key: cord-327273-7ntp7x8d authors: street, renée; malema, shirley; mahlangeni, nomfundo; mathee, angela title: covid-19 wastewater surveillance: an african perspective date: 2020-07-03 journal: sci total environ doi: 10.1016/j.scitotenv.2020.140719 sha: doc_id: 327273 cord_uid: 7ntp7x8d abstract the covid-19 pandemic has once again highlighted the importance of access to sufficient quantities of safe water and sanitation in public health. in the current covid-19 pandemic, an early warning wastewater system has been proposed as a platform for sars-cov-2 surveillance, and a potentially important public health strategy to combat the disease. this short communication on wastewater surveillance in sub-saharan africa highlights challenges, opportunities and alternatives taken into account the local context. the covid-19 pandemic has once again highlighted the importance of access to sufficient quantities of safe water, and sanitation in public health. well managed water, sanitation and hygiene (wash) are critical for protection of human health during disease outbreaks [1] . wastewater contains viruses, bacteria and parasites and inadequate treatment of, or exposure to, wastewater and fecal sludge plays a role in spreading disease [2, 3] . on the other hand, tracking of wastewater has historically played a key role in the development of early warning systems (ews) for various enteric viruses, including poliovirus, norovirus and hepatitis [4] [5] [6] . in 2011, kano state of nigeria was the first on the african continent to introduce environmental surveillance for poliovirus and many other regions in africa have since included wastewater surveillance to supplement polio eradication efforts [7] [8] [9] . to date, the screening of wastewater is recognized as an important tool for monitoring wild poliovirus and vaccine-derived polioviruses [7, 10] . in the current covid-19 pandemic, tracking of wastewater has been proposed as a platform for sars-cov-2 surveillance, and a potentially important public health strategy to combat the disease [11, 12] . diarrhea is a frequent presenting symptom in patients with covid-19, and sars-cov-2 rna has been detected in stool samples from both adults and children [13] [14] [15] [16] . thus sars-cov-2 surveillance through water-based epidemiology (wbe) is a potential complimentary and cost-effective approach to enable wide scale screening which would reduce labor intensive and costly personal covid-19 testing and tracings [11, 17, 18] . to date, the detection of sars-cov-2 rna has been demonstrated in the wastewater of a growing number of countries including australia, j o u r n a l p r e -p r o o f france, the netherlands and the united states of america [13, [19] [20] [21] [22] . notably most of this work has been carried out in high-income countries. like most epidemics, the rapid spread of covid-19 is likely to disproportionately affect the most disadvantaged and vulnerable communities [18, 23, 24] . currently covid-19 prevalence is influenced by regions supporting high frequency screening and testing, compared with poorly resourced regions where low prevalence may be linked to underreporting [18, 25] . therefore, wastewater surveillance systems may prove critical in many low-and middle-income countries where health systems infrastructure, testing systems, personal protective equipment (ppe) and human resource capacity are constrained [25, 26] . nonetheless, the proposed opportunities presented by wastewater surveillance need to be understood in the local context which will in turn give rise to locally relevant, evidence-informed solutions. a study of 100 households in a low-income urban settlement of nakuru, kenya revealed that all pit latrines were shared by more than one family, and the average number of people sharing a pit latrine was 23 individuals (ranging between 4 and 56) [37] . to date, no cases of transmission via the fecal-oral or waterborne routes have been reported for sars-cov-2, and it has been suggested that infection via this route is improbable during quarantine or while under self-isolation [21, 38] . however, this may not be the case for shared spaces and potential fecal-oral transmission might pose an increased risk in contained living premises such as hostels and similar places of overcrowding [21] . the sampling of non-sewered systems such as pit latrines has been proposed as a world bank, wash (water, sanitation & hygiene) and covid-19 guidelines for the safe use of wastewater in agriculture: revisiting who guidelines. water science and technology sanitation & hygiene) and covid-19. un environment. 2020 [cited access role of environmental poliovirus surveillance in global polio eradication and beyond the use of human sewage screening for community surveillance of hepatitis e virus in the uk assessment of enteroviruses from sewage water and clinical samples during eradication phase of polio in north india progress on the implementation of environmental surveillance in the african region environmental surveillance for poliovirus in polio high epidemiology of the silent polio outbreak in rahat, israel, based on modeling of environmental surveillance data computational analysis of sars-cov-2/covid-19 surveillance by wastewater-based epidemiology locally and globally: feasibility, economy, opportunities and challenges sars-cov-2 in wastewater: potential health risk, but also data source presence of sars-coronavirus-2 in sewage prolonged presence of sars-cov-2 viral rna in faecal samples. the lancet gastroenterology & hepatology time course quantitative detection of sars-cov-2 in parisian key: cord-308086-jycvupy4 authors: zambrano-monserrate, manuel a.; ruano, maría alejandra; sanchez-alcalde, luis title: indirect effects of covid-19 on the environment date: 2020-04-20 journal: sci total environ doi: 10.1016/j.scitotenv.2020.138813 sha: doc_id: 308086 cord_uid: jycvupy4 abstract this research aims to show the positive and negative indirect effects of covid-19 on the environment, particularly in the most affected countries such as china, usa, italy, and spain. our research shows that there is a significant association between contingency measures and improvement in air quality, clean beaches and environmental noise reduction. on the other hand, there are also negative secondary aspects such as the reduction in recycling and the increase in waste, further endangering the contamination of physical spaces (water and land), in addition to air. global economic activity is expected to return in the coming months in most countries (even if slowly), so decreasing ghg concentrations during a short period is not a sustainable way to clean up our environment. this outcome is mainly due to the social distancing policies adopted by the governments following the appearance of the pandemic. also, the use of vehicles decreased considerably. all this led to a dramatic reduction in the concentrations of nitrogen dioxide (no 2 ) and particulate matter that have a diameter of less than 2.5 micrometers (pm 2.5) in the main chinese cities (esa, 2020a; cams, 2020). in other parts of the world, such as europe, air pollution has dramatically reduced since governments ordered citizens to stay at home to contain the spread of the new coronavirus. main industries as well as other regular activities have ground to a halt. for instance, car use has reduced which caused ghgs to decrease. in china alone, all of these air quality improvements generated human health benefits that have outnumbered confirmed sars-cov2 deaths thus far (chen et al., 2020). beaches are one of the most important natural capital assets found in coastal areas or salinas (ecuador) now look cleaner and with crystal clear waters. environmental noise is defined as an unwanted sound that could be generated by anthropogenic activities (for instance, industrial or commercial activities), the transit of engine vehicles, and melodies at high volume. environmental noise is one of the main the imposition of quarantine measures by most governments has caused people to stay at home. with this, the use of private and public transportation has decreased significantly. also, commercial activities have stopped almost entirely. all these changes have caused the noise level to drop considerably in most cities in the world. the generation of organic and inorganic waste is indirectly accompanied by a wide also, the industry has seized the opportunity to repeal disposable bag bans, even though single-use plastic can still harbor viruses and bacteria (bir, 2020). china has asked wastewater treatment plants to strengthen their disinfection routines furthermore, the decrease in ghg emissions currently observed in some countries is only temporary. since once the pandemic ends, countries will most likely revive their economies, and ghg emissions will skyrocket again. on the other hand, the safe management of domestic waste could be critical during the covid-19 emergency. medical waste such as contaminated masks, gloves, used or expired medications, and other items can easily be mixed with domestic waste. j o u r n a l p r e -p r o o f however, they should be treated as hazardous waste and disposed of separately. furthermore, these type of waste must be collected by specialized municipal operators or waste management operators (un, 2020). along these same lines, the un environment program urged governments to treat waste management, including medical, domestic, and other waste, as an urgent and essential public service to minimize possible secondary health and environmental effects (arcplus, 2020). finally, it is concluded that covid-19 will produce both positive and negative indirect effects on the environment, but the latter will be greater. decreasing ghg concentrations during a short period is not a sustainable way to clean up our environment. furthermore, the virus crisis brings other environmental problems that may last longer and maybe more challenging to manage if countries neglect the impact of the epidemic on the environment. air pollution reduction and mortality benefit during the covid-19 outbreak in china global carbon project drinking water chlorination by-products and cancer waste paper recycling decision system based on material flow analysis and life cycle assessment: a case study of waste paper recycling from china recycle more, waste more? when recycling efforts increase resource consumption recycling, recovering and preventing "food waste": competing solutions for food systems sustainability in the united states and france pollution exposure on marine protected areas: a global assessment. marine pollution bulletin food waste matters-a systematic review of household food waste practices and their policy implications effect of hydrogen supplementation on engine performance and emissions psychological strategies to promote household recycling. a systematic review with meta-analysis of validated field interventions key: cord-331069-ioph6vsp authors: tobías, aurelio title: evaluation of the lockdowns for the sars-cov-2 epidemic in italy and spain after one month follow up date: 2020-07-10 journal: sci total environ doi: 10.1016/j.scitotenv.2020.138539 sha: doc_id: 331069 cord_uid: ioph6vsp from the end of february, the sars-cov-2 epidemic in spain has been following the footsteps of that in italy very closely. we have analyzed the trends of incident cases, deaths, and intensive care unit admissions (icu) in both countries before and after their respective national lockdowns using an interrupted time-series design. data was analyzed with quasi-poisson regression using an interaction model to estimate the change in trends. after the first lockdown, incidence trends were considerably reduced in both countries. however, although the slopes have been flattened for all outcomes, the trends kept rising. during the second lockdown, implementing more restrictive measures for mobility, it has been a change in the trend slopes for both countries in daily incident cases and icus. this improvement indicates that the efforts overtaken are being successful in flattening the epidemic curve, and reinforcing the belief that we must hold on. the first confirmed cases of sars-cov-2 in italy and spain were identified a week apart in late february 2020 (saglietto et al., 2020) . since then, italy has become the third most affected country worldwide (128,948 cases, in april 5th) after the united states and has the highest number of deaths due to the sars-cov-2 pandemic (15,887 deaths, in april 5th). meanwhile, spain is the second most affected in the number of diagnosed cases (130,759) and mortality (12,418) (our world in data, 2020). since march 8th, widespread lockdown measures have been in place in italy. specific measures restricting social contact were first introduced in the northern regions, where most cases had occurred, then extended to the whole country on march 10th. furthermore, science of the total environment j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / s c i t o t e n v italy tightened these measures extending the lockdown on march 21st: all businesses were closed, with the exception of those essential to the country's supply chains. similarly, spain imposed a lockdown on march 16th , with social distancing measures similar to those established in italy. two weeks later, on march 30th, spain also implemented a more restrictive lockdown, aimed at reducing the mobility and non-essential industrial activity countrywide (mitjà et al., 2020) . these restrictive measures have mainly been focused on flattening the epidemic curve. most of the results reported daily by governments, official agencies, and the media are aimed at describing cumulative epidemic data. conversely, little attention has been paid to describe, quantify, and compare the lockdown effects within and between countries from an epidemiological point of view using incident data. we collected data between february 24th and april 5th from the websites of the italian and spanish ministries of health (dipartamento della protezione civille, 2020; instituto de salud carlos iii, 2020). we have analyzed the trends of the daily incident diagnosed cases, deaths, and intensive care units (icu) admissions for sars-cov-2 in italy and spain before and during their respective national lockdowns, using an interrupted time-series design (bernal et al., 2017) . the data was analyzed with quasi-poisson regression, using an interaction model to estimate the change in trends (bernal et al., 2017) . the data was analyzed using stata, release 16 (statacorp, college station, tx, 2019). fig . 1 shows the observed daily incident data and the estimated trend slopes for italy and spain since february 24th. before the lockdown, the daily percent increase of all the incidence outcomes was higher in spain (38.5% for diagnosed cases, 59.3% for deaths, and 26.5% for icu admissions) than in italy (21.6%, 32.8%, and 16.7%, respectively) ( table 1) . during the first lockdown period, both countries show similar daily trends (12.5%, 13.7%, and 3.7% in italy; and 11.9%, 17.6%, and 9.6% in spain). thus, during the first lockdown the daily increase in incident data was considerably reduced. in italy, the diagnosed cases decreased by 42.1%, deaths by 58.2%, and icu admissions by 77.8%. this reduction was even higher in spain, where the diagnosed cases decreased by 69.1%, deaths by 77.8%, and icu admissions by 66.8%. however, although the slopes have been flattened for all outcomes, the trends kept rising (fig. 1) . during the second and more restrictive lockdown, currently ongoing, both countries show some positive signs, indicating that trends may be changing (fig. 1) . specifically, in italy all outcomes start declining; diagnosed cases if −2.0%, daily deaths of −0.2%, and icu admissions of −16.8%. similarly, spain also shows decline trends in daily diagnosed cases of −2.7%, deaths of −1.8%, and icu of −5.6%. lockdown, including restricted social contact and keeping open only those businesses essential to the country's supply chains, has had a beneficial effect in both countries. the trend slopes were considerably reduced for all the outcomes. however, this was not enough to change the rising trend of the epidemic. for this reason, more restrictive actions were suggested. the second lockdown, still ongoing, shows how the trends have changed, with a reduction of daily incident cases, deaths, and more significantly in icus. these are of similar magnitude in both countries, although italy carries a week ahead of spain. however, mortality still shows a small increase, probably because it follows incidence trends with a delay of 1-2 weeks. we should acknowledge that this figures could change during forthcoming weeks. analysis of trends using daily incident data may be a useful complement to more conventional approaches used to monitor the sars-cov-2 epidemic by testing and reporting changes overtime after a public health intervention (i.e., lockdown, confinement or quarantine). interrupted time-series regression models are relatively easy to implement using readily available data by health authorities (bernal et al., 2017) . this is a descriptive analysis without predictive purposes. for an easy interpretation, and comparison of the effectiveness of lockdown measures between countries, a linear trend is assumed before and during the lockdown periods. the changes in the definition of diagnosed cases have not been taken into account, nor has the reduction in the susceptible population because of the lockdown. therefore, the incident cases are modeled directly instead of the incidence rate, assuming that the entire population is at risk. timely indications for public health authorities and governments are essential to slow down the sars-cov-2 epidemic and relieve the pressure on overburdened health services. although available data is still limited, and findings must be interpreted with caution, we believe that real-time detection of pattern changes are essential to evaluate the current measures of control and design future ones. in this sense, the positive signs already shown by the decreasing trend slopes after a more restrictive lockdown in italy and spain could indicate an optimistic and encouraging forecast for those countries that in late march also announced restrictive lockdown measures for flattening the sars-cov-2 epidemic curve (e.g., the united kingdom on march 23th or ireland on march 27th). these results show that the sacrifices that our society is making are gaining us valuable time, which is essential to get ready to face the future pressures that this epidemic will bring forth. the authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. interrupted time series regression for the evaluation of public health interventions: a tutorial situación de covid-19 en españa experts' request to the spanish government: move spain towards complete lockdown covid-19) -statistics and research. oxford martin school, the university of oxford, global change data lab covid-19 in europe: the italian lesson to milena maule (department of medical sciences, university of turin) for her useful comments helping to improve the contents of the manuscript. .6 (4.7, 14.7) −5.6 (−24.4, 6.9) key: cord-305558-dnvl60ez authors: ranjan, avinash kumar; patra, a. k.; gorai, a. k. title: effect of lockdown due to sars covid-19 on aerosol optical depth (aod) over urban and mining regions in india date: 2020-07-19 journal: sci total environ doi: 10.1016/j.scitotenv.2020.141024 sha: doc_id: 305558 cord_uid: dnvl60ez abstract the severe acute respiratory syndrome-coronavirus diseases 2019 (sars-covid-19) pandemic has posed a serious threat to human health (death) and substantial economic losses across the globe. it was however presumed that extreme preventive measures of entire lockdown in india might have reduced the air pollution level and therefore decreased the aerosol optical depth (aod). the moderate resolution imaging spectroradiometer (modis)-based multi-angle implementation of atmospheric correction (maiac) daily aod product was deployed to investigate the change in aod level during lockdown phases across the indian territory as compared to the long-term mean aod level (2000–2019) of the same periods. the key findings of the study revealed that aod level over the indian territory is greatly reduced (~45%) during the lockdown periods as compared to the long-term mean aod level (2000–2019). furthermore, a noteworthy negative aod anomaly (~6 to 37%) was observed across the four metropolitan cities in india during the entire lockdown period (25th march to 15th may 2020). however, coal mining regions of the various coalfields in india showed a positive anomaly (~+11 to 40%) during the lockdown periods due to ongoing mining operations. in a nutshell, the study results indicated a huge drop in the aod level over indian territory during lockdown periods. it is expected that the pandemic can influence some policy decisions to propose air pollution control methods. lockdown events possibly may play a crucial role as a potential solution for air pollution abatement in the future. it may not be uncommon in future when the governments may implement deliberately selective lockdowns at pollution hotspots to control the pollution level. (https://www.who.int/emergencies/diseases/en/). the first covid-19 case was found in the wuhan region of central hubei province of china on 31 st december 2019 (shi et al., 2020) . it has rapidly been spreading since then across the globe (li et al., 2020a) countless studies have already unveiled the importance of aerosol research, and also demonstrated the direct and indirect contributions of aerosols on the climate change at regional to global scales (qian and giorgi, 1999; menon et al., 2002; huang et al., 2014) . the aerosol optical depth (aod) affects the atmospheric stability and precipitation as aerosols disturb the scattering and absorption of solar radiation (jiang et al., 2016; shaw and gorai, 2018) , the hydrological cycle (prasad et al., 2004) , and vegetation cover and its growth (lal et al., 2019; sarkar and kafatos, 2004) . apart from climatic effects, aerosol causes many serious healthrelated issues (i.e., asthma, premature death, lung cancer, cardiopulmonary mortality, and pulmonary inflammation) (prasad et al., 2005; huang et al. 2012; mulenga and siziya, 2019) . furthermore, numerous past studies have shown that aod can be used as a metric to estimate air pollution level, whereas aod is typically used as a proxy of pm 2.5 and pm 10 concentration estimation (kumar et al., 2007; lin et al., 2015) . thus, study on aod during lockdown periods can help in understanding the influence anthropogenic activities on the tropospheric aerosol level. an approximate concentration of particulate matter can also be anticipated. the current j o u r n a l p r e -p r o o f study therefore investigated the impacts of covid-19 imposed lockdown events on aod level over the indian territory. the overarching objectives of this investigation are (1) to analyze the effect of lockdown due to covid-19 on the aod level over the indian territory with special emphasize on four metropolitan cities and 10 mining regions in india, and (2) to estimate the aod anomaly during the lockdown periods (2020) as compared to the long-term (2000 -2019) mean aod during the same periods. retrieval and processing of long-term daily aod data using google earth engine (gee) cloud platform is the crucial aspect of the present study. this is the maiden study where long-term (2000 -2020) daily aod were retrieved for the entire indian territory with special emphasize on four metropolitan cities and 10 coal mining locations during the lockdown periods. this paper is structured as follows: section 1 is the introduction section, where emergence of covid-19 pandemic, status of affected countries from covid-19 pandemic, status of covid-19 cases in india, literature review on positive impacts of covid-19 enforced lockdown on environment, importance of aod study, motivation and objectives of the present investigation have been summarized. section 2 describes the materials and method that include details of satellite data, details of the study regions, phase-wise data processing, and the data analysis sequence. the key findings of the study, like, phase-wise aod concentration over the indian territory (including four metropolitan cities and 10 coal mine locations), aod anomaly as compared to last 20 year mean aod for the same periods, comparison with earlier studies have j o u r n a l p r e -p r o o f the aod product of moderate resolution imaging spectroradiometer (modis) satellite sensor (mcd19a2-v6) is used in the present study to retrieve the daily basis aod over the indian territory. mcd19a2 is a modis terra and aqua combined multi-angle implementation of atmospheric correction (maiac) land aerosol optical depth (aod) level-2 gridded product having a spatial resolution of 1 km. mcd19a2 offers daily-basis aod for land at two different wavelength bands, i.e., 470 nm (blue band) and 550 nm (green band). aod at 550 nm (green band) was used in the present study due to its better consistency . the mcd19a2 product was typically available in sinusoidal grid projection, which was rethereafter, phase-wise mean aod datasets were exported, and further processing, map preparation, assessment, etc. were completed in arcgis (v10.5) software. the present study is focused to analyze the impact of phase-wise nationalwide lockdown on the spatio-temporal pattern of aod level over the indian territory as compared to last 20 years mean aod level. furthermore, attention is paid to investigate the variation in aod level within furthermore, phase-wise anomaly maps are derived using eq. 1 to portray the percent changes in aod level at a particular spatial location during lockdown period as compared to the long-term mean (2000 -2019) aod for the same time-periods. the self-explanatory flowchart for the methodological workflow is given in fig 2, wherein the sequence of data acquisition, preprocessing, aod extraction, phase-wise aod estimation, and aod anomaly assessment are presented. where, is the phase-wise mean aod for the year 2020; and ̅ is the phase-wise long-term (2000 -2019) mean aod. the phase-wise aod distribution map of indian territory is prepared and presented in period. additionally, the aod data of few pixels in those areas are missing for some years and hence the mean aod level may be lesser than the actual level. ultimately, it can be concluded that the entire national lockdown has led to the huge decline in aod value across the indian state, suggesting corresponding reduction in air pollution (especially pm 2.5 and pm 10 ) level over the indian territory. phase-wise aod anomaly was estimated using eq. 1 and map was prepared to understand the spatial variation in aod during the lockdown period in india as compared to the long-term mean aod (2000 aod ( -2019 . the prepared aod anomaly map is presented in fig 4, wherein negative range (green -yellow) shows the decrement and positive range (light bluedark blue) shows the increment in the aod during different phases of the lockdown as compared to the long-term mean aod during the same periods. the prepared aod anomaly map shows a significant reduction in aod during lockdown period as compared to long-term mean aod. during phase 1, a significant reduction in the aod as compared to the long-term mean aod were observed in most of the states, except a few patches in mh, some portion of rj, mp, cg, od, ts, and ap states that reported higher aod value (fig 4(a) ). during phase 2, almost all states had negative aod anomaly percent; only a few small unevenly distributed patches of positive aod anomaly percent were detected across j o u r n a l p r e -p r o o f the north-east to south-eastern states of india (fig 4(b) ). however, slightly higher positive aod anomaly patches were observed during phase 3. almost every state was detected with few small spatial patches of positives aod anomaly; particularly, rj, up, br, all north-east states, jh, wb, mh, ts, ap, and ka were found with relatively higher positive anomaly patches (fig 4(c) ). furthermore, aod anomaly map over the entire lockdown period (25 th march to 15 th may, 2020) is shown in fig 4(d) . the map indicated that during the lockdown period, the aod reduced drastically across the indian territory (as aod anomaly percent was found negative across most of the area). nevertheless, few spatial patches were observed across mp, mh, ts, ap, od, wb, and as states where the positive anomaly was detected. the quantitative analysis of aod anomaly (state-wise mean aod anomaly is presented in one is the maiden study which reports a significant reduction in the aod level over the indian territory along with four metropolitan cities and 10 coal mine locations during lockdown periods as compared to same periods of last 20 year mean aod level. overall, these studies revealed that covid-19 pandemic enforced lockdown events resulted in significant improvement of the air quality in highly polluted indian cities. phase-wise aod anomaly ( however, unusually high positive anomaly over the few mine locations can be due to the spatiotemporal variation in areal coverage of coal mine locations along with the amount of coal extraction. one more possibility is that some of the mines were not functional since 2000 and coal production from these mines started after 2010, which resulted in very less aod during that time period as compared to recent years. moreover, inconsistency in the total number of aod pixels within the 3 km buffer zone of the coal mine location cannot be overlooked. this may be the one of the possible reasons for slightly higher positive aod anomaly, as we have discussed in section 3.2 and 3.3. no such study was available to compare the aod level over the mine locations. in a nutshell, our investigation reports a huge reduction in aod level across the indian early transmission dynamics in wuhan, china, of novel coronavirus-infected pneumonia using satellite remote sensing data to estimate the high-resolution distribution of ground-level pm 2.5 . remote sensing of environment research report on companies' survival and development strategy during a novel coronavirus epidemic mcd19a2 modis/terra+aqua land aerosol optical depth daily l2g global 1km sin grid v006. distributed by nasa eosdis land processes daac modis multi-angle implementation of atmospheric correction (maiac) data user's guide, collection 6 (ver effect of lockdown amid covid-19 pandemic on air quality of the megacity delhi application of support vector machine and gene expression programming on tropospheric ozone prognosticating for tehran metropolitan climate effects of black carbon aerosols in china and india characterizing of air pollution in tehran: comparison of two air quality indices covid-19 pandemic and environmental pollution: a blessing in disguise? science of the total environment indoor air pollution related respiratory ill health covid-19 pandemic: impacts on the air quality during the partial lockdown in são paulo state, brazil. science of the total environment impact of covid-19 lockdown on pm10, so2 and no2 concentrations in salé city (morocco) seasonal variability of aerosol optical depth over indian subcontinent. international workshop on the analysis of multi-temporal remote sensing images interactive coupling of regional climate and sulfate aerosol models over eastern asia interannual variability of vegetation over the indian subcontinent and its relation to the different meteorological parameters. remote sensing of environment study of aerosol optical depth using satellite data (modis aqua) over indian territory and its relation to particulate matter concentration effect of restricted emissions during covid-19 on air quality in india radiological findings from 81 patients with covid-19 pneumonia in wuhan, china: a descriptive study. the lancet infectious diseases the impact key: cord-318043-1x3dp1vv authors: ahmadi, mohsen; sharifi, abbas; dorosti, shadi; ghoushchi, saeid jafarzadeh; ghanbari, negar title: investigation of effective climatology parameters on covid-19 outbreak in iran date: 2020-04-17 journal: sci total environ doi: 10.1016/j.scitotenv.2020.138705 sha: doc_id: 318043 cord_uid: 1x3dp1vv abstract sars cov-2 (covid-19) coronavirus cases are confirmed throughout the world and millions of people are being put into quarantine. a better understanding of the effective parameters in infection spreading can bring about a logical measurement toward covid-19. the effect of climatic factors on spreading of covid-19 can play an important role in the new coronavirus outbreak. in this study, the main parameters, including the number of infected people with covid-19, population density, intra-provincial movement, and infection days to end of the study period, average temperature, average precipitation, humidity, wind speed, and average solar radiation investigated to understand how can these parameters effects on covid-19 spreading in iran? the partial correlation coefficient (pcc) and sobol’-jansen methods are used for analyzing the effect and correlation of variables with the covid-19 spreading rate. the result of sensitivity analysis shows that the population density, intra-provincial movement have a direct relationship with the infection outbreak. conversely, areas with low values of wind speed, humidity, and solar radiation exposure to a high rate of infection that support the virus's survival. the provinces such as tehran, mazandaran, alborz, gilan, and qom are more susceptible to infection because of high population density, intra-provincial movements and high humidity rate in comparison with southern provinces. since late december 2019, patients presenting with viral pneumonia due to an unidentified microbial agent were reported in wuhan, china. it was an outbreak of the novel coronavirus disease named 2019 novel coronavirus (covid-19; previously known as 2019-ncov). the disease has rapidly spread from wuhan to other areas and affected 196 countries worldwide by march 25, 2020, which raised intense attention internationally (chen et al., 2020; lu et al., 2020; phan et al., 2020; xu et al., 2020) . it is really important to find out all the factors that play a role in covid-19 spreading in urban. the transmission of viruses can be affected by many factors, including climate conditions (such as temperature and humidity), population density and medical care quality (wang et al., 2020) . therefore, understanding the relationship between the geographical features of a country and the transmission of covid-19 is key to making the best decision to control and prevent the pandemic. in other words, the discipline of geography is playing in the fight against the virus sars-cov-2, which causes coronavirus disease . therefore, urban geography can be very helpful in that the spatial organization of the city determines the spatial pattern of the spread of the disease (boulos and geraghty, 2020; wang et al., 2020) . while a set of health experts are banking on warmer weather conditions to slow down, if not completely halt, the coronavirus, it is yet not clear whether the coming months will bring any respite to the world. based on recent research, which has yet to be peer-reviewed, indicated that two factors include high temperature and humidity, directly correlated with the spreading of covid-19 in a region (wang et al., 2020) . (araujo and naimi, 2020) . however, the spreading of covid-19 virus in hot and humid conditions will not stop entirely. malaysia has confirmed more than 1,500 cases of the virus; more than 500 people are infected in indonesia; and in singapore, where the average temperature is around j o u r n a l p r e -p r o o f year-round, despite rigorous detection methods and strict quarantine rules. the results of the research show that longer-term dramatic change of solar flux of ionizing radiation leads to provide an opportunity to create nono-metrical viruses like sars and mers (qu and wickramasinghe, 2017) . also, high solar radiation prevents an outbreak with inactivating (or semi-infectious) coronaviruses (gupta et al., 2015; qu and wickramasinghe, 2017) . based on the results of (qu and wickramasinghe, 2017) identified. finally, the discussion and conclusion presented. the main variables in this study include geographical indicators with averaged data from february 19 to march 22 from weather spark online web service ("the typical weather anywhere on earth -weather spark," n.d.). variables including the number of infected people with covid-19 reported by ("who | world health organization," n.d.), population density, intra-provincial movement, infection days to end of the study period, average temperature( • c) (yuan et al., 2006) , average precipitation (mm) (araujo and naimi, 2020) , humidity(%) (wang et al., 2020) , wind speed (km/h) (yuan et al., 2006) and average solar radiation (kwh/m 2 ) (qu and wickramasinghe, 2017) in the study period. the infection rate as a dependent variable defined as eq. (1). this variable indicates the rate of infection or speed of the covid-19 spreading. table 1 shows the descriptive statistical and meteorological data of iran from february 19 to march 22. (2) where p is average annual precipitation (mm), t is the average annual temperature ( • c) and i is de martonne aridity coefficient. in this equation, the evaporation is indirectly considered. this method is more widely used in iran for two reasons. the first availability of the factors and second the classification of this method can define diverse climates (zareiee, 2014) . the de martonne classification is shown in table 2. iran can be divided into at least four different climate zones. different clustering current climate regions in iran shown in fig. 1a . more than half of iran's area is arid and consists of lands with high average temperature shown in orange color. however, the semi-arid area includes high mountain and agricultural lands. this area is gray in fig. 1a . also, three provinces of iran have the mediterranean, wet and very wetlands consisting of jangles and grasslands. the outbreak of covid-19 based on the first case of observation is shown in the geographical map ( fig.1b ). the first case of covid-19 infection occurred in qom and then spread to all provinces over the 13days period. regarding the figure, qom and tehran can be described as the center of outbreaks that have spread throughout the south and north. in some provinces, this outbreak has occurred earlier, which has been spectacularly significant in terms of intra-provincial movement. in some provinces, this outbreak has occurred after 13 days, which can be attributed to a lack of awareness of the people. in order to get a better understanding of the covid-19 outbreak in the iranian provinces and the study of geographical factors, the meteorological data recorded in the study period are referred. the results of pearson correlation analysis between the variables are shown in table 3 . in this study, the infection rate was defined as the independent variable and its correlation with geographical variables analyzed. do these results show whether the rate of disease outbreaks in the provinces depends on geographical factors or not? using these results, we can infer the meteorological impact scenario on the outbreak of covid-19. according to table 3 in this part of the research, sensitivity analysis between variables is discussed. therefore, we use two methods of partial correlation coefficient (pcc) and sobol'-jansen method to examine the importance of variables and prioritize it. in the pcc method, a linear regression must be made between the independent variables of the problem and the infection rate. on this basis, the basic geographical data should first be standardized. linear regression is created after changing data range between -1 and 1. table 4 ). we are not satisfied with linear regression, to investigate these variables more consistently, we will continue to use one of the most powerful methods for identifying in this paper, we used the multi-layer perceptron (mlp) technique with 10 hidden neurons to create a more accurate model. we used 70% of the data for training, 15% testing, and 15% model validation, to obtain the best model with the highest accuracy (r = 92%). the results were recorded as shown in fig. 2 . by applying the mlp model on sobol'-jansen method, results are depicted in fig.3 d. figure figure 3 shows the contour infection rate of covid-19 disease concerning geographic variables (population density and movement). the higher value of the population density and intra-provincial movement leads to a higher value of infection rate so that in high-density provinces, the rate of disease growth reaches 150 people per day. figure 3 b also shows the bubble plot of the average temperature and relative humidity over the study period. the size of bubbles also indicates the rate of infection, and the bubbles have different colors for different climates from iran. results show that in arid and semi-arid regions, disease rates are higher in areas with low humidity than in areas with high humidity. however, two wetlands of mazandaran and gilan are places with a high rate of infection. because these provinces are areas with very high population density. with the classification of the area to different climates, the average rate of disease spread in wetlands is higher than in other areas of iran (fig. 3 c) . figure 4 illustrates the governing variables involved in the change of coronavirus covid-19 spreading rate. the maps are depicted and colored based on data quartiles. figure 4 i shows the covid-19 infection rate over the study period. observations show that the infection rate in the provinces of central iran is higher than in the border regions, and these provinces are both high in population density and movement. a comparison of the virus infection rate charts and meteorological maps can justify the results obtained in the aforementioned methods. according to fig. 4 f, it can be seen that the humid area includes north, west, and northwest of iran. however, the main part of the outbreak is in humid, very humid, and semi-arid (or mountainous) areas. the wind direction in most parts of iran is from the west and in the northeast to west. wind speeds are low in most parts of the country. based on fig. 4 h solar radiation in central iran is lower than southeast with a low infection rate. we can conclude that where the infection rate is high, the population density and movement are high. also, in this area humidity, wind speed and solar radiation have a reverse relationship with the rate of the disease spreading. the the in that the spatial organization of the city determines the spatial pattern of the spread of the disease. iran is one of the countries with different types of climate. the infection rate in provinces is different; therefore, understanding the main variables that play an important role in this various spreading rate is crucial. in this study, the correlation of nine main variables includes the number of infected people, population density, intra-provincial movement, days of infection, average temperature, average rain, humidity, wind speed, and solar radiation with infection rate analyzed. the sensitivity analysis between variables determined by two methods partial correlation coefficient (pcc) and sobol'-jansen to examine the importance of variables and prioritize it. based on the pcc method, the population density, intra-provincial movement, day of infection have a direct relation with infection outbreak. conversely, wind speed, humidity, and solar radiation have an indirect correlation with the infection rate. however, in two humid regions of iran, the rate of virus spreading is high. the sobol'-jansen method also approved the aforementioned results and confirmed that the main variables that play an important role in the covid-19 outbreak are population density, intra-provincial movement, wind spread of sars-cov-2 coronavirus likely to be constrained by climate. medrxiv geographical tracking and mapping of coronavirus disease covid-19/severe acute respiratory syndrome coronavirus 2 (sars-cov-2) epidemic and associated events around the world: how 21st century gis technologies are supporting the global fight against outbr the effects of temperature and relative humidity on the viability of the sars coronavirus epidemiological and clinical characteristics of 99 cases of 2019 novel coronavirus pneumonia in wuhan, china: a descriptive study application of gene expression programming and sensitivity analyses in analyzing effective parameters in gastric cancer tumor size and location do sunspot numbers cause global temperatures? evidence from a frequency domain causality test genomic characterisation and epidemiology of 2019 novel coronavirus: implications for virus origins and receptor binding importation and human-to-human transmission of a novel coronavirus in vietnam sars, mers and the sunspot cycle variance based sensitivity analysis of model output. design and estimator for the total sensitivity index the typical weather anywhere on earth -weather spark high temperature and high humidity reduce the transmission of covid-19 who | world health organization pathological findings of covid-19 associated with acute respiratory distress syndrome a climatologic investigation of the sars-cov outbreak in beijing, china. am evaluation of changes in different climates of iran, using de martonne index and mann key: cord-321240-f6qh4fva authors: adekunle, ibrahim ayoade; onanuga, abayomi toyin; akinola, olanrewaju olugbenga; ogunbanjo, olakitan wahab title: modelling spatial variations of coronavirus disease (covid-19) in africa date: 2020-08-10 journal: sci total environ doi: 10.1016/j.scitotenv.2020.138998 sha: doc_id: 321240 cord_uid: f6qh4fva clinical and epidemiological evidence has been advanced for human-to-human transmission of the novel coronavirus rampaging the world since late 2019. outliers in the human-to-human transmission are yet to be explored. in this study, we examined the spatial density and leaned statistical credence to the global debate. we constructed spatial variations of clusters that examined the nexus between covid-19 attributable deaths and confirmed cases. we rely on publicly available data on confirmed cases and death across africa to unravel the unobserved factors, that could be responsible for the spread of covid-19. we relied on the dynamic system generalised method of moment estimation procedure and found a ~0.045 covid19 deaths as a result of confirmed cases in africa. we accounted for cross-sectional dependence and found a basis for the strict orthogonal relationship. policy measures were discussed. clinical and epidemiological evidence has been advanced for human-to-human transmission of the novel coronavirus rampaging the world since late 2019 (see kamph, 2020; shereen et al., 2020; yeo et al., 2020 for an extensive review). the contemporary disease is spreading exponentially around the world, and the pandemic has science of the total environment j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / s c i t o t e n v been felt in at least 185 countries reporting 1,844,863 confirmed cases with 117,021 deaths as at 14th april 2020 (who, 2020a (who, , 2020b . in this time of the global pandemic, fifty-two (52) african countries have reported one or more confirmed cases of covid 19 with only comoros and lesotho presently with no single confirmed case. as a result of changing medical data, africa at the time of writing has recorded 10,787 confirmed cases, with 501 deaths. algeria is the most hardly hit nation with 1983 confirmed cases and 313 deaths, although lesser confirmed cases compared to south africa (2272) with 27 deaths (who, 2020a (who, , 2020b . in other regions of the world, the united states of america (usa) with 553, 822 confirmed cases and 21,972 deaths remain the hardest-hit nation in america (north and south) and around the world. china, with 83,696 confirmed cases and 3351 deaths, is the hardest hit asian country. in europe, italy, with 159,516 confirmed cases and 20,465 deaths although relatively less compared to confirmed cases in spain with 169,496 with 17,489 deaths remains the hardest hit because of their superior coronavirus reported death cases. in the middle east region, iran, with 73,303 confirmed cases and 4585 deaths is the worst-hit nation. in ascertaining the structures, features, risk factors and severity of the novel coronavirus, clinical and epidemiological evidence has been leaned to human-to-human transmissions (community transmission). however, outliers in the human-to-human transmission could be as a result of clusters that are yet to be explored. by advancing arguments for clusters of the novel coronavirus in africa, we provided a social dimension to abating the spread of coronavirus diseases. africa is predominantly famous for overcrowding their megacities like pretoria, lagos, johannesburg, cairo and nairobi. clustering by people either in public gatherings or residential facilities makes them endangered species. even if social distancing is enforced in the public domain to prevent human-to-human transmission, it may be difficult if not impossible to enforce in an already overcrowded shared resident. by advancing arguments for inevitable human clustering at various residential or sub-groups in africa, the study provides an econometric analysis of the social dimensions of the spread of coronavirus diseases in africa. apparently, this study leads the debate on spatial density and statistical credence of how confirmed cases is statistically related to attributable deaths from coronavirus diseases in africa. we build upon the work of sarkodie and owusu (2020) to examine the phenomenological influence of outliers in the human-human transmission in africa. the intricacies of these unobserved factors in abating human-to-human transmission of coronavirus disease in africa underpin this study. we rely on publicly available data for africa countries confirmed and death cases. we use a novel estimation method capable of accounting for crosssectional dependence. we found a basis for the strict orthogonal relationship among the variable and accounted for unobserved heterogeneity of the human-to-human transmission. we rely on data obtained from the world health organisation (who) situation reports 55 1 through to situation reports 85 2 (a time plot of 31-time invariant observations). we transformed the daily observations in conformity with conventional panel data estimation procedure (wide to long) as in sarkodie and owusu (2020) . we relied on health indicators (number of covid-19 attributable deaths and number of confirmed cases) across 52 africa states. 3 in fig. i , we presented the spatial density of the number of confirmed cases and the number of deaths from covid 19 across african states. our empirical strategy in gauging the statistical relationship between the number of attributable covid-19 deaths and confirmed cases was to estimate a series of baseline fixed effect estimator by assuming that all explanatory variables are strictly exogenous. we proceed to estimate the dynamic panel data system generalised method of moment (gmm) (arellano and bover, 1995) and impose (and test) the common factor restrictions to account for the potential endogeneity of the number of covid-19 attributable deaths and number of confirmed cases across 52 africa states. the functional relationship is expressed as: where coviddeaths i, t is the total number of attributable covid-19 deaths in country i over period t; confrmd cases i, t represent the number of confirmed cases in country i over period t, t defines the time parameters, and i give the cross-sectional domain of the covid-19 attributable deaths model. we begin by imposing the assumption of strict exogeneity on the regressors, leading to violations and inconsistency in our fixed-effect model. we proceed to obtain asymptotically consistent parameter estimates in a single equation dynamic gmm estimators by using a common factor representation (blundell and bond, 1998) . our dynamic panel covid-19 attributable deaths model is specified as: all other variables remain as earlier defined except ρ, which gives the constant parameter. ω and θ are the output elasticities. with an attendant, country-specific fixed effect idiosyncratic errors (outliers) predicted upon the model in eq. (3); we adjusted for violation of strict orthogonal assumptions by introducing the change parameter and by taking the semi-derivatives of the variables to account for variances in units and measurements to specify eq. (4) ε i, t contains e i (the country-specific fixed effect that is timeinvariant) while μ it is assumed to be independent and normally distributed with zero (0) mean and constant variance σ μ 2 both over time and across cross-sections, i.e., u it ≈ n(0, σ μ 2 ). we also accounted for strict orthogonal violations that could be due to first differenced estimation of ordinary least squares since the transformed error term δμ it still correlates with coviddeaths i, t−1 (a condition exacerbated when both contains μ it−1 ). the possibility of the e (coviddeaths i, t−1 δμ it ) = 0 ∀ h ≥ 2, t = 3, ……t justify the introduction of lagged variables as instruments in the strict orthogonal assumption relationship (anderson and hsiao, 1982; blundell and bond, 2000) . we estimated the dynamic system generalised method of moment (gmm) model for some reasons. the real-time reporting informed the observations of coronavirus disease in africa. we established a linear relationship between the variables of interest which informs our construct along such tangent. the number of cross-sections (countries) is higher than the numbers of time series (time plot of 31-time invariant reports) chosen. we estimated an unbalanced panel data model (predicted on non-occurrences of cases in some situation reports in some african countries). system gmm, renowned for glowing outcomes with persistent data under trifling assumptions (arellano and bover, 1995; blundell and bond, 1998) , was used to estimate the model of attributable covid-19 deaths as induced by confirmed cases. the result of the robust twostep estimates of the dynamic system generalised method of moment (gmm) is presented in table i . following pesaran (2004) , we estimated cross-sectional dependence. we rejected the null of no-cross-sectional dependence at a 5% level of significance. we also rejected the null of slope homogeneity at a 5% level of significance using the delta tilde and adjusted delta tilde estimates. we estimated the system gmm to account for cross-sectional dependence among heterogeneous observations. the one-period lag value of attributable covid-19 deaths is positive and statistically significant at 1%, implying its percentage increase will result in 0.0123 percentage increase in covid-19 attributable deaths. the intuition point to the relatively less covid-19 attributable deaths as induced by previously confirmed cases. although the lagged factors control for simultaneity bias, we cannot completely rule out the devastating influence of historical information leading to covid-19 deaths. types of shared residents, proximity to health care facilities, choice of healthcare utilisation in the time of illness and most importantly during this global pandemic, existing health conditions, as well as the devastating influence of covid-19 attributable deaths to friends and family in terms of depression, frontline health workers who are saddled with the care and post-death management of patients, are magnanimous in this global pandemic era. in other climes, the number of confirmed cases is positive and statistically significant at 5%, implying 0.0453 percentage increase in covid-19 attributable deaths in africa. by way of intuition, a proportionate rise in confirmed cases is attributable to potential deaths by~0.045. principally, the cluster of residents and sub-group around regions with high confirmed cases should be dispersed to reduce the wave at which the virus transmits from human to human. in table ii , we validated the instrumental variable choice in the covid-19 attributable deaths in africa. dynamic panel data estimates are known to suffer from problems of unobserved heterogeneity, dynamic endogeneity and simultaneity bias (baltagi et al., 2015) . system gmm, known explicitly for heteroscedasticity and non-normality assumptions unlike the least squares estimates, assumes linearity and uncorrelated error terms. our first-order and second-order difference results in favour of the rejection of the null hypothesis in the firstorder serial correlation examination and acceptance of the null hypothesis for the second-order serial correlation test. blundell and bond (2000) argued that the system gmm estimators requires the presence of first-order serial correlation and not the second-order serial correlation in the residual term. the result of table ii confirms that we obtained appropriate diagnostics. z = − 2.42; p b 0.05 at 5% level of significance in the first order serial coreelation analysis and then no second order serial correlation based on calculated z that is not statistically significant at 5% (z = − 0.96;p n 0.05). the hansen (1982) j-statistics test result confirmed the model has valid instruments since we fail to reject the null of overidentifying restriction at a 5% level of significance (p n 0.05;i. e p = 0.532). the f-statistics value 122.42 indicates the model is jointly significant at 5% level of significance. this study examined the spatial density of the novel coronavirus disease (covid-19) across 52 african states and leaned empirical credence to the relationship between confirmed cases and attributable deaths. we presented spatial and statistical evidence based on the situation reports from the world health organisation (who). we advise the public on the cautious interpretations of our statistical model, which rely on phenomenological models as in most social sciences research and not a clinical procedure that has a confidence interval of 99%. we found algeria to be the most hardly hit african nation (at the time of writing) by the rampaging virus (estimated in terms of the number of deaths recorded), and also we establish a linear relationship between the number of confirmed cases and the number of attributable deaths. our findings corroborate the finding of sarkodie and owusu (2020) in one of their strings of findings. the study is limited to facts obtainable at the present time of this global pandemic. note: * p b 0.01, * * p b 0.05 respectively formulation and estimation of dynamic models using panel data another look at the instrumental variable estimation of error-components models dynamic panel data models. the oxford handbook of panel data initial conditions and moment restrictions in dynamic panel data models gmm estimation with persistent panel data: an application to production functions large sample properties of generalized method of moments estimators potential role of inanimate surfaces for the spread of coronaviruses and their inactivation with disinfectant agents general diagnostic tests for cross-section dependence in panels. cambridge working papers in economics investigating the cases of novel coronavirus disease (covid-19) in china using dynamic statistical techniques covid-19 infection: origin, transmission, and characteristics of human coronaviruses covid-19) situation report-55. world health organization available at covid-19) situation report-85. world health organization available at enteric involvement of coronaviruses: is faecal-oral transmission of sars-cov-2 possible? the authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. key: cord-275424-u4doukk7 authors: ogen, yaron title: assessing nitrogen dioxide (no(2)) levels as a contributing factor to coronavirus (covid-19) fatality date: 2020-07-15 journal: sci total environ doi: 10.1016/j.scitotenv.2020.138605 sha: doc_id: 275424 cord_uid: u4doukk7 nitrogen dioxide (no(2)) is an ambient trace-gas result of both natural and anthropogenic processes. long-term exposure to no(2) may cause a wide spectrum of severe health problems such as hypertension, diabetes, heart and cardiovascular diseases and even death. the objective of this study is to examine the relationship between long-term exposure to no(2) and coronavirus fatality. the sentinel-5p is used for mapping the tropospheric no(2) distribution and the ncep/ncar reanalysis for evaluating the atmospheric capability to disperse the pollution. the spatial analysis has been conducted on a regional scale and combined with the number of death cases taken from 66 administrative regions in italy, spain, france and germany. results show that out of the 4443 fatality cases, 3487 (78%) were in five regions located in north italy and central spain. additionally, the same five regions show the highest no(2) concentrations combined with downwards airflow which prevent an efficient dispersion of air pollution. these results indicate that the long-term exposure to this pollutant may be one of the most important contributors to fatality caused by the covid-19 virus in these regions and maybe across the whole world. the outbreak of the novel coronavirus is an ongoing global epidemic event which started in the city of wuhan, china in late 2019. by march 2020 the virus has spread globally and was declared as pandemic by the world health organization (world health organization, 2020). covid-19 is an acute respiratory disease which may lead to pneumonia with symptoms such as fever, cough and dyspnea (jiang et al., 2020) and has an approximate fatality rate of 2-3% (rodriguez-morales et al., 2020 science of the total environment j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / s c i t o t e n v been 209,839 confirmed cases and 8788 deaths reported globally. early studies concluded that the risk factors associated with the development of the disease are older age , history of smoking (liu et al., 2020) , hypertension and heart disease . the italian institute of health (istituto superiore di sanità) reported background diseases of 481 patients in italy who passed away due to covid-19 infection. table 1 shows the information about the most common background diseases which are evident in over 20% of the cases. furthermore, recent studies suggest that the cause of death of many covid-19 patients was related to cytokine storm syndrome mehta et al., 2020) . this syndrome, also known as hypercytokinemia is an uncontrolled release of proinflammatory cytokines (tisoncik et al., 2012) and it is a severe reaction of the immune system, leading to a chain of destructive processes in the body that can end in death. many studies have shown that the incidence of these diseases can also be caused by a long exposure to air pollution, especially nitrogen dioxide (no 2 ), a toxic component. no 2 enters the atmosphere as a result of anthropogenic activity (mostly fossil fuel combustion from vehicles and power plants) and natural processes (lightning and soil processes). elevated exposure to no 2 has been associated with hypertension (saeha et al., 2020) , heart and cardiovascular diseases (gan et al., 2012; mann jennifer et al., 2002; arden et al., 2004) , increased rate of hospitalization (mann jennifer et al., 2002) , chronic obstructive pulmonary disease (copd) (de et al., 1993; euler et al., 1988) , significant deficits in growth of lung function in children (avol et al., 2001; james gauderman et al., 2000) , poor lung function in adults or lung injury (bowatte et al., 2017; rubenfeld et al., 2005) and diabetes (saeha et al., 2020) . in addition to these, other studies have focused on the immune system's response to no 2 exposure. blomberg et al., 1999 , found that exposure to no 2 causes an inflammatory response in the airways and devalia et al., 1993 , showed that these exposures may induce the synthesis of proinflammatory cytokines from airway epithelial cells which consequently play an important role in the etiology (cause) of airway disease. moreover, the epithelial cells in the lung may be uniquely susceptible to death when exposed to no 2 (persinger et al., 2002) . high no 2 concentration is significantly associated with respiratory mortality (beelen et al., 2008; chen et al., 2007; hoek et al., 2013) and is also responsible for generating some harmful secondary pollutants such as nitric acid (hno 3 ) and ozone (o 3 ) (khoder, 2002) . as a result, the who has stated that the health risks may potentially occur due to the presence of no 2 or its secondary products (world health organization, 2003) . accordingly, the who understands the health issues arising from no 2 and suggests that the world population should be protected from exposure to this pollutant. the objective of this work is to assess the contribution of a long-term exposure to no 2 on coronavirus fatality. this is achieved by combining three databases: the tropospheric concentration of no 2 , the atmospheric condition as expressed by the vertical airflow, and the number of fatality cases. the data is processed at the administrative level for each country to obtain high spatial resolution. the data concerning the number of fatality cases was collected from each country on a regional/administrative level. the use of this method is intended to highlight the spatial variation of the epidemic which exists not only between different countries, but more importantly within each country. moreover, if high mortality rates are observed in two remote regions in two different countries, we need to identify their common factor which may explain mortality. for that, data was collected from 66 administrative regions in italy, spain, france and germany. information about fatalities was taken from the ministry of health (italy), ministry of health, social services and equality (spain), the national agency of public health (france) and the robert-koch-institute and the state health offices (germany). for the no 2 concentration in the troposphere (from surface up to~10 km), the sentinel-5 precursor space-borne satellite (spatial resolution of 5.5 km) was used which is operated and managed by the european commission under the "copernicus" program ( fig. 1) . the satellite operates in a sun-synchronous orbit at 824 km and an orbital cycle of 16 days. the satellite carries a tro-pospheric monitoring instrument (tropomi) which provides a (near-)global coverage of air pollution caused by no 2 and other pollutants such as o 3 , so 2 , co, ch 4 , ch 2 o and aerosols (veefkind et al., 2012) . for this study, long-term exposure was defined as a twomonth period (january-february 2020) prior to the outbreak of covid-19 in europe. the spatial data was collected using the google earth engine api (gorelick et al., 2017) . the global coverage of tropospheric no 2 for this time period was extracted using 832 different images followed by calculating the mean concentration for each administrative region. subsequently, only the maximum concentration value was used due to differences in the size of the regions. due to the thickness of the troposphere, the value which represents the no 2 concentration is not enough. there is also a need to understand the vertical airflow during the same period of the event. for that purpose, the vertical airflows at 850 mb (~1.5 km above sea level) was used as it defines the atmospheric capability to disperse the gas (fig. 2) . this data was provided by the noaa/oar/esrl psd, boulder, colorado, usa (http://www.esrl.noaa.gov/psd/). downwards airflows are given by positive values of omega (in pa/s), while upwards airflow by negative values of omega. in regions where positive omega is observed, the atmospheric will force the no 2 to stay close to the surface which leads the population to be exposed to the risk factor. in contrast, in regions with negative omega, the atmospheric conditions will disperse the gas further away and to higher altitudes. in these regions, the population is less exposed to the air pollution and to its associated health risks. mapping the tropospheric no 2 over europe reveals a major 'hotspot' of high concentration in the northern part of italy. the 'hotspot' is observed in the po valley which extends from the slopes of the western alps to the coastal plains of the adriatic sea. out of the top five regions where high fatality was observed, four of them were in northern italy (fig. 3) : lombardia, (2168 cases), emilia-romanga (531), piemonte (175 cases) and veneto (115 cases). the other region was in the administrative region 'community of madrid' (comunidad de madrid), spain (498 cases) which, like the po valley, is also surrounded by mountain ranges. as shown in fig. 4 , 78% of all fatalities due to coronavirus in these selected countries occurred in those regions. the concentrations of no 2 were high and ranged between 177.1 and 293.7 μmol/m 2 , accompanied by downwards airflows (positive omega ranged between 0.04 and 0.07 pa/s). there were 4443 fatalities in these countries due to covid-19 by march 19, 2020. 83% of all fatalities (3701 cases) occurred in regions where the maximum no 2 concentration was above 100 μmol/m 2 , 15.5% (691 cases) occurred in regions where the maximum no 2 concentration was between 50 and 100 μmol/m 2 , and only 1.5% of all fatalities (51 cases) occurred in regions where the maximum no 2 concentration was below 50 μmol/m 2 . in this study, the concentrations of the tropospheric no 2 which were extracted from the sentinel-5p satellite were used in order to explain the spatial variation of fatality cases in 66 administrative regions in four european countries. the sentinel-5p data shows two main no 2 hotspots over europe: northern italy and madrid metropolitan area. according to these results, high no 2 concentration accompanied by downwards airflows cause of no 2 buildup close to the surface. this topographic structure combined with atmospheric conditions of inversion (positive omega) prevent the dispersion of air pollutants, which can cause a high incidence of respiratory problems and inflammation in the local population. this chronic exposure could be an important contributor to the high covid-19 fatality rates observed in these regions. as earlier studies have shown that exposure to no 2 causes inflammatory in the lungs, it is now necessary to examine whether the presence of an initial inflammatory condition is related to the response of the immune system to the coronavirus. hence, poisoning our environment means poisoning our own body and when it experiences a chronic respiratory stress, its ability to defend itself from infections is limited. according to these results, more studies should be conducted which focus on additional factors such as age and presence of pre-existing and background diseases along with the impact of pre-exposure to no 2 and hypercytokinemia in order to verify their impact on fatalities due to the covid-19 pandemic. the author declares no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. cardiovascular mortality and long-term exposure to particulate air pollution respiratory effects of relocating to areas of differing air pollution levels long-term effects of traffic-related air pollution on mortality in a dutch cohort (nlcs-air study) persistent airway inflammation but accommodated antioxidant and lung function responses after repeated daily exposure to nitrogen dioxide traffic-related air pollution exposure over a 5-year period is associated with increased risk of asthma and poor lung function in middle age outdoor air pollution: nitrogen dioxide, sulfur dioxide, and carbon monoxide health effects clinical characteristics and risk factors for fatal outcome in patients with 2019-coronavirus infected disease (covid-19) in wuhan chronic disease associated with long-term concentrations of nitrogen dioxide effect of nitrogen dioxide on synthesis of inflammatory cytokines expressed by human bronchial epithelial cells in vitro chronic obstructive pulmonary disease symptom effects of long-term cumulative exposure to ambient levels of total oxidants and nitrogen dioxide in california seventh-day adventist residents association of long-term exposure to community noise and traffic-related air pollution with coronary heart disease mortality google earth engine: planetary-scale geospatial analysis for everyone the origin, transmission and clinical therapies on coronavirus disease 2019 (covid-19) outbreak -an update on the status long-term air pollution exposure and cardio-respiratory mortality: a review. environ association between air pollution and lung function growth in southern california children review of the clinical characteristics of coronavirus disease 2019 (covid-19) atmospheric conversion of sulfur dioxide to particulate sulfate and nitrogen dioxide to particulate nitrate and gaseous nitric acid in an urban area analysis of factors associated with disease outcomes in hospitalized patients with 2019 novel coronavirus disease air pollution and hospital admissions for ischemic heart disease in persons with congestive heart failure or arrhythmia covid-19: consider cytokine storm syndromes and immunosuppression molecular mechanisms of nitrogen dioxide induced epithelial injury in the lung covid-19, an emerging coronavirus infection: current scenario and recent developments -an overview incidence and outcomes of acute lung injury association between road traffic noise and incidence of diabetes mellitus and hypertension in toronto, canada: a population-based cohort study into the eye of the cytokine storm. microbiol tropomi on the esa sentinel-5 precursor: a gmes mission for global observations of the atmospheric composition for climate, air quality and ozone layer applications world health organization, 2020. coronavirus disease 2019 (covid-19) situation report -51 risk factors associated with acute respiratory distress syndrome and death in patients with coronavirus disease 2019 pneumonia in wuhan, china acknowledgments i wish to thank prof. michael hopp for his assistance with the drafting and prof. hadas saaroni for her assistance with the analysis of the atmospheric data. prof. hopp and prof. saaroni are faculty members in the department of geography and the human environment at tel-aviv university. none of these individuals received compensation for their contributions. key: cord-265078-u19e9j2w authors: xie, jingui; zhu, yongjian title: association between ambient temperature and covid-19 infection in 122 cities from china date: 2020-07-01 journal: sci total environ doi: 10.1016/j.scitotenv.2020.138201 sha: doc_id: 265078 cord_uid: u19e9j2w background: coronavirus disease 2019 (covid-19) has become a severe public health problem globally. both epidemiological and laboratory studies have shown that ambient temperature could affect the transmission and survival of coronaviruses. this study aimed to determine whether the temperature is an essential factor in the infection caused by this novel coronavirus. methods: daily confirmed cases and meteorological factors in 122 cities were collected between january 23, 2020, to february 29, 2020. a generalized additive model (gam) was applied to explore the nonlinear relationship between mean temperature and covid-19 confirmed cases. we also used a piecewise linear regression to determine the relationship in detail. results: the exposure-response curves suggested that the relationship between mean temperature and covid-19 confirmed cases was approximately linear in the range of <3 °c and became flat above 3 °c. when mean temperature (lag0–14) was below 3 °c, each 1 °c rise was associated with a 4.861% (95% ci: 3.209–6.513) increase in the daily number of covid-19 confirmed cases. these findings were robust in our sensitivity analyses. conclusions: our results indicate that mean temperature has a positive linear relationship with the number of covid-19 cases with a threshold of 3 °c. there is no evidence supporting that case counts of covid-19 could decline when the weather becomes warmer, which provides useful implications for policymakers and the public. • mean temperature of last two weeks (when b 3°c) was positively associated with newly confirmed covid-19 cases. • 1°c rise in the mean temperature of last weeks (when b 3°c) was associated with a 4.861% increase in the daily confirmed cases. • there is no evidence supporting that case counts of covid-19 could decline when the weather becomes warmer. a b s t r a c t a r t i c l e i n f o coronavirus disease 2019 , caused by the novel coronavirus, was first discovered in wuhan city, china (chen et al., 2020; lu et al., 2020) . subsequently, it spread rapidly to other provinces, although the government has taken timely measures to shut down the science of the total environment j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / s c i t o t e n v traffic (du et al., 2020; kupferschmidt and cohen, 2020) . as of 29 february 2020, data from the national health commission have shown that n79,000 confirmed cases have been identified and over 2800 deaths in the whole of china. besides china, other countries and regions are also affected by covid-19, which has become a serious public health problem globally (sohrabi et al., 2020; xu et al., 2020) . covid-19 infection could cause severe respiratory illness, similar to severe acute respiratory syndrome coronavirus (sars-cov) xu et al., 2020) . generally, fever, cough, and myalgia or fatigue are common symptoms at the onset of illness . early studies have demonstrated person-to-person transmission of covid-19 through direct contact or droplets (chan et al., 2020; lai et al., 2020; wang et al., 2020) . specifically, a study reported that presumed person-to-person hospital-associated transmission of covid-19 was suspected in 41% of patients . in addition to human-to-human contact, both epidemiological and laboratory studies have shown that ambient temperature is an important factor in the transmission and survival of coronaviruses (bi et al., 2007; casanova et al., 2010; chan et al., 2011; tan et al., 2005; van doremalen et al., 2013) . for example, temperature could increase or decrease the transmission risk by affecting the survival time of coronaviruses on surfaces (casanova et al., 2010; chan et al., 2011; van doremalen et al., 2013) . therefore, it is reasonable to explore the effect of temperature on the spread of this novel coronavirus. to provide useful implications for policymakers and the public, our paper aimed to investigate the relationship between daily mean temperature and newly confirmed covid-19 cases in 122 cities from china. our study included 118 prefecture-level cities and 4 municipalities that covered the majority of the chinese mainland (19.1°to 51.4°n orth latitude and 83.4°to 131.6°east longitude). fig. 1 shows the locations of these 122 cities and the cumulative confirmed cases in each city as of february 29, 2020. we focused on these cities since the meteorological data we have obtained was limited (not including all cities in china). daily confirmed cases were collected from the official websites of health commissions in corresponding provinces or cities between january 23, 2020 (i.e., the lockdown of wuhan) to february 29, 2020. we obtained the data after the closure of wuhan to minimize the potential inclusion of imported cases in this study. meteorological data during the same study period for each city were collected from national meteorological information center (http://data. cma.cn). meteorological factors included daily mean temperature, relative humidity, air pressure, and wind speed. the generalized additive model (gam) is a semi-parametric extension of the generalized linear model (glm), which is useful to explore the nonlinear relationship between weather factors and health outcomes liu et al., 2020; peng et al., 2006; talmoudi et al., 2017; wu et al., 2018) . because the temperature effect could last for several days and the incubation period of covid-19 ranges from 1 day to 14 days (reported by national health commission in china), it is a reasonable choice to use a moving-average approach to account for the cumulative lag effect of temperature (duan et al., 2019; li et al., 2018; lu et al., 2015) . therefore, in this study, a gam with a gaussian distribution family (hastie, 2017; liu et al., 2020) was applied to examine the moving average lag effect (lag0-7, lag0-14, lag0-21) of mean temperature on daily confirmed cases of covid-19. the model was defined as follows: in the model, log(y it ) is the log-transformed newly covid-19 counts in city i on day t (added one to avoid taking the logarithm of zeros) . a is the intercept and s(•) denotes a thin plate spline function with the maximum 2 degrees of freedom to avoid overfitting wang et al., 2018) . meantem il is the (l + 1)-day moving average term (lag0-l) of daily mean temperature in city i. we also controlled the relative humidity (rhu il ), air pressure (prs il ), and wind speed (win il ) during the same period for the possible confounding effect. log(y i,t−1 ) is the log-transformed covid-19 counts lagged one day in city i to account for potential serial correlation in the data (hunter et al., 2019; liu et al., 2020) . city i is the city fixed effect variable and day t captures day fixed effect (amuakwa-mensah et al., 2017) . according to the results from the gams, then we used a piecewise linear regression to determine the relationship between mean temperature and covid-19 confirmed cases in detail dukić et al., 2012; kim et al., 2016; qian et al., 2008) . in the sensitivity analysis, we first excluded wuhan city from our data because it was the worst-hit region in china and the number of confirmed cases was much larger than that of other cities. second, we changed the maximum degree of freedom for the spline function to 3 to examine whether our main results were robust. gams in our analysis were implemented via the "mgcv" package (version 1.8-28) of r software (version 3.5.2). the statistical tests were two-sided, and p b 0.05 was considered statistically significant. table 1 summarizes the descriptive statistics for covid-19 confirmed cases and meteorological variables. this study included n58,000 cases during the observation period (january 23, 2020 to february 29, 2020) and the average number was 12.726. average daily mean temperature, relative humidity, air pressure, and wind speed were 3.118°c, 67.48%, 964.931 hpa, and 2.116 m/s, respectively. table 2 shows the correlation coefficients among the meteorological variables. mean temperature had significantly positive correlations with relative humidity (r = 0.354, p b 0.05) and air pressure (r = 0.163, p b 0.05). however, mean temperature was negatively correlated with wind speed (r = −0.053, p b 0.05). the exposure-response curves in fig. 2 suggested that the relationship between temperature and covid-19 confirmed cases was significantly nonlinear (lag0-7: p b 0.001, lag0-14: p b 0.001, lag0-21: p b 0.001). specifically, the relationship was approximately linear in the range of b3°c and became flat above 3°c, indicating that the single threshold of the temperature effect on covid-19 was 3°c. based on results from gams, a piecewise linear regression was adapted with a threshold at a 3°c to quantify the effect of temperature above and below the threshold. as showed in table 3 , each 1°c rise in mean temperature (lag0-7) led to a 3.432% (95% ci: 2.277-4.586) increase in the daily number of covid-19 confirmed cases when mean temperature was below 3°c. this positive effect is largest at lag0-21 (percentage change = 6.953%, 95% ci: 4.681-9.225). when mean temperature was above 3°c, the negative effect of temperature was not statistically significant. the nonlinear relationship was robust after excluding wuhan city from our data (fig. 3) . we also used a piecewise linear model to quantify the effect in this sensitivity analysis (table 4) . below the threshold 3°c, the confirmed cases increased by 6.949% (95% ci: 4.692-9.205) for every 1°c rise in mean temperature (lag0-21). our main finding was robust when we changed the maximum degree of freedom for the spline function to 3 (figs. s1-s2) in this paper, we explored the nonlinear relationship between ambient temperature and covid-19 confirmed cases by using a generalized additive model. the exposure-response relationship was positive linear when the mean temperature below 3°c and became flat above 3°c, indicating that higher temperature may not limit the transmission of this novel coronavirus. previous studies have showed that temperature is also an important factor in the survival and transmission of other coronaviruses, like sars-cov and mers-cov (bi et al., 2007; casanova et al., 2010; chan et al., 2011; tan et al., 2005; van doremalen et al., 2013) , so we compared our main findings with results in these studies. tan et al. (2005) found that the optimum environmental temperature related to sars cases was from 16°c to 28°c based on data from hong kong, guangzhou, beijing, and taiyuan. moreover, bi et al. (2007) reported that temperature had a negative relationship with sars transmission in hong kong and beijing in 2003. a laboratory study using surrogate viruses to investigate the effect of temperature on coronavirus survival on surfaces showed that viruses were inactivated more rapidly at 20°c than at 4°c (casanova et al., 2010) . another laboratory study found that coronavirus on smooth surfaces was stable for over 5 days when temperature at 22°c-25°c, and virus viability was rapidly lost at higher temperatures (e.g., 38°c) (chan et al., 2011 ). van doremalen et al. (2013 also observed that mers-cov was less stable at high temperature. in brief, most studies showed that there was an optimum temperature for coronavirus and high temperature was harmful to its viability. however, this paper could not observe a negative effect of high temperature on covid-19 infection. a possible reason may be that the study period was limited in winter, with maximal mean temperature 26.9°c. further laboratory studies also need to be conducted to determine the underlying mechanism. our study has some implications. first, the nonlinear relationship between ambient temperature and covid-19 confirmed cases showed covid-19 may not perish of itself without any public health interventions when the weather becomes warmer. so, the public and governments could not expect the high temperature to eradicate this novel virus. additionally, increasing temperature in regions or periods below 3°c is related to the high risk of transmission, which provides useful information for policymakers if the novel coronavirus coexists with human for a long time. ⁎ p b 0.05. fig. 3 . exposure-response curves for the effects of temperature on covid-19 confirmed cases after excluding wuhan. the x axis is the mean temperature (7-day, 14-day and 21-day moving average). the y axis indicates the contribution of the smoother to the fitted values. however, several limitations should be acknowledged. first, we could not conduct subgroup analysis by gender and age group to explore the sensitive population because there was a lack of patient information. second, although the government has established a good disease surveillance system, under-reporting may still occur and could affect our main findings, especially at the beginning of covid-19 outbreak. third, our data only covered cities in china. further studies on the effects of temperature on covid-19 transmission in other countries are needed. to the best of our knowledge, this is the first study to investigate the nonlinear relationship between ambient temperature and daily covid-19 confirmed cases. our results indicate that mean temperature has a positive linear relationship with the number of covid-19 cases when the temperature is below 3°c. there is no evidence supporting that case counts of covid-19 could decline when the weather becomes warmer, which provides useful implications for policymakers and the public. the authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. climate variability and infectious diseases nexus: evidence from sweden weather: driving force behind the transmission of severe acute respiratory syndrome in china? effects of air temperature and relative humidity on coronavirus survival on surfaces the effects of temperature and relative humidity on the viability of the sars coronavirus a familial cluster of pneumonia associated with the 2019 novel coronavirus indicating 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elsewhere? severe acute respiratory syndrome coronavirus 2 (sars-cov-2) and corona virus disease-2019 (covid-19): the epidemic and the challenges impact of weather factors on influenza hospitalization across different age groups in subtropical hong kong early transmission dynamics in wuhan, china, of novel coronavirus-infected pneumonia ambient particulate matter air pollution associated with acute respiratory distress syndrome in guangzhou climate factors and the east asian summer monsoon may drive large outbreaks of dengue in china short-term effects of air pollution on daily mortality and years of life lost in nanjing outbreak of pneumonia of unknown etiology in wuhan china: the mystery and the miracle model choice in time series studies of air pollution and mortality high temperatures enhanced acute mortality effects of ambient particle pollution in the "oven" city of wuhan, china. environ. health perspect world health organization declares global emergency: a review of the 2019 novel coronavirus (covid-19) modeling zoonotic cutaneous leishmaniasis incidence in central tunisia from 2009-2015: forecasting models using climate variables as predictors an initial investigation of the association between the sars outbreak and weather: with the view of the environmental temperature and its variation stability of middle east respiratory syndrome coronavirus (mers-cov) under different environmental conditions a time-series study of the association of rainfall, relative humidity and ambient temperature with hospitalizations for rotavirus and norovirus infection among children in hong kong clinical characteristics of 138 hospitalized patients with 2019 novel coronavirus-infected pneumonia in wuhan non-linear effects of mean temperature and relative humidity on dengue incidence in guangzhou pathological findings of covid-19 associated with acute respiratory distress syndrome the study was partially supported by the national natural science foundation of china [grant 71571176]. supplementary data to this article can be found online at https://doi. org/10.1016/j.scitotenv.2020.138201. key: cord-320787-dwyyjq6o authors: la rosa, giuseppina; iaconelli, marcello; mancini, pamela; ferraro, giusy bonanno; veneri, carolina; bonadonna, lucia; lucentini, luca; suffredini, elisabetta title: first detection of sars-cov-2 in untreated wastewaters in italy date: 2020-05-23 journal: sci total environ doi: 10.1016/j.scitotenv.2020.139652 sha: doc_id: 320787 cord_uid: dwyyjq6o abstract several studies have demonstrated the advantages of environmental surveillance through the monitoring of sewage for the assessment of viruses circulating in a given community (wastewater-based epidemiology, wbe). during the covid-19 public health emergency, many reports have described the presence of sars-cov-2 rna in stools from covid-19 patients, and a few studies reported the occurrence of sars-cov-2 in wastewaters worldwide. italy is among the world's worst-affected countries in the covid-19 pandemic, but so far there are no studies assessing the presence of sars-cov-2 in italian wastewaters. to this aim, twelve influent sewage samples, collected between february and april 2020 from wastewater treatment plants in milan and rome, were tested adapting, for concentration, the standard who procedure for poliovirus surveillance. molecular analysis was undertaken with three nested protocols, including a newly designed sars-cov-2 specific primer set. sars-cov-2 rna detection was accomplished in volumes of 250 ml of wastewaters collected in areas of high (milan) and low (rome) epidemic circulation, according to clinical data. overall, 6 out of 12 samples were positive. one of the positive results was obtained in a milan wastewater sample collected a few days after the first notified italian case of autochthonous sars-cov-2. the study confirms that wbe has the potential to be applied to sars-cov-2 as a sensitive tool to study spatial and temporal trends of virus circulation in the population. severe acute respiratory syndrome coronavirus 2 (sars-cov-2) is responsible for the coronavirus disease covid-19, a public health emergency worldwide. on march 11 th 2020, the world health organization declared covid-19 a pandemic. italy is among the world's most affected countries in the covid-19 pandemic. indeed, after entering italy, covid-19 has been spreading fast. as of april 20 th 2020, the total number of cases reported by the authorities reached 181,228, with 108,237 active cases (dipartimento della protezione civile, bulletin 20.04.2020), mainly located in northern italy (lombardy, and its neighbouring regions of emilia-romagna and piedmont). presymptomatic and paucisymptomatic carriers, mostly undetected in clinical and laboratory surveillance systems, contribute to the spread of the disease (bay et al., 2020; nicastri et al., 2020; rothe et al., 2020; who, 2020) and hamper the efforts made to assess the extent of sars-cov-2 circulation in the population and to control efficiently virus transmission. analytical regular investigation of wastewaters provides valuable information to measure viral circulation in the population as wastewater treatment plants (wwtps), collecting and concentrating human excreta, are useful sampling points receiving discharges from the entire community. environmental microbiologists have studied pathogens in sewage for decades (la rosa & muscillo, 2012; sinclair et al., 2008) . the screening of wastewater, as a public health surveillance tool, defined as wastewater-based epidemiology (wbe), is currently well recognized (daughton, 2018; xagoraraki & o'brien, 2020) . in the recent years, scientists have applied wbe to a wide range of waterborne, foodborne and fecal-oral viruses, which infected individuals usually excrete in high concentration with faeces (katayama et al., 2008; iaconelli et al., 2017; bisseaux et al., 2018) . however, the concept of wbe can also be applied to viruses beyond those commonly associated with the faecal-oral route (i.e. enteric viruses), since viral shedding may involve different body fluids ultimately discharged into urban sewage. some studies have reported the presence of viral rna in the stools of covid-19 patients in percentages ranging from 16.5% to 100% at a concentration up to 6.8 log 10 genome copies/g of stool (chen et al., 200; lo et al., 2000; han et al., 2000; lescure et al., 2000) . furthermore, preliminary studies have reported the detection of sars-cov-2 rna in wastewater in the netherlands (medema et al., 2020) , france (wurtzer et al., 2020) , usa (wu et al., 2020), and australia (ashmed et al., 2020) . to date, no study has yet provided insights into the presence of sars-cov-2 in wastewaters in italy. herein we report the results of the screening for sars-cov-2 presence in sewage samples collected between the end of february and the beginning of april 2020 from wwtps in milan (northern italy) and rome (central italy). twelve raw sewage samples were collected between the 3 rd of february and the 2 nd of april 2020 from three wwtps, located in milan (two distinct plants, reported as a and b) and in rome (one plant receiving two different pipelines, c1 and c2, from different districts of the town), respectively. total numbers of inhabitants served by these wwtps (expressed as population equivalents) were 1.050.000, 1.050.000, and 900.000, for plant a, b, and c, respectively. composite samples, representing 24-hour period were collected from the wwtp influent, immediately stored at -20 °c, and dispatched frozen to the national institute of health for analysis. before viral concentration, samples underwent a 30 min treatment at 56°c to increase the safety of the analytical protocol for the laboratory personnel and environment. after heat treatment, samples were processed using class ii biological safety cabinets, and standard precautions were applied j o u r n a l p r e -p r o o f (hand hygiene products and personal protective equipment e.g., gloves, gowns, face and eye protection). sample concentration took place using a two-phase (peg-dextran method) separation as detailed in the 2003 who guidelines for environmental surveillance of poliovirus protocol (who, 2003) , with modifications to adapt the protocol to enveloped viruses. in brief, the wastewater sample (250 ml) was centrifuged to pellet the wastewater solids, retaining the pellet for further processing. the clarified wastewater was mixed with dextran and polyethylene glycol (peg), and the mixture was left to stand overnight at 4°c in a separation funnel. the bottom layer and the interphase were then collected drop-wise, and this concentrate was added to the pellet from the initial centrifugation. the chloroform treatment that the who protocol envisages at this stage was omitted to preserve the integrity of the enveloped viruses object of this study. the extraction of viral rna was done using the nuclisens minimag semi-automated extraction system with magnetic silica carried out following manufacturer's instructions (biomerieux, marcy l'etoile, france) with however slight modifications. the lysis phase was prolonged to 20 minutes, and brief centrifugation (2000 × g, 1 min) was used to pellet the sediment; subsequently, magnetic silica beads were added to the cleaned supernatant. before molecular tests, the extracted nucleic acids were further purified from potential pcr inhibitors using the onestep pcr inhibitor removal kit (zymo research, ca, usa). in the absence of a standardized method for sars-cov-2 detection in environmental samples, rnas were tested for the presence of sars-cov-2 using three different nested rt-pcr assays and one real-time qpcr assay (table 1 and figure 1 b) a newly designed primer set specific for sars-cov-2. novel nested primers, amplifying a 332 bp fragment of orf1ab, were designed using primer3 software (http://primer3.ut.ee/). for the assays a) and b) first-strand cdna was synthesized using super script iv reverse transcriptase (thermofisher scientific) with the reverse primer. pcr reaction was performed using 2.5 µl of cdna in a final volume of 25 µl (kit platinum™ superfi™ green pcr master mix, thermo), using 1 µl of primers (10 µm). the pcr conditions were as follows: 98 °c for 30 sec; 35 cycles of 98 °c for 10 sec, 50 °c and 54 °c for 10 sec for assay a) and b), respectively, and 72 °c for 30 sec; final extension 72 °c for 5 min. after the first round pcr, nested pcr was performed using 2 µl of first pcr product and under the same reaction composition and thermal profile conditions. a synthetic dna (biofab research, italy) including the pcr target region, was used to set up pcr conditions before experiments with study samples, but was not amplified along with samples to avoid risks of pcr contamination. molecular grade water was used as the negative control. c) a published nested rt-pcr for sars-cov-2 targeting the spike region (nao et al., 2020). cdna was synthesized from 5 l of sample rna, using superscript iii reverse transcriptase (thermofisher scientific), 0.5 m of the reverse primer (wuhancov-spk2-r, table 1 ) and a 50 min reaction at 50 °c (20 l final volume). first pcr reaction was performed by adding the reaction mix (dream taq polymerase and buffer from thermofisher scientific, 0.4 m of primers wuhancov-spk2-r and wuhancov-spk1-f) directly to the whole volume of synthesized cdna. the used pcr conditions were as follows: 95°c for 1 min; 35 cycles of 95 °c for 30 sec, 56 °c for 30 sec, and 72 °c for 40 sec; final extension 72 °c for 5 min. nested pcr (primers niid_wh-1_f24381 and niid_wh-1_r24873) was performed in a total volume of 50 µl using 5 µl of first pcr product, with the same conditions applied for the first pcr and 45 cycles. all reactions were performed in duplicate. for standard curve construction, the targeted region, coupled with a t7 promoter, was synthetized and quantified by eurofins genomics (germany), and tenfold dilutions were used for curve construction. in vitro synthetized rna using the standard curve dna as a template was used as an external amplification control to check for pcr inhibition. all amplifications were conducted on a quantstudio 12k instrument (thermo scientific). molecular biology water served as a non-template control. all samples were retested for confirmation of results obtained with methods a), b), and c). the pcr products were revealed by electrophoresis on 2% agarose gels and were purified using a montage pcrm96 microwell filter plate (millipore, billerica, ma, usa) and then direct sequenced on both strands (biofab research, rome, italy). sequences were identified in terms of the closest homology sequence using blast https://blast.ncbi.nlm.nih.gov/blast.cgi. all italian sars-cov-2 genome sequences available at the time of analysis were retrieved from gisaid (https://www.gisaid.org/) for comparison with study sequences, using the mega x software (kumar et al., 2018) .. sequences were submitted to ncbi genbank with the accession numbers: mt373156-mt373163. the 50% (6/12) of the wastewater samples showed positive results for sars-cov-2 rna, and the newly designed assay in the rdrp gene showed a higher sensitivity compared to the assay targeting j o u r n a l p r e -p r o o f the spike gene (table 2 ). both the published and newly designed sars-cov-2 specific primer sets detected bands of the expected size and were confirmed by sequencing. in contrast, only unspecific products were detected with a broad range assay for coronavirus. upon comparison of broad range primers with sars-cov-2 genome, we noted that they showed only 77.1 to 91.3 % nt identity, which explain why these were not able to amplify the novel coronavirus. no positive results were obtained by real-time rt-qpcr, therefore no quantitative data could be provided for the positive samples. this may be related to the sensitivity of the rdrp assay used in this study. indeed, in recent comparative studies, the sensitivity of this assay was shown to be low compared to others developed by who referral laboratories (etievant, 2020). in particular, the limit of detection (lod) of this assay was estimated at 316 viral genomic equivalents per reaction by nalla and coworkers (2020) and above 500 genome copies per reaction by vogel et al. (2020) as well as in our hands (data not shown), suggesting that virus concentration was below the lod of the assay. however, the external inhibition control associated to this assay was useful to confirm the acceptable levels of pcr inhibitors, all samples being below the acceptability criterion (median inhibition 29.1%, range 8.7%-51.4%). in this study, a thermal treatment of samples (30 min at 56 °c) was included before concentration to increase the safety for the laboratory personnel during sample manipulation. these conditions were reported to reduce the virulence of sars-cov-2 by over 5 log without affecting rna integrity following this investigation on the occurrence of sars-cov-2 rna in sewage, the production of quantitative data on virus concentration in raw sewage will be undertaken with the use of molecular methods optimized for environmental samples. this approach will allow obtaining a rough estimation of the total number of subjects excreting the virus, by integrating -as done by wu and co-workers in samples taken in the united states (wu et al., 2020) -the available information on viral shedding rates, wwtps loads, and virus concentration in wastewaters. moreover, the environmental surveillance will be extended to the collection of wastewater samples available in the department of environment and health of the italian national health institute, that were collected throughout italy in the framework of different projects on enteric viruses. such monitoring will provide a picture of the sars-cov-2 circulation across the different regions of italy and over time, to better understand the virus circulation, as provided by wastewater-based epidemiology (wbe) and compare it to the clinical data. samples collected before the reporting of the first known italian case on february 21 will also be tested, to possibly infer when sars-cov-2 first appeared in italy. in a previous study, indeed, wastewater monitoring provided evidence that a novel variant of norovirus gii.17 (termed kawasaki 2014) had been circulating in the italian population before its first appearance and identification in clinical cases, later becoming one of the prevalent variants in the population (suffredini et al., 2018) . also and most important, environmental monitoring of sars-cov-2 in sewage will continue when the emergency phase will be over, and its circulation in the population will be considered limited. indeed, sewage surveillance could also serve for the early detection of a possible re-emergence of covid-19 in urban areas. who recommends environmental surveillance for poliovirus as an early environmental monitoring, therefore, appears to be an effective measure for proving early warning against pathogen reintroduction. in conclusions, the main findings of this study are: 1) first detection of sars-cov-2 rna fragments in sewage in italy; 2) demonstration of the suitability of the who protocol for sewage treatment to enveloped viruses after appropriate modifications; 3) design of a novel nested pcr assay specific for sars-cov-2, useful for screening purposes. further research will clarify the applicability of wbe to sars-cov-2 for prompt detection, the j o u r n a l p r e -p r o o f × sars-cov-2 not detected; ○ sars-cov-2 detected (orf1ab); • sars-cov-2 detected (spike) a weak positive j o u r n a l p r e -p r o o f authorship statement all persons who meet authorship criteria are listed as authors, and all authors certify that they have participated sufficiently in the work to take public responsibility for the content, including participation in the concept, design, analysis, writing, or revision of the manuscript. furthermore, each author certifies that this material or similar material has not been and will not be submitted to or published in any other publication before its appearance in the hong kong journal of occupational therapy. authorship contributions please indicate the specific contributions made by each author (list the authors' initials followed by their surnames, e.g., y.l. cheung). the name of each author must appear at least once in each of the three categories below. category 1 conception and design of study: glr, es, ll, lb; acquisition of data: mi,pm, gbf, cv; analysis and/or interpretation of data: mi,pm, gbf, cv; glr, es, lb, ll category 2 drafting the manuscript: glr, es revising the manuscript critically for important intellectual content: glr, es category 3 approval of the version of the manuscript to be published (the names of all authors must be effective heat inactivation of sars-cov-2 guidelines for environmental surveillance of poliovirus circulation first data on stability and resistance of sars coronavirus compiled by members of who laboratory network advice on the use of masks in the context of covid-19: interim guidance sars-cov-2 titers in wastewater are higher than expected from clinically confirmed cases time course quantitative detection of sars-cov-2 in parisian wastewaters correlates with covid-19 confirmed cases. medrxiv prep wastewater-based epidemiology for early detection of viral outbreaks key: cord-327628-fl8dyahe authors: yuan, qi; qi, bing; hu, deyun; wang, junjiao; zhang, jian; yang, huanqiang; zhang, shanshan; liu, lei; xu, liang; li, weijun title: spatiotemporal variations and reduction of air pollutants during the covid-19 pandemic in a megacity of yangtze river delta in china date: 2020-08-20 journal: sci total environ doi: 10.1016/j.scitotenv.2020.141820 sha: doc_id: 327628 cord_uid: fl8dyahe abstract in recent decades, air pollution has become an important environmental problem in the megacities of eastern china. how to control air pollution in megacities is still a challenging issue because of the complex pollutant sources, atmospheric chemistry, and meteorology. there is substantial uncertainty in accurately identifying the contributions of transport and local emissions to the air quality in megacities. the covid-19 outbreak has prompted a nationwide public lockdown period and provides a valuable opportunity for understanding the sources and factors of air pollutants. the three-month period of continuous field observations for aerosol particles and gaseous pollutants, which extended from january 2020 to march 2020, covered urban, urban-industry, and suburban areas in the typical megacity of hangzhou in the yangtze river delta in eastern china. in general, the concentrations of pm2.5–10, pm2.5, nox, so2, and co reduced 58%, 47%, 83%, 11% and 30%, respectively, in the megacity during the covid-lock period. the reduction proportions of pm2.5 and co were generally higher in urban and urban-industry areas than those in suburban areas. nox exhibited the greatest reduction (>80%) among all the air pollutants, and the reduction was similar in the urban, urban-industry, and suburban areas. o3 increased 102%–125% during the covid-lock period. the daytime elevation of the planetary boundary layer height can reduce 30% of the pm10, pm2.5, nox and co concentrations on the ground in hangzhou. during the long-range transport events, air pollutants on the regional scale likely contribute 40%–90% of the fine particles in the hangzhou urban area. the findings highlight the future control and model forecasting of air pollutants in hangzhou and similar megacities in eastern china. . a study from the wrf-chem model showed that long-range transport contributed 30%-85% of pm 2.5 in hangzhou (ni et al., 2018) . the wrf-chem model combined with field observations showed that local emissions contributed more than 50% of pm 2.5 in hangzhou (shu et al., 2019) . the wrf/cmaq model results indicated that local emission sources accounted for 15.8%, 68.6%, 48.3% and 59.2% of the overall concentrations of so 2 , no 2 , pm 2.5 and pm 10 , respectively, in hangzhou . in addition to the model work, there is still a lack of field observation data for quantifying the contribution of local emissions and transport in hangzhou (sun et al., 2018; zhang et al., 2020c) . a novel coronavirus named "covid-19" accidently appeared in wuhan city in late december, 2019 wu et al., 2020) and its high infectivity strongly threatened human health xu et al., 2020) . the chinese government took powerful timely actions to control the spread of the virus, such as the highest epidemic emergency response, community lockdown, traffic restrictions, and factory shutdowns. these effective actions stopped people from gathering and successfully reduced the risk of the novel coronavirus infection. note that this public health emergency not only locked down people in the community but stopped the operation of the public traffic system and industry machine, which caused a short-term regional reduction of air pollutant emissions from vehicles and some industries in china (huang et al., 2020b; shi and brasseur, 2020; the strictest nationwide restrictions for preventing the covid-19 spread greatly reduced the primary emissions and weakened the regional transport effect of air pollutants due to the large-scale regional decrease in the primary pollution (huang et al., 2020b; zhang et al., 2020b) . consequently, the pandemic incident becomes a special atmospheric research hotspot due to the dramatic reduction in anthropogenic emissions (bauwens et al., 2020; le et al., 2020; sun et al., 2020) . this special period offers us a unique opportunity to accurately assess how the reduction in local emissions influences the air quality in megacities . in this study, we systematically analyzed the continuous three-month data of particulate and gaseous pollutants at one urban site, three urban-industry sites and six suburban sites in hangzhou. to better understand the variation and reduction in air pollutants, we classified the measurement periods into pre-covid, chinese new year (cny), covid-19 lockdown (covid-lock), covid-recover-i, and covid-recover-ii from 1 january, 2020 to 31 march, 2020. we found a significant reduction in pm 2.5-10 , pm 2.5 , no x , so 2 , co and an increase in o 3 during the covid-lock period. this study preliminarily reveals the contribution of transport and local emissions in a typical urban area in the yrd. the findings provide a reference for future air pollution control in the megacities in eastern china. 1 and table s1 ). the urban and urban-industry sites are located in the east low plain area, and the suburban sites are mostly located in the middle and west mountain areas ( fig. 1) . the urban site is located in the city center with the largest population density and more than 2 million vehicles (table s1 ). the urban-industry sites are located in the industry districts with a total of more than 2600 enterprises and nearly 1 million vehicles (table s1 ). ecotourism is one of the major domains in the suburban area due to the better ecological environment and air quality of this area. fig. 1 shows that the major stationary emissions of air pollutants (i.e., pm 10 , pm 2.5 , no x , and so 2 ) in hangzhou distribute in the urban-industry area. as a result, we determined that the air quality in the urban and urban-industry areas are worse than that in the suburban area (table s1 ). these monitoring sites, which comprise different locations and environments, can represent the different air quality in hangzhou city. visibility (vis) was detected by a visibility sensor (pw10, vaisala, netherlands). our field observations were conducted from 1 january, 2020 to 31 march, 2020. the highest epidemic emergency response in zhejiang province began on 23 january. cny vacation (24 january to 3 february, 2020): there was very low traffic flow (tpi=0.13) and few industries maintained normal operation due to the novel coronavirus epidemic, but large amounts of fireworks were burned in the suburban area. according to the official bans, fireworks were only allowed in the suburban areas in megacities during the cny. the traffic system resumed, and the average tpi was 0.25 in the urban area (fig. s1 ). nearly 100% of enterprises resumed operation during this period according to the statistics of the hangzhou development commission. the epidemic emergency response in zhejiang province was downgraded beginning on 2 march. the industry operation returned to normal, and the traffic system was further recovered (tpi=0.9). concentration-weighted trajectory (cwt) analysis, which is based on the backward trajectory, can be employed to identify the transport event and estimate the contribution of air pollutants from different regions . in this study, 72-hour air mass backward trajectories with one-hour resolution were calculated with an ending height of 500 m above ground level based on the meteorological data sets from the nation oceanic atmospheric administration (noaa) during the observation period, the daily average mass concentrations of pm 10 , concentrations of pm 2.5 , no x , and co at the urban site were higher than those at the urban-industry and suburban sites (table s2) , which suggests that vehicle emissions was the major source of air pollutants in the urban area. the weather conditions were mostly stable with low wind speeds (<3 m/s) and high rh (~77%) during the observation period (fig. 2) . to evaluate the reduction in air pollutants during the covid-lock period, the temporal variations in the six air pollutants (i.e., pm 2.5-10 , pm 2.5 , no x , so 2 , co, and during the covid-lock period, the average pm 2.5-10 mass concentrations at the urban site, urban-industry site, and suburban site were 8.5 μg/m 3 , 11.5 μg/m 3 , and 7.0 μg/m 3 , respectively, which decreased 54%, 62%, and 58%, respectively, compared with those during the pre-covid period (figs. 3a and s2a). coarse particles (pm 2.5-10 ) in the megacities of eastern china are mainly dominated by man-made fugitive dust from construction activities and roads, natural dust from the ground, growth of secondary aerosol particles, and industrial activities in urban areas (guo et al., 2020) . a higher reduction proportion of the coarse particles occurred at the urban-industry sites than that at the urban and suburban sites, which suggests that man-made dust during the covid-lock period, the average so 2 concentrations at the urban site, urban-industry site, and suburban site were 3.9 μg/m 3 , 6.2 μg/m 3 , and 4.0 μg/m 3 , respectively, which decreased 22%, 9%, and 9%, respectively, compared with those during the pre-covid period (figs. 3d and s2d). so 2 control was effective on normal days, and the average reduction proportion of so 2 was the lowest among all the air pollutants. emissions of industrial and coal-fired power plants are the major sources of so 2 in zhejiang province . we noticed that the slight j o u r n a l p r e -p r o o f journal pre-proof increase in so 2 concentrations occurred during the covid-recover-ii period due to the higher production intensity than that during the pre-covid period, which made up the production shortage during the covid-lock period in china. (ding et al., 2013; zhang et al., 2018) . in addition, the reduction of pm 2.5 is in favor of the o 3 formation ; this mechanism promotes the increase in o 3 during the covid-lock period. in general, the lockdown actions during the covid-lock period achieved obvious positive effectiveness for the air quality improvement in hangzhou. we journal pre-proof discover that all the air pollutants, with the exception of o 3 , decreased during the covid-lock period and the reduction proportion of each pollutant was generally higher in urban and urban-industry areas than the suburban areas. no x exhibited the highest reduction with a maximum decrease of ~80%. o 3 is the only air pollutant that exhibited an obvious increase more than 1 time during the covid-lock period. during the covid-lock period, a continuously low traffic flow was maintained and few industries maintained normal production. based on the minimum continuous local and regional emissions in the yrd during the covid-lock period, it is an opportunity to generally evaluate the role of the planetary boundary layer (pbl) in the local air pollutants in hangzhou. fig. 4 shows that pm 2.5-10 , pm 2.5 , no x and co all exhibited a significant decrease since sunrise between 7:00~8:00 in the morning. mass concentrations of these air pollutants reached the lowest values and the highest temperature occurred from 14:00~15:00 at all the observation sites ( fig. 4a-d) . the pbl height is an important meteorological factor that affects the mixing, transport, accumulation and dilution of air pollutants tang et al., 2007) . there is usually negative feedback between the pbl height and particle concentrations (petäjä et al., 2016) , and a reduced pbl height is favorable for the accumulation of air pollutants in the weak turbulent diffusion conditions . the reduction rate of air pollutants by the elevation of the pbl height with an increase in temperature can be calculated via the mass concentration at sunrise (~8:00) divided by the difference between the mass concentration at sunrise (~8:00) and the minimum values at noon (12:00-14:00) (dashed line in fig. 4a-d) . based on this analysis, we can estimate the air quality impacted by the elevation of the pbl height in the daytime in the urban area, urban-industry area and suburban j o u r n a l p r e -p r o o f journal pre-proof area: a reduction of 47%, 41%, and 41%, respectively, for pm 2.5-10 ; a reduction of 8%, 20%, and 27%, respectively, for pm 2.5 ; a reduction of 42%, 42%, and 41%, respectively, for no x ; and a reduction of 18%, 20% and 16%, respectively, for co ( fig. 4e) . overall, the daytime elevation of the pbl height can dilute approximately ~30% of pm 2.5-10 , pm 2.5 , no x and co concentrations on the ground in hangzhou. however, we observed the opposite diurnal trends of so 2 and o 3 in hangzhou ( fig. s4) , and a similar diurnal pattern has been observed in hangzhou by ji et al. (2018) . the reason for these trends should be that power plants, as the major contributors of so 2 emissions, mainly operated during the daytime for the electricity consumption of household and industrial activities. o 3 formation mainly occurred in the daytime due to the photochemical cycle in the atmosphere (xue et al., 2014) . consequently in this study, a total of six transport events from the cwt analysis were identified during the observation period: two northern long-range transport events during the pre-covid period (event 1: 1/12 13:00 to 1/15 14:00, event 2: 1/20 15:00 to 1/22 marked reductions of pm 2.5-10 , pm 2.5 , no x , so 2 and co were observed in hangzhou during the covid-lock period, with an average reduction of 58%, 47%, 83%, 11% and 30%, respectively. conversely, o 3 increased more than 1 time with the lockdown of traffic and industry. the response of air pollutants to the lockdown actions was more significant in the urban and urban-industry areas, where traffic and industry were the major sources of air pollutants. no x was the most sensitive air pollutant in response to the reduction in the traffic and industry emissions. the pbl exhibited a more obvious dilution effect for the particle pollutants in the suburban area. we present an approximate calculation that transport contributes 40%-90% of fine particles in the urban area of hangzhou during the long-range transport events. based on the three-month continuous observations, this study can serve as a general reference for future air pollution control. cooperative control of aerosol particles, no x and ozone will be an important issue for air quality improvement. it is important to strengthen the coordinated interregional control to reduce the transport effects. the authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. impact of coronavirus outbreak on no 2 pollution assessed 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particulate matter in hangzhou, china exploring wintertime regional haze in northeast china: role of coal and biomass burning no x emission reduction and recovery during covid-19 in east china effects of meteorological conditions and air pollution on covid-19 transmission: evidence from 219 chinese cities the authors are grateful to ms. jiani xu and ms. yating bao for their assistance with data collection. this work was supported by the zhejiang provincial natural science key: cord-338243-njkhwkwk authors: zhang, dayi; ling, haibo; huang, xia; li, jing; li, weiwei; yi, chuan; zhang, ting; jiang, yongzhong; he, yuning; deng, songqiang; zhang, xian; wang, xinzi; liu, yi; li, guanghe; qu, jiuhui title: potential spreading risks and disinfection challenges of medical wastewater by the presence of severe acute respiratory syndrome coronavirus 2 (sars-cov-2) viral rna in septic tanks of fangcang hospital date: 2020-06-23 journal: sci total environ doi: 10.1016/j.scitotenv.2020.140445 sha: doc_id: 338243 cord_uid: njkhwkwk abstract the outbreak of coronavirus infectious disease-2019 (covid-19) pneumonia raises the concerns of effective deactivation of the severe acute respiratory syndrome coronavirus 2 (sars-cov-2) in medical wastewater by disinfectants. in this study, we evaluated the presence of sars-cov-2 viral rna in septic tanks of wuchang cabin hospital and found a striking high level of (0.5–18.7) × 103 copies/l after disinfection with sodium hypochlorite. embedded viruses in stool particles might be released in septic tanks, behaving as a secondary source of sars-cov-2 and potentially contributing to its spread through drainage pipelines. current recommended disinfection strategy (free chlorine ≥0.5 mg/l after at least 30 min suggested by world health organization; free chlorine above 6.5 mg/l after 1.5-h contact by china centers for disease control and prevention) needs to be reevaluated to completely remove sars-cov-2 viral rna in non-centralized disinfection system and effectively deactivate sars-cov-2. the effluents showed negative results for sars-cov-2 viral rna when overdosed with sodium hypochlorite but had high a level of disinfection by-product residuals, possessing significant ecological risks. the outbreak of coronavirus infectious disease-2019 (covid-19) pneumonia since 2019 is caused by the severe acute respiratory syndrome coronavirus 2 (sars-cov-2) (lai et al., 2020; li et al., 2020; ralph et al., 2020) , and it has rapidly spread throughout 202 countries around the world. till 20 th june 2020, there are over 8.0 million confirmed cases and around 450,000 deaths globally, and the number is still increasing rapidly (who, 2020a) . there is clear evidence of human-to-human transmission of sars-cov-2 (chan et al., 2020; chang et al., 2020; li et al., 2020; poon and peiris, 2020) . besides direct contact and respiratory routes (carlos et al., 2020; lai et al., 2020; wu et al., 2020) , stool transmission might be an alternative route owing to the survival of sars-cov-2 in patient's stools (holshue et al., 2020; ling et al., 2020; tian et al., 2020; xiao et al., 2020; xing et al., 2020; zhang et al., 2020c) . as municipal wastewater pipe network receives huge amounts of wastewater from asymptomatic patients and treated sewage from hospitals, sars-cov-2 from non-or inefficient-disinfected wastewater might persist for a prolonged time in pipe network, becoming a secondary spreading source (zhang et al., 2020a) . it brings urgent requirement and careful consideration of disinfection strategies to prevent sars-cov-2 from entering drainage pipe network. disinfection is of great importance to eliminate or deactivate pathogenic microorganisms. traditional disinfection strategies include ultraviolet germicidal irradiation and biocidal agents, e.g., gaseous ozone, alcohol, formaldehyde, hydrogen peroxide, peroxyacetic acid, povidone iodine and chlorine-based disinfectant (kampf et al., 2020; tseng and li, 2008; tseng and li, 2007; walker and ko, 2007) . some disinfectants are intensively used in hospitals for nurse personal care (dumas et al., 2019; ioannou et al., 2017) . among them, chlorine-based disinfectants are widely j o u r n a l p r e -p r o o f used for their broad sterilization spectrum, high inactivation efficiency, low price, and easy decomposition with little residue (how et al., 2017) . nevertheless, overuse of chlorine-based disinfectants brings concerns of disinfection by-products (dbps) which are harmful to ecosystems and human health (bull et al., 2011; richardson et al., 2007; wang et al., 2014) . more than 600 kinds of dbps have been observed (richardson, 2011) , such as trihalomethanes (thms), haloacetic acids (haas), halogen acetonitriles (hans), halonitromethanes (hnms) and haloacetamides (hacams) (ding et al., 2020; kozari et al., 2020; luo et al., 2020; zhai et al., 2014) . some of them are reported attributable for bladder cancer (evlampidou et al., 2020; li and mitch, 2018) and adverse reproductive outcomes (nieuwenhuijsen et al., 2000) . for effective centralized disinfection, world health organization (who) has suggested free chlorine ≥ 0.5 mg/l after at least 30 minutes of contact time at ph<8.0 (who, 2020b). additionally, china has launched a guideline for emergency treatment of medical sewage containing sars-cov-2 on 1 st february 2020, requiring free chlorine of ≥ 6.5 mg/l and contact time of ≥1.5 hour in disinfection units (china-mee, 2020) . unfortunately, the performance of chlorine-based disinfectants on sars-cov-2 in real medical wastewater treatment system is not clear yet. in this work, we studied the presence of sars-cov-2 viral rna in septic tanks of wuchang cabin hospital (wuhan, china) to evaluate the disinfection performance and optimize disinfection strategies to prevent sars-cov-2 from spreading through drainage pipelines. further analysis of dbps evaluated the potential ecological risks in the effluents. j o u r n a l p r e -p r o o f wuchang cabin hospital was a temporary hospital designated for covid-19 patients, formerly wuchang stadium located in wuhan (longitude, e114°20'05''; latitude, n30°32'46'') . it was open from 5 th february as the first cabin hospital in wuhan and closed on 10 th march, in total receiving 1,124 covid-19 patients ( figure 1 ). it had eight separate toilets and all sewage from toilets and showers were combined, with daily volume of wastewater ranging from 60 to 200 m 3 . the wastewater was firstly pumped from toilets and showers into the first preliminary disinfection tank, and sodium hypochlorite was unregularly added to a final concentration of 800 g/m 3 when it was 90% full. afterwards, the first preliminary disinfection tank was temporarily enclosed and the wastewater was then pumped into another disinfection tank and disinfected in the same way. on each day, septic tanks outside the hospital were emptied at 8 am to discharge the effluents into pipe network and wastewater treatment plants and received wastewater from preliminary tanks at 10 am. sodium hypochlorite was supplemented for 1.5 hr contact and the mixing was conducted by continuous pumping and stirring. wastewater was then pumped into three septic tanks. before march 5 th , the dosage of sodium hypochlorite in septic tanks was 800 g/m 3 and it increased to 6700 g/m 3 after 5 th march to secure complete deactivation of sars-cov-2. influent and effluent samples were collected from septic tanks of wuchang cabin hospital on 26 th february, 1 st march and 10 th march, 2020 (table 1) . on these sampling days, the number of covid-19 patients in wuchang cabin hospital was j o u r n a l p r e -p r o o f stable, ranging from 200 to 400. around 2.0 l of water was directly collected in a plexiglass sampler and transferred into a sterile plastic bag for biological analysis and a brown glass bottle for dbps analysis. as we found obvious settlement of stool particles and suspended solids in septic tanks, a stratified plexiglass sampler was used to obtain samples from different layers of septic tanks to assess the levels of viruses and dbps along depth, designated as top-layer (0-50 cm) and bottom-layer (50-100 cm) water. free chlorine was measured on site using pcii58700-00 (hach, usa). dbps measurements were carried out on a gcms-qp2020 (shimadzu, japan) equipped with atomx purge, trap autosampler (teledyne tekmar, usa) and an sh-rtx-5ms [(5%)-phenyl-(95%)-methylpolysiloxane] fused silica capillary column (30 m × 0.25 mm, 0.25 μm film thickness). the autosampler operating conditions were as follows: purge for 11 min at 30 °c with high-purity nitrogen gas at a flow rate of 40 ml/min, dry purge for 1.0 min at 20 °c with the flow rate of 40 ml/min, pre-desorption at 180 °c and desorption for 2.0 min at 190 °c, and bake for 6.0 min at 200 °c. collected water samples were placed in 4 °c ice-boxes and immediately transferred into laboratory for rna extraction. after centrifugation at 3,000 rpm to remove suspended solids, the supernatant was subsequently supplemented with nacl (0.3 mol/l) and peg-6000 (10%), settled overnight at 4 °c, and centrifuged at 10,000 g for 30 minutes. viral rna in pellets was extracted using the ez1 virus mini kit one-way anova was used to compare the difference between samples and p-value less than 0.05 refers to significant difference. all data were presented in mean ± standard deviation (n=3). j o u r n a l p r e -p r o o f for all influents of septic tanks received from wuchang cabin hospital, there was no positive result for sars-cov-2 viral rna. on 26 th february and 1 st march, sars-cov-2 viral rna was (14.7±2.2)×10 3 and (7.5±2.8)×10 3 copies/l in the effluents of septic tanks, respectively (table 1) the absence of sars-cov-2 viral rna in the influents of septic tanks suggested that preliminary disinfection in wuchang cabin hospital was satisfactory to remove sars-cov-2 in aqueous phase after 1.5-hour contact. in septic tanks, disinfection achieved free chlorine > 6.5 mg/l for 1.5 hours when the dosage of sodium hypochlorite was 800 g/m 3 , meeting well with the guideline for emergency treatment of medical sewage containing sars-cov-2 suggested by china cdc. however, sars-cov-2 viral rna was surprisingly positive in the effluents after 12 hours when free chlorine declined to nondetectable. it might be explained by the release of embedded sars-cov-2 viral rna from stool particles in septic tanks. sars-cov-2 has been found in patients' stools in many previous studies (wu et al., 2020; xing et al., 2020) , which could escape from disinfection and slowly release into aqueous phase. suspended particles as small as 7 mm can protect viruses from uv exposure and dwindle their vulnerability to direct sunlight inactivation, and 0.3-mm sized particles can shield viruses from disinfection for their prolonged survival (templeton et al., 2005) . as stools are rich in organic compounds and form numerous suspended solids containing sars-cov-2, they are of high risk as the source releasing viruses in septic tanks. it is also evidenced by more sars-cov-2 rna copy numbers in upper-layer waters, explained by more stool residuals and suspended solids in the bottom of septic tanks absorbing sars-cov-2 from aquatic water. our results suggested that current recommended disinfection dosage could effectively remove aqueous sars-cov-2 viruses in wastewater containing limited suspended solids, like wastewater treatment plants (la rosa et al., 2020; zhang et al., 2020b) . but it might be not enough for embedded viruses in suspended solids and require higher level of chlorine-based disinfectant supplement. septic tanks can behave as a long-term source j o u r n a l p r e -p r o o f to release sars-cov-2 viral rna into waters when disinfection is not sufficient and challenges public health via potentially spreading viruses in drainage pipelines. the surprising presence of sars-cov-2 viral rna after disinfection with sodium hypochlorite suggested that free chlorine > 0.5 mg/l after 1.5-hour contact time cannot completely removing sars-cov-2 viral rna, and 800 g/m 3 dosage of sodium hypochlorite might be not enough to secure a complete disinfection of medical wastewaters, particularly for those from cabin, temporary or non-centralized hospitals containing huge amount of stool debris and suspended solids. from the negative results of sars-cov-2 viral rna (table 1) , the complete deactivation of sars-cov-2 was achieved when the dosage of sodium hypochlorite was 6700 g/m 3 . as the number of covid-19 patients were similar on the three sampling days, they produced similar wastewater discharge and viral load. the change of sars-cov-2 in effluents was therefore attributing to the increasing sodium hypochlorite supplement for disinfection. nevertheless, it was an over-dosage and resulted in a significant level of dbps in the effluents, which was about 15 times higher than other hospital wastewater (luo et al., 2020) . the four detected chloroform and trihalomethanes accounted to the majority of total dbps in wastewaters (furst et al., 2019) and their composition was similar as previous studies (luo et al., 2020; zhong et al., 2019) . they show high ecological risks and challenge the surrounding environment receiving disinfected medical wastewater, possessing threats to ecological system and human health (ding et al., 2020; li et al., 2019 give initial information about the potential risks of viral spread and dbps residues during disinfection processes for medical wastewater containing sars-cov-2. our study for the first time reported an unexpected presence of sars-cov-2 viral rna in septic tanks after disinfection with 800 g/m 3 of sodium hypochlorite and current disinfection guideline by who and china cdc might not secure a complete removal of sars-cov-2 in medical wastewater. sars-cov-2 might be embedded in patient's stools, protected by organic matters from disinfection, and slowly release when free chlorine declines. septic tanks in non-centralized disinfection system of journal pre-proof j o u r n a l p r e -p r o o f cabin hospitals or isolation points potentially behave as a secondary source spreading sars-cov-2 in drainage pipelines for a prolonged time. disinfection strategy is of great urgency to improve and the ecological risks of dbps need to be carefully considered. j o u r n a l p r e -p r o o f potential carcinogenic hazards of non-regulated disinfection by-products: haloquinones, halo-cyclopentene and cyclohexene derivatives, n-halamines, halonitriles, and heterocyclic amines novel wuhan (2019-ncov) coronavirus a familial cluster of pneumonia associated with the 2019 novel coronavirus indicating person-to-person transmission: a study of a family cluster epidemiologic and clinical characteristics of novel coronavirus infections involving 13 patients outside wuhan, china technical solution for emergency treatment of medical sewage contaminated by novel coronavirus developmental toxicity of disinfection by-product monohaloacetamides in embryo-larval stage of zebrafish association of occupational exposure to disinfectants with incidence of chronic obstructive pulmonary disease among us female nurses trihalomethanes in drinking water and bladder cancer burden in the european union disinfection byproducts in rajasthan, india: are trihalomethanes a sufficient indicator of disinfection byproduct exposure in low-income countries? first case of 2019 novel coronavirus in the united states organic chloramines in chlorine-based disinfected water systems: a critical review biomarkers of end of shift exposure to disinfection byproducts in nurses persistence of coronaviruses on inanimate surfaces and their inactivation with biocidal agents formation potential of emerging disinfection by-products during ozonation and chlorination of sewage effluents coronavirus in water environments: occurrence, persistence and concentration methods -a scoping review severe acute respiratory syndrome coronavirus 2 (sars-cov-2) and coronavirus disease-2019 (covid-19): the epidemic and the challenges early transmission dynamics in wuhan, china, of novel coronavirus-infected pneumonia drinking water disinfection byproducts (dbps) and human health effects: multidisciplinary challenges and opportunities occurrence and ecological risk assessment of disinfection byproducts from chlorination of wastewater effluents in east china persistence and clearance of viral rna in 2019 novel coronavirus disease rehabilitation patients disinfection by-products formation and acute toxicity variation of hospital wastewater under different disinfection processes chlorination disinfection byproducts in water and their association with adverse reproductive outcomes: a review emergence of a novel human coronavirus threatening human health 2019-ncov (wuhan virus), a novel coronavirus: human-to-human transmission, travel-related cases, and vaccine readiness disinfection by-products: formation and occurrence in drinking water. encyclopedia of environmental health occurrence, genotoxicity, and carcinogenicity of regulated and emerging disinfection by-products in drinking water: a review and roadmap for research inactivation of particle-associated viral surrogates by ultraviolet light review article: gastrointestinal features in covid-19 and the possibility of faecal transmission inactivation of surface viruses by gaseous ozone inactivation of viruses on surfaces by ultraviolet germicidal irradiation effect of ultraviolet germicidal irradiation on viral aerosols disinfection technology of hospital wastes and wastewater: suggestions for disinfection strategy during coronavirus disease 2019 (covid-19) pandemic in china analytical and toxicity characterization of halo-hydroxyl-benzoquinones as stable halobenzoquinone disinfection byproducts in treated water covid-19) situation report, 2020a. who. water, sanitation, hygiene and waste management for covid-19: technical brief clinical characteristics of imported cases of covid-19 in jiangsu province: a multicenter descriptive study evidence for gastrointestinal infection of sars-cov-2 prolonged presence of sars-cov-2 in feces of pediatric patients during the convalescent phase formation of brominated disinfection byproducts during chloramination of drinking water: new polar species and overall kinetics sars-cov-2 spillover into hospital outdoor environments ultra-fast and onsite interrogation of severe acute respiratory syndrome coronavirus 2 (sars-cov-2) in environmental specimens via surface enhanced raman scattering (sers) fecal specimen diagnosis 2019 novel coronavirus-infected pneumonia disinfection byproducts and their toxicity in wastewater effluents treated by the mixing oxidant of clo2/cl-2 key: cord-285725-gge8ri93 authors: burdsall, adam c.; xing, yun; cooper, casey w.; harper, willie f. title: bioaerosol emissions from activated sludge basins: characterization, release, and attenuation date: 2020-08-20 journal: sci total environ doi: 10.1016/j.scitotenv.2020.141852 sha: doc_id: 285725 cord_uid: gge8ri93 abstract this article presents a critical review of the peer-reviewed literature related to bioaerosol generation from activated sludge basins. characterization techniques include a variety of cultureand nonculture-based techniques, each with unique features. bioaerosols contain a variety of clinical pathogens including staphylococcus saprophyticus, clostridium perfringens, and salmonella enteritidis; exposure to these microorganisms increases human health risks. release mechanisms involve splashing and bubble burst dynamics. larger bubbles emit more aerosol particles than smaller ones. attenuation strategies include covering sources with lids, adjusting the method and intensity of aeration, and using free-floating carrier media. future studies should combine culture and non-culture based methods, and expand chemical databases and spectral libraries in order to realize the full power of real-time online monitoring. samples of bacteria and fungi lasting up to several hours (lin et al., 1999) . the bioaerosol samples are eventually transferred onto plates or dissolved into a liquid solution for further microscopic examination, culturing experiments or non-cultured analysis such as pcr analysis. efficiency of collection is dependent on the type of sampling method, materials of the sampler, operation parameters of the sampling devices and the microbial species (kim et al., 2018) . 2.2.1. culture-based techniques. culture-based techniques are the most well-established and readily available for bioaerosol assessment. it is also a very sensitive technique and many different species can be identified without the need for specific biomarkers or primers. culturable bioaerosols are normally sampled by using impactors (microorganisms are collected directly on a culture medium), liquid impinger (microorganisms are collected in liquid collection fluid) or air filtration methods (microorganisms are collected on a filter). the collected bioaerosols are then transferred to the lab and grown on petri dishes with a chosen media (e.g. lb, nutrient agar for bacteria; sabouraud dextrose agar for fungi) for a few days (yazdanbakhsh et al., 2020) . colonies can be counted manually or with the aid of image analysis techniques. additionally, selective culture mediums are available to allow for the culture, identification, and quantification of a species of interest while inhibiting the growth of other microorganisms (aithinne et al., 2018; hustá et al., 2020) . culture-based techniques only measure the cultivable microorganisms and tend to underestimate the bioaerosol concentration due to several reasons that may cause viability loss. these factors include bioaerosol drying out in filtration-based sampling, atmospheric temperature, relative humidity, exposure to uv radiation (douglas et al., 2017) . cellular aggregation can also cause large variations in culture-based data. currently the most popular non-culture-based method is the polymerase chain reaction (pcr) method which detect and identify microorganisms and viruses by dna or rna sequence comparison. a genetic sequence representing a specific microorganism is first targeted j o u r n a l p r e -p r o o f journal pre-proof by a carefully designed dna primer, then amplified, quantified, and sequenced. the resulting sequences can then be analyzed directly and compared with existing public databases for identification and quantification. bioaerosol samples are first eluted from the collection device and concentrated; dna material is then extracted and purified for subsequent pcr analysis. the pcr method detects both culturable and nonculturable microorganisms, thus circumventing the limitations imposed by culturedbased techniques. indeed, this method can be applied to any biological matter that contains nucleic acids and has been successfully applied to bioaerosols collected through a variety of sampling techniques (peccia and hernandez, 2006) . modern pcr-based methods also provide results more rapidly than culturing techniques-on the order of minutes as compared to days (wei et al., 2015) . the rapid developments in this technology have made it even more accurate, sensitive and also readily available to many laboratories. because this method does not differentiate nucleic acid material from dead versus living microorganisms or cell debris, pcr results tend to overestimate the infectivity of bioaerosols. live unculturable microorganisms and dead but morphologically intact microorganisms can be also quantified by fluorescence-based methods. non-culturable bioaerosols collected using air filtration or liquid impinger methods are transferred to the lab. there the microorganisms can be stained with a fluorophore (e.g. acridine orangesyto9, dapi) that binds with nucleic acid, and counted with an epifluorescence microscope or flow cytometry. using a combination of fluorescent dyes such as the live/dead baclight assay, both live and dead microorganisms can be visualized and enumerated. specific identification and quantification of a certain bacteria species is also possible with the use of fluorescentlylabeled nucleic acid probes to target rrna within morphologically intact cells. the main advantage of these methods is that all microorganisms (i.e. culturable and unculturable, dead and living) are quantified. the estimated bioaerosol concentration is therefore often higher than values determined using culturebased methods (pepper et al., 2015) . apart from whole microorganisms, bioaerosols also contain toxic or allergenic microbial byproducts that cannot be quantified by nucleic acid-based methods. the most common method for the detection of this j o u r n a l p r e -p r o o f journal pre-proof type of bioaerosol is enzyme-linked immunoassays (elisa). toxin/allergen bioaerosol samples are first immobilized to a solid surface, a detection antibody which recognizes a specific antigen on the toxin/allergen is then added. the detection antibody can be either directly linked to an enzyme or detected by a secondary antibody which is linked to an enzyme. when a substrate of the enzyme is added to the mixture, it produces a signal (e.g. chemiluminescence, fluorescence, absorbance) that correlates with the quantity of the antigen in the bioaerosol sample. elisa assays have also been developed to detect and quantify microbial pathogens by detecting the antigens on the microbial surface. successful applications include detection of bacterial spores (stratis-cullum et al., 2003) , e.coli (korzeniewska and harnisz, 2012) , and mite allergen (miyajima et al., 2014) . the advantages of elisa are its specificity and adaptability to direct field use; the disadvantage is that a good antibody is often required, which is not always available. 3.1. the aeration basin. the aeration basin is a central feature in modern wastewater treatment process trains. the purpose of the aeration basin is to remove biodegradable wastewater constituents, primarily organic compounds and nitrogen. large populations of prokaryotic and eukaryotic species are cultivated in the aeration basin by controlling ph, proper mixing, and providing oxygen as a terminal electron acceptor. aeration is achieved with diffused aeration or mechanical mixing (e.g. surface aeration). the intense mixing and turbulence creates bioaerosol emission. numerous studies have documented bioaerosol emission from aeration basins (bauer et al., 2002; brandi et al., 2000; filipkowska et al., 2000; han et al., 2019) . previous studies have used culture-dependent and cultureindependent methods to identify the microorganisms present in bioaerosols emitted from aeration basins (table 1 ). the primary focus of the culture-dependent work was the identification of known clinical pathogens including intestinal microorganisms (e.g. enterococci sp., enterobacter sp.) and bacteria that j o u r n a l p r e -p r o o f journal pre-proof inhabit mucous membranes (e.g. staphylococcus sp.). therefore, exposure to bioaerosols emitted from aeration basins create human health risks. korzeniewska et al., 2009 also detected fungi, which are resilient in bioaerosols because of their ability to survive desiccation stress (pepper et al., 2015) . the culture-independent bioaerosol work of gaviria-figueroa et al., 2019 revealed the presence of a variety of microorganisms that have functional significance in the wastewater treatment process. for example, candidatus accumulibacter is responsible for phosphorus removal (metcalf and eddy, 2003) . nitrospira is responsible for the oxidation of nitrite, a necessary step in the nitrification process (metcalf and eddy, 2003) . gaviria-figueroa et al., 2019 also detected antibiotic resistance gene-carrying organisms in bioaerosols. prolonged viability is a concern for bioaerosols released from aeration basins. activated sludge microorganisms grow within flocculent aggregates, consisting of extracellular polymeric substances (eps), inert particles, water, and numerous ionized chemicals (metcalf and eddy, 2003 the bubble then bursts when the membrane can no longer maintain the internal pressure of the bubble ( figure 1a) . as a bubble dissolves, the liquid remaining in the membrane splits into strands of liquid that j o u r n a l p r e -p r o o f journal pre-proof then break into small droplets a few microseconds later ( figure 1b ). if the bubble is only a few millimeters in diameter, a jet may form as water rushes to fill the void space created by the bubble on the surface ( figure 1c ). however, in larger bubbles, there is some confusion about the conditions that form jets; ke et al. (2017) indicated that this jet does not form above a diameter of 3.4 mm, so that the only source of aerosols is from the droplets formed from the membrane during bursting. lee et al. (2011) described jetting in the bursting of bubbles with a radius length much greater than 100 µm, but it is not quite clear whether those larger bubbles were as large as the ones examined in ke et al. (2017) . bursting bubbles release pollutants and ions into the atmosphere (hardy, 1982) . microorganisms accumulate in the interface that separates the bulk liquid from the atmosphere (hermansson and dahlbäck 1983; schäfer et al., 1998) . numerous studies have shown that bursting bubbles aerosolize the microorganisms present in the air-water interface (aller et al., 2005; baylor et al., 1977, blanchard and syzdek, 1970; filipkowska et al., 2000) . larger bubbles emit more and larger aerosol particles than smaller ones (ke et al., 2017) . with horizontal rotating brushes (figure 2 ). droplets of various sizes are ejected from the water into the air off of the discs in all directions ((1) in figure 2 ). many of these droplets may be too large to become aerosols and will simply fall back into the water. however, droplets < 7 µm in diameter can be carried on moving air currents and are small enough to be deposited in the respiratory system during normal respiration (donnison et al., 2004) . foams and bubbles are commonly observed near the rotating discs on the water surface ((2) in figure 2 ). bioaerosols are released as these bubbles pop on the surface and by the splashing that occurs when droplets land on the water surface ((3) in figure 2 , fracchia et al., 2006; li et al., 2013; sánchez-monedero et al., 2008) . bubbles form from the splashing of water caused by the rotation of the brushes ((4) in figure 2 ) and from the forcing of air down into the water column. splashing and bubble bursting occur with other methods of mechanical surface aeration (e.g. subsurface turbines, fountains, horizontal paddles), but peer-reviewed studies have not yet revealed the bioaerosol release mechanisms for these processes. horizontal mixing rotors were found to produce higher aerosol 4.1 covering sources. aeration basins can be covered with light-weight materials which can be periodically cleaned or replaced. this approach is now commonly done for odor control (metcalf and eddy, 2003) . hinged lids have been used to cover bioaerosol sources at a full-scale treatment facility (fernando and fedorak, 2005) . other studies have recommended covering sources to reduce bioaerosol emissions (fathi et al., 2017; kummer and thiel, 2008) or designing facilities so that sewage is not exposed to open air (o'hara and rubin, 2005) . the results in fernando and fedorak (2005) indicated that a floating cover apparently does not affect oxygen transfer for diffused aeration, but there may be a marginal reduction in oxygen transfer efficiency and energy efficiency (ashley et al., 1992) . covers may also have small openings to allow for airflow out of the basin during aeration (fernando and fedorak, 2005) , which may permit bioaerosol release. however, these hinged coverings may not be practical for certain mechanically-aerated systems. since the mechanical aeration methods are designed to introduce open air into the wastewater, oxygen flow may be restricted when the basin is covered, resulting in a drop in the aeration efficiency of the rotors. bioaerosol emissions from activated sludge basins are dependent upon the aeration method, which in turn influences mixing. switching from surface aeration to fine bubble diffused aeration appears to reduce bioaerosol production (bauer et al., 2002; brandi et al., 2000; fathi et al., 2017; han et al., 2019; sánchez-monedero, 2008) . fernando and fedorak, 2005 showed that changing from coarse bubble to fine bubble aeration decreased the bioaerosol concentrations from 1000 and 1800 cfu/m 3 to 24 and 37 cfu/m 3 and two locations near the aeration basins. changing from coarse bubble aeration to fine bubble aeration is a promising strategy for attenuating bioaerosol release. this option also has the additional benefit of improving oxygen transfer efficiency j o u r n a l p r e -p r o o f journal pre-proof (metcalf and eddy, 2003) . however, the conversion may require a redesign of the apparatus delivering the air to the basins. characteristics of the bioaerosols produced by these methods must also be considered. although horizontal rotors exert stronger shear forces that produce more total bioaerosols, the size of those particles is predominantly greater than 7.0 µm (han et al., 2020) . meanwhile, fine bubble aeration mainly produces smaller, respirable aerosols (han et al., 2020) . another strategy is the use of free-floating carrier media (ffcm), which consists of low-density materials that could be placed on the water surface to stop bioaerosol release. bourke, 1999 and sheehy et al., 1984 described using plastic or polystyrene beads as ffcm to prevent mists from being released from electroplating tanks. shredded foam has also been used because it may interlock better than sphere-shaped media (bourke, 1999). hung et al. (2010) used polystyrene spheres in a laboratory-scale bioreactor, and they found that the emission reduction increased as the sphere size (i.e. 1.9, 2.9, 3.4, 4.8 cm) decreased. they also showed that using multiple bead layers may provide a modest improvement in capture efficiency. for both the electroplating and sewage aeration experiments, free floating carrier media was effective at removing or preventing the release of most aerosol particles up to around 90% (hung et al., 2010; sheehy et al., 1984) . noh et al., 2019 found that the introduction of powdered activated carbon (pac) in a membrane bioreactor increased the formation of bacterial flocs and decreased the amount of free bacteria available to be aerosolized. no ffcm studies have been carried out at a full-scale wastewater treatment plant to the best knowledge of the authors. micro-environment characteristics and microbial communities in activated sludge flocs of different particle size bioaerosols emission and exposure risk of a wastewater treatment plant with a 2 o treatment process effect of aeration mode on aerosol characteristics from the same wastewater treatment plant the sea surface microlayer: biology, chemistry and anthropogenic enrichment airborne enteric coliphages and bacteria in sewage treatment plants bacterial activity at the air/water interface aerosol technology: properties, behavior, and measurement of airborne particles use of floating balls for reducing bacterial aerosol emissions from aeration in wastewater treatment processes a comparative study on the use of selective media for the enumeration of clostridium perfringens in poultry faeces. anaerobe, 102205. wastewater-based epidemiology? wastewater engineering treatment and reuse, fourth edition direct analysis of airborne mite allergen (der f1) in the residential atmosphere by chemifluorescent immunoassay using bioaerosol sampler soluble microbial products and their implications in mixed culture biotechnology reducing bacterial aerosol emissions from membrane bioreactors: the impact of srt and the addition of pac and calcium reducing bioaerosol dispersion from wastewater treatment and its land application: a review and analysis bioaerosol emission from wastewater treatment plants incorporating polymerase chain reaction-based identification, population characterization, and quantification of microorganisms into aerosol science: a review environmental microbiology icc/pcr detection of enteroviruses and hepatitis a virus in environmental samples integrated cell culture/pcr for detection of enteric viruses in environmental samples effect of the aeration system j o u r n a l p r e -p r o o f journal pre-proof on the levels of airborne microorganisms generated at wastewater treatment plants bacterial accumulation at the air−water interface control technology assessment: metal plating and cleaning operations the characteristics of biocl/plaster of paris composites and their photocatalytic performance under visible light illumination for self-cleaning a miniature biochip system for detection of aerosolized bacillus globigii spores inactivation of particle-associated viral surrogates by ultraviolet light real time detection and characterization of bioaerosol emissions from wastewater treatment plants antimicrobial surfaces with self-cleaning properties functionalized by photocatalytic zno electrosprayed coatings composition and functional group characterization of extracellular polymeric substances (eps) in activated sludge: the impacts of sciences characterization and source analysis of indoor/outdoor culturable airborne bacteria in a municipal wastewater treatment plant aerosols from a wastewater treatment plant using oxidation ditch process: characteristics, source apportionment, and exposure risks data on airborne bacteria and fungi emission from a conventional hospital wastewater treatment plant strength and breakage of activated sludge flocs p r e -p r o o f reference identification (i.e. order, family, genus, or species) or description method brandi et al., 2000* enterococci sp., escherichia coli, staphylococci sp.; total bacteria culture-selective media * shigella spp., yersinia enterocolitica, escherichia coli, klebsiella pneumoniae ozaenae, staphylococcus sp., pseudomonas sp., actinomycetes sp enterobacter sp; bacillus sp., acinetobacter sp., lysinibacillus culture-selective media clostridium perfringens, staphylococcus aureus, enterococcus spp. culture-selective media salmonella enteritidis, salmonella boydii, reovirus, enterovirus culture-selective media alphaproteobacteria: rhodobacter nitrospirae: nitrospira 16s rrna gene sequencing and cultureselective media * mesophilic bacteria, tsa-sb bacteria culture-selective media chryseobacterium sp., stenotrophomonas sp., alcaligenes sp., micrococcus sp., pantoea sp., enterobacter sp ** salmonella sp., total viable bacteria culture-selective media and pcr enterobacteriaceae sp key: cord-300739-ll1kc7sn authors: kerimray, aiymgul; baimatova, nassiba; ibragimova, olga p.; bukenov, bauyrzhan; kenessov, bulat; plotitsyn, pavel; karaca, ferhat title: assessing air quality changes in large cities during covid-19 lockdowns: the impacts of traffic-free urban conditions in almaty, kazakhstan date: 2020-05-04 journal: sci total environ doi: 10.1016/j.scitotenv.2020.139179 sha: doc_id: 300739 cord_uid: ll1kc7sn abstract number of cities worlwide experienced air quality improvements during covid-19 lockdowns; however, such changes may have been different in places with major contributions from nontraffic related sources. in almaty, a city-scale quarantine came into force on march 19, 2020, which was a week after the first covid-19 case was registered in kazakhstan. this study aims to analyze the effect of the lockdown from march 19 to april 14, 2020 (27 days), on the concentrations of air pollutants in almaty. daily concentrations of pm2.5, no2, so2, co, o3, and btex were compared between the periods before and during the lockdown. during the lockdown, the pm2.5 concentration was reduced by 21% with spatial variations of 6–34% compared to the average on the same days in 2018–2019, and still, it exceeded who daily limit values for 18 days. there were also substantial reductions in co and no2 concentrations by 49% and 35%, respectively, but an increase in o3 levels by 15% compared to the prior 17 days before the lockdown. the concentrations of benzene and toluene were 2–3 times higher than those during in the same seasons of 2015–2019. the temporal reductions may not be directly attributed to the lockdown due to favorable meteorological variations during the period, but the spatial effects of the quarantine on the pollution levels are evidenced. the results demonstrate the impact of traffic on the complex nature of air pollution in almaty, which is substantially contributed by various nontraffic related sources, mainly coal-fired combined heat and power plants and household heating systems, as well as possible small irregular sources such as garbage burning and bathhouses. j o u r n a l p r e -p r o o f 3 quarantine) were identified using satellite data from nasa and the european space agency (esa) (earth observatory, 2020) . (tobías et al., 2020) also depicted substantial air quality improvements after two weeks of lockdown in barcelona (spain) . the results support the idea that air pollution could be substantially improved in cities where transport was a major source. however, the air quality improvements during covid-19 lockdowns may not clearly favor improving the air quality in areas with a more complex mix of sources, where transport emissions have minor impacts compared to emissions from other sources (e.g., coal combustion for power and heating). concerning the levels of btex, almaty is among the most polluted cities in the world (carlsen et al., 2018) . in terms of priority pollutants, it is one of the most polluted cities of kazakhstan (kerimray et al., 2019) , and there were 21 days in 2018 on which the pm 2.5 concentrations exceeded 250 µg m -3 at least at one station (kerimray et al., 2020) . the wintertime concentrations of major atmospheric air pollutants were several times higher than those during summertime, which could be explained by intensive coal combustion at power plants and in households for heating. two coal-fired combined heat and power plants named j o u r n a l p r e -p r o o f 4 scientists largely criticized it. in february 2020, more than 20000 citizens signed an online petition urging officials to acknowledge the coal-fired power plants as the main emitters in almaty (vlast, 2020) . the inappropriate identification of the inventory is caused not only by the lack of capacity and outdated methodologies but also by the scarcity of data and nontransparent energy statistics (kerimray et al., 2017) . since the data on fuel consumption and emissions are not publicly available, producing independent inventories of pollutants is a complicated task. source apportionment with chemical analysis of pm particles is needed; however, due to the scarcity of funding for expensive laboratory equipment and the lack of capacity, it has not been conducted so far. in this study, changes in the air quality before and during the period of covid-19 lockdown in almaty were quantified. the possible effects of traffic emissions were discussed. daily concentrations of pm 2.5 , no 2 , so 2 , co, and o 3 were compared between the periods before (e.g., during the preceding three weeks or the same days in earlier years) and during the lockdown. benzene, toluene, ethylbenzene, and o-xylene (btex) concentrations were also measured during three days in the middle of the lockdown and compared with the concentrations observed during the same periods of previous years (2015) (2016) (2017) (2018) (2019) . this study aims to assess the impacts of covid-19 lockdown conditions (traffic-free) on the air quality of almaty, which is one of the most polluted large cities in the world. in this study, daily pm 2.5 concentration levels were obtained from the "airkaz" public air j o u r n a l p r e -p r o o f 5 periods. none of the selected stations was located close to chp-2 since the station close to chp-2 did not record full data for march. pm 2.5 concentrations were compared between the lockdown period during march 19 to april 14, 2020, and the same period in previous years. additionally, the air quality was compared within 2020 between the periods before lockdown (february 21 -march 18) and during lockdown (march 19 -april 14). monitoring of benzene, toluene, ethylbenzene, and o-xylene (btex) was conducted every spring at 8 am and 8 pm at six different locations (https://goo.gl/maps/6uprmjjoypweg2d56) during the period from the end of march to the beginning of april from 2015 to 2020. the sampling and analysis methods developed by (baimatova et al., 2016) and (ibragimova et al., 2019) were followed. the lockdown btex sampling was conducted on three days in the middle of the lockdown. daily no 2 , o 3 , so 2 , and co concentration values for the period of march 2 -april 14, 2020, from one station (located in the city center) were obtained from the "skymax technologies" company. no 2 , o 3 , so 2 , and co concentration values were not available for the previous years. the wind speed, wind direction, temperature, relative humidity, precipitation were obtained from the http://rp5.kz website (weather schedule, 2020), which collects data from the national oceanic and atmospheric administration (usa) from the station located at 43.15°n, 76.57°e at an elevation of 848 m above sea level. the cokriging method utilized in the arcgis ® geostatistical analyst tool (https://desktop.arcgis.com/ru/arcmap/) was used to map pm 2.5 and benzene distributions across table 1 . the period between february 21 to april 14, 2020 was characterized by a substantial difference (23.3 °c) between the minimum daily temperature (-6 °c) and the maximum daily temperature (17.3 °c). the average temperature before lockdown was 5.5 °c, while it was 8.7 °c during lockdown. additionally, there were less frequent rains before lockdown period (9 days out of 27) compared to the lockdown period (16 days out of 27). these results show that the meteorological conditions were in favor of air pollution reductions during the lockdown period compared to the preceding days. on the other hand, the meteorological conditions during the lockdown were almost similar to those of the same periods in the previous years of 2018 and 2019 (table 1 ; fig. s1 , supplementary file). the numbers of rainy days were 15, 16, and 16 days, and the average temperatures were 11.2, 11.6, and 8.7 °c in 2018, 2019, and 2020, respectively. the lockdown period was slightly colder compared to previous years, as there were six days during the lockdown period when the daily average temperature was below 5 °c, while such temperature falls were observed only on one day in 2018 and two days in 2019. these results show that the lockdown period had slightly unfavorable meteorological conditions for air pollution compared to the earlier years. j o u r n a l p r e -p r o o f 7 3.1. impact of the lockdown on the pm 2.5 concentration the study under analysis (february to april) is a transitional period characterized by rising temperatures and subsequent declining coal combustion by private houses (heating purposes) and chps. for example, the monthly coal combustion at chp-2 shows significantly varying levels throughout the year (seasonality), with twice lower values in june compared to january and 8. this record needs further investigation to better understand whether the effect is from policies and measures will last over the years. one possible (alternative) explanation could be the slightly higher temperatures during the period of february 21 -march 18 in 2020 (5.5 °c) compared to previous years (4.6-4.7 °c). in this study, to exclude the "temperature effect" and "precipitation effect" and to explore only the effect of the lockdown, the concentrations during the same period (march 19 -april 14) of 2018, 2019, and 2020 were compared. the pm 2.5 concentrations (averaged for all stations) during the lockdown period were 38, 40, and 31 μg m -3 in 2018, 2019 and 2020, respectively, indicating a reduction of the pm 2.5 concentration by 18% and 23% in 2020 (during lockdown) compared to the same periods in 2018 and 2019 (before the lockdown year). fig. 1 shows that the trend of the daily pm 2.5 was fluctuating during the period of march-april in all three years, with no clear downward/upward trend between days or between years. the pm 2.5 concentration levels varied across the stations during the lockdown from 27 to 38 μg m -3 . the spatial reductions varied between 6% and 34% during the lockdown period compared to the other years (fig. 2, fig. 3 and fig. s2 , supplementary file), and this might be attributed to the removal of traffic emissions with their varying contributions to the spatial locations. almaty is located at an altitude between 600 m and 1300 m due to its proximity to the mountains. a previous study by (kerimray et al., 2020) depicted that the pm 2.5 concentration was correlated with the elevations of the monitoring stations (r 2 =0.64). in this study, pm 2.5 concentration levels during the 2020 lockdown did not have a correlation with the elevation (r 2 =0.23), distance to chp-2 (r 2 =0.1), or distance to chp-3 (r 2 =0.22) (fig. s2, supplementary file). a previous study by (kerimray et al., 2020) used data from 11 monitoring stations for j o u r n a l p r e -p r o o f 9 pm 2.5 , while in this study, data from only 7 stations was used (due to the absence of full datasets for march months in 2018-2020). however, the spatial model results shown in fig. 3 show that the spatial profiles have similarities-lower levels in the south and higher levels in the northbut their variation ranges are significantly different. the weak correlations with distance to chp-2 (r 2 =0.10) and chp-3 (r 2 =0.22) could be due to many contributing factors, including the long distance of the sampling sites from chp-2, several contributing sources of emissions located at different places, complicated topography, and varying wind directions. station 16 is the most polluted place and experienced the most significant reduction in the lockdown period from the average of 57 μg m -3 in 2018-2019 to 38 μg m -3 in 2020 (34% decline). station 16 is at the lowest elevation above sea level (647 m) compared to the locations of the other stations. this station is located at the border of almaty and administratively belongs to the almaty region; however, it was included in this study. station 16 is only 2.5 km away from the coal-fired chp-3 and is located near major roads. the impacts of traffic and chp-3 emissions are evident at this location (kerimray et al., 2020) . the high levels despite the absence of the traffic contribution (38 μg m -3 ) demonstrate that coal combustion (especially close location to chp-3) is the primary source impacting the station. station 5, on the other hand, which is located in the city center with high traffic and a lower elevation (793 m), experienced a j o u r n a l p r e -p r o o f 10 1348 m and is close to the mountains, and it is far away from the densely populated areas with high traffic loads. these results confirm that the city has experienced spatial pm 2.5 reductions during the lockdown period. the number of days exceeding the daily who limit (25 μg m -3 ) was 23, 25, and 18 days in 2018, 2019, and 2020, respectively (for the period of march 19 -april 14) (fig. 1) . the lockdown in 2020 has resulted in a 25% reduction in the number of days compared to 2018 and 2019. however, even with a traffic-free environment, who daily limit values in almaty were still not met on 18 out of 27 days of the lockdown. the average concentrations of btex analytes from 2015 to 2020 are illustrated in fig. 4 . the averages for benzene (101 µg m -3 ) and toluene (67 µg m -3 ) were 3 and 2 times higher, while those for ethylbenzene (1.0 µg m -3 ) and o-xylene (1.6 µg m -3 ) were 4 and 2.7 times lower in 2020 than during the same sampling period in 2015-2019 (table 3 ). in addition, the average concentration of benzene was 15% higher in january 2020 compared to the lockdown period. table 3 . the sampling period during the lockdown in april 2020 was characterized by warmer temperatures ranging from 10.2 to 16.2 °c, while the temperature ranged from -6.2 to 14.5 °c on the sampling days in 2015-2019 ( fig. s1 and table s1 one of the reasons for the increased concentrations of benzene and toluene during the sampling days in 2020 could be attributed to the no-precipitation conditions. since there was no traffic activity during the lockdown, the higher levels of benzene and toluene may indicate that their origins are predominantly nontraffic sources, and the declining levels of ethylbenzene and o-xylene by up to 3 fold could be linked to the traffic-free conditions. btex concentrations were inversely proportional to the elevation (above the sea level) of the sampling sites (fig. 5) which was similar to the case for pm 2.5 concentrations. at the higher elevations (closer to the mountains), the concentrations of btex were lower than those at the lower elevations (fig. 5) , and this could be explained by the location of the coal-fired power plants and households burning coal at the lower elevations. the btex concentrations in 2020 were inversely correlated with the distance to chp-3, with r 2 =0.87 for benzene and r 2 =0.82 for toluene. the distance-concentration correlations for chp-2 were weak (r 2 <0.1), which could be due to the large distances of sampling sites from chp-2 (fig. s4, supplementary file) . the correlation of the benzene and toluene concentrations with the distance from chp-3 was stronger than the correlation with the elevation (fig. 5) , and this may indicate the dominant contribution of chp-3 to btex pollution in the city. according to the environmental reports of chp-3 in 2015, coal consumption at chp-3 was expected to increase in the future due to the rising demand for electricity (department of ecology of almaty region, 2015). there were substantial increases in benzene and toluene during the lockdown period compared to the average during the 2015-2019 years, while some reductions were observed in ethylbenzene and o-xylene concentrations. the variations were significant and ranged between 123% and 227% for benzene and between 36% and 241% for toluene. the highest increases in the concentrations were observed at station s4, which were 274% (by 119 µg m -3 ) for benzene and 241% (by 86 µg m -3 ) for toluene (table 3) . station s4 is located at a low elevation (700 m), close to coal-burning housing developments and at the distances of 12 km from chp-2 (fig. s4 , supplemental materials) and 14 km from chp-3 (fig. 5 ). there is also an almaty bus fleet park located 2.6 km away, and the public bus service was still in operation during the lockdown. the burning of coal at residential houses could have been higher, as people remained in their homes all the time during the 2020 lockdown, and there are plenty of nearby public bathhouses (saunas) that are often heated by burning their garbage or coal. on one of the sampling days, a bonfire was also observed. relatively lower concentrations of benzene (76-78 µg m -3 ) and toluene (41-42 µg m -3 ) during the 2020 lockdown were observed at sites s1 (978 m) and s6 (803 m). sampling site s1 is located in the upper part of almaty (closer to the mountains), while site s6 is located in a public park at 803 m above sea level. sampling sites s3 (764 m) and s5 (770 m) are located near significant roads; however, the high levels of btex at sites s3 and s5 during the 2020 lockdown indicate the significant contribution from coal combustion. j o u r n a l p r e -p r o o f 13 that the primary source of btex is biomass, biofuel, or coal burning, while t/b > 1 indicates that it mainly originates from vehicle emissions (liu et al., 2015) . the varying t/b observed during 2015-2019 indicated the complex nature of btex in the ambient air of almaty (fig. 7) . in 2015, the obtained t/b ratios were <1 in 18 out of 36 measurements, indicating that sources of btex were both vehicle exhaust and coal combustion (baimatova et al., 2016) . the t/b found in most of the analyzed samples in 2016 (30 from 36 measurements) and 2018 (31 from 35 measurements) were ≥1, suggesting that btex mainly originated from transport-related sources. the t/b of the vast majority of collected samples in 2017 (33 from 36 measurements) and 2019 (23 from 35 measurements) were <1, which indicated that btex mainly originated from coal burning (ibragimova et al., 2019) . simple and accurate quantification of btex in ambient air by spme and gc-ms determination of aromatic hydrocarbons in urban air of rome use of partial order in environmental pollution studies demonstrated by urban btex air pollution in 20 major cities worldwide adjustment of the standards for maximum permissible emissions (mpe) in the atmospheric air for the department of jsc ales chp-2". department of ecology of almaty region low-cost quantitation of multiple volatile organic compounds in air using solid-phase microextraction 6 information bulletin on the state of the environment of the republic of kazakhstan trends and health impacts of major urban air pollutants in kazakhstan analysis of the energy intensity of kazakhstan: from data compilation to decomposition analysis letter to the public council of the city of almaty serious btex pollution in rural area of the north china plain during winter season ministry of environmental protection of republic of kazakhstan changes in air quality during the lockdown in barcelona (spain) one month into the sars-cov-2 epidemic more than 20 thousand signatures were collected by a petition for the recognition of polluted air as the main problem in almaty spatiotemporal patterns and source implications of aromatic hydrocarbons at six rural sites across china's developed coastal regions this work was supported by the postdoctoral fellowships of ak and nb provided by al-farabi kazakh national university. btex sampling and analysis were supported by the ministry of education and science of the republic of kazakhstan (grant no. ap05133158) and "airvision.kz" public fund. the authors are grateful to skymax technologies for providing data. no potential conflict of interest was reported by the authors. the authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. key: cord-322906-zef971xp authors: hochman, assaf; alpert, pinhas; negev, maya; abdeen, ziad; abdeen, abdul mohsen; pinto, joaquim g.; levine, hagai title: the relationship between cyclonic weather regimes and seasonal influenza over the eastern mediterranean date: 2020-08-12 journal: sci total environ doi: 10.1016/j.scitotenv.2020.141686 sha: doc_id: 322906 cord_uid: zef971xp abstract the prediction of the occurrence of infectious diseases is of crucial importance for public health, as clearly seen in the ongoing covid-19 pandemic. here, we analyze the relationship between the occurrence of a winter low-pressure weather regime cyprus lows and the seasonal influenza in the eastern mediterranean. we find that the weekly occurrence of cyprus lows is significantly correlated with clinical seasonal influenza in israel in recent years (r = 0.91; p < .05). this result remains robust when considering a complementary analysis based on google trends data for israel, the palestinian authority and jordan. the weekly occurrence of cyprus lows precedes the onset and maximum of influenza occurrence by about one to two weeks (r = 0.88; p < .05 for the maximum occurrence), and closely follows their timing in eight out of ten years (2008–2017). since weather regimes such as cyprus lows are more robustly predicted in weather and climate models than individual climate variables, we conclude that the weather regime approach can be used to develop tools for estimating the compatibility of the transmission environment for influenza occurrence in a warming world. furthermore, this approach may be applied to other regions and climate sensitive diseases. this study is a new cross-border inter-disciplinary regional collaboration for appropriate adaptation to climate change in the eastern mediterranean. the world health organization (who) has estimated that in 2012 approximately 12.6 million deaths (23% of all deaths worldwide) were attributed to changeable environmental factors, of which many could be potentially influenced by ongoing climate change (who 2016) . in addition, the lancet commission on health and climate change determined that "climate change could be the greatest public health threat of the 21 st century" (watts et al., 2015; . there is clear evidence that climate change in the last 50 years has affected human health, partly by altering the epidemiology of climate sensitive diseases (e.g., patz et al., 2005; mirsaeidi et al., 2016) . specifically, climate change leads to alterations in the mean, variability, seasonality and/or extremes in one or more climatic variables such as temperature, precipitation, humidity, aerosols etc. these changes influence the dispersal of pathogens, the transmission environment and the host's resilience (vittecoq et al., 2017) . health effects related to climate change tend to emerge as seasonal and geographical alterations in the spread of disease (wu et al., 2016; dennis and fischer 30% of the burden of infectious diseases in europe in the period 2009-2013 (cassini et al., 2018) . caini et al. (2018) analysed the timing of seasonal influenza maximum occurrence, showing that it was delayed by 2.8d/year in western europe from 1996 to 2016, while it was shortened by 3.5d/year in eastern europe. regarding israel, caini et al., (2018) identified a progressive delay of maximum incidence by 2.8d/year. the reasons for such changes have not yet been fully explained, but ongoing climate change is among the leading candidates. moreover, a recent study revealed intense inter-seasonal influenza activity during 2018/9 ( barr et al., 2019) , reinforcing the need for year-round surveillance of influenza, even in areas with strong seasonality patterns like the eastern mediterranean. a plethora of studies have indicated that the timing of seasonal influenza varies across latitude, thus suggesting that meteorological conditions play an important role in the transmission of the disease (soebiyanto et al., 2010; 2014; tang et al., 2010; baumgartner et al., 2012; shaman and karspeck 2012; yang et al., 2012; tamerius et al., 2013; yaari et al., 2013; chong et al., 2019) . a few studies have demonstrated that absolute humidity modulates the airborne survival and transmission of the influenza virus (shaman and kohn 2009; shaman et al., 2010; 2011) . soebiyanto et al. (2015) have investigated the association between climatic variables and seasonal influenza in temperate and sub-tropical regions, including israel. they have provided evidence that an increase in influenza activity is related to a decrease in temperature and specific humidity. recently, zhao et al. (2018) has shown that influenza specific combination of variables that leads to enhanced incidence of infectious diseases, e.g. low temperatures and rainy/moisty or dry conditions in the case of influenza (axelsen et al., 2014; guo et al., 2015; chong et al., 2020) . indeed, there is growing evidence that large scale climatic modulations such as the el-niño or la-niña may influence the onset and peak of seasonal influenza in many regions across the globe (oluwole 2015 (oluwole , 2017 chun et al., 2019) . in order to potentially predict the compatibility of the transmission environment for climate sensitive infectious diseases, it is necessary to obtain skilful predictions of several meteorological variables at the same time, as clearly shown in the current covid-19 pandemic (ma et al., 2020) . however, one caveat of using individual climatic variables is that seasonal, decadal and multi-decadal weather and climate forecast models struggle in predicting these variables individually, especially in regions distant from the onset of the el-niño (weisheimer and palmer 2014 ). however, model forecasts are generally more robust in predicting weather regimes occurrences and timing (weisheimer and palmer 2014; grams et al., 2017) . a weather regime can be considered as a capsule containing much of the information on the transmission environment, including the synergistic relations between individual climatic variables like temperature, precipitation, humidity and wind (lamb 1950; 1972; stein and alpert 1993; alpert and sholokhman, 2011; santos et al., 2016) . moreover, a weather regime approach also has the advantage of retaining the physical relationship between the individual climatic variables. south-eastern part of the eastern mediterranean region (alpert et al., 2004a) . the semi-objective synoptic classification describes well the local weather and has many implications (alpert et al., 2004a, b; saaroni et al., 2010a, b; hochman et al., 2018a, b; 2019a, b; 2020a, b) . for example, hochman et al. (2018b) have provided evidence that by the end of the 21 st century, the duration of the summer is projected to extend by 49% (+ ~ 60 days), while the winter is expected to be shortened by 56% (-~ 60 days) under the "business as usual" greenhouse gas scenario (rcp8.5). the authors (hochman et al., 2018b) concluded that these alterations may lead to substantial changes in the timing of seasonal health hazards including seasonal influenza. high-quality climatic and infectious disease information is sparse in some regions of the world, e.g., in several of the eastern mediterranean countries. in this respect, google trends is a freely accessible tool that may provide insights into population for this study, we set a cross-border inter-disciplinary regional collaboration, composed of climatologists, epidemiologists and public health professionals from the palestinian authority, israel and germany (hochman et al., 2020c) . the purpose of j o u r n a l p r e -p r o o f journal pre-proof this study is to investigate the potential link between weather regime occurrences and climate sensitive infectious diseases, and discuss in how far this relationship can help to inform decisions in the health sector. as a case study, the weekly occurrences of an eastern mediterranean weather regime -cyprus lows -together with precipitation, temperature and humidity, are related to seasonal influenza in israel, the palestinian authority and jordan. climatic data were acquired from the national centre for environmental prediction/national centre for atmospheric research (ncep/ncar) reanalysis archive (kalnay et al., 1996) . we the student t-test is used to check for statistical significance of the correlation coefficients at the 5% significance level. finally, we investigate the ability of the weather regime approach in depicting the onset and maximum occurrence of the influenza season. the onset (maximum) is defined as the first week of the season with above zero (one) normalized incidence rates or weekly occurrence of cyprus lows. it should be noted that all datasets are open access for reproducibility and transparency and the modeling framework was validated as recommended by walters et al. (2018) . data from the icdc weekly reports of positive specimens for influenza at the trends data (fig. 2 -4 ; table s1 ). the reason may be that the individual variables have a strong impact on human behavior, which the google trends tool was designed to detect (nuti et al., 2014) . in terms of seasonality, google trends estimates the onset of influenza at week 35 and the maximum occurrence at week 2 (fig. 5) . in this case, the influenza onset and maximum precede all the climatic variables, with closer relation to weekly precipitation amounts ( fig. 3 and 5) . the observed seasonal occurrence of influenza in all three regions using google trends is very similar (fig. 5 ). the large similarity between the three countries suggests that indeed the regional environmental factors may play an important role. when analyzing the individual years in terms of ili and flu+ relationship to cyprus low occurrence, some year-toyear variability is identified (fig. s1 ). for example, differences in the seasonality of influenza between years with a relatively low occurrence of cyprus lows (e.g., 2013) compared to years with a higher occurrence (e.g., 2009). still, the tight relationship between cyprus lows and influenza is retained. next, we quantify the relationship between the meteorological variables and seasonal influenza occurrence in israel. as a first choice, a stepwise multiple linear regression model is adopted for the relation between the predictors, i.e., cyprus lows j o u r n a l p r e -p r o o f and four individual meteorological variables (temperature, precipitation, specific humidity and relative humidity) and the predictand (flu+) for 2008-2017. it is found that the number of cyprus lows per week can explain 82% of the variance with a root mean square difference of 0.14. adding the other meteorological variables only marginally contributes to a higher explained variance (table 1) occurrence is identified using the student t-test at the 5% significance level (fig. 6 ). furthermore, a close inspection of figure 6 suggests that the seasonal variability of cyprus lows closely follows the seasonal variability of influenza occurrence, especially close to maximum occurrence of influenza. in addition, we tested other potential regression models for predicting flu+ from the weekly occurrence of cyprus lows. only marginal improvement is shown for increasing order of polynomial or sine non-linear models (table s2 ). in this study, we analyze the relationship between weather regimes and seasonal influenza over the eastern mediterranean for the period 2004-2017. we find that cyprus low weekly occurrence has the highest significant correlation (r = 0.91; p < 0.05) with weekly clinical influenza data over israel with respect to individual climate variables such as precipitation, temperature, specific humidity and relative humidity. influenza when performing a complementary analysis for the palestinian authority, jordan and israel using google trends data. the weekly occurrence of cyprus lows precedes the onset and peak of influenza occurrence with a lag of about 1 to 2 weeks, and a correlation for maximum occurrence of r = 0.88 (p < 0.05). the evolution of both curves matches in eight out of ten years. this is an important finding, since the influenza virus has ~3 days incubation period, and ~3 additional days until a patient visits a clinic and a few more days for positive virus identification. the role of weather in the spread of influenza is not yet fully understood. thus, it is not possible to explicitly determine the biological mechanism relating cyprus lows and influenza occurrence. however, the environmental setting given by the typical cold weather associated with the cyprus low may affect directly or indirectly influenza through the host and/or the pathogen, i.e., the epidemiological triangle (e.g., fuhrmann 2010). for example, the host susceptibility to infection during cyprus low days may increase due to seasonal hormonal changes, which may be related to a reduction in exposure to sun light. for example, some studies suggest that low levels of vitamin d may weaken the immune response (cannel et al., 2006) , while high levels may reduce the risk of both influenza and covid-19 infections and death (grant et al., 2020; merzon et al., 2020) . furthermore, rapid changes in weather, journal pre-proof which may influence both the host susceptibility and the pathogen survival, can also increase the risk of an influenza epidemic (liu et al., 2020) . indeed, the winter season in the eastern mediterranean is typically associated with rapid changes in weather governed by transitions from cyprus lows to high-pressure systems (alpert et al., 2004b) . the strongest variability in weather regime transitions is especially evident in early winter (hochman et al., 2020b) , which also corresponds to the onset of the influenza season. in addition, the ability of the influenza virus to cause infection is higher when the air is sufficiently cold (polozov et al., 2008) . finally, studies have provided evidence that fluctuations in the duration of social contacts may relate to weather conditions (e.g., smieszek 2009; willem et al., 2012) . indeed, indoor social contacts during cyprus low days may be more frequent and longer lasting. the present results suggest that the weather regime approach can be used to develop a tool for estimating the compatibility of the influenza transmission environment in a changing climate. this is particularly important, since weather and climate model forecasts are generally more robust in predicting weather regimes occurrences and timing than individual climatic variables, especially at regions distant from the el-niño (e.g., weisheimer and palmer 2014; grams et al., 2017) . this can be achieved by applying the methodology to sub-seasonal, seasonal, annual, decadal and even multi-decadal scales using climate model predictions / projections (marotzke et al., 2016; vitart and robertson, 2018) . we envisage that this novel approach could be applied to other regions (soebiyanto et al., 2015; chun et al., 2019) and infectious illnesses, such as vector-borne diseases and infectious gastroenteritis or even the sars-cov-2 and its associated disease covid-19. unfortunately, climatology tools and data are under-utilized in public health j o u r n a l p r e -p r o o f journal pre-proof (fuhrman 2010; hochman et al., 2020c) . this study exemplifies the potential for inter-disciplinary collaboration. the present results and methodology can potentially be helpful for public health in practical terms, i.e., better understanding of the correlation between weather regimes and influenza may improve vaccination policy and medical resources allocation. for example, health systems may roughly estimate the timing of seasonal influenza surge and improve the timing of seasonal vaccination campaigns for the general population, as well as for vulnerable populations including the elderly, poor, women, children, disabled, refugees and chronically ill patients. in addition, we suggest that the utilization of google trends and other social media information in real-time may be beneficial in sparsely monitored regions, such as several eastern mediterranean countries. improved understanding of the relationship between internet searches and actual illness patterns may help countries with limited monitoring of diseases to plan timely health promotion, including seasonal vaccination and campaigns for preventive measures, as well as plan allocation of medical resources. however, this type of information should not replace investments in traditional data gathering and analysis, but rather serve as a complement to it (lazer et al., 2014) . as a caveat, we note that seasonal influenza occurrence, as most other infectious diseases, may be influenced by: vaccination effectiveness, public awareness, biological and socio-economic factors etc., which are not easily quantified and measured (caini et al., 2018) . we further note that laboratory confirmed influenza cases may also suffer from inaccuracies. in fact, a recent review article that tested the quality of different laboratory tests for viral respiratory infections, including influenza found that the pooled sensitivity of the different tests was 90.9% (95% confidence interval of 88.7% -93.1%) and specificity of 96.1% (95% confidence interval of 94.2% -97.9%; vos j o u r n a l p r e -p r o o f journal pre-proof et al., 2019) . in addition, laboratory tests are indeed just the tip of the iceberg with respect to the actual incidence rates of influenza or any other infectious disease. climatic changes and associated health risks know no borders. the challenges climate change pose to society and especially to public health, can be properly met only with regional collaborations as clearly revealed in the covid-19 pandemic (otu et al., 2020) . this manuscript was prepared as part of a jordanian, palestinian, israeli and german collaboration towards the establishment of a regional climate change adaptation center (rccac). the collaborators are committed to this important regional trans-national cooperation, which will benefit the people of this vulnerable part of the world. epidemic influenza and vitamin d impact of infectious diseases on population health using incidence-based disability-adjusted life years (dalys): results from the burden of communicable diseases in europe study, european union and european economic area countries latitudes mediate the association between influenza activity and meteorological factors: a nationwide modelling analysis in 45 japanese prefectures from association between meteorological variations and activities of influenza a and b across different climate zones: a multi-region modelling analysis across the globe weather regimes and analogues downscaling of seasonal precipitation; a case study over israel the dynamics of cyclones in the twentyfirst century; the eastern mediterranean as an example dynamics and predictability of cold spells over the eastern mediterranean. climate dynamics (under review) forecasting seasonal influenza with a state-space sir model tackling covid-19: can the african continent play the long game? impact of regional climate change on human health progressive ordering with decreasing temperature of the phospholipids of influenza virus factors governing the inter-annual variation and the long-term trend of the 850-hpa temperature over israel links between the rainfall regime in israel and location and intensity of cyprus lows. international approach absolute humidity modulates influenza survival, transmission, and seasonality absolute humidity and the seasonal onset of influenza in the continental united states absolute humidity and pandemic versus epidemic influenza forecasting seasonal outbreaks of influenza a mechanistic model of infection: why duration and intensity of contacts should be included in models of disease spread modeling and predicting seasonal influenza transmission in warm regions using climatological parameters. plos (2017) modeling the spread of avian influenza viruses in aquatic reservoirs: a novel hydrodynamic approach applied to the rhône delta (southern france) rapid molecular tests for influenza, respiratory syncytial virus, and other respiratory viruses: a systematic review of diagnostic accuracy and clinical impact studies modelling the global spread of diseases: a review of current practice and capability health and climate change: policy responses to protect public health the lancet countdown: tracking progress on health and climate change the 2018 report of the lancet countdown on health and climate change: shaping the health of nations for centuries to come on the reliability of seasonal climate forecasts a nice day for an infection? weather conditions and social contact patterns relevant to influenza transmission impact of climate change on human infectious diseases: empirical evidence and human adaptation modelling seasonal influenza: the role of weather and punctuated antigenic drift relationship between humidity and influenza a viability in droplets and implications for influenza's seasonality developments and prospects in synoptic climatology the effects of synoptic weather on influenza infection incidences: a retrospective study utilizing digital disease surveillance this cross-border collaboration is a part of the track ⅱ initiative of the aravainstitute for environmental studies, israel. as such, we would like to thank robin twite and dr. yara dahdal for initiating cross-border collaboration. we would like to thank the team of the icdc and maccabi healthcare services, who routinely collect key: cord-314711-c6rqv4zd authors: pan, jinhua; yao, ye; liu, zhixi; meng, xia; ji, john s.; qiu, yang; wang, weidong; zhang, lina; wang, weibing; kan, haidong title: warmer weather unlikely to reduce the covid-19 transmission: an ecological study in 202 locations in 8 countries date: 2020-09-09 journal: sci total environ doi: 10.1016/j.scitotenv.2020.142272 sha: doc_id: 314711 cord_uid: c6rqv4zd purpose to examine the association between meteorological factors (temperature, relative humidity, wind speed, and uv radiation) and transmission capacity of covid-19. methods we collected daily numbers of covid-19 cases in 202 locations in 8 countries. we matched meteorological data from the noaa national centers for environmental information. we used a time-frequency approach to examine the possible association between meteorological conditions and basic reproductive number (r0) of covid-19. we determined the correlations between meteorological factors and r0 of covid-19 using multiple linear regression models and meta-analysis. we further validated our results using a susceptible-exposed-infectious-recovered (seir) metapopulation model to simulate the changes of daily cases of covid-19 in china under different temperatures and relative humidity conditions. principal results temperature did not exhibit significant association with r0 of covid-19 (meta p = 0.446). also, relative humidity (meta p = 0.215), wind speed (meta p = 0.986), and ultraviolet (uv) radiation (meta p = 0.491) were not significantly associated with r0 either. the seir model in china showed that with a wide range of meteorological conditions, the number of covid-19 confirmed cases would not change substantially. conclusions meteorological conditions did not have statistically significant associations with the r0 of covid-19. warmer weather alone seems unlikely to reduce the covid-19 transmission. the novel coronavirus disease 2019 is an infectious disease caused by severe acute respiratory syndrome coronavirus 2 (sars-cov-2). it was first identified in december of 2019 in wuhan, china, and has since become an ongoing pandemic. it has impeded global development and stressed health care delivery systems worldwide (li et al., 2020) . the number of confirmed covid-19 cases worldwide is still increasing; as of aug 31, 2020, more than 200 countries reported a total of 25,302,607 confirmed cases. the infectious capacity of sars-cov-2 is higher than middle east respiratory syndrome coronavirus (mers-cov), and severe acute respiratory syndrome (sars), which is a viral respiratory disease of zoonotic origin caused by severe acute respiratory syndrome coronavirus (sars-cov or sars-cov-1). (meo et al., 2020) previous studies have shown the importance of meteorological conditions in the transmission of infectious diseases, including, but not limited to, influenza and severe acute respiratory syndrome (sars). for example, it was reported that the transmission of sars can be influenced by meteorological factors (e.g., temperature, conclusions. yao et al. analyzed the association between temperature, relative humidity, and uv radiation with covid-19 transmission rate in 62 chinese cities and reported that warmer temperature could not mitigate the epidemic; besides, the relative humidity and uv radiation had no relationship with covid-19 transmission in china (yao et al., 2020) . the findings from studies in spain and iran were also consistent with the chinese study (briz-redon and serrano-aroca, 2020; sahafizadeh and sartoli, 2020) . other studies, however, came to an opposite conclusion that meteorological factors, such as temperature and relative humidity, were associated with confirmed covid-19 cases (byass, 2020; pani et al., 2020; runkle et al., 2020) . the different conclusions came from these aforementioned studies may partially contributed to the different statistical and modelling approaches(álvaro briz-redón and briz-redón, 2020) or due to their limited generalizability globally as they were conducted within one particular country with meteorological conditions specific to the local climate. therefore, this study aims to comprehensively examine the associations between meteorological factors (temperature, relative humidity, and wind speed) and from the databases compiled by johns hopkins university , we collected data on the daily reported covid-19 cases in 7 locations in australia, 9 locations in canada, and 50 locations in the united states (us). from the respective ministries of health, we collected covid-19 data in 63 locations in china (2020c), 8 locations in germany(2020e), 19 locations in italy, 5 locations in japan(2020b), and 41 locations in the united kingdom (uk) (2020a). all these locations have cumulative number of cases over 50 to enable estimation of the basic reproductive number (r 0 ) of covid-19. in brief, r 0 represents the expected number of secondary cases produced by an initial infectious individual in a completely susceptible population (pan et al., 2020) . in order to obtain stable r 0 and to avoid influences of difference in detection methods, inspection strategies and reported ways on the number of confirmed cases in different countries, we determined the initial days for various locations according to the following criteria: 1) there should be consecutive case days lasting at least four days, and 2) the number of newly confirmed cases should not equal to one in any of these four days, then 3) the first day of the aforementioned dates was chosen as the first case-day in the study regions. in each location, a total of 18 days (17 days after of the initial date and including the initial date) were used to estimate r 0 . we employed the method introduced by king et al. to estimate r 0 (aaron a. king et al., october 30, 2017) . first, we constructed a linear regression model to estimate the correlation coefficients. second, we obtained r 0 by combining the coefficients j o u r n a l p r e -p r o o f journal pre-proof obtained derived from the previous step with the average incubation and confirmation periods. we assigned the average values of the incubation period and the average days from infection to confirmation as 7.0 and 3.8 days, respectively, according to a previous research(li et al., 2020). meteorological parameters include temperature, relative humidity, wind speed, and uv radiation. we collected hourly data of temperature, relative humidity, and wind speed from the noaa national centers for environmental information(2020d). daily mean levels of these meteorological factors were calculated at station level and then aggregated to location levels to be matched with r 0 of covid-19. regarding uv radiation, daily erythemally weighted daily dose (edd) data were extracted from the dutch-finnish ozone monitoring instrument (omi) level 2 uv irradiance products with version 003 (omuvb v003) at 13 km × 24 km resolution. omi is a nadir-viewing spectrometer aboard the nasa aura satellite covering uv wavelength from 270 -380 nm. the average of edd values from omi pixels matched within these locations was assigned as the daily mean edd level for the corresponding locations. firstly, we used the wavelet coherence analysis to examine the possible association between meteorological factors and covid-19 cases in 198 locations. abruzzo in j o u r n a l p r e -p r o o f italy, stockton-on-tees and suffolk of the uk, and delaware of the us were excluded from this analysis because of missing data in daily temperature for some days. the association between daily meteorological factors and numbers of covid-19 cases in these locations was measured by the mathematical "magnifying glass" of wavelet coherency analysis (he et al., 2018) . the method quantitatively represents the internal covariates between the two-time series according to the synchronization intensity of the two time series trends. in the present analysis, the daily time series pairs (e.g. covid-19 cases and temperature) were used to implement wavelet coherency analysis (he et al., 2018) . larger coherency value implies stronger association. secondly, we estimated the country-specific associations between meteorological factors and r 0 of covid-19 in the same period using multiple regression models. we then used meta-analysis to pool the p values of the country-specific associations of meteorological factors with r 0 . finally, to validate the observed associations of meteorological factors with the covid-19 transmission, we constructed a susceptible-exposed-infectious-recovered (seir) model ( figure s1 ) using chinese data. we chose china because more detailed meteorological data and case information were available only in the chinese cities. specifically, when a susceptible (s) person encounters a covid-19 case, this person is likely to be infected by the virus (e) and progress to the infected phase (i), and the person may appear to have obvious symptoms and be subsequently diagnosed. the patients might be treated (t), or they have been showing asymptomatic infection and j o u r n a l p r e -p r o o f journal pre-proof stay in sub-clinical stage (u), and then most of them will join the rehabilitation group (recovery, r). the flow diagram for the model appears in figure s1 and the formula for the model are shown below, of which β 1 represents the probability of transmission following an effective contact between infectious and exposed cases and susceptible individuals, β 2 represents the probability of transmission following a contact between subclinical cases and susceptible individuals, q is the quarantine rate, j is the detection rate, α 1 is the death rate, γ 1 and d are progression rate of cases from confirmed to recovery and exposed to infection, respectively. μ 1 and μ 2 are ratios of subclinical and confirmed cases. we constructed the seir models for wuhan and other chinese cities separately, given the dominant covid-19 cases from wuhan. in the seir models, we estimated the r 0 under various temperature and relative humidity using the relationship established in the regression models. we then estimated daily number of confirmed cases and new cases under expanded range of temperature and humidity (the range of temperature: -10 to 40 degrees; the range of relative humidity: 55% to 95%). then we used one-way anova analysis to test the differences between the daily confirmed cases of covid-19 under different meteorological conditions. the detailed formula in the seir model are as the following: j o u r n a l p r e -p r o o f all calculations were completed in r software version 3.6.1 (r foundation for statistical computing) and matlab r2019b. a p value of less than 0.05 was considered to indicate statistical significance. among the 202 locations, the mean ± standard deviation and range of r 0 of covid-19 were (1.7±0.5, 0.6-4.0) in 202 districts. the top three locations with highest r 0 were hamburg and hessen in germany and new york in the us. the average temperature was 6.7 °c, with a range of -23.0°c to 29.6°c and the median ± interquartile range for temperature in these locations were shown in supplemental table 1 . the meteorological conditions and r 0 of covid-19 in these locations exhibited different spatial patterns (figure 1) . generally, the locations far away from the equator have lower temperatures. the uv radiation tended to decrease with decreasing temperature (figure 1 ). when holding temperature constant, increasing relative humidity did not show uniform upward or downward trend in relation to r 0 (figure 2a) . there was no significant association between r 0 and other meteorological parameters, such as wind speed or edd (figure 2b ). j o u r n a l p r e -p r o o f in total, 198 wavelet coherency spectra were obtained (one for each study region) ( figure s2 ). figure 3 indicated that countries closer together showed more similar wavelet coherence figures. in general, we found that in these countries, the wavelet coherence value was relatively small, and only in a few days a relatively large wavelet coherence value was observed, suggesting temperature be less likely to be associated with covid-19. in the single-variable model, temperature exhibited no significant associations with r 0 of covid-19 (meta p=0.446, see figure 4) , showing that the covid-19 transmission would not change with increasing temperature. in the 200 locations with complete meteorological factors, multi-variable regression analysis found that temperature (meta p=0.591), relative humidity (meta p=0.215), and wind speed (meta p=0.986) were not significantly associated with r 0 (figure 5) , suggesting that the transmission capacity of covid-19 would not change with the variation of temperature, wind speed, or relative humidity. the uv radiation data were collected only in 134 locations in china, uk and us. after adjustment for temperature, wind speed, and relative humidity, there was no significant association between uv and r 0 (meta p=0.491) either ( figure 6 ). in this analysis covering 202 locations in 8 countries, meteorological conditions (temperature, wind speed, relative humidity, and uv radiation) were not significantly associated with the covid-19 transmission, suggesting that warmer weather alone seems unlikely to reduce the spread ability of the pandemic. to our knowledge, this is the first study at a global scale to examine the relationship between meteorological conditions and epidemiological characteristics of covid-19 using multiple regression models, mete-analysis, wavelet analysis and seir models. previous studies reported that certain meteorological factors may have effect on the transmission of respiratory-borne infectious diseases (chan et al., 2011; jaakkola et al., 2014) . the conditions of successful transmission of respiratory pathogenic microorganisms are to maintain a certain degree of virulence in the whole airborne transmission process. the possible drivers may include temperature, humidity, uv radiation, and air ventilation (duguid, 1946; herfst et al., 2017) journal pre-proof temperature and humidity, which was also characteristic of an h3n2 seasonal strain (steel et al., 2011) . furthermore, lowen et al. provided evidence that humidity and temperature conditions could affect the effective transmission of influenza viruses (lowen et al., 2007) . besides, uv radiation is a major inactivating factor for influenza viruses in the outdoor environment (weber and stilianakis, 2008) and thus a high level of uv exposure may also constrain the transmission of sars-cov virus (rabenau et al., 2005) . therefore, it is hypothesized that covid-19 transmission may decrease or even disappear when the temperature increases in the summer. in this multi-country analysis, we did not observe the aforementioned relationship between temperature and transmission of covid-19, even after adjusting for other potential confounders. several prior studies also found that temperature did not play significant role in covid-19 infection (baker et al., 2020; briz-redon and serrano-aroca, 2020; sahafizadeh and sartoli, 2020; yao et al., 2020) , for example, baker et al. used a climate-dependent epidemic model to simulate the covid-19 pandemic, and found that without effective control measures, summer weather would not substantially limit pandemic growth (baker et al., 2020) . briz-redon et al. used spatial-temporal analysis to explore the relationship between cumulative number of covid-19 cases and temperature, and found no evidence suggesting a reduction in covid-19 cases at higher temperature (briz-redon and serrano-aroca, 2020). a few others reported opposite findings (mendez-arriaga, 2020; qi et al., 2020; shi et al., 2020; tosepu et al., 2020) . for example, auler et al. (auler et al., 2020) . explored the relationship between meteorological conditions and the spread ability of covid-19 j o u r n a l p r e -p r o o f in the most affected brazilian cities and found higher mean temperatures and average relative humidity favored the covid-19 transmission. additionally, shahzad et al. (shahzad et al., 2020) and xie et al. (xie and zhu, 2020) also found a relationship between temperature and daily covid-19 confirmed cases. to further verify our findings, we constructed a seir model using chinese data and found that with increasing temperature, the new confirmed cases of covid-19 did not decrease significantly. in this aspect, it might be premature to count on warm weather to stop the covid-19 transmission. our study has strengths and limitations. the major strength is utilizing data from 202 locations in 8 countries, covering wide climate areas and enabling our findings generalized globally. also, there are several limitations of this study. firstly, our major outcome, r 0 of covid-19, is influenced by a number of factors such as various lockdown policies across countries, different phases of the covid-19 epidemic, as well as other unmeasured confounders. in response, we conducted a two-stage analysis (first within country, and then multi-country) to account for the variation of control policy across countries. also, to facilitate a comparison of r 0 across various locations, we uniformly chose a total of 18 days in each location (17 days after of the initial date and including the initial date) to calculate r 0 . secondly, our study is ecological in nature, with lack of individual-level (e.g. patients' age, sex) and some location-specific information (e.g. intensity of control policy, availability of medical resources), which may have an influence on the covid-19 transmission and confound our results. another limitation is the use of relative humidity, which is be j o u r n a l p r e -p r o o f we chose these 202 locations because detailed daily data of new confirmed covid-19 cases and environmental factors of these locations are available in the public database, which may cause selection bias to some extent. future studies should develop complicated models with higher spatial-temporal resolution to assess the relationship between meteorological conditions and the epidemiological characteristics of covid-19. conclusively, this study provides the first global evidence that meteorological factors do not have significant effect on the covid-19 transmission. given the lack of association, public health agencies should not rely on the warm weather to flatten the curve of covid-19 transmission. therefore, the non-medication interventions should be implemented consistently to keep constraining the epidemic caused by sars-cov-2, in case of another resurgence. j o u r n a l p r e -p r o o f to all the data in the study and had final responsibility for the decision to submit for publication. none. the institutional review board at the school of public health, fudan university, approved the study protocol with a waiver of informed consent. data were analyzed at aggregate level and no participants were contacted. introduction to model parameter estimation the effect of climate on the spread of the covid-19 pandemic: a review of findings, and statistical and modelling techniques evidence that high temperatures and intermediate relative humidity might favor the spread of covid-19 in tropical climate: a case study for the most affected brazilian cities susceptible supply limits the role of climate in the early sars-cov-2 pandemic coronavirus (covid-19) in the uk a spatio-temporal analysis for exploring the effect of temperature on covid-19 early evolution in spain eco-epidemiological assessment of the covid-19 epidemic in china the effects of temperature and relative humidity on the viability of the sars coronavirus the size and the duration of air-carriage of respiratory droplets and droplet-nuclei spatiotemporal variation of the association between climate dynamics and hfrs outbreaks in eastern china during 2005-2016 and its geographic determinants drivers of airborne human-to-human pathogen transmission italy ministry of health. coronavirus disease-19 decline in temperature and humidity increases the occurrence of influenza in cold climate national health commission of people's republic of china. covid-19 confirmed case information in china noaa national centers for environmental information effectiveness of control strategies for coronavirus disease 2019: a seir dynamic modeling study association of covid-19 pandemic with meteorological parameters over singapore covid-19 transmission in mainland china is associated with temperature and humidity: a time-series analysis stability and inactivation of sars coronavirus the modest impact of weather and air pollution on covid-19 transmission covid-19: fallzahlen in deutschland und weltweit short-term effects of specific humidity and temperature on covid-19 morbidity in select us cities high temperature has no impact on the reproduction number and new cases of covid-19 in bushehr asymmetric nexus between temperature and covid-19 in the top ten affected provinces of china: a current application of quantile-on-quantile approach impact of temperature on the dynamics of the covid-19 outbreak in china transmission of a 2009 pandemic influenza virus shows a sensitivity to temperature and humidity similar to that of an h3n2 seasonal strain correlation between weather and covid-19 pandemic in jakarta inactivation of influenza a viruses in the environment and modes of transmission: a critical review association between ambient temperature and covid-19 infection in 122 cities from china no association of covid-19 transmission with temperature or uv radiation in chinese cities key: cord-322787-dbtc0bo3 authors: runkle, jennifer d.; sugg, margaret m.; leeper, ronald d.; rao, yuhan; mathews, jessica l.; rennie, jared j. title: short-term effects of weather parameters on covid-19 morbidity in select us cities date: 2020-06-09 journal: sci total environ doi: 10.1016/j.scitotenv.2020.140093 sha: doc_id: 322787 cord_uid: dbtc0bo3 abstract little is known about the environmental conditions that drive the spatiotemporal patterns of sars-cov-2, and preliminary research suggests an association with weather parameters. however, the relationship with temperature and humidity is not yet apparent for covid-19 cases in us cities first impacted. the objective of this study is to evaluate the association between covid-19 cases and weather parameters in select us cities. a case-crossover design with a distributed lag nonlinear model was used to evaluate the contribution of ambient temperature and specific humidity on covid-19 cases in select us cities. the case-crossover examines each covid case as its own control at different time periods (before and after transmission occurred). we modeled the effect of temperature and humidity on covid-19 transmission using a lag period of 7 days. a subset of 8 cities were evaluated for the relationship with weather parameters and 5 cities were evaluated in detail. short-term exposure to humidity was positively associated with covid-19 transmission in 4 cities. the associations were small with ¾ cities exhibiting higher covid19 transmission with specific humidity that ranged from 6 to 9 g/kg. our results suggest that weather should be considered in infectious disease modeling efforts and future work is needed over a longer time period and across different locations to clearly establish the weather-covid19 relationship. experimental and observational studies demonstrate the influence of meteorological parameters on the seasonal transmission of influenza, human coronavirus (hcov), and human respiratory syncytial virus (rsv), which are often characterized by distinct increases in incident cases and detection frequency in the winter months (lowen and j o u r n a l p r e -p r o o f 3 in the us. as the us begins its public health response to covid-19, the implementation of extensive public health interventions are needed at appropriate time scales to mitigate the public health and economic impacts of the covid-19 pandemic. research on the seasonality and influence of meteorological parameters on covid-19, such as temperature and specific humidity, can be used to inform the timing of effective interventions to mitigate sars-cov-2/covid-19 transmission at the local scale to save countless lives and resources. the objective of this research is to examine the association between meteorological variables and covid-19 in us cities. unlike previous studies, we will use a highresolution spatiotemporal meteorological dataset to answer the following: is there an association with meteorological parameters and covid-19? if so, which meteorological parameters predict covid 19 transmission? is the association stronger after accounting for locally implemented social distancing measures? how does this relationship vary spatially across the us? by answering these questions, the knowledge gained on the contribution of environmental factors like temperature and humidity on transmission can be paired with other nonpharmaceutical interventions related to behavioral (e.g., wearing face mask, washing hands) factors that boost immunity or the timing of social distancing measures with seasonal spikes in influential environmental parameters to reduce transmission. this retrospective case-crossover study examined the nonlinear and delayed association between environmental factors and covid-19 j o u r n a l p r e -p r o o f 4 transmission. we selected the following us locations that exhibited high relative caseloads of covid-19 in the early stages of the pandemic for their underlying populations: seattle, washington; new york, ny; albany ga; new orleans, la.; bridgeport-stamford-norwalk, conn.; pittsfield, mass; detroit, mi; chicago, il. figure 1 is a map of the 8 study locations. we assumed at least a median incubation period of 5.2 days (lauer et al 2020) . case counts were log-transformed, and time series were created when cities had more than 2 new daily cases. because deidentified and anonymized data on case morbidity were obtained from a publicly accessible data portal this research did not involve participant consent and institutional review was not warranted. environmental parameters. meteorological data were derived from the european center for median range weather forecast (ecmwf) atmospheric reanalysis dataset (era-5) (c3s, 2017). era-5 provides a suite of hourly weather parameters that may affect local covid-19 transmissions at a 30-km spatial resolution. while not commonly used in environmental health studies, the advantage that era-5 data provides over individual weather station data is that spatial heterogeneity is more representative and the estimation of health effects of temperature and humidity can be derived in locations far j o u r n a l p r e -p r o o f 5 from weather stations or without any station. previous research has shown that reanalysis data and weather station data show similar health risk estimates (roye et al 2020). daily average near-surface air temperature, specific humidity, and solar radiation were extracted from era-5 for each study location by a simple spatial average. because relative humidity (rh) is highly correlated with temperature, we chose to instead include specific humidity as a predictor variable in the analysis. heat mapping. preliminary studies have suggested that the combination of humidity and air temperature could affect the transmission of local covid-19 cases (e.g., sajadi et al., 2020 , lou et al., 2020 , oliveriros et al., 2020 . we examined the association between local covid-19 cases and air temperature and specific humidity using the density heatmap. to construct the density heatmap, the daily confirmed covid-19 case reports were first separated based on their corresponding daily mean air temperature (every 1°c) and mean specific humidity (every 0.5 g/kg). all daily confirmed case counts were classified into the same air temperature and specific humidity conditions (e.g., 0 °c < t air < 1 °c and 1 g/kg < q < 1.5 g/kg) and evaluated together as a density measurement. this explanatory analysis was intended to demonstrate the association of covid-19 cases with the combined effect of air temperature and specific humidity. the heatmap could identify the range of optimal meteorological conditions for local transmissions. considering the incubation period of covid-19, we applied the analysis j o u r n a l p r e -p r o o f 6 nonlinear model (dlnm). this approach is more flexible than conditional logistic regression (armstrong et al 2014) in that it allows for overdispersion. the application of the dlnm to the case-crossover design provides a means to assess the nonlinear and delayed effects, as well as the cumulative exposure-response between short-term daily average exposure to meteorological parameters and daily counts for covid-19 cases. we performed separate analyses for our primary health outcome --covid-19 morbidity --and each meteorological parameter relative to the median and quartiles (i.e., 50th versus 75th). this approach is suitable for studying the effects of time-varying exposures (e.g., intermittent changes in meteorological) on a rare, acute condition (i.e., covid-19 transmission) (armstrong et al., 2019 , malig et al., 2016 , guo et al., 2011 . we relied on the following equation: where t is the day of the observation; y t is the observed daily case counts on day t; α is the intercept; t t,l is a matrix obtained by applying the dlnm to temperature or humidity, β is a vector of coefficients for t t,l , and l is the lag days. strata t is a categorical variable of day (30 day time period) used to control for trends, and λ is a vector of coefficients. sd t is a binary variable that is "1" if day t was a social distancing order, and υ is the coefficient. our model was adapted from similar work by guo et al 2011 who also employed a case-crossover design and dlnm to investigate the effects of temperature on mortality (guo et al 2011). given that the incubation period between exposure and symptom occurrence is 2 to 14 days (linton et al 2020), we used a maximum 14-day lag period to explore the potential delayed association of temperature and humidity in our model for approximating the pre-and post-infection period for each case. sensitivity analysis. a sensitivity analysis was conducted to select degrees of freedom for the lag polynomial (2-8 degrees of freedom) and the response polynomial (2-8 degrees of freedom) for new orleans, la (data not shown). in addition, we changed the maximum lag to 14 and 20 days, which gave similar results (data not shown). prior research has examined a 0 day, 3 day to 5 day lags for covid-19 transmission (ma et al 2020 all the way to a lag period extending 7 to 14 days for meteorological parameters (islam et al 2020). for our initial examination of meteorological parameters independently, we compared the best model fit using quasi-akaike information criterion (q-aic) to determine the optimal degrees of freedom and lag periods. q-aic is a well-established technique for sensitivity analysis and was used to compare dlnm-only models and dlnm+case-crossover models to confirm the final model selection (guo et al. 2011) . models were also examined for the adjustment for trends, such as the day of the week. however, due to the short time series, differences were minimal or resulted in a poor fit (high q-aic) and thus we selected the most j o u r n a l p r e -p r o o f 8 parsimonious model. the "dlnm" package was used to create the dlnm model (gasparrini 2011) using r statistical software (r core team 2020). we adopted the rare-disease assumption where our study hypothesis tested the association between weather exposure and a disease (i.e., covid-19) characterized by low prevalence. therefore, we assumed the odds ratio to approximate the relative risk. all relative risks (rr) were presented with corresponding 95% confidence intervals (95% cis). attributable burden of covid-19 transmission due to weather. in epidemiology, measures of potential impact are used to examine the expected impact of changing the distribution of one or more risk factors in a particular population (kleinbaum et al 1982 , szklo et al 2014 . for example, the attributable risk, also known as the etiologic fraction, is used to examine the proportion of all new cases in a given time frame that is attributable (or causally associated) to the exposure of interests (szklo et al 2014) . because the evidence-base linking covid-19 transmission and weather is new and evolving, it is too early to assume a causal association. therefore, we relied on the excess fraction (ef) as an analogous, but alternative measure to the attributable risks in our analysis, to approximate the excess caseload due to exposure. to examine the attributable burden of transmission for covid-19 due to weather we calculated the percent excess fraction for humidity and temperature for individual cities. we used the following equation: % ef = b x (rr i -1) / b x (rr -1.0 i ) + 1.0), where b is the point prevalence of covid-19 for each city. point prevalence was calculated as the number of cases over the study period divided by the total population in a specific city. we table 1 ). the crude rate of covid-19 per location was highest for new orleans, la (374 daily cases per 100,000 people), followed by new york city, ny (51 daily cases per 100,000 people), albany, ga (42 daily cases per 100,000 people), and bridgeport, ct (25 daily cases per 100,000 people). the lowest rates of covid-19 cases were in seattle, wa (4 daily cases per 100,000 people), and pittsfield, ma (8 cases per 100,000 people). the highest crude death rates were observed in new york city, ny (6 daily deaths per 100,000 people), albany ga (3 daily deaths per 100,000 people), new orleans, la (2 daily deaths per 100,000 people) and detroit, mi (2 daily deaths per 100,000 people). the density heatmap ( figure 2 ) presents a descriptive explanatory analysis of the combined association of temperature and specific humidity on covid-19 cases for the selected cities. based on the heatmap, covid-19 cases were more common in low specific humidity (2 -6 g/kg) and low temperature (2 -11 °c) conditions. this association was consistent when we consider different incubation times (lag 0-14 days). all locations. table 2 shows the goodness of fit (qaic) values across model types for all locations and parameters, which is a common validation and sensitivity technique (e.g, gasparrini et al. 2010 , guo et al. 2011 . in general, the humidity was the strongest j o u r n a l p r e -p r o o f 10 predictor for covid-19 cases, with a better model performance for humidity than temperature across all model types and study locations. case crossover models performed higher in seattle, wa, new york city, ny, chicago, il, and new orleans, la. the variation in the dose-response profile for humidity was negligible before and after adding temperature as a predictor into the model, indicating that humidity exhibited a robust association. model performance was poor (indicated by high qaic values) for detroit, mi, pittsfield, ma, and bridgeport, ct. results for these cities were insignificant and therefore not reported in the final results (supplemental figures 1,2) . overall, the case-crossover + dlnm model outperformed the dlnm only model. however, select locations had better model fit for dlnm only (e.g., albany, ga), although marginally better. results were presented for the following cities: new orleans, la, albany, ga, and seattle, wa, and models were selected based on qaic values. dlnm and casecrossover models were also constructed for these locations to analyze the effect of solar radiation (watts/m 2 ) on covid incidence rates. new orleans, la. the relative risk for covid-19 exhibited a u-shaped relationship with increases in cases at high and low humidity in new orleans. with reference to the median humidity, relative risk peaked at minimum (5 g/kg, rr: 1.98, ci: 1.07-3.66) and maximum (16 g/kg, rr: 2.18, ci: 1.28-3.72) values. similarly, temperature exhibited a u-shaped relationship with reference to the median and a significant relative risk at 16-17°c (rr: 1.17-1.23; ci: 1.03-2.24) and at the maximum observed temperatures (23°c; rr: 1.75, ci: 1.13-2.44). solar values exhibited an inverted u-shaped relationship with a higher relative risk from 5200 -6300 (watts/m 2 ) (figure 3 ). albany, ga. temperature and solar radiation were not significant predictors of covid-19 cases. with reference to the median humidity, significant relative risk is observed from 6 to 9 g/kg (rr: 1.23-1.47, ci: 1.06-1.94). due to a lower qaic value and more robust results, unlike other cities, a dlnm-only model was applied to the humidity and the covid-19 relationship for albany, ga (figure 4) . incidence that revealed a protective effect from 9 to 10°c (rr: 0.60-0.69, ci:0.39-0.95), whereas no relationship was observed between humidity and solar radiation and covid-19 cases in nyc ( figure 6) . seattle, wa. the temperature was significant from 3 to 5°c (rr: 1.59-1.95, ci: 1.22-2.65). however, the humidity was significant at the lowest values with an increased risk of transmission occurring at less than 3 g/kg (rr: 1.44, ci: 1.16-1.80). lower risk of transmission was observed for the lowest values of solar radiation (i.e., less than 3200 watts/m 2 , rr: 0.93, ci: 0.89-0.97) (figure 7) . the excess burden of new covid-19 cases due to weather. overall, the attributable burden of excess covid-19 cases associated with exposure to humidity and temperature was low for each city (table 3 ). the excess fraction was the highest for j o u r n a l p r e -p r o o f new orleans, with 3.7 to 4.5% of new cases occurring within the humidity range of 5g/kg to 16g/kg and 6.8 to 9.1% occurring within the temperature range of 16(°c) to 23(°c). in this study, we examined whether daily meteorological patterns in humidity, temperature, and solar radiation were associated with the transmission of covid-19 in u.s. cities that emerged as early hot spots for infection. we applied the dlnm to a case-crossover design to assess the nonlinear and delayed effects of meteorological parameters on covid-19 incident cases. to our knowledge, this study is the first to assess the effects of meteorological variables on covid-19 morbidity using a robust distributed lag nonlinear model and case-crossover design. we observed a weak but statistically significant relationship between covid and meteorological parameters for (sajadi et al., 2020) . humidity was observed as the best predictor for the coronavirus outbreak followed by temperature and solar radiation. the majority of cities included in this study demonstrated a nonlinear dose-response relationship between a range of specific humidity conditions and sustained covid-19 transmission. more specifically, 3 of the 4 cities were characterized by a significant relationship between covid-19 transmission and humidity (e.g., albany, ga, new orleans, la, and chicago, il). humidity in the range of 6 to 9 g/kg (analogous to an absolute humidity range of 7.56-11.37 g/m 3 ) was a significant predictor of covid-19 cases and resulted in an up to two-fold increased temperature and solar radiation did not exhibit a strong association with covid19 incidence in our study locations. our results for new york city, ny support and extend previous research on covid19 and meteorological parameters in new york city that found a significant association with temperature using simple correlation coefficients (bashir 2020). bashir et al. observed a direct association with higher temperatures predicting higher covid-19 cases (2020). conversely, our research found a protective effect at higher temperatures and is corroborated by earlier studies (qi et al., 2020, unlike previous studies examining the influence of meteorological factors on covid19 transmission, one strength of our study is the adjustment for social distancing measures (sajadi et al 2020) . most environmental health research includes either a variable for relative humidity (rh) and/or absolute humidity (ah). specific humidity is more conservative and less susceptible to changes in pressure and temperature compared to ah. further, in addition to the confounding influence of humidity and temperature, rh is typically not useful as a stand-alone humidity variable in environmental health or epidemiological research. our results are only comparable to a few recent studies examining the association between covid-19 and specific humidity (e.g., ma et al., 2020 , sajadi et al., 2020 . recent research has demonstrated the linkage between poor air quality and covid-19 mortality (wu et al. 2020) , and in our study, we did not adjust for background air quality measures as a potential confounding factor. while our modeling strategy did adjust for social distancing measures, our estimates do not account for underreporting of case counts (lachmann 2020) , demographic data on cases, changes in testing capacity, or the date of onset of covid19 symptoms. this study did not include information on the newly discovered coronavirus as the primary cause of severe acute respiratory syndrome correcting under-reported covid-19 case numbers. medrxiv the frequency and seasonality of influenza and other respiratory viruses in t tennessee: two influenza seasons of surveillance data the incubation period of coronavirus disease 2019 (covid-19) from publicly reported confirmed cases: estimation and application yangy, et alincubation period and other epidemiological characteristics of 2019 novel coronavirus infections with right truncation: a statistical analysis of publicly available case data defining the epidemiology of covid-19-studies needed roles of humidity and temperature in shaping influenza seasonality the role of absolute humidity on transmission rates of the covid-19 outbreak effects of temperature variation and humidity on the death of covid-19 in wuhan a time-stratified case-crossover study of ambient ozone exposure and emergency department visits for specific respiratory diagnoses in california determining the seasonality of respiratory syncytial virus in the united states: the impact of increased molecular testing seasonal variations of respiratory viruses and etiology of human rhinovirus infection in children seasonality of respiratory viral infections. annual review of virology coronavirus infections-more than just the common cold coronavirus as a possible cause of severe acute respiratory syndrome covid-19 transmission in mainland china is associated with temperature and humidity: a timeseries analysis. science of the total environment, 138778. r core team (2020). r: a language and environment for statistical computing. r foundation for statistical computing temperature and latitude analysis to predict potential spread and seasonality for covid-19 the impact of temperature and absolute humidity on the coronavirus disease 2019 (covid-19) outbreak-evidence from china potential factors influencing repeated sars outbreaks in china epidemiology: beyond the basics global influenza seasonality: reconciling patterns across temperate and tropical regions environmental predictors of seasonal influenza epidemics across temperate and tropical climates high temperature and high humidity reduce the transmission of covid-19 exposure to air pollution and covid-19 mortality in the united states the relationship between air quality and respiratory pathogens among children in suzhou city key: cord-328509-l4yz1ude authors: sharma, shubham; zhang, mengyuan; anshika; gao, jingsi; zhang, hongliang; kota, sri harsha title: effect of restricted emissions during covid-19 on air quality in india date: 2020-08-01 journal: sci total environ doi: 10.1016/j.scitotenv.2020.138878 sha: doc_id: 328509 cord_uid: l4yz1ude the effectiveness and cost are always top factors for policy-makers to decide control measures and most measures had no pre-test before implementation. due to the covid-19 pandemic, human activities are largely restricted in many regions in india since mid-march of 2020, and it is a progressing experiment to testify effectiveness of restricted emissions. in this study, concentrations of six criteria pollutants, pm(10), pm(2.5), co, no(2), ozone and so(2) during march 16th to april 14th from 2017 to 2020 in 22 cities covering different regions of india were analysed. overall, around 43, 31, 10, and 18% decreases in pm(2.5), pm(10), co, and no(2) in india were observed during lockdown period compared to previous years. while, there were 17% increase in o(3) and negligible changes in so(2). the air quality index (aqi) reduced by 44, 33, 29, 15 and 32% in north, south, east, central and western india, respectively. correlation between cities especially in northern and eastern regions improved in 2020 compared to previous years, indicating more significant regional transport than previous years. the mean excessive risks of pm reduced by ~52% nationwide due to restricted activities in lockdown period. to eliminate the effects of possible favourable meteorology, the wrf-aermod model system was also applied in delhi-ncr with actual meteorology during the lockdown period and an un-favourable event in early november of 2019 and results show that predicted pm(2.5) could increase by only 33% in unfavourable meteorology. this study gives confidence to the regulatory bodies that even during unfavourable meteorology, a significant improvement in air quality could be expected if strict execution of air quality control plans is implemented. • the effect of restricted human activities due to the covid-19 pandemic in india on air quality in 22 cities was estimated. • pm 2.5 had maximum reduction in most regions. • correlation between cities especially in northern and eastern regions improved in 2020 compared to previous years. • the substantial reduction in concentrations resulted in a 4 times reduction in total er. • pm 2.5 could increase due to unfavourable meteorology but the average concentration would still be under cpcb limits. a b s t r a c t a r t i c l e i n f o air pollution has come up as a growing concern all over the world, especially in developing nations like india. india witnessed economic growth, rapid expansion of cities, industrialization, and fast-paced development of infrastructure since liberalization during the 1990s. simultaneously, the level of air pollution in india has increased to a major health risk and cause of large premature mortality. approximately one million people died in 2015 due to ambient particulate matter (pm) pollution alone in india (guo et al., 2017) . indian cities have been always making into the top 20 most polluted cities of the world for the past few years and exceeding the ambient air quality standards recommended by the world health organization and central pollution control board (cpcb) kota et al., 2018; mukherjee and agrawal, 2018) . pm, the most dominant pollutant, in major parts of india has major contributions from vehicles, residential, energy, industrial and dust (guo et al., 2017; guo et al., 2019) . to control the severe air pollution in the country, the national clean air programme (ncap) launched a five-year action plan was launched in 2019 with a goal of reducing pm by 30% nationwide (moefc, 2019). are effective strategies followed up by efficient implementation can reduce the air pollution as expected? it is an open question as atmospheric processes that determine concentrations of air pollutants are nonlinear and changing meteorology plays significant roles in pollution formation. for example, the chinese five year clean air action plan resulted in improved air quality in china (j. li et al., 2019) . however, the peak pm 2.5 concentrations during episodes in winter did not reduce due to unfavourable meteorology (wang et al., 2019) . similarly, zhang et al. (2014) estimated~33% reduction in nitrate in eastern us by emission control was offset by meteorology. a simulation done in china showed that metrology played very important role in air pollution formation and severe air pollution was not avoided during the lockdown in january and february 2020 (wang et al., 2020) . the spread of coronavirus disease 2019 (covid 19), which was initially identified in wuhan of china, resulted in more than one million cases worldwide within the first four months. this has resulted in lockdown in many nations worldwide. while, the first confirmed case in india was on january 30th, 2020, the first international travel advisory posing restrictions on travel to china, republic of korea, iran, italy and japan was issued on march 11th of after the country saw sudden jump in covid-19 cases on march 4th (https://www.mohfw.gov.in/). southern state of india, kerala, which was initially the most effected state imposed curtails on mass gatherings on march 10th. starting from march 16th all places of mass gatherings such as institutions, shopping malls and theatres were closed across the country. the first nationwide lockdown for fourteen hours was on march 22nd, which was followed by 21 days lockdown starting from march 24th. this lockdown enforces restrictions and self-quarantine measures, which reduce emissions from transportation and industries. the changes in air pollution in this lockdown period can provide an insight into the achievability of air quality improvement when there are significant restrictions in emissions from many sources and gives regulators better plans to control air pollution. in this paper we analysed the variations in ground-based air quality and meteorological data obtained from a network of air quality monitoring stations across 22 different cities in india for the past four years (2017-2020) for the time period of march 16th to april 14th. comparison of data in the last four years helps in understanding the potential effect of change in emissions during days with similar meteorology. this paper also explores the possible scenario which could result in national capital region if similar control on anthropogenic emissions occurs in worst meteorology conditions using weather research forecasting (wrf)-air quality dispersion modelling system (aermod). to study the changes in air quality during the lockdown period, the data from 22 cities covering different regions of india were analysed, i.e. bhopal and dewas in centre, jorapokhar, patna, gaya, brajrajnagar and kolkata in the east, faridabad, amritsar, jodhpur, delhi, agra, kanpur and varanasi in the north, amravati, bengaluru, thiruvananthapuram and chennai in the south, as well as ahmedabad, mumbai, nagpur and pune in the west. concentrations of the different pollutants for the time period of march 16th to april 14th from 2017 to 2020 were analysed. the hourly concentrations of seven air pollutants including particulate matter (pm 2.5 and pm 10 ), nitrogen oxides (no x , no and no 2 ), sulfur dioxide (so 2 ), ozone (o 3 ) and carbon monoxide (co) along with meteorological parameters including wind speed, wind direction, temperature and relative humidity were obtained from the cpcb online portal for air quality data dissemination (https://app. cpcbccr.com/ccr/#/caaqm-dashboard-all/caaqm-landing). to understand the overall improvement in air quality, air quality index (aqi) was computed. the details of aqi are available elsewhere (cpcb, 2014; sahu and kota, 2017) , and only briefly summarized here. aqi uses pm 10 , pm 2.5 , no 2 , o 3 , co, so 2 , nh 3 and pb, of which minimum concentrations three pollutants should be available, with at least one being either pm 2.5 or pm 10 . the concentrations are converted to a number on a scale of 0-500. the sub index aqi (aqi i ) for each pollutant(i) is calculated using eq. (1) where, c i is the concentration of pollutant 'i'; b hi and b lo are breakpoint concentrations greater and smaller to c i and in hi and in lo are corresponding aqi values. the overall aqi is the maximum aqi i , and the corresponding pollutant is the dominating pollutant. the aqi is divided into five categories: good, satisfactory, moderate, poor, very poor and severe depending on whether the aqi falls between 0-50, 51-100, 101-200, 201-300, 301-400 and 401-500, respectively. the potential health benefits in different cities due to change in concentrations were estimated using the excess risks associated with the pollutant loads during similar periods with and without lockdown. the relative risks of a pollutant are calculated using eq. (2). where rr i is the relative risk of pollutant i, β i is the exposure-response coefficient indicating the additional health risk (such as mortality) caused by per unit of air pollutant i, when it exceeds a threshold concentration. the β values are 0.038%, 0.032%, 0.081%, 0.13% and 0.048% for m 3 , pm 10 , so 2 , no 2 and o 3 per μg/m 3 respectively, and for co, it is 3.7% per mg/m 3 (hu et al., 2015; shen et al., 2020) . c i,0 is the threshold concentration, meaning that when the concentration of pollutant i is below or equal it has no excess health risk. the excess risk (er) from pollutant i and the total er of all pollutants are estimated using eqs. (3) and (4). 2.3. wrf-aermod modelling system the effect on meteorology on the pm 2.5 concentrations in national capital region (ncr) of delhi was studied using the air quality dispersion modelling system (aermod). required meteorology data was simulated by the weather research forecasting (wrf) model version 3.7.1 with initial and boundary conditions from fnl (final) operational global analysis data on 1.0 × 1.0 degree grids from ncar for every 6 h (http://dss.ucar.edu/datasets/ds083.2/). the 400 × 400 m gridded emissions for delhi-ncr by the safar-indian ministry of earth sciences for 2018 (beig and sahu, 2018) (http://safar.tropmet.res.in/) was used to drive the model. 3.1. variation in meteorology during the analysis period fig. 1 shows the wind rose plot for march 15th to april 14th of 2017, 2018, 2019 and 2020 for five different regions in india. except central india, the wind pattern in most of the years during the analysis period was similar. in north india, south and southwest are the predominant wind direction with average wind speed of~1.5 ms −1 . in southern, eastern and western india, while predominant wind direction was south and southeast, the average wind speeds were~1 ms −1 ,~0.7 ms −1 and 0.8 ms −1 , respectively. however, in central india, even though wind speeds in all the years were similar (~2.1 ms −1 ), wind direction in 2020 (southeast), 2019 (west) and 2018 (southwest) were different. furthermore, there were negligible variations in temperature in different regions during this period. for example, the average temperature in north india was 29.2°c (coefficient of variation~3%). overall, it can be concluded that the meteorology in the analysis period during 2017 to 2020 was similar. fig. 2 shows the temporal change in the average concentrations of the six criteria pollutants in the five regions. overall, around 43, 31, 10, and 18% decreases in pm 2.5 , pm 10 , co, and no 2 were observed during lockdown period compared to the previous years. while there were 17% increase in o 3 and negligible change in so 2 . the higher decrease in pm 10 compared to pm 2.5 could be due to its greater contribution from anthropogenic sources (klimont et al., 2017) . significant decreases in concentrations of pm 2.5 , pm 10 , no and no 2 were observed in north india. for example, compared to an average decrease of 12% in the previous years, pm 2.5 concentration in 2020 decreased by 34%, clearly indicating the effect of lockdown. similar conclusions can be derived for pm 2.5 and pm 10 in other regions. a slight increase in so 2 concentrations was observed in 2020 compared to previous year. this could be due to no restrictions on power plants in northern india and using coal powered energy an essential commodity during lockdown period. a decrease in o 3 was observed in 2020 compared to 2019, while compared to last three years averagely, the concentrations in 2020 were 10% higher. in east india, while there was a decrease in co concentration, an increase in other gaseous pollutants was observed in 2020 compared to 2019. o 3 had 77% increase compared to 2019 and 89% increase compared to the average concentration in 2017 to 2019. in southern india, clear decrease in no, no 2 and o 3 was observed during the lockdown period, while increase in co was observed. increases in o 3 and co and decreases in no and no 2 were observed in central india. most cities in northern, western and southern regions are voc limited (sharma et al., 2016) , thus this increase in o 3 could be due to more decrease in nox compared to voc. furthermore, this could also be attributed to decrease in pm concentrations, which can result in more sunlight passing through atmosphere encouraging more photochemical activities and thus higher o 3 production (dang and liao, 2019; k. li et al., 2019) . excessive risks (er) associated with the criteria pollutants during the lockdown compared to the same period in the previous three years are included in fig. 3 . as per who air quality guidelines (who, 2005) , the threshold values of 25 μg/m 3 (24 hour mean), 50 μg/m 3 (24 hour mean), 100 μg/m 3 (8 hour mean), 200 μg/m 3 (1 hour mean) and 20 μg/m 3 (24 hour mean) for pm 2.5 , pm 10 , o 3 , no 2 and so 2 were considered for t calculation. for co, the recommended air quality guidelines of cpcb, 4 mg/m 3 (1 hour mean), were used. overall, significant health risks due to pm 2.5 and pm 10 were obtained in all the regions even during lockdown period. however, the mean er due to pm reduced by~52% on an average in the country. except so 2 in north india and o 3 in east india, er for all pollutants in every region reduced during lockdown period. this overall reduction in er in india during the lockdown period (~4 times) could save~0.65 million deaths in india in a year. fig. 4 shows the change in aqi and the corresponding dominant pollutant during the analysis period in 22 indian cities. overall, a significant improvement is observed in 2020 during the lock down period in the entire country compared to the previous years. 30% reduction in aqi was observed in the analysis period of 2020 compared to the previous years. about 44, 33, 29, 15 and 32% reductions in aqi were observed in north, south, east, central and western regions. delhi observed the maximum reduction of 49% in aqi. this reduction in aqi was also associated with a change in dominant pollutant in many cities. while in gaya, kolkata, kanpur and nagpur, the dominant pollutant during the lockdown period changed to o 3, it changed to no 2 for agra and patna. this is expected as the maximum reduction was observed for pm 2.5 among all pollutants. correlation between aqi of cities in four different regions, north, east, west and south, during the analysis period is shown in fig. 5 . correlation between cities especially in northern and eastern parts of the country improved in 2020 compared to previous years. for example, the correlation between the largest city in north india, delhi with other cities increased by a factor of 1.9 to 2.8. the best correlation (0.82) between the two central indian cities bhopal and dewas was observed in 2020. this clearly indicates that the increased dominance of regional transport compared to local contributions in the cities during lockdown period. furthermore, this betterment of overall air quality could be due to more dispersion during the pre-monsoon period when this lockdown happened. similar lockdown in china did not result in significant improvement in air quality due to unfavourable meteorology (wang et al., 2020) . to understand this effect, two simulations were carried out. while in simulation 1 the actual meteorology during the analysis period in 2020 was used, in simulation 2 the meteorology pertaining to worst case during early november of 2019 was used (beig et al., 2020) . in both cases the emissions from all sources but energy, residential and windblown dust in delhi ncr was zeroed out to predict pm 2.5 . the model performance in 30 observations stations in the city are shown in table 1 . results indicate that except in eight sites, the mean fractional bias (mfb) falls under the usepa criteria of ±0.6 (epa, 2007). the relative change in concentration in simulation 2 compared to simulation 1 is also included in table 1 . in 24 sites an increase in concentration was observed due to unfavourable meteorology. on an average the concentration in simulation 2 in sites with good model performance increased by 33% compared to simulation 1. this indicates that even the meteorology was not favourable, the average daily pm 2.5 concentration in delhi-ncr would increase to 54 μgm −3 , which is less than the cpcb standard (60 μgm −3 ) and 1.13 times more than the corresponding who standard. however, this increase might not be accurate in the air pollution episode during november, even though similar restrictions on human activities are implemented, as the residential emissions increase in north india mainly due to space heating (guo et al., 2017) . the effect of restricted human activities due to the covid-19 pandemic in india since mid-march of 2020 was studied by analysing concentrations of six criteria pollutants during march 16th to april 14th from 2017 to 2020 in 22 cities covering different regions. among all pollutants, pm 2.5 had maximum reduction in most regions. in contrary, in most regions an increase in o 3 was observed, which could be due to the decrease in pm in addition to decrease in nox. this substantial reduction in concentrations resulted in a 4 times reduction in er. as expected, a significant reduction in aqi was observed in 2020 compared to previous years. however, four cities had o 3 as their dominant pollutant instead of pm 2.5 , suggesting that attention should also be given to decreasing emissions of precursors to secondary pollutants in addition to controlling primary pm. correlation between cities especially in northern and eastern regions improved in 2020 compared to previous years, indicating more significant regional transport than previous years. further analysis on actual and unfavourable meteorology using wrf-aermod modelling system concluded that even the predicted pm 2.5 could increase due to unfavourable meteorology, the average concentration would still be under cpcb limits. this study gives confidence to the regulatory bodies that a significant improvement in air quality in india could be expected if strict execution of air quality control plans is implemented. note: mfb not following the us epa criteria limit was underlined and the values where the concentrations in worst meteorology is lower than base case is shown using italics. the authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. safar-high resolution emission inventory of mega city delhi -2018. moes objective evaluation of stubble emission of north india and quantifying its impact on air quality of delhi radiative forcing and health impact of aerosols and ozone in china as the consequence of clean air actions over 2012-2017 guidance on the use of models and other analyses for demonstrating attainment of air quality goals for ozone, pm2. 5, and regional haze a review of air quality modeling studies in india: local and regional scale source apportionment of pm2. 5 in north india using source-oriented air quality models contributions of local and regional sources to pm2. 5 and its health effects in north india characterizing multi-pollutant air pollution in china: comparison of three air quality indices global anthropogenic emissions of particulate matter including black carbon year-long simulation of gaseous and particulate air pollutants in india severe particulate pollution days in china during 2013-2018 and the associated typical weather patterns in beijing-tianjin-hebei and the yangtze river delta regions anthropogenic drivers of 2013-2017 trends in summer surface ozone in china ministry of environmenta, forest and climate change air pollutant levels are 12 times higher than guidelines in varanasi, india. sources and transfer significance of pm2. 5 air quality at the indian capital sensitivity analysis of ground level ozone in india using wrf-cmaq models temporal variations of six ambient criteria air pollutants from 2015 to 2018, their spatial distributions, health risks and relationships with socioeconomic factors during 2018 in china. environ responses of pm2.5 and o3 concentrations to changes of meteorology and emissions in china severe air pollution events not avoided by reduced anthropogenic activities during covid-19 outbreak source apportionment of sulfate and nitrate particulate matter in the eastern united states and effectiveness of emission control programs authors would like to thank the central pollution control board, ministry of environment, forest and climate change (moefcc) and ministry of human resources and development, government of india. key: cord-304490-q9ab1pji authors: iqbal, najaf; fareed, zeeshan; shahzad, farrukh; he, xin; shahzad, umer; lina, ma title: nexus between covid-19, temperature and exchange rate in wuhan city: new findings from partial and multiple wavelet coherence date: 2020-04-22 journal: sci total environ doi: 10.1016/j.scitotenv.2020.138916 sha: doc_id: 304490 cord_uid: q9ab1pji abstract this study attempts to document the nexus between weather, covid-19 outbreak in wuhan and the chinese economy. we employ 24-h daily average temperature, daily new confirmed cases of a covid-19 in wuhan, and rmb exchange rate to represent the weather, covid-19 outbreak, and chinese economy, respectively. the methodology of wavelet transform coherence (wtc), partial wavelet coherence (pwc), and multiple wavelet coherence (mwc) is used to analyze the daily data collected from 21st january 2020 to 31st march 2020. results reveal significant coherence between series at different time-frequency combinations. overall results show the insignificance of an increase in temperature to contain new covid-19 infections. the renminbi exchange rate showed a negative coherence at specific time-frequency spots suggesting a negative but limited impact of the covid-19 outbreak in wuhan on the chinese export economy. our results are contrary to many earlier studies, which show a significant impact of increased temperature in slowing down covid-19 spread. these results can have important implications for economic and containment policy making regarding the covid-19 outbreak. the world is passing through an unprecedented situation as novel corona-virus (covid-19) is sweeping across -massive population of the world recently. the first case was reported in china's wuhan during december 2019, and a statement from who confirmed the novel nature of the virus on 9 th january 2020 (zhu et al., 2020) . within the same month, who declared public health emergency of international concern (pheic) on 29 th january 2020, citing concerns for the response capacity of countries with weaker health systems (sohrabi et al., 2020) . due to the highly contagious nature of covid-19 (r 0 =2-5) and an ever-increasing number of cases in other parts of the world, soon it became a pandemic (liu, gayle, wilder-smith, & rocklöv, 2020) . the total number of confirmed cases and deaths worldwide amount to 2,127,873 and 141,454 respectively at 04:33 hours beijing time on 17 th april 2020, according to data from johns hopkins university. a recent study in madrid suggests that covid-19 may become more contagious along time, implying that r 0 may increase (garcia-iglesias & de cos juez, 2020) . the health impact is severe enough to put more than half of the world's total population under some form of restric tion, while the economic impact is being called worse than the 2008-09 global financial crisis and compared with the great depression of 1930. stock markets around the world have seen a worse decline for decades (baker et al., 2020) . researchers across the globe are struggling to document the nascent knowledge acquired through primary j o u r n a l p r e -p r o o f observation and experience of the situation. efforts on a global scale are being made to know more about this virus and to slow down and ultimately stop the spread of this menace. figure 1 shows the daily time trend of new confirmed cases in wuhan city. [ insert figure 1 here] a sudden huge increase in new cases on 13 th february 2020 is due to the inclusion of new criterion (clinical symptoms) in detecting confirmed covid-19 cases. figure 2 showing the map where the coronavirus originated. novel corona-virus belongs to the family of severe-acute-respiratory-syndrome (sars) and bears flu like symptoms. since the weather is a key variable in predicting flu, hence it is likely to be an important factor for covid-19 too (sajadi et al., 2020) . since severe cold, wind speed and rain (weather variables) are expected to contribute to flu, cold, fever, cough and pneumonia etc. all of which are possible symptoms of covid-19, it is imperative to know how weather is associated with daily new confirmed infections of covid-19 in wuhan during this outbreak. figure 3 displays the 24-hourly daily average temperature of wuhan city. covid-19 has severely restricted peoples' mobility and disturbed routine-life-activities of almost more than half of the world population. in this scenario, the negative economic impact of this disease is imminent, especially in the country where it was reported first (china) and which is also amongst the worst affected (82,341infected and 3,352 dead till 17 th april 2020). as china is a production house of the world and a major portion of its gross domestic product (gdp) depends on exports, the renminbi (rmb, chinese currency) exchange rate is expected to be also affected (feng, li, & swenson, 2016) . due to lockdown in hubei (central chinese province of which wuhan is the capital), the movement of people and goods to and from this place was completely halted. due to the novel nature of covid-19, it became difficult to ascertain if the virus could be spread through goods transport or not. in this uncertainty, other countries felt reluctant to allow chinese made products to enter their borders. production had already suffered due to complete lockdown in a whole province and then reduced demand overseas added further to declining exports in china. all these factors can affect the exchange rate of rmb, which is primarily linked to foreign trade flows (li, ma, & xu, 2015) . in such a scenario, it is interesting to know how the chinese rmb exchange rate moved with the emerging situation of the covid-19 outbreak, explicitly speaking the number of new daily confirmed cases in wuhan during this period. figure 4 shows the daily time trend of the rmb exchange rate against usd. this study attempts to document the relationship between local weather (temperature), economy (exchange rate of rmb), and covid-19 outbreak (daily number of new confirmed covid-19 cases) in the chinese city of wuhan where it was first reported, using wavelet analysis. as it is an emerging situation, the research on different aspects of this global outbreak is still naive at the moment. soon after reporting of early cases of covid-19, it is established that human-to-human transmission is taking place lai, shih, ko, tang, & hsueh, 2020) . temperature is an important factor in infectivity reduction of the human coronavirus (lamarre & talbot, 1989) . experience with sars had demonstrated that the disease disappeared in warm weather during late july (wallis & nerlich, 2005) . similar behavior has been expected by some in the case of covid-19, also due to its relationship with the same family i.e., corona-virus (wilder-smith, chiew, & lee, 2020). temperature and humidity is an important factor in the survival of coronavirus on metal and other surfaces (casanova, jeon, rutala, weber, & sobsey, 2010) . higher humidity, lower temperature and tropical areas were found to be more feasible for the coronavirus spread during sars outbreak (chan et al., 2011) . a recent study finds an association between meteorological factors, air pollutants and number of deaths in wuhan during covid-19 outbreak using the generalized additive model (ma et al., 2020) . weather is found to be associated with the daily number of covid-19 cases in the indonesian capital city of jakarta also (tosepu et al., 2020) . research studies on the sars outbreak found that daily infections could increase as higher as 18.18 times at low temperatures as compared to high temperatures (merlo et al., 2006) . a study involving 429 cities around the world suggests that temperature may be an important factor in covid-19 infection and transmission and regions with similar weather conditions as of wuhan should be extra cautious in preventing an outbreak . the same study suggests that there may be the best temperature for covid-19 transmission and low temperature is more feasible for this infection and transmission. another research, including data from all cities of china suggests that increase in temperature leads to increase in doubling time of covid-19. this implies that high temperatures may reduce the speed of transmission of covid-19. although the model from this study explains only 18% of the variation in doubling time of covid-19 cases, it still provides an important insight into how temperature can play a role in the containment of this outbreak (oliveiros, caramelo, ferreira, & caramelo, 2020 ). while the above mentioned studies suggest a decisive role of increased temperature in reducing covid-19 spread, the current spread around southern hemisphere suggests there may be only little if any role of temperature in this regard. according to research on global scale, high temperature does not seem to slow down the covid-19 spread (jamil, alam, gojobori, & duarte, 2020) . another study on community outbreaks j o u r n a l p r e -p r o o f throughout the world suggests that covid-19 is a seasonal respiratory virus, spreading along similar latitude (sajadi et al., 2020) . in this uncertain situation where literature is inconclusive about the role of temperature in the covid-19 spread, we attempt to analyze the number of daily new covid-19 cases and average daily temperature in this regard. a better-modeled association helps to understand the behavior of this disease in varying weather conditions which can ultimately help to save precious human lives by taking preventive measures. what has happened in wuhan is important for the rest of the world to know to enable them to making informed and better decisions related to covid-19 containment. a recent study cited measures taken in wuhan as a model to contain the covid-19 elsewhere in the world (m. . a few recent studies confirmed the negative impact of the covid-19 outbreak on the chinese economy during its early stages (al-awadhi, al-saifi, al-awadhi, & alhamadi, 2020; mckibbin & fernando, 2020) . the chinese economy is export-oriented, and significant changes in exports due to covid-19 can affect its exchange rate. a lot of research is available on the relationship between the exchange rate and exports of a country, especially in the case of china (burdekin & willett, 2019; taylor, 2016) . a lot of studies conclude a positive relationship between the depreciation of rmb and chinese exports (park, yang, shi, & jiang, 2010) while others are inconclusive (cheung, chinn, & qian, 2012) . however, the current situation may be different as compared with the classical exchange-rate-exports relationship due to its novel nature. in the ongoing scenario, the rmb exchange rate is expected to show some coherence with the covid-19 outbreak, both directly and indirectly. weather is represented by "average daily temperature" in wuhan and calculated by taking 24-hourly local observations and then averaging throughout every day. covid-19 outbreak is represented by the "number of daily new confirmed infections" of covid-19 and the numbers are taken from national health commission of china's official website. data on chinese exchange rate v/s us dollar is taken from imf website. all data values are collected on daily basis from 21 st january 2020 (lockdown start date of wuhan city) to 31 st march, 2020. we have employed continuous wavelet transform (cwt), wavelet transform coherence (wtc), partial wavelet coherence (pwc) and multiple wavelet coherence (mwc) to analyze the association between the average daily temperature of wuhan, number of daily new confirmed covid-19 cases in wuhan city and rmb exchange rate. wavelet methodology is used mostly in geophysics and recently j o u r n a l p r e -p r o o f getting footprints in weather, environment, economics, and finance studies also (afshan, sharif, loganathan, & jammazi, 2018; ng & chan, 2012 ; wu, tan, guo, li, & chen, 2019) . it can capture non-linear association between multiple series of data (benhmad, 2012) . such methodology has not been employed in any studies related to covid-19 up to the best of our knowledge till now. there are several advantages of using wavelet methodology in multiple time series analysis; 1) assumption of stationarity can be relaxed. 2) a series with non-normal distribution can be used. 3) events localized in time can be captured efficiently. 4) analysis is done from a time-frequency perspective. 5) its very efficient in capturing non-linear relationships (which is the case most frequently in real world scenarios). 6) it can determine strength and direction of association and distinguish between short, medium and long term relationships at the same time. 7) different types of wavelet functions can be used depending upon the nature of data which allows more efficient and accurate tracking of the association. 8) it can capture bi-directional (lead-lag) relationship at the same time at different time-frequency domains between two time series (grinsted, moore, & jevrejeva, 2004; ng & chan, 2012; vacha & barunik, 2012) . the mathematical equation for wavelet transforms coherence is presented below; (1) the wavelet coherence ranges from 2 0 ( , ) 1 r m n  . zero means no coherence at all and one means perfect coherence. the method of monte carlo simulation is employed. in this methodology, the coherence is studied between two variables while controlling for the common effects of third variable. the mathematical representation of this method is given as under; the simplest way of understanding multiple wavelet coherence to compare it with multiple correlation. in this method, coherence is studied between one dependent variable y and the combination of two other x1 and x2 variables. the mathematical representations of mwc is shown below; ; descriptive statistics show that average number of daily cases of covid-19 is 704.31, ranging from minimum "0" to maximum 12,523 during our observation period. average daily temperature is 10.7 degree celsius, ranging from a minimum of 3 degree to a maximum of 21 degree centigrade. exchange rate average is rmb 6.99 per usd fluctuating between 6.90 and 7.115 which shows limited variation (maximum 3%) during this period. correlation between all three variables is positive and significant at the 1% level. coefficient for correlation is 0.61 between covid-19 and temperature, 0.56 between covid-19 and exchange rate and 0.53 between temperature and exchange rate respectively. inside from the light ones outside is called "cone of influence" and represents essential "edge effects" along its borders. figure 5(b) shows the significant variations in temperature that can be seen in frequency bands of 0-4, 4-8 and 8-16 during 3 rd , 3 rd -4 th and 8 th , and 3 rd -6 th weeks of observation respectively represented by an "l" and a long oval shaped dark red contours. can be interpreted as a correlation that is loca lized in time-frequency domain in simple terms but possesses many advantages as compared to simple correlation (grinsted et al., 2004) . the direction of clusters of small arrows observed in the figure 6(b), represents the direction of association between covid-19 and temperature while the colored bar on the right side tells us the strength of this association. arrows pointing towards right side mean a positive association (in phase) between these variables while negative (out phase) towards the left. arrows inside the circle (contour) mean a significant association. rightward direction of arrows inside the contour represents positive association between temperature and covid-19 in frequency band of 8-16 periods during third week of observation. red color inside the circle matches with a correlation of almost 0.80 which is shown on the colored bar on the right side representing a strong association. black cone shape lining from top to bottom on both sides is called "cone of influence" and represents significance level. temperature and exchange rate are in phase as shown by the arrows point ing towards right in the circle shown on the base of the figure 6(c) inside the cone of influence. red color inside is matching with almost 0.80 shown on the colored bar on the right which means a strong association in the frequency range of 16 and onwards during 4 th and 5 th week of observation. there are notable edge effects also in the same frequency band before and after 4 th and 5 th week. there is another very small cluster of arrows j o u r n a l p r e -p r o o f pointing left and downwards in the frequency range of 0-4 periods during 2 nd week which implies an out-phase association running from exchange rate to temperature. figure 7a-1 shows result of partial wavelet coherence (pwc) involving covid-19, temperature and exchange rate. it shows wavelet coherence between covid-19 and temperature while controlling for exchange rate. one small and the other large red colored contour can be observed in frequency domain of 0-4 and 8-16 periods respectively showing short and long term coherence within the given time period. short term coherence is observed during 1st week while long term between 2nd and 3rd week of the observation. red color inside contour matches with almost 0.80 on the colored bar on the right side of the figure showing a strong association. if we compare this result with wtc result of covid-19 and temperature from figure 6a, both are almost same. this implies that exchange rate has no significant impact on the relationship between covid-19 and temperature and results of wtc show true coherence between covid-19 and temperature. mwc shows how good the linear combination of independent variables co-moves with a dependent variable. figure 7a -2 presents result of mwc involving covid-19 as dependent while temperature and exchange rate as independents. linear combination of both independent variables explains variation (small and large red circles with black outlining) in covid-19 in almost all frequency bands including 0-4, 4-8, 8-16 and 16 to onwards during 1 st , 3 rd -4 th , 2 nd -3 rd and 4 th -5 th weeks of observation respectively. figure 7b-2 shows mwc results of temperature as dependent while exchange rate and covid-19 as independent variables. here also red colored islands with black outline can be observed in all frequency bands including 0-4, 4-8, 8-16 and onwards during 1 st -2 nd and 9 th , 3 rd , 3 rd -4 th and 5 th week of observation respectively. these small and large red colored contours show the strength of combination of exchange rate and j o u r n a l p r e -p r o o f covid-19 in predicting temperature. the more red the color, the more the variation can be explained in temperature by the combination of exchange rate and covid-19. figure 7c-2 shows mwc results involving exchange rate as dependent while temperature and covid-19 as independent variables. two small circles can be observed in the frequency band of 0-4 during 2 nd and last week of observation respectively while a large red circle in frequency band of 16 and above during 4 th and 5 th week of observation. these red areas show the association between exchange rate and a linear combination of temperature and covid-19 in that particular time-frequency space. average daily temperature of wuhan shows a positive (in phase) coherence with daily new number of covid-19 cases in medium term considering the given observation time period. this suggests that increase in temperature did not play any significant role in reducing the covid-19 spread in wuhan. this result is contrary to a lot of other studies suggesting that increase in temperature may help to contain covid-19 spread. our results are applicable for a temperature range between 3 degree and 21 degree centigrade which is the minimum and maximum temperature observed during the observation period. although exchange rate and covid-19 show a significant negative (out phase) coherence for a short period of time during 4 th and 5 th weeks of observation, the impact of covid-19 on rmb exchange rate is not very large. the mwc results downplay any huge combined impact of covid-19 and temperature on rmb exchange rate suggesting little impact on chinese exports during the observation period. overall results show a significant co movement and coherence between covid-19, exchange rate and weather in wuhan. although wavelet analysis is relatively new and better than correlation and many other time series techniques from many aspects as stated above in methodology section, results from this approach still need a caution in interpretation while talking about causality. in absence of any sound economic/scientific/social theory, there may not be any causation and data may show correlation and co-movements merely. modeling nonlinear granger causality between the oil price and us dollar: a wavelet based approach china's global interdependence: international reserves, capital inflows, financial market transmission, and exchange rate determination effects of air temperature and relative humidity on coronavirus survival on surfaces the effects of temperature and relative humidity on the viability of the sars coronavirus clinical characteristics and intrauterine vertical transmission potential of covid-19 infection in nine pregnant women: a retrospective review of medical records are chinese trade flows different 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in multilevel logistic regression to investigate contextual phenomena geophysical applications of partial wavelet coherence and multiple wavelet coherence role of temperature and humidity in the modulation of the doubling time of covid-19 cases exporting and firm performance: chinese exporters and the asian financial crisis temperature and latitude analysis to predict potential spread and seasonality for covid-19 world health organization declares global emergency: a review of the 2019 novel coronavirus (covid-19) the role of the chinese economy in the world economy: a us perspective correlation between weather and covid-19 pandemic in jakarta co-movement of energy commodities revisited: evidence from wavelet coherence analysis disease metaphors in new epidemics: the uk media framing of the 2003 sars epidemic temperature significant change covid-19 transmission in 429 cities can we contain the covid-19 outbreak with the same measures as for sars? multi-scale relationship between land surface temperature and landscape pattern based on wavelet coherence: the case of metropolitan beijing a novel coronavirus from patients with pneumonia in china j o u r n a l p r e -p r o o f key: cord-322572-wic7n6ia authors: liu, jiangtao; zhou, ji; yao, jinxi; zhang, xiuxia; li, lanyu; xu, xiaocheng; he, xiaotao; wang, bo; fu, shihua; niu, tingting; yan, jun; shi, yanjun; ren, xiaowei; niu, jingping; zhu, weihao; li, sheng; luo, bin; zhang, kai title: impact of meteorological factors on the covid-19 transmission: a multi-city study in china date: 2020-07-15 journal: sci total environ doi: 10.1016/j.scitotenv.2020.138513 sha: doc_id: 322572 cord_uid: wic7n6ia the purpose of the present study is to explore the associations between novel coronavirus disease 2019 (covid-19) case counts and meteorological factors in 30 provincial capital cities of china. we compiled a daily dataset including confirmed case counts, ambient temperature (at), diurnal temperature range (dtr), absolute humidity (ah) and migration scale index (msi) for each city during the period of january 20th to march 2nd, 2020. first, we explored the associations between covid-19 confirmed case counts, meteorological factors, and msi using non-linear regression. then, we conducted a two-stage analysis for 17 cities with more than 50 confirmed cases. in the first stage, generalized linear models with negative binomial distribution were fitted to estimate city-specific effects of meteorological factors on confirmed case counts. in the second stage, the meta-analysis was conducted to estimate the pooled effects. our results showed that among 13 cities that have less than 50 confirmed cases, 9 cities locate in the northern china with average at below 0 °c, 12 cities had average ah below 4 g/m(3), and one city (haikou) had the highest ah (14.05 g/m(3)). those 17 cities with 50 and more cases accounted for 90.6% of all cases in our study. each 1 °c increase in at and dtr was related to the decline of daily confirmed case counts, and the corresponding pooled rrs were 0.80 (95% ci: 0.75, 0.85) and 0.90 (95% ci: 0.86, 0.95), respectively. for ah, the association with covid-19 case counts were statistically significant in lag 07 and lag 014. in addition, we found the all these associations increased with accumulated time duration up to 14 days. in conclusions, meteorological factors play an independent role in the covid-19 transmission after controlling population migration. local weather condition with low temperature, mild diurnal temperature range and low humidity likely favor the transmission. • the impacts of meteorological factors on covid-19 case counts were assessed after controlling population migration. • the weather with low temperature, mild diurnal temperature range and low humidity likely favor the transmission of covid-19. • the epidemic might gradually ease partially due to rising temperatures in coming months. the purpose of the present study is to explore the associations between novel coronavirus disease 2019 (covid-19) case counts and meteorological factors in 30 provincial capital cities of china. we compiled a daily dataset including confirmed case counts, ambient temperature (at), diurnal temperature range (dtr), absolute humidity (ah) and migration scale index (msi) for each city during the period of january 20th to march 2nd, 2020. first, we explored the associations between covid-19 confirmed case counts, meteorological factors, and msi using non-linear regression. then, we conducted a two-stage analysis for 17 cities with more than 50 confirmed cases. in the first stage, generalized linear models with negative binomial distribution were fitted to estimate city-specific effects of meteorological factors on confirmed case counts. in the second stage, the meta-analysis was conducted to estimate the pooled effects. our results showed that among 13 cities that have less than 50 confirmed cases, 9 cities locate in the northern china with average at below 0°c, 12 cities had average ah below 4 g/ wuhan, the capital city of hubei province, china, was the first major metropolitan region suffering from the coronavirus disease 2019 outbreak and the epidemic center since december, 2019 (zhou et al., 2020) . covid-19 is caused by the severe acute respiratory syndrome coronavirus 2 (sars-cov-2), a novel coronavirus. due to the high contiguousness and wide spread, covid-19 has officially been declared a pandemic by the world health organization (who) on march 11, 2020 (world health organization, 2020b). as of march 21th, more than 170 countries has reported this epidemic, with a total diagnosed cases of about 234,073 causing over 9000 deaths (world health organization, 2020b) . europe and the united states have gradually becoming the epicenter of the pandemic (world health organization, 2020c) and the world is facing great public health crisis from covid-19, which is likely more severe than sars in 2003. in china, covid-19 has spread in multiple major cities that have huge numbers of both inbound and outbound passengers (e.g., beijing, shanghai, and guangzhou) (wu et al., 2020) . to block the quick spread of infection and control the severe epidemic, china has conducted strict measures by mobilizing and redistributing nationwide resources, shelter-in-place and quarantining all confirmed cases and close contacts. a study indicated that a series of control measures since january 23, 2020 in china reduced the covid-19 epidemic size significantly, and the similar measures were expected to remain until the end of april 2020 (yang et al., 2020) . the current daily new covid-19 cases in china have reached very low level. china has cumulatively reported more than 81,008 confirmed cases and over 3,255 deaths as of march 21, 2020 (national health commission of the people's republic of china, 2020). among all these effective strategies in controlling this epidemic, locking down wuhan, a city of 11 million residents, was one of the most dramatic measures. it turned out that the limitation of population migration was effective in controlling epidemic diseases like covid-19. however, the independent effect of meteorological factors on the transmission of covid-19 has not been studied systemically while controlling population migration. previous studies showed that cold and dry weather is beneficial for the survival and spread of droplet-mediated viral diseases like influenza (lowen et al., 2007; shaman and kohn, 2009; li, 2011) . the sars epidemic was gradually faded with the warming weather coming, and was basically ended in july, 2003 (tan et al., 2005; wang et al., 2006; cao et al., 2016) , suggesting that the temperature and its variations might have affected the sars outbreak. some studies have suggested that the climate change might have contributed to various infectious diseases emergence and spread (lofgren et al., 2007; gale et al., 2010; stott, 2016) , including the sars and covid-19. in korea, researchers found that the risk of influenza incidence was significantly increased with low daily temperature and low/high relative humidity (rh), but a positively correlated with diurnal temperature range (dtr) (park et al., 2020) . absolute humidity (ah) had significant correlations with influenza viral survival and transmission rates (shaman et al., 2010; shaman et al., 2011) . one important feature of covid-19 epidemic is that the countries currently suffering most from the disease are most located in the regions with low temperature. therefore, meteorological factors, such as ambient temperature (at) and humidity, might play an important role in the spread of the disease. many factors might influence the covid-19 epidemic, including social and political factors, geographical factors, climatic factors, etc. (casadevall, 2020; wu et al., 2020) . when only considering the temperature in single-factor model in the higher-temperature group, every 1°c increase in the minimum temperature leads to a decrease of the cumulative number of covid-19 cases by 0.86 . luo etc. reported that weather was related to the spread of covid-19, but the increase of temperature may not necessarily lead to declines in case counts without the implementation of extensive public health interventions (luo et al., 2020) . in another study, researchers estimated that the weather variables explain 18% of the variation in disease doubling time, and the remaining 82% may be related to containment measures, general health policies, population density, transportation or cultural aspects (oliveiros et al., 2020) . because of the human to human transmission, the migration should be considered when evaluate the effects of meteorological factors over covid-19 transmission. however, to our knowledge, previous studies have not controlled the population migration to examine independent effects of weather conditions on the covid-19 transmission. in this study, we first explored non-linear relation between covid-19 case counts and meteorological factors. then we used generalized linear models to examine the associations between meteorological factors and covid-19 daily case counts in 30 provincial capitals except for wuhan in china while controlling the population migration. since the covid-19 condition was much more complicated compared with other provinces due to government interventions in hubei, like wuhan lockdown and mass screening, we chosen to study the relationship in 30 capital cities of china. we obtained daily officially reported confirmed case counts from the health commission of the 30 capital cities except wuhan during the period january 20th to march 2nd 2020 (fig. 1 ). the daily meteorological data, including hourly temperature and rh, were obtained from shanghai meteorological bureau and data center of ministry of ecology from january 5th to march 2nd 2020. meanwhile, migration scale index (msi) of the 30 cities was collected from the website of baidu migration (https://qianxi.baidu. com/?from=mappc). msi reflects the population scale of moving in, and msi of cities can be comparable. the daily average at and dtr were calculated based on hourly data. ah was calculated according to the method used in the previous study which was measured by vapor pressure (g/m 3 ) (shaman et al., 2011; davis et al., 2016; liu et al., 2018) . a descriptive analysis was performed to explore the city-specific characteristics of confirmed case counts, at, dtr, ah and msi of these 30 cities. for each city, average meteorological data were calculated based on the period of january 20th to march 2nd, 2020 to account for the lag effect and the latent period of covid-19. then, a second order polynomial non-linear regression models were fitted between total covid-19 confirmed case counts and at, dtr, ah, msi. we characterize the disease transmission and case distribution in the 13 cities with less than 50 confirmed cases. then, a two-stage analysis was conducted for the other 17 cities with more than 50 cases in each city. in the first stage, because of the clustering characteristics of the disease, we adopted generalized linear models with negative binomial distribution to estimate city-specific effects. the analyses were performed with r software version 3.3.2, and the "mass" package (mass: support functions and datasets for venables and ripley's mass, 2019) was used to fitting models. the fitted formulas were as follows: where t is the day of the observation; e(y t ) is the expected number of daily confirmed cases on day t; α is the intercept; β is the regression coefficient. considering the lag effects and the average latent period of covid-19, 3-day moving average rh and 3-day moving average msi were controlled in the models when exploring the effects of at (1) and dtr (2). as a meteorological factor, natural cubic splines (ns) with 3 df was used for controlling rh. considering the collinearity, only three-day moving average msi were controlled in the models (3) when dealing with ah. because of the lag effects, we evaluated the associations in lag 0, lag 03, lag 07 and lag 014 between daily confirmed case counts and these meteorological factors for each city. in the second stage of the analysis, we conducted a random effects meta-analysis to pool estimates across city-specific associations. the meta-analysis was performed based on stata/se 11.0 (statacorp llc, usa). all results were expressed as the relative risk (rr) in daily confirmed case counts with 95% confidence intervals (95% ci) relative to a fixed change (1°c or 1 g/m 3 ) of each factor. statistical significance was set at p-value b 0.05. as of march 2nd, 2020, a total of 3,905 cases were officially reported in 30 provincial capital cities in china. among these cities, 17 cities had more than 50 confirmed cases, accounting for 90.6% of all cases in this study. during our study period, the daily msi, at, dtr and ah for these 30 cities were 1.62 ± 1.14, (3.44 ± 7.97)°c, (9.13 ± 3.04)°c and (4.76 ± 3.14) g/m 3 . strong regional differences were observed for meteorological factors and msi. among the 13 cities that have less than 50 cases, 9 cities located in the northern china with average at below 0°c, 12 cities had average ah below 4 g/m 3 and one city (haikou) had the highest ah (14.05 g/ m 3 ) (figs. 1, 2 and table 1 ). the msi in these 13 cities were relatively lower than the remaining 17 cities that have more than 50 cases (fig. 2) . the nonlinear regression analysis results (fig. 3) suggest brief distribution characteristics between confirmed case counts and at, dtr, ah, msi. we found an obvious trend association between at and the confirmed case counts, it seemed that the confirmed case number increased with temperature increasing in the range of −20°c-20°c. like that, similar trend was also found between confirmed case counts and msi. well, we found there was an arched shape for the relationship between confirmed case counts and period-average ah, as there were more confirmed cases at the ah of around 6 g/m 3 . however, the regression model showed that the confirmed cases counts declined with the increase of dtr in the range of 5°c-15°c. concerning the small sample size in those 13 cities, the fitted cityspecific generalized linear models and meta-analysis were only conducted for the 17 cities with 50 and more cases to explore the associations between covid-19 case counts and meteorological factors (fig. 4) . in city-specific analysis, significant negative associations were found in 9 cities (beijing, tianjin, zhengzhou, hangzhou, shanghai, xian, nanchang, fuzhou and guangzhou) in lag 03. in meta-analysis, the pooled results showed that each 1°c increase in at was related to the decline of daily confirmed covid-19 case counts, the corresponding overall rr was 0.80 (95% ci: 0.75, 0.85) (fig. 4a ). each 1°c increase in dtr was associated with decreased patients in lag 03 and the pooled rr was 0.90 (95% ci: 0.86, 0.95). in the city level, it was significant for hangzhou, nanchang, fuzhou, chengdu and zhengzhou in lag 03 (fig. 4b ). as showed in fig. 4c , ah had significant negative effects on confirmed case counts for 4 cities, including guangzhou, hangzhou, nanchang, and nanjing. meta-analysis showed that each 1 g/m 3 increase in ah was significantly associated with reduced confirmed case counts for 17 cities cities in lag 07, lag 014 and the combined rr was 0.72 (95% ci: 0.59, 0.89) and 0.33 (95% ci: 0.21, 0.54). fig. 4d showed associations between confirmed case counts and at, dtr and ah in lag 0, lag 03, lag 07 and lag 014. the pooled effects of at, dtr and ah became stronger with the increase of cumulative lag days. as of march 2nd, china has reported 80, 302 covid-19 cases. this is the first study to examine the impact of meteorological factors on covid-19 after controlling population migration. our results indicated that covid-19 transmission may be affected by meteorological factors, and a weather with low temperature, mild diurnal temperature range and low humidity likely favor its transmission. our findings on the impact of meteorological conditions over the transmission of covid-19 are consistent with previous studies on the transmission of sars or other infectious diseases (tan et al., 2005; lin et al., 2006; liu et al., 2018; park et al., 2020) . some studies suggested that global climate change might be accompanied by the changes to the outbreak of infectious diseases (bezirtzoglou et al., 2011; anwar et al., 2019; casadevall, 2020) . as we know, viruses are completely dependent on their hosts for replication and survival. it is possible that as virus has adapted to gradually higher global at, some new and previously unknown infectious diseases are likely to emerge and spread (casadevall, 2020) , such as sars-cov and ebola virus, and poses a threat to human health. the emergence and spread of novel coronavirus since december 2019 might be related to the ongoing climate change. in winter and spring, a decrease in resistance to respiratory diseases in a colder environment for population might be easier to accelerate the spread velocity. lin etc. showed that in days with a lower air temperature during the epidemic, the risk of increased daily incidence of sars was 18.18-fold (95% ci: 5.6, 58.8) higher than in days with a higher temperature (lin et al., 2006) . tan etc. found a close association between temperature, its variations and the sars outbreak in the four cities in china, suggesting that sars more likely outbreaks in spring (tan et al., 2005) . consistent with these results, we also found that each 1°c increase in at was related to the decline of daily confirmed case counts, the corresponding overall rr was 0.80 (95% ci: 0.75, 0.85). in addition, lambrechts etc. has found that a large dtr might impede dengue virus infection of the mosquito midgut and reduce transmission risks compared to a small dtr or constant temperature. intensity of dengue virus transmission can be influenced by the specific combination of mean and range in temperature fluctuations (lambrechts et al., 2011) . in our study, each 1°c increase in dtr was associated with decreased (d) pooled estimates in lag 0, lag 03, lag 07 and lag 014. the associations of covid-19 case counts with at, ah and dtr in each city was evaluated by fitting generalized linear models respectively (lag 03). the meta-analysis was conducted to combine the city-specific results. at: ambient temperature; dtr: diurnal temperature range; ah, absolute humidity. patients in lag 03 and the pooled rr was 0.90 (95% ci: 0.86, 0.95). this suggests that novel coronavirus might be also more suited to survive in an environment with small dtr or constant temperature. ah is an indicator describing the mass of water vapor per volume of air (g/m 3 ). shaman et al. found that 50% of influenza virus transmission variability and 90% of influenza virus survival variability could be explained by ah variation, whereas, only 12% and 36% could be explained by relative humidity (shaman and kohn, 2009) , and the epidemic influenza typically peaks in the winter when low ah maximizes r0 (shaman et al., 2011) . a previous study found that ah was one of most important weather parameters in predicting heat-related mortality among a spectrum of weather parameters (zhang et al., 2014) . these studies indicated that ah may be a better indicator of humidity in acute health effects. the covid-19 outbreak in china happened in winter and early spring with lower ah. our results indicated that there might exist an optimum low humidity for covid-19 to spread. because those 12 cities with ah below 4 g/m 3 confirmed fewer case counts than other cities. for the 17 cities with more than 50 cases, results showed that every 1 g/m 3 increase in ah was significantly associated with declined confirmed case counts in lag 07, lag 014 and the combined rr was 0.72 (95% ci: 0.59, 0.89) and 0.33 (95% ci: 0.21, 0.54). consistent with our results, liu et al. has explored the effects of ah on h7n9 infection risks in china and found significantly higher effects of low ah on risks of h7n9 infection (liu et al., 2018) . possible explanation is that low ah might increase the stability of coronavirus and favor its transmission like influenza did (lowen et al., 2007) . our results are somewhat different from a previous study about early covid-19 outbreak, which reported that the changes in temperature and humidity as spring and summer months arriving might not lead to decline of confirmed case counts without the implementation of extensive public health interventions (luo et al., 2020) . although public health control measures play a major role in controlling pandemic like covid-19, our results indicate an independent role of weather conditions on the transmission. unlike this study, we used data over a longer period and controlled the population migration in our models. therefore, we are optimistic that this epidemic will be faded to a large degree in the coming warmer season with the enforcement of public health interventions in china. as we know, the covid-19 in china firstly confirmed in wuhan and a considerable proportion of confirmed cases in other cities of china were imported from wuhan, which may confuse the relation of meteorological environment and covid-19. however, we controlled its effect with msi and estimated a significant association between the meteorological environment and covid-19 transmission. the most important environmental implication is that, at, dtr and ah are critical factor for covid-19 transmission, which also deserve to be better studied in other regions during this pandemic. in conclusions, our study implicates that meteorological factors play an independent role in the covid-19 transmission. a weather with low temperature, mild diurnal temperature range and low humidity favors the transmission. this study indicates that the epidemic might gradually ease as a result of rising temperatures in coming months as well as the implementation of public health control measures. the authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. climate change and infectious diseases: evidence from highly vulnerable countries climate changes, environment and infection: facts, scenarios and growing awareness from the public health community within europe analysis of spatiotemporal characteristics of pandemic sars spread in mainland china climate change brings the specter of new infectious diseases humidity: a review and primer on atmospheric moisture and human health assessing the impact of climate change on vector-borne viruses in the eu through the elicitation of expert opinion impact of daily temperature fluctuations on dengue virus transmission by bemnaedes aegyptib/em&gt environmentally mediated transmission models for 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factors for mortality of adult inpatients with covid-19 in wuhan, china: a retrospective cohort study this work was supported by the novel coronavirus disease science and technology major project in gansu province. key: cord-336659-qddjqiw9 authors: ramos, jheneffer sonara aguiar; pedroso, thays millena alves; godoy, fernanda ribeiro; batista, renata elisa; de almeida, frankcione borges; francelin, carolina; ribeiro, francis lee; rocha-parise, michelle; de melo e silva, daniela title: multi-biomarker responses to pesticides in an agricultural population from central brazil date: 2020-08-21 journal: sci total environ doi: 10.1016/j.scitotenv.2020.141893 sha: doc_id: 336659 cord_uid: qddjqiw9 abstract we evaluated farmworkers exposed to pesticides and individuals with no history of occupational exposure to pesticides. it was performed the comet assay to evaluate dna damage. the immunophenotyping of tcd4+ lymphocyte subpopulations in peripheral blood was performed by flow cytometry. the single nucleotide polymorphisms (snps) in pon1, xrcc1, il6, il6r, tnf-α, and mir137 genes were evaluated by real-time pcr. the exposed group was composed mostly by males (69.44%), with direct exposure to pesticides (56%) and with an average age range of 46 ± 13.89 years, being that 58.3% of farmworkers directly exposed to pesticides and reported the full use of personal protective equipment (ppe). dna damage was greater in the exposed group (p < 0.05), reinforced by the use of ppe to denote a lower degree of dna damage (p = 0.002). in this context, in the exposed group, we demonstrated that the use of ppe, age, gender and intoxication events were the variables that most contributed to increase dna damage (p < 0.0001). besides, the exposed group showed a significant increase in the subpopulations of t lymphocytes cd3+ cd4+ (p = 0.04) and cd3+ cd4+ cd25+ (p < 0.0001). snps in the tnf-α (rs361525) gene presented a difference in the genotype distribution between the groups (p = 0.002). the genotype distribution of tnf-α (rs361525) was also positively correlated with the dna damage of the exposed group (r = 0.19; p = 0.01), demonstrating a higher risk of dna damage in the farmworkers presenting the a mutated allele. our findings demonstrate that pesticides can exert various deleterious effects on human health by damaging the dna as well as by influencing the immune system in the case of both direct or indirect exposure and these issues are associated to age, gender, intoxication and the nonuse of ppe. pesticides have been extensively used globally to increase crop production and quality through controlling pests and for vector-borne diseases. it is noteworthy that brazil is one country that most consume pesticides in the world (marcelino et al. nascimento et al. 2020; paumgartten, 2020) . only in 2019, 439 products were authorized, the most significant number in the last 10 years (brazilian agriculture minister, nascimento et al. 2020 ) and even with the covid-19 pandemic, the brazilian government released 150 new pesticides this year (until may). thus, almost all individuals are exposed to relatively low doses of pesticides due to environmental contamination or intentional use. according to damalas and eleftherohorinos (2011) , at low doses of exposure pesticides do not produce any permanent harmful effects on humans. in this context, agricultural workers and their families and individuals who reside close to fields where pesticides are applied are considered to be the group that will receive the most considerable exposure at the highest risk for adverse health outcomes (gangemi et al., 2016; docea et al. 2017; jacobsen-pereira et al. 2018; godoy et al. 2019; marcelino et al. 2019) . as a result, humans exposed to a complex mixture of pesticides are more likely to develop different diseases due to deleterious effects on immune, hematological, nervous, endocrine, and reproductive systems (corsini et al. 2013; aroonvilairat et al., 2015; campos et al. 2016; corral et al. 2017; docea et al. risk related to the use of pesticides and protect human health (docea et al. 2017; jacobsen-pereira et al. 2018; lozano-paniagua et al. 2018 ; barrón-cuenca et al. 2019; godoy et al. 2019) . the development and validation of new and useful biomarkers to assess pesticide exposure are warranted to implement proper control measures (araoud, 2011; lozano-paniagua et al. 2018) . various in vitro and in vivo studies, as well as epidemiological approaches, have demonstrated that pesticides or their metabolites may result in genotoxic and mutagenic effects (bolognesi, 2003; docea et al., 2017; kapeleka et al., 2019; paumgartten et al., 2020) . therefore, the use of genotoxicity and mutagenicity biomarkers is relevant to provide early identification of biological effects (kapka-skrzypczak et al., 2011; aiassa, 2018; lozano-paniagua et al. 2018) . for assessment of mutagenic and genotoxic pesticide-induced damage, the most widely used methods are sister chromatid exchange assay, chromosomal aberrations test, single-cell gel electrophoresis (comet) assay, and micronuclei test (aiassa, 2018; godoy et al. 2019; kapeleka et al., 2019; marcelino et al., 2019) . data from experimental and epidemiological studies have also demonstrated that exposure to pesticides can modify the immune system either morphologically or functionally contributing to the development of immune-mediated diseases, such as asthma, allergies, type 1 diabetes, thyroid diseases, rheumatoid arthritis and atherosclerosis (gangemi et al., 2016; requena et al. 2019 ; fukuyama and tajiki-same author, in another study (parks et al. 2019) , demonstrated that moderate to higher level of serum antinuclear autoantibodies are associated with the past exposure to some types of pesticides and a history of seeking medical care in male farmers occupationally exposed to pesticides. in general, pesticides can impair immune cells function by inducing oxidative stress, mitochondrial dysfunction, endoplasmic reticulum stress, disruption of the ubiquitin protease system or autophagy, and inhibition of enzymes with esterase activity (corsini et al., 2008; mokarizadeh et al., 2015; fukuyama and tajiki-nishino, 2020) . therefore, the altered immune system may be a sensitive marker of pesticide-induced immunotoxicity, eventually affecting the development of immune-mediated disorders, and so may be predictive of eventual diseases (corsini et al., 2013; fukuyama and tajiki-nishino, 2020) . biomarkers recommended assessing immunotoxicity of pesticides include lymphocyte count, antibody-mediated immunity (serum concentrations of immunoglobulins) analysis, lymphocytes phenotypic analysis by flow cytometry, measurements of autoantibodies and markers of an inflammatory response, among others (rojas-garcía et al., 2011; parks et al. 2019; fukuyama and tajiki-nishino, 2020) . it is also of particular relevance to the the environmental health research to investigate single nucleotide polymorphisms (snps) in inflammatory genes since snps play a critical role in the assessment of the immune response to pesticide play a role in the risks of pesticide-related disease and can also be used as biomarkers associated with susceptibility (gangemi et al., 2016; sisto et al., 2019) . regarding the metabolism genes, snps in cytochrome p450 (cyp), glutathione transferases (including gstm1, gstp1, gstt1), acetyltransferases (nat2), and paraoxonases (mostly pon1) genes have been widely used to evaluate interindividual differences in metabolization and detoxification of pesticides (rojas-garcía et al., 2011; teodoro et al., 2019) . additionally, polymorphisms in dna repair genes, especially those involved in base excision repair, including ogg1 (8-oxoguanine dna glycosylase) and xrcc1 (x-ray repair cross-complementation group 1) can be associated with higher risks of pesticide-related diseases. moreover, gene variants have also been investigated to understand the differences in susceptibility to pesticide exposure (tabrez et al., 2014; teodoro et al., 2019) . hence, the current study evaluated the impact of pesticide exposure on the health of rural workers in the southeast and southwest of goias, brazil, using genotoxicity, immunotoxicity, and susceptibility tests. this is a pioneer study in central brazil involving genetic and immunological biomarkers to identify how pesticides could impair such systems increasing the susceptibility to the development of chronic issues problems. was composed of 100 individuals directly exposed to pesticides (occupationally exposed to various pesticides during storage, mixing, loading, and pesticide spraying activities), and 80 subjects indirectly exposed, living nearby crops, therefore, environmentally exposed to pesticides. the control group consisted of 180 individuals, 125 men, and 55 women, with no direct contact or closer exposure to pesticides, and were matched with the exposed group by age, gender, and lifestyle. it is worth mentioning that we sampled the total blood of the rural workers during the midseason and at the end of a week of application, once we could verify how exposure to such products altered the response of multiple biomarkers. we evaluated dna damage by alkaline single cell gel electrophoresis (comet assay) according to singh et al. (1988) , with a slight modification, mainly in the stained of the slides. briefly, two slides were processed for each individual. ficoll-paque™ plus (density 1.077 g/ml, ge healthcare, uppsala, sweden) following the manufacturer's instructions. briefly, ten milliliters of well-mixed whole blood were for each sample were acquired and analyzed. genomic dna was extracted from whole peripheral blood using the the estimation of genotype and allele frequencies was carried out by direct counting. allele and genotype frequencies were compared between pesticide-exposed j o u r n a l p r e -p r o o f individuals and controls by the χ2 test. we also tested hardy-weinberg equilibrium (hwe). the hardy-weinberg equilibrium is considered the null model of population genetics and serves to test hypotheses about the change in allele and genotype frequencies in populations. in an infinite population, in which matings occur at random and in the absence of evolutionary factors such as natural selection, mutation and gene flow, the allelic and genotype frequencies remain constant throughout the generations, and are, respectively, p and q and p 2 , 2pq and q 2 (mayo, 2008). these analysis were carried out with genepop v. 1.2 (raymond and rousset, 1995) . the p-value was between 1 and 5 percent (p < 0.01 or < 0.05, respectively). the demographic characteristics of the study group are shown in table 1. the exposed and control groups did not differ regarding age, gender, smoking habits, and alcohol consumption. the time of exposure of the exposed group presented a median of 16.3 ± 10.3 years. the use of ppe was described by 58.3% of the farmworkers, while 41.7% reported not using it at all. a total of 37 individuals of the exposed group (20.6%) reported acute pesticide poisoning consisting of 10 indirectly exposed subjects (27%) and 27 directly exposed individuals (73%). of the 27 directly exposed rural workers who were intoxicated, six of them did not use ppe. one hundred (87 men and 13 women) were individuals directly exposed to pesticides and 80 subjects (38 men and 42 women) live nearby crops and, therefore, were environmentally exposed to pesticides. the most frequently self-reported chronic health problems among exposed individuals were high blood pressure (18.9%), allergy (17.2%), diabetes type 2 (11.1%), j o u r n a l p r e -p r o o f journal pre-proof and thyroid disease (4.4%). regarding pesticides and in accordance to the organism they kill (megha et al, 2018), exposed individuals reported frequent use of herbicides (47%) and followed by insecticide (42%) and fungicide (11%). the more commonly used pesticides were glyphosate (40.86%), 2,4-d (15.59%), cypermethrin (10.22%), deltamethrin (8.06%), and atrazine (5.38%). the most common crops were soybean (48%) and corn (34%) crops. dna damage in exposed and controls are described in table 2 . we demonstrated more dna damage in the exposed group compared to the non-exposed group (p < 0.05), independent of the type of exposure (if direct or indirect) [ table 2 ]. no significant difference in the dna damage was observed based on smoking habits and alcohol consumption (p > 0.05). age, gender distribution, the use of ppe and intoxication events showed statistically significant differences in dna damage (p < 0.001), demonstrating considerable dna lesions among older farmworkers, women, individuals that reported intoxication and who did not use ppe [ table 3 ]. we did not find association between time of exposure to pesticides and dna damage (p>0.05). of the 360 individuals, 173 were analyzed by flow cytometry (118 exposed and 55 non-exposed). the individuals in the exposed group showed a significant increase of cd3 + cd4 + (p <0.05) , cd3 + cd4 + cd25 + (p < 0.0001) and cd3 + cd4 + cd25 + foxp3 + (p < 0.05) lymphocytes subpopulations when compared to individuals in the non-exposed group (figure 2a,2b and 2c) . however, the percentage of natural regulatory t cells (cd3 + cd4 + cd25 + foxp3 +) did not differ between the j o u r n a l p r e -p r o o f journal pre-proof groups (p = 0.12) ( figure 2d ). there were no statistically significant correlations between the percentage of tcd4 + cells and tcd4 + cd25 + cells and the percentage of dna in tail (% dna) in the exposed group (r = -0.15; p = 0.25 and r = -0.14; p = 0.13, respectively) [ figure 3 ]. the distributions of all genotypes were in accordance to hardy-weinberg equilibrium. the snps genotyping of pon1 (rs662), xrcc1 (rs25487), il6 (rs1800795), il6r (rs2228145), and mir137 (rs1625579) revealed that there was no statistically significant difference in the genotype and allele distributions among the studied groups (p > 0.05) ( table 4 ). we also did not find that the farmers presenting mutant alleles of pon1 (rs662), xrcc1 (rs25487), il6 (rs1800795), il6r (rs2228145), and mir137 (rs1625579) presented increased dna damage (figure 4 ). however, there was a difference in the snps distribution of the tnf-α (rs361525) gene between the study groups (p = 0.002) [ figure 4 ]. additionally, a significant positive correlation was found between the tnf-α (rs361525) polymorphism and dna damage (r = 0.19; p = 0.01), but we found no correlation between tnf-α (rs361525) and the percentage of dna in tail (% dna) in the control group (r = 0.05; p = 0.47). this is the first study from central brazil that demonstrated how genetic and immune biomarkers are associated to the exposure of a complex mixture of pesticides also, families of farmworkers are often environmentally exposed to multiple pesticides, either by living near crops or by having contact with contaminated clothes and work tools without personal protection (damalas and eleftherohorinos, 2011; parks, 2016; doğanlar et al. 2018 ). in general, farmworkers' families are exposed to lower levels but for a longer duration to pesticides. thereby may be more vulnerable to adverse effects, especially pesticide poisoning (ward et al., 2006; shirangi et al., 2010; parks, 2016) . the chronic diseases reported by pesticide-exposed participants in our study is in agreement with studies performed in similar conditions (directly and indirectly exposition) (mrema et al., 2017; kongtip et al., 2018; barrón-cuenca et al. 2019) . moreover, other epidemiological studies have shown a higher risk of psychiatric problems, in people exposed to pesticidesespecially those who have suffered from journal pre-proof associated pesticide diseases. however, the statistical associations between exposure to certain pesticides and the incidence of some chronic diseases are compelling enough to create concern. besides the chronic effects observed in individuals exposed to pesticides, we also observed an increase in the dna damage of exposed individuals compared to the control group (p < 0.05). previous studies on farmworkers exposed to in agreement with the gender of exposed individuals, women displayed higher levels of dna damage than men (p < 0.001), probably because they are the most actively involved laborers in the crops until harvest, as reported by rekhadevi et al. 2017 and are also responsible for washing their partners' working clothes or male relatives. therefore, women had direct and chronic contact with pesticides and their residues. indeed, comparing genotoxic damage in individuals who reported using full ppe relative to those who did not use ppe or used incomplete ppe demonstrated higher levels of dna damage among the latter group (p < 0.001). we also found increased j o u r n a l p r e -p r o o f journal pre-proof dna damage in older farmworkers and in those that reported intoxication. such findings demonstrated an influence of ppe's effectiveness in preventing the genotoxic effects of pesticides on peripheral blood cells (simoniello et al., 2008) . previous studies have shown the same correlations between ppe use, intoxication, age and gender on level of dna damage and suggested to be due to differences in exposure conditions, dna repair capability and lifestyle factors (simoniello et al., 2008; how et al., 2015; ali et al. 2017; cayir t al., 2019) . according to ali et al. 2017, women from bahawalpur district, of the punjab province, in india, exposed to pesticides while picking cotton with bare hands, presented increased dna damage when compared to controls. besides, the dna damage was positively correlated to age and exposure time, demonstrating that dna repair capability could be committed. on the other hand, our results did not show any influence of smoking habits and alcohol consumption on genotoxic damage. therefore, increased dna damage in the exposed group was due to exposure to pesticides, and not associated with other confounding factors. similar results were also produced by other authors, who found no significant difference between lifestyle and dna damage (simoniello et al., 2008; kaur et al., 2011; wilhelm et al., 2015) , unlike barron-cuenca et al. (2019) and hayat et al. (2019) , which showed an increase of dna damage. moreover, cd4 + lymphocytes subpopulations were also analyzed as a biomarker of alterations on the immune system. our analysis demonstrated significant modifications of immunotoxicity parameters in the exposed group, specifically in the percentages of tcd4 + , t cd4 + cd25 + and tcd4 + cd25 + foxp3 + lymphocytes subsets that indicates that the pesticides evoke an alteration in the cd4 + lymphocytes in the peripheral blood of exposed individuals. however, the percentage of natural regulatory t cells cd3 + cd4 + cd25 + foxp3 + and did not differ significantly between the exposed j o u r n a l p r e -p r o o f and the non exposed groups. our findings are promising as we demonstrate a disturbance in the pattern of tcd4 + lymphocytes subpopulation in front of the pesticide and a maintenance of the natural regulatory t cells percentage. this data strongly suggests that the pesticides evoke a peripheral t cell subpopulation alteration, what is plausible to purpose, would commit further immune reactions. at this moment our group is working to better explore this data. another important issue is individual susceptibility that influences physiological responses to pesticide exposure. therefore, it is essential to identify genotypes that determine the modulation of the proteins involved in the metabolization, detoxification, and dna repair, influencing the heterogeneity of responses to pesticides (oliveira et al., 2019) . regarding susceptibility biomarkers, only tnf-α rs361525 polymorphism showed a significant difference in genotype distributions between exposed and control groups (p = 0.002). tnf-α gene encodes tumor necrosis factoralpha (tnf-α) proinflammatory cytokine that is enhanced by the oxidative stress pesticide-induced as reported by some authors (mecdad et al., 2011; gangemi et al., 2016) . in this study, subjects exposed to a complex mixture of pesticides had a significantly positive correlation between the tnf-α (rs361525) polymorphism and the dna damage (r = 0.19; p = 0.01). all together, these findings indicate that the higher prevalence of a allele constitutes a susceptibility factor for the dna damage observed in the pesticide-exposed farmworkers. finally, genotype and allele frequencies of pon1, xrcc1, il6, il6r and mir-137 were similar to other studies (wong et al., 2008; singh et al., 2011; satti et al., 2013; mahmoudi and cairns, 2017) and did not present distinct distribution between exposed and unexposed groups. 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agricultural herbicides in iowa assessment of dna damage in floriculturists in southern brazil polymorphisms in metabolic gstp1 and dna-repair xrcc1 genes with an increased risk of dna damage in pesticide-exposed fruit growers genotoxic effects of a complex mixture of pesticides were observed in farmworkers • immune changes may reflect an immune activation in defense against pesticides • allele a of the tnf-α (rs361525) increased dna damage of the farmworkers this work received financial support from sus program (ppsus/go key: cord-333547-88dkh6xd authors: hasan, shadi w.; ibrahim, yazan; daou, marianne; kannout, hussein; jan, nila; lopes, alvaro; alsafar, habiba; yousef, ahmed f. title: detection and quantification of sars-cov-2 rna in wastewater and treated effluents: surveillance of covid-19 epidemic in the united arab emirates date: 2020-10-19 journal: sci total environ doi: 10.1016/j.scitotenv.2020.142929 sha: doc_id: 333547 cord_uid: 88dkh6xd testing sars-cov-2 viral loads in wastewater has recently emerged as a method of tracking the prevalence of the virus and an early-warning tool for predicting outbreaks in the future. this study reports sars-cov-2 viral load in wastewater influents and treated effluents of 11 wastewater treatment plants (wwtps), as well as untreated wastewater from 38 various locations, in the united arab emirates (uae) in may and june 2020. composite samples collected over twenty-four hours were thermally deactivated for safety, followed by viral concentration using ultrafiltration, rna extraction using commercially available kits, and viral quantification using rt-qpcr. furthermore, estimates of the prevalence of sars-cov-2 infection in different regions were simulated using monte carlo. results showed that the viral load in wastewater influents from these wwtps ranged from 7.50e+02 to over 3.40e+04 viral gene copies/l with some plants having no detectable viral rna by rt-qpcr. the virus was also detected in 85% of untreated wastewater samples taken from different locations across the country, with viral loads in positive samples ranging between 2.86e+02 and over 2.90e+04 gene copies/l. it was also observed that the precautionary measures implemented by the uae government correlated with a drop in the measured viral load in wastewater samples, which were in line with the reduction of covid-19 cases reported in the population. importantly, none of the 11 wwtps’ effluents tested positive during the entire sampling period, indicating that the treatment technologies used in the uae are efficient in degrading sars-cov-2, and confirming the safety of treated re-used water in the country. sars-cov-2 wastewater testing has the potential to aid in monitoring or predicting an outbreak location and can shed light on the extent viral spread at the community level. coronaviruses (covs), which range from 60 to 220 nm in size, are enveloped positive-sense single-stranded ribonucleic acid (rna) viruses with club-like spikes on their surface, and infect a wide range of hosts including birds and mammals. they were first identified in the mid-1960s, and have traditionally been associated with the common cold in humans. more recently, they gained significant medical importance due to the emergence of three deadly zoonotic strains: (i) severe acute respiratory syndrome coronavirus (sars-cov) in 2002 (mortality rate 11%), (ii) middle east respiratory syndrome coronavirus (mers-cov) in 2012 (mortality rate 35%), and (iii) sars-cov-2 in 2019 (mortality rate still being determined, but estimated at 2-3%) [1] [2] [3] [4] [5] . covs have more detrimental impacts on immunocompromised and elderly individuals and have the potential to create worldwide outbreaks [6] . the first cases of sars-cov-2 infections occurred in either late november or early december 2019, and quickly spread until the world health organization (who) declared it a public health emergency of international concern on january 30 th 2020, and a pandemic on march 11 th 2020. despite international efforts to contain the virus using various policies, it is still posing a serious global challenge today [7, 8] . scientists attribute the difficulty in managing the outbreak to a long incubation period (~5 days) and viral shedding and transmission by asymptomatic infected individuals [9, 10] . most of what we know about viral shedding comes from studies that quantify sars-cov-2 in pharyngeal or nasopharyngeal swabs, with very little work done to understand the shedding of this virus in stool. a limited number of studies have shown that the shedding period of sars-cov-2 in stool samples varies considerably, and can still be detected up to 27.9 ± 10.7 days after infection in some cases [9, 11] . the major transmission routes of sars-cov-2 have been shown to be through aerosol droplets, person to person contact, and contaminated surfaces j o u r n a l p r e -p r o o f journal pre-proof [11] [12] [13] [14] [15] . some studies demonstrated that the virus can replicate in cells that line the human digestive tract, and that a significant number of covid-19 patients have detectable levels of viral rna in their stool [16] [17] [18] . in some cases, the number of viral gene copies in one gram of stool ranges from ~10 4 to 10 8 genomes [16] [17] [18] . even though the virus is detectable in the stool of covid-19 patients, there is limited evidence that it is infectious, as only one study to date has demonstrated this to be the case, while another study demonstrated that it was not possible to isolate infectious viruses from the stool of covid-19 patients [16] [17] [18] . these findings indicate that sars-cov-2 could be detected in the municipal wastewater of a region containing infected individuals. furthermore, it also means that monitoring the virus in municipal wastewater represents an effective low-cost method to track infections in the population. wastewater monitoring has been a successful method of tracking emerging contaminants and circulating antimicrobial/antibiotic resistance genes [19] [20] [21] . furthermore, monitoring different types of viruses, such as hepatitis a, noroviruses, and rotavirus, in wastewater has also been used as a surveillance technique to investigate the distribution of these viruses in a community, a practice termed water-based epidemiology (wbe) [22, 23] . it is thus possible that wbe and the environmental surveillance of sars-cov-2 in wastewater could help track the outbreak in a certain region and identify regions with infected asymptomatic individuals. carrying out sars-cov-2 testing to identify and quarantine affected individuals is a good strategy for managing this outbreak in countries with testing capabilities and capacities, and is the method used here in the uae. however, it is a reactionary strategy that can only be deployed after a case is reported clinically, and by then it is likely that the virus has been spreading through a population at a significant level. in contrast, detecting and quantifying sars-cov-2 in wastewater covers a larger portion of the population as it essentially tests j o u r n a l p r e -p r o o f journal pre-proof everyone who contributed to the wastewater sample analyzed [24, 25] . if successful, it would be a way of mass testing and could lead to early detection before infections manifest as clinical cases or hospital admissions. recent peer-reviewed and non-peer-reviewed studies published by several groups in the netherlands, the usa, france, spain, italy, australia, and turkey have demonstrated that the idea of tracking infection rates by measuring the viral load in wastewater is feasible, cost-effective, and efficient [1, [26] [27] [28] [29] . the authors believe that the viral concentration in wastewater is a good predictor of the number of infected individuals in the population of the united arab emirates (uae), including asymptomatic cases that would otherwise remain undetected. most importantly, monitoring wastewater could be used as a way of tracking the prevalence of the virus and become an early-warning tool for new outbreaks in the future. consequently, the main objectives of this study were: (i) to detect the presence of sars-cov-2 virus in municipal (untreated) wastewater and treated effluents of wastewater treatment plants (wwtps) in the uae; (ii) to quantify the viral concentration in viral gene copies per liter; and (iii) to explore whether these measurements mirror infections in the population in order to comment on the utility of this method to track the epidemiology of the disease. thus far, the frequency and degree of testing individuals and wastewater samples achieved in the uae have been replicated only in a few other jurisdictions. to the best of our knowledge, this is the first study to detect and quantify sars-cov-2 in wastewater in the region. various sewer access points (e.g. manholes located in neighborhoods) and pumping stations. these 11 wwtps implement a series of treatment technologies including preliminary, primary, secondary (asp/clarification), and tertiary (sand filtration, disinfection, chlorination) for the purpose of reusing treated water (tse) for irrigating farmland and watering green spaces. composite samples were collected over a 24-hour period using auto-samplers, and 250 ml of the composite samples were transferred to isolab gmbh sterile polypropylene (pp) plastic bottles, labortechnik gmbh, germany) for 90 min [30] [31] [32] . although this inactivation step might lead to some viral loss, it is an essential safety measure that minimizes the risk of sars-cov-2 transmission to laboratory personnel. studies have demonstrated that thermal deactivation at lower temperatures, similar to the one chosen in this study, resulted in a non-infectious virus that could still be detected by rt-pcr based methods, while deactivation at much higher temperatures (92 o c) resulted in complete degradation of the virus so that detection was not possible by rt-pcr [32, 33] . after heat inactivation, the samples cooled down to 4 o c prior to filtration and viral concentration. in the second method, 8,000 average molecular weight polyethylene glycol (peg) was used to concentrate the viruses [30] . briefly, 50 ml of the filtrate was transferred to a 50 ml conical tube, followed by the addition of peg and nacl to a final concentration of 8 and 1.8%, respectively. the sample was mixed on a nutator for 1 h in order to dissolve the peg and nacl and precipitate viruses. the sample was then centrifuged at 12,000 x g using a fixed angle rotor for 2 h at 4 o c. the supernatant was poured off and the pellet was re-suspended in 1.5 ml of trizol (thermofisher cat#15596). isopropanol (1 ml) was added to the aqueous layer and the mixture was agitated by inverting the tube before incubation at room temperature for 10 min. the rna was pelleted by centrifugation at 12,000 x g for 15 min at 4 o c and washed once in 75% ethanol prior to resuspension in elution buffer (40 µl) from the abiopure viral dna/rna extraction kit. the two protocols described for viral concentration and rna extraction (either ultrafiltration columns/rna extraction kit or peg/trizol) were selected and tested because they were the two methods that were reported for this type of work at the time these experiments were initiated in early april 2020 [30, 34] . the authors wanted to compare them to decide which methodology to adopt as wastewater sampling continued. all the data reported in the tables were obtained using the ultrafiltration method ( fig. 1a) the extracted rna (8 µl the prevalence of sars-cov-2 infection in a certain region was estimated using the measured viral loads in wastewater, the wastewater flow rate, the viral load in the stool of infected individuals, and the estimated daily production of stool per capita according to eq. 2 [27] : the stool viral load (r f ) in log 10 was simulated as a log-normal distribution with a mean of 7.18 and stdev of 0.67 [16] . daily stool production per capita (f) (g/capita.day) was simulated as a log-normal distribution with a mean of 149 and stdev of 95 as per the statistics reported for the high-income countries [35] . the percentage of covid-19 patients who shed virus in their stool (ɛ) was modeled as a uniform distribution from 0.29 to 0.55, as reported by the limited number of studies on this topic thus far [11, 15, 36] . the reported data from the simulations were based on 50,000 calculations. j o u r n a l p r e -p r o o f at the time when the authors initiated this study, only two studies were reported in non-peerreviewed pre-prints; one study utilized ultra-concentration columns for viral concentration followed by rna kit extraction, while the other study used peg to concentrate viruses followed by trizol extraction [30, 37] . therefore, in order to assess the differences between these two methods and determine which one to use for our study, viruses from the same wastewater samples (50 ml) were concentrated using either peg followed by rna extraction with trizol or using a 30 kda mwco column followed by extraction using a viral rna kit as described in the materials and methods. quantification of the viral load was then performed identically on the rna extracted from each method using rt-qpcr. different methods for wastewater virus concentration have been adopted by different groups around the world [27, 30, 37] . the methods fall into three major categories and involve concentrating viruses using either (i) precipitation using chemicals such as peg or al(oh) 3, followed by centrifugation [1, 30, 38, 39] , (ii) ultrafiltration columns with very low molecular weight cut-offs [27, 29, 34] , or (iii) binding of viruses to electronegative membranes [27, 40] . using ultrafiltration columns in combination with the commercial rna kits resulted in higher counts compared to using peg and trizol (fig. 2) . indeed, a reading of 31.7 gene copies/ml was determined using the ultrafiltration method compared to a reading of 2.6 gene copies/ml for the same sample using the peg/trizol method. consequently, all subsequent virus measurements in the wastewater samples were performed using the ultrafiltration and commercial rna extraction kit method. the peg protocol tested here was used in the state of massachusetts in late march 2020, with a significantly higher number of reported cases than what was reported in the uae when j o u r n a l p r e -p r o o f journal pre-proof the measurements reported here were performed. in the massachusetts study, high counts ranging between 50 and 300 gene copies/ml were reported in the wastewater samples [30] . precipitation-based methods that rely on chemicals such as peg to concentrate viruses have a higher throughput since they are cheap and user-friendly compared to the expensive ultrafiltration column method that sometimes requires multiple rounds of centrifugation to concentrate the wastewater sample. however, using ultrafiltration columns in combination with commercial rna extraction kits might represent a more sensitive approach, more suited to detecting lower concentrations of the virus in wastewater. the ultrafiltration method might be more appropriate for long term surveillance as well after the virus concentration drops below the detectable limit of the assay. once that occurs, a more sensitive assay would be able to detect both methods used have advantages and caveats [41] . for example, one drawback of concentrating viruses using the ultrafiltration method is related to the fact that it is often difficult to concentrate all viruses from the sample, as some viruses are adsorbed to the solid phase in the wastewater sample and are thus pre-filtered when the sample is passed through the 0.2micrometer filter. as more groups report the experimental protocols they used to make sars-cov-2 wastewater measurements, scientists need to come together to agree on standardizing the method used to perform this analysis. whatever the method is chosen, there will always be a viral loss that results from different steps in the process. it is the author"s opinion that the most important property of wastewater monitoring is sensitivity, reproducibility, precision, and not j o u r n a l p r e -p r o o f necessarily accuracy. at this point, the value of these measurements is to observe the change over time in order to gain insight into infection rates and kinetics in the population. laboratories with access to bsl-3 labs will lead the way in determining which methods are best suited for this type of analysis in the future. the viral loads in the 11 wwtps and the 38 locations in the uae are summarized in fig. 3 and table 2 j o u r n a l p r e -p r o o f preceded by an elevation of sars-cov-2 concentration in wastewaters [43] . indeed, several studies have explored the detection and quantification of sars-cov-2 in wastewater influents [27, 30, 34, 39, [44] [45] [46] . however, only a few studies have attempted to establish a correlation between the increase/decrease in the viral load in the wastewater influents and the number of infected patients [1, 27, [43] [44] [45] . 2020, 346 new covid-19 cases were reported in the uae, which is less than those reported on the same day of the preceding month [42] . in another study carried out in the murcia region (spain), the epidemiological data on covid-19 revealed a tight correlation between the virus prevalence (cases per 1.00e+05 inhabitants) and the viral load in the wwtp"s influents. their study also confirmed that sars-cov-2 could be detected weeks before the initial confirmed case [1] . these studies, together with our findings, provide strong evidence for the significance of environmental epidemiological surveillance in monitoring sars-cov-2 outbreaks, and for this surveillance method to be used as an early warning tool for possible outbreaks or "second waves". this tool can help decision-makers in developing appropriate policies to manage outbreaks in a certain area. it can also help evaluate the effectiveness of these policies in reducing the widespread transmission of the virus. although mass testing of inhabitants for sars-cov-2 is an excellent option for assessing the virus prevalence, wastewater surveillance of sars-cov-2 viral loads can also be a good indicator of the circumstances on the ground and could direct the mass testing efforts to specific geographic locations. in epidemiology, the reproduction number is the number of individuals an infected person interacts with and infects. this number can be significantly reduced through infection mitigating policies that a jurisdiction implements [47, 48] . the first covid-19 case in the uae was reported on january 29 th 2020, and that person later recovered on february 9 th 2020. the j o u r n a l p r e -p r o o f several months after the virus outbreak, many countries still cannot carry out enough sars-cov-2 tests to identify and isolate infected individuals in order to curb the epidemic. what makes the situation even more complex is that a significant amount of viral transmission is attributed to asymptomatic infected individuals or individuals with very mild symptoms [51] [52] [53] . this also means that the number of actual infections is underestimated. thus, augmenting testing strategies using wastewater epidemiology data represents a promising new tool in estimating prevalence in a given location. different conclusions can be drawn from the wastewater analyses depending on how the data is processed, essentially achieving different levels of insight into the outbreak. at the first level, viral concentration in the wastewater (gene copies/l) is not very helpful on its own, though it can give you a good overview of how an outbreak is progressing from sampling the same area over time. this assumes that the flow of water through the area does not change much between sampling dates and viral load can inform on whether the outbreak is getting better or worse. importantly, different areas cannot be compared to each other using this first metric only. for instance, the viral load in viral gene copies/l for b4 wwtp gives an indication that the region served by this wwtp is significantly more affected than the region served by b2 wwtp, attempted to provide an estimate in different regions using the monte carlo approach and the results were reported with 95% ci based on the simulated variables. as more groups around the world report results and communicate laboratory protocols used to make these measurements, a comprehensive comparison needs to be carried out in order for scientists to agree on standardized methods. overall, this study showed the potential of detecting sars-cov-2 in wastewater as an early warning and prediction tool for the spread of the disease. this monitoring can help authorities take appropriate and prompt actions to contain any potential 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the epidemic in the netherlands the impact of a nation-wide lockdown on covid-19 transmissibility in italy estimating the effective reproduction number of the 2019-ncov in china straits times, uae imposes first lockdown on historic district to slow coronavirus coronavirus: uae to clear streets for disinfection drive who says asymptomatic covid-19 transmission is "very rare iceland lab"s testing suggests 50% of coronavirus cases have no symptoms no symptoms in 80% of covid cases raise concerns the authors are thankful to the ministry of interior (moi) in abu dhabi (uae) for their financial support (award no. cpra-2020-027), their immense efforts in coordination and key: cord-330779-mso2zfom authors: sunkari, emmanuel daanoba; korboe, harriet mateko; abu, mahamuda; kizildeniz, tefide title: sources and routes of sars-cov-2 transmission in water systems in africa: are there any sustainable remedies? date: 2020-09-09 journal: sci total environ doi: 10.1016/j.scitotenv.2020.142298 sha: doc_id: 330779 cord_uid: mso2zfom governments across the globe are currently besieged with the novel coronavirus (covid-19) pandemic caused by sars-cov-2. although some countries have been largely affected by this pandemic, others are only slightly affected. in this regard, every government is taking precautionary measures to mitigate the adverse effects of covid-19. sars-cov-2 has been detected in wastewater raising an alarm for africa due to the poor water, sanitation, and hygiene (wash) facilities. also, most countries in africa do not have resilient policies governing sanitation and water management systems, which expose them to higher risk levels for the transmission of sars-cov-2. therefore, this study unearthed the likely sources and routes of sars-cov-2 transmission in water systems (mainly wastewater) in africa through a holistic review of published works. this provided the opportunity to propose sustainable remedial measures, which can be extrapolated to most developing countries in the world. the principal sources and routes of potential transmission of sars-cov-2 in water systems are hospital sewage, waste from isolation and quarantine centres, faecal-oral transmission, contaminated surface and groundwater sources, and contaminated sewage. the envisioned overwhelming impact of these sources on the transmission of sars-cov-2 through water systems in africa suggests that governments need to put stringent and sustainable measures to curtail the scourge. hence, it is proposed that governments in africa must put measures like improved wash facilities and public awareness campaigns, suburbanization of wastewater treatment facilities, utilizing low-cost point-of-use water treatment systems, legally backed policy interventions, and community-led total sanitation (clts). sars-cov-2 in water systems can be inactivated and destroyed by integrating ozonation, chlorination, uv irradiation, and sodium hypochlorite in low-cost point-of-use treatment systems. these proposed sustainable remedial measures can help policymakers in africa to effectively monitor and manage the untoward impact of sars-cov-2 on water systems and consequently, on the health of the general public. countries, especially in africa. although some countries have been largely affected by this pandemic, others are only slightly affected. owing to this, every government is taking precautionary measures to mitigate the adverse effects of covid-19. some of the symptoms associated with covid-19 include fever, cough, diarrhoea, and breathing difficulties (who, 2020) . the world health organization (who) has mentioned that the main routes of exposure of the virus to humans are inhalation of droplets generated when an infected person coughs, sneezes, or exhales (who, 2020) . however, recent studies have shown that sars-cov-2 can be found in the faeces of infected symptomatic and asymptomatic patients (foladori et al., 2020; pan et al., 2020; randazzo et al., 2020; tang et al., 2020; xiao et al., 2020; zhang et al., 2020a) . clinical experiments and researches have also reported evidence of sars-cov-2 in urine samples of infected patients (lescure et al., 2020; ling et al., 2020) , and hospital and urban sewage (medema et al., 2020; wu et al., 2020) . it can be inferred from these studies that the water systems, especially municipal wastewater of areas hit hard by covid-19 might contain the virus. recently, sars-cov-2 has been detected in untreated wastewater in australia, the netherlands, usa, and france (ahmed et al., 2020; medema et al., 2020; nemudryi et al., 2020; wurtzer et al., 2020) corroborating the assumption that the virus could be detected in wastewater. this raises serious concerns for the water systems in developing economies like most african nations. most countries in africa do not have resilient policies governing sanitation and water management systems, which expose them to higher risk levels for the spread of policies regulating the siting of pit latrines in communities but these have been widely not adhered to in most countries. such acts expose people to cross-contamination of the pit latrines with the groundwater sources. consequently, if there are covid-19 infected patients living in such communities that have their pit latrines closer to their drinking water sources, the risk of getting infected with the virus through oral ingestion of the virus-contaminated water is very high. similar observations about water-borne diseases such as diarrhoea and gastroenteritis in africa are very common (oppong et al., 2020; samie et al., 2020) . indiscriminate open defection around surface and groundwater sources in africa have also been reported in the literature (elisante and muzuka, 2016; anornu et al., 2017; back et al., 2018; abanyie et al., 2020; houéménou et al., 2020; mutono et al., 2020; owamah, 2020) . through open defecation, the carriers of the virus may unknowingly transmit it through their stool to drinking water sources, which can have a debilitating effect on consumers of such virus-contaminated water. there is also a high risk of exposure to the virus by people that use the same toilets (a common practice in africa) because the virus may remain in the aerosol or droplet generated during the use of shared toilets built in small spaces without aeration. on 2 july 2020, senior government medical officers reported in ghana that the commonly known symptoms of cough, cold, fever, and breathlessness often exhibited by covid-19 patients are not lately shown by covid-19 patients. now, covid-19 patients show stomach upset, vomiting, and diarrhoea because the virus attacks the gastro-intestines rather than the previously known lungs attack. these are not well known symptoms of the virus and as such patients may not suspect these to be indicative of the fact they have come in contact with the virus. in addition, since these new symptoms of the virus are oblivious to most doctors, the virus could escalate at the community level. these symptoms are also akin to waterborne diseases and go to buttress the possibility of the virus being transmitted through the domestic usage of the virus contaminated water. also, untreated wastewater is mostly discharged into the environment, which may interact with surface and groundwater resources, thereby contaminating these dwindling resources (williams et al., 2019) . overall, since most of the people living in africa, especially those dwelling in rural and peri-urban settlements depend on surface and groundwater resources for their domestic water supply, the risk of contracting covid-19 through sars-cov-2 contaminated water is very high and thus, the sources and routes of community spread of the virus, which is currently being reported must be critically re-examined. therefore, this review examines the potential sources and routes of sars-cov-2 transmission in water systems in africa with emphasis on wastewater management systems and proposes sustainable remedial measures to deal with the potential risk of community spread of sars-cov-2 via wastewater in africa. hence, the review will be a framework for african policymakers in dealing with the covid-19 pandemic. it will also add to the pool of existing literature on the possible transmission of sars-cov-2 through wastewater. according to the who, as at 2017, about 2 billion people in the world are still living without basic sanitation facilities (who, 2019). out of this, about 709 million people representing 35% of the total number are living in africa. in contrast to the developed world, there is overreliance on non-sewered wastewater and sanitation systems in africa (street et al., 2020) . however, this goal is yet far from being achieved in africa. for example, in ghana, which is one of the biggest economies in west africa, only 21% of the population has improved sanitation systems in place (appiah-effah et al., 2019) , slightly below the improved basic sanitation coverage of 28% in sub-saharan africa (who, 2017) . elsewhere in south africa, which happens to be one of the biggest economies in africa, about 37% of the general public does not have a water-borne sewage system and thus, relies on bucket toilets, pit latrines, and chemical toilets as an alternative (street et al., 2020) . the same situation is common in most of the african countries. it is well documented in the literature that sub-saharan africa has most of its population sharing toilets vis-à-vis other nations in the world (rheinländer et al., 2015) . the situation is much worrying in the densely populated urban regions of sub-saharan africa, where public or shared toilets are common (morella et al., 2008) . gudda et al. (2018) studied pit latrine faecal sludge accumulation in nakuru, kenya and pointed out that all the pit latrines in 100 households were communal and the average number of shared users of a pit latrine was 23 persons. there have not been any reported cases of sars-cov-2 transmission via faecal-oral or waterborne routes and due to quarantine or self-isolation of persons suspected to be infected with covid-19, it is argued that infection through this route is unlikely (amirian, 2020). nevertheless, this might not hold for shared or communal spaces and the risk of faecal-oral transmission might be common in confined places of abode like hotels and places that are overcrowded . within the next decade (dos santos et al., 2017) . majority of the population growth is in informal and peri-urban areas, which usually do not have basic amenities like water and sanitation, as a result, urban access to water has been impeded overtime. current estimates reveal that approximately two-thirds of sub-saharan africa's urban residents live in informal settlements and only in nairobi, kenya, these areas contribute about 75% of urban growth (dos santos et al., 2017) . the access to water by residents of these informal areas is really appalling when compared to the core urban areas, thus, rapid population growth will only compound the situation (adams, 2018) . bain et al. (2018) revealed that during the period between 2000 and 2015, the annual rate of change of total population with access to basic drinking water amenities in sub-saharan africa was 57.6% and in north africa, it was 90.6%. moreover, the annual rate of change of total population with access to basic sanitation in sub-saharan africa was reported as 28.1% and 86.1% in north africa (bain et al., 2018) . in terms of hygiene, sub-saharan africa recorded a positive change of 15.4% whereas it was 76.3% in north africa (bain et al., 2018) . even with positive changes in hygiene, the records suggest that access to basic water, sanitation and hygiene amenities still remains very low in sub-saharan africa. in addition, nhamo et al. (2019) , studied the chances of africa to achieve the sdg 6 by 2030 using a composite index approach with three indicators of the sdg 6; proportion of the population using safely managed drinking water amenities, proportion of the population using safely managed sanitation amenities, and level of water stress. the results indicate that most of the countries are at various stages of achieving the targets set out in the sdg 6 ( table 1 ). the fact that many of the african countries show declining trends of wash is a clue that it will be difficult for africa to reach the sdg targets by 2030 (nhamo et al., 2019) . j o u r n a l p r e -p r o o f there are several routes through which sars-cov-2 can enter the water systems, which can eventually lead to its transmission through the water medium ( figure 2 ). some of these routes include wastewater discharged from hospitals, government-approved quarantine and isolation centres and houses used as quarantine and isolation centres. faecal contaminations can be transmitted through water supply network systems, which end up in contaminating the water (arslan et al., 2020; foladori et al., 2020) . in africa, domestic water supply is usually from surface and groundwater sources and these also serve as potential routes for transmission of sars-cov-2. for example, wastewater is often discharged directly into surface water sources without pre-treatment or proper treatment. if the wastewater discharged into the surface water sources contains fragments of sars-cov-2, which is the causative organism of covid-19, then it is possible that the water will be contaminated and there is a potential risk of community transmission since most rural dwellers in africa rely on surface water sources for their domestic water supply. in the same way, groundwater sources can also serve as conduits for transmitting sars-cov-2 if the discharged wastewater that contains fragments of the virus is introduced into the aquifer. the virus contamination can as well occur during groundwater recharge. generally, groundwater contains lesser microbial contaminants known as pathogens than surface water, but the biological integrity of groundwater cannot be underestimated (alley and alley, 2017). governments to partner with the private sector to deal with the situation. there is the need to provide efficient but cheap sanitation services to the citizenry, especially for the poorest of the poor. the best solution to this menace is the application of financial solutions to support the access of households to improved wash amenities and to encourage wash-related entrepreneurial activities. if governments provide easy access to funds by households and private individuals through microcredit, loans, and micro enterprise financing, this will facilitate the provision of wash amenities for the poor. another important measure for dealing with the possible transmission of sars-cov-2 through wash-related activities is public awareness through regular behavioural change campaign to revolutionize the thinking of most africans on myths associated with wash activities. if all these measures are put in place in africa, the likelihood for the transmission of sars-cov-2 and other human enteric viruses that may originate from the stool of infected persons will be very low. adequate and centralized wastewater treatment facilities are a major problem in africa. as explained before, in most african countries, huge amount of the untreated wastewater generated is usually released directly into surface water sources. the adverse effects of this attitude on public health is unquestionable. it is even worrying to know that the quarantine and isolation centres of health care facilities used for testing and treating suspected and confirmed covid-19 carriers have a common sewerage system with the coterminous communities and cities (adelodun et al., 2020) . this situation exposes the people to the tendency of using water from surface water sources that might be contaminated with sars-cov-2 and thus, making them vulnerable to the virus. one of the ways of contracting sanitary-related diseases is through leakage of sewerage systems when conveying wastewater j o u r n a l p r e -p r o o f journal pre-proof contaminated with pathogens and excretes (gormley et al., 2020) . the best antidote to this threat is separating the sewerage systems and wastewater treatment facilities of the health care centres from that of the urban central systems to facilitate viral removal during treatment process. wastewater treatment facilities should be located in at least each city. this will ameliorate the situation and stop people from indiscriminately discharging wastewater into surface water bodies. wastewater generated in most industries in africa, unfortunately do not pass through the entire cycle or pathway of wastewater flow (figure 3 ). mostly after generation, due to financial or infrastructural challenges, the wastewater does not get treated but is discharged with no benefit (figure 3 ). however, with the needed finances and infrastructure in place, the wastewater generated must be properly treated and discharged or reused. some of the ultimate uses of treated wastewater are for portable water supply, irrigation, and hydro energy ( figure 3 ). governments are overwhelmed with several equally important developmental works but there should be a willpower in dealing with the wastewater treatment issue in africa. to augment the situation, the private sector should be motivated to focus on investing in waste-to-value projects in parts of africa, where waste treatment or recycling facilities are absent. this will help improve the sanitary conditions around physical locations and also improve the health of the people. from water systems using cheaper low-cost point-of-use treatment devices such as zerovalent iron filter, iron-oxide bio-sand filter, nanocellulose-based filter, gravity-based ultrafilter, and many more (bradley et al., 2011; shi et al., 2012; chaidez et al., 2016; mautner, 2020) . these devices can be effectively used for inactivating and destroying the sars-cov-2 genetic material, especially in africa where there are no effective wastewater treatment systems. moreover, in view of the recent findings of researches that suggest that sars-cov-2 can be completely eliminated in water systems by the use of ozonation, chlorination, uv irradiation, and sodium hypochlorite (rosa et al., 2020; quevedo-león et al., 2020; wang et al., 2020b) , there is the need for african countries to start integrating them into their low-cost point-of-use treatment systems. the model for such an integration is schematically presented in figure 4 . in this schematic diagram, it can be observed that when the different disinfection techniques are integrated and control measures are put in place to prevent the water from being re-contaminated, the integrity and reliability of the reclaimed water can be enhanced. such an integrated approach of disinfecting contaminated water and wastewater can withstand influent flow and water quality fluxes. the current times require policy interventions that have legal support to direct the attitude of people living in africa. even with the advent of the covid-19 pandemic, some people living in africa believe covid-19 is a western disease and that the confirmed cases in their countries are only political gimmicks of their governments who they think largely depend on the western world. in these abnormal times, surface water sources such as streams and rivers, which hitherto were used as domestic water supply sources in some villages have to be j o u r n a l p r e -p r o o f protected from encroachment by the rural people. in this regard, governments have to find alternative ways of meeting the water supply needs of rural people. by doing so, sanctions can be meted out to violators. at this critical point in time, wastewater should be treated before discharge into the environment. hence, there must be stringent measures regulating wastewater treatment and culprits should be punishable by law. employees in wastewater treatment facilities must thus take maximum precaution to prevent themselves from possible infection. at least, it is encouraging that some african countries like ghana, nigeria, cameroon, south africa, angola, benin, burkina faso, equatorial guinea, ethiopia, gabon, guinea, kenya, liberia, rwanda, dr congo, sierra leone, zambia, and morocco, have already put law-supported punitive measures in place for people who do not wear masks in public places in the wake of the covid-19 pandemic. this sets the basis for others to follow suit if only they want to fight the covid-19 pandemic. however, the safety protocols provided by the who and ministries in charge of health in all countries should be strictly adhered to and people who violate them in public places should be sanctioned. this is an innovative way of allowing communities to initiate their own actions towards addressing their own problems. the aim is to help improve wash practices and it is currently being implemented in many developing countries through the guidance and support of non-governmental organizations. in africa, it is difficult for governments to be able to spearhead every developmental project. this calls for active participation of community members themselves and important stakeholders in society. one of the primary targets of the since previous approaches to curtail sanitation problems only set high standards with subsidies as incentives to rural people. overtime, this never became sustainable due to the uneven adoption and partial use of the toilet facilities. moreover, it has made rural dwellers over reliant on subsidies, which are not also regular. in this regard, faecal-oral transmission through open defecation persisted leading to the spread of waterborne diseases. so instead of merely providing the 'hardware' for wash practices, there is the need for behavioural change to ensure sustainable improvement and this can only be done through clts. investing in community mobilisation should be at the heart of the clts programs such that the focus on toilet construction for individual households will be shifted to making sure villages and communities are actually open defecation-free. through awareness creation with the message that the continuous practice of open defecation by even the minority in the community will expose everyone to the risk of diseases, clts will prompt the community's crave for collective change, will push people into taking actions and development of innovative ideas, will provide mutual support and proffer suitable local solutions to local problems, which in the end will lead to complete ownership and sustainability. the impact of the covid-19 pandemic is currently felt everywhere in the world and in all aspects of the economy. the impact is even envisioned to be more severe in the developing world like africa, which is still struggling to meet the basic necessities of life for the people living there. since most of the people living in africa, especially those dwelling in rural and peri-urban settlements depend on surface and groundwater resources for their domestic water supply, the risk of contracting covid-19 through sars-cov-2 contaminated water from wastewater systems is very high. hospital sewage, waste from isolation and quarantine centres, contaminated surface and groundwater sources, faecal-oral transmission, and j o u r n a l p r e -p r o o f assessment of the quality of water resources in the upper east region, ghana: a review thirsty slums in african cities: household water insecurity in urban informal settlements of lilongwe, malawi clinical and virological data of the first cases of covid-19 in europe: a case series persistence and clearance of viral rna nanocellulose water treatment membranes and filters: a review presence of sars coronavirus-2 in sewage and 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the kwahu-bombouaka group of the voltaian supergroup surgo foundation, 2020. africa covid-19 community vulnerability index (africa ccvi) detection of novel coronavirus by rt-pcr in stool specimen from asymptomatic child sarscov-2 rna detection of hospital isolation wards hygiene monitoring during the coronavirus disease 2019 outbreak in a chinese hospital disinfection technology of hospital wastes and wastewater: suggestions for disinfection strategy during coronavirus disease un-water global analysis and assessment of sanitation and drinking-water (glaas) 2014 report: investing in water and sanitation: increasing access, reducing inequalities who climate, sanitation and health modes of transmission of virus causing covid-19: implications for ipc precaution recommendations 1 billion people lack safe drinking water at home, more than twice as many emerging contaminants in a river receiving untreated wastewater from an indian urban centre prolonged presence of sars-cov-2 viral rna in faecal samples time course quantitative detection of sars-cov-2 in parisian wastewaters correlates evidence for gastrointestinal infection of sars-cov-2 hydrogeochemical controls and human health risk assessment of groundwater fluoride and boron in the semi-arid north east region of ghana isolation of 2019-ncov from a stool specimen of a laboratory confirmed case of the coronavirus disease 2019 (covid-19) the first author thanks the scientific and technological research council of turkey (tübi̇tak) for the continuous support as a doctoral fellow of bideb 2215 graduate scholarship program for international students. the editors, especially prof. damià barceló and the anonymous reviewers, are also sincerely acknowledged for their useful reviews that improved the quality of this paper. key: cord-341212-dk6ioi15 authors: ribeiro, andre luis ribeiro; sousa, naama waléria alves; carvalho, vitor oliveira title: besides the climate model, other variables driving the covid-19 spread in brazil() date: 2020-06-15 journal: sci total environ doi: 10.1016/j.scitotenv.2020.140211 sha: doc_id: 341212 cord_uid: dk6ioi15 nan we have read with great interest the study by auler et al. (auler et al., 2020) , about the influence of climate on covid-19 spread. the authors considered data from the five most affected cities by the current pandemic in brazil. the authors used meteorological data from 13 th of march to 17 th of april 2020 and analyzed weather conditions such as temperature, relative humidity and rainfall against variables like number of cumulative cases, new daily cases and contamination rate to build their study model. the study model and data analysis are well-performed, and although the authors found that temperature and relativity humidity influenced the covid-19 dissemination, other well-known and important variables, such as social distancing, population testing, hand wash (giordano et al., 2020) and rational use of face mask were not part of their study model (feng et al., 2020) . brazil is a continental country with large disparity between cities and regions, with massive differences from socioeconomic to human development. on the other hand, the governors of the state of rio de janeiro and são paulo, among others, are reinforcing social distancing in their state (wikipedia, 2020b) . this dispute was taken to the supreme court, which reinforced the authority of cities and states to define local measures of social distancing, quarantine, prohibition of activities and definition of essential services (federal, 2020) . the covid-19 pandemic started in wuhan, china and spread worldwide. the cities of são paulo and rio de janeiro were the 2 first cities to report cases in brazil, which is possibly explained by their importance in commercial aviation, responsible for almost 80% of the weekly international seats of the country, 62.27% and 17.1% respectively (based on data from november 2019 of the national civil aviation agency of brazil -anac) (regis, 2020) . since the cases started to spread in these cities, uncoordinated measures of social distancing were gradually implemented across the country, in despite of the divergences between the president and governors (wikipedia, 2020a) , (wikipedia, 2020b) . brasilia showed the first case in 7 th march and its history of the pandemic was marked by the trip of the brazilian president to usa between 7 to 10 of march, where evidence that high temperatures and intermediate relative humidity might favor the spread of covid-19 in tropical climate: a case study for the most affected brazilian cities medida cautelar na ação direta de inconstitucionalidade 6.341 distrito federal. supremo tribunal federal rational use of face masks in the covid-19 pandemic modelling the covid-19 epidemic and implementation of population-wide interventions in italy as bolsonaro flouts warnings, coronavirus spreads in brazil seis em cada dez voos internacionais no brasil decolam de sp key: cord-328914-6zog3xf3 authors: petroselli, chiara; montalbani, elena; la porta, gianandrea; crocchianti, stefano; moroni, beatrice; casagrande, chiara; ceci, elisa; selvaggi, roberta; sebastiani, bartolomeo; gandolfi, isabella; franzetti, andrea; federici, ermanno; cappelletti, david title: characterization of long-range transported bioaerosols in the central mediterranean date: 2020-10-19 journal: sci total environ doi: 10.1016/j.scitotenv.2020.143010 sha: doc_id: 328914 cord_uid: 6zog3xf3 airborne bacteria were characterized over a 2-y period via high-throughput massive sequencing of 16s rrna gene in aerosol samples collected at a background mountain european monitoring and evaluation programme (emep) network site (monte martano, italy) located in the central mediterranean area. the air mass origin of nineteen samples was identified by air mass modelling and a detailed chemical analysis was performed. four main origins (saharan, north-western, north-eastern, and regional) were identified, and distinct microbial communities were associated with these air masses. samples featured a great bacterial diversity with protobacteria being the most abundant phylum, and sphingomonas followed by acidovorax, acinetobacter and stenotrophomonas the most abundant genera of the dataset. bacterial genera including potential human and animal pathogens were more abundant in european and in regional samples compared to saharan samples; this stressed the relevance of anthropic impact on bacterial populations transported by air masses that cross densely populated areas. the principal aerosol chemical characteristics and the airborne bacterial communities were correlated by cluster analysis, similarity tests and non-metric multidimensional scaling analysis, explaining most of the variability observed. however, the strong correlation between bacterial community structure and air mass origin hampered the possibility to disentangle the effects of variations in bacterial populations and in dust provenance on variations in chemical variables. the presence and diffusion of bioaerosols (bacteria, viruses, fungi, and other dead or living organisms including biological debris) in the earth atmosphere impact ecosystems, climate, and human health (burrows et al., 2009; burrows et al., 2009; fröhlich-nowoisky et al., 2016; pöschl and shiraiwa, 2015) . the biosphere directly emits bioaerosols into the atmosphere, which subsequently enables their dispersion and transport even at long distances (després et al., 2012; womack et al., 2010) . in the course of atmospheric transport, bioaerosols may undergo further chemical and physical transformation, stress, and biological aging upon interaction with uv radiation, photo-oxidants, and various air pollutants like acids, nitrogen oxides, ozone, and aromatic compounds. all these processes can limit or even suppress the vitality of the living fraction of bioaerosol and therefore affect their capacity to diffuse and to colonize new ecosystems (womack et al., 2010) . due to the above challenges, the present knowledge on the ability of viruses and bacteria to spread in the air and diffuse infections and more in general diseases is still immature and demands a wide spectrum of investigation (middleton, 2017; morawska and cao, 2020; polymenakou, 2012) . most of the previous studies in the mediterranean area have been limited to advections of air masses from the sahara desert only. the occurrence and impact of this type of air mass, very rich in desert dust, are frequent and well documented (escudero et al., 2006; formenti et al., circulation of air masses of different origin and distinguished by nature, type, quality, and extent of contributions (cusack et al., 2012; kallos et al., 2014 kallos et al., , 2007 petroselli et al., 2018) . due to the very different characteristics of the source areas, these air masses are expected to carry different bacterial populations and specific chemical markers and pollutants. moreover only a few studies have used molecular-based approaches to investigate the relationships of different air masses with the bacterial communities in the mediterranean area. in such studies, bioaerosol characterization was conducted by a low-throughput approach (cloning and sequencing of 16s rrna gene), while high-throughput sequencing (hts) approaches were used in an even smaller number of cases. most of the previous studies on aerosol-associated microbial communities in the mediterranean area have been focused on intense saharan intrusions sampled in the proximity of the dust sources (gat et al., 2017; katra et al., 2015; mazar et al., 2016; polymenakou et al., 2008) , or after a long-range transport over the mediterranean basin (federici et al., 2018; rosselli et al., 2015; sanchez de la campa et al., 2013) . much less is known about the specific characteristic of the bacterial communities transported by air masses from continental europe. in this frame, the present study aims at defining the patterns of the bacterial communities of atmospheric aerosol from distinct geographic regions reaching the mediterranean. the samples were collected during different long-range transport events towards a background monitoring site hypotheses to be tested in this work are two-fold: (i) bacterial community structure associated with long-range transported aerosol in the central mediterranean area is significantly different based on the air mass provenance; (ii) there is a correlation between the main aerosol chemical characteristics and the airborne bacterial communities. to test these hypotheses, we investigated the chemical and microbial datasets by cluster analysis, similarity tests, and non-metric multidimensional scaling analysis. all the aerosol samples analyzed in this work were collected at the emep regional background site of monte martano (mm) in central italy (42°48'19''n, 12°33'55''e) . mm has been established in a relatively undisturbed location, near a television antenna, on the ridge of a small mountain chain (1100 m asl), above the timberline and facing a completely free horizon (moroni et al., 2015) . the site is equipped with aerosol, gaseous pollutants, and meteorological monitoring instrumentations (moroni et al., 2015) . due to its elevation, the low background concentrations and the 360° free horizon, the site is particularly suited for the assessment of long-range transport events of atmospheric aerosol (federici et al., 2018; petroselli et al., 2018a petroselli et al., , 2018b . the importance of the site for the monitoring of saharan dust advections was recognized the sampled filters underwent a thorough chemical characterization that included the investigation of both the inorganic and organic fractions of particulate matter. major ion composition was determined by ion chromatography (dionex 2100) after 30 minutes ultra-sonication in ultrapure water (18 mω). the quantified analytes were: li + , na + , shaken for 1h at maximum speed, centrifuged for 30' at 10000 x g and then at 11500 x g for 15' at 4c° to recover bacteria (radosevich et al., 2002) . supernatant was discarded and dna was j o u r n a l p r e -p r o o f each sequence was assigned to its original sample according to its index oligos and barcodes. after sorting the sequences, the reverse read of each paired-end sequence was reverse complemented and merged with the corresponding forward read. a quality cut-off was applied in order to remove the sequences that did not contain the barcode, those with an average base quality value (q) lower than 30 and those that did not provide a perfect match in j o u r n a l p r e -p r o o f journal pre-proof the overlapping part between the two paired ends. the barcode was removed and sequences were sorted into operational taxonomic units (otus) using the uparse-otu algorithm (edgar, 2013) . the minimum identity between each otu member sequence and the representative sequence (i.e. the sequence that showed the minimum distance to all other sequences in the otu) was set to 97%. the taxonomic classification of each otu was carried on with the stand-alone version of rdp bayesian classifier (wang et al., 2007) , using a 50% confidence level (claesson et al., 2010) . chloroplast sequences were not excluded by further analyses because their abundance can provide information on pm origin. three independent extractions, amplifications and sequencing on each sample were performed in order to test the robustness of the proposed experimental approach and the three replicates featured nearly identical otu distribution profiles (data not shown). cluster analysis using the bray-curtis similarity index was applied to the bacterial communities belonging to the different aerosol samples. similarity test (anosim) was performed to detect differences in the bacterial community structure followed by the determination of discriminating genera by means of simper routine. this analysis indicates the average contribution of each genus to the similarity and dissimilarity between groups of samples. non-metric multidimensional scaling (nmds) analysis was performed using the bray-curtis dissimilarity matrix and the first nmds dimension was then plotted with chemical data in order to gain information from the correlation between abiotic and biotic components of dust samples. additionally, the chemical peculiarities of the samples based on similarities highlighted by the nmds were interpreted by using principal component analysis (pca). statistical analyses and j o u r n a l p r e -p r o o f journal pre-proof graphical representations were carried out using the r statistical environment (version 4.0.1 -r core team 2020) and ggplot2 package (wickham, 2016) . nine saharan dust advections and ten long-range transports from other geographical origin have been considered in this work. the air mass origins were identified on the basis of back-trajectory (bt) analysis. the bts for the identified provenance groups are summarized in figure 1 , for the 500 m endpoint. the other endpoints (50 and 1000 m above the ground) provided similar results and have been included in supplementary material ( figure sm3 ). saharan dust advection samples have been marked with the code sh. as for the other provenances, three main macroareas have been identified, namely regional (rg), north-western (nw) and north-eastern (ne). rg air masses have been defined as those remaining over the terrestrial and marine sectors of central italy for at least 48 h before sampling. table 1 summarizes all the pm samples collected during 2014 and 2015. as a general trend, the saharan dust samples are characterized by higher aerosol mass concentrations with respect to the non-saharan advections (see table 2 ), i.e. an average +68.4% for pm 10 and +85.3% for pm coarse , defined as pm 10 -pm 2.5 , and lower pm 2.5 /pm 10 ratio, reading 0.52±0.18 for sh and 0.76±0.12 for non-sh samples. the increase in the concentration of the coarse fraction is typical of natural crustal aerosol sources such as desert dust (formenti et al., 2011) . moreover, ca and fe, typical crustal markers resulted higher in saharan dust on average ( table 2 ). the insoluble fraction of ca, defined as ca tot -ca 2+ , was close to 60% for saharan dust, j o u r n a l p r e -p r o o f journal pre-proof slightly lower for rg air masses and much lower for the nw. this is consistent with both the source area mineralogy and the different atmospheric processes during the long-range transport (avila et al., 2007) . biomass burning markers such as ammonium and organic carbon (oc) were higher in non-saharan samples, and particularly enriched in ne samples, possibly due to the frequent wildfires recorded in eastern europe regions. the latter have been found to exert a distinct impact on the monte martano site, as previously reported in . the average oc and ec values are in agreement with those reported in (sandrini et al., 2014) at mm for the year 2009. total pahs were on average the highest for rg followed by sh and ne and nw air masses. benzo(a)pyrene, the reference pah for health effects, has the same order in abundance. sequencing of 16s rrna gene fragments led to the recovery of 1286659 high-quality sequences, which clustered, across all samples, into a total of 10513 operational taxonomic units (otus) calculated at 97% of sequence similarity. the average number of otus per sample was 2239. although a considerable fraction of the total biodiversity (18.6% on average) could not be classified at genus level, a total of 879 different genera were identified across all samples. among them, a total number of 116 genera were found whose relative abundance was higher than 0.5% in at least one sample. these genera were considered abundant (abundant genera hereafter) and further analyzed. 32 bacterial genera manifested a relative abundance higher than 0.5% on average in all samples; they are shown in figure 2 . overall, the most abundant genera were sphingomonas (8.47%), followed by acidovorax (3.89%), acinetobacter (3.33%), methylobacterium is known to be resistant to desiccation and to γ radiation together with arthrobacter, also abundant in our samples (favet et al., 2013) . microvirga was already found in desert-coming air-masses and some species of this genus can reduce nitrogen gas to ammonia (favet et al., 2013; gonzález-toril et al., 2020) . it should be also noted that some of the 32 most abundant genera are human-and animal-associated bacteria and include known pathogens, such as haemophilus, staphylococcus, streptococcus and propionibacterium (brock et al., 2012) . moreover, we retrieved some bacterial genera that, despite being ubiquitous in the environment, also contain many opportunistic pathogens and a few pathogens, such as the pseudomonadales acinetobacter and pseudomonas, or clostridium sensu stricto and clostridium xi (brown, 2014) . however, analyses based on 16s rrna sequences do not allow to distinguish pathogenic from non-pathogenic species or strains. the results of the cluster analysis on the database containing only the abundant genera, summarized by the dendrogram in the right panel of figure 2 , were used for a data-driven visualization of the samples that are reported in the barplot following the dendrogram order. the average 1-d distances reported in the dendrogram revealed a high β-diversity among the j o u r n a l p r e -p r o o f journal pre-proof bacterial communities of the sh samples, which however generally clustered together. at genus level, the structure of bacterial communities clearly showed differences due to the sample provenance rather than to other factors such as seasonality. interestingly, amongst the pm samples, the non-saharan samples collected during regional movements of air masses (rg) and, to a lesser extent, during long-range intrusions (ne and nw), showed a high richness of genera with low abundance, indicating a highly diverse and even community. conversely, pm during saharan intrusions showed a lower richness of genera, indicating that these microbial communities were dominated by fewer typical phylotypes. this is in contrast with previous studies, which generally reported higher diversity during dust intrusion events compared to nondust events (gonzález-toril et al., 2020; griffin, 2007; mazar et al., 2016; polymenakou et al., 2008; sanchez de la campa et al., 2013) . it may be hypothesized that, in the case of central italy, both regional air masses and long-range intrusions from ne and nw mainly cross more heterogenous areas than saharan intrusions, thus collecting a wider variety of microorganisms. particularly, when bts indicated that regional air masses were prevalent, it is also possible that local sources played a major role in shaping bacterial communities. in fact, a wide variety of potential local sources, such as soil surface, leaf surface, water bodies and even animal faeces, to gain further insights about similarities and differences among all the aerosol samples and hypothesize possible effects of the air masses with different origins, a non-metric multidimensional scaling (nmds) analysis was performed using the computation of bray-curtis distances between bacterial communities. this statistical method has been applied to the database containing only the abundant genera, and results are shown in figure 3 . the results of j o u r n a l p r e -p r o o f nmds analysis showed a good clustering (stress value < 0.15) of the samples according to their provenance group. in particular, the nmds1 dimension (x-axis, figure 3 ) seems to separate well the different clusters, and particularly the saharan dust samples from the others, while nmds2 describes the variability within each group. nmds is a helpful exploratory analysis but does not allow explaining the similarities or dissimilarities among samples, and additional information from other analysis is needed. for example, samples associated with rg and nw air masses show a partial overlap in the nmds analysis, which is understandable based on the phenomenology of back trajectories (see figure 1 ). in fact, rg air masses at mm tend to the terrestrial and marine western sectors of peninsular although it has been demonstrated that a number of diseases are linked to desert aerosols (middleton, 2017) , the concern about saharan intrusions might be reduced from a public health point of view in this context, since air masses from european and regional origin were more enriched in human-associated bacteria than saharan air masses. a more detailed boxplot representation of the distribution of the 116 more abundant genera for the four air mass origins is reported in supplementary material (figure sm5 ). chemical and microbiological data were combined to check possible correlations between the variables and the sample provenances. in particular, some typical markers of saharan dust, biomass burning, and industrial activities, the two latter being particularly enriched in non-saharan samples, were identified amongst the chemical analytes. moreover, the analysis of the β diversity showed that the microbial communities of long-range transported saharan dust were significantly different from those sampled when other air masses were present, strongly supporting the hypothesis that desert dust can impact the bacterial composition of the aerosol at our latitudes (gat et al., 2017; mazar et al., 2016; rosselli et al., 2015) . on the contrary, non-saharan samples showed similar communities among each other, which in fact clustered together (figures 2 and 3) . nevertheless, as observed for the chemical characteristics, even if similarities existed within the pm samples sharing the same origin, the differences were not negligible and suggested that each event was independent of the others. this has been already observed in previous works, at least for dust events. in fact, significant differences in bacterial community j o u r n a l p r e -p r o o f journal pre-proof structure were reported during different dust events that impacted the same area, even when two events were very close in time (federici et al., 2018; yamaguchi et al., 2014) . in order to combine information about microbiology and chemistry, the nmds1 dimension from the statistical analysis on bacterial communities was correlated with the concentration of chemical variables, normalized against the pm values (w/w). some of the statistically significant correlations (p = ***) are shown in figure 5 . specifically, a significant correlation was found between nmds1 and pm 2.5 (i.e. pm 2.5 /pm 10 ratio). pm ratio was lower for saharan dust with the exception of the outlier sh_20141107 which corresponded to the weakest saharan dust event, with a pm 10 concentration of 8.4 µg/m 3 . the correlation was significant also between nmds1 and pm coarse ., which was higher for sh because saharan intrusions are constituted by coarser particles. organic carbon (oc) content correlated significantly with nmds1. oc in saharan dust was lower than in non-saharan samples because the latter can have a higher anthropogenic contribution. the highest oc/pm 10 values were found for sh_20140624 (which had also high sulphate concentration) and sh_20140522 of nw provenance. as stated above, also many bacterial genera that were significantly more abundant in non-sh than in sh samples (e.g. lactobacillus, streptococcus, propionibacterium and haemophilus) were generally related to anthropic and built environments. this confirms the relevance of the impact that densely populated areas may exert on bacterial populations transported by air masses. anthracene was the only pah correlating significantly with nmds1, being higher for sh samples. the sum of low molecular weight pahs (lw) was also higher for sh samples. calcium concentrations showed no correlation with nmds1, which was interpreted as due to the high local contributions of this element. iron, on the other side, was richer in sh samples and j o u r n a l p r e -p r o o f journal pre-proof correlated negatively with nmds1. ammonium and sulphate concentrations were generally higher for non-saharan air masses. innocente et al. (innocente et al., 2017) also reported that high ammonium and sulphate concentrations were associated with long-range transport from north-west in milan (north italy), and those air masses presented a high percentage of propionibacterium. this is in agreement with our simper analysis, which indicated the genus propionibacterium as significantly more abundant in nw than in sh samples ( figure 4 ). however, innocente and colleagues also reported that this correlation was weak, and ionic composition of air masses was much more clearly related to air mass provenience than to bacterial community structure. indeed, also in our case, since nmds1 was strongly correlated to air mass origin, it was not possible to fully understand whether variations in chemical variables were more correlated to variations in bacterial community structure or to dust provenance. in this work, we have characterized the bacterial communities of 19 air masses of different origin, sampled as pm 10 at the remote site of monte martano, in central italy. this emep station is representative of the central mediterranean area. the main results of the present work can be summarized as follows:  four distinctive air masses were identified: previous similar work on this topic was substantially limited to saharan (sh) dust air masses while in the present study we extended the characterization to regional (rg), north-western (nw), and north-eastern (ne) air masses.  at genus level, the distribution of the bacterial populations in air masses clearly showed differences due to the sample provenance. in fact, pm 10 during saharan intrusions j o u r n a l p r e -p r o o f journal pre-proof showed a relatively low number of genera, while non-saharan samples, particularly those collected during regional movements of air masses (rg), showed a high number of different genera with low abundance, indicating a highly diverse and even community. cluster analysis was performed on the 116 genera whose abundance was higher than 0.5% in at least one sample (abundant genera). barplots represent only the 32 bacterial genera that showed a relative abundance higher than 0.5%. chloroplasts were also included in the analysis. j o u r n a l p r e -p r o o f table 1 . sample characteristics in terms of provenance and aerosol mass concentration in the pm 10 and coarse (pm 10 -pm 2.5 ) fractions. provenance classification is based on bts analysis (see figure s1 in the supporting information). case studies of source apportionment and variation of soluble and insoluble calcium in red rains related to dust sources and transport patterns from north africa to northeastern spain continental-scale distributions of dust-associated bacteria and fungi desert dust contribution to pm10 loads in italy: methods and recommendations addressing the relevant european commission guidelines in support to the air quality directive microbial hitchhikers on intercontinental dust: catching a lift in chad airborne bacteria and 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produced particulate matter in the mediterranean and north atlantic: current state of knowledge natural and anthropogenic aerosols in the eastern mediterranean and middle east: possible impacts richness and diversity in dust stormborne biomes at the southeast mediterranean. sci. rep. 4, 5265 desert dust hazards: a global review airborne transmission of sars-cov-2: the world should face the reality ground-based measurements of long-range transported aerosol at the rural regional background site of monte martano (central italy) source identification of airborne bacteria in the mountainous area and the urban areas disentangling the major source areas for an intense aerosol advection in the central mediterranean on the basis of potential source contribution function modeling of chemical and size distribution measurements r: a language and environment for statistical computing. r foundation for statistical computing development of a high-volume aerosol collection system for the identification of air-borne microorganisms microbial immigration across the mediterranean via airborne dust back-trajectories show export of airborne fungal spores (ganoderma sp.) from forests to agricultural and urban areas in england chemical and microbiological characterization of atmospheric particulate matter during an intense african dust event in southern spain background levels of atmospheric hydrocarbons, sulphate and nitrate over the western mediterranean intercontinental dispersal of bacteria and archaea by transpacific winds noaa's hysplit atmospheric transport and dispersion modeling system naive bayesian classifier for rapid assignment of rrna sequences into the new bacterial taxonomy conservative fragments in bacterial 16s rrna genes and primer design for 16s ribosomal dna amplicons in metagenomic studies microbial aerosol characteristics in highly polluted and near-pristine environments featuring different climatic conditions biodiversity and biogeography of the atmosphere ggplot2: elegant graphics for data analysis changes in the rg rg nw cc: microbiological analysis:, dc: conceptualization, methodology, data curation key: cord-318856-f0m3wuyj authors: hoogeveen, martijn j.; van gorp, eric c.m.; hoogeveen, ellen k. title: can pollen explain the seasonality of flu-like illnesses in the netherlands? date: 2020-10-22 journal: sci total environ doi: 10.1016/j.scitotenv.2020.143182 sha: doc_id: 318856 cord_uid: f0m3wuyj current models for flu-like epidemics insufficiently explain multi-cycle seasonality. meteorological factors alone, including the associated behavior, do not predict seasonality, given substantial climate differences between countries that are subject to flu-like epidemics or covid-19. pollen is documented to be allergenic, it plays a role in immuno-activation and defense against respiratory viruses, and seems to create a bio-aerosol that lowers the reproduction number of flu-like viruses. therefore, we hypothesize that pollen may explain the seasonality of flu-like epidemics, including covid-19, in combination with meteorological variables. we have tested the pollen-flu seasonality theory for 2016-2020 flu-like seasons, including covid-19, in the netherlands, with its 17.4 million inhabitants. we combined changes in flu-like incidence per 100k/dutch residents (code: ili) with pollen concentrations and meteorological data. finally, a predictive model was tested using pollen and meteorological threshold values, inversely correlated to flu-like incidence. we found a highly significant inverse correlation of r(224)= -0.41 (p < 0.001) between pollen and changes in flu-like incidence, corrected for the incubation period. the correlation was stronger after taking into account the incubation time. we found that our predictive model has the highest inverse correlation with changes in flu-like incidence of r(222) = -0.48 (p < 0.001) when average thresholds of 610 total pollen grains/m3, 120 allergenic pollen grains/m3, and a solar radiation of 510 j/cm2 are passed. the passing of at least the pollen thresholds, preludes the beginning and end of flu-like seasons. solar radiation is a co-inhibitor of flu-like incidence, while temperature makes no difference. however, higher relative humidity increases with flu-like incidence. we conclude that pollen is a predictor of the inverse seasonality of flu-like epidemics, including covid-19, and that solar radiation is a co-inhibitor, in the netherlands. makes pollen less airborne, and cools the bio-aerosol down. very high humidity levels (rh 98%) are even detrimental to pollen (guarnieri, 2006) . an rh 98% effect on pollen could thus provide an alternative explanation as to why flu-like incidence in tropical countries is higher during the rainy season, and reduced during the rest of the year. we hypothesize that pollen bio-aerosol has an inverse effect on flu-like incidence, including covid-19 (see figure 1 ), whereby pollen is known to be triggered and influenced by meteorological variables, which can then jointly explain the seasonality of flu-like incidence. this indirect explanation of the pollen effect is based on the fact that pollen bio-aerosol and uv light exposure lead to immuno-activation, and sometimes allergic symptoms, which seem to protect against flu-like viruses, or at least severe outcomes from them. the indirect pollen effect is explained by the spread of pollen bio-aerosol under sunny and dry conditions. further, it is unknown how viral bio-aerosol and pollen bio-aerosol interact with each other in the air, and whether anti-viral phytochemicals in pollen could then play a role in an alternative explanation. to further understand the impact of pollen as an environmental factor influencing the life cycle of flulike epidemics, the objective of this study is to determine the correlations of pollen and meteorological variables with (changes in) flu-like incidence and develop and test a discrete predictive model that combines pollen and meteorological co-inhibitors. our main hypothesis, therefore, is that pollen is the missing link, jointly explaining with certain meteorological variables, flu-like seasonality, and that a compound threshold based factorcombining detected flu-inhibitorsis a good unified predictor of such seasonality. regarding covid-19, we have limited ourselves to observing whether or not covid-19 at the tail-end of the 2019/2020 flu-like season is able to break with the flu-like seasonality pattern. to study the relationship between pollen and flu-like incidence in the netherlands, we used the public datasets of elkerliek hospital (elkerliek.nl) about the weekly allergenic, low-level allergenic and total pollen concentrations in the netherlands in grains/m 3 , whereby for 42 types of pollen particles the j o u r n a l p r e -p r o o f journal pre-proof numbers are counted and averaged per day per 1m 3 of air. the common burkard spore trap was used, through which a controlled amount of air was ingested. the applied classification and analysis method conforms to the eaaci (european academy of allergology and clinical immunology) and the ean (european allergy network) standards. allergenic pollen includes nine types of particles that are classified as moderate (corylus, alnus, rumex, plantago and cedrus libani) , strong (betula and artemisia), or very strong allergenic (poaceae and ambrosia). additionally, we included low-level allergenic pollen concentrations in addition to the allergenic ones because we assume that they may also have effects. low-level allergenic pollen includes the other 33 particles that are classified as nonallergenic to low-level allergenic (cupressaceae, ulmus, populus, fraxinus, salix, carpinus, hippophae, fagus, quercus, aesculus, juglans, acer, platanus, pinus, ilex, sambucus, tilia, ligustrum, juncaceae, cyperaceae, ericaceae, rosaceae, asteraceae, ranunculaceae, apiaceae, brassicaceae, urtica, chenopodiaceae, fabaceae, humulus, filipendula, and indet) . total pollen concentration is the sum of the average allergenic and low-level allergenic pollen concentrations. advantages of using the total pollen metric are that there are hardly any 0 values (only 3 out of 266), and we did not need to limit ourselves to just parts of the seasonal cycle, which might introduce subseasonal bias into our research. we also assumed that long-distance pollen transport is accounted for, as foreign pollen will also be counted by a pollen measuring station that works all year round. furthermore, we used the data from the dutch state institute for public health (rivm.nl) gathered by nivel (nivel. nl) about weekly flu-like incidence (who code "ili" -influenza like illnesses) reports at primary medical care level, per 100,000 citizens in the netherlands. primary medical care is the using the number of influenza-like reports per primary care unit divided by the number of patients registered at that unit. this is then averaged for all primary care units and then extrapolated to the complete population. the datasets run from week 1 of 2016 up to week 18 of 2020 (n = 226 data points) to include the recent covid-19 pandemic at the tail-end of the 2019/2020 flu-like season. to underpin the relative importance of covid-19: sars-cov-2 has been detected in the netherlands since week 9, 2020. according to the figures of nivel.nl (2020, see figure 2 ), from week 13 onward sars-cov-2 is the outcome of the (vast) majority of positive tests for patients at primary care level with flu-like complaints, and by week 18 100% of positive tests indicate sars-cov-2 (other tested viruses are five influenza a and b subtypes, rsv, rhinovirus and enterovirus). furthermore, we also included meteorological datasets from the royal dutch meteorological institute (knmi.nl), including average relative humidity/day, average temperature/day and global solar radiation in j/cm 2 per day as an indicator of uv radiation. these datasets were obtained from the knmi's centrally located de bilt weather station. next, we calculated the weekly averages for the same periods that featured in the other datasets. de bilt is traditionally chosen as it provides an approximation of modal meteorological parameters in the netherlands, which is a small country. furthermore, all major population centers in the netherlands, which account for around 70% of the total dutch population, are within a radius of only 60 kilometers from de bilt. we therefore assumed in this study that the measurements from de bilt are sufficiently representative for the meteorological conditions typically experienced by the dutch population. to test allergenic versus low-level allergenic pollen assumptions, against hay fever and pre-covid-prevalence of allergic rhinitis that is more or less similar to that in western europe, being around 23%, and frequently undiagnosed (bauchau & durham, 2004) . furthermore, it can be noted that the prevalence of allergic diseases in general in the netherlands is around 52% (van de ven et al, 2006) . datasets were complete, except that three weekly pollen concentration measurements were missing (1.3%). this was due to a malfunctioning monitoring station during week 26 of 2016, week 21 of 2017 and week 22 of 2019. these missing measurements appeared to be completely random. we imputed missing values to avoid bias and maintain power. we used a four-week surrounding average to estimate the three missing data points and thus avoid breaking lines in visuals. we checked that the missing data has no material impact on the results by comparing these averages with the data of previous years for similar periods, and by observing whether removal from statistical tests had any effect on outcomes and conclusions. regarding the incidence of flu-like symptoms, we calculated the weekly change compared to the previous week (δili=ili t -ili t-1 ). this was to obtain an indication of the flu-like epidemic life cycle progression, whereby a decline is interpreted as ro<1 and an increase as ro>1 (ro is the reproduction number of flu-like viruses). furthermore, to cater, in one time-series metric, for changes in flu-like incidence as well as for an incubation period of up to two weeks, we calculated a three-week moving average (3wma) of changes in flu-like incidence, of which two weeks are forward looking: (δili 3wma = (δili t + δili t+1 + δili t+2 )/3) thus, δili 3wma has on average a one week lag. a general advantage of a moving average is that it reduces statistical noise. it should be noted that whenever we use the term incubation time, we also mean to include reporting delay (estimated to be around 4.5 days). we have not assumed delay effects for meteorological variables or pollen concentrations, so we have not calculated moving averages for other time series. compared with our previous study (hoogeveen, 2020) , there is an overlap in datasets of less than 10%. the datasets are extended by the extension in time, the addition of meteorological datasets and non-allergenic pollen, and the introduction of newly calculated variables, such as total pollen j o u r n a l p r e -p r o o f journal pre-proof concentration, δili 3wma , the compound predictor and the log10 transformations on pollen, ili and the hay fever index. we formulated the following statistical null hypotheses for falsification. h1 0 : there are no inverse correlations for total pollen concentrations with flu-like incidence (corrected for incubation period). h2 0 : there are no inverse correlations between pollen and changes in flu-like incidence (δili or corrected for incubation time: δili 3wma ). h3 0 : there is no predictive significance of a discrete model's compound value, based on thresholds for pollen and meteorological co-inhibitors, related to changes in flu-like incidence (δili 3wma ). to understand the role of meteorological variables, to check whetherin our datasetsmeteorological variables show their well-established effects on pollen as assumed, and to select coinhibitors: h4 0 : meteorological variablessolar radiation, temperature and relative humidityhave no effect on pollen and/or flu-like incidence change (δili 3wma ). low-level allergenic pollen is sometimes known to have a slight allergenic effect. to understand how to interpret adding none-to-low-level allergenic pollen to the total pollen metric, we wanted to verify their effects on the hay fever index: h5 0 : low-level allergenic pollen has no effect on hay fever and (changes in) flu-like incidence. note that with the exception of h5, all hypotheses are related to potential causality: the temporal sequentiality (temporality) of the respective independent variables, and flu-like incidence corrected for incubation period. whenever we refer to temporality, we mean to indicate that the datasets behave as if there is causality, on the understanding that statistics alone cannot prove causality in uncontrolled settings. variables are presented with their means (m) and standard deviations (sd). we calculated correlation coefficients to test the hypotheses and to assess the strength and direction of relationships. as a sensitivity analysis, we also calculated the bootstrapped correlation coefficients. we used the full datasets, to avoid sub-seasonal bias, and by extending the number of years the distortions by incidental and uncontrolled events are supposed to be minimized. however, as a second sensitivity analysis, we removed from the datasets the autumn weeks between 42 and 50, which typically show low pollen concentrations of up to 20 grains/m 3 , which are applied to analyze the main outcome (h2 0 ). further, as a third sensitivity analysis we calculate correlations per individual time lag included in δili 3wma in relation to h2 0 . next, linear regression (f-test) on identified inhibitors and interactions was used descriptively to determine whether the relationship can (statistically) be described as linear, and to determine the equation using estimates and intercept values, and produce probability, significance level, f-value, and the multiple r squared correlation to understand the predictive power of the respective inhibitor. standard deviations and errors, and degrees of freedom (df) were used as input for calculating the 95% probability interval. we have reported in the text the outcome of statistical tests in apa style, adapted to journal requirements. for relationships that appear non-linearlogarithmic or exponential we have used the log10 function to transform the data if that makes the relationship appear linear, before re-applying linear regression. we have also used the log10 transformed datasets for the calculation of correlation coefficients, to correct for skewness. finally, we created a simple, discrete model resulting in one compound value, using selected flu-like inhibitors. this was to determine the optimal average threshold values for these inhibitors, which have between total pollen and flu-like incidence, including the first cycle of the covid-19 pandemic. furthermore, we can reject h5 0 in favor of our assumption that it makes sense to also include low-level allergenic pollen concentrations in our study. low-level allergenic pollen is inversely correlated to flulike incidence (r(221) = -0.37, p < .00001), especially when corrected for the 2 weeks incubation time (r(219) = -0.53, p < .00001). the fact that the correlations become stronger when taking into account incubation time, implies temporality. furthermore, we can also observe from figure 3 that flu-like incidence starts to decline after the first pollen bursts. moreover, flu-like incidence starts to increase sharply after pollen concentrations become very low or close to zero. this is a qualitative indication of temporality. furthermore, we can notice that the first covid-19 cycle behaved according to pollen-flu seasonality, at least does not break with it. when testing the impact on δili, the weekly changes in medical flu-like incidence, the extended dataset till 2020, including covid-19, shows a strong and highly significant inverse correlation with total pollen (r(226) = -0.26, p = 0.000063). therefore, we can falsify the null-hypothesis (h2 0 ) that there is no inverse correlation between the weekly pollen concentrations and weekly changes in flulike incidence (δili), including the period covering the first cycle of the covid-19 pandemic. this inverse correlation therefore provides further support for the alternative hypothesis that the presence of an elevated level of pollen has an inhibiting effect on flu-like incidence, and starts to immediately influence the direction and course of the epidemic life cycle. also, during the covid-19 dominated period of the last 9 weeks, it appears that flu-like incidence behaves according to the expected pollenflu seasonality. this strengthens the idea that covid-19 might itself be seasonal, like all other flu-like pandemics since the end of the 19 th century. also when studying other data from rivm.nl about covid-19 hospitalizations, we cannot conclude that covid-19 breaks through the seasonal barrier. for example, new covid-19 hospitalizations decreased from a peak of 611 on march 27 to just 33 on may 3, the last day of week 18. using the three-week moving average (δili 3wma ) of changes in flu-like incidence, the correlation coefficients become stronger and are again highly significant for total pollen concentration (r(223) = -j o u r n a l p r e -p r o o f journal pre-proof 0.41, p < 0.00001). the bootstrapped correlation coefficient calculation gives a comparable outcome (r(223) = -0.38, p < 0.0001). as a second sensitivity analysis, we used the reduced dataset (minus the weeks of low pollen activity) and again found similar correlations (r(191) = -0.44, p < 0.0001; bootstrapped r(188) = -0.44, p < 0.0001, ci 95% -0.46 to -0.25)). finally, as a third sensitivity analysis, we analyze each time lag included in the δili 3wma calculation separately. per individual time lag there are as well highly significant inverse correlations: as given before r(226) = -0.26, p = 0.000063 in case of no time lag (δili t ); r(225) = -0.22, p = 0.000713 in case of a time lag of one week (δili t+1 ); r(225) = -0.23, p = 0.000552 in case of a time lag of two weeks (δili t+2 ); and the bootstrapped correlations for these are similar. we can thus also reject the null-hypothesis (h2 0 ) that there is no inverse relationship between pollen and changes in flu-like incidence including incubation time (δili 3wma or δili t+1 or δili t+2 ). these correlations (see also figure 4 ) are a further indication of temporality and does not contradict the idea that covid-19 is subject to pollen induced fluseasonality. the fact that the correlation with δili 3wma is stronger than those for each of the included time lags might be an indication of the noise reduction effect of this moving average, and makes thus the compound effect of the three covered time lags more visible. linear regression analysis shows that pollen has a highly significant inhibitory effect on flu-like incidence change (δili 3wma ) of f(1, 222) = 37.1, p < 0.001 (see table 2 , line 1), as a further basis for using total pollen concentration as a predictor. a log10 transformation of pollen to compensate for visual non-linearity leads to a similar outcome: f(1, 219) = 43.87, p < 0.001 (see table 2 , line 4). at least visually, it is a good fit (see figure 4 ). of the meteorological variables, only solar radiation has a highly significant inverse correlation with changes in flu-like incidence (δili 3wma ): (r(224) = -0.25, p = 0.000156). thus, of the meteorological variables, when it comes to solar radiation and relative humidity the nullhypothesis (h4 0 ) can also be rejected, as they seem to effect the flu-like epidemic lifecycle. of these two, only solar radiation is a flu-like inhibitor in line with its positive effect on pollen concentration, its association with immune-activation and the effect that uv has on viruses. a univariate linear regression also shows the highly significant negative correlation for solar radiation on flu-like incidence change (δili 3wma ) (f(1, 222) = 14.43, p < 0.001 (see table 2 , line 2). as the correlation is weak (multiple r-squared = 0.06), we have interpreted solar radiation as a co-inhibitor in relation to pollen; as a stand-alone independent variable its effect is too weak to explain flu-like seasonality. taking into account all these findings, we developed a discrete, compound model in which we included the changes in flu-like incidence (δili 3wma ), a threshold value for solar radiation (k r ), and both pollen threshold values for allergenic (k ap ) and total pollen (k p ). we found that the compound model has the highest inverse correlation (r(222) = -0.48, p < 0.001) for the following threshold values: k r : 510 j/cm 2 , k ap : 120 allergenic pollen grains/m 3 , and k p : 610 total pollen grains/m 3 . the bootstrapped correlation coefficient calculation gives a comparable outcome (r(222) = -0.47, p < 0.0001). in line with the previous outcomes, the inclusion of relative humidity, low-level allergenic pollen or temperature did not improve the correlation strength of this model. furthermore, given that they showed no significant interaction effects with pollen, it was not necessary to take such interactions into consideration in the model. in each of the observed years, the now (re)defined pollen thresholds are passed in week 10 (± 5 weeks), depending on meteorological conditions controlling the pollen calendar and coinciding with reaching flu-like peaks, and again in week 33 (± 2 weeks), marking the start of the new flu-like season. there is a highly significant inverse relationship between our compound threshold-based predictor value with flu-like incidence change (δili 3wma ) of f(1, 222) = 65.59, p < 0.001 and a multiple r-j o u r n a l p r e -p r o o f squared correlation of 0.2281 (see table 2 , line 3). this confirms the usefulness of a discrete, pollen and solar radiation threshold-based model as a predictor of switches in flu-like seasonality, whereby the effect of pollen is stronger than that of solar radiation. as a consequence, we can reject the nullhypothesis (h3 0 ) that this compound pollen/solar radiation value has no predictive significance for flulike seasonality. first of all we will discuss the possible implications of the results for our theoretic model and alternative explanations. next, we will discuss our methods. we found highly significant inverse relationships between pollen and solar radiation and (changes in) flu-like incidence: a higher pollen concentration or an increase in solar radiation in the netherlands is related to a decline in flu-like incidence. this inverse correlation with pollen becomes stronger when the 2019/2020 period is included, which has been increasingly dominated by covid-19 during the last 9 weeks. given that more time will be needed to draw conclusions about whether the spread of covid-19 is seasonal or not, from the data in this study it can only be observed that covid-19 is not breaking with the flu-like seasonality pattern. alternatively, social distancing may have contributed to flattening both the flu-like epidemic and covid-19 pandemic curves at the tail-end of the 2019/2020 flu-like season. the dutch government imposed hygiene measures from march 9, 2020 onward and a mild form of a lockdown, that included social distancing, from march 11. such behavioral policies the highly significant inverse correlation between hay fever and flu-like incidence confirms that allergic rhinitis makes it more difficult for flu-like viruses to propagate. solar radiation, the only meteorological variable that has a co-inhibitive effect on changes in flu-like incidence, has a stimulating effect on aerosol pollen formation and is responsible for melatonininduced immuno-activation. relative humidity reduces pollen aerosol formation, and correlates positively with flu-like incidence. we did not specifically look at precipitation, but it might make sense to explicitly consider this independent variable, given that it reduces pollen dissemination. in our study we showed that temperature, aside from the fact that it influences pollen, has no predictive value for changes in flu-like incidence. therefore, its inverse correlation with flu-like incidence might be interpreted in a number of ways: a) as spurious: the common causal factor is solar radiation, or b) as a stressor that has immediate effects on the functioning of the immune system of already infected persons. when discussing the influence of meteorological variables, we assume that the associated behavioral aspects are covered. these are sometimes summarized as seasonal behavior, but this independent variable might have a cultural dimension that needs to be better understood. we showed that a compound value, based on threshold values for pollen and solar radiation, results in a stronger correlation with the flu-like lifecycle than the individual inhibitors. this model could form an empirical basis for understanding flu-like seasonality, its ro and reliably predicting the start and end of each flu-like cycle. given that behavior, in the form of hygiene and social distancing, is also widely seen as an inhibitor, it might be worthwhile to also include this factor in our compound value. this will probably lead to an even stronger predictor for the evolution of the reproduction number ro of flu-like epidemics, although this might be beyond explaining the seasonality effect itself. for as long as the level of herd immunity (fine et al., 2011) for covid-19 is still below required thresholds for ending pandemics (plans-rubio, 2012) , it might make sense to also include indications of herd immunity levels in the theoretic model. finally, despite air pollution not been seen as an inhibitor of flu-like incidence (coccia, 2020), it still might interact with pollen. a more complete theoretic model, controlling for the (interactions with) air pollution, could give more insight in how to interpret the findings of this or similar studies. in general, statistical research cannot prove causal relationships in uncontrolled environments, even if datasets seem to behave as if there is causality. such statistics, however, can provide indications and identify reliable predictors, help filter out bad ideas, and be the inspiration for testable hypotheses that can be verified in laboratory and other fully controlled experiments. with a predictor we mean that a reliable temporal relationship between two variables is identified, without yet having validated causality, i.e., a bellwether factor. although the datasets seem to be sufficiently representative, there appears to be room for improvement. for example, including the data of more weather stations might help to improve the approximation of the weather conditions the dutch population experiences on average, and help to distinguish patterns per province. furthermore, it might be useful to include wind speeds, given that these constitute a vector for the dispersal of pollen in the netherlands, which has a maritime and temperate climate. additionally, the effects of climate change on pollen maturation (frei & gassner, 2008 ) might also be an important factor. another example of improving the representativeness would be by including more pollen types in the particle counts than are currently covered by the current methodology of the european allergy network. further, reclassification or recalibration of pollen types on a rational scale in terms of allergenicity, let's say 0-100%, would be very useful. for example, if pollen types are identified with a reliable score of 0%, these could be used to differentiate impact of pollen eleven faces of coronavirus disease 2019 herd immunity": a rough guide seasonality in risk of pandemic influenza emergence towards a data-driven characterization of behavioral changes induced by the seasonal flu ripe pollen carbohydrate changes in trachycarpus fortunei: the effect of relative humidity climate change and its impact on birch pollen quantities and the start of the pollen season an example from switzerland for the period 1969-2006 pollen exposure weakens innate defense against respiratory viruses nivel zorgregistraties eerste lijn -surveillance -wekelijks bulletin over symptomen en aandoeningen op basis van gegevens van huisartsen why lungs keep time: circadian rhythms and lung immunity the vaccination coverage required to establish herd immunity against influenza viruses dynamical prediction of flu seasonality driven by ambient temperature: influenza vs. common cold current understanding of the pathophysiology of allergic rhinitis covid-19 transmission in mainland china is associated with temperature and humidity: a time-series analysis humidity and latitude analysis to predict potential spread and seasonality for covid absolute humidity and pandemic versus epidemic influenza the role of temperature and humidity on seasonal influenza in tropical areas: guatemala, el salvador and panama global influenza seasonality: reconciling patterns across temperate and tropical regions potential utility of melatonin in deadly infectious diseases related to the overreaction of innate immune response and destructive inflammation: focus on covid-19 & asfiang p. correlation between weather and covid-19 pandemic in jakarta atopic diseases and related risk factors among dutch adolescents receptor recognition by the novel coronavirus from wuhan: an analysis based on decade-long structural studies of sars coronavirus association between ambient temperature and covid-19 infection in 122 cities from china no association of covid-19 transmission with temperature or uv radiation in chinese cities clinical characteristics of 140 patients infected with sars-cov-2 in wuhan key: cord-321727-xyowl659 authors: wang, lishi; li, jing; guo, sumin; xie, ning; yao, lan; cao, yanhong; day, sara w.; howard, scott c.; graff, j. carolyn; gu, tianshu; ji, jiafu; gu, weikuan; sun, dianjun title: real-time estimation and prediction of mortality caused by covid-19 with patient information based algorithm date: 2020-07-20 journal: sci total environ doi: 10.1016/j.scitotenv.2020.138394 sha: doc_id: 321727 cord_uid: xyowl659 the global covid-19 outbreak is worrisome both for its high rate of spread, and the high case fatality rate reported by early studies and now in italy. we report a new methodology, the patient information based algorithm (piba), for estimating the death rate of a disease in real-time using publicly available data collected during an outbreak. piba estimated the death rate based on data of the patients in wuhan and then in other cities throughout china. the estimated days from hospital admission to death was 13 (standard deviation (sd), 6 days). the death rates based on piba were used to predict the daily numbers of deaths since the week of february 25, 2020, in china overall, hubei province, wuhan city, and the rest of the country except hubei province. the death rate of covid-19 ranges from 0.75% to 3% and may decrease in the future. the results showed that the real death numbers had fallen into the predicted ranges. in addition, using the preliminary data from china, the piba method was successfully used to estimate the death rate and predict the death numbers of the korean population. in conclusion, piba can be used to efficiently estimate the death rate of a new infectious disease in real-time and to predict future deaths. the spread of 2019-ncov and its case fatality rate may vary in regions with different climates and temperatures from hubei and wuhan. piba model can be built based on known information of early patients in different countries. • the mortality rate determines whether a highly infectious disease becomes a public concern. • summarizing information after the fact does not contribute to real-time readiness to deal with the disease. • the patient information based algorithm (piba) estimates the death rate of a disease in real-time. • piba can be used to estimate the death rate of a new infectious disease in real time and to predict future deaths. a b s t r a c t a r t i c l e i n f o the mortality rate is the most important factor that determines whether a highly infectious disease becomes a public concern and carries risks causing a pandemic. different virus epidemics take place throughout the world every year, but only a few rise to the level of public concern (schlagenhauf and ashra, 2003; viboud and simonsen, 2012; who ebola response team, 2014) . severe acute respiratory syndrome (sars), swine influenza a h1n1 virus (h1n1), and zaire ebolavirus (ebola) brought on the public's attention because they caused many severe infections and thousands of deaths (dawood et al., 2012; nicholls et al., 2003; who ebola response team, 2014) . similarly, the disease covid-19 caused by a coronavirus (2019-ncov) brought world-wide attention and caused public panic because many deaths had been reported without being put in the context of the many mild infections and its potentially low case fatality rate (chan et al., 2020; huang et al., 2020; wang et al., 2020; wu et al., 2020) . for example, despite being a common infection, influenza rarely causes public concern because even though it is common, it leads to death in only 0.1% of cases. a variety of reports indicate that 2019-ncov is highly infectious through multiple routes huang et al., 2020; wu et al., 2020) . while the high infection rate is certain, the mortality rate of covid-19 has not been definitively determined. it is reasonable to suspect that the deaths of six of the first 41 patients (15%) in wuhan (huang et al., 2020) in the earliest reports by chinese scholars were inaccurate. when the initial mortality rates were reported, only patients who were critically ill were included. patients with mild symptoms, as well as those with asymptomatic infections, were not analyzed huang et al., 2020; wu et al., 2020) . case-fatality rates reported by huang et al. (2020) analyzed a skewed patient sample since it included only a small number of patients who had been transferred from other hospitals due to their critical condition. therefore huang et al.'s sample was skewed towards a concentration of severely ill patients, while the general patient population includes more patients with covid-19 who are asymptomatic or only have mild symptoms and who have not been hospitalized. chen et al. (2020) reported an 11% death rate, again based on patients with severe conditions. we have estimated the mortality rate using a patient information based algorithm (piba). the piba uses patient data in real-time to build a model that estimates and predicts death rates for the near future. piba uses data of patients identified early in the disease process to calculate the average number of days from hospitalization to death for those hospitalized. another feature is to take into account variations based on mathematical models. the piba calculation method does not divide the total number of patients on a day by the number of deaths on the same day. instead, the piba calculation method divides the number of deaths on that day by the number of possible patients of a day or days when the patients have just begun to develop the disease. thus, piba comprehensively and reasonably estimates the mortality rate based on the actual number of deaths and estimates the number of patients on a specific day. as time goes on, large amounts of data from northern and southern china have been accumulated through continuous reporting, all of which are used by piba, which then becomes more accurate as data accumulates. we conclude that it is time to utilize the accumulated data to estimate the case fatality rate of covid-19 infection. based on national data from the china national health center, the covid-19 death rate is much lower than that reported in huang et al. (2020) . holistic data covering all of wuhan, the epicenter city of covid-19, also indicates a death rate lower than that reported by huang et al. these data sources cover a larger patient sample, and include patients displaying symptoms with varying levels of severity. therefore, the updated estimation of the death rate should reference these larger scale and more representative data. our study contributes to knowledge on covid-19 death rate by building on huang et al.'s (2020) estimation and available data from official websites and addressing the limitations with a larger and more representative sample. 2.1. steps for estimating and predicting mortality using piba 1) to collect data from the patient's initial admission to death. strive to collect data for a certain number of patients. 2) to calculate the average number of days (μ) from hospital admission to the death and the number of days between one standard deviation (μ ± σ) interval and two standard deviations (μ ± 2σ). 3) to use these parameters (μ, μ ± σ, μ ± 2σ) to calculate the daily mortality during the epidemic. 4) to predict the mortality of infectious diseases in the future based on the calculated known mortality combined with the number of patients in a region. the predicted numbers are compared with real mortality to test and correct model data. 5) to conduct following-up modification of the piba model according to different nationalities and regions. in particular, the initial patient data collected may vary significantly from country to country, one ethnic group to the other, and region to region. the calculation based on the number of deaths and the number of patients on the same day does not reflect the real death rate because most patients with covid-19 do not die on the same day that they entered the hospital (chan et al., 2020; huang et al., 2020; wang et al., 2020) . with the piba method, we recognize that the patient population size was inaccurate in the early days but trust the published information of patients who died right after covid-19 outbreaks. the estimation is built upon data from patients with a normal distribution model. based on information about patients in wuhan who died during the period between dec 16, 2019, to jan 2, 2020 (huang et al., 2020) , two parameters were used to estimate days from onset of symptoms to death and days from admission to the intensive care unit (icu) to death. these two parameters are adopted in the estimation and prediction of covid-19 death rate. each parameter has five values including the mean, μ, one standard deviation from the mean, μ ± σ, and two standard deviations from the mean, μ ± 2σ. we collected data from covid-19 patients in china from three public websites. the data from the whole country are collected and made available on the official website of the health emergency office of the national health commission of the people's republic of china at http://www.nhc.gov.cn/yjb/new_index.shtml. the data from hubei province and wuhan are from the health commission of hubei province at http://wjw.hubei.gov.cn/fbjd/dtyw/. these data include the number of patients with covid-19 who were confirmed as having the disease, who died from the disease, whose condition was severe, and who were admitted to the hospital or icu. other collected data included daily new cases, new deaths, people who were in close contact with an infection source, and accumulated number of patients. we paid particular attention to data from wuhan, plus two additional cities in hubei province, xiaogan, and huanggang, in which the number of patients was higher than in other cities in hubei province. information from a northern province, heilongjiang province, was collected from the official website of outbreak information of the health commission of heilongjiang province at http://wsjkw.hlj.gov.cn/index. php/home/zwgk/all/typeid/42. data of heilongjiang province and harbin city were included because the province is located in the northern high-altitude zone. these data are used to assess whether the covid-19 is more, less, or equally likely to spread to an area with a cold climate. collected information included numbers of patients and numbers of deaths from each city and in the whole province. for any missing data in any day, a formula was used to estimate the data in that day: ni = {(n(i + j) + (n(i − j)) / (j + 1)} + (n(i − j), where ni = the estimated value of the missing data of the day i. j is the number of days of missing data, usually is 1; in the rare case, data of two consecutive days may be missing. if the data of two days are missing, the first day will be considered as the day i, the second day n (i + 1) will be calculated as n(i + 1) = ni + {(n(i + j) + (n(i − j)) / (j + 1)}. based on the days between confirmation of covid-19 and the days of death in the hospital, calculated from wuhan, as mentioned in method 1 and information from the whole country and hubei province, we tested the number of days from diagnosis to death, that most likely reflects the actual death rate. the estimated days are used to estimate the death rate using data from hubei province and wuhan city with the five values from above (μ, μ ± σ, μ ± 2σ). in consideration of the contribution of a variety of sources for the estimation, we fractured the data from (μ, μ ± σ and μ ± 2σ) into the piba and built the testing model as follows. 1) m i = (d i − d i−1 ) / (p i−n − p i−n−1 ) (death rate at increments) 2) m i = d i / p i−n (death rate at accumulative numbers) where m i = mortality rate, d i = the cumulative numbers of deaths on day i, p i = the cumulative numbers of patients on day i , i = the current day for calculating the death rate, n = the number of days from severe infection to death. when we considered these five partial values in normal distribution as a good indicator with a width of one standard deviation, each one of the five death rates calculated above on each day would have its own weight as the possible normal distribution (μ = 38.2%, μ − σ = μ + σ = 24.2%, and μ + 2σ = μ − 2σ = 6.7%). from here, we could give the death rate for every single day just a single value that results from the weighted average of all five cohorts of patients, as defined by time from severe illness to death. the equation is as follows: where d = death rate, mμ = mortality rate with μ days, wμ = weight with μ days gap, μ = mean in normal distribution, σ = standard deviation. 2.5. confirmation of the best estimation of the days to calculate the death rate in the other cities the same formula was then used to estimate the death rate from the other two cities in hubei province, namely xiaogan and huanggang. the piba model was developed using data from hubei province, including a. distribution of days between disease symptoms and death and between time of icu admission and death. vertical axis: days, horizontal axis: cases. b. estimated days from first symptoms to death and days from icu admission to death. c. lagging days (days from first symptoms to the day of death), μ, μ ± σ and μ ± 2σ and their weight (in percentages) used for the estimation of death rate in the broader patient population. note: among these values above, the lagging day μ − 2σ from symptom confirmation to death in panel b that equals to −3 has been set to 0. wuhan, xiaogan, and huanggang, and was further validated using data from heilongjiang province and harbin city. piba was then used to predict trends in new number of deaths. in order to further test the validity of our piba method in predicting actual mortality, we used a combination of the curve trend data and the overall mortality rate of the country, hubei, wuhan, and the rest of the country (china overall except hubei). based on our prediction of the days from actual hospitalization to death, we separately predicted the number of deaths in each day of the coming week. that is, from the comprehensive information of the number of new patients on the seventh day, the 13th day, and the 19th day before the targeted prediction day, we obtained three numbers of deaths for each of the predicted days. then from three of these numbers, the lower and upper values of the number of deaths on that day are used as the minimum and the maximum number of predicted deaths on that day, respectively. also, the same formula was used to predict the death number of a week in south korea. using information published by wuhan, we calculated the days between icu admission and death. we obtained the actual data from 33 patients who died in the hospital in wuhan. the days from onset of symptoms to deaths ranged from 6 to 30 (see fig. 1a ). from icu intake to death, the shortest number is one day, and the longest is 22 days. we derived two parameters, each from the 33 death cases, i.e., the days from onset of symptoms to death and the days from inpatient admission to death. since there are six patients out of these 33 death cases who have the same date of symptoms' appearance and inpatient, there were 33 values in the dataset related to inpatient and 27 values in another dataset related to symptoms' appearance (fig. 1a) . the results indicated that the average time from onset of the symptoms to death is 13 days (m = 13, s.d. = 6) (see fig. 1b ). accordingly, the lagging days from the day of death and their weight in the calculation of death rate were derived based on the new inpatient days (fig. 1c) . the prediction of death rate is based on data from wuhan city in which patients diagnosed with covid-19 had been confirmed since january 19, 2020 and where deaths had occurred, which were among the first confirmed cases of coronavirus. 3.2. estimated death rate for the whole country and hubei province using piba formula according to our five estimation parameters, from illness (i.e., symptom appearance) to death, the maximum number of days is 25 days. the earliest reported data in wuhan was published on january 19, 2020. based on these data, we were able to calculate the mortality rate from february 8, 2020, to the present. however, on february 12, the national health committee revised the data again (see appendix table 1 ). because of this amendment, the number of confirmed cases appeared to have changed significantly in only one day. we chose the calculation results from february 14 up to february 25 (appendix table 2 ), considering that the death rates on february 12 and february 13 are likely distorted by this sharp rise within a short term. fig. 2a through d provide information about the overall death rates in mainland china (hereafter referred to as country), hubei, wuhan, and rest of country (excluding hubei) (appendix table 3 ). we noticed that the death rate at increments based on piba in the whole country (in blue) in fig. 2a is below 10%, with most values between 2.7% and 6% in the last five days. the death rate in hubei province is similar to that of the whole country because 90% of the patients in the whole country were from hubei province (see appendix table 1 ) (fig. 2b) . in wuhan, the accumulated death rate was still high, as much as 20% (fig. 2d ). when we used the data from the rest of the country to test our piba formula, as expected, the curve is different from the curves from hubei and wuhan. unlike in hubei and wuhan, the death rate of the rest of the country is much lower and stable, mostly lower than 1% (fig. 2c) . the predicted death rate will remain between 1% and 2% for the near future. xiaogan and huanggang are the two cities in hubei province. the number of patients with covid-19 in these two cities is higher than in other cities in hubei except wuhan. they also are the cities with the largest number of patients with covid-19 in china. we, therefore, tested the piba formula using data from these two cities. currently, the death rate based on the increment data is around 3%, lower than that in wuhan but higher than that in the rest of the country. however, according to piba, the rate of deaths may decrease in the near future. heilongjiang province, including its capital city, harbin, is the province outside of hubei with the largest number of diagnosed patients. harbin city is located in the northeast of china and is in the coldest area in china. no patients from harbin city or the heilongjiang province were reported during the sars epidemic period. we used the piba formula to estimate the death rate in both the heilongjiang province (fig. 3c) and harbin city (fig. 3d) . the death rate of harbin decreased sharply in the past several days, into 0%. the low rate of less than 1% will possibly remain for the future. based on the piba and the death rate of accumulated numbers, the expected final death rate of the whole country, hubei, wuhan, and rest of the country except hubei, is predicted as follows (see table 1 ). the predicted values are from the intersection points between the incremental estimation and net values estimation. we used the predicted death rate to calculate the potential number of deaths per day in the coming week. because our initial estimation on the lagging days between inpatient and death was only based on 33 fig. 3 . death rate estimations of four places. the blue curve represents the mortality calculated by the actual increase in deaths per lagging day divided by the increase in actual patients on the previous corresponding day. the gray curve represents the total number of deaths per lagging day, divided by the total number of identified actual patients on the corresponding previous day. the orange curve shows the number of deaths per day divided by the total number of patients the same day. numbers on the vertical axis represent the death rate; on the horizontal axis is the date. a. the death rate of xiaogan city in hubei province b. death rate of huanggang city in hubei province. c. the death rate in heilongjiang province. d. the death rate in harbin city. patients, we, therefore, used the days of average 13 days plus (19 days) and minus one standard deviation (7 days) as the range of number of deaths on a given day in the coming week (see appendix table 4 . predicted number of deaths in the days of the coming week after february 25, 2020). as shown in fig. 4 , the actual number of deaths in the past four days fell into the predicted range. in the country (fig. 4a) , hubei (fig. 4b) , and wuhan (fig. 4c) , the numbers of actual death were near the predicted minimum numbers. while, for the rest of the regions of the country except hubei, the actual death data fluctuates between the predicted maximum and minimum values (fig. 4c) . due to the number of newly infected patients dropping in the last few days, the total number of patients tends to be constant or even less in the coming days if unexpected events do not occur. the peaks in these figures reflect sudden changes in numbers of patients (see fig. 4 ). we believe that the intersecting point between the trendlines could reasonably be considered one of the rates in its range of the death rate of patients infected in the future. as shown in the data above, the incidence in mainland china's provinces and cities was basically zero in late middle march. because of this, we were not able to prove the feasibility of this method in more regions in mainland china. however, because the environment, medical conditions, and population races in different countries are different, to test the usefulness of the piba model in other countries, we need to get the basic information of the initial population. this information includes the specific number of days from onset to death of a reasonable number of patients in different regions of different countries. at present, we could not access these data accurately. the only thing we can do is to test asian countries such as south korea and japan based on their ethnic similarities with populations in china. taking all aspects into consideration, we believe that south korea's data are more reliable. therefore, fig. 4 . comparison between the predicted number of deaths based on piba and the actual number of deaths. the blue color represents the estimated minimum number of deaths line. the orange color represents the estimated maximum number of deaths line. the gray line represents the actual number of deaths. panels a, b, c, and d showed these death numbers in the country, hubei, wuhan and the rest of country except hubei. we further tested our model using the affected population in south korea. as shown in fig. 5 , the trend of deaths in south korea in recent days is consistent with our prediction. first, piba is capable of accurately estimating the disease mortality and the number of future deaths. this real-time accurate prediction and estimation of disease mortality provide the public, government, and society with more accurate disease information. based on currently available data that includes patients with varying degrees of severity, the estimated prediction of the mortality rate of covid-19 is less than 3%, and less than the prior prediction based on limited available data. this finding may ease public concern and panic. updated scientific findings will be widely disseminated to broaden public awareness and contribute to helping fight covid-19. the medical, clinical, and research community should strive to publish scientifically rigorous findings related to urgent public health issues. publishing findings based on the availability of limited data contributes to unnecessary public concern and government action. in this particular case, the first report on the estimation of coronavirus death rate is an applaudable effort. however, it also had the limitations of a skewed dataset that focused on patients who were transferred from local hospitals because of their critical condition while excluding patients with less severe symptoms who remained at local hospitals. as soon as more data are available, we should provide updated reports and introduce improved estimation and prediction algorithms. this study indicates that as the number of transmissions of 2019ncov increases among the human population, its lethality will gradually decrease. indeed, the reasons are not necessarily all because of their reduced toxicity. there may also be improvements in treatments and implementation of early detection methods. therefore, a real-time estimate of death rate using patient information such as the piba method would demonstrate an appreciation of the importance of public and societal awareness. a critical issue to consider is that if the mortality rate of the covid-19 in a certain area is relatively high, the covid-19 in the area is still spreading and endemic. one of the most obvious questions is why the fig. 5 . test piba model using covid-19 population from south korea. a. estimation of death rate in the korean population using the piba method. the blue curve represents the mortality calculated by the actual increase in deaths per lagging day divided by the increase in actual patients on the previous corresponding day. the gray curve represents the total number of deaths per lagging day, divided by the total number of identified actual patients on the corresponding previous day. the orange curve shows the number of deaths per day divided by the total number of patients the same day. the number on the vertical bar represents the death rate, number on the horizontal bar shows the date. b. comparison between the predicted number of deaths based on piba and the actual number of deaths. the blue color represents the estimated minimum number of deaths line. the orange color represents the estimated maximum number of deaths line. the gray line represents the actual deaths. mortality rate in wuhan is considerably higher than in other places. based on our assessment, wuhan's medical equipment and rescue measures are comparable with other areas in china, and the pathogenicity of the virus is similar. we conclude that there is a large proportion of patients in wuhan who have mild illness and not been hospitalized at all. due to the uncertainty of the movement of infected people in the early stages of the onset, these mildly ill people move around in wuhan unidentified. this problem reminds other parts of the world that if the fatality rate of the covid-19 is found to be high, a large number of infected people have not been able to be identified or diagnosed. therefore, the work of controlling and isolating this infected group has not been completed, and the disease is still spreading and circulating in the area. the data on heilongjiang province and harbin show that, unlike some experts' predictions (cf. https://news.ifeng.com/c/7uhmhxcfhmq), it will occur more intensely in the high-altitude regions with a cold climate, and the mortality rate will be higher. with the development of the generations of 2019-ncov, its toxicity will gradually weaken, and we expect that the mortality rate in the cold northern regions will not increase, nor will it exceed that in wuhan or hubei province. our research has limitations, mainly due to available data. first, the estimation of number of patients from the date of hospital admission or icu intake to the date of death is based on data from official public websites. information from 33 individuals was estimated. if the information had been available regarding more patients, the initial estimate would have been more accurate. the second aspect is the accuracy of the number of patients diagnosed and the number of hospitalizations per day. due to the back and forth revision and correction of the data as announced by the official sources, we are not confident that all the data are error-free; however, we feel that these data as a whole are reliable. the third limitation of the piba method is that it depends on accurate patient information at the beginning of the epidemic. depending on different situations from different countries or regions, this information may or may not be available, or the information may not be accurate. the piba model accurately predicted a case fatality of 1.6% for symptomatic patients in china at a very early stage in the covid-19 pandemic. the model can be generalized to predict case fatality for any infection (including asymptomat), to predict the rate of severe disease, and to predict the death rate for patients who develop severe disease. these early, accurate predictions inform the public, society, and governments to estimate the extent of the disease's harm and to develop suitable strategies. supplementary data to this article can be found online at https://doi. org/10.1016/j.scitotenv.2020.138394. the authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. a familial cluster of pneumonia associated with the 2019 novel coronavirus indicating person-to-person transmission: a study of a family cluster epidemiological and clinical characteristics of 99 cases of 2019 novel coronavirus pneumonia in wuhan, china: a descriptive study estimated global mortality associated with the first 12 months of 2009 pandemic influenza a h1n1 virus circulation: a modelling study clinical features of patients infected with 2019 novel coronavirus in wuhan lung pathology of fatal severe acute respiratory syndrome severe acute respiratory syndrome spreads worldwide global mortality of 2009 pandemic influenza a h1n1 a novel coronavirus outbreak of global health concern ebola virus disease in west africa-the first 9 months of the epidemic and forward projections nowcasting and forecasting the potential domestic and international spread of the 2019-ncov outbreak originating in wuhan, china: a modelling study this work was partially supported by funding from merit grant i01 bx000671 to wg from the department of veterans affairs and the veterans administration medical center in memphis, tn, usa and grant 90dduc0058 to cg from u.s. department of health and human services, administration for community living. revise and approve and manuscript: all authors. all the data of patients in this study are from official public websites. key: cord-293139-uj1m3t79 authors: hua, jinxi; zhang, yuanxun; de foy, benjamin; mei, xiaodong; shang, jing; feng, chuan title: competing pm2.5 and no2 holiday effects in the beijing area vary locally due to differences in residential coal burning and traffic patterns date: 2020-08-11 journal: sci total environ doi: 10.1016/j.scitotenv.2020.141575 sha: doc_id: 293139 cord_uid: uj1m3t79 abstract the holiday effect is a useful tool to estimate the impact on air pollution due to changes in human activities. in this study, we assessed the variations in concentrations of fine particulate matter (pm2.5) and nitrogen dioxide (no2) during the holidays in the heating season from 2014 to 2018 based on daily surface air quality monitoring measurements in beijing. a generalized additive model (gam) is used to analyze pollutant concentrations for 34 sites by comprehensively accounting for annual, monthly, and weekly cycles as well as the nonlinear impacts of meteorological factors. a saturday effect was found in the downtown area, with about 4% decrease in pm2.5 and 3% decrease in no2 relative to weekdays. on sundays, the pm2.5 concentrations increased by about 5% whereas there were no clear changes for no2. in contrast to the small effect of the weekend, there was a strong holiday effect throughout the region with average increases of about 22% in pm2.5 and average reductions of about 11% in no2 concentrations. there was a clear geographical pattern in the strength of the holiday effect. in rural areas the increase in pm2.5 is related to the proportion of coal and biomass consumption for household heating. in the suburban areas between the fifth ring road and sixth ring road there were larger reductions in no2 than downtown which might be due to decreased traffic as many people return to their hometown for the holidays. this study provides insights into the pattern of changes in air pollution due to human activities. by quantifying the changes, it also provides insights for improvements in air quality due to control policies implemented in beijing during the heating season. particles (pm 2.5 ) and nitrogen dioxide (no 2 ), there have been conflicting results. (cui et al., 2020) found concentrations of thirteen elements in pm 2.5 were higher on weekends than on weekdays. (beirle et al., 2003; chen et al., 2015; liu et al., 2016) did not find a clear weekly pattern in the beijing area. these studies did not consider the effect of meteorology on pollutant concentrations. the regional transport plays an important role in the air pollution of beijing: a clear spatial pattern was observed with decreasing concentrations from south to north (li et al., 2015) . because meteorology has a strong impact on air pollution in the region, it must be taken into account to prevent biases in the estimates of human-related air pollution changes (sun et al., 2013; sun et al., 2015; wang et al., 2017a; . in addition to meteorology, local emissions also affect air quality. the main anthropogenic sources of air pollution in beijing during the heating season are coal-burning for heating and vehicle emissions due to rapid urbanization xu et al., 2019) . a series of measures were implemented to improve air quality in the city, such as "action plan on prevention and control of air pollution" (zhang et al., 2016) , "joint prevention and control of atmospheric pollution" , "coal to electricity" and "coal to gas" projects (shuxue et al., 2020) . the actions have been found to effectively reduce the pm 2.5 and no 2 concentrations (barrington-leigh et al., 2019; cheng et al., 2019; de foy et al., 2016b; wang et al., 2017b; zhang the holiday effect is similar to the weekend effect in that it is a measure of the difference in pollution levels between holidays and non-holidays (tan et al., 2013) . in general, it shows higher concentrations during non-holidays and lower concentrations during holidays. the holiday effect is due to changes in human activities which are influenced by lifestyle, urbanization, energy consumption structure, and traditional culture (forster and solomon, 2003; liu et al., 2019; seidel and birnbaum, 2015) . when there is no clear weekend effect, the holiday effect provides a useful tool to identify changes in air quality due to changes in human activities (chen et al., 2019) . (madhavi latha and highwood, 2006) found coarse particulate matter (pm 10 ) concentrations are lower during the christmas holidays than non-holidays in the united kingdom, which are mainly due to reductions of local traffic emissions. (chen et al., 2019; tan et al., 2009) investigated the difference of six air pollutants in taipei between the spring festival and non-spring festival, finding significant reductions during the spring festival for nitrogen oxides (no x ), carbon monoxide (co), volatile organic compounds or non-methane hydrocarbon (nmhc), sulfur dioxide (so 2 ), and pm 10 , while o 3 concentrations increased due to a reduction in the titration effect. (tan et al., 2013) reported a distinct spatial holiday effect associated with the degree of urbanization in taipei and found that the holiday effects of no x , co and nmhc become greater when the population, and hence the number of motor vehicles increases. was available from the beijing municipal environmental monitoring center (http://www. bjmemc.com.cn/). these sites are designed to reflect urban background conditions, regional transmission, traffic pollution, and urban air quality, covering most of the spatial range and multiple land use types (ji et al., 2019; sun et al., 2019) . for each site, daily averages were calculated from the valid data points when data was available for more than 10 hours per day. the location of the sites and the number of observations as shown in table s1 . pm 2.5 and no 2 were available for more than 95% of the days for most sites during the study period (756 days in total). beijing includes 16 administrative regions ( fig. 1) , with a total population of 21.54 million in 2018 (beijing municipal bureau of statistics) and an area of 16,410km 2 (dong et al., 2018) . rapid urbanization caused a drastic expansion from core districts (dongcheng and xicheng). the area within the fifth ring road is considered the most densely populated area with around half of the inhabitants and only 4% of the surface area of beijing (xin , dong, et al., 2018 . due to relatively short commuting time and cheap housing, the area between the fifth ring road and the sixth ring road accounts for 27% of the population of beijing city (xin zhang, 2019). outside the sixth ring road, the population density is relatively sparse, and rural residents account for a large proportion, with approximately 86% of land area only 24% of the population (xin zhang, 2019 , dong, et al., 2018 . different population distribution and development patterns will lead to variations in air pollution due to variations in human activities. to explore the spatial variation of the holiday effect, the sites were clustered by geographical locations based on different population and development patterns (fig. 1) . the sites within the fifth ring road were defined as downtown, the sites between the fifth ring road and the sixth ring road were defined as suburban, the sites outside the sixth j o u r n a l p r e -p r o o f journal pre-proof the holiday periods referred to new year"s day (january 1), the spring festival (lunar new year), and the lantern festival based on the national legal holiday arrangements issued by the state council. the spring festival is the most important holiday involving family reunions, and it will bring travel peaks of people returning to their hometowns before the festival and then back to work afterwards. for the purposes of this study, the festival holiday period is defined as starting two days before the eve of the spring festival and finishing four days after the spring festival. this excludes the influence of the travel peaks which occur before and after that . the specific dates are listed in table s2 . overall, the holiday periods last around ten days each year. in this study, the non-parametric mann-whitney u test, which does not require the data to be normally distributed (chen et al., 2019) , was used to compare the pollutant concentrations and meteorological observations during the holidays and non-holidays, weekends and weekdays. the predictors in our gam model include time vectors to represent inter-annual, monthly, and weekday variations, as well as meteorological variables (boundary layer height, east-west wind component, south-north wind component, relative humidity, air temperature, dew point temperature, and surface pressure). the time factors were defined as linear terms, and the meteorological variables were defined as smooth terms. the equation is as follows: s (·) is the p-spline smoothing function that optimizes the fitting and controls the smoothness through a penalty term. s 1 (blh) are the smoothers that characterize the non-linear influence of boundary layer height on the measurements. s 2 (u, v) are interaction terms that denote the influence of horizontal ventilation due to zonal and meridional wind speeds. " " represent the meteorological variables selected in the candidate list based on their contribution to the model r 2 . the candidate list included relative humidity, air temperature, dew point temperature, and pressure. to avoid the collinearity problem, the test process input only one variable to gam at a time. the one leading to the greatest increase in correlation coefficient was included. all meteorological variables were scaled linearly in order to approximate the normal distribution of zero mean to reduce the effects of extreme observations. after considering the impact of meteorological parameters, a net contribution to the time cycle can be obtained from the regression coefficient. in this way, temporal profiles are closer to changes caused by emissions than meteorological factors. the temporal indicators are input for each year, each month, and each day of the week, and therefore do not have a unique solution. as described j o u r n a l p r e -p r o o f journal pre-proof in (de foy, 2018), a weighting factor of one was used on the penalty term for the regression coefficients which solves the dummy variable trap problem while also forcing  to have the smallest possible values. the gam results can be interpreted using equation (2): where p corresponds to the percentage change in the concentration during the time intervals relative to long-term averages. block-bootstrapping (de foy and schauer, 2015; requia et al., 2019) with seven-day chunks was used to estimate the uncertainty of the linear terms. the model was obtained 100 times using a randomly resampled dataset each time. when resampling the dataset, the data points to be included were selected at random with replacement so that each dataset was of the same size as the original. the standard deviation of the temporal coefficients was obtained from the 100 model simulations. the 95% confidence interval of the nonlinear terms in equation (1) and 20% lower no 2 concentrations ( table 1) . the mean (± sd) pm 2.5 concentrations are 96±82μg/m 3 and 81±80μg/m 3 in holidays and non-holidays, respectively. the mean (± sd) no 2 concentrations are 44±29μg/m 3 and 55±31μg/m 3 during holidays and non-holidays, respectively. daily means of pm 2.5 and no 2 between the holidays and non-holidays, weekends and weekdays periods were found to be statistically different with p<0.01 using the mann-whitney u test (table 1) . meteorological variables were also statistically different, which means that it was important to consider these factors in the model in order to properly quantify the human-related air pollution changes. during the holidays, the mean blh is 47m lower than non-holidays and the air temperature is around 3℃ lower. the main reason for the difference is that the holiday periods fall mainly within january and february which are colder than march. the same weather parameters from era5 and isd show a consistent bias: blh, d2m, t2m, rh, sp, and u are lower during the holidays and v is higher. the average standard deviations of pm 2.5 scaling factors are around 4.5% and 9.9% in non-holidays and holidays, respectively, and they are stable from site to site ( table s3 ). the relatively high uncertainty of holiday effects is due to the fact that there are fewer data points for the holiday periods than for the non-holidays. for no 2 , the uncertainty of non-holidays is around 1.5% and for holidays it is around 2.6%. the uncertainty for pm 2.5 is higher than no 2 mainly because pm 2.5 concentrations are affected by complex factors such as various emission sources, air mass transport, chemical transformation, day-to-day carry over, and complex interaction effect j o u r n a l p r e -p r o o f between synoptic conditions and pm 2.5 (wang, et al., 2017 , khuzestani, et al., 2018 . the performance of the model fit was assessed by calculating the regression coefficient (r 2 ) and the root mean square error (rmse) using the 100 bootstrap runs ( fig. s1 and fig. s2) . overall, the gam estimates of the holiday effects were found to be robust for each site with respect to the selection of the optimal set of meteorological variables. the list of variables selected as input to the gam for each site is shown in table s1 . daily average boundary layer height and isd winds were included in most cases, and the average relative humidity was the optimal choice at the majority of sites during the sensitivity tests. we will take the site yz as an example to discuss the impact of meteorology on pollutant concentrations. the site is located in the plain area and near a subway station, which means that its topographic features are similar to most of the other sites and it is strongly impacted by human activities. the increase in the mixing layer height led to the strong diffusion of pollutants (miao et al., 2019) , leading to approximately a 65% decrease in pm 2.5 with one standard deviation increase in the boundary layer height at yz (fig. s3) . high relative humidity promotes the hygroscopic growth of particulate matter (cheng et al., 2015) , with about a 65% increase in pm 2.5 with one standard deviation increase in the relative humidity. beijing is surrounded by mountains to the west, north, and northeast; and the southeast is a plain that slopes slowly towards the bohai sea. because of the topographical features, the air quality at most sites is influenced by southerly winds. frequent northerly winds during the heating periods also transport air pollution from downtown to j o u r n a l p r e -p r o o f journal pre-proof yz site which is a suburban site to the southeast. for no 2 , an increase in one standard deviation of the boundary layer height is associated with a 22% decrease at yz (fig. s4) . higher relative humidity is associated with higher no 2 concentrations. except for the influence from southerly winds, local emissions were found to have high contributions to no 2 levels because the yz site is very busy as it is near a subway station. the 95% confidence interval range is very narrow for the meteorological parameters ( fig. s3 and for the day of the week profiles, the pm 2.5 scaling factors vary from site to site, but on average there is not much variation from monday to sunday (fig. 3, table 2 figure s8 ) suggesting that the weekend effects are robust with respect to spatial variability. the weekend effect in pm 2.5 can be clearly seen even though pm 2.5 is influenced by carry over on the scale of 3 to 5 days. while this shows that the weekend effect is strong enough to be identified over other factors, future analysis would be required to estimate the impacts of carry over, for example using aerosol chemical speciation. the probability distribution of percentage changes by type of day shows that the differences between the days are statistically significant. as an example, the distributions of pm 2.5 factors at wsxg are clearly different for saturdays, sundays and holidays, and the distributions of no 2 factors are clearly different for saturdays and holidays ( figure s9 ). this result updates the previous research on the weekend effect in beijing. (beirle et al., 2003; chen et al., 2015; liu et al., 2016) which showed that there was no obvious weekend effect for pm 2.5 or no 2 in beijing, mainly because the previous study mostly did not consider the impact of meteorological parameters and of spatial patterns. this implies that the gam analysis provides valuable information with respect to temporal variation and meteorological influence, and that a network of widely distributed monitoring stations can provide more subtle information on the weekend effect. suggest that there are multiple factors involved in the change of human-activities, as will be discussed in section 3.4. from downtown to suburban, to rural areas, there is a clear change in the holiday effects in the direction of a larger increase of pm 2.5 and a smaller decrease of no 2 (fig. 4) . for the most part, sites in close geographical proximity behave similarly, although there are a few outliers. dl, dgc, and tz exhibit different characteristics from the neighboring sites, probably because they are affected by local land use effects. for example, dgc is geographically close to pg, but dgc is surrounded by farmland and forest while pg is located in a residential area (fig. s10) , which suggests that the different holiday effects are due to local variations in land use type. dl was purposely designed to monitor urban background air quality surrounded by mountainous areas (chen et al., 2015; li et al., 2015) . these sites are excluded in the analysis that follows. for downtown, the changes are relatively consistent, with an increase in pm 2.5 concentrations ranging from 20.4% to 27.1% and a reduction in no 2 ranging from 8.6% to 12.5% ( table 2) . for most sites in the suburban region, the pm 2.5 changes are close to downtown sites with 19.5~25.1% increases, and the changes in no 2 are stronger than downtown with 12.0~15.7% decreases. the effects of holidays in rural areas are clearly distinct. for the pm 2.5 holiday effect, the southwest and northeast rural areas demonstrate the largest increases, being on average 30.6% higher than weekdays. the sites in the southeast and northwest areas show the lowest increases j o u r n a l p r e -p r o o f journal pre-proof with 12.2% changes on average. this pattern is similar to the feature of pm 2.5 emissions from household heating in (cai et al., 2018) , who developed a village-based emission inventory of household combustion based on the investigation of all villages in beijing. for no 2 , the sites in the southwest and northeast rural areas have the lowest decrease (7.3% on average) while the sites in the southeast and northwest areas have the highest decrease (14.6% on average). the pm 2.5 holiday effect consisted of increased concentrations ranging from 2% to 39% depending on the site. in contrast, the no 2 holiday effect consisted of decreased concentrations ranging from 3% to 18% depending on the site. that pm 2.5 has a stronger holiday effect than no 2 implies that there are greater differences in human activities for pm 2.5 emission sources. rural areas to the northeast of beijing experienced larger increases in pm 2.5 concentrations. these are mainly concentrated in miyun, huairou, and pinggu, which are districts in northeast beijing and are more heavily forested, and where coal and biomass burning is frequently used as a heating fuel (cai et al., 2018) . found that coal-fired boilers have been mostly eliminated from urban areas but remain in rural areas and especially in the districts of miyun, huairou, and pinggu in 2014. we compared the strength of the holiday effect with household energy consumption by town in most districts of beijing in 2017 provided by (cai et al., 2018) . for each rural measurement site, we calculated the average coal and biomass consumption in neighboring districts. the strength of the holiday effect in pm 2.5 in rural areas was found to have a positive correlation with coal and biomass consumption (fig. 5) . the northeast and southwest rural areas had a higher proportion of coal consumption for household heating than the northwest and southeast rural areas, and had a j o u r n a l p r e -p r o o f journal pre-proof correspondingly larger increase in pm 2.5 concentrations during the holidays. the spatial variation of the holiday effect suggests that indoor household heating activities could be a possible cause for the increases in pm 2.5 in rural areas. the results suggest that the promotion of the "coal to gas" project ( barrington-leigh et al., 2019; zhao et al., 2020b) will play an important role in improving air quality in beijing in the next few years. household heating is also a significant source of no 2 emissions (luo et al., 2019) , such that the no 2 emitted by coal combustion probably offset the reduction of no 2 due to reduced traffic. the area with more coal-fired activities have a smaller reduction in no 2 than the areas with lower coal-fired activities. therefore, the net no 2 holiday effect in rural areas is a result of two competing effects. for the area within the sixth ring road, although suburban areas and downtown show similar pm 2.5 increases, the suburban area exhibited an extra 2.7% reduction in no 2 relative to the downtown area. the difference is probably because the suburban area is home to a large number of commuters thanks to relatively cheap housing costs and short commute times, and consequently has a greater fraction of people traveling during the holidays (zhao et al., 2020a) . changes in travel patterns are particularly strong during the spring festival when a large number of people return to their hometown leading to reduced transportation emissions during the spring festival itself. to distinguish between the effect of different holidays it will be necessary to have a longer time series of measurements. in this study, we used gam to estimate the holiday effects of pm 2.5 and no 2 in beijing by concentrations increased by about 5% whereas there were no clear changes for no 2 . although there is uncertainty due to meteorological factors such as temperature, wind speed and direction, and boundary layer height, the weekend variations are consistent at all downtown sites and robust with respect to temporal variability. the holiday effect was found to be much stronger than the weekend effects, and had opposite signs for pm 2.5 and no 2 . there were increases in pm 2.5 ranging from 2% to 30% depending on the site. in contrast, no 2 decreased from 3% to 18% depending on the site. furthermore, a clear spatial pattern was found in the strength of the holiday effect. in the rural areas, the strength of the pm 2.5 increases were associated with the extent of coal and biomass consumption for household heating in districts surrounding the measurement sites. it is worth noting that the promotion of renewable energy can therefore be expected to improve air quality in rural hotspots as well as in the greater beijing area. in addition, the suburban area where more people travelled during the holidays experienced greater reductions in no 2 than the downtown area. the spatial variation in the holiday effect at different sites reflects two distinct ways that human activities impact air quality: increased residential heating tended to increase both pm 2.5 and no 2 , whereas reduced traffic emissions leads to lower no 2 . this study investigated the holiday effect in beijing, providing evidence for the influence of human activities on air quality on short time scales. studies of the holiday effects as well as other natural experiments such as the impacts of the olympic games (liu et al., 2012) , apec blue (gao et al., 2017; sun et al., 2016) , and new studies emerging on the impact of the covid-19 lockdown (bauwens et al., 2020; chauhan and singh, 2020; wang and su, 2020) will provide valuable information for the formulation of policies for both holiday and non-holiday periods. pollutant emissions from residential combustion and 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pollution in beijing and the implications relative impact of emissions controls and meteorology on air pollution mitigation associated with the asia-pacific economic results of investigation on population distribution of beijing's various ring roads. favorite big beijing nitrate dominates the chemical composition of pm2.5 during haze event in beijing trends of multiple air pollutants emissions from residential coal combustion in beijing and its implication on improving air quality for control measures a study on the model for heating influence on pm2.5 emission in beijing china air pollution and control action in beijing mass human migration and beijing"s urban heat island during the chinese new year holiday historic and future trends of vehicle emissions in beijing, 1998-2020: a policy assessment for the most stringent vehicle emission control program in china long-term trends in no2 columns related to economic developments and air quality policies from 1997 to 2016 in china long commutes and transport inequity in china"s growing megacity: new evidence from beijing using mobile phone data effect of the "coal to gas" project on atmospheric nox during the heating period at a suburban site between beijing and tianjin pollution levels, composition characteristics and sources of atmospheric pm2.5 in a rural area of the north china plain during winter human activities and urban air pollution in chinese mega city: an insight of ozone weekend effect in beijing village energy survey reveals missing rural raw coal in northern china: significance in science and policy this work was supported by the national natural science foundation of china (nsfc, no. j o u r n a l p r e -p r o o f key: cord-329050-vzsy6xw1 authors: nabi, ghulam; wang, yang; lv, liang; jiang, chuan; ahmad, shahid; wu, yufeng; li, dongming title: bats and birds as viral reservoirs: a physiological and ecological perspective date: 2020-09-22 journal: sci total environ doi: 10.1016/j.scitotenv.2020.142372 sha: doc_id: 329050 cord_uid: vzsy6xw1 the birds (class aves) and bats (order chiroptera, class mammalia) are well known natural reservoirs of a diverse range of viruses, including some zoonoses. the only extant volant vertebrates, bats and birds have undergone dramatic adaptive radiations that have allowed them to occupy diverse ecological niches and colonize most of the planet. however, few studies have compared the physiology and ecology of these ecologically, and medically, important taxa. here, we review convergent traits in the physiology, immunology, flight-related ecology of birds and bats that might enable these taxa to act as viral reservoirs and asymptomatic carriers. many species of birds and bats are well adapted to urban environments and may host more zoonotic pathogens than species that do not colonize anthropogenic habitats. these convergent traits in birds and bats and their ecological interactions with domestic animals and humans increase the potential risk of viral spillover transmission and facilitate the emergence of novel viruses that most likely sources of zoonoses with the potential to cause global pandemics. the coronavirus disease 2019 caused by the severe acute respiratory syndrome coronavirus 2 (sars-cov-2) was characterized as a global pandemic on 11th march 2020 (world health organization, 2020) . the covid-19 pandemic has had a dramatic socio-economic impact due to its exceptionally rapid spread and higher number of deaths (cash and patel, 2020; weiss and murdoch, 2020) , particularly among older age groups (mahase, 2020) . epidemiological research has revealed that free-living bats are likely the native host of the sars-cov-2 (zhou et al., 2020) . other recent viral epidemics are also believed to have originated from either bats or birds (calisher et al., 2006; chan et al., 2015; olival et al., 2017; nabi et al., 2020) . indeed, bats or birds are thought to host many pathogens (morse et al., 2012; chan et al., 2013; hayman, 2016; olival et al., 2017; woolhouse and brierley, 2018) . the relatively high number of zoonoses carried by birds and mammals is highly correlated with their diversity at the order level (mollentze and streicker, 2020) . birds (class aves) and bats (order chiroptera, class mammalia) have both undergone dramatic adaptive radiations; there are over 10,000 bird species (avibase; https://avibase.bsc-eoc.org/) and 1,400 bat species, and both taxa have a global distribution (wilson and mittermeier, 2019) . the high diversity of birds and bats provides an abundance of potential reservoirs for a diverse range of viruses (calisher et al., 2006; hayman, 2016) , especially recently emerging, high-profile zoonoses j o u r n a l p r e -p r o o f (olival et al., 2017; woolhouse and brierley, 2018) . why are birds and bats reservoirs of so many zoonotic viruses chen et al., 2014; hayman, 2016; olival et al., 2017; miłek and blicharz-domańska, 2018; venkatesh et al., 2018; wong et al., 2019) ? one explanation lies in their many shared, convergent features, such as small body size, high population densities, close social interaction, spatial mobility, and the ability to colonize anthropogenic environments chan et al., 2015) . these features predispose birds and bats to act as viral reservoirs and to transmit viruses to other vertebrates, including humans. however, few studies have compared the physiology and immunology of these ecologically, and medically, important taxa (caviedes-vidal et al., 2007; mollentze and streicker, 2020; song et al., 2020) . this paper reviews convergent traits in the physiology, immunology and flight-related ecology of birds and bats with the aim of a better understanding of why these species are such important reservoirs of viral zoonoses, and the potential risk of bat and bird viruses infecting humans. wild birds are reservoirs of many emerging zoonotic viruses (reed et al., 2003; abulreesh et al., 2007) . for example, a large variety of influenza a viruses are hosted by wild aquatic birds in the orders of anseriformes and charadriiformes (olsen et al., 2006) . approximately 300 avian species have been confirmed to carry the west nile virus (cdc, 2019) and also others gamma-and delta-covs have been detected in multiple avian orders on all continents hughes et al., 2009; chu et al., 2011; chamings et al., 2018) . the majority of viral infections in birds are either typically of low pathogenicity or asymptomatic (olsen et al., 2006; kuiken, 2013; lycett et al., j o u r n a l p r e -p r o o f journal pre-proof 2019). however, in recent years, several birds-borne viruses, such as the highly pathogenic avian influenza virus (hpaiv) a (e.g., h5n1 and h7n9) and infectious bronchitis viruses (ibv), have caused major epidemics and mortality among humans or domestic animals (alexander, 2007; bui et al., 2016; wang et al., 2020) . bats, primates, and rodents not only have the greatest viral richness among mammals but also harbor a higher proportion of zoonotic viruses than other mammalian taxa (olival et al., 2017; mollentze and streicker, 2020) . bats host a greater diversity of viruses than non-flying mammals, including the paramyxoviruses (drexler et al., 2012) , the rhabdoviruses (rupprecht et al., 2017) , the hepaciviruses, the pegiviruses (quan et al., 2013) , and the influenza a viruses (tong et al., 2013) . the updated bat-virus database indicates that 301 bat species host viruses with all known viral genomic structures and replication strategies according to the baltimore classification system (http://www.mgc. ac.cn/dbatvir/; (chen et al., 2014; hayman, 2016) . bats are believed to host the ancestors of all major mammalian paramyxoviruses (drexler et al., 2012; hayman, 2016) ; those hosted by non-flying mammals and birds originated from bats (drexler et al., 2012) . in the past two decades, domestic mammals and humans have contracted several viruses from bats including sars-cov-2 (zhou et al., 2020) , the virus that is causing the current global pandemic, but also sars-cov, the middle east respiratory syndrome coronavirus (mers-cov), the ebola virus, the marburg virus, and the rabies virus (cui et al., alpha-and beta-covs (woo et al., 2012) . birds (particularly aquatic birds) are natural hosts of the influenza a virus (olsen et al., 2006; webster et al., 1992) , but bats also host influenza a-like viruses (tong et al., 2013; zhu et al., 2013) and the conventional influenza a virus can infect bat cells (zhou et al., 2014) . the fact that they are both capable of flight means that birds and bats have coexisted within a broad range of spatial niches for over 50 myr (veselka et al., 2010) . it is therefore unclear whether coronaviruses and influenza a virus were transmitted from birds to bats or vice versa (brunotte et al., 2016) . it is worth noting that the human influenza a virus is thought to have come from an avian ancestor, with pigs as an immediate host, approximately 100 years ago (gammelin et al., 1990; scholtissek, 1996) . because they are both endothermic vertebrates, birds and bats should be subject to similar selective pressures on flight-related morphological and physiological traits (mcguire and guglielmo, 2009 ). the convergent traits of miniaturized body size, enhanced metabolic rate and antioxidant capacity, prolonged lifespan, a short but efficient digestive tract, and possessing some specific immunological features relative to non-flying mammals are thought to be the result of functional constraints on evolution imposed by the demands of powered flight (thomas and suthers, 1972; norberg, 1990; caviedes-vidal et al., 2007; costantini, 2008; munshi-south and wilkinson, 2010; song et al., 2020; ) . unlike non-flying mammals which tend to increase in size over evolutionary time (cope's rule; laurin, 2004) , the evolutionary trend in birds and bats has been towards miniaturization; the mass of flying birds ranges from 1.5 g to 15 kg, and for bats from 1.5 g to 1.5 kg ( fig. 1 ; norberg, 1990) . in the volant groups, although the j o u r n a l p r e -p r o o f energetic costs (per unit body weight) can vary with the type of flight (e.g., sustained flapping flight, short flight, and gliding flight; guigueno et al., 2019) , in general, the energetic cost (per unit body weight) of flight is approximately comparable in birds and bats (thomas and suthers, 1972; munshi-south and wilkinson, 2010) . compared with non-flying mammals, both birds and bats have significantly higher metabolic demands for volant flight (norberg, 1990; guigueno et al., 2019) . the enhanced metabolic demands for powered flight in birds and bats are thought to have driven the evolution of reduced cell and genome sizes (gregory, 2001; 2002; organ et al., 2007) . for example, bats have the smallest genome size (∼1.6 to 3.54 gb) of all mammals, and their dna loss/gain ratio is ∼4.3-fold greater than that of other mammals (kapusta et al., 2017; teeling et al., 2018) . similarly, birds have the smallest genome size of all vertebrates (tiersch and wachtel, 1991; gregory et al., 2009 ). furthermore, the reduction in dna in both birds and bats has proceeded mostly through the deletion of large segments (>10 kb) events and gene loss (zhang et al., 2014; kapusta et al., 2017) . the acquisition of powered flight and the evolution of smaller genome size in birds and bats is believed to have been achieved by streamlining genomic structure and reducing genomic redundancy (teeling et al., 2018) . in endotherms, body size is positively correlated with life span (speakman, 2005) . however, bats and birds have a substantially longer life span than non-flying mammals of similar body size ( fig. 1 ; austad and fischer, 1991; prinzinger, 1993 , healy et al., 2014 . on average, birds live up to four times longer than similar-sized mammals (lindstedt and calder, 1981; holmes and ottinger, 2003) , and bats live 3.5 times longer than similar-sized, non-flying, placental mammals (austad and fischer, 1991; wilkinson and south, 2002) . the mechanisms underlying the relatively long j o u r n a l p r e -p r o o f life spans of birds and bats are associated with their enhanced capability for preventing oxidative damage to mitochondria and nuclear dna (costantini, 2008; munshi-south and wilkinson, 2010) . because of their longer life spans, widespread distributions and population connectivity, both bats and birds are exposed to a broader range of environments which may increase the probability of these taxa accumulating zoonotic pathogens over time (figuerola and green, 2000; munshi-south and wilkinson, 2010; lucas, 2016) . in both birds and bats, the size and mass of the digestive tract have been minimized to reduce weight during the flight (caviedes-vidal et al., 2007) . however, both birds and bats have more efficient digestive systems than non-flying mammals (caviedes-vidal et al., 2007) . there has also been a striking convergence in the gut microbiomes of birds and bats that tends to be independent of diet or phylogeny (song et al., 2020) . despite their smaller body size, the capacity of bats and most birds to fly allows them to easily escape from unfavorable conditions and predation (healy et al., 2014) . given that the immune system is highly conserved in amniotes, the basic structure and function of responses to viruses are broadly similar in mammals and birds (schat and kaiser, 2014; wigley, 2017) . however, birds and bats as volant groups, some specific immunological features absent in non-flying mammals have enabled them to coexist with viral pathogens (table 1 ; zhang et al., 2013; schat and kaiser, 2014) and act as natural reservoirs for emerging viruses (brook and dobson, 2015; chan et al., 2013) . birds lack lymph nodes but have a specific primary lymphoid organ, the bursa of fabricius. birds have heterophil in their white blood cells that is the functional equivalent of mammalian neutrophil (schat and kaiser, 2014; wigley, 2017) . compared to mammals, birds have different repertoires of j o u r n a l p r e -p r o o f journal pre-proof toll-like receptors (tlrs), inflammatory cytokines and other immune molecules . genes related to innate immunity in birds are initiated immediately during antiviral responses. for example, the duck major histocompatibility complex type i (mhc-i) and interferon-induced protein with 5 tricopeptide repeats (ifit5) are initiated in response to h 5 n 1 virus inoculation (vanderven et al., 2012) . avian immunoglobulin y (igy) is a functional counterpart of mammalian igg and ige, providing defense against infections. however, igy can not activate the complement system and promote hemagglutination inhibition (warr et al., 1995; zhang et al., 2017) . these specific features of the avian immunological system enable birds to be tolerant of many viruses . such notion has been validated by among mammalia groups, bats possess very similar virus-sensing pattern recognition receptors (prrs) and conserved immune systems. however, bats appear to control viral replication by initiating an innate immune response earlier than non-flying mammals brook and dobson, 2015) . there are other critical differences in the adaptive immune response between bats and non-flying mammals. first, bats have a diverse antibody repertoire with relatively lower avidity and a weaker association with antigens . second, bats exhibit a delayed, or differential, peak of primary antibody response and a slow secondary antibody response relative to rodents, primates, and ungulates chan et al., 2013; pavlovich et al., 2018) . in bat genomes, genes in the type i interferon family, the mhc-i, and natural killer-cell receptors, are known to be highly expanded . it has recently been suggested that the low expression j o u r n a l p r e -p r o o f of c-1-tetrahydrofolate synthase in the cells and tissues of bats compared to humans is due to antiviral replication (anderson et al., 2020) . notably, several genes, such as c-rel (a vital gene for maintaining lymphoid cell function) and the ataxia-telangiectasia mutated gene (atm) in the dna damage checkpoint-dna repair pathway, were positively selected in bat ancestors . compared with non-flying mammals, these special immunological features allow bats to mount efficient immune responses against a diverse range of viruses (banerjee et al., 2020) . the ability to fly not only significantly reduces the risk of predation but also significantly increases the ability to colonize new niches and habitats (norberg, 1990) . this enhanced mobility also means that birds and bats transport viruses over hundreds, even thousands of kilometers during migration (hill et al., 2012; prosser et al., 2013) . approximately 20% of birds are migratory (kirby et al., 2008; newton, 2008) . the migrations of billions of birds worldwide also transport viruses to stopover sites, overwintering and breeding habitats (hill et al., 2012) , although migrations can also lower infection risks by escaping from habitats where pathogen stages have accumulated and eliminating infected individuals during strenuous journey (satterfield et al., 2018) . wild birds are associated with the dispersal of covs (georgopoulou and tsiouris, 2008; chamings et al., 2018) , the influenza a virus (hill et al., 2012) , the arboviruses (west nile virus), the usutu virus, the newcastle disease virus, the avian pox virus, and the duck plague virus (georgopoulou and tsiouris, 2008; verhagen et al., 2015; satu et al., 2017) . fewer bats migrate (krauel and mccracken, 2013) but some undertake migrations of over 1,000 km (plowright j o u r n a l p r e -p r o o f allocati et al., 2016) . such migrations allow bat viruses, such as covs, the rabies virus, the hendra, and nipah viruses, to spread over long distances (calisher et al., 2006) . although migratory bird and bat species have different migration patterns, their movements, particularly during intercontinental migration, contribute to viral dissemination and also facilitate viral recombination, mutation and evolution (bahl et al., 2013; hill et al., 2016; plowright et al., 2017; lycett et al., 2019) . given that bats and birds have evolved to compete for spatial niches such as roosting sites they may interact with each other, either directly or indirectly. the bird-bat interactions include co-occurrence in the same nest (e.g., between starling sturnus vulgaris and noctule bats nyctalus noctule (myczko et al., 2016) , the predation of eggs, nestlings, or adult birds by bats (medellín, 1988; ibáñez et al., 2001; perrella et al., 2020) and the predation of bats by birds (fenton and fleming, 1976; camargo and laps, 2016; mikula et al., 2016) . perrella et al. (2020) found about 8% of bird nests were preyed by bats and 2% by reptiles. both bats and birds species richness increases in proximity to the equator due to higher ecological productivity (brown, 2014; de oliveira et al., 2018) . similarly, pathogen diversity is also greater in tropical areas compared to temperate regions, and therefore, pathogen richness in birds and bats could be higher near the equator compared to temperate regions (guernier et al., 2004) . this coexistence could allow the mixing of bats and birds viruses for the generation of recombinant, novel mutant, or reassortment of rna viruses perrella et al., 2020) . furthermore, a large number of birds and bats are gregarious with high population densities. for example, colonies of the mexican free-tailed bat (tadarida brasiliensis mexicana) can contain up to one j o u r n a l p r e -p r o o f million individuals per roost at an average density of about 4,000 bats/m 2 (mccracken and gustin, 1991) . indirect bird-bat interactions include competition for food, and for temporal, and spatial, niches (fenton and fleming, 1976; goldingay, 2009 ). therefore, these convergent features of small body size, high population densities, and spatial mobility, and the bird-bat social interactions provide the opportunity for exchanging viruses, thereby facilitating the emergence of highly pathogenic, new viruses. human activity, such as agriculture and urban development, is causing significant degradation, loss and fragmentation of bird and bat habitat (voigt and kingston, 2016; walsh et al., 2017) . although the majority of the birds and bats are susceptible to anthropogenic change, some flourish in anthropogenic environments, including cities (duchamp and swihart, 2008; johnson and munshi-south, 2017) and are well adapted to urban environments by exhibiting a suite of phenotypic traits in morphology, physiology, and behavior (macgregor-fors et al., 2012; magle et al., 2012; jung and threlfall, 2016; afelt et al., 2018; isaksson, 2018 ) . anthropogenic environments provide some human commensal species with an abundance of food and reduced numbers of parasites and predators, thereby increasing reproductive output and winter survival (minias, 2016) . the often high densities of birds and bats in anthropogenic environments facilitate viral transfer to humans (plowright et al., 2015; afelt et al., 2018) . domestic fowl and livestock are often also at high density in anthropogenic environments, in some countries close to captive wild game. this juxtaposition of domestic and wild animals provides an abundance of immediate hosts for bird and bat-derived viruses, many of which can become pathogenic once transmitted to humans . furthermore, many birds and bats are j o u r n a l p r e -p r o o f caught and transported to markets to be sold for food, traditional medicine, ornamentation, as pets or for sport hunting (mildenstein et al., 2016) . for example, at least 167 species of bats (92 species of large-bodied fruit bats and 75 insectivorous species) are reported to be hunted in africa, asia, central and south america, and across the islands of oceania (mildenstein et al., 2016) . similarly, 4,561 bird species (45.7% of all species) are caught by humans for different purposes (butchart, 2008) . generally, these captured bats and birds are sold and kept in close contact with humans and other taxa in overcrowded and unhygienic wet markets that have become epicenters for the mixing and transmission of viral pathogens aguirre et al., 2020) . the high human population density in cities increases the risk of humans becoming infected with recombinant viruses from intermediate hosts, some of having already caused global pandemics (sehgal, 2010) . the risk of cross-species transmission depends on the spatio-temporal network connecting viral reservoirs to intermediate, and final, hosts (hassell et al., 2017; plowright et al., 2017) . anthropogenic environments can, therefore, be regarded as a viral nexus where bird and bat-derived viruses, a diverse range of potential intermediate hosts, and humans, all exist in close proximity. because their primary and secondary hosts are either mildly symptomatic or asymptomatic, many bird and bat-derived viruses may spread and diversify unnoticed in anthropogenic environments (afelt et al., 2018) . the occasional transmission of viral pathogens from asymptomatic host species to new hosts can lead to either asymptomatic infection, severe disease, or death. birds and bats share a variety of flight-related physiological and ecological traits that predispose them to harbor, disperse, and transmit viruses. special features of their j o u r n a l p r e -p r o o f immune systems enable them to function as asymptomatic carriers of a diverse range of viruses. close interactions between birds and bats in the course of competition for spatial niches, further increases the probability of viral transmission, recombination, and mutation, while the migrations undertaken by many birds and bats disperse viruses over long distances. the ability of some birds and bats to flourish in anthropogenic environments increases the probability of the viral transmission to domestic animals or captive wild game, which facilitates the emergence of novel viruses pathogenic to humans. by bringing together birds, bats, domestic animals, wild game and humans, urban environments provide the ideal conditions for acquiring new viral genes, and harboring high viral burden with strains of higher transmission efficiency, thus facilitating transmission of the viruses to humans. considering that many ongoing bird and bat-derived zoonotic viruses are probably circulating, diversifying, and spreading unnoticed, the risk of such pandemics is ongoing. more transdisciplinary and interdisciplinary investigations are warranted to unravel the complex interactions connecting bat and bird-derived viruses to immediate hosts and to humans and shed light on the origin of the current covid-19 pandemic and reduce the risk of future pandemics. the relationships between body mass and life span in birds (n=1660), bats (n=260), and non-flying mammals (n=2293). birds (p < 0.001) and bats (p < 0.001) have significantly longer lifespans than non-flying mammals when controlled for body mass in a general linear model. black lines around the fitted line are the 95% confidence intervals for each taxon. body mass and lifespan data for each group were taken from myhrvold et al. 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alphacoronavirus and betacoronavirus and avian coronaviruses as the gene source of gammacoronavirus and deltacoronavirus epidemiological characteristics of human-infective rna viruses who characterizes covid-19 as a pandemic comparative analysis of bat genomes provides insight into the evolution of flight and immunity comparative genomics reveals insights into avian genome evolution and adaptation igy: a key isotype in antibody evolution characterization of uncultivable bat influenza virus using a replicative synthetic virus a pneumonia outbreak associated with a new coronavirus of probable bat origin hemagglutinin homologue from h17n10 bat influenza virus exhibits divergent receptor-binding and ph-dependent fusion activities we appreciate the valuable comments from three anonymous reviewers for the improvement of our original manuscript. this study was supported by the national natural science foundation of china (nsfc, 31672292, 31971413) to d.m.l., nsfc (31770445) to y.f.w., the biodiversity investigation, observation, and assessment key: cord-347613-tjeo62dv authors: da silva, priscilla gomes; mesquita, joão rodrigo; de são josé nascimento, maria; ferreira, vanessa andreia martins title: corrigendum to “viral, host and environmental factors that favor anthropozoonotic spillover of coronaviruses: an opinionated review, focusing on sars-cov, mers-cov and sars-cov-2”[sci. total environ. 750 (2021) 141483] date: 2020-09-10 journal: sci total environ doi: 10.1016/j.scitotenv.2020.142123 sha: doc_id: 347613 cord_uid: tjeo62dv nan in the second paragraph of section 2.1, we note that we made a mistake regarding the information given in this part. we confused the information regarding the bat species and the bat-coronavirus strain related sars-cov-2 with the bat species and the bat-coronavirus strain related to sars-cov-1. sars-cov-2 indeed shares 96.2% nucleotide homology with a bat-coronavirus (ratg13) that was isolated from the bat species rhinolophus affinis (cui et al., 2019) , not sars-cov-1. moreover, the hela cells were used in a virus infectivity study with sars-cov-2, not sars-cov-1. in this study, hela cells that expressed or did not express ace2 proteins from humans, chinese horseshoe bats, civets, pigs and mice were used, and it was found that sars-cov-2 is able to use all ace2 proteins (except for mouse ace2) as an entry receptor to enter ace2-expressing cells, but it could not enter cells that did not express ace2, indicating that ace2 is probably the cell receptor through which sars-cov-2 enters cells (zhou et al., 2020) . that being said, the reformulated paragraph with the correct information is as follows: "on later studies, a bat-coronavirus closely-related to sars-cov-1, named sars-related rhinolophus bat cov hku3 (sarsr-rh-batcov hku3), was isolated from chinese horseshoe bats (rhinolophus sinicus) (lau et al., 2005) . this and other bat-coronaviruses share 88-92% nucleotide sequence homology with sars-cov-1 (ye et al., 2020) , leading scientists to believe that sars-cov was transmitted directly to humans from wet market civets, with bats as the main reservoir hosts (cui et al., 2019; hu et al., 2017) ". origin and evolution of pathogenic coronaviruses discovery of a rich gene pool of bat sars-related coronaviruses provides new insights into the origin of sars coronavirus severe acute respiratory syndrome coronavirus-like virus in chinese horseshoe bats zoonotic origins of human coronaviruses a pneumonia outbreak associated with a new coronavirus of probable bat origin the authors regret that the printed version of the above article contained a number of errors. the correct and final version follows. the authors would like to apologise for any inconvenience caused. please note that none of these changes impact on the conclusions made by the paper but are necessary to correct for accuracy. key: cord-282268-f7mbdfr6 authors: cartenì, armando; di francesco, luigi; martino, maria title: how mobility habits influenced the spread of the covid-19 pandemic: results from the italian case study date: 2020-06-24 journal: sci total environ doi: 10.1016/j.scitotenv.2020.140489 sha: doc_id: 282268 cord_uid: f7mbdfr6 abstract starting from december 2019 the world has faced an unprecedented health crisis caused by the new coronavirus (covid-19) due to the sars-cov-2 pathogen. within this topic, the aim of the paper was to quantify the effect of mobility habits in the spread of the coronavirus in italy through a multiple linear regression model. estimation results showed that mobility habits represent one of the variables that explains the number of covid-19 infections jointly with the number of tests/day and some environmental variables (i.e. pm pollution and temperature). nevertheless, a proximity variable to the first outbreak was also significant, meaning that the areas close to the outbreak had a higher risk of contagion, especially in the initial stage of infection (time-decay phenomena). furthermore, the number of daily new cases was related to the trips performed three weeks before. this threshold of 21 days could be considered as a sort of positivity detection time, meaning that the mobility restrictions quarantine commonly set at 14 days, defined only according to incubation-based epidemiological considerations, is underestimated (possible delays between contagion and detection) as a containment policy and may not always contribute to effectively slowing down the spread of virus worldwide. this result is original and, if confirmed in other studies, will lay the groundwork for more effective containment of covid-19 in countries that are still in the health emergency, as well as for possible future returns of the virus. in december 2019, the city of wuhan (hubei, china) experienced a cluster of pneumonia cases that were monitored by the chinese health authorities. this was caused by the new coronavirus sars-cov-2 pathogen, also known as covid-19 (e.g. chinazzi et al., 2020) . the global spread was so rapid that the world health organization (who) on 30 january 2020 officially declared that the covid-19 epidemic was a public health emergency of international concern and later, on 12 march 2020, a global pandemic . in june 2020, who (2020) counted a total of more than 8 million confirmed cases globally and about 450 thousand deaths, reaching all countries worldwide. countries that were initially heavily impacted by this pandemic (e.g. china and south korea) through a massive testing regime as well as strict mobility and travel restrictions were successful in limiting the number of new locally transmitted cases (e.g. kucharski et al., 2020) . in these few months, scientists have made advances in characterising the novel coronavirus and have worked extensively on therapies and vaccines to combat it. furthermore, the medico-scientific community has investigated incubation times for the virus. for example, lauer et al. (2020) estimate that the average incubation time is 5.1 days, while in most cases (97.5%) the symptoms occur within 11.5 days of infection. the above results were used to derive the commonly applied quarantine period of 14 days (e.g. backer et al., 2020) applied in many countries (e.g. china, the usa and major european countries like france, germany, italy, spain and the uk). with respect to the detection of positive cases, previous studies have revealed the presence of a significant fraction of asymptomatic patients infected with the virus surveillances, 2020) , in addition to an unknown percentage of false positive and/or negative of each diagnostic tool among patients with covid-19, which may have slowed down the detection time of new infections. while the scientific community has focused in recent months mainly on health issues to defeat this virus, other key topics addressed in the literature seek to correlate the cases (deaths) of covid-19 to both meteorological (e.g. temperature and relative humidity qi et al., 2020; shi et al., 2020; j o u r n a l p r e -p r o o f tosepu et al., 2020; zhu and xie, 2020 ) and air quality (e.g. pm pollution conticini et al., 2020; pluchino et al., 2020; variables. by contrast the incidence of human mobility on the spread of the covid-19 was not still deeply investigated. indeed, the lockdown of cities and regions together with specific mobility restrictions (e.g. restricted hours and/or areas, specific restrictions for citizen categories) have been common practices performed worldwide to contain and delay the spread of the covid-19 epidemic. for example, according to fang et al. (2020) without the wuhan lockdown, the number of covid-19 cases would have been 64.81% higher in the 347 chinese cities outside hubei province, and 52.64% higher in the 16 other cities within hubei (fang et al., 2020) . many countries are using expedients such as strict mobility, travel restrictions, minimum distance, and quarantine (e.g. muller et al., 2020; wells et al., 2020) the main european countries (such as germany, spain, france and lastly the uk) as well as china and the us, have implemented a 14-day quarantine period based exclusively on medical considerations related to incubation time, that is the time that elapses from initial infection to manifestation of the symptoms (or no symptoms for the asymptomatic patients). this common practice is based on the consideration that, as the incubation of infected suspects takes place within 14 days, the national health system/world health organization will be able to detect a new case in this time interval. by contrast, the hypothesis discussed in this research is that the time period (days) in which a new positive case of coronavirus is identified and certified, which could be called a sort of a positivity detection time, is longer than the incubation time because of possible delays between contagion and detection caused, for example, by the significant percentage of tests that prove false negative to covid-19, or by the fraction of people who, although infected, are asymptomatic and/or initially show only mild symptoms, and therefore do not resort to health care. furthermore, this positivity detection time, as well as the spread of covid-19, is correlated with j o u r n a l p r e -p r o o f mobility habits, in the sense that the number of certified cases of coronavirus in one day is directly related to the number of people who made trips several days before. to the authors' knowledge, this issue has not been investigated elsewhere, and the appropriate definition and estimation of positivity detection time and its correlation with mobility habits (e.g. daily origin-destination trips) could avoid a slowdown in detecting the infection and hence a slowdown in taking restrictive/mitigative measures. starting from these considerations, the aim of the paper was twofold: i) to discuss the spread of coronavirus in italy; ii) to investigate, for the first time in the literature, the incidence of citizen mobility within the spread of the coronavirus (covid-19) pandemic, also quantifying the positivity detection time for the italian case study. to do this, we referred to the mobility habits of the 14-80 year-old population defined in italy as the "active population" (source: istat, 2020), that is the fraction of citizens who are individually able, unless temporary impediments, to carry out activities (e.g. work, leisure, shopping) and that therefore have autonomous mobility habits. the proposed case study is very suitable for the purposes of this research because italy was the first european country to experience mass contagion starting from the first outbreak. furthermore, by may 2020 the spread had almost stopped. it is therefore possible to analyse the huge quantities of detailed contagion data (on a daily basis) and citizen mobility observed at a national scale and for a long time (before, during and after the lockdown), in addition to the effects of specific injunctions adopted by the italian government. to do this, quantitative estimation was also performed from the transportation perspective: the hypothesis according to which the number of certified cases of coronavirus in one day is directly related to the mobility habits made several days before, in addition to other context factors, was investigated. after all, citizen mobility could increase the probability of contagion both directly, for example via trips made by public transport where social distancing cannot be guaranteed, or indirectly (e.g. car trips) because such trips are a measure of the number of activities that a population undertakes in a certain area (trips are made for a purpose), j o u r n a l p r e -p r o o f activities that are generally based on human interactions (e.g. work, leisure, shop, sports, events, cinema), which favor the spread of the virus. estimates were made through a multiple linear regression model linking the number of certified daily cases (day-to-day) to socio-economic indices (e.g. number of residents; population density), environmental variables (e.g. temperature, pm pollution), health care indicators (e.g. number of swabs taken daily) and mobility habits (e.g. number people who performed trips several days before). the paper is organized as follows. section 2 reports methods and materials discussing data collection and model formulation; section 3 describes and discusses the main results. finally, conclusions are reported in section 4. as stated above, one of the aims of the paper was to investigate the incidence of citizen mobility within the spread of the coronavirus (covid-19) pandemic. estimates were made through a regional (zonal) aggregation level following the classification of territorial units for statistics (nuts) of ec (2003) , although some regional-scale variables were estimates starting from a subzonal (provincial) analysis as described below (see the traffic zones considered in figure  the average daily temperature measured by ilmeteo (2020) from january 2020 to may 2020;  the italian mobility rates estimated by isfort (2020) . precisely, the mobility rates considered are those estimated by the official national monitoring observatory "audimob" of isfort (2020) , which periodically carries out continuous sample surveys on the mobility of italians through telephone and computer interviews. through this observatory it was possible to analyse the mobility habits before and during the national lockdown in italy. in all, 2,175 interviews were conducted by isfort (2020) between january and february (before the covid-19 epidemic) and 1,398 interviews immediately after the lockdown (8 march 2020) on a representative population sample between 14 and 80 years old. about 70% of interviews were conducted by the computer assisted telephone interview (cati) system and about 30% by the computer assisted web interviewing (cawi) system. the model estimation was performed through a multiple linear regression model linking the number of certified daily cases (day-to-day) to socio-economic, environmental, health care and mobility traffic count sections j o u r n a l p r e -p r o o f habits variables. this tool is among those most commonly used in econometric analysis (e.g. greene, 2012) . for example, within the transport and/or economic sectors, such methods are commonly used to explain the economic development of an area driven by a transportation infrastructure considered as an input, in addition to other social, economic and territorial variables. with this type of model it is possible to separate the effects of one group of variables with respect to the others (which is the aim of the research), or, in other words, to estimate the effects of a specific variable (e.g. mobility habits), other things being equal. the daily regional new positive cases of covid-19 (delta new certified infections per day) provided by the italian ministry of health (2020), were considered as dependent variables, while different independent variables were tested at regional scale:  health care variables (e.g. number of covid-19 tests per dayrelative to the year 2020);  mobility habits variables (e.g. number of citizens who make at least one trip per day; transport accessibility; distance from the main italian clustersrelative to the year 2020). although several model specifications and independent variables are significant the best model formulation obtained with respect to the validation tests (adj. r-squared and t-value) was: where: mob t,i-x is the average number of 14-80 year-old people have done at least one trip (here defined as "mobility habits") "x" days before the i-th day with respect to the t-th region [100,000*people/day]; this variable measures the circumstance investigated in this research that the number of certified cases of coronavirus in one day is directly related to the mobility habits made "x" days before; temp t,i-x is the average daily temperature observed "x" days before the i-th day with respect to the t-th region [°c] (source: ilmeteo, 2020); constant variable was also estimated, accounting for all the attributes not otherwise included (explained) in the model. as mentioned in the previous section, the first real covid-19 outbreak in italy was in codogno (lombardy). starting from this, the epidemic spread first to neighbouring regions and then increasingly greater distances to the whole of italy. to take into account this proximity effect, a specific variable, ttd t,i , measuring the proximity to the outbreak of codogno was considered in the model. to take this effect into account, we considered that this proximity variable could follow a time-decay principle. the most common non-linear functions proposed for quantifying the time-j o u r n a l p r e -p r o o f decay effect (in the literature well known as the distance-decay principle) are the inverse power and the negative exponential functions (e.g. cheng and bertolini, 2013; martínez and viegas, 2013; hooper, 2015 , kwan, 1998 . starting from such considerations, different time-decay specifications were tested for the proposed ttd t,i variable, resulting that the following inverse power function was the best variable formulation for the case study in question: where: tt t,i is the average weighted (on the population) travel time from the t-th region toward the codogno cluster on the i-th day; ctt t,i,p is the average minimum car 1 travel time from the p-th province toward codogno on the i-th day, estimated on the current national transport network; pop p is the population of the p-th province (source: istat, 2020); day i is the i-th day. to the authors' knowledge, an issue which has not yet been investigated in the literature is the proper definition and estimation of positivity detection time and its correlation with mobility habits (e.g. trips/day). this time period is the average number of days in which the national health system identifies and certifies a new positive case of coronavirus, and which does not coincide (this is the hypothesis supported in this research) with the incubation time that epidemiological studies quantify as being within 14 days (with an average value of 5 days). for this purpose, through the model formulation (1), the number of new covid-19 cases in one day was correlated with the number of people making at least one trip "x" days before, which is to say that the number of today's certified new cases are a function of the mobility habits (and hence of people's interactions) performed some days before. to do this, reference was made to the average number of 14-80 yearold people making at least one trip a day (mobility habits) estimated through the equation: where: mob t,i is the i-th day average number of 14-80 year-old people have done at least one trip in the t-th region; pop t is the 14-80 year-old population (that is, as said, the socio-economic category considered in this study) living in the t-th regional area (source: istat, 2020); admr t is the average daily mobility rate relative to the t-th regional area before the diffusion of covid-19 (source: isfort, 2020); the daily mobility rate was defined as the percentage of residents in the t-th region who during a day make at least one trip, for whatever purpose, with the exception of pedestrian trips shorter than five minutes; %var t,i is the i-th average daily percentage variation of admr t with respect to the pre-covid-19 condition and relative to the t-th regional area. on basis of the italian transport ministry (2020) data, regional weighted ( where: %var t,i,p is the i-th day average percentage variation of the p-th provincial daily mobility rate within the t-th region, with respect to the pre-covid-19 condition; pop p is the population living in the p-th province (source: istat, 2020); %var t,i,p,j is the i-th day average percentage variation of the j-th car traffic trips within the p-th province and the t-th region, with respect to the pre-covid-19 condition (source: italian transport ministry, 2020); f p,j,i is the i-th day average car trips relative to the j-th traffic count section within the p-th province and the t-th region (source: italian transport ministry, 2020). the decision to estimate the trend (day by day) of the daily average percentage variation (%var t,i ) starting from the trend in car trips observed (car traffic counts), instead of considering, for example, the trend in public transport passengers, was made for two reasons: i) public transport (transit) trips decreased over time faster than those observed for private cars due both to the reluctance of users to use such transport services during the pandemic (which do not guarantee adequate social distancing), and to the reduction in the supply of transport services (e.g. reduction in departures/day); whereas public transport trips decreased more rapidly over time, the overall mobility rate, i.e. the average number of people making at least one trip/day (e.g. trips to buy food, pharmaceutical products or other basic necessities), followed a more gradual trend comparable with that observed for car mobility (a consideration also confirmed in terms of model estimation results as described in section 3); ii) moreover, for this transport mode, there were much more widespread data available at a national scale, which was therefore better suited to the purposes of the research. as said, one of the aims of the research was to discuss the spread of coronavirus in italy to investigate the incidence of citizen mobility within the spread of the coronavirus (covid-19) pandemic, the mobility habits trend was preliminary estimated applying the equation (3). as said, through the official national monitoring observatory "audimob" of isfort (2020), were estimated the mobility rates of the italian "active population" (14-80 year-old population) before and during the national lockdown (as imposed by dpcm of 8 march 2020). before the covid-19, within the 14-80 year-old italian population, 38 million residents (80% of the total) made at least one trip per day, while after the lockdown ordinance (dpcm, 8 march 2020) a significant reduction in mobility habits was observed and in few days a reduction to about 18 million people trips/day was observed (-42%). the estimates for the period before covid-19 were used to evaluate the admr t rate, while those made in the first lockdown period (8 march 2020) were used to validate the %var t,i estimates. results in term of daily mobility rates performed by isfort (2020) j o u r n a l p r e -p r o o f significant in regions in central italy (-51%), and less marked in the southern regions and the islands (-36%), while the northern regions fell just below the national average (-42%). as regards the age of the interviewees, starting from the restrictions the collapse in mobility was clear, especially among the over-65s where it fell by three-quarters: fewer than 15% of citizens made at least one trip by private or public transport during the lockdown. the reduction in the mobility rate was also striking among the young and very young, where the majority are schoolchildren or university students. looking at the employment status of the interviewees, the mobility rate during the lockdown was still around 50% among workers (a little higher among employees than the self-employed), who recorded a 35% decrease in trips, just 5-7 points below the general 2 average. on the other hand, the trips of retirees were almost eliminated: their mobility rate fell from 66% pre-covid-19 to 16% under lockdown. there was also a very marked reduction in j o u r n a l p r e -p r o o f student mobility (from 73% to 26%), which was of course massively affected by school closures (dpcm of 9 march 2020). for each of the 20 italian regions, the 14-80 year-old population mobility habits and its day by day evolution before, during and after (beginning of business recovery "phase 2") the covid-19 pandemic in italy was therefore estimated through the equation (3) found.) show that the estimated mobility habits trend is consistent with those of the available databases, in addition to those of the isfort (2020) investigation. as stated above, the main aim of the paper was to investigate the incidence of mobility habits (1), linking the number of certified daily cases (day-to-day) to socio-economic, environmental, health care and mobility zone-specific variables at regional scale. the length of time considered spans the period from the first new cases observed on 21 february 2020 resulting from the outbreak in codogno near milan in lombardy, to 20 april 2020 (60 consecutive days) when the daily infection curve reached its lowest point (figure 3) . furthermore, other time periods were also tested and not reported for brevity so as not to produce significant differences in estimation results. although several model specifications and independent variables are significant, in table 2 with respect to socio-economic variables, italy is characterized by uneven population density within the area of the country and for this reason, although the average regional population density, the model that gave the best results includes a population density variable (popdensity t ) referring to the provincial capital of the region, that is the area where most of the population live. in the italian regions, the average population density is about 183 inhabitants/km 2 , while the corresponding provincial capital population density is about 540 inhabitants/km 2 (+66%). the territorial area where this difference is more evident is the campania region where the province of naples (the highest population density area of the country) with 2,617 inhabitants/km 2 is 84% denser than its region average value (424 inhabitants/km 2 ). this circumstance means that areas with higher population densities have a higher probability of contagion, being (on average) less able to guarantee social distancing (increase in social activities with overcrowding). moreover, more than 19 million inhabitants live in these provincial capitals of the region. (table 2) , explains the circumstance that, all else being equal, the more tests are conducted, the greater is the probability of finding positive cases (especially with respect to the asymptomatic population). as mentioned, the first real covid-19 outbreak in italy was in codogno (lombardy). starting from this, the epidemic spread first to neighbouring regions and then increasingly greater distances to the whole of italy. to take into account that the areas close to codogno have greater daily exchange trips with the outbreak area, and therefore a greater probability of contagion, a specific variable (ttd t,i ) measuring the proximity to the outbreak of codogno was considered in the model. moreover, with the passing of the days this proximity effect from the initial outbreak (trips from codogno and lombardy) decreased, resulting in new contagion produced by the local mobility of residents in the region. to take this effect into account, we considered that this proximity variable could follow the time-decay principle described by the equation (2). through this variable j o u r n a l p r e -p r o o f formulation the proximity effect was greatest within the first days and then "decayed" in its incidence with the passing of the time. mobility habits were the variable (mob t,i-x ) that best explained the number of covid-19 infections (in term of "weight" with respect to the standardized coefficients estimated and reported in table 2 ). this variable measures the circumstance investigated in this research that the number of certified cases of coronavirus in one day is directly related to the mobility habits made "x" days before. to estimate the most representative number of "days before" that influence the new cases in a day, many thresholds were tested in terms of model validation tests, obtaining that trips 21 days before was the best variable to reproduce the data observed. this result is also qualitatively observable from figure 5 through which it may be seen that the daily mobility habits shifted 21 days ahead (left axis of figure 5 ) closely reproduce the observed trend of new daily cases of covid-19 (right axis of figure 5 ). furthermore, among the environmental measures, a particulate matter pollutant variable (pm t ) was significant, measuring the number of days in 2019 in which the national pm 10 daily limit set at 50 µg/m 3 was exceeded. this measure on a regional scale was obtained as a weighted (on the population) average of the corresponding variables referring to provinces within each region, meaning that areas with higher population and with lower air quality have have a higher probability of contagion. overall, the data analysis shows how the areas of the country with the highest pm pollution are those of northern italy (e.g. province of milan in lombardy and turin in piemonte), where are mainly located the industrial areas and/or most of the population live, according to with the circumstance that pms are mainly generated by industries, heating (e.g. home, office) and transport sector (e.g. mobility habits). the opposite occurs for areas in the south, characterized by an economy mainly based on tourism and agriculture. this variable explains, as observed in other case studies, the (positive) correlation between the number of cases per day and the average pollution in the area. with respect to air quality impacts upon the spread of covid-19, some recent research has shown that people living with long-term exposure to air pollution are more likely to j o u r n a l p r e -p r o o f become infected by coronavirus. for example, conticini et al. (2020) conclude that a prolonged exposure to air pollution may partly explain a higher presence of viral agents such as sars-cov-2. finally, temperature (temp t,i-x ) was also significant and represents the third variable in "weight" with respect to the standardized coefficients estimated ( j o u r n a l p r e -p r o o f relative humidity positively influence the spread of covid-19 (e.g. qi et al., 2020; shi et al., 2020; tosepu et al., 2020; zhu and xie, 2020) . for example, in hubei (china) qi et al. (2020) observed that every 1 °c increase in the average temperature with relative humidity in the range from 67% to 85% led to a 36% to 57% reduction in confirmed covid-19 cases. in addition, the authors also concluded that every 1% increase in relative humidity led to an 11% to 22% reduction in daily confirmed cases with average temperatures in the range from 5.0 °c to 8.2 °c. the research discussed in this paper concerns the topics of both the "atmosphere" (air quality and temperature impacts) and the "anthroposphere", in the sense of the earth's research area dealing with the part of the environment that is made or modified to satisfy human activities and habits, where transportation system and the corresponding people mobility trips cover a central role. precisely, the aim of the paper was to investigate the incidence of citizens' mobility habits within the spread of the coronavirus (covid-19) pandemic for the italian case study. the conjecture that the number of new certified cases of coronavirus in one day is directly related to the number of trips made several days before, in addition to environmental and other context factors, was investigated. another issue discussed in this paper and unexplored in the literature is the appropriate definition and estimation of the positivity detection time and its correlation with mobility habits. the thesis was that this time period generally exceeds the incubation time due to many external factors such as false negative test results to covid-19 or people who, albeit infected, are asymptomatic and/or initially show only mild symptoms, and therefore do not resort to health care. to pursue the research aims, quantitative estimation was made through a multiple linear regression model. estimation results showed that mobility habits represent the variable that mainly covid-19 mobility trends (driving data) regionale per la protezione ambientale incubation period of 2019 novel coronavirus (2019-ncov) infections among 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relationship between particulate matter (pm) pollution and covid-19 infection spread in italy a novel methodology for epidemic risk assessment: the case of covid-19 outbreak in italy covid-19 transmission in mainland china is associated with temperature and humidity: a time-series analysis position paper: relazione circa l'effetto dell'inquinamento da particolato atmosferico e la diffusione di virus nella popolazione impact of temperature on the dynamics of the covid-19 outbreak in china the epidemiological characteristics of an outbreak of 2019 novel coronavirus diseases (covid-19)-china correlation between weather and covid-19 pandemic in jakarta, indonesia. science of the total environment 138436 impact of international travel and border control measures on the global spread of the novel 2019 coronavirus outbreak world health organization exposure to air pollution and covid-19 mortality in the united states effects of temperature and humidity on the daily new cases and new deaths of covid-19 in 166 countries association between ambient temperature and covid-19 infection in 122 cities from china. science of the total environment 138201 the research was carried out as part of the activities of the transportation system laboratory of the university of campania "luigi vanvitelli," italy. the research was also carried out within the activities of funding program valere: vanvitelli per la ricerca; send research project, university of campania "luigi vanvitelli", italy. key: cord-325479-2r4oomdp authors: torii, shotaro; furumai, hiroaki; katayama, hiroyuki title: applicability of polyethylene glycol precipitation followed by acid guanidinium thiocyanate-phenol-chloroform extraction for the detection of sars-cov-2 rna from municipal wastewater date: 2020-10-17 journal: sci total environ doi: 10.1016/j.scitotenv.2020.143067 sha: doc_id: 325479 cord_uid: 2r4oomdp the primary concentration and molecular process are critical to implement wastewater-based epidemiology for severe acute respiratory syndrome coronavirus 2 (sars-cov-2). however, the previously developed methods were optimized for nonenveloped viruses. few studies evaluated if the methods are applicable to the efficient recovery of enveloped viruses from various types of raw sewage. this study aims (1) to compare the whole process recovery of pseudomonas phage φ6, a surrogate for enveloped viruses, among combinations of primary concentration [ultrafiltration (uf), electronegative membrane vortex (emv), and polyethylene glycol precipitation (peg)] and rna extraction methods (spin column-based method using qiaamp viral rna mini kit and acid guanidinium thiocyanate–phenol–chloroform extraction using trizol reagent) for three types of raw sewage and (2) to test the applicability of the method providing the highest φ6 recovery to the detection of sars-cov-2 rna. among the tested combinations, peg+trizol provided the highest φ6 recovery ratio of 29.8% to 49.8% (geometric mean). uf+qiaamp viral rna mini kit provided the second highest φ6 recovery of 6.4% to 35.8%. the comparable φ6 recovery was observed for uf+trizol (13.8 – 30.0 %). peg+qiaamp viral rna mini kit provided only 1.4% to 3.0% of φ6 recovery, while coliphage ms2, a surrogate for nonenveloped viruses, was recovered comparably with peg+trizol. this indicated that the nonenveloped surrogate (ms2) did not necessarily validate the efficient recovery for enveloped viruses. emv+qiaamp viral rna mini kit provided significantly different φ6 recovery (1.6 – 21 %) among the types of raw sewage. then, the applicability of modified peg+trizol was examined for the raw sewage collected in tokyo, japan. of the 12 grab samples, 4 were positive for sars-cov-2 cdc n1 and n3 assay. consequently, peg+trizol provided the highest φ6 recovery and allowed for the detection of sars-cov-2 rna from raw sewage. the ongoing disease outbreaks caused by severe acute respiratory syndrome coronavirus 2 (sars-cov-2) have tremendous damage to global health and world economics. the main transmission of the respiratory viruses is via close contact with respiratory secretions expelled by an infected person (world health organization, 2020) . although the sars-cov-2 predominantly caused respiratory diseases, its genome was detected not only from the respiratory tract but also from stools (wölfel et al., 2020) . therefore, the detection of human pathogenic viruses from wastewater suggests the presence of infected people in the catchment area. this approach has been expected to be feasible to evaluate the eradication of poliovirus in the community (lodder et al., 2012) and the prevalence of norovirus, (kazama et al., 2016) known as wastewater-based epidemiology (wbe). currently, the monitoring of the sars-cov-2 concentration is expected to be a powerful tool for the early detection of outbreaks and the prediction of prevalence in the catchment murakami et al., 2020; rusiñol et al., 2020) . recent studies have detected sars-cov-2 in the raw sewage or secondary effluent by applying primary concentration methods followed by rna extraction and reverse transcription (rt)-quantitative polymerase chain reaction (qpcr) (ahmed et al., 2020a; haramoto et al., 2020; medema et al., 2020; randazzo et al., 2020; sherchan et al., 2020) . the adopted primary concentration methods included polyethylene glycol precipitation (peg) wu et al., 2020) , ultrafiltration (uf) (medema et al., 2020; sherchan et al., 2020) , electronegative membrane vortex (emv) (haramoto et al., 2020) , and adsorption-extraction methods (ahmed et al., 2020a) . considering that the constraints on financial capacity, laboratory equipment, and labor resources differ among the implementers of wbe, it is preferable to validate a variety of primary concentration methods. the conventional primary concentration has been optimized to detect waterborne enteric viruses, which are mostly nonenveloped. enveloped viruses possess a lipid membrane at the outermost layer, thus exhibiting different physical properties (i.e., more hydrophobic) from nonenveloped viruses (lytle and routson, 1995) . few studies have evaluated the applicability to the recovery of enveloped viruses from water. a previous study adopted the filter-lysis method and struggled with efficient recovery of enveloped viruses: poliovirus (nonenveloped) for 45% versus koi herpes virus (enveloped) for 3.6% (haramoto et al., 2009) . thus, the conventional process should be 4 optimized for the efficient recovery of enveloped viruses. a recent study compared a variety of concentration methods for the recovery of murine hepatitis virus (mhv), a surrogate of sars-cov-2, from raw sewage (ahmed et al., 2020b) . they reported the highest mhv recovery rate for the adsorptionextraction methods with mgcl 2 pretreatment (65.7%). they also reported a 56.0% recovery for the uf using amicon ultra-15 centrifugal filter device. although these methods achieved a high recovery efficiency enough for detecting enveloped viruses in the raw sewage, expensive equipment (e.g., bead-beating system) and costly consumable supplies (e.g., centrifugal device) are needed for sample processing. moreover, previous studies did not investigate how the water quality and the type of the molecular process affect the whole recovery efficiency of enveloped viruses. (casanova and weaver, 2015a; ye et al., 2016) . a recent study adopted it as a molecular process control (mpc) (sherchan et al., 2020) . moreover, φ6 and its host, pseudomonas syringae, are not pathogenic to humans and require minimal containment for laboratory facilities (i.e., bsl1) (casanova and weaver, 2015b) . finally, φ6 can be propagated within 1 day with high titers (up to 10 10 pfu/ml); thus, it can be practically adoptable as a surrogate for the human pathogenic enveloped viruses. this study aims (1) to compare the combination of primary concentration (uf, emv, and peg) and rna extraction (qiaamp viral rna mini kit and trizol) for the whole process recovery of nonenveloped and enveloped virus surrogates and (2) to test the applicability of the method providing the highest φ6 recovery to detect sars-cov-2 2.1. preparation of coliphage ms2, pseudomonas phage φ6, and murine norovirus bacteriophage ms2 (nbrc 102619, national institute of technology and evaluation (nite), tokyo, japan) was propagated as described elsewhere (torii et al., 2019) . pseudomonas phage φ6 (nbrc 105899, nite) was propagated using pseudomonas syringae (nbrc14084, nite) as a host strain. briefly, 3 ml of phosphate buffer (pb) (10 mm, ph 7.0) was added on the soft lb plates (0.7% agar) semiconfluent with φ6 plaques (approximately 1000 plaques/plates) and incubated at room temperature for 5 h. the suspension and soft agar were then removed from the plate and transferred to a centrifuge tube. next, 10 ml of recovered viruses were clarified by centrifugation at 3500 g for 15 min and filtered through a cellulose acetate filter (0.2 μm, dismic-25cs, advantec, tokyo, japan). mnv s7-pp3 strain was propagated using raw.264.7 cell as a host (kitajima et al., 2008) . the concentrations of propagated stocks were approximately 10 11 pfu/ml, 5 × 10 9 pfu/ml, and 10 11 copies/ml for ms2, φ6, and mnv, respectively. the propagated stocks were stored at 4°c. before the primary concentration, the ms2 and φ6 stocks were diluted by 1000-fold and 100-fold, respectively, to prepare the diluted stocks. three raw sewages were used for the comparison: raw sewage a was a grab sample collected from the influent of a wastewater treatment plant (wwtp) located in niigata prefecture, raw sewage b was a composite sample collected from the influent of a wwtp located in kanagawa prefecture, and raw sewage c was a composite sample collected from the influent of wwtp located in tokyo metropolis. the physicochemical water qualities of each raw sewage is shown in table 1 . the composite samples (raw sewages b and c) were generated as described in the supporting information (si). all the samples were stored at −20°c until the primary concentration. three primary concentration methods were tested: ultrafiltration after pre-centrifugation (uf), electronegative membrane vortex (emv), and polyethylene glycol precipitation after pre-centrifugation (peg). a 50-ml (for uf and emv) or 40-ml (for peg) of raw sewage was inoculated with 1/1000 amount of diluted stocks of ms2 and φ6 (i.e., 50 μl for uf and emv, 40 μl for peg) and incubated at 4 °c for 1.5 h -2.5 h. for a single day, ranging from 4 to 14 of aliquots of spiked raw sewage were prepared. as a control, 50 ml of milliq water spiked with 50 μl of diluted stocks of ms2 and φ6 were prepared in duplicate every single day. the incubation of raw sewage for 1.5-2.5 h is expected to reach the liquidsolid partitioning of spiked viruses at equilibrium, which allows for mimicking the actual partitioning conditions of viruses in raw sewage (ye et al., 2016) . the procedure of each primary concentration method was conducted four times per type of raw sewage (i.e., raw sewages a, b, and c). a 50-ml aliquot of raw sewage was centrifuged at 3500 g for 15 min to remove large particles. the supernatant was further centrifuged at 3500 g for 20 min to filter through the centricon plus-70 centrifugal device with a molecular cutoff of 30 kda (merck millipore, billerica, ma, usa). the final volume of the concentrates ranged from 0.17 to 0.21 ml. thus, the concentration factor in uf ranged from 237-to 294-fold. emv: emv was performed based on a previous study (haramoto et al., 2020) . a 50 ml aliquot of raw sewage inoculated with 500 μl of 2.5 m mgcl 2 was filtered through a mixed cellulose-ester membrane (hawp04700, pore size, 0.45 μm; diameter, 47 mm; merck millipore) by vacuum aspiration. subsequently, 10 ml of elution buffer, containing 0.2 g/l of sodium polyphosphate, 0.3 g/l of ethylenediaminetetraacetic acid trisodium salt trihydrate (c 10 h 13 n 2 o 8 na 3 3h 2 o), and 0.1 ml/l of tween 80, was added to the filtered membrane in a 50-ml centrifuge tube. elution was performed by vigorous vortexing using a football-shaped stirring bar. this step was repeated using a 5 ml of elution buffer after transferring a 10-ml of eluent to a different centrifuge tube. the resultant eluent (approximately 15 ml) was centrifuged at 2,000 g for 10 min at 4°c. the supernatant was filtered through a cellulose acetate filter (0.2 μm, dismic-25cs, advantec, tokyo, japan). the filtrate was centrifuged at 1,500 g for 10 min twice followed by 5 min in a centriprep ym-50 uf device (merck millipore) for concentration. the final volume of the concentrate ranged from 0.64 to 4.38 ml. thus, the concentration factor in emv ranged from 11.4-to 78.1-fold. a 40-ml aliquot of raw sewage was centrifuged at 3,500 g for 5 min to remove large particles. the supernatant was supplemented with 4 g of peg8000 (sigma-aldrich , mo, usa) and 2.35 g of nacl (wako, osaka, japan) to the final concentrations of 10% (w/v) and 1.0 m, respectively, and incubated at 4 °c overnight in a shaker . thereafter, the mixture was centrifuged at 10,000 g for 30 min. the pellet was resuspended with 10 mm pb. the final volume of the concentrate ranged from 0.42 to 0.8 ml. thus, the concentration factor in peg ranged from 50-to 95-fold. after each primary concentration, the resultant concentrate and control samples were stored at -20 °c until the molecular process. freeze-thawing of primary concentrates was limited up to once. for the section 3.1, two types of viral rna extraction methods were tested: spin column-based nucleic acid purification using qiaamp viral rna mini kit (qiagen, hilden, germany) and acid guanidinium thiocyanate-phenol-chloroform extraction (chomczynski and sacchi, 1987) using trizol reagent (thermo fisher scientific, ma, usa). first, a 140-μl aliquot of the virus concentrate was seeded with 5 μl of nonenveloped mnv (corresponding to 4.32 ± 0.19 copies) as an mpc. as a control, a 140-μl aliquot of milliq spiked with the same amount of mnv was prepared in duplicate. the comparison of mnv concentrations between concentrated samples and control samples allows to evaluate the molecular process recovery ratio as described in 2.6. the spiked concentrates were processed following the manufacturer's instruction to obtain an rna extract with a final volume of 60 μl. thus, the concentration factor in the rna extraction process was 2.3-fold. the extracted rna was subjected to the rt process within the same day. j o u r n a l p r e -p r o o f 2.5. before the rt-qpcr step, the rna was incubated at 95°c for 5 min followed by 4°c for 1 min (mijatovic-rustempasic et al., 2013) to denature dsrna of φ6. a preliminary investigation indicates that the heating step did not significantly affect the quantification results of ms2 suspended in milliq water (data not indicated). first, 20 μl of the rna extract was subjected to the rt step. a high-capacity cdna rt kit (thermo fisher scientific) was used to obtain cdna with a final volume of 40 μl. the concentration factor in rt process was 0.5-fold. the obtained cdna was stored at 4°c and subjected to qpcr within 2 days. then, taqman™ gene expression master mix was used to perform qpcr following the manufacturer's protocol. a 5 μl of the cdna was mixed with 15 μl of the reaction mixture containing 10 μl of the master mix, virus-specific forward primers and reverse primers, and taqman probe. the sequence of primers and the probe (gendron et al., 2010; kitajima et al., 2008; wolf et al., 2010) were described in table s1 . the conditions of thermal cycling were as follows: 50°c for 2 min and 95°c for 10 min, followed by 45 cycles of 94°c for 15 sec and 60°c for 60 sec (for quantification of ms2 and φ6), or followed by 94°c for 15 sec and 56°c for 60 sec (for mnv quantification). a standard curve generated from tenfold serial dilution of standard dna (plasmid dna or oligo dna) containing the target sequence (10 5 -10 1 or 5 × 10 5 to 5 × 10 0 copies/reaction) was used to determine the number of viral genome copies per qpcr reaction. a negative control was included in all qpcr assays. the amplification efficiencies for ms2, φ6, and mnv averaged 93.5%, 97.2%, and 99.8%, respectively. the coefficient of determination (r 2 ) for ms2, φ6, and mnv assay averaged 0.998, 0.999, and 0.999. to test the impact of rt-qpcr kit on the whole or molecular process recovery (see section 3.3), the rt-qpcr steps described earlier (referred to method 1) was compared with one-step rt-qpcr using quantitect probe rt-pcr kit (qiagen) (method 2). method 2 was performed following the manufacturer's instruction. a 5 μl of the rna extract was mixed with 15 μl of the reaction mixture, containing 10 μl of master mix (qiagen), 0.2 μl of quantitect rt mix, virus-specific forward primers and reverse primers, and taqman probe. the conditions of thermal cycling were as follows: 50°c for 30 min and 95°c for 15 min, followed by 45 cycles of 94°c for 15 sec and 60°c for 60 sec (for quantification of ms2 and φ6), or followed by 94°c for 15 sec and 56°c for 60 sec (for mnv quantification). journal pre-proof 2.6. calculation of whole process recovery and molecular process recovery the whole process recovery ratio (w), molecular process recovery ratio (m), and sample limit of detection (slod) (copies/ml) were presented as eq. (1), (2), and (3), respectively. the cdna concentration of ms2 and φ6 in control were measured by qiaamp viral rna mini kit, followed by rt-qpcr and were 5.55 ± 0.31 log and 5.61 ± 0.27 log copies/ml, respectively. the comparison of virus concentrations between concentrated samples and control allows for the evaluation of the whole process recovery ratio as described below. where c obs_wpc indicates the cdna concentration of wpc in concentrated samples (copies/ml), c ini_wpc indicates the cdna concentration of wpc in the control sample (copies/ml), x the concentration factor during the whole process (primary concentration, rna extraction, and rt), c obs_mpc indicates the cdna concentration of mpc in concentrated samples (copies/ml), c ini_mpc indicates the cdna concentration of mpc in the control sample (copies/ml) and alod indicates the assay limit of detection defined as the minimum copy number with a 95% probability detection (copies/ml). the concentrated samples and corresponding control samples were always subjected to rt-qpcr simultaneously to avoid the potential bias on the whole and molecular process recovery ratio. furthermore, the number of freeze-thawing (i.e., none or once) was made consistent between concentrated and control samples. (ahmed et al., 2020b) . thereafter, the rna was precipitated and filtered through a silica-based column followed by washing and elution, as described in the manufacturer's instructions, without dnase treatment. the final volume of eluted rna was 60 μl. thus, the concentration factor of this process was 4.2-fold. the applicability of peg + trizol + rneasy powermicrobiome kit was confirmed by raw sewages a, b, and c. the whole process recovery of φ6 was evaluated in duplicate for each raw sewage. the rt-qpcr process follows method 1 (two-step rt-qpcr using high-capacity cdna reverse transcription kit and taqman™ gene expression master mix). a 400-500 ml of grab sample of raw sewage was collected on june 30, july 6, 16, 22, and 29; and august 5, 2020 at municipal wwtps d and e, located in tokyo metropolis, japan. the samples were stored at −20°c until processing. a total of 12 samples were further processed as below. a 40-ml aliquot of each raw sewage was concentrated by peg. then, a 250 μl of the concentrate was processed by trizol + rneasy powermicrobiome kit to obtain a 60 μl of rna extract. then, 35 μl of rna extract was subjected to rt to obtain 70 μl of cdna as a final volume. four published assays (niid_2019-ncov_n, cdc n1, cdc n2, and cdc n3 assays(centers for disease control and prevention, 2020; shirato et al., 2020)) were performed to detect the sars-cov-2 rna from raw sewage. we also tested the whole process recovery ratio of φ6. 3.1. whole process recovery ratio of ms2 and φ6 the comparisons among the combination of primary concentration and rna extraction methods were performed as shown in figure 1 . for each type of raw sewage, three primary concentration methods were performed four times. each primary concentrate was then subjected to two types of rna extraction methods. note that uf concentration was performed separately to conduct both rna extraction methods; the limited volume of single uf concentrate (i.e., 170 -210 μl) did not allow for conducting both methods, which requires a total of 280 μl of concentrate. uf+trizol was not performed for raw sewage a due to the limited amount of the sample. the whole process recovery ratio of ms2 and φ6 by each method (primary concentration + rna extraction) as a function of the type of raw sewage is shown in figure 2 . the mean log whole process recovery ratio along with its corresponding standard deviation (sd) is shown in table 2 mini kit in raw sewage a was due to the outlier (φ6 recovery of −2.06 log) (see figure 2 ). interestingly, the use of trizol did not significantly improved the whole process φ6 recovery of uf, contrary to the results observed in peg. this was possibly because the positive effect of using trizol for φ6 extraction was offset by the inhibition during molecular process. the mnv recovery was lower in uf+trizol than uf+qiaamp viral rna mini kit by 0.37 to 1.09 log (see figure s1 and table s2 ). accordingly, the ms2 recovery was lower in trizol than qiaamp viral rna mini kit, as shown in figure 2 . thus, the both effects, higher extraction efficiency but stronger inhibition, leads to the comparable whole φ6 recovery ratio of uf + trizol to uf + qiaamp viral rna mini kit. emv + qiaamp viral rna mini kit has been originally developed to concentrate viruses and protozoa simultaneously (haramoto et al., 2012) . this method provided favorable φ6 recovery ratio for raw sewage a. however, the φ6 recovery was decreased to −1.01 ± 0.42 (9.7%) for b and −1.80 ± 0.22 (1.6%) for c. interestingly, the result of anova suggested that the water matrix significantly affected the recovery ratio of ms2 (p < 0.05) and φ6 (p < 0.01). the lower recovery in raw sewages b and c might be due to the lower elution efficiency, caused by the higher turbidity and organic concentration in wastewater matrix (higher tss and uv 260 ) (see table 1 )). the turbid water matrix promoted membrane fouling, which prevented the elution buffer from contacting with the surface of the membrane, where viruses attached, during the vigorous vortex. in the filtration of raw sewage supplemented with mg 2+ ions through negatively charged membranes, not only viruses but also various components of feed water (e.g., humic acids, silica, and clays) are co-deposited on the membrane surface (hata et al., 2011) . previous research also reported the negative impact of membrane fouling on the elution efficiency (shi et al., 2016) . in fact, the original work developing emv + qiaamp viral rna mini kit validated the whole process recovery ratio of nonenveloped coliphage qβ and poliovirus for river water and tap water, but did not test for raw sewage (haramoto et al., 2012) . a recent work detected sars-cov-2 rna from the secondary effluent and did not detect from the raw sewage (haramoto et al., 2020) . these results suggest that emv + qiaamp viral rna mini kit can be applied only to concentrate enveloped viruses for relatively clean water samples (e.g., secondary effluent or raw sewage containing low tss and uv 260 , such as a) and not universally recommended for raw sewage. emv + trizol provided a lower recovery of both ms2 and φ6 (<5%). the comparison between the rna extraction kits in emv was discussed in si. j o u r n a l p r e -p r o o f achievable slod in each combination of primary concentration and rna extraction method was shown in figure 3 . in this study, we adopted the observed values of concentration factor and whole process recovery ratio and assumed alod to be the most sensitive value theoretically possible, namely, 3 copies/5 μl (bustin et al., 2009) . peg + trizol achieved the lowest slod of φ6 for a [1.31 ± 0.12 log copies/ml (20 copies/ml)] and the third lowest slod of φ6 for b and c [1.33 ± 0.28 log copies/ml (21 copies/ml) and 1.07 ± 0.31 copies/ml ( achievable slod depends on the concentration factor, whole process recovery ratio, and alod. thus, each method still can be potentially improved by higher concentration factors (i.e., increased initial sample volume or reduced concentrate volume). for example, previous studies adopted higher initial volume for primary concentration: up to 200 ml for uf concentration (medema et al., 2020) , up to 200 ml for emv (haramoto et al., 2020) , and up to 250 ml for peg (la rosa et al., 2020) . it should be noted that the concentration factor and whole/molecular process recovery are generally trade-offs; highly concentrated samples contain a higher amount of inhibitor, reducing the efficiency of rt and qpcr process. hence, the removal of inhibitory substances during rna extraction, optimized dilution of primary concentrate, and selection of reverse transcriptase qpcr master mix resistant to inhibition will be required if the primary concentration is performed with a higher concentration factor. j o u r n a l p r e -p r o o f with respect to the type of raw sewage. black color indicates ms2 recovery, whereas red color indicates φ6 recovery. circles with error bars indicate mean values and standard deviation. smaller square is jittered plots, indicating each data of slod. note that the slod by uf+trizol (raw sewage a) was not available. impact of rt-qpcr kit on the whole process recovery ratio the impact of the rt-qpcr kit selection on the whole process recovery was evaluated for three primary concentration methods using raw sewage a as a test sample j o u r n a l p r e -p r o o f and qiaamp viral rna mini kit as an rna extraction kit ( figure s2 ). the stored rna extract of qiaamp viral rna mini kit was subjected to rt-qpcr process of method 2. the rt-qpcr recovery was compared between the two types of methods. the whole process ms2 and φ6 recovery is presented in figure s3 . method 2 provided ms2 recovery of −2.53 ± 0.32 log, −3.74 ± 0.72 log, and −1.22 ± 0.11 log and φ6 recovery of −3.38 ± 0.11 log, −2.67 ± 0.49 log, and −2.26 ± 0.16 log for uf, emv, and peg, respectively. for all the primary concentration methods, the whole process ms2 and φ6 recovery by method 2 were significantly lower than method 1 (paired t-test, p < 0.05). moreover, the molecular process mnv recovery was −2.17 ± 0.54 log, −2.42 ± 0.36 log, and −0.59 ± 0.22 log for uf, emv, and peg, respectively ( figure s4 ). they were significantly lower in method 2 than method 1 (paired t-test, p < 0.05). these results indicate that method 2 was not effective for the quantification of both ms2 and φ6 from raw sewage processed by three types of primary concentration methods. the observed difference was due to the inhibition during the rt-qpcr process, as revealed by the molecular process recovery of mnv. both methods are different in terms of master mix composition, the type of primer (method 1, random primer; method 2, specific primer), and the inclusion of rnase inhibitor (method 1, included; method 2, not included). moreover, in method 1, 0.5-fold rna extract was subjected to qpcr [due to the dilution in the rt process (figure 1 )], potentially contributing to the mitigation of pcr inhibition. a previous study reported that qiagen quantitect probe rt-pcr kit was susceptible to organic pcr inhibitor, such as lactoferrin, than other rt kits (stephens et al., 2010) . these results indicate that the rt-qpcr kit affects the quantification of the virus concentrate for all the methods in raw sewage. thus, the rt-qpcr steps should also be optimized for efficient recovery. detection of sars-cov-2 rna from raw sewage the applicability of peg + trizol + rneasy powermicrobiome kit was investigated for the detection of sars-cov-2 rna from raw sewage. first, the peg + trizol + rneasy powermicrobiome kit provided the φ6 recovery ratio of −0.10 ± 0.10 (79%), −0.56 ± 0.10 (27.3%), and −0.75 ± 0.03 (17.8%) for a, b, and c, respectively, which were comparable with the peg + trizol method. the slod was 0.72 ± 0.12 log copies/ml (5.3 copies/ml), 1.18 ± 0.09 log copies/ml (15.1 copies/ml), and 1.34 ± 0.03 log copies/ml (11.8 copies/ml). thus, the slod can be slightly lowered than peg + trizol. the peg + trizol + rneasy powermicrobiome kit was then applied to the detection of sars-cov-2 rna from the raw sewage collected from tokyo metropolis. the results of four sars-cov-2 qpcr assays along with corresponding values of whole process recovery of φ6 were reported (table 3 ). the whole process recovery of φ6 averaged −0.49 ± 0.32 log (33%). the sample limit of quantification (sloq), given by aloq (5 copies/5 μl) divided by the concentration factor and by φ6 whole process recovery ratio, averaged 4.29 ± 0.32 log copies/l (2.0 × 10 4 copies/l). of the 12 grab table s3 . the discussion between confirmed cases and the sars-cov-2 rna is described in si. overall, the peg + trizol was successfully applied to the detection of sars-cov-2 rna from wastewater with a favorable whole process recovery ratio of φ6. figure 2 ). this indicates the danger of reliance on nonenveloped surrogates. in addition, not only primary concentration but also the molecular process (rna extraction and rt-qpcr) should be optimized. our study suggested that effective primary concentration is just the first step. an appropriate molecular process (i.e., rna extraction and rt-qpcr) is required, as was proven by the comparison between peg + qiaamp viral rna mini kit and peg + trizol (see figure 2 ) and by the comparison between rt-qpcr methods ( figure s3 ). finally, the universal applicability of primary concentration methods cannot be judged from a single type of wastewater matrix. the results of the whole process recovery by emv indicate that the efficiency of primary concentration differs depending on the wastewater matrix (see figure 2 ). it may be necessary to validate the quantification process in house by adopting the appropriate wpc because the rna extraction kits, rt-qpcr kits, and the water quality differ in every laboratory. a further consideration is required for adopting φ6 as a process control to validate the quantification results of enveloped viruses. the possible rationales and limitations of adopting φ6 are presented in table 4 . under the limited bsl facility (e.g., wwtp), the choice of φ6 will be practically best considering the broad and commercial availability compared with other enveloped bacteriophages. however, φ6 has double-stranded rna and an envelope derived from pseudomonas syringae, which might not fully reflect the properties of viruses in interest (e.g., sars-cov-2 and influenza). thus, further research should confirm the comparability of the fate of φ6 during primary concentration and molecular process with the sars-cov-2, coronavirus surrogates (mhv, porcine epidemic diarrhea virus (randazzo et al., 2020) , bovine attenuated coronavirus (gonzalez et al., 2020) ), and ideally indigenous sars-cov-2 in wastewater. to the best of our knowledge, no studies have evaluated the comparability of overall j o u r n a l p r e -p r o o f recovery efficiency of surrogate viruses. de facto standardization of these surrogate viruses should be avoided before the comparison conducted in the future. ･no proof of comparability to sars-cov-2 the structural difference between φ6 and sars-cov-2 and between freshly prepared enveloped viruses and indigenous sars-cov-2 might affect the recovery efficiency.  polyethylene glycol precipitation (peg) followed by acid guanidinium thiocyanate-phenol-chloroform extraction (peg + trizol) provided the highest whole process recovery ratio of pseudomonas phage φ6 ranged from -0.53 to -0.30 log (29.8 -49.8%) in three types of raw sewage.  ultrafiltration (uf) followed by qiaamp viral rna mini kit provided a comparable whole process recovery of φ6, ranging from -1.19 to -0.45 log (6.4 -35.8 %), with ms2. j o u r n a l p r e -p r o o f  electronegative membrane vortex (emv) provided significantly different whole process recovery of ms2 and φ6 depending on the water quality of raw sewage; the recovery was reduced in raw sewage containing higher tss and uv 260 .  the successful recovery of the enveloped virus by peg precipitation might need an appropriate rna extraction method (e.g., acid guanidinium thiocyanate-phenol-chloroform rna extraction). not only primary concentration but also the following molecular process should be optimized for the efficient recovery of enveloped viruses.  non-enveloped surrogate (ms2 and mnv) did not necessarily validate the success of the primary concentration and molecular process of φ6 (e.g., peg+qiaamp viral rna mini kit). this indicates enveloped viruses should be spiked to primary concentrate as whole process control and molecular process control to validate the quantification of enveloped viruses from raw sewage.  the modified peg + trizol method was successfully applied to detect sars-cov-2 rna by cdc n1 and n3 assay from raw sewage collected on 6 th ,16 th , and 29 th in july 2020 in tokyo metropolis. j o u r n a l p r e -p r o o f shotaro torii: investigation, resources, funding acquisition writing -review & editing. katayama 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development of genetic diagnostic methods for novel coronavirus 2019 (ncov-2019) in japan cross-platform evaluation of commercial real-time reverse transcription pcr master mix kits using a quantitative 5′nuclease assay for ebola virus impact of repeated pressurization on virus removal by reverse osmosis membranes for household water treatment viral multiplex quantitative pcr assays for tracking sources of fecal contamination virological assessment of hospitalized patients with covid-2019 sars-cov-2 titers in wastewater are higher than expected from clinically confirmed cases survivability, partitioning, and recovery of enveloped viruses in untreated municipal wastewater shotaro torii: investigation, resources, funding acquisition writing -review & editing. katayama hiroyuki: resources, project administration, funding acquisition, supervision, writing -review & editing key: cord-347354-1bh6ncls authors: rodrigues, marcos; gelabert, pere j.; ameztegui, aitor; coll, lluis; vega-garcía, cristina title: is covid-19 halting wildfires in the mediterranean? insights for wildfire science under a pandemic context date: 2020-10-08 journal: sci total environ doi: 10.1016/j.scitotenv.2020.142793 sha: doc_id: 347354 cord_uid: 1bh6ncls wildfires in the mediterranean are strongly tied to human activities. given their particular link with humans, which act as both initiators and suppressors, wildfire hazard is highly sensitive to socioeconomic changes and patterns. many researchers have prompted the perils of sustaining the current management policy, the so-called ‘total fire exclusion’. this policy, coupled to increasingly fire-prone weather conditions, may lead to more hazardous fires in the mid-long run. under this framework, the irruption of the covid-19 pandemic adds to the ongoing situation. facing the lack of an effective treatment, the only alternative was the implementation of strict lockdown strategies. the virtual halt of the system undoubtedly affected economic and social behavior, triggering cascading effects such as the drop in winter-spring wildfire activity. in this work, we discuss the main impacts, challenges and consequences that wildfire science may experience due to the pandemic situation, and identify potential opportunities for wildfire management. we investigate the recent evolution of burned area (retrieved from the mcd64a1 v006 modis product) in the eu mediterranean region (portugal, spain, france, italy and greece) to ascertain to what extent the 2020 winter-spring season was impacted by the public health response to covid-19 (curfews and lockdowns). we accounted for weather conditions (characterized using the 6-month standardized precipitation evapotranspiration index; spei6) to disregard possible weather effects mediating fire activity. our results suggest that, under similar drought-related circumstances (spei6 ≈ -0.7), the expected burned area in 2020 during the lockdown period in the eu (march-may) would lay somewhere within the range of 38,800 ha ± 18,379 ha. instead, the affected area stands one order of magnitude below average (3,325 ha). this stresses the need of considering the social dimension in the analysis of current and future wildfire impacts in the mediterranean region. mobility allowed during a significant amount of time, at least several weeks. the strength and duration of such measures varied from one region to another, yet the european mediterranean region (eumed, e.g., portugal, spain, france, italy and greece) remained under countrywide lockdowns spanning from march to may 2020 (thomas et al., 2020) . despite the positive epidemiological effect, the post-lockdown economic scenario is looking grim and countries are experiencing large gdp drops, which will intensify in the near future. from an environmental perspective, the response to covid-19 has caused noticeable impacts such as the unparalleled drop in air pollution over some of the largest metropolitan areas in the world (saadat et al., 2020; zambrano-monserrate et al., 2020) . nevertheless, the sustained cessation/reduction of human activities poses unforeseen implications over anthropogenic dominated landscapes, and has set an open and ongoing debate between those who see the pandemic as an opportunity to demonstrate environmental restoration potential options and those who advocate about potential negative impacts in the future (chakraborty and maity, 2020) . in the particular case of wildfires, the cessation of human activity may reduce their incidence in the very short-term, especially during the winter-spring season, known to be the most associated with human-related fire occurrence (rodrigues et al., 2018) . however, researchers, managers and firefighters are already warning about the potential subsequent impacts on and of wildfires. for example, the lack of activity may lead to a significant reduction in forest management -especially of interventions without immediate economic return such as fuel reduction treatments-, fuel accumulation, and limited or impaired firefighting capability (social distancing), which coupled to fire-prone conditions and budget limitations, may foster extreme wildfires (ewes) in the mid-to-long run. furthermore, given the increased severity of the disease in people with previous pathologies, especially respiratory ones, smoke from ewes may boost the vulnerability to the virus (emami et al., 2020) . so far, the pandemic raised more questions than answers, though the entire society and especially the scientific community, is working towards solving the most pressing ones. what is going to happen under a scenario of budgetary constraints and likely subsequent infection waves is yet to be seen, but surely merits further research efforts. in this work, we present a preliminary and concise analysis of the potential impacts in wildfires of the societal and public health response to covid-19. we analyzed wildfire activity during the lockdown j o u r n a l p r e -p r o o f journal pre-proof period in the eumed countries -march to may-focusing on the progression of burned area during the most recent decades (2003) (2004) (2005) (2006) (2007) (2008) (2009) (2010) (2011) (2012) (2013) (2014) (2015) (2016) (2017) (2018) (2019) (2020) . we paid special attention to weather conditions (characterized using the 6-month standardized precipitation evapotranspiration index; spei6) so that we could better isolate the actual effect of curfews and lockdowns. the spei is a well-known indicator of water balance and drought conditions that has been previously used to predict fire activity (marcos et al., 2015) or in the analysis of some of the most recent extreme wildfire episodes in portugal (turco et al., 2019) and australia (nolan et al., 2020) . our main goal was to determine to what extent the response to covid-19 has affected wildfires under the hypothesis that the cessation of human activity would prompt a drop in wildfire incidence. within this framework, we discuss possible implications and opportunities for wildfire science. data on burned areas were obtained for the most fire-affected countries in the eumed region -portugal, spain, italy, france and greece-all of them experiencing strict lockdowns and mobility restrictions. we retrieved the burned area extent during the lockdown period -march to may-on a yearly basis since 2003, using the modis product mcd64a1 version 6 (giglio et al., 2018) . the mcd64a1 product provides reliable, homogeneous and up-to-date data since 2003 (boschetti et al., 2019) , distributed in monthly raster files at 500x500 meter resolution. values of burned area were summarized into yearly time series by country, expressing them as z-scores (subtracting the mean and dividing by its standard deviation) to enable direct comparisons between countries while also enabling their interaction with spei. additionally, we also characterized the thermo-pluviometric conditions using the 6 months spei (spei6) based on may (thus covering the period december-may). spei6 was retrieved on a yearly basis as calculated in the global drought monitor (beguería, 2017) , which provides spei values at 1x1 degree conditions (e.g., 2005, 2011, 2012 and 2015) , instead of the current 3,325 ha in 2020 (table 1) . it has long been recognized that ignition probabilities are determined by human activities but most of previous scientific work has modelled ignitions from weather and geographical variables eluding the link with human-related drivers (costafreda-aumedes et al., 2017; rodrigues et al., 2018) . therefore, direct impacts of changing socio-economic activities in fire incidence remained unquantified until now (françois-nicolas et al., 2018) . under strict limitations on human activities, winter-spring 2020 fires have experienced a measurable and significant decrease in all eumed countries, becoming an outlier in fire statistics. wildfire records for 2020 clearly separate from previous trends so far, posing a challenge for data management and interpretation in future analyses. it remains to be determined how lastly the effects of the pandemic will affect fire incidence (the 2020 summer season, longer?), but implications for future wildfire research are evident, if only to measure how fire activity would respond to cessation of human activity in the mediterranean. in the event of upcoming waves conducive to further mobility/activity restrictions, we may experience decreased fires for an undetermined period. quantitative assessments like ours may be conducted elsewhere, or even globally, allowing identifying disruptions in fire activity and possibly preparing for exacerbated fires in the future, since sustaining this situation in time or subsequent lockdowns may well promote fuel built-up due to decreased vegetation management. once budget and personnel constraints due to the likely economic recession reach fire governance structures and combine with the expected increased frequency of droughts and fire weather danger (jolly et al., 2015; turco et al., 2017) , a perfect-storm confluence of conditions may trigger amplified wildfire disasters. on the other hand, certain covid-related responses may exert a direct influence on firefighting capability. to the expected decline in means and resources due to budgetary constraints, specific measures like individual quarantines may add to the existing limitations in personnel. in the same line, social distancing strategies may also hinder firefighting or prescribed burning training operations and volunteer activities (i.e. forest defense associations, adf in spain) by impeding practices requiring close teamwork at the threat of infection. the unpredictable mid-term consequences of covid-19 on fire regime dynamics add uncertainty on top of an already controversial clash of current and proposed management frameworks, i.e., "fire exclusion" versus sbegueria/{speibase}: {version} 2 standardized precipitation evapotranspiration index (spei) revisited: parameter fitting, evapotranspiration models, tools, datasets and drought monitoring global validation of the collection 6 modis burned area product how does drought impact burned area in mediterranean vegetation communities? covid-19 outbreak: migration, effects on society, global environment and prevention human-caused fire occurrence modelling in prevalence of underlying diseases in hospitalized patients with covid-19: a systematic review and meta-analysis wildfire risk as a socioecological pathology summary note of a global expert workshop on fire and climate change the collection 6 modis burned area mapping algorithm and product climate-induced variations in global wildfire danger from 1979 to seasonal predictability of summer fires in a mediterranean environment causes and consequences of eastern australia"s 2019-20 season of mega-fires. glob democratizing wildfire strategies. do you realize what it means? insights from a participatory process in the montseny region fire regime dynamics in mainland spain. part 1: drivers of change a comprehensive spatialtemporal analysis of driving factors of human-caused wildfires in spain using geographically weighted logistic regression environmental perspective of {covid}-19 oxford {covid}-19 {government} {response} {tracker} decreasing fires in mediterranean europe we thank the two anonymous reviewers for the insightful comments, which have undoubtedly contributed to improve this work. key: cord-350236-7fit8q1s authors: wan, bin; zhang, xinlian; luo, dongxia; zhang, tong; chen, xi; yao, yuhan; zhao, xia; lei, limei; liu, chunmei; zhao, wang; zhou, lin; ge, yuqing; mao, hongju; liu, sixiu; chen, jianmin; cheng, xunjia; zhao, jianlong; sui, guodong title: on-site analysis of covid-19 on the surfaces in wards date: 2020-08-18 journal: sci total environ doi: 10.1016/j.scitotenv.2020.141758 sha: doc_id: 350236 cord_uid: 7fit8q1s abstract sars-cov-2 has erupted across the globe, and confirmed cases of covid-19 pose a high infection risk. infected patients typically receive their treatment in specific isolation wards, where they are confined for at least 14 days. the virus may contaminate any surface of the room, especially frequently touched surfaces. therefore, surface contamination in wards should be monitored for disease control and hygiene purposes. herein, surface contamination in the ward was detected on-site using an rna extraction-free rapid method. the whole detection process, from surface sample collection to readout of the detection results, was finished within 45 min. the nucleic acid extraction-free method requires minimal labor. more importantly, the tests were performed on-site and the results were obtained almost in real-time. the test confirmed that 31 patients contaminated seven individual sites. among the sampled surfaces, the electrocardiogram fingertip presented a 72.7% positive rate, indicating that this surface is an important hygiene site. meanwhile, the bedrails showed the highest correlation with other surfaces, so should be detected daily. another surface with high contamination risk was the door handle in the bathroom. to our knowledge, we present the first on-site analysis of covid-19 surface contamination in wards. the results and applied technique provide a potential further reference for disease control and hygiene suggestions. in early 2020, severe acute respiratory syndrome coronavirus 2 (sars-cov-2) spread across the globe, causing more than 20 million infections and 700,000 deaths as of aug 13, 2020 (dong et al., 2020) coronavirus can spread through the air and survives on various surfaces for considerable periods. on june 18, beijing reported new incidents related to the xinfadi market cluster (owen, 2020) covid-19 was discovered on the surface of chopping boards used for imported salmon at the xinfadi food market, providing that covid-19 could survive on material surfaces. previous researches reported that the covid-19 virus can inhabit the surface of materials in wards. (guo et al., 2020; these researchers confirmed the virus by real time reverse transcription polymerase chain reaction (rt-pcr), which typically performs deactivation, nucleic acid extraction, and rt-pcr amplification of the collected samples. however, nucleic acid extraction risks nucleic acid losses and places high demands on the detection limit. furthermore, the whole nucleic-acid extraction and amplification process requires approximately 2.5-4 hours for one batch of detection. therefore, a rapid detection method should be applied j o u r n a l p r e -p r o o f journal pre-proof for on-site covid-19 identification in the environment. loop-mediated isothermal amplification (lamp) has achieved brilliant performance in pathogenic virus detection, accomplishing amplification within 45 minutes (liu et al., 2018) . lamp assay also performs nucleic acid amplification without requiring nucleic acid extraction (lalli et al., 2020) , thus preventing rna damage through a tedious process. for these reasons, we applied lamp in our present report on surface-contamination detection. patients with confirmed covid-19 are retained for over two weeks in rooms with many living and medical apparatuses. nosocomial transmission plays a major role in viral spread and infection, especially in wards. confirmed patients living in the ward can spread viruses through coughing or even shortness of breath (ghinai et al., 2020) . this experiment aimed to determine the concentration of surface contaminants in wards of the chengdu center of disease control (chengdu cdc), which has been designated for the treatment of covid-19 patients during the disease outbreak. samples were collected from seven sites: 1) bedrail; 2) bedside cupboard; 3) chairs; 4) door handles of the bathroom; 5) light switches; 6) remote controller or beeper; 7) fingertip of electrocardiograph (ecg) monitoring. the samples were collected on 18th, 19th and 24th mar, 27th and 28th apr of 2020. the sampling site was illustrated in figure 1 (a). the correspondences between patient clinical information and collected samples were listed in table s the surface contamination samples were collected as described index a of the hygienic standard for disinfection in hospital (chinese national standard, gb 15892-2012). briefly, a 5 cm × 5 cm standard scale board was placed on the surface of sampling material, and the surface was evenly rubbed within the 25-cm 2 area with a cotton swab wetted with 0.9% sodium chloride. after swiping, the cotton swab was immersed in 1 ml 0.9% sodium chloride solution prepared for nucleic-acid amplification detection. the collected surface-contamination samples were immediately transferred to the bsl-2 laboratory next to the chengdu cdc wards for analysis. viral contamination was detected by a nucleic acid extraction-free isothermal detection kit, specifically, a novel coronavirus real-time isothermal amplification kit (cat.no. pcsyhe), acquired from shanghai fosun long march medical science co., ltd and certificated by 7 the detection process was performed following by manufacture's instructions. for each batch, we prepared sufficient reaction reagent for n tested samples plus two control samples. that is, n × 1 μl of bst enzyme, n × 1 μl of rt ii enzyme, and n × 18 μl of covid-19 gene reaction reagent were added to a centrifuge tube, mixed by shaking, and centrifuged at low speed for a few seconds. after separation, 20 μl aliquots were pipetted into pcr reaction tubes. the reaction tubes could be placed at 2~8 °c for 3 hours at most after separation. next, 5 μl of the samples were added to different pcr reaction tubes. a 5-μl negative control and 5 μl-positive control were added to the control wells. the five positive samples from the handles were 100% associated with positive results from the ecg fingertips positive results. four positive cases from the handles were also associated with positive results from bedrails, and three cases were associated with positive results from cupboards and light switches. therefore, a surface contamination sample from the door handle can be interpreted as an ultra-high risk label. in daily monitoring, the bathroom door handles should be swabbed and analyzed. when the samples from a door handle report positive results, the corresponding ward poses an enhanced hygienic challenge. three of the collected samples (samples #0324-27, #0324-11, and #0427-l5) presented on six contaminated surfaces. all of these confirmed cases came from j o u r n a l p r e -p r o o f outside mainland china and presented positive symptoms. on a 1-4 scale of clinical severity, where type 1 denotes mild cases and type 4 represents the severest cases, sample #0324-27 was classified as type 2, and samples #0324-11 and #0427-l5 were classified as type 3. the clinical symptoms might influence the contamination degree and infection risk. further research on these relationships is ongoing. we successfully applied an extraction-free sars-cov-2 isothermal amplification detection method to on-site analysis of surface contamination by covid-19 patients in wards. for each confirmed case, seven sites in the ward were collected and analyzed. the detection process is efficient and labor-saving, as desired for on-site covid-19 contamination detection. among 31 cases collected from 18 march to 27 april of 2020, 72.7% reported positive amplifications on the ecg fingertip, indicating that this surface is an important hygiene site. the correlation results also confirmed that bedrails should be regularly monitored, as contamination on bedrail surfaces is relevant to many other contaminated surfaces. although the analysis can be performed by standard real-time pcr instruments, simpler isothermal amplification fluorescent instruments are suggested for on-site analysis, as they are less expensive, smaller in size, and more easily transported than standard pcr instruments. in future works, we will analyze the relationship between different clinical symptoms and surface contamination, which may reveal the transmission mode of covid-19 in wards. validated the method. yuqing ge, hongju mao, sixiu liu, jianmin chen, xunjia cheng, jianlong zhao, and guodong sui: conceived the idea, coordinated the project, and wrote the manuscript. -first report about on-site detection of sars-cov-2 in wards. -the whole detection process could accomplish within 45 minutes without nucleic acid extraction. -the presence of sars-cov-2 in wards was confirmed by nucleic acid isothermal amplification. j o u r n a l p r e -p r o o f prevention and control of major infectious diseases such as aids and viral hepatitis" (2018zx10732401-003-016); the science and technology commission of shanghai municipality (nos. 17jc1401000, 19441903700 and 18dz1113000) ，the national natural science foundation of china an interactive web-based dashboard to track covid-19 in real time first known person-to-person transmission of severe acute respiratory syndrome coronavirus 2 (sars-cov-2) in the usa rapid and extraction-free detection of sars-cov-2 from saliva with colorimetric a sample-to-answer labdisc platform integrated novel membrane-resistance valves for detection of highly pathogenic avian influenza viruses covid-19: who raises concerns about new cases in beijing environmental virus surveillance in the isolation ward of covid-19 sars-cov-2 rna detection of hospital isolation wards hygiene monitoring during the coronavirus disease 2019 outbreak in a chinese hospital the authors declare no competing interests. key: cord-303665-l57e54hu authors: lahrich, s.; laghrib, f.; farahi, a.; bakasse, m.; saqrane, s.; el mhammedi, m. a. title: review on the contamination of wastewater by covid-19 virus: impact and treatment date: 2020-09-10 journal: sci total environ doi: 10.1016/j.scitotenv.2020.142325 sha: doc_id: 303665 cord_uid: l57e54hu emerging viruses are a major public health problem. most zoonotic pathogens originate in wildlife, including human immunodeficiency virus (hiv), influenza, ebola, and coronavirus. severe acute respiratory syndrome (sars) is a viral respiratory illness caused by a coronavirus called sars-associated coronavirus (sars-cov). viruses are charged colloidal particles that have the ability to adsorb on surfaces depending on ph. their sorptive interaction with solid particles has important implications for their behavior in aquatic environments, soils, sewage sludge, and other solid materials and their removal or concentration by water treatment processes. current state of knowledge on the potential of wastewater surveillance to understand the covid-19 pandemic is reviewed. this study also identified wastewater irrigation systems with a higher risk of covid-19 transmission. emphasis was placed on methodologies for the detection and quantification of sars-cov-2 in wastewater. in light of recent epidemics around the world, there is increasing awareness of the risk of exposure to emerging pathogens during wastewater collection and treatment. emerging pathogens may enter wastewater systems from pathogen shedding in human waste, introduction of decontamination wastewater, illicit activity, animal farming, and hospital effluents, or surface water runoff following a wide-area biological incident. some emerging pathogens (e.g., ebola virus [ebov] and sars-cov-2) pose a significant health threat and their exposure in a wastewater system could have potentially serious health consequences. the need to assess the potential exposure and transmission of disease through sanitation systems is therefore necessary. excretion of sars-cov-2 and its rna from the body in saliva, sputum, and feces can be found in sewage. the main route of transmission of this virus would be inhalation by person-to-person transmission and aerosol/droplet, as well as fomite and hand contamination. however, currently available data indicate that there is a need to better understand the role of wastewater as a potential source of epidemiological data and a risk factor for public health. the detection of sars-cov-2 in feces has prompted several groups around the world to promote the analysis of wastewater to assess its circulation in populations (mallapaty, 2020; lodder and de roda the prevalence of sars-cov-2 and take appropriate measures to prevent and control the spread of the disease in the community. however, it is very difficult to track the virus because most people are asymptomatic; and further, it is not possible to do active clinical testing of all individuals, due to resource and cost constraints. furthermore, covid-19 may also display second or more waves. under these circumstances, the passive, but effective, method of sewage or wastewater monitoring can be used to trace and track the presence of sars-cov-2, through their genetic material rna, and screen entire community. the presence of sars-cov-2 in wastewater is predictable because it can infect the gastrointestinal tract and are shed through the stools of the patients (xiao et al., 2020; leung et al., 2003; zumla et al., 2015; gu et al., 2020) . with the objective of keeping the water community informed of covid-19 related findings, this review highlights the recent scientific evidence, as well as topics not previously discussed. emphasis was placed on their presence and persistence, as well as detection methods in different water matrices. virus-infected wastewater treatment techniques are also highlighted. environmental persistence refers to the length of time a pathogen, such as the sars cov-2, is able to survive outside the human body; the longer it survives, the more likely it is to cause infection. for the most part, investigations on the fate of viruses in the aquatic environment have focused on non-enveloped enteric viruses, given that these viruses are characterized by high resistance under a variety of environmental conditions (annalaura et al., 2020) . as for the number of studies concerning the fate of enveloped viruses in aquatic compartments, it is rather limited, because enveloped viruses are predisposed to deactivate in water (wigginton et al., 2015) . in fact, although enveloped viruses are inactivated more quickly than non-enveloped j o u r n a l p r e -p r o o f journal pre-proof viruses, the survival time of enveloped viruses can still be very long depending on the specific environmental conditions. this is explained by the fact that the surface s-proteins ( figure 1 ) are deeply anchored and only pass through the envelope: if the envelope is altered, but the surface sproteins are preserved, infectivity is maintained. the persistence of viruses can be affected both by the type of environment (e.g., surface, water, wastewater) and by the physical and chemical properties of the environment (e.g., temperature, ph, humidity, exposure to sunlight and the type of surface (rzeżutka and cook, 2004; thevenin et al., 2013) . furthermore, it is also possible to be influenced by the composition of the media. this is consistent with a recent study published detailing the survival rates of sars-cov-2 on different non-living surfaces: 72 hours on stainless steel and plastic, 24 hours on cardboard, and 4 hours on copper (van doremalen et al., 2020) . studies to verify the survival of sar-cov and sar-cov-2 have a strong phylogenetic similarity (forster et al., 2020) , showing the survival rate of a pathogen with a viral titer of 10 5 on aluminum, plastic, metal, wood and paper of 4-5 days at room temperature (kampf et al., 2020) . generally speaking, viruses are microscopic pathogenic agents ranging in size from 18 to 1500 nm (hurst and gerba, 1989) and are abundant in water and wastewater (gantzer et al., 1998) , especially domestic and urban effluents, which are particularly laden with animal and bacterial viruses. these two groups are of particular interest for environmental and human health studies. infected subjects are considerable and can have up to 10 10 per gram of stool (masson, 1996) . the transmission of these viruses to humans generates several diseases and epidemics that affect all age groups. in some cases, they can be fatal for children (e.g., gastroenteritis leading to morbidity and mortality during the first five years of life) (parashar et al., 2013) . humans are considered to be the primary contaminator, and secondary receptor (gantzer et al., 1998) . several potential routes ensure viral transmission to humans: domestic use of the contaminated surface, or groundwater, bathing in contaminated water, consumption of infected seafood, or crops grown in contaminated soil. there are many different types of viruses to include, for example, picornaviridae (e.g. polioviruses, echoviruses, and hepatitis a), reoviridae (e.g. reoviruses, rotaviruses), adenoviridae (e.g. adenovirus a.), coronaviridae (e.g. coronaviruses), caliciviridae (e.g. caliciviruses), small round viruses (e.g. astroviruses, norwalk), and bacteriophages (gantzer et al., 1998; girard and hirth, 1989; havelaar, 1991; grabow et al., 1995; havelaar et al., 1986; havelaar et al., 1986; havelaar et al., 1990; joffre, 1991) . according to kai et al. (1985) , their concentration in the feces is less than l0 5 particles per gram. owing to their characteristics, bacteriophages are considered by researchers as indicators of fecal pollution and as models for monitoring the fate of viruses in different water environments and wwtp (havelaar, 1991) . bacteriophages have a morphology, structure, and composition similar to those of enteric viruses. resistance and behavior, especially of f-specified rna phages, are comparable to those of enteric viruses (havelaar, 1991; havelaar et al., 1988; lewis, 1995) . concretely, on the one hand, phages are not involved in human pathology. one of the main problems is the spread of viruses between polluted environmental waters and populations. it happens that water is contaminated by humans on the one hand, and water becomes a means of infection for humans on the other hand. since wastewater contains viruses that are repelled by everyone, regardless of their health, monitoring for viruses in wastewater and environmental waters that receive effluent from wastewater treatment plants (wwtps) can determine the true prevalence and molecular epidemiology of gastroenteritis viruses and the risks to human health (guan et al., 2020; huang et al., 2020; wang et al., 2020a) in a given geographical area rather than clinical research (prevost et al., 2015; kazama et al., 2017) . such data would be a useful indicator, especially for poor countries, as it would allow simple, reliable and inexpensive epidemiological surveillance. in such a situation, the two fundamental factors that require attention to prevent the spread of infection, especially in high-risk locations such as hospitals, are the interconnection of the plumbing system and its condition (gormley et al., 2020; xiao et al., 2020) . the genetic material of sars-cov-2 has been detected in the feces of covid-19 patients with or without gastrointestinal symptoms (wölfel et al., 2020; lescure et al. 2020 ) and in cured individuals who no longer have symptoms (wölfel et al., 2020; lescure et al. 2020; holshue et al., 2020) . however, the presence of sars-cov-2 genetic material in the stool does not necessarily indicate infection or disease. a few studies that have attempted to detect a viable infectious virus in the stool have produced conflicting results. three studies reported the detection of live virus (wölfel et al., 2020; lescure et al. 2020; holshue et al., 2020) in the stool and one study reported no detection of live virus despite the detection of the sars-cov-2 genetic material (holshue et al., 2020) . researchers in netherlands were the first to successfully isolate and detect sars-cov-2 in wastewater (medema et al., 2020) . they demonstrated that the coronavirus genome can be detected at several wastewater collection sites within days of the identification of the first human case of covid-19. this hypothesis was confirmed by wurtzer and his colleagues (https://www.sciencemag.org/news/2020/04/coronavirus-found-paris-sewage-points-early warning-system). it also demonstrates, for the first time, that the quantities of viral genomes detected in wastewater are increasing in line with the number of covid-19-related hospitalizations at the regional level. preliminary results obtained even more recently at the same sites show a very significant reduction in the viral load in wastewater, an expected consequence of containment measures on the circulation of the virus. queensland and the australian national scientific agency csiro that took samples from a suburban pumping station and wwtp. they analyzed the wastewater samples using rt-pcr tests, which helps identify gene fragments of the sars-cov-2 virus. this is also the method used by hospitals to test for the virus in human samples. passive surveillance through wastewater mining and monitoring of sars-cov-2, as a subset of the national water quality monitoring network, therefore, can be utilized to assess community or public health in covid-19 pandemic as well as post-pandemic scenarios. the monitoring should commence in red, orange, as well as green zones to alert health officials in advance about the possible second wave of covid-19. however, these methods remain more difficult, especially for sars-cov-2, and take more time than most molecular techniques, which explains why they are less frequently used. in order to develop and test methods for monitoring sars-cov-2 genetic material in sewage, a study is currently underway (kitajima et al., 2020) . with this approach, it is possible to estimate the frequency of the disease in communities, identify areas where few tests are performed, predict a possible second wave of infection, and monitor vaccine results. the approach is not yet ready and is not an alternative to human testing. there are then creations of a risk to public health either as a result of the contamination of water bodies by migration of viruses through the soil or the consumption of contaminated market garden produce. the reuse of treated and untreated wastewater in agriculture is a practice that is steadily increasing. it is therefore important to know the fate of these viruses, particularly on plants. this can only be done with enteric viruses that can multiply on cell cultures. indeed, the presence of viral genome does not indicate the presence of infectious viral particles. studies reported in the literature show that viruses can survive on plants irrigated with sewage for variable periods ranging from a few days to nearly 4 weeks depending on conditions (badawy et al., 1990; tierney et al., 1977) . in addition to the nature of the vegetable under consideration, it appears that two factors have a fundamental influence on the survival time of viruses on plants after irrigation. these are the initial level of contamination and the temperature associated with sunlight. it must be fully aware that even in regions with a very hot climate it takes more than 6 hours to achieve a 2-log reduction in virus contamination. this means, for example, that in case of irrigating a golf course with wastewater in the morning, enteric viruses are likely to be still present when the players will be on the course during the day. the same situation can be found on irrigated lawns in public parks. in both cases, players or children are likely to come into contact with enteric viruses. on the other hand, with regard to vegetables, it is clear, and this has been well confirmed by croci et al., (1991) , that plants irrigated during cultivation with contaminated water retain significant amounts of viruses on their surface. in addition, storage at +4°c not only does not accelerate viral inactivation but slows it down. it is therefore extremely important to have virusfree vegetable crops at harvest time. figure 2 illustrates the potential impacts of reusing recycled wastewater for agricultural irrigation. in addition, since the onset of the crisis, the impact of the covid-19 pandemic on the environment has attracted attention, including observation and analysis of recent impacts, and estimates related to long-term changes. qualitative assumptions prevail, while consistent quantitative research must await relevant data sets and additional knowledge. most aspects of the environmental impact of the covid-19 pandemic do not come directly from the virus itself. sudden restrictions or closures of economic sectors (such as heavy industry, transportation, or hotel businesses) had a direct impact on the environment. from an anthropocentric point of view, the pandemic may lead to a more sustainable future, and particularly to more resilient socioecological systems or shorter supply chains, which is a positive development. however, countries can still choose less sustainability by pursuing rapid economic growth and reducing environmental concerns. although the overall negative impact on the economy and society can be enormous, it is likely that the reduction in global economic activity due to the covid-19 crisis will trigger many major improvements in the quality of service of the environment and climate systems. however, not all the environmental consequences of the crisis are or will be positive. some of these include the increase in the amount of non-recyclable waste, the large amount of organic waste generated due to declining agricultural and fisheries exports, as in many countries in the world, wastewater offers morocco an alternative solution as the pressure on freshwater is constantly increasing, particularly due to repeated droughts. in the country, wastewater reuse is intended for industry, particularly phosphate washing, but also for golf course irrigation. a letter from the ministry of the interior addressed to the local authorities prohibits the use of wastewater before it has been treated due to the possible presence of traces of genomes from the stools of affected persons (https://www.leconomiste.com/article/1061485-leseaux-usees-un-moyen-de-tracage-du-covid-19). the letter mentions that the use of this wastewater is set by the laws and regulations in force. the detection of viruses in wastewater and drinking water requires the following detection methods: sensitive, resistant to false-positive results, and enabling full automation. in addition, journal pre-proof the method used must be fast and inexpensive. a method, which fulfills all needed requirements, as yet was not worked out. in addition to economic agents, the implementation of methods for the detection of viruses in the aquatic environment can come up against several obstacles, including: the considerable dilution of the sample, the influence of the environmental matrix on the analytical results and the mutagenic variability of viruses. in faecally contaminated water, viruses are present in relatively small amounts. it is therefore often necessary to concentrate the samples before determining the exact virus content (marzouk et al., 1979) . these include, for example: polymerase chain reaction (pcr) (li et al., 2002; pina et al., 1998; lee et al., 2005; cho et al., 2000; fout et al., 2003; schvoerer et al., 2000) , nucleic acid sequence-based amplification (nasba) (rutjes et al., 2006; jean et al., 2002; jean et al., 2001) , dna chip technique (nettikadan et al., 2003; alhamlan et al., 2013) , atomic force microscope (afm) (nettikadan et al., 2003) , fluorescence microscopy (hara et al., 1991; hennes et al., 1995; noble et al., 1998; shibata et al., 2006 ; wen et al., 2004 ; weinbauer and suttle, 1997) , electron microscopy (weinbauer and suttle, 1997; bettarel et al., 2000 ; alonso et al., 1999; wommack et al., 1992) , biosensor application (liu and zhu, 2005; rengevych et al., 1999) , enzyme-linked immunosorbent assay (elisa) (kittigul et al., 2000; nasser et al., 1987; el-esnawy, 2000; nishida et al., 2009 ) and flow cytometry (marie et al., 1999; abad et al., 1998 ; brussaard, 2004 ; chen et al., 2001) . some of these methods have been modified by: i) concentration (elisa tests, pcr and nasba reactions, application of microarrays) (li et al., 2002; alhamlan et al., 2013; kittigul et al., 2000) , ii) combination of different methods (pcr reaction combined with plate-forming tests, atomic force microscopy combined with protein microarray technology) (straub et al., 1995; haab et al., 2001; zhu et al., 2001) , iii) change in the pore size of the filter (epifluorescence microscopy) (weinbauer and suttle, 1997) , iv) dilution of the sample (flow cytometry) (nettikadan et al., 2003) . combined journal pre-proof methods can also be used. for example, the combination of pcr with plate formation tests is possible. polymerase chain reaction is used to amplify the specific sequence of deoxyribonucleic acid (dna). in this reaction, double-stranded dna, called template dna, is amplified. the pcr technique, because of its high specificity, has been adopted for several years for the detection of viruses in the environment, in particular enteroviruses and hepatitis a virus (hav) (egger et al., 1995; gantzer et al., 1997) . pcr is a technique that amplifies (i.e. synthesizes many copies) a specific segment of dna of interest using short sequences of synthetic nucleotides called primers that bind to unique regions of the target genome for organism-specific identification. while much simpler than cell culture, molecular methods also present many challenges. the (li et al., 2002) . molecular methods pose another problem when it comes to translating nucleic acid test results in public health risks. using nucleic acid-based analysis, the result is the expression of all viral genetic material present, without distinguishing between infectious and non-infectious particles (metcalf et al., 1995) . it is beyond the scope of pcr to measure the extent to which viruses are affected by different disinfectants. in fact, pcr targets specific parts 2005). in addition, the technology is highly sensitive and allows observation of the interaction between molecules in real-time (liu and zhu, 2005; keusgen et al., 2002) . considering the need for rapid information on the infection status of the population, and the presence of the virus in the environment, biosensors can play an essential role in the diagnosis and surveillance of the disease in the current global pandemic. qiu et al. (2020) were able to demonstrate a dual-function plasmonic biosensor that combines plasmonic photothermal effect (ppt) and localized surface plasmon resonance (lspr) to detect sars-cov-2 rna transduction without the use of rt-pcr. the biosensor demonstrated high specificity and a low detection limit of sars-cov-2 sequences down to 0.22 pm (qiu et al. 2020) . as the viral concentration is relatively low in a patient sample, the detection limit is of paramount importance. loc devices appear to have the lowest detection limits, making them most immediately relevant for this application (qiu et al. 2020; peng et al., 2019; kaarj et al., 2018; seo et al., 2020) . plaque forming tests connected with pcr reaction enable detection of viruses present in water in time of 2 to 4 days (straub et al., 1995) . in this method, the detection period is considerably shorter than that of the traditional plate-forming test, as well as a shorter incubation period. techniques based on biosensors in terms of time-saving are much better (liu and zhu, 2005) . comparison of described methods is presented in table 1 . insert table 1 6 wastewater treatment is designed to reduce or eliminate suspended solids, dissolved and particulate organic matter, nutrients, and heavy metals. the degree of wastewater treatment is with well-designed and well-functioning wastewater treatment plants and on-site sanitation systems with reliable in-situ disposal or a network for emptying and discharge to a sewage sludge treatment plant, the risk posed by fecal pathogens, including sars-cov-2, should be limited. as a further precaution, wwtps may consider adding a final disinfection step (often called tertiary treatment) to further reduce the risk posed by viral pathogens, such as sars-cov-2, before spilling. the methods are available for the inactivation of viruses in wastewater effluents and water range from the purely physical (ionizing radiation by gamma rays, non-ionizing radiation by ultraviolet light, photodynamic oxidation and heat) to the purely chemical (chlorine, chlorine dioxide, ozone, iodine, bromine, and bromine chloride). two treatments such as the addition of chlorine to provide a residue after ozonation can be used to produce finished water free of toxic residues. chlorine is the most widely used disinfectant because it is effective at low concentrations, relatively inexpensive, and forms a residue if applied in sufficient doses. it can be applied as gas or hypochlorite, the gaseous form being the most common. chlorine gas reacts readily with water to form hypochlorous acid and hydrochloric acid; the hypochlorous acid produced then hypochlorous acid (hocl) form is the main form of chlorine responsible for its disinfecting properties. at neutral and lower ph levels, more hocl is formed, resulting in greater disinfection capacity at these ph levels. chlorine in the form of hocl or oclis the available free chlorine. the combination of hocl with ammonia and organic compounds in wastewater produces combined chlorine in the form of chloramines. low-level wastewater disinfection can effectively inactivate sars-cov-1 (0.5 mg l -1 free chlorine residual), although standard dosage recommendations must be followed (wang et al., 2005) . therefore, the safety of drinking water and wastewater depends on the appropriate selection of the disinfectant dose and contact time in the treated environment, which are very important analytical techniques and methods that can detect viruses. viruses are charged colloidal particles that have the ability to adsorb on surfaces. their adsorption interaction with solid particles is very important for their behavior in aquatic and soil environments and for their elimination or concentration by water treatment processes (bitton, 1975) . to control the adsorption of viruses on surfaces, factors such as the type of virus and the relevant surface, ph, electrolytes, and the presence or absence of interfering substances in the suspension medium must be considered (bitton et al., 1976) . as with all other treatment systems capable of removing viruses from water and effluents, carbon requires continuing study. although it is not an exciting system for this purpose, carbon does retain viruses. the extent to which it acts as a filter by adsorbing or filtering other materials that adsorb viruses should be investigated. carbon, of course, is important in the disinfection process because it removes organic compounds that interfere with disinfectants. carbon may also alter effluent quality in a way that adversely affects disinfection. for example, iron used for coagulation may react in carbon columns and j o u r n a l p r e -p r o o f journal pre-proof subsequently reduce iodine making it unavailable for disinfection. problems of this kind must always be monitored. treatment processes are generally unable to remove all viruses from sewage. research must therefore focus on how best to remove substances that interfere with the disinfection process from effluents and raw waters. techniques that lead to an increase in ph are of particular interest because strong alkalinity has a destructive effect on viruses. the concentration of viruses entering treatment facilities varies greatly from season to season, from one location to another, and even within 24-hours (bitton et al., 1976) . management of virus removal by treatment procedures requires coordination and synchronization of sampling. quantitative methods of virus concentration must be developed to accurately assess the effectiveness of treatments. the ability of some viruses to survive in disinfected effluent can be problematic (cromeans et al., 2010; li et al., 2017) . to overcome this dilemma, one solution is to adopt wastewater treatment technologies that achieve high levels of pathogen inactivation while removing carbon and nutrients. for example, the removal of pathogens (as well as biochemical oxygen demand (bod) and nutrient removal) can be achieved by size exclusion using membrane bioreactors (purnell et al., 2016) . but high membrane costs and frequent fouling limit their large-scale application. the efficient operation of membrane bioreactors is suggested in this regard by filtering coronaviruses attached to suspended solids (naddeo and liu, 2020) . use of electrospun nanofibre membranes, which have the property of attracting the genetic material of viruses, is a potential tool for wbe surveillance (venugopale et al., 2019) . in addition, pathogens can be reduced by bioabsorption, photodegradation, gravity settling or chemical lysis (curtis et al., 1992; curtis, 2003) . the use of algal-based wwt should also be evaluated. they were introduced in the 1950s to minimize the energy requirements of the activated sludge (as) process and/or improve secondary effluent to meet nutrient discharge standards. in recent years, algae-based wastewater treatment j o u r n a l p r e -p r o o f journal pre-proof systems have evolved to become sustainable and cost-effective alternatives to conventional, energy-intensive wastewater treatment systems (rawat et al., 2011; oswald and gotaas, 1957 ). these systems have been shown to inactivate pathogens at high levels while removing carbon and nutrients (young et al., 2016; buchman, 2014) . the presence of sars-cov-2 genetic material in wastewater can be used to monitor the spread of covid-19 in a community. the use of wastewater as a disease surveillance tool is not widespread, but it is beginning to grow. lack of a standardized protocol for monitoring sars-cov-2 in wastewater is a major challenge. detecting viral genetic material in wastewater requires a virus concentration step to enable extraction and detection, but there is limited knowledge on how to do this efficiently for sars-cov-2. understanding how the virus breaks down in the aquatic environment is also critical to assessing risks to human health at present; the stability of the sars-cov-2 genome in wastewater is unclear. it is possible to use an effective surveillance tool to provide an alert if viral particles rise above thresholds, allowing for quicker action and containing the infection before it spreads at an alarming rate. j o u r n a l p r e -p r o o f during this period, the authorities may reconsider their recommendations for local irrigation of wastewater. this also requires a renewed effort to promote micro-irrigation technology that can safely irrigate the soil without leaving the farmers and bring fresh produce into direct contact with the wastewater. as the latest data on sars-cov-2 and other coronaviruses show, they can survive on different environmental surfaces for hours or days. accordingly, further research is needed to better understand such differences in persistence duration. in this manner, supports-based these materials can be developed for the treatment of covid-19 in wastewater. j o u r n a l p r e -p r o o f j o u r n a l p r e -p r o o f biosensors  it enables rapid virus detection (virus detection using lab-on-a-chip methods takes 7 to 16 minutes)  low-cost analysis  size of biosensors enables easy transport  minimize sample and reagent volume  possibility of intermolecular observations in real time  high sensitivity  no sample pre-treatment  the range of transcription factor promoter pairs available  transcriptional regulation is rarely a simple process  the antibody binding capacity is strongly dependent on assay conditions (e.g. ph and temperature)  the antibody-antigen interaction is generally robust, however, binding can be disrupted by chaotropic reagents, organic solvents, or even ultrasonic radiation table 1 lahrich et al. j o u r n a l p r e -p r o o f comparative survival of enteric viruses and coliphage on sewage irrigated grass a comparison of methods for counting viruses in aquatic systems adsorption of viruses onto surfaces in soil and water factors affecting the adsorption of polio virus to magnetite in water and 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virucidal effect of a disinfectant on a non-enveloped virus applied onto a surface persistence of poliovirus 1 in soil and on vegetables grown in soil previously flooded with inoculated sewage sludge or effluent differences in viral disinfection mechanisms as revealed by quantitative transfection of echovirus 11 genomes aerosol and surface stability of sars-cov-2 as compared with sars-cov-1 novel wastewater surveillance strategy for early detection of coronavirus disease 2019 hotspots. current opinion in environmental science & health a novel coronavirus outbreak of applications and perspectives on microfluidic technologies in ships and marine engineering: a review study on the resistance of severe acute respiratory syndrome-associated coronavirus comparison of epifluorescence and transmission electron microscopy for counting viruses in natural marine waters accurate estimation of viral abundance by epifluorescence microscopy emerging investigators series: the source and fate of pandemic viruses in the urban water cycle virological assessment of hospitalized patients with covid-2019 distribution of viruses in the chesapeake bay guidelines on sanitation and health evidence for gastrointestinal infection of sars-cov-2 inactivation of indicator organisms in wastewater treated by a high rate algal pond system protein arrays and microarrays middle east respiratory syndrome key: cord-350714-zfprrxt4 authors: yao, ye; pan, jinhua; wang, weidong; liu, zhixi; kan, haidong; qiu, yang; meng, xia; wang, weibing title: association of particulate matter pollution and case fatality rate of covid-19 in 49 chinese cities date: 2020-06-20 journal: sci total environ doi: 10.1016/j.scitotenv.2020.140396 sha: doc_id: 350714 cord_uid: zfprrxt4 abstract the covid-19 epidemic, caused by the sars-cov-2 virus, has resulted in 3352 deaths in china as of april 12, 2020. this study aimed to investigate the associations between particulate matter (pm) concentrations and the case fatality rate (cfr) of covid-19 in 49 chinese cities, including the epicenter of wuhan. we used the global moran's i to analyze spatial distribution and autocorrelation of cfrs, and then we used multivariate linear regression to analyze the associations between pm2.5 and pm10 concentrations and covid-19 cfr. we found positive associations between pm pollution and covid-19 cfr in cities both inside and outside hubei province. for every 10 μg/m3 increase in pm2.5 and pm10 concentrations, the covid-19 cfr increased by 0.24% (0.01%–0.48%) and 0.26% (0.00%–0.51%), respectively. pm pollution distribution and its association with covid-19 cfr suggests that exposure to such may affect covid-19 prognosis. sars-cov-2 is a newly emerged coronavirus that has posed immense challenges to global health and has caused unpredictable economic loss. first reported in december of 2019 in wuhan, china, this novel coronavirus (covid-19) epidemic exhibits human-to-human transmissibility and has spread rapidly across countries (li et al., 2020) . as of april 12, 2020, a total of 1,610,909 covid-19 cases and 99,690 deaths have been confirmed in 211 countries, with china reporting a total of 82,214 j o u r n a l p r e -p r o o f 3 (conticini et al., 2020) . exposure to ambient particulate matter (pm) pollution has been reported to increase the risks of mortality and morbidity from cardiopulmonary diseases worldwide (atkinson et al., 2014; chen et al., 2017; samet et al., 2000; samoli et al., 2005) , with higher likelihood of adverse effects among elderly or people with underlying medical conditions (zeka et al., 2006) ; elderly and people with underlying medical conditions also experienced higher fatality from covid-19 pan et al., 2020) . toxicological evidence showed that pm can cause pulmonary inflammation and affect the defense system against infection (donaldson et al., 2001) . in addition, exposure to pm could increase inflammation and oxide stress, aggravating respiratory symptoms resulting in increased hospital emergency visits of patients with asthma and chronic obstructive pulmonary disease (copd) (epa, 2020). moreover, air pollution, especially pm pollution, is positively associated with case fatality from other coronavirus infection including severe acute respiratory syndrome (sars) (cui et al., 2003) . other studies have proposed that pm could carry viruses as carrier and spread viruses everywhere as a vector (alonso et al., 2015; yang et al., 2011) . to date, few studies have estimated and quantified the effects of air pollutants on case fatality rate (cfr) from covid-19. therefore, this study aims to investigate the associations between pm 2.5 and pm 10 and cfr of covid-19 in chinese cities. spatial auto-correlation statistics have been commonly used to examine spatial dependence or auto-correlation in spatial data. spatial auto-correlation includes 1) the global spatial auto-correlation which is used for estimating the overall degree of spatial auto-correlation for spatial data, and 2) the local indicators of spatial association (lisa) which is used to assess the influence of individual locations on the magnitude of the global statistic and to identify the locations and types of clusters. the spatial weights were created by rook contiguity rule, and applied to describe the spatial relationships among cities. we explored the spatial distribution of cfrs from 49 cities in china by calculating the global moran's i and lisa using arctoolbox of arcmap (version 10.2). the calculation formula of global moran's i is shown as following: lisa is computed as follows: j o u r n a l p r e -p r o o f 6 covid-2019 cfrs of all cities, and w ij is the spatial weight matrix corresponding to the cities pair i and j. global moran's i index is between -1.0 and 1.0. moran's i >0 represents positive spatial correlation, and the greater the value, the more obvious the spatial correlation. moran's i <0 represents negative spatial correlation, and the smaller the value, the greater the spatial difference. otherwise, moran's i = 0, the space is in random mode. the positively spatial correlation means that the correlation becomes more and more significant with the location (distance) aggregation, and vice versa. then, we conducted a cross-sectional analysis to examine the associations of figure 3a , χ 2 =15.25, p = 0.0042) and pm 10 ( figure 3b , χ 2 =13.53, p = 0.0090) during epidemic period in china. for every 10 ug/m 3 increase in pm 2.5 and pm 10 , the cfr increased by 0.24% (0.01%-0.48%) and 0.26% (0.00%-0.51%), respectively ( table 1 ). the risk estimates increased to 0.61% (0.09% -1.12%) and 0.33% (0.03% -0.64%) j o u r n a l p r e -p r o o f 10 the potential mechanism for pm exposure on respiratory outcomes might be the activation of inflammatory pathways in the small respiratory airways in response to pms, leading to the recruitment of inflammatory cells (kelly and fussell, 2011) . these biological mechanisms might potentially influence the prognosis of covid-19 patients. in this study, pm-fatality associations are significantly positive no matter if using average pm levels during epidemics period or in 2015-2019. considering that the patients died from covid-19 are likely stay in hospital for treatment without being directly exposed to ambient air pollution prior to death. therefore, we speculate that the effects of pm 2.5 and pm 10 on death mainly affect the progress of patients from mild to severe and prognosis, when the patients were not isolated from ambient air pollution. additionally, our results showed positive association between long-term pm exposure and covid-19 cfr, suggesting that long term pm exposure that prior to the epidemics period could have increased vulnerability of population to sars-cov-2. there is still a need to increase our efforts in the control of air pollutant emissions, critical for potential resurgence of covid-19 epidemics in the future. this ecological association study is limited by the duration of study period. j o u r n a l p r e -p r o o f 11 per capita to ensure the credibility of the results. also, the risk estimates stayed stable after adding other covariates including local lisa map values, city size and population or proportion of people older than 65 years. previous studies reported that some chronic diseases, such as hypertension, diabetes and cardiopulmonary diseases were also potentially linked to the pathogenesis of covid-19 (yang et al., 2020) ; thus the co-morbidities of these diseases may serve as confounders to associations of pm exposure and covid-19. the effects of prevalence of these diseases should be investigated further when data available. limited by the resolution of covid-19 data, which was only available at city level, exposure assessments of pm 2.5 and pm 10 in this study were done at city level based on ground monitoring data rather than using gridded predicting data of pm 2.5 and pm 10 at high spatial resolution (e.g. 1km×1km); using ground monitoring with limited spatial resolution might cause exposure misclassification. nevertheless, we believe that this exposure misclassification would not substantially bias our findings since: 1) the ground monitoring sites were normally located at areas of high population density in china that could reflect the exposure levels of the majority of residents; 2) and this kind of nondifferential misclassification j o u r n a l p r e -p r o o f figure 3a : cfr was positively associated (meta χ 2 =15.25, p=0.0042) with pm 2.5 in cities outside hubei (blue points, r=0.56, p=0.005) and those inside hubei except wuhan (green points, r=0.33, p=0.26) pollution. gdp per capita and hospital beds per capita effects were removed during statistical analysis. figure 3b : cfr was positively associated (meta χ 2 =13.53, p=0.0090) with pm 10 in cities outside hubei (blue points, r=0.48, p=0.019) and those inside hubei except wuhan (green points, r=0.47, p=0.11) pollution. gdp per capita and hospital beds per capita effects were removed during statistical analysis. average pm concentrations were calculated from january 15, 2020 to february 29, 2020 to represent the mean pm levels during the main period of panel studies of air pollution in patients with copd: systematic review and meta-analysis fine particulate air pollution and daily mortality. a nationwide analysis in 272 chinese cities can atmospheric pollution be considered a co-factor in extremely high level of sars-cov-2 lethality in northern italy? air pollution and case fatality of sars in the people's republic of china: an ecologic study air pollution, lung function and copd: results from the population-based uk biobank study ambient particle inhalation and the cardiovascular system: potential mechanisms impact of exposure measurement error in air pollution epidemiology: effect of error type in time-series studies clinical characteristics of coronavirus disease 2019 in china air pollution and airway disease early transmission dynamics in wuhan, china, of novel coronavirus-infected pneumonia association of public health interventions with the epidemiology of the covid-19 outbreak in wuhan, china short-term exposure to air pollution and lung function in the framingham heart study the national morbidity, mortality, and air pollution study. part ii: morbidity and mortality from air pollution in the united states estimating the exposure-response relationships between particulate matter and mortality within the aphea multicity project prevalence of comorbidities and its effects in patients infected with sars-cov-2: a systematic review and meta-analysis concentrations and size distributions of airborne influenza a viruses measured indoors at a health centre, a day-care centre and on aeroplanes this study was sponsored by the bill & melinda gates foundation (grant no. opp1216424). the authors declare no competing interests. key: cord-259325-2yl7kl7b authors: nakada, liane yuri kondo; urban, rodrigo custodio title: covid-19 pandemic: impacts on the air quality during the partial lockdown in são paulo state, brazil date: 2020-04-29 journal: sci total environ doi: 10.1016/j.scitotenv.2020.139087 sha: doc_id: 259325 cord_uid: 2yl7kl7b abstract in early march 2020, the world health organization declared the covid-19 as a pandemic, and in late march 2020 partial lockdown was ordered by the são paulo state government. the aim of this study was to assess impacts on air quality in são paulo – brazil, during the partial lockdown implemented to provide social distancing required due to the covid-19 pandemic. we have analyzed data from four air quality stations in são paulo, brazil to assess air pollutant concentration variations during the partial lockdown. data were compared to the five-year monthly mean and to the four-week before the partial lockdown. overall, drastic reductions on no (up to −77.3%), no2 (up to −54.3%), and co (up to −64.8%) concentrations were observed in the urban area during partial lockdown compared to the five-year monthly mean. by contrast, an increase of approximately 30% in ozone concentrations was observed in urban areas highly influenced by vehicle traffic, probably related to nitrogen monoxide decreases. although the partial lockdown has contributed to a positive impact on air quality, it is important to take into account the negative impacts on social aspects, considering the deaths caused by covid-19 and also the dramatic economic effects. j o u r n a l p r e -p r o o f on march 11, 2020, the world health organization (who) declared that the covid-19disease caused by the new coronavirus sars-cov-2 -had been characterized as a pandemic (who, 2020) . in brazil, the first case was confirmed on february 26, 2020, in são paulo -sp. to date (april 26, 2020) , there are 61,888 confirmed cases in all regions of brazil, most of the cases (20,715) confirmed in são paulo state (brazil, 2020) , being são paulo -sp, the city with most confirmed cases (13,513) (seade, 2020). on march 24, 2020, partial lockdown was ordered by são paulo state government (são paulo, 2020a) , closing shopping malls, restaurants, fitness centers, elementary, middle and high schools, and universities. supermarkets and drugstores started working with restrictions concerning person-to-person distance, and public transportation started working with reduced hours. since partial lockdown was first ordered, social isolation varied from 54% (march 24), achieving a minimum of 47% (april 09) and a maximum of 59% (several dates), with an average of 54% (são paulo, 2020b). the aim of this study was to assess impacts on air quality in são paulo, brazil, during the partial lockdown implemented to provide social distancing required due to the covid-19 pandemic. and 2019 were used to calculate the mean levels of each pollutant for each month, and therefore estimate a five-year monthly trend. similarly, data from february 25, 2020 to march 23, 2020 (four-week before partial lockdown) and from march 24, 2020 to april 20, 2020 (fourweek during partial lockdown) were used to calculate the mean levels of each pollutant both before and during the partial lockdown. furthermore, the variations in mean concentrations journal pre-proof j o u r n a l p r e -p r o o f 5 (μg•m ─3 , ppb or ppm) were calculated to assess relative change (%) comparing the partial lockdown period to the five-year monthly trend or to the four-week before partial lockdown. nitrogen dioxide (no 2 ) data obtained by remote sensing and provided by the copernicus sentinel-5 precursor tropospheric monitoring instrument (s5p/tropomi), developed by the european space agency (esa) was used to assess no 2 levels (tobías et al. 2020). brazil is currently in the autumn season, and thus under good conditions to pollutant dispersion. during winter season são paulo commonly faces the temperature inversion phenomena, when the air pollutants reach their peaks. meteorological monitoring data bulletin made available by the são paulo state environmental agency (cetesb, 2020) show that favorable conditions to pollutant dispersion were found both before partial lockdown (february 25 -march 23) and during partial lockdown (march 24 -april 20), therefore indicating that observed pollutant reductions were not highly determined by changes in dispersion conditions. before partial lockdown, in a few days (march 11 -17) adverse conditions to ozone dispersion were observed, and in the same period ozone peaks were detected. in the industrial area we observed low levels of variation when compared to the five-year monthly mean (2015-2019), and also concentration increases of all analyzed pollutants when compared to the period before the partial lockdown (table 1) . it is important to mention that the industry was not ordered to lockdown, albeit some industrial sectors have been affected by decreasing demand. in the urban area we observed significant air quality improvements considering decreases in air pollutants monitored in areas highly influenced by vehicle traffic (urban road i, urban road journal pre-proof j o u r n a l p r e -p r o o f 6 ii and city center) (table 1 and figure 1 ). high reductions of air pollutants concentration were found during partial lockdown compared to the five-year monthly mean (variation a), while significant reductions were found in comparison to the period before partial lockdown (variation b). drastic reductions on no (−48.6%, −77.3% and −72.7% in urban road i, urban road ii and city center, respectively), no 2 (−30.1%, −54.3% and −46.5% in urban road i, urban road ii and city center, respectively) and co (−36.1%, −53.1% and −64.8% in urban road i, urban road ii and city center, respectively) concentrations were observed in the urban area during partial lockdown compared to the five-year monthly mean. in são paulo -sp, road traffic accounts for approximately 68% of nox and 98% of co emissions (andrade et al. 2017) . one recent research has demonstrated that traffic emissions from heavy-duty diesel trucks are major sources of no (he et al. 2020) . during the partial lockdown, vehicle traffic considerably decreased in all analyzed areas, positively affecting the air quality. decreases in pollutant concentrations in urban road i were lower than in the other analyzed areas, probably because this urban road is the connecting route for several highways and also is the main route in são paulo. < air quality in the megacity of são paulo: evolution over the last 30 years and future perspectives ministry of health -covid19 -coronavirus panel qualar: air quality information system google earth engine: planetary-scale geospatial analysis for everyone. remote sensing environment on-road emission measurements of reactive nitrogen compounds from heavy-duty diesel trucks key: cord-302195-25gjbyi1 authors: al huraimel, khalid; alhosani, mohamed; kunhabdulla, shabana; stietiya, mohammed hashem title: sars-cov-2 in the environment: modes of transmission, early detection and potential role of pollutions date: 2020-07-15 journal: sci total environ doi: 10.1016/j.scitotenv.2020.140946 sha: doc_id: 302195 cord_uid: 25gjbyi1 abstract the coronavirus disease 2019 (covid-19) is spreading globally having a profound effect on lives of millions of people, causing worldwide economic disruption. curbing the spread of covid-19 and future pandemics may be accomplished through understanding the environmental context of severe acute respiratory syndrome coronavirus 2 (sars-cov-2) and adoption of effective detection tools and mitigation policies. this article aims to examine the latest investigations on sars-cov-2 plausible environmental transmission modes, employment of wastewater surveillance for early detection of covid-19, and elucidating the role of solid waste, water, and atmospheric quality on viral infectivity. transmission of sars-cov-2 via faecal-oral or bio-aerosols lacks robust evidence and remains debatable. however, improper disinfection and defected plumbing systems in indoor environments such as hospitals and high-rise towers may facilitate the transport of virus-laden droplets of wastewater causing infection. clinical and epidemiological studies are needed to present robust evidence that sars-cov-2 is transmissible via aerosols, though quantification of virus-laden aerosols at low concentrations presents a challenge. wastewater surveillance of sars-cov-2 can be an effective tool in early detection of outbreak and determination of covid-19 prevalence within a population, complementing clinical testing and providing decision makers guidance on restricting or relaxing movement. while poor air quality increases susceptibility to diseases, evidence for air pollution impact on covid-19 infectivity is not available as infections are dynamically changing worldwide. solid waste generated by households with infected individuals during the lockdown period may facilitate the spread of covid-19 via fomite transmission route but has received little attention from the scientific community. water bodies receiving raw sewage may pose risk of infection but this has not been investigated to date. overall, our understanding of the environmental perspective of sars-cov-2 is imperative to detecting outbreak and predicting pandemic severity, allowing us to be equipped with the right tools to curb any future pandemic. the outbreak of the novel coronavirus sars-cov-2 was reported in wuhan, china at the end of december 2019 where cases of pneumonia in people associated with the wet market had been confirmed as cases of the novel coronavirus (holshue et al., 2020) . shortly after, it was declared as a pandemic by the world health organization (who) with over 8.7 million covid-19 confirmed cases as of june 21,2020 (who situation report -153). the spread of the pandemic resulted in worldwide lockdowns in effort to "flatten the curve" and not overwhelm health care institutions (lau et al., 2020) . the key to interrupting the chain of transmission is isolating infected people and tracing back those who they have interacted with (khanna et al., 2020; larsen et al., 2020) . human-to-human transmission occurs during the virus incubation period of 2-10 days, with spread being facilitated through droplets, contaminated hands and surfaces (enyoh et al., 2020; kampf, 2020 ). an inter-personal distance of at least 2 m was prescribed to minimize the risk of contagion through the droplets (cdc, 2020; setti et al., 2020c) . numerous research articles have been recently published assessing the plausible modes of environmental transmission of sars-cov-2 and spread of covid-19 through environmental analysis. there is no conclusive evidence for aerosol or faecal-oral transmission of sars-cov-2 despite several researchers considering them as plausible routes that may explain the high infectivity and global spread of covid-19 (chen et al., 2020; van doremalen et al., 2020; wang et al., 2020a) . additionally, environmental parameters have been utilized to assess the spread of covid-19 within a population through wastewater surveillance as well as attempts to predict the severity of the pandemic through analysis of atmospheric pollution of cities. solid waste management is another aspect of paramount importance that may contribute to the spread of the pandemic within the community but that has not received much attention within the scientific community. only j o u r n a l p r e -p r o o f 5 two studies were found analyzing sars-cov-2 rna in natural water bodies receiving raw or treated sewage waters with differing results, and it is unclear if there is any risk of infection, particularly in recreational waters where people are in frequent contact (guerrero-latorre et al., 2020; odih et al., 2020; usman et al., 2020) . from the literature studied, concerns of covid-19 infection through environmental contact pertain mainly to areas that lack proper sanitation and wastewater treatment, lack adequate solid waste management infrastructure, in areas where raw sewage is discharged directly into natural water bodies, and in cities where air pollution is problematic. although there has not been any evidence presented that validates environmental transmission routes, the lack of sanitary and waste infrastructure is likely to increase the probability of human contact with contaminated material, the impact of which is yet to be investigated. the major mode of transmission of sars viruses is through exposure to droplets of respiratory secretions from an infected person (>5 µm), indirectly through fomite transmission from contact with contaminated objects, or possibly by faecal-oral routes and air borne transmission (wang et al., 2005; ye et al., 2016; kitajima et al., 2020; naddeo and liu, 2020) . faecal-oral routes and aerosol transmission have not been validated as exposure routes as there is not enough evidence to prove that sars-cov-2 transmission is possible by aerosol or wastewater. however, alarming infection incidents among health care workers, cruise-ship and airplane passengers point to the likelihood of additional transmission mechanisms in confined spaces with dense populations (nghiem et al., 2020) . wu et al. (2020b) agreed that potential faecal-oral transmission may pose risk in cruise ships, public transportation, hostels and dormitories but unlikely in hospitals or quarantine facilities. although grunig et al. (2020) concluded that fecal-oral transmission had likely played a role in amplifying the pandemic in wuhan (grunig et al. 2020) , the data is based on literature review of sars-cov not on research investigation. on that basis, it is plausible that sewage could serve as vectors for coronavirus (ye et al., 2016; zhang et al., 2020) . researchers have also postulated that the spread of covid-19 solely by respiratory droplets and close contact did not seem to explain the vast spread of the disease in various parts of the world such as italy, and thus air borne transmission has been investigated (setti et al., 2020c) . clearly, the alarming infection rate of sars-cov-2 may suggest several plausible transmission mechanisms. table 1 summarizes the latest research articles proposing various modes of sars-cov-2 transmission and arguments presented. journal pre-proof j o u r n a l p r e -p r o o f coronavirus rna has been detected in the stool of symptomatic and asymptomatic sars and covid-19 patients, indicating that transmission may be possible via the raw sewage network (faecal-oral) (wang et al., 2005; gundy et al., 2009; ahmed et al., 2020; holshue et al., 2020 ., wang et al., 2020a wolfel et al., 2020; wu et al., 2020b; zhang et al., 2020) . the incidence of diarrhea in sars cases raised concern about its potential environmental transmission where viruses are more stable in diarrheal stool due to the higher ph, reaching upto 4 days as opposed to 1-2 days for normal stool (gundy et al., 2009; sars epidemiology working group, 2003) . nevertheless, live sars-cov-2 was observed in stool of 2 patients who did not have diarrhea (wang et al., 2020a) . sars-cov can persist in sewage for 14 days at 4c and for 2 days at 20c, and its rna can be detected for 8 days. ( gundy et al. 2009; wang et al. 2005) . sars-cov rna was detected in 97% of stool samples from patients infected with sars (peiris et al., 2003) , while detected in 57% of samples in another study by he et al. (2004) . numerous researchers have attempted to assess whether sewage systems were plausible transmission pathways of coronavirus (barcelo et al., 2020; gormley et al., 2020) . it is unlikely for sars-cov-2 to be transmitted via wastewater or present any significant risk of infection due to viral sensitivity to disinfectants and poor stability in environmental conditions (randazzo et al. 2020b ); rimoldi et al., 2020) . coronaviruses are enveloped viruses that have a lipid bilayer membrane outside the viral protein capsid, which contains proteins or glycoproteins. the structural difference with nonenveloped viruses may have an impact on their survival in aqueous environments, where their lipid layers are sensitive to the detergents and organic solvents (ye et al., 2016) . gundy et al. (2009) found that coronavirus dies off very rapidly in wastewater, with a 99.9% reduction in 2-3 days due to action of solvents and detergents. thus, while genetic fragments remain detectable in wastewater, the j o u r n a l p r e -p r o o f virus likely becomes non-viable once the envelope is damaged (ye et al., 2016; nghiem et al., 2020) . at two hospitals receiving sars patients in beijing, china, sars-cov rna was detectable in concentrates of sewage prior to, and occasionally after disinfection by chlorine but there was no live sars-cov (wang et al., 2005) . sars-cov-2 was detected in faeces (wang et al., 2020a) and its rna was detected in both faeces and urine (sun et al., 2020; xiao et al., 2020) , while other attempts failed to cultivate the virus from faeces (woelfel et al., 2020) or treated wastewater (rimoldi et al., 2020) . raw sewage with improper disinfection in hospitals containing patients' excrements may be a possible transmission path (wang et al., 2005) . however, accidental contact with treated wastewater through aerosols or droplets should not call for public concern as potential risk of infection seems to be negligible (rimoldi et al., 2020) . contact with raw wastewater particularly in areas with poor sanitation may be potential routes of transmission posing risk of infection (grunig et al., 2020; lodder and husman, 2020; rimoldi et al., 2020) . in fact, contact with, and contamination by sewage water has been reported to be responsible for an outbreak of sars cov-1. the outbreak occurred in hong kong in 2003 involving 341 patients and 42 deaths due to a faulty wastewater plumbing system in a high-rise building (peiris et al., 2003) . the defected plumbing system facilitated the transport of virus laden droplets of wastewater originating in the bathroom pipelines to air ducts via the bathroom extraction ventilation (gormley et al., 2020) . gormley et al. (2017) presented evidence that pathogens can be aerosolized and transported on airstreams within sanitary plumbing systems from one part of a building to another on different floors. one important factor contributing to the travel of contaminated air throughout a building is the interconnectedness of building's plumbing system (gormley et al., 2020) . one study found that while toilets may generate a large number of aerosols, the total volume of aerosolized liquid was extremely small, indicating that the potential for inhalation was low. (lin and marr, 2017) . nevertheless, the possibility of infection by j o u r n a l p r e -p r o o f 9 contact with large splashing droplets has not been negated and requires further research (lin and marr, 2017) . heller et al. (2020) presented a framework to test the faecal-oral hypothesis, and proposed different environmental pathways of exposure from faeces to mouth: transmission by ingestion of a pathogen present in water, transmission by hand contact with surface washed with water containing pathogen, and transmission by excreta-related insect vectors. how long the novel sars-cov-2 can survive in wastewater and remain infectious is yet to be assessed (naddeo and liu, 2020) . aboubakr et al. (2020) reported that information on sars-cov-2 stability in excrements is important in elucidating their role in transmitting the disease and assessing the plausibility of a faecal-oral route. in addition to the impact of disinfection, survival of coronavirus in water depends on a number of factors, including temperature, light exposure (solar or uv inactivation), organic matter, total dissolved solids (tds), hardness, turbidity, ph, nitrate concentrations, and the presence of antagonist microorganisms (john and rose, 2005; naddeo and liu, 2020) . temperature is the most critical factor influencing survival of coronavirus where higher water temperatures decrease the virus survival rate due to denaturation of proteins and activity of extracellular enzymes (john and rose, 2005; gundy et al., 2009) . a 99.9% reduction of coronavirus was exhibited within 10 days in filtered tap water at room temperature, while over 100 days were required to reach that same level of virus inactivation for tap water at 4°c (gundy et al., 2009 ). coronavirus were found to be more susceptible to higher temperatures than nonenveloped viruses and more strongly associated with wastewater solids (gundy et al., 2009; ye et al., 2016) . the latter indicates that the primary treatment of wastewater and adsorption of coronavirus onto organic matter and suspended solids may provide protection against the virus (gundy et al., 2009; ye et al., 2016; rimoldi et al., 2020; wurtzer et al., 2020) . further j o u r n a l p r e -p r o o f 10 investigations are required to assess environmental conditions of wastewater that may impact sars-cov-2 viability. the question currently remains as to the possibility of sars-cov-2 transmission and spread by air, indoor or outdoor. one method by which that could take place is through transport of virus-laden particles in the air where very small droplets (<5 µm) are formed after the liquid content of respiratory secretions evaporates allowing their transport by air currents carrying the viral content (morawska and cao, 2020) . current knowledge indicates an unlikely probability in outdoor environments and an increase in probability under specific indoor environments, like hospitals and areas where patients are quarantined (contini and costabile, 2020; liu et al., 2020a,b) . tabula (2020) stressed that evidence is limited on sars-cov-2 transmission via airborne route contending that studies are conflicting, and that robust evidence is yet to be presented. the difficulty in validating sars-cov-2 aerosol transmission stems from difficulty in sampling virus-laden aerosols and quantification at low concentrations (liu et al., 2020b; morawska and cao, 2020) . aerosol transmission is currently a matter of intense debate and more studies are proposing it as plausible despite lack of robust evidence. aerosol generation was reported under specific medical procedures (such as endotracheal intubation, non-invasive positivepressure ventilation, etc) and aerosol transmission could be more probable route than faecalavoiding air recirculation should be implemented (morawska and cao, 2020; setti et al., 2020c) . effective measures in minimizing airborne sars-cov-2 included negative pressure ventilation and high air exchange rates as shown for intensive care and critical care units of renmin hospital in wuhan, china (liu et al., 2020a) . it is more difficult to validate aerosol transmission of sars-cov-2 in outdoor environments than in indoors. the probability of inhaling airborne viable virus generated from a distance and being infected is very low (contini and costabile, 2020). hospital settings for example host infected individuals occupying limited space with likely poor air exchange creating a favorable environment for virus survival and assessment of aerosol transmission (contini and costabile, 2020). liu et al. (2020a) detected sars-cov-2 aerosol at two outdoor crowd gatherings where asymptomatic carriers could pose potential source of airborne sars-cov-2 but stated that public venues pose low risk when avoiding crowded gatherings. the relationship between covid-19 and air quality can be viewed from various aspects. first, the lockdown procedures around the world have resulted in less anthropogenic activities and subsequent decreases in air pollution. from other aspects, the level of air pollution in a city may seem to influence the severity of covid-19, either due to health susceptibility of individuals living in polluted cities to covid-19 infection, or air pollution as a mode of transmission which is not supported by evidence despite being proposed by some researchers. there are numerous studies from around the globe showing significant decrease in ambient air pollution following lock down and quarantine measures to combat j o u r n a l p r e -p r o o f 13 covid-19. the overall air quality in northern china was improved during the control of covid-19 due to reduced emissions from transportation and industry (wang et al., 2020b) . a total of 322 of the 366 cities studied in northern china exhibited a decline in the air quality index (aqi) and reduction of pm 2.5 , pm 10 , so 2 , no 2 , and co (wang et al., 2020b) . similarly, sharma et al. (2020) reported a decline in aqi and reduction in concentrations of pollutants expect for so 2 when comparing march and april of 2020 with previous years. in these studies, it was reported that o 3 concentrations had increased during the covid-19 control period possibly due to reduction of pm concentrations causing more sunlight to pass through the atmosphere encouraging more higher o 3 production (sharma et al., 2020) . other researchers have reported that concentrations of pm 2.5 exhibited significant reduction in several cities in china, but not enough to avoid severe air pollution events during lockdown likely attributed to unfavorable meteorological conditions (wang et al., 2020c) . the decrease in air pollution may have reduced the number of non-communicable diseases and fatalities, where 6% reduction in mortality was postulated due to air pollution reduction, equivalent to saving 100,000 lives in china alone (dutheil et al., 2020) . air pollution has been linked to sars-cov-2 viral infections through the impact of poor air quality on human health and susceptibility to viral infection (wu et al., 2020c) , and evidence is not available for pollutant particles such as pm and no 2 acting as vectors despite suggested by some researchers (pansini and fanacca, 2020) . air pollution is known to cause inflammation, cellular damage, respiratory diseases and may suppress early immune response to infection (wu et al., 2020c) . for example, pm 10 and pm 2.5 have been linked to pneumonia and chronic pulmonary diseases (pansini and fornacca, 2020; wu et al., 2020c) . numerous investigations have attempted to assess the relationship between air pollution and severity of covid-19 around the world. some studies show that people living in polluted areas are more vulnerable to sars-cov-2 infections and induced mortality as they are more prone to developing chronic respiratory conditions (conticini et al., 2020; murgante et al., 2020; pansini and fornacca, 2020; zhu et al., 2020) . concentrations of pm exceeding limits may increase the susceptibility of covid-19 infected individuals to respiratory complications while oxidant pollutants may impair the efficiency of lungs to clear the virus (qu et al., 2020) . several studies have investigated exceedance of pm and its correlation with covid-19 infectivity and lethality. just small increases of long-term exposure to pm 2.5 (1 g/m 3 increase) was found to be associated with an 8% increase in the covid-19 death rate in the us (wu et al. 2020c similarly, the number of infected people was higher in italian cities with 100 days exceeding limits set for pm 10 or ozone, having a low wind speed and lower temperature (coccia, 2020). on the other hand, bontempi (2020) reported that direct correlations between high concentrations of pm 10 and diffusion of covid-19 virus in lombery and piedmont, italy were not evident. in particular, cities with highest pm 10 pollution (torino and alessandria) had low infections cases, while bergamo which exceeded pm 10 concentration only few times, exhibited the highest infectious cases (bontempi, 2020). like pm, several studies have linked viral infectivity to exceedances in the other criteria pollutants. sars-cov-2 viral infections in china, usa, and italy were found to be higher in areas afflicted by carbon monoxide (co) and nitrogen dioxide (no 2 ), while higher mortality rates were found to be in areas correlated j o u r n a l p r e -p r o o f 15 with high particulate matter (pm 2.5 ), co, and no 2 (pansini and fornacca, 2020) . zhu et al. (2020) observed positive associations of pm 2.5 , pm 10 , co, no 2 , and o 3 with covid-19 confirmed cases, and that short-term exposure to these pollutants is associated with increased risk of infection with covid-19. in terms of interpretation of how air pollution may enhance the spread of covid-19, there are several points of view based on reasoning rather than on robust evidence. several researchers view that the extent to which covid-19 has spread in many countries cannot be solely explained by just exposure to droplets of respiratory secretions from an infected person or through fomite transmission from contact with contaminated objects. setti et al. (2020b) postulated that through airborne transmission, pm could act as a droplet carrier, triggering the spread of the virus. however, the capability of this coronavirus to bind particulate matters remains to be established, but could be through adsorption (fattorini and regoli, 2020; qu et al., 2020) . air borne transmission of sars-cov-2 has been postulated by morawska and cao (2020) as explanation to the trend in the increase of infections, and that air transmission should be seriously considered during the course of this pandemic. under high pm concentration and atmospheric stability, viruses may create clusters with the pm reducing their diffusion coefficient and enhancing abundance into the atmosphere (setti et al., 2020c) . setti et al. (2020c) presents the first evidence of sars-cov-2 rna presence on outdoor pm through analysis of 34 pm 10 samples of outdoor/airborne pm 10 from an industrial site of bergamo province. however, correlation between the presence of virus on pm and covid-19 outbreak progression has not been confirmed in that study, and links between air pollutants and the pandemic has not been validated (setti et al., 2020c) . few review articles were found on coronavirus or sars-cov-2 in municipal solid waste materials while no experimental research articles were found. the reason maybe that sars-cov-2 infected waste is typically generated from medical centers and hospitals which are then incinerated. however, with the worldwide lockdown and self-quarantine measures, solid waste containing viable sars-cov-2 are likely generated at the household level from covid-19 infected individuals posing risk of infection to front line waste workers (nghiem et al., 2020) . in that regard, mol and caldas (2020) report that spread of the coronavirus may be increased by inadequate waste management through poor handling conditions particularly in developing countries with poor waste management strategies. kharel (2020) waste generated from households during the lockdown period. sars-cov-2 was also found to be more stable on plastic and stainless steel than on copper and cardboard and despite its high stability in favorable environments, it is nevertheless susceptible to standard disinfection methods (chin et al., 2020; van doremalen et al., 2020; kampf et al., 2020) . much of the information on sars-cov-2 persistence on solid surfaces is deduced from previous coronavirus studies ( aboubakr et al., 2020; kampf et al., 2020) . the limited available data on sars-cov-2 persistence on solid surfaces and solid waste materials calls for the need to elucidate solid waste and its management practices with covid-19 spread. it is important to understand the fate of sars-cov-2 in the water environment to ensure public health protection measures are suitably set in place (naddeo and liu, 2020) . however, there is currently limited data on the presence and viability of sars-cov-2 in water bodies (cahill and morris, 2020). aboubakr et al. (2020) presented a review of studies on persistence of coronaviruses in chlorinated and dechlorinated water, which may help to understand the persistence of sars-cov-2 in waters. sars-cov-2 in the water environment may find its origin in the discharge of raw sewage into water bodies which is common practice in many parts of the world, lack of basic sanitation resulting in contamination of drinking water sources, accidental contamination by raw sewage, or where performance of sewage treatment plants is sub optimal (guerrero-latorre et al., 2020; odih et al., 2020; usman et al., 2020) . guerrero-latorre et al., 2020 interim guidance, 2020), and contracting the virus via water sources is unknown and has not been investigated to date. the need to investigate is high particularly in developing countries with poor water and sewage infrastructure where the probability of faecal material reaching natural water bodies is high. there is also no evidence of potential aerosolized sars-cov-2 originating from wastewater used for irrigation (usman et al., 2020) . with research progress, the implications of research findings on sars-cov-2 in the water environment will assist public health officials in devising the proper mechanisms to protect the general public. there are a lot of aspects to be taken care of starting from the disinfection at the source, proper distribution, collection and safe practices for storage. conventional treatment systems like chlorination and uv disinfection are expected to remediate covid-19 presence in water systems similar to other coronaviruses (pecson et al., 2020; who, interim guidance, 2020) . since wastewater contains viruses excreted from infected individuals in a given wastewater treatment plant catchment population, wastewater surveillance and quantification of sars cov-2 can be an effective tool in estimating the number of infections in a community at an early stage of the outbreak (ahmed et al., 2020; mallapaty, 2020; wu et al., 2020a) . the early detection and determination of sars-cov-2 prevalence in a population can assist policy makers in formulating the appropriate mitigation policies and help to ensure healthcare institutions are not overwhelmed (mao et al. 2020; wu et al., 2020a) . sars-cov-2 rna is detected in wastewater using real-time reverse-transcriptase-polymerase-chain-reaction testing (rt-qpcr) (lodder and husman, 2020; mao et al., 2020; randazzo et al., 2020b) . wastewater rt-qpcr was reported to be a sensitive and reliable technique for early detection of sars-cov-2 outbreaks (randazzo et al., 2020b) . it is important to note that rna detection in wastewater is not indicative of viable virus that is transmissible (nghiem et al., 2020; who scientific brief, 2020) . genetic material of sars-cov-2 has already been j o u r n a l p r e -p r o o f detected in wastewater samples from the region of valencia, spain (randazzo et al., 2020a) , amsterdam airport schiphol, netherlands (lodder and de roda husman, 2020) , australia (ahmed et al., 2020) , massachusetts, usa (wu et al., 2020a) , france (wurtzer et al., 2020) , milan, italy (la rosa et al., 2020; rimoldi et al., 2020) , istanbul, turkey (kocamemi et al., 2020) and china (wang et al., 2020d) . the fact that wastewater samples at amsterdam airport schiphol and in tilburg, netherlands tested positive for viral rna by quantitative rt-pcr methodology only days after the confirmed cases of covid-19 in the country shows the sensitivity of this surveillance system and how it can serve as an early warning tool (lodder and de roda husman, 2020) . randazzo et al. (2020 a,b) reported detection of sars-cov-2 rna in wastewater when only 50-76 cases were reported in valencia and 12-16 days before covid-19 cases were declared in 3 out of 6 municipalities in spain. however, there is a lack of standardized protocol for the detection of sars-cov-2 in wastewater with discrepancies among rt-qpcr n1, n2 and n3 assays. massive population tests should be the first choice but wastewater monitorization may provide a reliable picture of the situation (kitajima et al., 2020; randazzo et al., 2020b) . wastewater surveillance may serve as a complementary approach to clinical testing campaigns for assessing the prevalence of covid-19 in a community (wu et al., 2020a) . one wastewater treatment plant can capture wastewater from more than a million residents, providing an estimate of the prevalence of covid-19 within a large population (mallapaty, 2020) . wastewater-based epidemiology (wbe) has some benefits over clinical testing particularly for poor nations with limited resources and the fact it may serve as an early detection tool, but cannot fully replace clinical testing which should be considered as the first choice (hart and halden, 2020; randazzo et al., 2020b) . clinical screening comes with the challenges of undertaking a massive, time-consuming, and labor-intensive process constrained by availability of testing technologies (mao et al., 2020) . wastewater j o u r n a l p r e -p r o o f 20 surveillance on the other hand can account for individuals who have not been tested, or are asymptomatic, potentially symptomatic, presymptomatic, or only have mild symptoms (lodder and de roda husman, 2020; mallapaty, 2020) . additionally, different clinical diagnostic testing methods and assays makes country comparisons difficult (kitajima et al., 2020) . the importance of wbe is also highlighted by its ability to detect low levels of viruses, especially important at early stages of an outbreak or when infection levels are decreasing following intervention (kitajima et al., 2020) . monitoring programs for coronavirus in wastewater treatment plants should be established to assess their fate during water and wastewater treatment (naddeo and liu, 2020) . researchers can determine the abundance of covid-19 in a population from wastewater samples by how much viral rna is excreted in faeces and extrapolate the number of infected people from concentrations of viral rna in wastewater (mallapaty, 2020) . sars-cov-2 rna is first concentrated from wastewater, viral rna copies are enumerated using rt-qpcr, and the estimated rna copy numbers are then used to estimate the number of (ahmed et al., 2020; kitajima et al., 2020) . the reasons for the discrepancy between confirmed cases and observed viral titers could be due to inaccurate assumptions of viral load in stool or loss assumptions in viral titer due to degradation, and presence of asymptomatic patients (wu et al., 2020a) . there is lack of a standardized protocol for the based on this presented review of covid-19 infectivity and relation to environmental factors, strategies may be adopted to combat future pandemic by ability to assess its distribution and spread from environmental indicators. there is need for development of a standardized protocol for quantification of sars-cov-2 in wastewater and overcoming existing challenges discussed previously (kitajima et al., 2020) . wastewater surveillance may then serve as an important and quick tool to determining the spread of covid-19 within a community and can assist policy makers in j o u r n a l p r e -p r o o f 22 early detection of outbreak through analysis of sars-cov-2 rna in wastewater samples. the information obtained can assist in identifying areas where transmission is occurring (kitajima et al., 2020; larsen et al., 2020) , provide guidance on when to relax restrictions on population movement (nghiem et al., 2020) , assists in containing the pandemic once the curve is flattened, and helps to prevent escalation where infections are minimal (larsen et al., 2020) . from our limited understanding of atmospheric pollution impact on covid-19 spread and severity, integration of air quality protection and climate change mitigation within nations' sustainable development strategies may assist in curbing future viral outbreaks (fattorini and regoli, 2020; pansini and fornacca, 2020; wu et al., 2020c) . there is emphasized importance on continued enforcement of air pollution regulations to protect health during and after this pandemic as well as in the event of future outbreaks (wu et al., 2020c) . the pandemic is ongoing and the status of infections in the world is dynamically changing. thus, the links between air pollution and covid-19 infectivity and lethality are not established at this stage. any future development in that regard may serve as a tool for policy makers in setting proactive strategies to face future pandemics. for example, if future robust evidence is made available linking air pollution to covid-19 spread, then it may actually be plausible to predict pandemic impacts based on the number of days cities exceed pollutant limits (coccia, 2020). governments would be then able to prioritize regions with high pollutant concentrations and take proactive action to reduce atmospheric pollution. in terms of protection against spread of viral infectivity in indoor environments, attention should be given to building design that ensures increased ventilation rates, natural ventilation, proper air circulation, as well-engineered sanitary plumbing systems that minimize the potential for virus-laden aerosol to spread within the building (gormley et al., 2020; liu et al., 2020a; j o u r n a l p r e -p r o o f limited, further investigations are needed to devise methodologies for sampling and quantification of sars-cov-2 in aerosols (liu et al., 2020a; morawska and cao, 2020) . despite limited research on sars-cov-2 in municipal solid waste, the best waste management strategies should be implemented to limit workers' exposure to waste contaminated with viable virus, likely generated by households with symptomatic and nonsymptomatic individuals. practices may include separate collection services for infected households, delaying waste collection beyond the lifespan of the virus (72 hours), and direct transport of collected waste to incinerators or landfills avoiding waste segregation at material recovery facilities (nghiem et al., 2020) . there are limitations to our current understanding of the environmental transmission of sars-cov-2 and links between environmental pollution and covid-19 infectivity and spread. the research is moving at quick pace and the changing dynamics of infections worldwide presents its challenges to establishing robust evidence linking environmental conditions such as air pollution with covid-19 infections. experimental research on validation of faecal-oral and aerosol transmission of sars-cov-2 is also met with challenges, where robust evidence is yet to be presented through in-depth research efforts. other areas of environmental research have not received attention such as covid-19 transmission in solid waste. several of the presented articles are pre-prints undergoing peerreview, which limits comparison of evidence with other published research. there needs to be caution in interpreting the existing findings and the results presented herein is a snapshot of the current understanding of the environmental related aspects of sars-cov-2. j o u r n a l p r e -p r o o f knowledge on sars-cov-2 within the environmental context maybe beneficial in establishing effective policies for mitigating the transmission of the disease and combating future pandemics. early detection of covid-19 and prevalence within a population can be achieved through surveillance of sars-cov-2 rna in wastewaters, aiding decision makers in choosing the right times for tightening or relaxation of restrictions among other measures. should future robust evidence be available on links between atmospheric pollution and covid-19 spread, air quality maybe another tool of importance that can be employed to assess infectivity of covid-19 and future infections. this may allow policy makers to establish proactive strategies to face future pandemics, prioritizing regions with high atmospheric pollution. since air pollution mitigation actions during a viral outbreak may be of limited effectiveness, long-term strategies for air quality protection and regulatory enforcement are of major importance. evidence is needed to validate transmission of sars-cov-2 via faecal-oral or aerosol pathways, which would immensely help our understanding on the infectivity and vast spread of the pandemic. prevention of viral outbreak or spread within indoor environments such as hospitals or high-rise buildings due to circulation of virus-laden aerosol may be achieved by ensuring well-engineered sanitary plumbing systems and adequate air ventilation. solid waste management and impact on covid-19 spread has received little attention and there is need to assess the spread of the pandemic through waste materials specially in developing nations where inadequate practices may act to promote the spread of the pandemic within communities. research is also needed to assess the impact of raw sewage discharge into water bodies, a topic that has received little attention. overall, our understanding of the environment perspective of sars-cov-2 may help in detecting viral outbreak at early stages and assessing pandemic severity in effort to be equipped with the right tools to curb any future pandemic. j o u r n a l p r e -p r o o f mol and caldas (2020); nghiem et al. (2020) fomite (transmission via solid waste handling) wang et al. (2020b) possibility of faecaloral routes detected live sars-cov-2 in faeces, suggesting possible faecal oral transmission. information on how frequently viable virus is present in patient stool and the range of viral loads were not present. xu et al. (2020) plausible faecal-oral transmission rectal swab was tested positive with sars-cov-2 rna persistently when negative nasopharyngeal tests were found. evidence of replication-competent virus in faecal swabs was not present. randazzo et al. (2020b) unlikely faecaloral (wastewater) disinfection effect is likely to inactivate sars-cov-2. review studies postulating that presence of sars-cov-2 in sewage and stool could lead to possible faecal-oral transmission via aerosolization from toilet flushing, leaky plumbing system etc., similar to sars-cov. van doremalen et al. aerosolization from defective plumbing system with wastewater containing viral load due to interconnectedness of all parts of the building by the wastewater plumbing system. setti et al. (2020b) aerosol/air borne transmission detection of sars-cov-2 rna on particulate matter. morawska et al. (2020) review study postulating the aerosol transmission based on researches on sars-cov-2 similarity with sars-cov, droplet dynamics and airflow in buildings. santarpia et al. 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of sars-cov-2 viral rna in faecal samples evaluation of lockdown impact on sars-cov-2 dynamics through viral genome quantification in paris wastewaters evidence for gastrointestinal infection of sars-cov-2 characteristics of pediatric sars-cov-2 infection and potential evidence for persistent fecal viral shedding survivability, partitioning, and recovery of enveloped viruses in untreated municipal wastewater association between short-term exposure to air pollution and covid-19 infection: evidence from china isolation of 2019-ncov from a stool specimen of a laboratory the authors for the submitted manuscript "sars-cov-2 in the environment: modes of transmission, early detection and potential role of pollution" certify that they have no affiliations with or involvement in any organization or entity with any financial interest (such as honoraria; educational grants; participation in speakers' bureaus; membership, employment, consultancies, stock ownership, or other equity interest; and expert testimony or patent-licensing arrangements), or nonfinancial interest (such as personal or professional relationships, affiliations, knowledge or beliefs) in the subject matter or materials discussed in this manuscript. key: cord-350919-by4zwniq authors: chowdhuri, indrajit; pal, subodh chandra; saha, asish; chakrabortty, rabin; ghosh, manoranjan; roy, paramita title: significant decrease of lightning activities during covid-19 lockdown period over kolkata megacity in india date: 2020-07-28 journal: sci total environ doi: 10.1016/j.scitotenv.2020.141321 sha: doc_id: 350919 cord_uid: by4zwniq abstract the outbreak of covid-19 has now created the largest pandemic and the world health organization (who) has declared social distancing as the key precaution to confront such type of infections. most of the countries have taken protective measures by the nationwide lockdown. the purpose of this study is to understand the effect of lockdown on air pollutants and to analyze pre-monsoon (april and may) cloud-to-ground and inter-cloud lightning activity in relation to air pollutants i.e. suspended particulate matter (pm10), nitrogen dioxides (no2) sulfur dioxide (so2), ozone (o3) and aerosol concentration (ac) in a polluted tropical urban megacities like kolkata. after the strict lockdown the pollutants rate has reduced by more than 40% from the pre-lockdown period in the kolkata megacity. so, decreases of pm10, no2, so2, o3 and ac have a greater effect on cloud lightning flashes in the pre-monsoon period. in the previous year (2019), the pre-monsoon average result shows a strong positive relation between the lightning and air pollutants; pm10 (r2 = 0.63), no2 (r2 = 0.63), so2 (r2 = 0.76), o3 (r2 = 0.68) and ac (r2 = 0.83). the association was relatively low during the lock-down period (pre-monsoon 2020) and the r2 values were 0.62, 0.60, 0.71, 0.64 and 0.80 respectively. another thing is that the pre-monsoon (2020) lightning strikes decreased by 49.16% compared to the average of previous years (2010 to 2019). the overall study shows that the reduction of surface pollution in the thunderstorm environment is strongly related to the reduction of lightning activity where pm10 and ac are the key pollutants in the kolkata megacity. j o u r n a l p r e -p r o o f governments of india and west bengal have implemented strict measures, such as the closure of shops, supermarkets, malls, all industries, public transport, airports, etc. there is also some relaxation after lockdown 3.0 (after 3 may 2020), with the exception of the red zone of infection with covid-19. due to the social distancing prevention, some researchers (kerimray et al., 2020; li et al., 2020) reported air quality improvements associated with lockdown measures like consequent decrease of vehicle and industrial transit. the improvement of air quality and the reduction of air pollutants have a broad effect on large urban areas or megacities. the worldwide research has also proved that due the lockdown, air and water quality has also been improved (yunus et al., 2020) . sharma et al. (2020) analyzed data on air pollutants and assessed the impact of the lockdown on air quality in different parts of india. during the partial lockdown, the air quality of sao paulo in brazil improved dramatically and the level of pollutants decreased by 77% (nakada and urban, 2020) . the national capital region (delhi) in india is india's most polluted megacity, but the covid-19 pandemic lockdown suddenly reduced the concentration of air pollutants and significantly improved air quality after three days of lockdown (mahato et al., 2020) . as a result, many researchers (mahato et al., 2020; mandal and pal, 2020; yunus et al., 2020) have carried out the covid-19 pandemic lockdown on environmental quality, such as air, water and noise quality, in different parts of the world. however, due to the decline in air pollutants, some micro-climatic phenomena have also changed where the levels of air pollutants have changed dramatically, as lightning and thunderstorms are among them. j o u r n a l p r e -p r o o f positive charge of super-cooled cloud droplets and a negative charge of soft hail or snow pellets. the super-cooled cloud droplets move upward, positioned in the upper part of the cloud, and the soft hail in the middle or lower part of the cloud (ogawa and brook, 1964) . thus, the positive charge accumulated in the upper part of the thunderstorm cloud and the middle and lower parts of the cloud are accumulated by negative charges and their electrostatic discharge is generated by a massive lightning (lhermitte and williams, 1985) . many scientists have shown that the change in major weather conditions caused the urban effect (orville et al., 2001; soriano et al., 2001) . a large number of literature (chaudhuri and middey, 2013; kar et al., 2009; kar and liou, 2014) has shown that there is a strong relationship between the air pollutant and the lightning in the highly polluted megacity of the tropical region. different studies have shown that the increase in cloud-to-ground and intercloud lightning has an effect on nitrate oxide and o 3 in urban atmospheres (pawar et al., 2012) . air pollution, therefore, has a direct and indirect impact on the global climate and atmosphere. concentration of aerosols in the atmosphere has an effect on rainfall and cloud formation and has worked as a change in weather conditions. suspended particulate materials (pm 10 ) are the most important air pollutants and cloud lightning determinants (naccarato et al., 2003) . possible concentration of so 2 in the atmosphere to increase lightning flashes in urban areas (soriano and de pablo, 2002) . kar et al., (2009) reported that the major concentration of pm 10 and so 2 in the atmosphere is responsible for the hike of lightning strikes. on the other hand, the concentration of no 2 on the troposphere has a major effect on j o u r n a l p r e -p r o o f although different studies have included a lockdown impact on improving air quality in urban areas, changes in air quality and air pollutants and the impact on the climate of microregions such as megacities have not yet been discussed. this means that the covid-19 lockdown imposed has an indirect impact on the micro-climate phenomenon. the present study has been conducted considering the ambient air pollutants, i.e., pm 10 , no 2 , so 2 , o 3 and aerosol on lightning flashes during the pre-monsoon period (april and may). a higher amount of pre-monsoon lightning flash is reported over the kolkata megacity area than the monsoon period (chaudhuri and middey, 2013) . hence, the pre-monsoon season has been selected for this study because this time coincides with the covid-19 lockdown period. the main objectives of this study are therefore to analyze the trend of ambient air pollutants (pm 10 , no 2 , so 2 , o 3 and aerosol) during the lockdown and pre-lockdown periods. and to compare the pre-monsoon cloud-lightning activities affecting these air pollutants during the covid-19 lockdown period and some pre-lockdown periods in the kolkata megacity area. the location of the study is the kolkata megacity, the capital city of west bengal, as well as the largest megacity in eastern india (fig. 1) . physiographically, it is situated over the indo-gangetic plain specifically the mature part of the ganges delta. the average altitude of kolkata and its environs is 6.05 m with salty marshy wetland topography; after the implementation of the wetland restoration project, it is found especially towards the eastern parts of the megacity. the climate is tropical wet and dry ('aw' type of kopen classification), characterized by wet in summer and dry in winter. the mean annual temperature and rainfall are 26°c and 1,582 mm respectively. the megacity faces five seasons, i.e., pre-monsoon (apr-may), monsoon (june-sep), post-monsoon (oct-nov), winter (dec-jan) and spring (feb-mar). during the pre-monsoon period, this area experienced several local storms, characterized by strong winds and afternoon rains with j o u r n a l p r e -p r o o f thunderstorms and lightning. the monthly average temperature of pre-monsoon season is 30°c to 38°c and rainfall ranges from 0 to 150mm. the rainfall mainly occurs due to the nor-waster and severs tropical cyclone over the bay of bengal. the wind blows in the north, north-east, south and south-east direction during the pre-monsoon period. as per records of the census of india and government of west bengal, huge urbanization took place around the kolkata and the population of megacity has touched 14.85 million. kolkata is the main commercial hub of eastern india, and a number of macro and micro industries are located here. so pollution is the main problem in kolkata, mainly air pollution, pm and other air pollutants are higher than other major cities in india. it caused respiratory diseases, such as lung cancer, (cpcb, 2020). most of the lightning studies were conducted in kolkata during the pre-monsoon season (april-may). this study period is therefore 24 march to 20 may, which is the period of (fig. 4) . the normal trend method used to compare both air pollutants and lightning flash counts for the period 2010 to 2020 (pre-monsoon period). the mann-kendall statistical s test calculated as following eq.1 (kendall, 1975; mann, 1945 ). (1) here, and are rank of observation in and time series. mann (1945) and kendall (1975) have reported that statistics s and the mean and variance are computed as eq.3. j o u r n a l p r e -p r o o f where, n is the number of observations, m is the number of groups of tied ranks and the notation t is extend of any given time. when the n >10 the standard normal variable (z) is computed as following eq.4. the slope estimates of n datasets were computed by the following equations (sen, 1968 ). where, and are the value of data at the time j and k ( > ), respectively. the median of slope or sen's slope estimator of odd and even data is computed as eq.6 and 7 where, is median of data trend. eq.6 applied if n is odd data and if n is even eq.7 is used. when the median slope is statistically different than zero, then confidence interval of at specific probability (da silva et al., 2015; gilbert, 1987 ) estimated as eq.8 from the pre-lockdown to during lockdown period and the trend of daily pm 10 decreases by -1.00μg/m 3 during the lockdown period (table 1 and 2). the pm 10 sources, such as vehicles and traffic, are very low on the roads and the industries have been tightly closed to maintain the social distance in kolkata during the lockdown. other important pollutants, i.e. no 2 and so 2 have also shown the significant reduction during the covid-19 pandemic lockdown ( fig. 2) . in the study area, average concentrations of no 2 and so 2 decreased by almost -68.38% and -40.38% respectively, and the trend of daily reduction is about -0.373 and -0.153μg/m 3 from the pre-lockdown to lockdown (fig. 2 , table 1 and 2) due to the emission from diesel, in smaller degree from gasoline vehicles, manufacturing industry and power plants have totally stopped. o 3 in the lower troposphere acts as a pollutant and potential for respiratory hazards. therefore, the concentration of o 3 is also much below the permissible limit and also has reducing trend (-42.58%) from pre-lockdown to lockdown, with a daily trend of -0.571μg/m 3 /day (fig. 2 , table 1 and 2). the concentrations of aerosol extracted from daily modis data during the pre-locking period to the lock-down period also show the same trend as for other pollutants (-57.92%) from the pre-and during the lock-down period and a daily decrease of -1.099μg/m 3 /day (fig. 2 , table 1 thereafter the above mentioned pollutants and aerosol concentration are minutely increases in the present phase of the lockdown period (fig. 2) . here table 1 here table 2 here current research corresponded to pre-monsoon thunderstorm and lightning activity during the previous studies have shown that sulfuric acid (h 2 so 4 ) particle is more active in the formation of new cloud condensation nuclei (ccn) as well as thunderstorm and lightning (perry and hobbs, 1994; siingh et al., 2011; thornton et al., 1997) . the reaction of so 2 with hydroxyl radical (oh) formed h 2 so 4 in the atmosphere. the formation of h 2 so 4 is shown in equations 9, 10 and 11 as follows. j o u r n a l p r e -p r o o f 2 + 2 → 2 + 3 (10) 3 + 2 → 2 4 (11) scatter plot (r 2 value of 2019 is 0.76 and 2020 is 0.71) revealed that higher so 2 concentration is associated with high lightning and flashing in kolkata, but the scatter distribution and ten-years trend showed a reduction in so 2 and lightning both during the 2020 lockdown period (fig. 3. the impact of the lock-down and its associated level of pollutants has been estimated in this study to determine the relationship between the level of pollutants and cloud flashes. for this purpose, the pre-monsoon season in the present and previous years has been selected purposively. the atmospheric disturbances have been found in this region and associated surrounding regions, popularly known as "kalbaisakhi" or "norwester". pollution in urban areas has a significant impact on the generation of lightning flashes and their associated frequency and intensity. although the kolkata megacity was considered to be one of the major polluted megacity due to rapid commercial, industrial and transport activities, heavy lightning flashes with high vertical air currents are common in any pre-monsoon season. apart from the various meteorological components, the suspended particulate matter (spm) has a major impact on surface lightning flashes during the pre-monsoon period. the global pandemic of the covid-19 lockdown has changed india's air quality. all cities in india are witnessing a downward trend in pollutants. this is primarily due to fewer automobiles and roadside food vendors using coal stoves, which is the significant source of emissions in indian cities. there is a significant decrease in the tendency of lightning flashes has been observed during the lockdown period of the kolkata megacity and its associated regions (fig. 3 ). however, the covid-19 lockdown reduces the level of air pollutants by closing down man-made sources of emissions. on the other hand, major air pollutants, nitrate oxides and j o u r n a l p r e -p r o o f aerosol concentration -6.86 *** -1.099 ***, **, and * are the significant at 1%, 5%, and 10% level of significance respectively. j o u r n a l p r e -p r o o f effect of lockdown amid covid-19 pandemic on air quality of the megacity delhi covid-19 pandemic persuaded lockdown effects on environment over stone quarrying and crushing areas nonparametric tests against trend voltages inside and just above thunderstorms evidence of thermal and aerosol effects on the cloud-to-ground lightning density and polarity over large urban areas of southeastern brazil covid-19 pandemic: impacts on the air quality during the partial lockdown in são paulo state, brazil. science of the total environment the mechanism of the intracloud lightning discharge effect of lightning activity on surface nox and o3 over a tropical station during premonsoon and monsoon seasons further evidence for particle nucleation in clear air adjacent to marine cumulus clouds nitrogen oxides from thunderstorms-results from experiments over estimates of the regression coefficient based on kendall's tau effect of restricted emissions during covid-19 on air quality in india solar activity, lightning and climate effect of small urban areas in central spain on the enhancement of cloud-to-ground lightning activity relationship between convective precipitation and cloud-to-ground lightning in the iberian peninsula. monthly weather review 129, j o u r n a l p r e -p r o o f particle formation lightning flash density in relation to aerosol over nanjing (china) observational evidence of aerosol enhancement of lightning activity and convective invigoration: aerosol enhancement of lightning covid-19 and surface water quality: improved lake water quality during the lockdown key: cord-338189-j4hnldk4 authors: saadat, saeida; rawtani, deepak; hussain, chaudhery mustansar title: environmental perspective of covid-19 date: 2020-08-01 journal: sci total environ doi: 10.1016/j.scitotenv.2020.138870 sha: doc_id: 338189 cord_uid: j4hnldk4 the outbreak of covid-19 has caused concerns globally. on 30 january who has declared it as a global health emergency. the easy spread of this virus made people to wear a mask as precautionary route, use gloves and hand sanitizer on a daily basis that resulted in generation of a massive amount of medical wastes in the environment. millions of people have been put on lockdown in order to reduce the transmission of the virus. this epidemic has also changed the people's life style; caused extensive job losses and threatened the sustenance of millions of people, as businesses have shut down to control the spread of virus. all over the world, flights have been canceled and transport systems have been closed. overall, the economic activities have been stopped and stock markets dropped along with the falling carbon emission. however, the lock down of the covid-19 pandemic caused the air quality in many cities across the globe to improve and drop in water pollutions in some parts of the world. on late december 2019 in a hospital in wuhan city, in china an unusual pneumonia was noticed with a link to an animal market that sells poultry, fish and other animals to the public (xu et al., 2020) . this event was soon reported to the world health organization (who). in a month (26 january), the causal microorganism had been identified as a novel coronavirus that was named covid-19. genome sequencing and reverse transcription polymerase chain reactions tests of this virus had been done. who r&d had been started to quicken diagnostics, therapeutics and vaccine development and a candidate vaccine was prepared for initial laboratory testing . the emergency committee of who declared a global health emergency on 30 january 2020 based of growing case notification rates at chines and international locations. the case detection rate is changing on a daily basis and could be tracked in nearly real time on the developed website by johns hopkins university and other media. in the middle of february 2020, china suffered the huge burden of morbidity and mortality, whereas the incidence in other asian countries, in europe and north america remains low so far (velavan and meyer, 2020) . coronaviruses are single-stranded rna viruses that can infect not only humans, but also a huge variety of animals as well (kooraki et al., 2020) . these viruses were first studied by tyrell and bynoe in 1966 who cultured them from patients with common cold. due to their spherical virions morphology along with a shell and surface projections like a solar corona, these viruses were named coronaviruses. in latin corona means crown and there are four different subfamilies including alpha, beta, gamma and delta coronaviruses identified so far. alpha and beta-coronaviruses have been originated from mammalians, particularly from bats, gamma-and delta-coronaviruses originated from pigs and birds (ather et al., 2020) . the genome of these viruses differs between 26 kb and 32 kb. the beta-coronaviruses could cause severe disease and fatalities among the other seven subtypes of these viruses. alpha-coronaviruses cause mildly symptomatic or even asymptomatic infections. sarscov-2 is a beta-coronavirus and is related to the sars-cov virus. there are four structural genes encoding the nucleocapsid protein (n), the spike protein (s), a small membrane protein (sm) and the membrane glycoprotein (m) with an extra membrane glycoprotein (he) occurring in the hcov-oc43 and hku1 betacoronaviruses. the whole genome of sars-cov-2 is 96% identical to that of a bat coronavirus cao et al., 2020) . sars-cov-2 seemingly had made its transition from animals on an animal market in wuhan city in china. although, the efforts to identify potential intermediate hosts seem to have been neglected in wuhan and the exact transmission route have to be clarified. the primary clinical symptoms of the sars-cov-2-linked disease covid-19 which permitted the case detection as pneumonia. recently literatures report the description of gastrointestinal symptoms and asymptomatic infections, especially among young children. the average incubation period is ranging from 0 to 24 days zhou et al., 2020) . as we are writing these lines, the pandemic affects 200 countries and territories, with around 1,357,382 infected subjects, more than 120, 438 deaths and 456.773 recovered patients, according to the johns hopkins university. as who has declared the fast spreading of covid-19 as an epidemic, the citizens around the globe hastened to go home. for instance, in the case of wuhan city in china which has been the epicenter of the pandemic with over than 11 million people, is shown to have produced 200 tons of clinical trash on a single day exactly 24 february/2020 which is four times the amount the city's only dedicated facility can incinerate per day. as coronavirus is spreading rapidly to other parts of the world, very soon the medical waste management could be a big issue. medical health organizations waste management companies have already taken step in coronavirus decontamination services, it is becoming very crucial for governments to find solutions soon. at the meantime, it is every individual's duty to follow the regulations while discarding of their face masks and other medical wastes (luan and ching, 2020) . to the end, it is possible only by mutual understanding and willingness and world will emerge stronger than this epidemic. some people are at higher risk of adverse effects from contact to medical wastes as well, including cleaners, trash collectors and some other people who have to spend a great amount of time in public places. all over the world governments stopped students to go to schools and universities, and a lot of employees are being asked to work from home, only those who are maintaining the cleanliness of cities have to go to their jobs daily, that makes them among the most vulnerable groups and one that is highly susceptible to the virus from respiratory shed droplets on the masks. they may also be infected by other pathogens existing in the discarded pieces of garbage, for instance meningitis and hepatitis b. the masks are made up of plastic based materials that are liquid-resistant and are long lasting after they are discarded, ending up in ocean or landfill. the surgical masks should not be worn longer than one day, discarding them and empty bottles of hand sanitizer along with solid tissue papers are ending up to a huge trail of medical waste in the environment. for instance, in hong kong, where covid-19 infection started in late january/2020 the medical wastes have already polluted the environment. recently, an environmental ngo ocean asia in soko islands took a survey, according to it, in hong kong a large amount of discarded single-use masks washed up to a 100-meter stretch of beach. gary stokes the director of the ocean asia ngo, who has been monitoring the ocean surface trash, his team has seen a few masks over the years, but now they were spotted all along the high tide line and seashore with new deposits coming with each current. while this recent covid-19 outbreak, the general public have started wearing surgical masks in order to take precautionary measures. when 7 million people suddenly start wearing one or a couple of masks daily, single use gloves and hand sanitizers, the amount of trash created is going to be substantial. the contrary impacts of such medical wastes are far-reaching. when these are remained discarded in an animal's natural habitat in both land and ocean this could cause animals to mistakenly eat this as food and lead in their death (hellewell et al., 2020) . the diagram below illustrates the problems of polluting the environment by medical wastes while covid-19 pandemic (fig. 1 ). covid-19 does not affect everyone in the same way. there are several reasons that's why different socioeconomic groups are affected by this pandemic in different ways. to understand the consequences, and to predict how this pandemic affects differently with various socioeconomic groups is not easy and good data is the key to it. these socioeconomic factors include population density, urban and rural settings, education level, lifestyle, the size of household and homeowners & tenants. sometimes only a single block distance neighborhood household within the socioeconomic spectrum can make a huge difference in one's life (demonstrate form the us in club vita's us longevity map). therefore, sometimes it is very unfortunate that people who are feeling the effects of covid-19 very severely, are probably in your neighbors (messner, 2020) . majority of the countries are now trying different tactics to stop the spreading of the disease and trying to limit only a subset of the people would catch the disease. it has been indicated that groups with lower socioeconomic status could be more at danger from the spread of the covid-19, based on the analysis of new york showing that poor neighborhoods have been affected highly. covid-19 spreads by droplets shed of the respiratory system by someone with the virus, which means it would spread with higher proximity of people, larger contact networks and lower levels of hygiene. there are some factors, which increase the risk of catching the virus. 1-population density: close contact among people is very high in urban areas rather than rural areas. 2-household size: a big household will have a higher chance to bring the virus home, while in household where one person lives alone; he/she will have to catch the virus outside the household. in sweden, social-distancing regulations are not taken very strictly due to the high proportion of single person household. whereas in italy based on the multi-generational homes apparently contributed to the multiplication of the coronavirus. 3-social distancing level: social distancing is very effective to stop the spread of the disease, but several reasons that various groups might show dissimilar levels of social distancing: -official advice might be dependable between regions, for instance, guidance in the us has varied even between neighboring towns. access to local guidance might be different between socioeconomic groups, for instance guidance might be provided online or in particular languages. -working from home might reduce social contact, but can only be available to some people focused in jobs linked to higher socioeconomic status. -stay at home regulations would be more than a challenge for those who live in smaller and crowded houses or without outside space. -some groups would be obedient to social distancing regulations not all. -not all who are infected by the covid-19 will react severely to it. there are some factors that contribute to the risk of covid-19 but they are probably felt differently by different socioeconomic groups (lipsitch et al., 2020) -people who have had medical problems of diabetes, chronic respiratory disease, cardiovascular disease, or even high blood pressure and cancer are at higher risk from coronavirus (giannis et al., 2020; fang et al., 2020; zheng et al., 2020) . -who has warned the smokers that they might be highly at risk because to the obvious effects of smoking on the lungs and smoking is common in lower socioeconomic groups. -different socioeconomic groups do not have access to the same level of healthcare services. this would particularly common in countries like us where the huge number of uninsured population is concentrated in certain industries not to universal health care system. therefore, some socioeconomic groups are more likely at risk compared to others. so, logically higher numbers of deaths can be expected from certain parts of society. this can be highly related for pension plans using analysis of this experience of the population to predict future mortality rates. the post pandemic population may look more different compared to the start point of this outbreak. the annual percentage change in gross domestic products is shown in table. 1. the short-term scenarios of the covid-19 environmental aspects raise many questions. china is struggling to rebound from the epidemic and has to limit the re-entry of covid-19 to its region by put a check on travelers coming from abroad (bogoch et al., 2020) . in a country with such a high population, where the majority of its population has not yet experienced covid-19, and has no immunological contact with this virus, the possibility of second wave is a big risk. european and north american countries has not yet reached to the peak of the epidemiological curve. one crucial aspect seems obvious: the fast control of the outbreak done by china could not be implemented to democratic countries where rights of individuals are very high. therefore, outside china no leader has the capability to enforce these measures at the level of china (bai et al., 2020) . the question is: what will happen in countries of indian sub-continent, the middle-east and south america, where they live in crowded forms traditionally, big gatherings are common, and the public health systems are insufficient. the possibility of secondary peak appearance could not be estimated. in the mid-term, the scenario in the southern hemisphere should be considered. not almost all south american and african countries have access to national health systems and sufficient health care services. many of these nations decided to close the borders, however very late, when they already had patients of covid-19 inside. all these indications show that the southern hemisphere would not escape from this pandemic. the outbreak is widening in the southern hemisphere now, and this is happening while the higher income nations are struggling over their own problems in (i) applying control actions (ii) trying to recuperate from the massive social and economic impacts, and (iii) focusing in preventing re-entry of covid-19 by foreign travelers (chinazzi et al., 2020) . the long-term scenario of probable secondary waves of outbreak is concerning as well. a second wave might be devastating more than the first one, based on other pandemics in history. economists have shown serious concerns about the economic effects of control measures taken during this crisis (hemida and abduallah, 2020) . however, there are many models that show the economic impacts of the disease and majority of the economists are challenged by the social and economic depth of the pandemic. they are trying to understand the control as soon as possible. although the economic losses are obvious, but still economists are not able to grasped the extending nature of the outbreak that is causing far more economic damage compared to drastic measures taken to end the pandemic globally as soon as possible (meo et al., 2020; anderson et al., 2020 . the covid-19 pandemic will have severe impact on socioeconomic growth across the globe as shown in table. 2. general actions to decrease person to person transmission of coronavirus are needed to control the present outbreak. special restrictions strategies and efforts should be applied to protect the highly vulnerable populations such as children, health care workers, and older aged people . a guideline has been already published for the medical employees, health care providers, and public health individuals and researchers who are interested in working in the coronavirus (mossa-basha et al., 2020) . the major death cases of coronavirus outbreak are happening mainly in old people probably because of a poor immune system that allows rapid growth of viral infections. the public services must provide in decontaminating reagents for sanitizing hands multiple times on a daily basis (luan and ching, 2020) . physical contact with contaminated and wet things must be counted in dealing with the coronavirus, particularly agents which could be a possible rout of transmission. china and some other countries such as the us applied travel screening that could control and prevent the spread of the virus. epidemiological alterations in coronavirus infections must be observed. the probable routes of transmission and subclinical infections, adaptation, progression must be taken into consideration and spreading of virus among people and potential intermediate animals and reservoirs should perceived. moreover, still there are significant numbers of questions that need to ponder. these are, but not limited to, details about how many people have been tested, how many of them turned positive and whether this range stays constant or fluctuating. additionally, only fewer pediatric cases have been reported to date; that could be due to lack of testing and not due to true infection (rothan and byrareddy, 2020) . only in a period of few months, the world has changed. thousands of people have been deceased, and hundreds of thousands have been infected by covid-19. and the rest of people who are not infected, their entire life has been changed by this virus. in italy, the most massive travel restrictions are being placed since second world war. in london, the normal busy bars, theatres, and other public places have been closed and people are asked to stay in their homes. the flights are being canceled in all over the world. majority of people are staying at home, practicing social distancing and working remotely (harapan et al., 2020) . it is all happening to control the spread of coronavirus, and to decrease the death rate. however, all these changes have led some unexpected consequences. as industries, transportation systems and all other bossiness have shut down; it has caused a sudden drop in carbon emission. compared to this time last year, levels of air pollution in new york have dropped at almost 50% due to measures that have been to restrict the spread of virus. in china, emissions data shows a 25% decrease at the starting point of the year as people were told to stay at home, factories closed and coal use feel by 40% at china's largest power plants since the last three months of 2019. according to the ministry of ecology and environment, the amount of good quality air was around 11.4% compared with the same time last year in more than 330 cities all over china. in europe, nitrogen dioxide (no 2 ) emission dropped over northern italy, spain and uk, as shown in satellite images (ficetola and rubolini, 2020) . this epidemic has also caused extensive job losses and threatened the sustenance of millions of people as businesses are struggling and are shut down to control the spread of virus. economic activities have been stopped and stock markets dropped along with the falling carbon another unexpected environmental impact of coronavirus has been observed in venice, italy. as the tourist's numbers culled due to the coronavirus, the waters in venice's canals are cleaner compared to the past. while motorboats, sediment churning and other water pollutants have been dropped efficiently, residents got amazed by seeing the clear water and the fish could be seen once again in the canals. one of the other effects of coronavirus on environment is the noticeable drop in coal consumption. this contributed in a large scale drop in air pollutants in china. the number of airborne pollutants like co 2, co and nitrous oxides has fallen too. as millions of people are holding on lockdown across the globe, energy consumption profiles in buildings are being disturbed. as many people working from home nowadays, domestic energy consumption is predicted to rise very quickly. the predictions data showed that this has risen around 6 to 8% in the us. this pandemic would ultimately save energy and also might have an effect on reducing the consumption of polluting fuels in power stations as the demand has been dropped (lau et al., 2020) . the covid-19 pandemic has changed the air quality in many cities across the world as shown in the fig. 2 . the covid-19 pandemic is spreading very quickly every day, and the number of people putting on lockdown is increasing, to date more than 120, 438 people have died across the globe and there is a direct loss to the world economy. however, many think that there is a good side; that the spread of virus has been decreasing air and water pollution and probably even saved lives in this process. nevertheless, this epidemic which is taking people's lives certainly should not be seen as a way of bringing about positive environmental change. first of all, it is not certain for how long this dip in emission will be. when the epidemic finally subside, then carbon and other pollutant emissions get back then it would be as if this clear sky view never happened and the changes we see today will not have lasting impact. general actions to reduce person to person transmission of covid-19 are required to control the current outbreak. special attention and labors should be applied to save the highly vulnerable populations including children, health care workers, and old people. there is already published guideline available for the medial employees, health care providers, and public health individuals and researchers who are interested in working in the coronavirus. most of death cases of coronavirus outbreak are happening largely in old people possibly due to a weak immune system that permits rapid growth of viral infections. the public services must provide decontaminating reagents for sanitizing hands multiple times on a routine basis. physical contact with contaminated and wet things must be taken into count while dealing with coronavirus, particularly agents that could be a possible route of transmission. epidemiological alterations in coronavirus infections must be observed taking into consideration the probable routes of transmission and subclinical infections, furthermore to the adaptation, progression, and spreading of virus among people and potential intermediate animals and reservoirs. there are still some remaining doubts that have to be considered. the most important thing is about the details of how many people have been tested, how much of them turned positive and whether this range stays constant or variable. a less number of pediatric cases have been reported to date; that could be due to lack of testing and not due to true infection. how will country-based mitigation measures influence the course of the covid-19 epidemic? coronavirus disease 19 (covid-19): implications for clinical dental care presumed asymptomatic carrier transmission of covid-19 pneumonia of unknown aetiology in wuhan, china: potential for international spread via commercial air travel remdesivir for severe acute respiratory syndrome coronavirus 2 causing covid-19: an evaluation of the evidence the effect of travel restrictions on the spread of the 2019 novel coronavirus (covid-19) outbreak are patients with hypertension and diabetes mellitus at increased risk for covid-19 infection? comparison of air quality in some of the biggest cities around the world before the covid-19 pandemic and while the lockdown climate affects global patterns of covid-19 early outbreak dynamics coagulation disorders in coronavirus infected patients: covid-19, sars-cov-1, mers-cov and lessons from the past coronavirus disease 2019 (covid-19): a literature review feasibility of controlling covid-19 outbreaks by isolation of cases and contacts the sars-cov-2 outbreak from a one health perspective coronavirus (covid-19) outbreak: what the department of radiology should know early dynamics of transmission and control of covid-19: a mathematical modelling study the positive impact of lockdown in wuhan on containing the covid-19 outbreak in china coronavirus disease (covid-19): spectrum of ct findings and temporal progression of the disease defining the epidemiology of covid-19-studies needed a reusable mask for coronavirus disease sars to novel coronavirus-old lessons and new lessons biological and epidemiological trends in the prevalence and mortality due to outbreaks of novel coronavirus covid-19 the institutional and cultural context of cross-national variation in covid-19 outbreaks policies and guidelines for covid-19 preparedness: experiences from the university of washington the epidemiology and pathogenesis of coronavirus disease (covid-19) outbreak trop med int health, 2020. the covid-19 epidemic clinical characteristics of 138 hospitalized patients with 2019 novel coronavirus-infected pneumonia in wuhan, china pathological findings of covid-19 associated with acute respiratory distress syndrome covid-19 and the cardiovascular system a pneumonia outbreak associated with a new coronavirus of probable bat origin key: cord-276392-m1bbt8bo authors: asyary, al; veruswati, meita title: sunlight exposure increased covid-19 recovery rates: a study in the central pandemic area of indonesia date: 2020-04-27 journal: sci total environ doi: 10.1016/j.scitotenv.2020.139016 sha: doc_id: 276392 cord_uid: m1bbt8bo abstract this study aims to present the correlation between sunlight exposure and covid-19 statuses in jakarta, indonesia. the secondary data analysis was derived from surveillance data for covid-19 from government authorities, including the ministry of health, the meteorological, climatological, and geophysical agency, and the local government of jakarta. three statuses related to covid-19 were examined in the study: incidence, death, and recovered. meanwhile, sunlight exposure was presented as daily duration of it. only the number of recovered patients correlated significantly with sunlight exposure (p-value = .025; r = 0.350). this study's findings showed that sunlight exposure was associated with recovery from covid-19. coronavirus disease 2019 (covid-19) is not only rapidly spreading but has become a global pandemic that affects many, including developing countries with limited resources (singhal, 2020) . in fact, even the currently affected developed countries are overwhelmed in their fight against covid-19 (bénassy-quéré et al., 2020; heymann and shindo, 2020; saglietto et al., 2020) . it is considered that most developing countries will face more challenges than developed countries in curbing the spread of covid-19 in their regions, causing them to potentially evolve into the new epicenter of the pandemic, and indonesia is not exempted (hopman et al., 2020) . covid-19 is caused by a type of influenza virus that suppresses the body's immune system so that the viruses can grow in the respiratory tissues and organs (shi et al., 2020; xu et al., 2020) . in this situation, individuals who are elderly or with prior comorbidities are more vulnerable to the severe effects of covid-19 due to inadequate immune systems j o u r n a l p r e -p r o o f (garnier-crussard et al., 2020; le couteur et al., 2020; morley and vellas, 2020) . besides that, inadequate healthcare management, such as failure to provide early diagnosis and prompt treatment, would decrease the rate of recovery among covid-19 patients (greenhalgh et al., 2020; hopman et al., 2020) . march 2020 (djalante et al., 2020; wenham et al., 2020) . moreover, indonesia has one of the highest proportions of death related to covid-19 cases among countries in the world, with the epicenter of the disease being its capital, jakarta (organization, 2020a) . the confirmed positive cases of covid-19 in indonesia are divided into three levels of severity: 1) high, 2) moderate, and 3) low (indonesian ministry of health, 2020a). patients whose conditions are of high or moderate severity are given intensive medical care in healthcare facilities. meanwhile, low-severity cases of covid-19 are managed the same way as the rest of the general population, meaning they should stay home and practice social isolation and physical distancing (indonesian ministry of health, 2020a). at the same time, the government has strongly promoted the clean and healthy living behavior (phbs) and people's healthy lifestyle movement (germas) programs to encourage the people to include routine outdoor/indoor exercise to decrease the spread of covid-19 (indonesian ministry of health, 2020b). the world health organization (who) reported that there is still no evidence that sunlight can terminate covid-19 (world health organization, 2020) . moreover, too much of sunlight may cause harm through its ultraviolet, infrared, etc. (karapiperis et al., 2020) . however, sunlight contributes to the healing of multiple health condition including respiratory diseases such as influenza and severe acute respiratory syndrome (sars) (geier et al., 2018; miller, 2018) . weather factors have shown persistent correlation to the emergence and re-emergence of infectious diseases, including covid-19 (tosepu et al., 2020) . thus, evidence for the effect of sunlight on covid-19 is needed as the correlation between the two is still rarely assessed. jakarta is the capital city and business center of indonesia. it is geographically located within the range of 5°19'12" south latitude to 6°23'54" south latitude and 106°22'42" east longitude to 106°58'18" east longitude, with an average altitude of ±7 meters above the sea surface. jakarta, which has tropical climates, has two seasons: rainy season that happens annually from october to march and dry season that takes place from april to september annually. there are 132 referral hospitals available to treat covid-19 patients of high and moderate severity in indonesia. eight of these, plus an emergency hospital, are in jakarta. the set of relevant data, ranging from 2 nd march to 10 th april 2020, was obtained from the indonesian government authorities. the daily confirmed cases of covid-19 incidence, death, and recovery were derived from the jakarta local government. this data was also made available by the indonesian ministry of health as well as the indonesian national task force team for covid-19. meanwhile, the dataset of daily sunlight in jakarta was obtained from the meteorological, climatological, and geophysical agency of indonesia. spearman's correlation was performed to analyze the coefficient correlation value and determine whether significance existed. this statistical analysis was used to determine correlation between the existing variables. these variables were number of covid-19 positive cases, deaths, and patients who recovered, and sunlight exposure. according to figure 1(a) , the incidence of covid-19 in jakarta had been increasing. since the first multiple cases of covid-19 were reported on 3 rd march 2020, jakarta had seen an average of 45.25 new confirmed covid-19 cases daily. the daily average number of recovered patients was 1.50, which was lower than the daily average deaths at 3.80 cases. therefore, the death proportion of covid-19 cases in jakarta was 8.4% higher than the recovered proportion at 3.3%. figure 1(b) shows that the duration of sunlight exposure for covid-19 patients in jakarta fluctuated daily. the shortest duration of daily sunlight exposure was 0 minute, while the longest duration was 480 minutes in jakarta. the average duration of daily sunlight exposure was 217.95 minutes or 3.6 hours. in this study, we found that higher duration of sunlight exposure was related to more cases of recovery from covid-19 among patients. this correlation is in line with previous evidence that sunlight does not terminate the covid-19 virus so it cannot prevent the infection. conversely, sunlight can maintain the health condition of covid-19 patients so they have opportunity to recover from the disease. sunlight boosts the immune system, which slows down the development of influenza and sars agents in the human body (cannell et al., 2006; miller, 2018) . in this case, covid-19 patients who experienced sunlight exposure when they were receiving care either in hospitals or home settings were more likely to recover from the disease. sunlight triggers vitamin d production, which functions to increase the immune system (slusky and zeckhauser, 2018) . poor sunlight exposure activates influenza (sagripanti and lytle, 2007) . previous studies have shown that sunlight exposure significantly contributed to the healing of most respiratory conditions including tuberculosis and lung disease (aloia and li-ng, 2007; asyary et al., 2017) . being in a region with a tropical climate, jakarta can take advantage of the presence of abundant sunlight in every season. the health benefits of exposure to sunlight have been established (singhal, 2020) . access to much-needed sunlight can enhance mood as well as release endorphins that will increase immunity against diseases such as covid-19 (sternberg and engineer, 2020) . as it sits on the equator, the indonesian territory, including jakarta, is known as a tropical region that experiences two seasons: dry and rainy. however, even with its rainfall during the rainy season, jakarta is still quite dry. the average duration of maximum sunlight is 3 to 3.5 hours per day in jakarta, which amounts to 4.8 kilowatthour per square meter per day (kwh/m 2 /day), or 10 times the potential of european sunlight (indonesia national energy board, 2013). most countries around the world, including indonesia, are welcoming the dry or summer season, which takes place from april to september and can be potentially leveraged by each country to fight covid-19. this potential approach can be accompanied by the formal treatment/therapy according to covid-19 clinical guidelines (organization, 2020b) . who has only underlined the benefit of sunlight for clothes management (organization, 2020c) , so this finding will assist medical care particularly in j o u r n a l p r e -p r o o f low-resource health settings or places with inadequate covid-19-mitigating response, including jakarta (hopman et al., 2020; le couteur et al., 2020) . despite this study's significant finding about the relationship between sunlight and covid-19 recovery, this research has limitations. the covid-19 recovery factors could be affected by several others variables such as prompt treatment/therapy, phbs and germas, and physical capabilities. it is also essential to explore the type and characteristics of sunlight exposure in detail. additionally, the available data provided by the authorities did not record the exposure of every covid-19 patient to sunlight. this study shows that sunlight exposure correlated significantly with recovery from covid-19 among patients in jakarta of indonesia. however, sunlight exposure did not correlate significantly with the occurrence of and death from covid-19. this preliminary study needs to be developed further as sunlight presents genuine potential in accelerating recovery from covid-19 not only in jakarta but also other countries, especially those with high death rates due to this pandemic. re: epidemic influenza and vitamin d epidemiology and infection level of exposure of childhood tuberculosis with adult pulmonary tuberculosis household contacts 13 covid-19: europe needs a catastrophe relief plan. mitigating covid econ epidemic influenza and vitamin d review and analysis of current responses to covid-19 in indonesia: period of novel coronavirus (covid-19) epidemic: what are the risks for older patients? a longitudinal ecological study of seasonal influenza deaths in relation to climate conditions in the united states from covid-19: what is next for public health? managing covid-19 in low-and middleincome countries indonesia is high potential to sunlight beneficiary covid-19) in indonesia. jakarta. indonesian ministry of health, 2020b. prevent covid-19 with germas. jakarta. indonesian national task team force for coronovirus assessment for the seasonality of covid-19 should focus on ultraviolet radiation and not 'warmer days covid-19 is a disease of older people immune system: your best defense against viruses and bacteria from the common cold to the sars virus covid-19 and older adult coronavirus disease 2019 (covid-19): situation report, 72. organization, w.h., 2020b. infection prevention and control guidance for long-term care facilities in the context of covid-19: interim guidance water, sanitation, hygiene and waste management for covid-19: technical brief covid-19 in j inactivation of influenza virus by solar radiation covid-19 infection: the perspectives on immune responses a review of coronavirus disease-2019 (covid-19) sunlight and protection against influenza is covid-19 making you stay at home or" shelter-inplace"? turn your home into a healing space! correlation between weather and covid-19 pandemic in jakarta covid-19: the gendered impacts of the outbreak fact or fiction [www document suppressed t cell-mediated immunity in patients with covid-19: a clinical retrospective study in wuhan key: cord-352630-dx1fwngb authors: hossain, md. sabbir; ahmed, sulaiman; uddin, md. jamal title: impact of weather on covid-19 transmission in south asian countries: an application of the arimax model date: 2020-11-02 journal: sci total environ doi: 10.1016/j.scitotenv.2020.143315 sha: doc_id: 352630 cord_uid: dx1fwngb we aimed to examine the impact of weather on covid-19 confirmed cases in south asian countries, namely, afghanistan, bangladesh, india, pakistan, and sri lanka. data on daily confirmed cases, together with weather parameters, were collected from the first day of covid confirmed cases in each country to 31 august 2020. the weather parameters were rainfall (mm), relative humidity (%), maximum and minimum temperature (°c), surface pressure (kpa), maximum air pollutants matter pm 2.5 (μg/m3) and maximum wind speed (m/s). data were analyzed for each investigated countries separately by using the autoregressive integrated moving average with explanatory variables (arimax) model. we found that maximum wind speed had significant negative impact on covid-19 transmission in india (-209.45, 95% confidence interval (ci): -369.13, -49.77) and sri lanka (-2.77, 95% ci: -4.77, -0.77). apart from india, temperature had mixed effects (i.e., positive or negative) in four countries in south asia. for example, maximum temperature had negative impact (-30.52, 95% ci: -60.24, -0.78) in bangladesh and positive impact (5.10, 95% ci: 0.06, 10.14) in afghanistan. whereas rainfall had negative effects (-48.64, 95% ci: -80.17, -17.09) in india and mixed effects in pakistan. besides, maximum air pollutants matter pm 2.5 was negatively associated with the confirmed cases of covid-19. in conclusion, maximum wind speed, rainfall, air pollutants (maximum pm 2.5) and temperature are four variables that could play a vital role in the transmission of covid-19. although there is a mixed conclusion regarding weather parameters and covid-19 transmission, we recommend developing environmental policies regarding the transmission of covid-19 in south asian countries. novel coronavirus (covid-19) is a respiratory disease caused by severe acute coronavirus syndrome 2 (sars-cov-2) (f. . due to its highly human -to -human transmission nature (bogoch et al., 2020; c. wang et al., 2020) the disease spread rapidly throughout the world and was declared a global pandemic by world health organization (who) on 11 march 2020. over 25 million confirmed cases (25, 094, 338) and 844,060 covid-19 deaths were reported around the world until 31 august 2020 (world health organization, 2020) . several studies suggested that weather parameters like temperature, rainfall, humidity, wind speed, and air pollutants may influence the transmission of the covid-19 (ahmadi et al., 2020; al-rousan and al-najjar, 2020; bashir et al., 2020; jüni et al., 2020; liu et al., 2020; qi et al., 2020; sobral et al., 2020; tosepu et al., 2020; zoran et al., 2020) . for example, liu et al. (2020) , qi et al.(2020) , sobral et al. (2020) and y. demonstrated that the transmission of covid-19 infection is suppressed as temperature increases in china and some other regions around the world. moreover, al-rousan and al-najjar (2020), tosepu et al. (2020) and zoran et al. (2020) reported a significant positive correlation in china, indonesia and italy while in iran, ahmadi et al. (2020) and in 144 geopolitical areas worldwide, jüni et al. (2020) reported no significant correlation between temperature and covid-19 transmission. furthermore, liu et al. (2020) , qi et al. (2020) and y. stated humidity as one of the important weather parameters that significantly reduce the virus transmission of covid-19. but some studies reported no significant impact of humidity on the covid-19 epidemic (bashir et al., 2020; tosepu et al., 2020) . also, ahmadi et al. (2020) , sobral et al. (2020) and zoran et al. (2020) investigated the impact of rainfall, air pollutants, and wind speed on covid-19 and found that rainfall and air pollutants had a positive j o u r n a l p r e -p r o o f impact while wind speed had a significant negative impact on covid-19. however, poirier et al. (2020) reported that weather parameters alone could not decline the coronavirus transmission. several statistical methods such as correlation, regression analysis, generalized additive model qi et al., 2020; xie and zhu, 2020) , and generalized linear model , are extensively applied to assess the impact of environmental factors on covid-19 transmissibility. however, among those methods, most of the studies used correlation and regression analysis techniques (guo et al., 2020; jüni et al., 2020; şahin, 2020; sobral et al., 2020; tosepu et al., 2020; zoran et al., 2020) . these studies have used the regression model for time series data but have not determined the stationary condition of the data, although stationary is the precondition for implementing any regression analysis techniques with time-series data (chen et al., 2004) . as a result, these studies could have produced incorrect estimates due to misspecification of the applied models. a well-defined time series technique, such as the autoregressive integrated moving average with explanatory variables (arimax) model, is therefore essential to apply in order to eliminate the long-term trend of covid-19 epidemic and to consider environmental factors as external regressors too. in addition, due to lack of data availability, most of the study was conducted at the birthplace of covid-19, this study was accumulated different types of data, including daily covid-19, climate, and air pollutants datasets from the first unequal date of covid-19 confirmed cases to 31 august 2020 of five south asian countries, such as afghanistan, bangladesh, india, pakistan, and sri lanka. j o u r n a l p r e -p r o o f °c and annual rainfall averaging about 255 millimeters (wikipedia, 2020b) . sri lanka's climate is tropical and consists of distinct wet and dry seasons (world travel guide, 2020). the geographical location of five south asian countries with cumulative covid-19 confirmed cases up to 31 august was presented in fig. 1 . we used the arimax model to evaluate the relationship between daily covid-19 confirmed cases and daily climatic variables. the steps of the whole process are listed as below (yan et al., 2017) : first, the arima model was developed to the time series of confirmed cases from 1 st day of confirmed cases to 31 august 2020 for each country. we used the bayesian information criteria (bic) to identify the best model for each country. the detailed procedure of the arima model was found in supplementary materials (s1). second, cross-correlation function (ccf) was used to explore the relationship between climatic variables and covid-19 confirmed cases for each country separately. the dependent (covid-19 confirmed cases) and independent variables (climate variables) were pre-whitened by the previously fitted arima models. pre-whitening is an important technique for seeing which lag of the independent variable affects the dependent variable. pre-whitening, the method of eliminating or reducing short-term stochastic persistence widely applied to the study of a variety of geophysical variables in time series (razavi and vogel, 2018) . finally, climate variables selected through step 2 were incorporated as covariates into the arimax model. the maximum likelihood method was applied for the estimation of the parameters. to assess if the residual series was white noise, the ljung-box q test was performed. we used r software version 3.6.1 to analyze the data (team, 2013) . to perform this analysis, mass, hmisc, pastecs, forecast, tseries, & lmtest packages were used. figure 1 shows that until 31 august 2020 the highest and lowest number of confirmed covid-19 cases were recorded in india (3,691,200), and sri lanka (3,050), respectively. also, fig. 2 shows that the trend line of covid-19 confirmed cases between afghanistan, bangladesh, and pakistan is very similar, after 100 days of transmission these countries shows a decreasing trend. india have the highest rate of transmission compared to others and the transmission rate is continuously increasing from the beginning which makes india as a new hotspot of covid-19 but the line of the pattern for pakistan and sri lanka shows considerable inconsistency. fig. a.3) figure 3 shows that the cross-correlation between the pre-whitened weather variables and covid-19 confirmed cases at lags 0 to 12 days. here only positive lags would be considered because the positive value indicated that climatic factors could affect covid-19 confirmed cases a certain period later. for afghanistan, except minimum temperature at lag 5 and maximum temperature at lag 12 days, all other climatic variables failed to prove the statistically j o u r n a l p r e -p r o o f significant correlation with covid-19 confirmed cases at different lags (fig. 3) . maximum temperature at lag 3 (fig. 3) , rainfall and maximum wind speed at lag 6 ( fig. a.1 bangladesh and for india rainfall at lag 6, wind speed at lag 8 (fig. 3) and maximum particulate matter pm 2.5 at lag 2 (fig. a.1) had a significant correlation with confirmed cases. similarly, for sri lanka, and pakistan various weather parameters at different lags have found a significant correlation with covid-19 confirmed cases (fig. 3, fig. a.1) . at different lags, attempts were made to integrate the above-mentioned climate variables as covariates into the arimax model. for example, for afghanistan, the arimax model was set up separately by considering each of the covariates; maximum temperature at lag 12, and minimum temperature at lag 5. likewise, the previously selected variables at different lags were considered to be covariates in the arimax model for certain countries and only those were provided in table 3 , which shows a significant major effect on covid-19. we examined the effects of weather on covid-19 transmission in south asian countries using the arimax model approach. our study shows that weather variables have significant positive or negative effects on covid-19 infections. however, the findings don't seem to be consistent across the selected countries in south asia. for example, the maximum wind speed was significantly negatively correlated with the covid-19 transmission only in india and sri lanka. in addition, the temperature had significant positive and negative impact on the transmission in four countries in south asia, excluding india. we found that maximum wind speed had a significant negative impact on covid-19 transmission which is in line with some previous studies (ahmadi et al., 2020; islam et al., 2020; zoran et al., 2020) . however, this finding was opposed to some recent studies (bashir et al., 2020; menebo, 2020) where they claimed that there was no correlation between wind speed and covid-19 transmission. moreover, in the previous outbreak of influenza virus or severe acute respiratory syndrome (sars), or middle east respiratory syndrome coronavirus (mers-cov), the wind speed regarded as one of the key factors that promote the transmission of sars, mers and influenza (altamimi and ahmed, 2020; chan et al., 2011; chong et al., 2020; peci et al., 2019) . moreover, previous studies (doremalen et al., 2020; bourouiba, 2016) claimed that covid-19 may be airborne which can stabilize in aerosols for up to 3 hours and increase the risk of transmission through aerosols. the risk of covid-19 spread might be more in closed places with low wind speed because in low wind speed particle density of infectious droplets is much higher which can favor the spread of covid-19 virus in the environment. our analyses also showed that temperature had a significant positive and negative impact on the transmissibility of covid-19 in four south asian countries except for india. menebo, (2020), bashir et al. (2020) and (a. gupta et al., 2020) also reported similar findings that temperature had a significant positive correlation with covid-19. furthermore, some other studies reported inverse relationship (guo et al., 2020; islam et al., 2020; rahman et al., 2020; shi et al., 2020; or no relation (jamil et al., 2020; poirier et al., 2020) between temperature and incidence of covid-19. as the south asian countries have high population density with low income including less aware of the transmission, people often break the lockdown for their livelihood on shiny days. and this may be one of the reasons for the positive relationship between temperature and confirmed cases. in that case, temperature plays one of the key indirect factors for covid-19 transmission. we did not find any association of covid-19 transmission with relative humidity and surface pressure. shi et al. (2020) also obtained similar findings that there was no significant correlation between covid-19 incidence and absolute humidity. however, some other studies (s. gupta et al., 2020; ma et al., 2020; found opposite results that there exists an association of covid-19 with relative humidity and pressure. air pollutants included particulate matter with aerodynamic diameter µg per m3 (maximum pm 2.5) had a significant negative impact on covid-19 only in pakistan. ma et al. (2020) found similar findings in wuhan, china that the mortality counts due to covid-19 were negatively correlated with pm 2.5 and pm 10. zoran et al. (2020) and bashir et al. (2020) reported opposite findings (positive correlation) that a high level of air pollution has a significant impact on the increased rates of confirmed covid-19 cases. it is obvious that higher j o u r n a l p r e -p r o o f journal pre-proof concentrations of air pollution could increase the risk of respiratory virus infection (horne et al. 2018 ). but interestingly, our results showed that covid confirmed cases were associated with a decrease in the average concentration of air pollutants (pm 2.5), which could be a reflection of higher rainfall at the same time, as rainfall washes away pollutants from the atmosphere and for pakistan, we also reported the significant effect of rainfall. similar type of argument was also made by silva et al. (2014) where they showed that severe acute respiratory infection (sari) cases were negatively associated with air pollutants. hence, we argue that the effect of air pollutants on covid transmission depends on the impact of other relevant factors (rainfall) and the effect varies depending on city, region, and the specific pollutants under investigation. rainfall had a significant negative impact on covid-19 transmission in india and pakistan, also had positive impact in pakistan (at lag 12) which is in line with (a. gupta et al., 2020; menebo, 2020; sobral et al., 2020) and opposite with some recently published studies (ahmadi et al., 2020; bashir et al., 2020; tosepu et al., 2020) . the possible reason for the negative correlation is that rainfall rate contributes to the accumulation and washout process of aerosols and microbial bio-aerosols (bacteria, viruses, fungi) implying that viruses could not have longer residence times in the atmosphere and, consequently will not able to disperse further. another hypothetical justification might be that people often stay home on rainy days, which also could reduce the transmission. we also found that rainfall at lag 12 had an impact on fig. 3 . cross-correlation between covid-19 confirmed cases and weather variables 5 investigation of effective climatology parameters on covid-19 outbreak in iran the correlation between the spread of covid-19 infections and weather variables in 30 chinese provinces and the impact of chinese government mitigation plans climate factors and incidence of middle east respiratory syndrome coronavirus correlation between climate indicators and covid-19 pandemic in new york potential for global spread of a novel coronavirus from the effects of temperature and relative humidity on the viability of the sars coronavirus yield variability as influenced by climate: a statistical investigation association between meteorological variations and activities of influenza a and b across different climate zones: a multi-region modelling analysis across the globe discovery bangladesh [www document aerosol and surface stability of sars-cov-2 as compared with sars-cov-1 transmissibility of covid-19 and its association with temperature and humidity shortterm elevation of fine particulate matter air pollution and acute lower respiratory infection novel coronavirus (covid-19) cases data [www document temperature, humidity, and wind speed are associated with lower covid-19 incidence no evidence for temperature-dependence of the covid-19 epidemic. medrxiv 2020.03.29 impact of climate and public health interventions on the covid-19 pandemic: a prospective cohort study meteorological factors correlate with transmission of 2019-ncov: proof of incidence of novel coronavirus pneumonia in hubei province impact of meteorological factors on the covid-19 transmission: a multi-city study in china effects of temperature variation and humidity on the death of covid-19 in wuhan temperature and precipitation associate with covid-19 new daily cases : a correlation study between weather and covid-19 pandemic in oslo the power project [www document effects of absolute humidity, relative humidity, temperature, and wind speed on influenza covid-19 transmission in mainland china is associated with temperature and humidity: a time-series analysis a retrospective analysis of influence of environmental / air temperature and relative humidity on sars-cov-2 outbreak. prepr prewhitening of hydroclimatic time series ? implications for inferred change and variability across time scales impact of weather on covid-19 pandemic in turkey the impact of temperature and absolute humidity on the coronavirus disease 2019 (covid-19) outbreak -evidence from china respiratory viral infections and effects of meteorological parameters and air pollution in adults with respiratory symptoms admitted to the emergency room association between climate variables and global transmission of sars-cov-2 swedish committee for afghanistan (sca) [www document estimation of the transmission risk of the 2019-ncov and its implication for public health interventions r: a language and environment for statistical computing correlation between weather and covid-19 pandemic in jakarta ~:text=a tropical rainy climate governs,that fall under this group.&text=2) in india a tropical climate_of_pakistan#:~:text=pakistan has four seasons%3a a,period of october and november world air quality index project world health organization, 2020. coronavirus disease (covid-19) world travel guide [www document a new coronavirus associated with human respiratory disease in china effects of temperature and humidity on the daily new cases and new deaths of covid-19 in 166 countries association between ambient temperature and covid-19 infection in 122 cities from china impact of meteorological factors on the incidence of bacillary dysentery in beijing, china : a time series analysis assessing the relationship between surface levels of pm2 . 5 and pm10 particulate matter impact on covid-19 in august 2020. 1 here, arima (2,1,2) means autoregressive term of order 2, moving average term of order 2 and first difference was taken to make the series stationary. 2 all the selected best arima models need to satisfy the three conditions: lowest bic, significant parameter estimation and no autocorrelation in residual analysis. though arima (0,1,3) has lowest bic value, it provides insignificant parameter estimation. that's why we move for 2 nd lowest bic value and arima (2,1,2) satisfies all the three conditions. 3 for india 2 nd difference was taken to make the covid confirmed series trend and mean stationary. note: pm 2.5 means maximum atmospheric particulate matter with diameter less than 2.5 and * means significant at 5% level j o u r n a l p r e -p r o o f key: cord-299432-lbv69du4 authors: franklin, alan b.; bevins, sarah n. title: spillover of sars-cov-2 into novel wild hosts in north america: a conceptual model for perpetuation of the pathogen date: 2020-05-12 journal: sci total environ doi: 10.1016/j.scitotenv.2020.139358 sha: doc_id: 299432 cord_uid: lbv69du4 abstract there is evidence that the current outbreak of the novel coronavirus sars-cov-2, which causes covid-19, is of animal origin. as with a number of zoonotic pathogens, there is a risk of spillover into novel hosts. here, we propose a hypothesized conceptual model that illustrates the mechanism whereby the sars-cov-2 could spillover from infected humans to naive wildlife hosts in north america. this proposed model is premised on transmission of sars-cov-2 from human feces through municipal waste water treatment plants into the natural aquatic environment where potential wildlife hosts become infected. we use the existing literature on human coronaviruses, including sars cov, to support the potential pathways and mechanisms in the conceptual model. although we focus on north america, our conceptual model could apply to other parts of the globe as well. j o u r n a l p r e -p r o o f 2 infected humans to native wildlife that could subsequently serve as new reservoir hosts for the virus. in this way, the virus may become entrenched in areas outside of its region of origin and available for future outbreaks. however, for this to occur there are a number of hurdles that the virus would need to overcome to infect a novel wildlife host. here, we propose a plausible mechanism where sars-cov-2, the pathogen causing the disease covid-19, could spillover from infected humans into novel wildlife hosts in north america. we developed a conceptual model for this hypothesized mechanism (fig. 1) , which we outlined as five premises supported from the existing literature on shedding of coronaviruses by humans, survivability of these viruses, and documented pathways for movement of coronaviruses into the natural environment. although we focused on north america, our conceptual model could also be applied to other parts of the globe. for our conceptual model to be plausible, we assume that coronaviruses can be shed in the feces of infected humans. this assumption has been supported by research on other coronaviruses (yeo et al. 2020) . for example, mers coronavirus was detected in 14.6% and 2.4% of fecal and urine samples, respectively, from 37 infected individuals (corman et al. 2015) , while sars cov was shed in the feces of 56 infected individuals for a median of 27 days, with 4 individuals shedding for over 100 days (liu et al. 2004 ). in addition, 38.4% of sars-infected patients experienced diarrhea, sars-cov rna was detected in 16─73% of the stool samples, and cultured from the small intestines of 5 patients (leung et al. 2003 , yeo et al. 2020 ). in addition, sars-cov remained infectious in diarrheal fecal samples at room temperature for up to 4 days (lai et al. 2005) . more recently, a u. s. patient with covid-19 also shed sars-cov-j o u r n a l p r e -p r o o f 3 59% of 96 infected patients for up to 31 days (zheng et al. 2020 ). thus, a portion of infected humans are capable of shedding novel coronaviruses, including sars-cov-2, in their feces, with some for extended (1-4 months) periods. although there is uncertainty whether sars-cov-2 remains infectious in feces, similar coronaviruses, such as sars-cov, are infectious in feces, and ace2 receptors for sars-cov-2, are abundant in gastric, duodenal, and rectal epithelia cells in humans (xiao et al. 2020) . this, coupled with the positive detection of sars-cov-2 rna from feces in a large portion of infected patients (wu et al. 2020b , xiao et al. 2020 , zheng et al. 2020 suggests that infectious sars-cov-2 virions are secreted from gastrointestinal cells into feces (xiao et al. 2020 ). if fecal shedding is substantial in terms of number of infected individuals at focal locations, such as in hospitals, airports, or concentrated housing, then substantial amounts of virus could be deposited into municipal sewage systems (pathways 1 and 2 in fig. 1 ). human coronaviruses (hcov) can survive for extended periods in the environment, especially aqueous environments (geller et al. 2012) . survival rates of hcov in saline ranged from 80-100% for 3 days and 30-55% for six days (geller et al. 2012 ). using two surrogate hcovs for sars cov, casanova et al. (casanova et al. 2009 ) found that the viruses remained infectious in water and sewage for 17-22 days at 25° c and <1 log 10 reduction in infectivity at 4° c. in addition, sars-cov-2 rna has been detected in untreated wastewater and sewage in sufficient quantities to j o u r n a l p r e -p r o o f once hcov arrives at waste water treatment plants (wwtp) in sewage (pathway 2 in fig. 1) , it needs to maintain its infectivity through the treatment process to be of concern in the effluent that is ultimately introduced into the natural environment. in general, the transit time for sewage to reach a wwtp is less than one day (wigginton et al. 2015) . while wwtp do reduce virus levels, infective virus is still detected in the effluent from these plants (wigginton et al. 2015) . based on metagenomics, coronaviruses were detected in 80% of the samples from effluent class b sewage sludge from 5 wwtp in the u.s., which is typically applied to agricultural lands as a soil amendment (bibby and peccia 2013) . although data is lacking for coronaviruses, wastewater treatment prior to disinfection results in 0─2 log 10 reduction of infective enteroviruses and 2 ─ >3-log reduction of infective adenoviruses, with infectious virus still being detected in the final effluent from the waste treatment process released into the environment (simmons and xagoraraki 2011, wigginton et al. 2015) . thus, there is evidence that infectious coronaviruses could pass through the wastewater treatment process and enter natural aquatic systems via wwtp (pathway 3 in fig. 1 ). even if wwtp completely or mostly eliminated sars-cov-2 from their effluent when once released into natural aquatic systems, coronaviruses would be available for uptake in wildlife hosts (pathway 4 in fig. 1 ). insectivorous bats (order chiroptera) are the logical reservoir host for covid-19 in north america because they were considered the reservoir host for sars cov (banerjee et al. 2019) and are suspected as a host, such as rhinolophus spp., for sars-cov-2 (lu et al. 2020 ). in addition, coronaviruses have been detected in feces of north american bats with viral rna prevalence in shed feces of 17-50%, depending on the species of bat (dominguez et al. 2007 ). other north american wildlife strongly associated with aquatic environments are raccoons (procyon lotor), which have also been infected with coronaviruses (martin and zeidner 1992) . interestingly, raccoons also feed on aquatic organisms, such as mollusks, that are also potential candidates to bioaccumulate viruses. where they increased their foraging activity downstream from wwtp relative to upstream (vaughan et al. 1996 , abbott et al. 2009 ). this suggests a potential pathway for bats to become infected with hcov, and presumably sars-cov-2, from water sources contaminated with these pathogens from wwtp. america through a wildlife host is whether spillback from wildlife hosts to humans could occur (pathway 5 in fig. 1 ). spillover into wildlife and subsequent spillback into the human population represents an unmanaged source of sars-cov-2. for example, if bats are considered the likely reservoir host for covid-19, spillback of coronaviruses in north america could occur where bats use buildings for nocturnal roosts or hibernation sites and deposit their feces where humans might encounter them, such as in attics of residences (voigt et al. 2016) . north american bats have been shown to shed coronaviruses in their feces, often at high (up to 50%) prevalence (dominguez et al. 2007) . airborne transmission of sars cov from human fecal matter was considered the primary route of infection of 187 human cases in a housing complex (yu et al. 2004) , indicating that aerosol transmission of hcov from bat feces to humans is possible. although there is still considerable uncertainty about which wildlife species can serve as reservoir hosts for sars-cov-2, current research on domestic animals indicates potential j o u r n a l p r e -p r o o f 8 candidates in wild cats and mustelids . because domestic cats can efficiently replicate sars-cov-2 and transmit the virus to naïve cats , domestic cats represent another mechanism for spillover transmission from wild cats to humans. another risk associated with the establishment of sars-cov-2 in a wildlife host population is the potential for mutation in novel hosts that results in a variant virus (menachery et al. 2017) . of particular concern, is whether there is the potential for recombination of sars-cov-2 with other bat coronaviruses should spillover of sars-cov-2 occur in bat populations. while the primary risk associated with the current covid-19 outbreak appears to be humanto-human transmission of sars-cov-2, we believe the existing evidence also supports the plausibility of novel coronaviruses, such as sars-cov-2, spilling over to new wildlife hosts through fecal shedding by infected humans and introduction to the natural aquatic environment via the waste water treatment system. in addition, we posit that spillback of novel coronaviruses from the new wildlife hosts is also possible. thus, considering the current covid-19 pandemic, wastewater treatment plants and their surrounding environments should come under increased scrutiny for serving as a potential areas where spillover into wildlife hosts could occur. this was recently conducted in the netherlands where sars-cov-2 rna was found in sewage from wwtps servicing 6 cities and an airport (medema et al. 2020) . such scrutiny could integrate surveillance of key wildlife species, such as bats and raccoons, which have the potential for acquiring coronaviruses from their aquatic environments. an enhanced surveillance program of identifying sars-cov-2 spillover into wildlife would ideally involve 1) identifying "hotspot" municipalities with high human caseloads of covid-19, 2) identifying areas downstream from wwtp effluent releases, and 3) sampling target wildlife species, such as bats, mustelids, and j o u r n a l p r e -p r o o f 9 raccoons, for sars-cov-2 antibodies and viral presence. such an effort could be conducted in conjunction with sampling wwtp effluent as proposed by medema et al. (2020) . at this stage, a probabilistic risk assessment model would probably not be very informative because of the uncertainties of the mechanisms described here and the need to parameterize the pathways we propose. for example, most detection of coronavirus in fecal and environmental samples have focused on rna detection through pcr and has, generally, not documented infectivity. we argue that further research into our proposed pathways is warranted, especially because outbreaks of novel, zoonotic pathogens have epidemiological implications beyond just human-to-human transmission. bats and coronaviruses identification of viral pathogen diversity in sewage sludge by metagenome analysis fort lauderdale's foul sewage spills have killed fish. there's likely more damage survival of surrogate coronaviruses in water viral shedding and antibody response in 37 patients with middle east respiratory syndrome coronavirus infection detection of group 1 coronaviruses in bats in north america human coronaviruses: insights into environmental resistance and its influence on the development of new antiseptic strategies term sars coronavirus excretion from patient cohort genomic characterisation and epidemiology of 2019 novel coronavirus: implications for virus origins and receptor binding concomitant cryptosporidia, coronavirus and parvovirus infection in a raccoon (procyon lotor) presence of sars-coronavirus-2 in sewage jumping species-a mechanism for coronavirus persistence and survival release of infectious human enteric viruses by fullscale wastewater utilities effects of sewage effluent on the activity of bats (chiroptera: vespertilionidae) foraging along rivers bats and buildings: the conservation of synanthropic bats bats in the anthropocene: conservation of bats in a changing world emerging investigators series: the source and fate of pandemic viruses in the urban water cycle sars-cov-2 titers in wastewater are higher than expected from clinically confirmed cases prolonged presence of sars-cov-2 viral rna in faecal samples evidence for gastrointestinal infection of sars-cov-2 enteric involvement of coronaviruses: is faecal-oral transmission of sars-cov-2 possible? evidence of airborne transmission of the severe acute respiratory syndrome virus viral load dynamics and disease severity in patients infected with sars-cov-2 in zhejiang province the findings and conclusions in this publication are those of the authors and should not be construed to represent any official usda or u.s. government determination or policy. this key: cord-301067-wk3cf0b7 authors: corpus-mendoza, asiel n.; ruiz-segoviano, hector s.; rodríguez-contreras, sergio f.; yañez-dávila, david; hernández-granados, araceli title: decrease of mobility, electricity demand, and no2 emissions on covid-19 times and their feedback on prevention measures date: 2020-11-01 journal: sci total environ doi: 10.1016/j.scitotenv.2020.143382 sha: doc_id: 301067 cord_uid: wk3cf0b7 the spread of coronavirus disease 2019 (covid-19) on 2020 has affected human activities in a way never documented in modern history. as a consequence of the prevention measures implemented to contain the virus, cities around the world are experiencing a decrease in urban mobility and electricity demand that have positively affected the air quality. the most extreme cases for cities around the world show a decrease of 90, 40, and 70 % in mobility, electricity demand, and no2 emissions respectively. at the same time, the inspection of these changes along the evaluation of covid-19 incidence curves allow to obtain feedback about the timely execution of prevention measures for this and future global events. in this case, we identify and discuss the early effort of latin-american countries to successfully delay the spread of the virus by implementing prevention measures before the fast growth of covid-19 cases in comparison to european countries. as hypertension (shin et al., 2020) , cardiovascular disease (mann et al., 2002) , chronic pulmonary disease (euler et al., 1988) , and a diminished response to viral and bacterial infections (ciencewicki and jaspers, 2007) . moreover, it is also proposed that the same pollutants can participate directly in the transmission of covid-19 as a coronavirus carrier (bontempi, 2020; sasidharan, et al., wu et al., 2020; zoran et al., 2020) . however, this last observation is not yet demonstrated, since high levels of air pollutants are usually evident in cities with high human population and hence, high human interaction (pisoni and van dingenen, 2020) . therefore, in this article, we conduct a broad evaluation of the impact of the covid-19 pandemic on the urban mobility, electricity consumption, and no 2 emissions as a whole for several countries around the world rather than for a single region or sector affected as in previous literature. at the same time, we analyse the evolution of confirmed covid-19 cases and compare them with the start of prevention measures and changes in sectors affected in different countries to discuss the effectiveness in time in which they are applied. we think that the combination of these two approaches can not only explain how the pandemic affects human activities and the environment, but also how these changes allow us to obtain feedback of the prevention measures applied for this and future events. are obtained from the global health expenditure database (who ghed, 2020) . these datasets are used to find the date of the 100th covid-19 case (d 100 ) for each country in order to evaluate their daily incidence (i c ) and death incidence (i d ), which show the quantity of confirmed cases and deaths per 100000 habitants respectively. then, it is possible to obtain the incidence rate (i cr ) from the slope of i c versus time curve during the fastest infection period, as well as the threshold day (t d ) from the x-axis intercept of the slope, which estimates the quantity of days after d 100 in which the infection grows the fastest, as shown in fig. 1 for italy. this analysis of the i c curve is inspired by the evaluation of the turn-on voltage and series resistanc of electronic devices such as diodes, and it is a simple approach to assess and compare the evolution of i c between countries. here, i cr is useful to evaluate the spread speed of the virus, whereas t d identifies the moment in time in which fast growth starts. the combination of these parameters allow to estimate and discuss the effectiveness of the actions implemented to stop the spread of the virus, and to plan for future and similar events. however, the disadvantage of this method is its lagging nature, since the fast growth region of the i c curve is often confirmed at late stages of the pandemic. another dataset used is the #covid19 government measures dataset (acaps, 2020), which collects daily country-level data from news, social media, and articles about the prevention measures implemented around the world to fight the pandemic. these measures are classified in 5 categories in the original dataset, however, we reclassify them and discuss them in terms of their effects on health, and economy, but mainly on the environment by analysing changes in mobility, electricity generation, and air quality index (aqi) before and after the pandemic. here, the mobility around transit stations such as subway, bus, and train stations is selected as the parameter to study rather than mobility around residential areas, grocery shops and pharmacies, or retail and recreation areas since transit stations usually involve a high concentration of people. this information is obtained from the covid-19 community mobility reports by google (google, 2020) and presents the percentage change in the number of people visiting transit stations compared to a baseline level, which is the median value for each day of the week during january 3rd and february 6th, 2020. also, hourly and daily electrical power consumption is obtained for 26 countries from their respective transmission system operator (tso) in order to evaluate their daily percentage change in electrical energy consumption between march 1st and june 30th for 2019 and 2020. here, the daily data is adjusted to compare days of the week rather than dates. this adjustment is applied because power consumption during the weekends is usually different than during the weekdays. data for most european countries are available at the european network of transmission system operators for electricity (entsoe, 2020) , whereas other sources are j o u r n a l p r e -p r o o f journal pre-proof 8 used for italy (terna, 2020) , spain (red eléctrica de españa, 2020), russia (soues, 2020), uk (elexon, 2020), india (andrew, 2020 and posoco, 2020) , japan (tepco, 2020), singapore (ema, 2020), turkey (exist, 2020), bolivia (cndc, 2020), brazil (ons, 2020), chile (cen, 2020), colombia (xm, 2020), mexico (cenace, 2020), peru (coes, 2020), uruguay (adme, 2020), and usa (eia, 2020). finally, daily aqi index for no 2 measured by monitoring stations is analysed for 36 capital cities around the world to compare the percentage change between the first half of 2019 and 2020. here, we select capital cities assuming that they represent a significant amount of population and human activities affected by the pandemic. also, no 2 is chosen as the air pollutant to study instead of other pollutants such as co, co 2 , so 2 , pm 2.5 , or pm 10 , since most of the no 2 in cities is produced by combustion vehicles while driving, a common activity worldwide. these and other environmental data are available at the world air quality index project (waqip, 2020). j o u r n a l p r e -p r o o f another point to consider besides the development of the pandemic around the world is the impact that it has in modern life, since the execution of prevention measures implies an adjustment on the usual human activities, and therefore, the environment. some of the measures applied until now are classified as shown in fig. 4 , with many of them affecting more than one category. particularly, the mobility of people around transit stations is clearly lower in terms of percentage for all countries compared to their baseline levels at the beginning of the year, as shown in fig. 5 . also, the average mobility curves by continent reveal that the drop in mobility starts in the middle of march for europe, asia, and the americas, reaching levels of approximately -60% compared to the baseline, whereas the change in africa is lesser and later. however, there is a significant difference in the average d 100 by continents, since the average mobility curve in europe is still close to the baseline before its average d 100 . this means that the pandemic in that region had already started by the time mobility measures were applied, whereas some asian countries and most of the americas and africa had already restricted their mobility similarly to mobility, the electrical energy consumption around the world is also affected by the pandemic, as shown in fig. 6 , which reveals a decrease of the average electricity consumption curve by continents since the middle of march, 2020 compared to the values of 2019 despite people spending more time at their homes. therefore, we attribute this change to a decrease of industrial activity, closure or partial operation of transit stations and retail sector, as well as flexible times to work from home. fig. 6 also shows the dates in which some countries recommended or enforced their citizens to stay at home. these dates do not differ significantly between the nations analysed, which once again demonstrates an early action by most of latin-america. finally, the percentage change and absolute change in terms of gwh is shown in fig. 6d ), where it is observed that electricity consumption decreased in most countries analysed j o u r n a l p r e -p r o o f activities which are probably not heavily affected by the pandemic, which could explain the difference in electrical consumption compared to the other countries. supplementary material (fig. s2 ). finally, fig. 7 shows the percentage decrease in the aqi for no 2 , which is a measure of the air pollution by no 2 , where higher values represent a higher risk to health. particularly, the aqi for no 2 in cities depend mainly on the combustion of fossil fuels and therefore, driving. also, the aqi for this and other air pollutants is affected by the weather seasons, with winter slowing the dilution and dispersion of pollutants . this explains the decrease in the it is now observed that the prevention measures applied limited human activities and caused the decrease of urban mobility as well as electricity consumption, which led to a decrease of no 2 emissions. therefore, the appearance of the virus paradoxically had a positive effect on the air quality to the point that many authors consider the decrease of no 2 has saved more human lives than covid-19 has claimed (dutheil, 2020) . some studies now indicate that 24000 to 36000 premature deaths per month have been avoided in china due to an improved air quality , whereas the total covid-19 deaths in the same country are less than 5000. however, the reopening of human activities after the lockdown demonstrate that the improvement in air j o u r n a l p r e -p r o o f quality is unsustainable (zambrano-monserrate), since pollution levels are back to the normal trend compared to previous years (liu et al., 2021) . these observations should serve as the basis to design and implement actions oriented towards the improvement of human health and air quality, for example, traffic control, investment in public transportation, replacement of face-toface work with online work, renewable energy projects, electric vehicles infrastructure, and more. detailed data for rome, italy in the inset. philippines had an approximate 70% decrease of mean no 2 quality index for the period evaluated. details by country in supplementary material (fig. s3a and fig. s3b ). in summary, the adoption of prevention measures to mitigate the impact of covid-19 on human health has caused a decrease of mobility in transit stations as well as a decline in electricity demand around the world. as a consequence, the air quality has been positively j o u r n a l p r e -p r o o f affected as observed by the decrease of no 2 in multiple capital cities. therefore, these observations can be used to implement traffic control programs, investment in public transportation, replacement of face-to-face work with online work, electric vehicles infrastructure, and other green energy projects oriented towards the improvement of air quality and, therefore, human health. at the same time, the analysis of changes in mobility and electricity demand along the evaluation of t d and i cr from the i c curves allow to discuss the timely execution of the prevention measures, which works as a feedback to consider and plan actions for the current pandemic or future global events. here, it is observed that european the assessment capacities prpject. #covid19 government measures dataset administración del mercado eléctrico first confirmed detection of sars-cov-2 in untreated wastewater in australia: a proof of concept for the wastewater surveillance of covid-19 in the community india's daily electricity generation covid-19 lockdown effects on air quality by no 2 in the cities of barcelona and madrid (spain) changes in u.s. air pollution during the covid-19 pandemic understanding european network of transmission system operators for electricity energy exchange istambul. transparency platform covid-19: air pollution remains low as people stay at home. air qual the influence of covid-19 on air quality in india: a boon or inutile the short-run and long-run effects of covid-19 on energy and the environment covid-19 community mobility reports modified from original picture on freepik covid-19, city lockdowns, and air pollution: 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india association between road traffic noise and incidence of diabetes mellitus and hypertension in toronto, canada: a population-based cohort study amplified ozone pollution in cities during the covid-19 lockdown system operator of the unified energy system (системный оператор единой энергетической системы) last time accessed on jult 4 th severe air pollution events not avoided by reduced anthropogenic activities during covid-19 outbreak world air quality index project emergency committee regarding the outbreak of novel coronavirus (2019-ncov) who coronavirus disease (covid-19) dashboard world health organization. global health expenditure database last time accessed on spatiotemporal variations of air pollutants in western china and their relationship to meteorological factors and emission sources indirect effects of covid-19 on the environment assessing the relationship between ground levels of ozone (o3) and nitrogen dioxide (no2) with coronavirus (covid-19 writing -original draft, writing -review & editing. hector s. ruiz-segoviano: data curation, formal analysis, investigation, visualization, writing -review & editing. sergio f. rodríguez-contreras: data curation, formal analysis, investigation, visualization, writing -review & editing. david yañez-dávila: data curation, formal analysis, investigation, writing -review & editing. araceli hernández-granados: data curation, formal analysis, investigation, writing -review & editing ancm thanks the support of cátedras by consejo nacional de ciencia y tecnología key: cord-292045-pnid9dmq authors: kumar, manish; patel, arbind kumar; shah, anil v.; raval, janvi; rajpara, neha; joshi, madhvi; joshi, chaitanya g. title: first proof of the capability of wastewater surveillance for covid-19 in india through detection of genetic material of sars-cov-2 date: 2020-07-28 journal: sci total environ doi: 10.1016/j.scitotenv.2020.141326 sha: doc_id: 292045 cord_uid: pnid9dmq abstract we made the first ever successful effort in india to detect the genetic material of sars-cov-2 viruses to understand the capability and application of wastewater-based epidemiology (wbe) surveillance in india. sampling was carried out on 8 and 27 may 2020 at the old pirana waste water treatment plant (wwtp) at ahmedabad, gujarat that receives effluent from civil hospital treating covid-19 patients. all three, i.e. orf1ab, n and s genes of sars-cov-2, were found in the influent with no genes detected in effluent collected on 8 and 27 may 2020. increase in sars-cov-2 genetic loading in the wastewater between 8 and 27 may 2020 samples concurred with corresponding increase in the number of active covid-19 patients in the city. the number of gene copies was comparable to that reported in untreated wastewaters of australia, china and turkey and lower than that of the usa, france and spain. however, temporal changes in sars-cov-2 rna concentrations need to be substantiated further from the perspectives of daily and short-term changes of sars-cov-2 in wastewater through long-term monitoring. the study results sars-cov-2 will assist concerned authorities and policymakers to formulate and/or upgrade covid-19 surveillance to have a more explicit picture of the pandemic curve. while infectivity of sars-cov-2 through the excreted viral genetic material in the aquatic environment is still being debated, the presence and detection of genes in wastewater systems makes a strong case for the environmental surveillance of the covid-19 pandemic. the current ongoing global coronavirus disease pandemic, caused by the infection of severe acute respiratory syndrome coronavirus 2 (sars-cov-2), has spread to 216 countries and territories, with 7.7 million of the confirmed cases and more than 425,000 deaths worldwide, as of june 12, 2020 (who, 2020) . the active replication of infectious sars-cov-2 particles in enterocytes of human intestine due to expression of ace2 receptor causes shedding of virus in the faeces (lamers et al. 2020; qi et al., 2020) . the clinically reported symptoms in covid-19 patients mainly include cough, difficulty in breathing, fever and diarrhoea (gao et al., 2020; kumar et al., 2020a) . however, during a previous study of covid-19 patients, sars-cov-2 rna was detected in faeces more frequently than gastrointestinal symptoms (17%) such as diarrhoea (cheung et al., 2020) . these results suggest a large number of asymptomatic individuals along with symptomatic patients, discharge the virus which ultimately reaches sewage treatment plants (haramoto et al., 2020) . the virus can be shed in faeces for several days, even after the patient stops exhibiting respiratory symptoms . zheng et al., (2020) , reported detection of sars-j o u r n a l p r e -p r o o f disease outbreak in a certain catchment by monitoring viral load in the wastewater, as it contains excrement from both symptomatic and asymptomatic individuals (xagoraraki and o'brien, 2020; choi et al. 2018; yang et al., 2015) . wbe was an effective tool during past outbreak of other enteric viruses, such as poliovirus, hepatitis a and norovirus (hellmér et al., 2014; asghar et al., 2014; kitajima et al., 2020 , kumar et. al., 2020a , it can be used as an early warning tool for the disease outbreak in a community and used to inform the efficacy of the current public health interventions . wbe data can help estimate actual infected population due to the virus, as it also covers asymptomatic and presymptomatic the patients, which may be underestimated by clinical surveillance (bivinis et. al., 2020; tang et al., 2020; wölfel et al., 2020a; , kumar et al., 2020a . detection of, sars-cov-2 rna in wastewater has been reported in australia, china, france, israel, italy, japan, netherlands, spain and the us (ahmed et al., 2020a,b; bar-or et al., 2020; haramoto et al., 2020; la rosa et al., 2020; medema et al., 2020; nemudryi et al., 2020; randazzo et al., 2020; rimoldi et al., 2020; wurtzer et al., 2020 , kumar et al., 2020c . according to some of these studies, after the number of confirmed cases reached to 1-100 per million population, sars-cov-2 rna was detected in wastewater (ahmed et al., 2020a; bar-or et al., 2020; medema et al., 2020; nemudryi et al., 2020; wurtzer et al., 2020 , kumar et al., 2020d . to date of submission of this work, there is no study reporting detection of sars-cov-2 in wastewater in india. as of june 12, 2020, the number of confirmed cases in india was 223 per million population. the first case of covid-19 in india was reported on january 30, 2020 and the number of confirmed cases has reached more than 300,000 as of june 12, 2020 (ministry of health and family welfare, india). the state of gujarat has reported >22,500 confirmed cases of covid-19, as of june 12, j o u r n a l p r e -p r o o f 2020, with >12,000 confirmed cases in ahmedabad city (ministry of health and family welfare, india). to further understand the capability and potential application of wbe surveillance, we made the first successful detection of genetic material of the sars-cov-2 virus in india. we also analysed the temporal variation in genetic material loadings in the same wastewater treatment plant during a lockdown period in india. finally, we evaluated the effect of traditional treatment systems on sars-cov-2 genetic material and aim to assist concerned authorities and policymakers to formulate and/or upgrade covid-19 surveillance to include an explicit picture of the pandemic curve. wastewater samples were collected on 8 and 27 may, 2020 from the old pirana waste water treatment plant (wwtp) at ahmedabad, gujarat which is the largest wastewater treatment plant in asia with a capacity of >180 m 3 /day. the wwtp is equipped with an upflow anaerobic sludge blanket (uasb) as an advanced process to treat the wastewater. this wwtp is designed to produce treated water with ph, biological oxygen demand (bod), total suspended solids (tss), and chemical oxygen demand of 7-8.5, <20 mg.l -1 , <30 mg.l -1 and <100 mg.l -1 respectively. the sampling location for this study was selected based on the fact that pirana wwtp receives the sewage waste of a government civil hospital treating covid-19 patient. to ensure accuracy and precision, duplicated analyses of the samples were also performed for a raw wastewater, in which the reproducibility was fairly high (average c t difference of 1.2). several blanks were prepared and run to check the cross-contamination, and sensitivity of the protocol, extraction and instrumentation. all analyses were conducted at the indian council of medical research (icmr), new delhi, an approved facility of the gujarat biotechnology research centre (gbrc). viral rnas were isolated from sewage samples using following steps: precipitation of viral particles; viral rna isolation and quality checking. the sewage samples (50 ml) were centrifuged at 4500×g (model: sorvall st 40r ,thermo scientific) for 30 min followed by filtration of supernatant using 0.22 micron filters (mixed cellulose esters syringe filter, himedia). each sewage filtrate was then concentrated using the poly ethylene glycol (peg) methods. for this method, peg 9000 (80 g/l) and nacl (17.5 g/l) were mixed with 25 ml filtrate and this was incubated overnight at 17°c and 100 rpm (model: incu-shaker tm 10lr, benchmark). the following day the mixture was centrifuged at 13000×g (model: kubota 6500, kubota corporation) for 90 mins. after centrifugation, the supernatant was discarded and the pellet resuspended in 300 µl rnase-free water. this was further used as a sample for rna isolation. rna isolation was carried out using a commercially available kit (nucleospin ® rna virus, macherey-nagel gmbh & co. kg, germany). concentrated viral particles (200 µl) were mixed with 10 µl ms2 phage, 20 µl proteinase k (20mg/ml) solution and 600 µl of rav1 buffer containing carrier rna. here, ms2 phage was taken as a molecular process inhibition control (mpc; haramoto et al 2018) for evaluating the efficiency of nucleic acid extraction and pcr inhibition. it is to be noted that ms2 may naturally occur in wastewater, it is therefore there is possibility that recovered ms2 may consist both the spiked and background viral content. further steps were carried out as instructed in the product manual (macherey-nagel gmbh & co. kg). final elution was carried out with 30 µl of elution buffer (provided by kit). rna concentrations were determined using a qubit 4 fluorometer (invitrogen). j o u r n a l p r e -p r o o f rnas were analysed for the detection of orf1ab, n gene and s gene of sars-cov-2 and ms2 (internal process control) by rt-pcr using taqpath tm covid-19 rt-pcr kit (applied biosystems). amplification was performed in a 25 μl reaction mixture containing 7 μl extracted nucleic acids of each samples. positive control (2 μl) (taqpath™ covid-19 control) and purified negative control (5 μl) were used in case of positive and negative control respectively. nuclease free water was used as no template control in this study. further procedures were carried out as described in product manual. rt-pcr experiment consisted of ung incubation at 25°c for 2 min, reverse transcription at 53 °c for 10 min and activation at 95 °c for 2 min, followed by 40 cycles, each involving denaturation at 95 °c for 3s followed by annealing/extention at 60 °c for 30s. the reactions were performed in applied biosystems™ 7500 fast real time pcr system (applied biosystem), and interpreted as instructed in the manual. although there is no direct correlation of the c t value to copy numbers as the kit used for the detection is qualitative assay yet we put an effort to calculate number of gene copies present in a unit volume of the sample. for this the well-established principle of 3.3 c t change corresponds to 10-fold change has been used. more precisely, 500 copies of sars-cov-2 genes were taken as positive control with c t of average 26 for all the three genes i.e. orf1ab, n and s, which were then extrapolated to compare it with sample c t values and derive approximate copies of genes in the wastewater sample. the amount of rna used as template was multiplied with the enrichment factor to derive an estimated copy numbers for each wastewater sample. table 1 shows the number of active cases for the city i.e. ahmedabad and india, obtained by deducting recovered cases from total confirmed cases since 17 march, 2020. consistency between abundance of sars-cov-2 genetic materials and number of confirmed cases was observed in the previous reports in australia, france, italy, spain and japan further, referring to the limitations of the present study owing to lockdown scenario, we recommend that although based mpc analysis, the efficiency of rna extraction and rt-pcr is considered high for all the wastewater samples collected for this study, the efficiency of peg method could have been better established. further, based on indigenous f-phage analysis hata et al., (2020) reported a high efficiency of peg method in japanese wastewater, yet an evaluation of sample concentration efficiency, using the whole process control (wpc) together with mpc is recommended (haramoto et al 2018) . we recommend longer monitoring with several replicated analyses to evaluate the correlation as well as uncertainties involving rt-pcr (stuart et al 2014) and then replace the semi-quantitative method employed in this study with precise copy calculations using suitable methods. nevertheless, the bottom line is that the patterns of obtained c t values suggest successful detection of sars-cov-2 rna from the wastewater samples, their increasing abundance together with an increase of covid-19 confirmed cases, and their reduction by uasb treatment and aeration pond. in summary, results demonstrated the capability of wastewater-based epidemiology in indian settings and strongly advocates that despite the lack of quality sewer infrastructure or other wastewater collection issues, wbe can be applicable and thus we strongly implementing environmental surveillance of the cvoid-19 pandemic in india, starting with major cities. while the world is providing high resolution proofs of the wbe concept, india needed indigenous proof of concept and its applicability. in this context, we achieved two major outcomes: i) for the first time in india and top 10 efforts in the world, we isolated sars-cov-2 genetic material and detected it during a lockdown period owing to good coordination among the government organizations; ii) temporal variation in ct value demonstrated the capability of wbe surveillance in india; and iii) for the third time in the world treated water was analysed for the presence and confirmation of sars-cov-2 genetic material. the results were of good resolution and provided significant indication of temporal variation in covid-19 patient loadings. however, owing to limited samples analysed in this preliminary study, even though the case numbers align with increased rna concentrations in wastewater, the temporal changes in sars-cov-2 rna concentrations needs to be further investigated from the several perspectives of daily, short-term and long-term changes. our results demonstrated that a conventional treatment plant is capable of removing genetic materials j o u r n a l p r e -p r o o f of sars-cov-2, however there may not be the complete elimination. in a country like india where sewer systems are not complete and only a part of the waste is received at wwtps, it is essential to study each treatment stage to determine the effectiveness of treatment. this will help reduce the commonly perceived fear of the commons pertaining to the effectiveness of treatment plants as well as transmission through wastewater. the authors declare no competing financial interest. j o u r n a l p r e -p r o o f zhang, w., du, r.h., li, b., zheng, x.s., yang, x. lou, hu, b., wang, y.y., xiao, g.f., yan, b., shi, z.l., zhou, p., 2020a . molecular and 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correlates with covid-19 confirmed cases wastewater-based epidemiology for early detection of viral outbreaks community sewage sensors for monitoring public health we acknowledge the unimaginable support from every corner as naming all of them involved or helped during analyses or sampling or protocol development would be difficult. special key: cord-277490-xrgnt6l5 authors: huang, zhongwei; huang, jianping; gu, qianqing; du, pengyue; liang, hongbin; dong, qing title: optimal temperature zone for the dispersal of covid-19 date: 2020-05-16 journal: sci total environ doi: 10.1016/j.scitotenv.2020.139487 sha: doc_id: 277490 cord_uid: xrgnt6l5 abstract it is essential to know the environmental parameters within which the severe acute respiratory syndrome coronavirus 2 (sars-cov-2) can survive to understand its global dispersal pattern. we found that 60.0% of the confirmed cases of coronavirus disease 2019 (covid-19) occurred in places where the air temperature ranged from 5 °c to 15 °c, with a peak in cases at 11.54 °c. moreover, approximately 73.8% of the confirmed cases were concentrated in regions with absolute humidity of 3 g/m3 to 10 g/m3. sars-cov-2 appears to be spreading toward higher latitudes. our findings suggest that there is an optimal climatic zone in which the concentration of sars-cov-2 markedly increases in the ambient environment (including the surfaces of objects). these results strongly imply that the covid-19 pandemic may spread cyclically and outbreaks may recur in large cities in the mid-latitudes in autumn 2020. j o u r n a l p r e -p r o o f 3 through aerosols, which can be produced by speaking at a normal volume (anfinrud et al., 2020) . in addition, it is found that sars-cov-2 can stay for a considerably long time in the air. the aerodynamic characteristics and propagation of sars-cov-2 in aerosols have been reported (liu et al., 2020) . it was reported that sars-cov-2 was still found in the diamond princess cruise ship 17 days after people disembarked. therefore, it is essential to understand the survival of sars-cov-2 in the ambient environment to prevent covid-19. this information is very useful not only for the policymakers but also for the general population. visualizing speech-generated oral fluid droplets with laser light scattering the effect of travel restrictions on the spread of the 2019 novel coronavirus (covid-19) outbreak the global oxygen budget and its future projection transmission of 2019-ncov infection from an asymptomatic contact in germany sars-cov-2 rna found on particulate matter of transmission of a 2009 pandemic influenza virus shows a sensitivity to temperature and humidity similar to that of an h3n2 seasonal strain evidence that higher temperatures are associated with lower incidence of covid-19 in pandemic state, cumulative cases reported up to a seasonal model to simulate influenza oscillation in tokyo association between ambient temperature and covid-19 infection in 122 cities from china key: cord-305262-23qylbmg authors: rowan, neil j.; laffey, john g. title: unlocking the surge in demand for personal and protective equipment (ppe) and improvised face coverings arising from coronavirus disease (covid-19) pandemic – implications for efficacy, re-use and sustainable waste management date: 2020-09-10 journal: sci total environ doi: 10.1016/j.scitotenv.2020.142259 sha: doc_id: 305262 cord_uid: 23qylbmg currently, there is no effective vaccine for tackling the ongoing covid-19 pandemic caused by sars-cov-2 with the occurrence of repeat waves of infection frequently stretching hospital resources beyond capacity. disease countermeasures rely upon preventing person-to-person transmission of sars-cov2 so as to protect front-line healthcare workers (hcws). covid-19 brings enormous challenges in terms of sustaining the supply chain for single-use-plastic personal and protective equipment (ppe). post-covid-19, the changes in medical practice will drive high demand for ppe. important countermeasures for preventing covid-19 transmission include mitigating potential high risk aerosol transmission in healthcare setting using medical ppe (such as filtering facepiece respirators (ffrs)) and the appropriate use of face coverings by the general public that carries a lower transmission risk. ppe reuse is a potential short term solution during covid-19 pandemic where there is increased evidence for effective deployment of reprocessing methods such as vaporized hydrogen peroxide (30 to 35% vh2oh) used alone or combined with ozone, ultraviolet light at 254 nm (2000 mj/cm2) and moist heat (60 °c at high humidity for 60 min). barriers to ppe reuse include potentially trust and acceptance by hcws. efficacy of face coverings are influenced by the appropriate wearing to cover the nose and mouth, type of material used, number of layers, duration of wearing, and potentially superior use of ties over ear loops. insertion of a nose clip into cloth coverings may help with maintaining fit. use of 60 °c for 60 min (such as, use of domestic washing machine and spin dryer) has been advocated for face covering decontamination. risk of virus infiltration in improvised face coverings is potentially increased by duration of wearing due to humidity, liquid diffusion and virus retention. future sustained use of ppe will be influenced by the availability of recyclable ppe and by innovative biomedical waste management. since first reported as a cause of serious human pneumonia in wuhan, hubei, china in december 2019, the novel coronavirus covid-19 has spread worldwide with devastating consequences. at the time of writing (29 th august, 2020), there has been 25.1 million cases of covid-19 reported (in accordance with the applied case definitions and testing strategies in the affected countries) including 845,343 deaths (european centre for disease control and prevention, 2020) . there is evidence of resurgence of the sars-cov-2 globally with the emergence of second waves of infection in many countries (european centre for disease control and prevention, 2020) . hong kong is addressing its third wave of infections, where australia is battling a second wave of infection having previously reduced viral transmission cases close to zero. covid-19 has also emerged strongly in developing low-resource countries that already have significant healthcare challenges, such as across the african continent that is also challenged with acquired immunodeficiency syndrome (aids) and mycobacterium tuberculosis as co-morbidities (african centre for disease control and prevention, 2020) . currently, there is still no effective vaccine or anti-viral therapy for covid-19 with reliance upon the prevention of transmission by way of imposing a lockdown, cocooning, social distancing, and wearing of face masks in order to protect vulnerable groups and to safeguard frontline healthcare professionals. epidemiological studies show that social distancing prevents person-to-person transmission of sars-cov-2, which is relevant given that there is growing recognition that asymptomatic carriers may also contribute to this transmission (li et al., 2020) . there is evidence to suggest that covid-19 is a super-spreader of infectious airborne viral particles where several people can be infected at the same time (li et al., 2020) . publication from 1 january 2003 (as the first recorded human infection of sars-1 occurred in november 2002 (as per derraik et al., 2020) and 8 august 2020. titles and/or abstracts were screened by the first author and where appropriate, full text of individual research studies, opinion pieces and reviews were consulted. key words used were ppe; reuse; reprocessing; disinfection; decontamination; n95; covid-19; sars-cov-1; sars-cov-2; uv; hydrogen peroxide vapour (vh2o2); ozone; waste management; recycling. data extraction and rapid analysis was supplemented by conducting a short observation study where the first author noted the types of facemasks and face coverings worn by the public on entering a large shopping centre in the republic of ireland on 14 th and 15 th august 2020. at the time of initial writing (3 rd april, 2020) (rowan and laffey et al., 2020) , the number of confirmed covid-19 cases had reached 1 million, including 51,515 deaths, which highlights that a 25-fold increase in the prevalence of sars-cov-2 has occurred in only 4 months (european centre for disease prevention and control, 2020) . rowan and laffey (2020 had predicted an unprecedented high demand for ppe across the globe and therefore, it was prudent to consider ppe reuse as a potential option to meet the critical shortage in the supply chain for frontline hcws. rowan and laffey (2020) intimated that the structure of sars-cov-2 is such that is sensitive to harsh environmental stresses. moreover, the structure of sars-cov-2, and related coronaviruses, includes a rna genome, a protein capsid, and an outer envelope. viral inactivation is linked to the alteration of one of these structural elements by an environmental stress, such as, heating, ultraviolet light, and biocides (bentley et al., 2016; pinon and vialette, 2018; gorbalenya et al., 2020) . the proteins and lipids of the (li et al., 2016) , is such that these viruses are more likely to be sensitive to disinfection technologies (pinon and vialette, 2018; rowan and laffey, 2020) . kampf et al. (2020) had also analysed 22 studies of different human coronaviruses where sars, mers, hcov (but not including were efficiently inactivated by disinfection on variety of contact surface using 62 to 71% ethanol, 0.5% hydrogen peroxide, or 0.1% sodium hypocholorite within 1 min of exposure, but survived on untreated surfaces for up to 9 days. van doremalan et al. (2020) also conducted tests that showed that sars-cov-1 remains on plastic, stainless steel, copper and cardboard for up to 72 h. these and other studies have informed selection of many current disinfection procedures to address sars-cov-2 pandemic, including ppe reuse. given that disposable, plastic-based, ppe (gowns, eye protection, gloves, face masks, filtering facepiece respirators (ffrs)) are heat sensitive, existing healthcare technologies were considered to be either not available, unsuitable or not configured for reprocessing of ppe in healthcare for emergency use (rowan and laffey, 2020) . however, potential solutions for effective reprocessing of ppe that considered virus inactivation, material compatibility and device functionality (filtration efficacy, penetration, fit test and so forth) post processing included use of low temperature hydrogen peroxide vapour (vh2o2), ultraviolet germicidal light (uvgi), moist heat, and use of weak bleach for liquid decontamination (rowan and laffey, 2020; cdc, 2020) . mcevoy and rowan (2019) had published a comprehensive review on the background and efficacy of vh2o2 for terminal sterilization of medical devices that was used to provide supportive technical information in choice of procedures. this information was supported by prior findings of bentley et al. (2016) who reported on 4 log 10 viral titre reductions for the recalcitrant naked norovirus in a variety of hospital settings (stainless steel, glass, vinyl flooring, ceramic tile, pvc plastic cornering) using 30% w/w hydrogen peroxide vapour. rowan (2019) had also reviewed potential microbial mechanistic information underpinning uv disinfection that also provided supportive foundation knowledge for the potential use of pulsed light technology for ppe. journal pre-proof information underpinning these candidate technology solutions included best-published information of efficacy of these approaches to surface disinfection cornoavirus or related viruses and surrogate biological indicator organisms on different surface materials (kampf et al., 2020) . the fda had authorised use of vh2o2 technology, under emergency use authorization (eua), for the reprocessing of critical n95 face masks in the united states in order to help address covid-19 transmission. this was informed by columbus-based battelle process studies (battelle, 2016) . given exceptional circumstances, original equipment manufacturers (oems) of ppe had also suggested possible appropriate reprocessing strategies, but they also reiterated that their products had been manufactured with the sole intention of single use. the contingency plan to be adopted in hospitals on the west of ireland was to procure, install and seek approval from competent authority for the deployment of vh2o2 (bioquell bq50 system) for filtering face-piece respirators (ffrs) and surgical gowns, uv technologies (nanoclave low-pressure uvgi system and claranor pulsed light system) for simple ppe such as face shields, and use of mild sodium hypochlorite (4000ppm) for liquid decontamination of critical starmed hoods. the vh202, uvgi and mild liquid disinfection strategies have been set up, but there remains a requirement to gain trust and confidence by hcws for ppe reuse post treatments. several authors have reported on the viability of sars-cov1 and sars-cov-2 on various contact surface such as printed paper, printed tissue, cloth, wood, glass, banknotes, plastic, stainless steel, surgical mask layers over different environmental temperatures, relative humidity and durations (li et al., 2003; lai et al, 2005; pagat et al., 2007; chan et al., 2020; chin et al., 2020; fischer et al., 2020; kasloff et al., 2020; behzadinsaab et al., 2020; biryukov et al., 2020) . in general, lower environmental temperatures support the longer survival of sars-cov-2 on materials as reported by chin et al. (2020) where only a 0.7 log 10 reduction was observed for sar-cov-2 at 4°c after 14 days compared with 4.5 log 10 reduction at 22°c (room temperature) after 14 days and 4.5 log reduction at 37°c after just 2 days. similarly, also noted only a 2 log 10 reduction of sars-cov-1 at 4°c after 14 days when the virus was inoculated onto glass surfaces. the longer survival of sars-cov-2 at colder temperatures may have future implications for viral persistence on contaminated face coverings as we are approaching the winter flu season. however, public health practices that have been put in place to mitigate the spread of sars-cov-2 are likely to have a positive impact on the occurrence of influenza cases given that these viruses share similar modes of transmission to cause illness. derraik et al. (2020) comprehensively reported on the viability of sars-cov-1 and sars-cov-2 on different contact surfaces, without and with uv or heat treatments, and noted the importance of virus load and inoculum size on inactivation performance. lai et al. (2005) , who looked specifically at ppe, highlighted the variability in sars-cov-1 viability of 2 days on a disposable polypropylene gown and 24 h on a cotton gown for same 6 log 10 reduction. akin to studies reported by derraik et al. (2020) , we also observed that the majority of researchers used medium tissue culture infective dose (tcid 50 ) to report inactivation of sars-cov-1 and sars-cov-2 on various surfaces. kasloff et al. (2020) (rowan and laffey, 2020) . there is also a pressing need to explore attitudes, perceptions and possible barriers for use of reprocessed ppe by frontline clinicians and nurses that would entail conducting a social marketing study so as to inform overall acceptance and to overcome behaviour change factors for ppe reuse. increased use of face masks by people in communities in irish society is aligned with similar recommendations in other countries across the globe (rubio-romero et al., 2020; holland et al., 2020; jansson et al, 2020) . who (2020) also advocate that "use of face masks alone are insufficient to provide adequate level of protection, and other measures should also be adopted". who (2020) also advises for each country to apply a risk-based approach that considers benefits (such as reduction of potential risk of exposure), along with potential risk (such as self-contamination, false sense of security, impact of ppe shortage) when deciding to use facemasks by general population. the centre for disease control and prevention (2020) a short observational study of the types of face masks and face covering used by 1043 shoppers as they entered a large retail centre was conducted in the irish midlands on 14 th and 15 th august, 2020. findings revealed that 461 wore coverings with ear loops, 320 wore procedural masks with elastic ear loops, 140 wore kn95/n95 respirators, 38 wore face shields, 5 wore bandanas, 3 wore scarfs, and 56 shoppers did not wear face coverings. there was no evidence of anyone using surgical masks secured with ties. it was observed that 64 appeared to be wearing face masks or coverings over their mouth only, or below their chin, or j o u r n a l p r e -p r o o f were improperly fitting such that these did not cover the nose or mouth. some shoppers removed their face masks, or raised their face shields to the top of their head, in order to have conversations, which indicated a lack of understanding of their purpose and function. recnet evidence from fischer et al. (2020) with ffrs suggests that face masks and face coverings should consider use of adjustable cloth ties, as this design potentially offers better filtration efficacy of the virus compared to using a face coverings that have elasticated ear loops. creativity in the design of cloth coverings was observed including insertion of a clear panel to facilitate lip reading. face cloths are likely to be disinfected through use of domestic washing machine for re-use where combination of moist heat above 60°c and detergent will kill covid-19 rubio-romero et al., 2020) . . cdc (2020b) report that it is not known if face shields provide any benefit as source control to protect others from the spray of respiratory particles. cdc does not recommend use of face shields for normal everyday activities or as a substitute for cloth face coverings. if face shields are used without a mask, they should wrap around the sides of the wearer's face and extend to below the chin. (cdc, 2020; rowan and laffey, 2020) . some studies have been reported on the use of different regimes of heating for ppe processing. heating causes irreversible structural damage in virus proteins that prevents binding to host cells (derraik et al., 2020) ; the challenge is for thermal procedures is to eliminate sars-cov-2 with damaging ppe. the guiding principle, similar to the concept of pasteurization for use with heat sensitive foods, is that one can achieve a similar one-log reduction in viral load by reducing exposure time with increasing temperature. for example use 72°c for 15 seconds provides similar level of lethality to that of using a holding temperature of 60°c for 30 min. in general, heat treatment at 60°c for 30 min would lead to ca 4.6 to 7 log 10 reduction in sars-cov-2 (table 1) . however, doubling exposure duration at 60°c to 60 min would be prudent given the variability in heat inactivation studies reported j o u r n a l p r e -p r o o f for sars-cov-1 and sars-cov-2 (derraik et al., 2020) . for example, darnell and co-workers (2004) reported on residual infectivity after exposure of sars-cov-1 to heating at 65°c for 90 min. also, there is considerable variability in the manner by which the viruses have been tested by researchers that includes use of artificial solutions, surfaces and materials, with and without soiling, where the lack of harmonized procedures makes it challenging to appreciate significance of findings and relevance to practice, such as ppe (table 1) . variable factors influencing the efficacy of heat inactivation procedures for sars-cov-1 and sars-cov-2 include number of viruses present (viral load), presence of organic matter (soiling), temperature, humidity and duration of treatment (table 1) . song and co-workers (2020) reported on the use of heating of face masks in an oven at 56°c for 30 min combined with hot air from a hair dryer for 30 min to inactivate influenza virus without observing efficacy in filtering capacity. rubio-romero et al. (2020) noted that findings from this particular study was used by the international medical centre of beijing (2020) ffrs maintain their filtration efficiency after decontamination at 70°c for 30 min, although fit and deformation testing is not reported. price and chu (2020) and spanish society of preventive medicine, public health and hygiene (2020) recommend use of dry heat at 70°c for 30 min in a convection oven to ensure constant and uniform temperature maintenance. however, there is a general lack of information on the effect of dry heat on filtration, fit-test or deformity over several decontamination cycles (n95decon, 2020; rubio-romero et al., derraik et al., 2020) . the cdc (2020) stated that, based on limited research available as of april 2020, moist heat has shown promise as a potential method to decontaminate ffrs. the cdc's national institute for occupational safety and health (2020) reiterated that before using any decontamination method, it should be evaluated for its ability to retain 1) filtration performance, 2) fit characteristics achieved prior to decontamination, and 3) safety of the ffr for the wearer (e.g. by inactivating sars-cov-2). moist heat, consisting of 60°c and 80% relative humidity (rh) caused degradation in the filtration and fit performance of tested j o u r n a l p r e -p r o o f ffrs [berman et al., 2010; bergman et al., 2011; viscusi et al., 2011] . heimbuch et al. (2011) disinfected ffrs contaminated with hini influenza using moist heat of 65°c and 85% rh that achieved a minimum of 99.99% reduction in the test virus. cdc (2020) noted that one limitation of the most heat method is the uncertainty of disinfection efficacy for various pathogens. this is particularly relevant as there could be more than one respiratory virus or pathogen on contaminated ffrs in healthcare environment and during covid-19 pandemic. ozone can disrupt lipids and proteins in the cell envelope of viruses exposing vital genetic material, thus causing oxidative inactivation (rowan, 2019) . zhang et al (2004) had previously reported on decontamination of ffp respirators using ozone where sars-cov1 was inactivated using different concentrations of ozone solution disinfection with efficacy at 27.73 mg/l for 4 min exposure., toon (2020) also described the efficacy of ozone for decontaminating ppe where the relative humidity needed to be maintained above 50%, dennis et al. (2020) reported virucidal potentialof ozone where they implemented a simple disinfection-box system for treating ffrs. the authors recommended ozone concentrations at 10 to 20 ppm combined with an exposure of at least 10 min. dennis et al. (2020) note advantages of ozone that include rapid virucidal action that is effective for fibrous material, which included addressing crevices and shading. however, there is very limited information on ozone for broader ppe and medical device treatment due possibly to risk associated with its volatility. the majority of authorised approaches advocated by competent bodies deploy hydrogen peroxide vaporization (vh2o2) for emergency reprocessing of ppe where there is critical shortage (table 1) . jatta et al (2020) rowan and laffey, 2020) . the background and benefits of using vh2o2 as a reprocessing agent or sterilising modality for medical device application have been comprehensively reviewed by mcevoy and rowan, 2020. however, vh2o2 compatibility with cellulose-based materials in ppe needs consideration . grossman et al. (2020) noted that several vh2o2 sterilisation systems are currently approved for use under emergency use authorization (eua), but these technologies can be difficult to obtain due to the significant demand around the world. grossman and co-authors (2020) described the vh2o2 process (closed and sealed off room using bioquell z-2 disinfection cycle) for n95 respirators. these ffrs had been placed in tyvck pouches where the process includes conditioning, gassing, dwell, and aeration of the vh2o2. grossman and co-workers (2020) demonstrated a reproducible and scalable process for decontaminating n95 respirator within a large academic hospital and healthcare system. the cdc (2020) all phages which was below the limit of detection. viscusi et al. (2009) found that 9 ffr models (three particulate n95, three surgical n95 ffrs and three p100) exposed to one cycle j o u r n a l p r e -p r o o f of vh2o2 treatment using the sterrad 100s h2o2 gas plasma sterilizer (advanced sterilization products, irvine, ca) had filter aerosol penetration and filter airflow resistance levels similar to untreated models; however, bergman et al. (2010) found that three cycles of gas plasma treatment using the sterrad 100s h2o2 gas plasma sterilizer negatively affected filtration performance. table 1 lists the most frequently published papers on the decontamination of reuse of ppe using vh2oh. the cdc (2020) reported that ethylene oxide (eo) is not recommended as a decontamination method for ffrs as it is carcinogenic and teratogenic and may be harmful to the wearer, even at very low concentrations. niosh set a low exposure limit due to residual cancer risk below the quantitative limits of detection, i.e, preferring lowest feasible exposure (cdc, 2020). the cdc reviewed several studies where eo was shown to not harm filtration performance for the 9 tested ffr models. all tests were conducted for one hour at 55°c with eo gas concentration ranging from 725 to 833 mg/l viscusi et al., 2009; bergman et al., 2010) . also, six models that were exposed to three cycles of 736 mg/l eto all passed the filtration performance assessment (bergman et al., 2010) . ultraviolet (uv) irradiation causes inactivation of viruses by damaging rna or dna via a photo-dimerization process (darnell et al., 2004 the cdc (2020) also noted that ultraviolet germicidal irradiation (uvgi) is a promising method for ppe reuse, but stated that not all uv lamps provide the same intensity, thus treatment times would have to be adjusted accordingly (table 2) . moreover, uvgi is unlikely to inactivate all the viruses and bacteria on an ffr due to shadow effects produced by the multiple layers of the ffr's construction. the cdc (2020) noted that acceptable filtration performance was recorded for eleven ffr models exposed to various uv doses ranging from roughly 0.5-950 j/cm 2 and uvgi was shown to have minimal effect on fit. card et al. (2020) reported on the potential efficacy of ffp respirator decontamination using uvgi using biosafety cabinets that describes irradiation for 15-20 min per side with a fluence of 100 w/cm 2 . lowe et al. (2020) (2020) also advocates against use of uv disinfection of filtering facepiece respirators due to "shadowing effects produced by the multiple layers of the filtering respirators construction". rubio-romero et al. (2020) noted that the advantages of uv could be that  j/cm 2 of uv-c inactivates viruses similar to sars-cov2 on n95s that maintain fit and filtering performance after 10-20 cycles but shadowing may affect disinfection efficacy (n95descon, 2020c). straps also become degraded after multiple cycles of uv (mills et al., 2018) . table 3 . there has been a staggering increase in the production of ventilators and supply of single-use ppe to meet unprecedented demands globally (health products regulatory authority, 2020; global news wire, 2020). cocking (2020) (2020) platforms that will meet need for accelerate rate of usage so as to ensure no undue risks aligned with bringing together multi-actors, particularly competent authorities/regulators. there is a commensurate need for an understanding of the appropriateness and impact of different reprocessing modalities on materials when considering future reprocessing of ppe and medical devices (rowan and laffey, 2020) . there is an unprecedented surge in plastic-based ppe usage, arising a s consequence from the ongoing covid-19 pandemic, which constitutes a new form of single-use-plastic (sup) waste that will to plague our oceans posing a threat to our marine ecosystems (euronews, 2020) . shorelines have been littered with discarded ppe, such as masks and visors, with the gullets of birds stuffed with latex gloves, along with crabs tangled in face masks. marine conservation organisation oceansasia highlighted the growing number of single-use face masks being discovered during its plastic pollution research in the soko islands near hong kong (clark, 2020) . to provide context, republic of ireland is a small country with a population of ca 4.5 million, yet it's hcws require 9 million face masks per week at a cost to the exchequer of €1billion a year (farsaci, 2020) . nzediegwu and chang (2020) . the world health organization (2020) projected that supplies of ppe must increase 40% monthly to deal effectively with covid-19 pandemic. essential ppe includes an estimated 89 million medical masks, 76 million pairs of medical gloves and 1.6 million pairs of goggles. the increased demand for ppe is expected to be sustained beyond covid-19 with an estimated compound annual growth of 20% in facial and surgical masks supply from 2020 to 2025 . it is noteworthy that china produced 240 tons of medical waste daily during peak of pandemic in wuhan (singh et al., (2020) . horton and barnes (2020) reported that microplastics have now been found in the most remote places on earth, far away from human activities. in addition with climate-induced stress, microplastics may lead to enhanced multi-stress impacts, potentially affecting the health and resilience of species and ecosystems. the impact on ppe contamination on the marine environment has yet to be determined where there is significant gaps in knowledge. indiscriminate use and inappropriate disposal or mismanagement sups that have low biodegradation have led to accumulation of plastic debris in terrestrial and aquatic ecosystems globally . this will affect natural biota, agriculture, fisheries along with threatening human and animal health (jambeck et al., 2015) . despite recent progress made in plastic sustainability and waste management, silva et al. (2020) have noted widespread drawbacks in the use and management of plastics in the fight against covid-19 pandemic that area associated with government imposed partial and total lockdown of cities/regions/municipalities that has promoted greater use of sups, including ppe, by the general public and healthcare workers (tobías, 2020) . there has also been a shift towards mandatory use of ppe by the general public, along with frontline healthcare workers j o u r n a l p r e -p r o o f where silva et al. (2020) noted that over 50 countries are mandated to wear masks in public places. there is also a commensurate need for increased production of ppe globally. world health organisation (2020) had expressed concerns about use of masks by general public due to lack of correct handling, and disposal, and the shortage of this material in healthcare materials. silva et al. (2020) noted that surgical masks should not be worn longer than a few hours (such as 3 h) and should be appropriately discarded to avoid cross-contamination (i.e., in a sealed plastic bag). however, incorrect disposal of ppe is widespread and has been found in several public places and natural environments ngo oceans asia, 2020) . observed that masks are likely to degraded into smaller microplastic pieces as are made from nonwoven materials (e.g., spunbond and meltdown spunbond) often incorporating polypropylene and polyethylene. these authors also noted that significant enhancement in the usage of ppe and other sups is likely to result in an overload increase in waste generation that would disrupt viable options for effective waste management. many countries have classified all such hospital and household waste potentially contaminated with sars-cov2 as infectious that should be incinerated under high temperature (ensuring sterilization), followed by landfilling of residual ash (european commission, 2020; silva et al., ilyas et al., 2020) . ilyas and co-workers (2020) reviewed, and reported on the merit, of developing different disinfection technologies for handling covid-19-generated waste from separate collection to using various physical and chemical steps with view to reducing health and environmental risks. there is also a significant void in communication channels to general public about appropriate disposal of used face-masks and gloves during covid-19 that may require user behavioural change, such as exploiting health belief model through social marketing approaches (suanda et al, 2013; suanda et al., 2017) . however, silva et al. (2020) noted that not all countries are capable of managing such waste appropriately and are been forced to use direct landfills or open burning as alternative strategies. there is also commensurate concerns about the short, and more longer term, impact of burning considerable amount of plastic that may increase environmental footprint due to release of ghgs and undesirable j o u r n a l p r e -p r o o f hazardous compounds . as some items of ppe are lightweight, there is potential for them to be blown by wind to pollute natural environments including threatening terrestrial and aquatic biota, such as by entanglement. silva et al. (2020) noted that up 40,000 kg of masks may find their way inappropriately into the natural environment arising from wwf (2020) reporting of inappropriate disposal of only 1% for over 10 million masks introduced to the environment monthly. in order to allay environmental problems arising from covid-19 due to high demand on sups and ppe that produces increased medical waste, silva et al. (2020) advocated (1) in the short term, it is important to maintain the ppe supply chain in order to the ensure health and safety of our citizens and our frontline hcws. however, we now need to look at contingency planning in order to future proof against the potentiale environmental impact of increased single-use plastic (sup) ppe waste using sustainable solutions. opportunities will arise to address this challenge through seamlessly connecting research and entrepreneurial ecosystems that will generate a new pipe-line of potentially usable bioplastic products. this could be accelerated through multi-actor innovation hubs linked to healthcare, industry and academia (rowan and galanakis, 2020) . silva et al. (2020) noted that the replacement of plastic value chain from fuel-based raw materials and energy has been priorities, which features in many international agreements addressing a green and circular economy. silva et al. (2020) also noted that bio-based plastics supports are emerging, but at an early stage capturing a market share of ca. 2% due mostly to low-cost of fossil-based j o u r n a l p r e -p r o o f plastics, the intense requirement for land use and related financial investment, and undeveloped recycling and/or disposal routes. hatti-kaul et al. (2020) described screening for microbial strains for enhanced hydrolytic and biodegradation abilities for direct conversion of biomass (such as microalgae), extraction of value-added products, and synthesis (polymerisation) process. however, such potentially high-performance bio-based polymers, similar to physical properties of fossil fuel-counterparts (such as low degradability, high durability) , would need to be characterized and tested for suitability to match design specifications of future ppe including tolerance to thermal processing and potential re-use. oems of ppe, academia and regulators should play as strong role in informing the efficacy of bio-based reusable polymers for next-generation products that considers suitability from design, safety and life cycle assessment perspectives. end-of-life strategies need to be consider for waste management and recycling of ppe during covid-19 used by general public without compromising on safety, where landfill and waste-to-energy should be a last resort option . the rapid accumulation of plastic waste is driving international demand for renewable plastics with superior qualities (e.g., full biodegradability to co 2 without harmful by-products), as part of an expanding circular bioeconomy (karan et al., 2019). there has been increasing interest in the identification of alternatives to petroleum-based plastics for various industrial applications where desirable bio-based material properties would include ease of biodegradation and renewability (emadian et al., 2016; thakuv et al., 2018) . bioplastics partly or wholly made from biological materials, and not crude oil, represent an effective way of keeping the huge advantages of conventional plastics but mitigating their disadvantages (carbon commentary, 2011) . a bioplastic is a plastic that is made partly or wholly from polymers derived from biological sources such as sugar cane, potato starch or the cellulose from trees, straw and cotton (thakuv et al., 2018) . there presents an opportunity to exploit the 9 stages of technology readiness developed by nasa (straub, 2015) to evaluate the sustainability and maturity of emerging innovations for covid-19 that also addresses environmental friendliness as well as functionality. this strategy is particularly relevant as it address potentially sustainable products from conceptualisation to commercial deployment at higher technology readiness levels: this is particularly relevant given that industry would be familiar with this concept and would allow ease of transitioning for environmental impact. this evaluation of new bioplastics could include life cycle (ruiz-salmón et al., 2020) and ecotoxicological (garvey et al., 2015) assessments of different trophic levels reflecting impact on biodiversity that connects academia with industry partners and policy makers. o'neill et al. (2020) described development of freshwater aquaculture on cutaway peatlands using organic principles where vast quantities of microalgae, used as natural means of water quality waste remediation, could be used as test system for advancing bioplastic-based ppe innovation and recycling for circular economy developments. future green innovative research could be extended to new biopolymer-based wrapping and packaging (including for adjacent food industry) to investigate non-thermal treatments that encompass both complex viruses and parasites . a limiting factor in the production of alternative biomaterials for alternative to single-use ppe relates to thermal stability of materials for fabrication and potential for deformation due to thermal processes. skrzypczak et al. (2020) recently reported on a new 3d printing approach for meeting such a need where they j o u r n a l p r e -p r o o f described an affordable, self-replicating, rapid prototyper that would also make this approach more accessible to home-based 3d printing activities. also demonstrated potential for exploiting different forms of polymer processing (such as 3d printing and injection moulding) after novel vapour hydrogen peroxide and electron beam treatments that could be advance next-generation ppe and medical device technologies. in response to meeting threats of covid-19, there is substantially increased volumes of medical waste produced that also contains ppe, which presents unprecedented challenges for meeting effective waste management strategies globally with significant potential for overload of systems want et al. 2020 . have noted that the unprecedented demand has also impacted other industries reliant upon ppe including manufacturing, construction, oil and gas energy, transportation, firefighting and food production. also noted that this pandemic has substantially impacted upon how solid-waste management activities are performed as prior to covid-19 resource recycling and waste management were not regarded as essential services and were placed in lockdown. however, the strategically important disease mitigation role of waste management has been recognised given the need to properly dispose and handle sars-cov2 contaminated waste to avoid transmission (reuters, 2020; price et al., 2020) . wastes and their disposal has urged countries to treat waste management amid covid-19 as urgent and essential public service. these authors noted that ppe includes plastics as major constitutes representing ca 25% by weight, which if not recycled or their disposal may contribute substantially to hazardous environmental pollutants, such as dioxins or toxic metals. polypropylene is a common constituent of ppes, such as found in n95 masks, tyvek protective suits, gloves, and medical face shields. singh and co-workers (2020) also noted that the potential for recovery of polymers from mixed healthcare waste including ppe is challenging. this would be further influenced by the low-level of recycling worldwide and lack of government policies. noted that single-use ppe is not a sustainable that are easier to maintain are preferred in china. incineration is widely deployed as is deemed to be safe, simple and effective (ghodrat et al., 2017) where extreme high temperatures completely kill microorganisms along with converting organic matter into inorganic dust. however, hospitals vary in type of incineration approach depending upon waste preparation and flue gas purification that includes pyrolysis vaporization incinerator where organic components of waste are converted to flammable gases to avoid dust at temperatures above 850°c that reduces particle emission to air. report that these high temperatures is conducive to complete destruction of toxic and hazardous components, thereby reducing production of toxic pollutants such as dioxins due to low temperature combustion (zhu et al., 2008 wang et al., (2020) described chemical disinfection technologies for treatment of hospital waste that is typically used in combination with mechanical and crushing treatments in china. generally, crushed hospital waste are mixed with chemical disinfections such as sodium hypochlorite, calcium hypocholorite, chlorine dioxide for fixed contact times during which organic wastes are decomposed and microbial threats inactivated. chemical disinfection have desirable attributes including low effective concentrations, rapid action, stable performance and broad sterilisation efficacy for different types of microorganisms. these chemical disinfectants are generally used as are non-corrosive, safe, easily soluble in water but not easily affected by chemical or physical factors with low toxicity and reported to have no residual hazard post disinfection (chen and yang, 2016) . suggest that chemical disinfection technology could be considered when amount of waste is small. also reported on use of microwave disinfection as a means of energy saving, low action temperature, slow heat loss, light damage and low environmental pollutions with no residues or toxic wastes after disinfection, but requires strict control by special microwave devices. stated that microwave technology only used at present for treatment of biohazardous wastes, but the technology is been promoted as effective supplementation technology for incineration to enable diversification of hospital wastes in china. wang also reported that microwave technology can achieve logarithmic value for killing complex pathogens such as parasites and viruses at > 6 log along with killing j o u r n a l p r e -p r o o f of bacillus subtilis endospores at > 4 spores. also reported on high temperature steam disinfection (saturated water vapor with temperatures greater than 100 c) to kill microorganisms (zhang et al., 2016) . in china, a log kill of thermophilic lipobacillus endospores at > 5 logs is required. however, this approach has a low volume reduction rate and easily generates toxic volatile organic compounds during disinfection (teng et al., 2015) . from perspective of investment and operation costs, as well as economic and social benefit, high temperature incineration is still most popular approach to hospital waste disinfection in china. thus, there are pressing needs to define effective decontamination strategies for medical waste through appropriate management strategies will also contribute to global collective effort in reducing sars-covid-19 transmission along with future safeguarding our environment. there is extraordinary pressure to meet shortages in single-use ppe supply for our frontline clinicians and healthcare workers. ppe treatment is challenging as the constituent material, including single-use plastics (sups), are sensitive to harsh decontamination processes. there has been an unprecedented surge in the production of commercial and homemade cloth and fabric face coverings to offset this challenge and to help with preventing person-to-person transmission in the community setting. many countries across the globe are extending, decontaminating and reusing ppe where there is critical shortage for frontline healthcare workers (hcws), but under emergency use only. this unprecedented need will continue given the absence of a vaccine and occurrence of successive waves of sars-cov-2 globally; and, the likely high demand for ppe by the medical and nursing profession beyond covid-19. fischer, e.p., fischer, m.c., grass, d., henrion, i., warren, s. w., westman, e. (2020) . low cost measurement of facemask efficiency for following expelled droplets during speed . zhao et al. [n95s] liao et al. sickbert-be nnett et al. perencev ich et al. rubio-ro mero et al (2020) dangaville et al. (2020) [shortage] saini et al. [overalls] barceló (2 020) virkram et al. derraik et al. fisher and shaffer (2011 ) ma et al. o'hearn et al. grinivas an and peh (2020) lowe et al. mullerji et al. (2020) ahmed et al. european commissi on (2020 schwart z et al (2020) inagalei et al (2020) [duv-leds] toon (2020) [ozone] macintyre et al. boṧkoski et al. (2020) matin-rodri guez et al (2020) [pain] [n95s] (2010) (2020) fda (2020c) laffey (2020) rubio-ro mero et al. mackenzi e (2020) [househol macintyre et al (2015) toon (2020) [gowns] clark (2020) jatta et al (2020) liao et al (2020) batejat et al ( fda (2020 park (2020) ou et al. laffey (2020) [surgical toon (2020) [ozone] ou et al. ou et al. barceló ( ozog et a. daeschler (2020) perkins et al. heilingloh et al., (2020) pastorino et al. genus, species and strain of microorganism *provide appropriate culture collection reference number and/or include type strain for test microorganism(s) in studies *include bacillus atrophaeus and/or geobacillus stearothermophilus endospore along with test organisms *confirmation of identify of test microorganisms by biochemical, physiological, morphological, immunological and/or molecular means (provide name of supplier for rapid test kits) *method of storing cultures (cryoprotectant) and frequency of sub-culturing (using fresh microbial slope every month kept at 4°c where bacterial indicators used) initial inoculum * description of procedures for microbial cultivation including name of supplier company for media (to include in vitro analysis) * growth medium composition, growth temperature, ph, incubation time, and growth phase (exponential or stationary) * growth achieved under static or orbital cultivation (rpm) * confirm purity by identifying 3 randomly selected isolates recovery conditions and enumeration methods for test strains * composition of media used for recovery to include basal media or physiological saline as diluent * time and storage conditions between treatment and microbiological analysis * description of procedure for enumerating viral test strains post treatments, such as use of in vitro tissue culture procedures uv treatment medium properties and conditions for commercial: description of power unit used for generating pulses to include equipment name of the supplier company and model for prototype: adequate description of components including treatment chamber, electrical configurations and specifications auxiliary devices * temperature probe * thermophile power detector and software for total broad-spectrum dose received by sample * transmissivity sensor to monitor %uv transmittance ensure microbial population density is ≤ 5-log orders to mitigate against influence of protective shading effects include description of media composition, ph, aw j o u r n a l p r e -p r o o f composition of menstruum used as diluent for treated samples sufficient number of treatment trials and replications to provide statistical confidence of findings at 95% level; description of statistic test and version of software package (such as minitab or spss) description of method used to generate bacterial endospores (natural aged for 7 days or incorporation of manganese sulphate to expedite conversion of vegetative cells to spores on agar surfaces) include native microflora along with artificially seeded test microorganisms due to variability in resistance profile to pl consider occurrence of cavities in plant surface microstructures that may protect microorganisms from incident light due to shading as part of eua, the fda (2020) reviews the totality of scientific evidence for ppe reprocessing including specialist testing *testing submitted within previous applications supporting device clearance for other uses that considers different types of polymer materials, such as materials consistent with those found in compatible n95 respirators. *performance data such as sporicidal test, residual analysis, bioburden reduction validation demonstrating > 3 log reduction of a non-enveloped virus challenge; testing regarding material compatibility, functionality and filtration performance of compatible n95 respirators after multiple decontamination cycles *testing regarding residuals after decontamination of compatible n95 respirators. *typically, reprocessed ppe are discarded after 10 treatments as per respective factsheet for facilities and personnel furnished to fda j o u r n a l p r e -p r o o f j o u r n a l p r e -p r o o f barriers to reuse of ppe by healthcare workers include lack of knowledge to inform acceptance and discomfort over prolonged usage with potential for social marketing studies to inform trust and associated decision making rimmer (2020); mitchell (2020) evaluation of fitted filtration efficiency (ffe) showed that surgical masks with ties (71.5±5.5%) and procedural mask with ear loops (38.1±11.4%) exhibit lower ffe post vh2o2 treatment is lower than n95 respirators (98.5±0.4%). this suggests potential benefits of using head ties instead of ear loops for homemade face coverings and would help prevent slippage below nose during wearing. sickbert-bennett et al., 2020 disinfection performance studies for evaluating ppe reuse over single or several cycles use surrogate viruses or bacterial endospore indicators (bioburden typically at or below 10 6 ), where most sars-cov-2 strain(s)are studied using in vitro tissue culture infection models. most researcher won't have access to level 3 containment facilities rowan and laffey, (2020) ; derraik et al., evaluation of facemask and variety of commonly available non-certified face coverings for filtering expelled droplets during speech, sneezing and coughing revealed that variability from below 0.1% (fitted n95 mask) to 110% (fleece mask). sequence of decreasing efficacy n95 respiratory, combining cotton-polypropylene-cotton mask; combining layer cotton in pleated style mask; combining 2 layer cotton with pleated style mask; use of single layer cotton masks; knitted masks; double layer bandana; and fleece. fischer et al., 2020 improvised face masks and face coverings should be used as a last solution and for low risk situation as increased duration of wearing may increase risks of virus infiltration due to humidity, liquid diffusion and virus retention european centre for disease prevention and control (2020) use of common washing machine (ca 60°c for 30 min) combined with use of spin dryer appear effective for face cloth decontamination and reuse zhao et al. 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strategies to reduce the global carbon footprint of plastics study on pyrolysis of typical medical waste materials by using tg-ftir analysis decontamination interventions for the reuse of surgical mask personal protective equipment: a systematic review ppe is designed for single-use for medical/nursing staff, but supply chain has been insufficient to meet global needs with many countries adopting reuse practices post deployment of technologies to meet emergency covid-19 use rowan and laffey (2020) ; derraik et al., (2020) there are limited technologies suitable for ppe reuse that reflects matched efficacy for reprocessing rubio-romero et al. (2020) differences in priority usage and decontamination technologies between higher risk medical environment (ppe) and lower risk community settings (face coverings) that have informed selection of technologies and approaches used derraik et al. (2020) evidence that ppe can be effectively reprocessed using technologies not readily available to public such as vh2o2, o3, low pressure uvc such as uvgi (2000 mj/cm 2 ) where variance in determining efficacy of uv dose between uv modalities influencing harmonious acceptance). generally, is greater disinfection using uva over uvb and uva.derraik et al., (2020) ; rowan, 2019; rubio-romero et al. (2020) high throughput vh2o2 can effectively disinfect, for example ,2,500 n95 respirators per 12 h shift at 3000-750 ppm hydrogen peroxide rubio-romero et al., (2020) mackenzie, (2020); perkins (2020) recommendation for wearing of face masks and coverings to prevent spread of covid-19 cdc (2020); ministry of health spain (2020); choice of technologies for reprocessing of ppe healthcare depends on the type and complexity of ppe (functionality, fit test, deformation, filtration efficacy) that are typically single use and thermally-sensitive with increasing challenges in the order face shields, gowns, ffrs (including disposable n95 respirators,) derraik et al., (2020) ; rubio-romero et al. (2020) evidence of extended use of n95 respirators such as 4 h (france, new zealand and sweden) to 40 h (mexico) kobayashi et al. (2020) physical irradiation technologies (gamma) and ethylene oxide (eo) are not appropriate for ppe reuse due to non-compatability with material composition or concerns over lingering residual toxic end-points produced during eo rowan and laffey (2020) j o u r n a l p r e -p r o o f wearing such as over winter flu season face shields are inferior to use of face masks where the latter is particularly relevant for combined use in healthcare settings to prevent infection through the eyes. rowan and laffey, (2020) an increasing trend towards development of smart coatings on materials for inactivation of sars-cov-2 and against other future potential pandemic viruses, along with provision for incorporation in ppe, mobile phones and so forth behzadinasab et al. 2020 .over 50 countries are now recommending facemasks by public that presents a new form single-use plastic waste silva et al., 2020 influence of soiling on critical ppeup to 14 days survival and retention of sars-cov-2 on surgical gowns. kasloff et al., 2020. there are opportunities for innovation in new bioplastic-based ppe and waste management as there is likely to be a high demand for ppe post covid-19 ilyas et al., 2020 there is an increase trend towards modelling recovery scenarios to investigate the potential impact of lockdown duration that is implemented to protect frontline hcws against covid-19 that may include provision for ppe costings against the cost associated with medical staff absenteeism or illness due to inadequate ppe. guan et al. (2020) ; thomas et al. (2020) ; ivanov et al. (2020) ; mukerji et al. 2017) use of artificial intelligence and deep learning could help identify high-risk patients and suggest appropriate types and use of ppe boṧkoski et al., (2020) j o u r n a l p r e -p r o o f the authors declare that they have no competing or conflict of interests.j o u r n a l p r e -p r o o f key: cord-279942-y5io9qzl authors: chakrabarty, rajan k.; beeler, payton; liu, pai; goswami, spondita; harvey, richard d.; pervez, shamsh; van donkelaar, aaron; martin, randall v. title: ambient pm2.5 exposure and rapid spread of covid-19 in the united states date: 2020-11-09 journal: sci total environ doi: 10.1016/j.scitotenv.2020.143391 sha: doc_id: 279942 cord_uid: y5io9qzl it has been posited that populations being exposed to long-term air pollution are more susceptible to covid-19. evidence is emerging that long-term exposure to ambient pm2.5 (particulate matter with aerodynamic diameter 2.5 μm or less) associates with higher covid-19 mortality rates, but whether it also associates with the speed at which the disease is capable of spreading in a population is unknown. here, we establish the association between long-term exposure to ambient pm2.5 in the united states (us) and covid-19 basic reproduction ratio r 0– a dimensionless epidemic measure of the rapidity of disease spread through a population. we inferred state-level r 0 values using a state-of-the-art susceptible, exposed, infected, and recovered (seir) model initialized with covid-19 epidemiological data corresponding to the period march 2–april 30. this period was characterized by a rapid surge in covid-19 cases across the us states, implementation of strict social distancing measures, and a significant drop in outdoor air pollution. we find that an increase of 1 μg/m3 in pm2.5 levels below current national ambient air quality standards associates with an increase of 0.25 in r 0 (95% ci: 0.048–0.447). a 10% increase in secondary inorganic composition, sulfate-nitrate-ammonium, in pm2.5 associates with ≈10% increase in r 0 by 0.22 (95% ci: 0.083–0.352), and presence of black carbon (soot) in the ambient moderates this relationship. we considered several potential confounding factors in our analysis including gaseous air pollutants, and socio-economical and meteorological conditions. our results underscore two policy implications – first, regulatory standards need to be better guided by exploring the concentration-response relationships near the lower end of the pm2.5 air quality distribution; and second, pollution regulations need to be continually enforced for combustion emissions that largely determine secondary inorganic aerosol formation. in december 2019, a new strain of coronavirus, sars-cov-2, began infecting residents of wuhan province, china. (chinazzi et al. 2020; li et al. 2020b; wu et al. 2020a; xu et al. 2020) in the following months, the disease caused by sars-cov-2coronavirus disease 2019 (covid-19)has spread to nearly every country around the globe, and the situation had rapidly evolved into a global pandemic. (chinazzi et al. 2020; gilbert et al. 2020) the viral entry of sars-cov-2 has been shown to use angiotensin-converting enzyme 2 (ace2) as its co-host receptor. (wan et al. 2020 ) ace2 plays a crucial role in lung protection by cleaving and converting angiotensin ii (ang ii) to the cardioprotective angiotensin 1-7 (ang 1-7). (tikellis and thomas 2012) clinical observations of covid-19 patients (guan et al. 2020 ) suggest a mechanism involving viral loads of sars-cov-2 depleting residual ace2 activity and impairing host defenses. this causes an imbalance between ang ii and ang 1-7, resulting in high circulating levels of ang ii, which induces pulmonary vasoconstriction, inflammation, and oxidative stress. (derouiche 2020) consequently, depleted lungs, typically in the form of acute lung injury or its most serious form, acute respiratory distress syndrome, manifest in patients with covid-19. (li et al. 2020a) a recent study by italian medical researchers posited a causal link between sars-cov-2 infection rate and long-term air pollution exposure in a population.(frontera et al. 2020) they postulated a -double-hit phenomenon‖: patients chronically exposed to high levels of fine particulate matter (pm 2.5 ; particulate matter with aerodynamic diameter 2.5 micrometers or less) present themselves with an overexpression of ace2, (lin et al. 2018 ) which readily facilitates penetration of the viral infection. this in turn depletes ace2 receptors and gives rise to more severe forms of the disease. subsequently, the spread of the disease accelerates among the population. j o u r n a l p r e -p r o o f journal pre-proof exposure to pm 2.5 has a well-established association with increased risks and severe outcomes during infectious disease outbreaks, including covid-19, the 2009 h1n1, and the 1918 spanish influenza pandemics (clay et al. 2018 (clay et al. , 2019 morales et al. 2017; wu et al. 2020b ) exposure to pm 2.5 has been causally linked to occurrences of chronic respiratory disease, infectious respiratory disease, asthma, inflammation, and decreased lung function. ) recent studies have have strongly associated covid-19 mortality with long-term air pollution exposure in the us , as well as identifying that long-term meteorological and climatic variables play a minor role in comparison to the amount of susceptible population for fundamentally driving the pandemic dynamics (baker et al. 2020 ). yet, no study to our knowledge has examined the association between long-term pm 2.5 exposure and the exponentially fast spread of covid-19 in a population. (ferguson et al. 2020) the spread of a disease through a population is estimated using the dimensionless epidemiological parameter the basic reproduction ratio. (griffin et al. 2011; liu et al. 2020b; ridenhour et al. 2018) it is defined as the average number of individuals that an infected individual would infect in an entirely susceptible population. thus, this parameter is of utmost importance for public health officials and policymakers because it indicates the onset of an outbreak based on the threshold value of 1.0. with increasing >1, disease spread in a population becomes more rapid, and it becomes harder to control the outbreak. here, we establish the association between and long-term ambient pm 2.5 exposure in the united states of america (us), where the impact of the pandemic has been most severe. using robust and established statistical analysis, we elucidate the role of pm 2.5 mass concentration and composition in covid-19's rapid spread across the us. we estimate the state-specific values of using an established epidemic progression model involving the susceptible-exposed-j o u r n a l p r e -p r o o f inference of the covid-19 basic reproduction ratio. we inferred state-wise values by fitting the prediction of a susceptible-exposed-infected-recovered (seir) model (li et al. 2020c; liu et al. 2020a ) to confirmed covid-19 cases. (dong et al. 2020) our epidemic model accounts for the age-stratified disease transmissibility (wallinga et al. 2006) , and possible large-scale j o u r n a l p r e -p r o o f journal pre-proof undocumented transmission (li et al. 2020c ) of covid-19 in the us. the detailed model structure and parameterization follow that outlined in recent publications (li et al. 2020c; liu et al. 2020a) , except that here we neglected the influence of interstate mobility of covid-19 carriers on long-term disease progression, considering the rapid decline in domestic traffic after the nationwide implementation of stay-at-home orders. the inference timespan was set between march 02 and april 30 (coinciding the nationwide social distancing period), so as to minimize the influences of other human behaviors and social activities on epidemic dynamics. the daily number of confirmed covid-19 cases was acquired from a real-time epidemic tracking dashboard published by johns hopkins university. (dong et al. 2020) the fitting procedure can be described as such: first, the daily number of state-wise confirmedand-active covid-19 cases 31 was tracked and recorded, which can be written as a time-series ( ) (subscript denotes each us state, superscript indicates -reported‖, and is time incrementing with a unit of day between march 02 and april 30). next, the seir prediction was fitted with the ground truth using twenty consecutive days of epidemic size data. specifically, we took twenty consecutive elements from the ( ) time series, generating a -minibatch‖ written as ( ). here, is defined as an initial date. a total of 41 minibatches can be generated, where increments between 1 and 41. for each minibatch ( ), we initialize the seir model with ( ), and then the model guessed a value for and predicted the epidemic trends on the following nineteen days, written as ̂( ). the values of were inferred in a trialand-error manner, by minimizing the root-mean-square-error between ( ) and (1) here, represents the basic reproduction ratio values inferred for state within the timespan between and ; and respectively denote the unknown documentation ratio and exposure ratio 34 , which were simultaneously inferred along with . finally, for each state , we calculated a time-averaged reproduction ratio ̅ by taking the arithmetic mean values of the series. where denotes a constant intercept; ( ) denotes a thin-plate basis smooth function; denotes a zero centered gaussian noise; stands for degrees of freedom, and was chosen because no high-level of nonlinearity was observed in the data trends. the restricted maximum likelihood method was adopted in the optimization to prevent overfitting. the gam fitting and analysis were conducted using r software and the -mgcv-1.8-31‖ package. the complete inference results for ̅ (time-averaged between march 2 and april 30) and the pm 2.5 composition profiles corresponding to each us state are tabulated in supplementary information (table s1 -s9). although real-time values of ̅ were always greater than 1 during the two-month investigation period, the parameter's rapidly declining trend (supplementary table s1 ) suggests that the implemented non-pharmaceutical intervention strategies-such as school and business closure-were effective in altering the disease dynamics. figure 1 shows the correlation between state-wise ̅ and the annual average pm 2.5 concentration. a positive correlation between ̅ and pm 2.5 concentration can be observed from all the past 6-year datasets. the correlation between ̅ and long-term average (between years 2000 and 2017) pm 2.5 exposure profile for the entire continental us are shown in figure 1 (b) and (c). a qualitative comparison of the color-coded continental us maps reveals the overall spatial pattern of ̅ coinciding with that of the pm 2.5 exposure levels. j o u r n a l p r e -p r o o f figure 3 shows the results of johnson-neyman analysis (carden et al. 2017) , where sna fraction is the predictor variable and bc concentration is the moderating variable. these results indicate that the direct relationship between sna fraction and ̅ is dependent on bc concentration. figure 3(a) shows the value of ̅ as a function of sna fraction and bc concentration. figure 3 shows that in areas where a large portion of pm 2.5 is made up of sna, an increase in bc concentration leads to an increase in ̅ . however, if sna makes up a smaller portion of pm 2.5 , an increase in bc concentration leads to a decrease in ̅ . alternatively, as bc concentration increases, the positive relationship between ̅ and sna fraction becomes more prominent. shows the 95% confidence interval. given that we find both population density and sna fraction to be highly correlated with ̅ , a logical argument might arise regarding the relation of ̅ with sna simply being a compositional surrogate for population density. especially since sna aerosol precursors are closely linked to urbanization, one might argue that it is difficult to delineate the effect of sna fraction and population density on ̅ . we aim to address this concern and strengthen our argument by citing specific examples wherein confounding relationship of ̅ with population density and sna with population density do not hold valid. a justified comparison would be between alabama and louisiana, two states that are similar climatically, socioeconomically, and demographically (see table s11 ). in comparing these states, we find that their population densities differ by only 1.04%, but louisiana has 5% higher fraction of sna. despite their similarity in population density, ̅ in louisiana is 20.7% higher than alabama. this example shows that when comparing two states that differ only in sna fraction, the positive association between sna fraction and ̅ still holds. to the best of our knowledge, this is the first nationwide study to estimate the relationship between long-term exposure to pm 2.5 and the rapidity of covid-19 spread in the us. up to 6 µg/m 3 pm 2.5 ambient concentrations, which is below current regulatory standards(epa 2019), we find that a 1.0 μg/m 3 increment in long-term exposure associates with a 0.25 increase in ̅ . short-term exposure due to outdoor air pollution dropped significantly during the months of providing new evidence of a relationship of pm 2.5 with ̅ at levels below the current naaqs (dirgawati et al. 2019; makar et al. 2017; pinault et al. 2016) . with respect to pm 2.5 composition, we find a 10% increase in sulfate-nitrate-ammonium (sna) ionic fractions to be associated with a 0.218 (≈10%) increase in ̅ (95% ci: 0.083 -0.352). this strong association of ̅ with secondary inorganic fraction in pm 2.5 , which could be is relatively straight forward, partitioning of nitrate to sol phase depends on a number of factors including temperature (kroll et al. 2020) . no 2 has also been shown to accelerate the oxidation of so 2 to form sulfates the inherent ability to accurately quantify the number of covid-19 cases due to limited testing capacity during the march-april timeframe presents another potential limitation. the large uncertainty represented by the shaded area in fig. 3 suggests that the variation in ̅ is not fully accounted for by the pm 2.5 exposure profile. caution must be taken when extrapolating results from this study to generalize the virus spread in other countries and drive public health responses. the basic reproduction ratio is a complex property of an epidemic and is highly sensitive to the underlying model used to estimate it, the specific population demographic, and time period of study. (ridenhour et al. 2018) future analysis should include covid-19 epidemic parameters and pm 2.5 exposure data at finergrain levels, e.g. county-level . research on disproportionate impacts of air pollutionon on at-risk populations, including minority populations and populations with lower socioeconomic status, during the epidemic is another understudied area. synergistic analysis of air quality and population demographic information suggest that the highest pm 2.5 concentrations in a given area tended to be measured at locations where populations lived or were more likely to below the poverty line and constituted larger percentages of racial and ethnic minorities. last but not least, the design limitations of this study calls for detailed research on biological mechanisms responsible for the observed associations. j o u r n a l p r e -p r o o f the epidemic dynamic model and statistical analysis codes can be accessed at https://github.com/pliu1991/covid19pm25_supporting_data_and_files. 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authors thank the insightful comments and suggestions from two anonymous reviewers. ☒ the authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.☐the authors declare the following financial interests/personal relationships which may be considered as potential competing interests:j o u r n a l p r e -p r o o f key: cord-349078-59wel5o5 authors: kanniah, kasturi devi; zaman, nurul amalin fatihah kamarul; kaskaoutis, dimitris g.; latif, mohd talib title: covid-19's impact on the atmospheric environment in the southeast asia region date: 2020-05-25 journal: sci total environ doi: 10.1016/j.scitotenv.2020.139658 sha: doc_id: 349078 cord_uid: 59wel5o5 abstract since its first appearance in wuhan, china at the end of 2019, the new coronavirus (covid-19) has evolved a global pandemic within three months, with more than 4.3 million confirmed cases worldwide until mid-may 2020. as many countries around the world, malaysia and other southeast asian (sea) countries have also enforced lockdown at different degrees to contain the spread of the disease, which has brought some positive effects on natural environment. therefore, evaluating the reduction in anthropogenic emissions due to covid-19 and the related governmental measures to restrict its expansion is crucial to assess its impacts on air pollution and economic growth. in this study, we used aerosol optical depth (aod) observations from himawari-8 satellite, along with tropospheric no2 column density from aura-omi over sea, and ground-based pollution measurements at several stations across malaysia, in order to quantify the changes in aerosol and air pollutants associated with the general shutdown of anthropogenic and industrial activities due to covid-19. the lockdown has led to a notable decrease in aod over sea and in the pollution outflow over the oceanic regions, while a significant decrease (27% 30%) in tropospheric no2 was observed over areas not affected by seasonal biomass burning. especially in malaysia, pm10, pm2.5, no2, so2, and co concentrations have been decreased by 26–31%, 23–32%, 63–64%, 9–20%, and 25–31%, respectively, in the urban areas during the lockdown phase, compared to the same periods in 2018 and 2019. notable reductions are also seen at industrial, suburban and rural sites across the country. quantifying the reductions in major and health harmful air pollutants is crucial for health-related research and for air-quality and climate-change studies. j o u r n a l p r e -p r o o f 3 accounting for 94% of the cases and 97% of the total deaths respectively (who, 2020) . as one of the most densely populated areas in the world, for constraining the fast spread of the disease, the sea countries implemented a series of measures such as placing travel bans, closing international and inter-state boarders, quarantine residential areas, restriction in large-scale social movement and social gatherings (including religious activities) and implementing partial/full lockdown, which included suspension of operation of public transportations, industries, shopping centres, worship places, schools and other educational institutions. in malaysia, covid-19 pandemic was first reported in january 2020 (sipalan et al., 2020) . however, the localized clusters began to emerge in march due to a massive religious gathering held near kuala lumpur in late february. since the mid of march, active covid-19 cases increased significantly and till 16 may 2020, the country has reported 6,855 confirmed cases and 112 deaths (who, 2020) . consequently, the malaysian government implemented the movement control order (mco) for two weeks starting from 18 march, which was then extended to until 9 june. with the movement control order, the malaysian government shuts down public transport, educational institutes, busy central parks and other social interaction points in a way to curtail the spread and transmission of covid-19. as a result of the lockdown and the disruption in human and industrial activities in numerous countries around the world, a significant reduction in air pollution, especially in the concentration of no 2 , has been noticed in china and several european and american countries (shrestha et al., 2020; tobias et al., 2020; wang and su, 2020; zhang et al., 2020) . recent studies by muhammad et al. (2020) , wang and su (2020) and dutheil et al. (2020) have reported a no 2 reduction ranging between 20-30% in china, usa, italy, spain and france. data collected by the ozone monitoring j o u r n a l p r e -p r o o f 5 chemical reactions in the atmosphere (pandolfi et al., 2012; henschel et al., 2015; kharol et al., 2018; epa, 2020) . therefore, the use of aod, although being a columnar quantity, may also detect changes in the concentrations of pollutant particles in the lower troposphere. assessing the total amount of columnar aerosol is critical not only for studying its impact on human health but also on solar radiation, cloud condensation processes, and climate change over south and southeast asia (e.g. dumka et al., 2015; pani et al., 2016 pani et al., , 2018 singh et al., 2020) . since the high pollution levels is a major environmental and health issue in sea countries, it is essential to understand the degree and the spatial extent of the decrease in air pollutants and aerosols due to restriction measures during the covid-19 period in spring 2020. such findings can assist in formulating more stringent policies in the post covid-19 period, in order to maintain an acceptable air quality in this region. this study aims to investigate the effect of mco/lockdown measures on air quality in the sea region using satellite remote sensing and ground-based measurements with special focus on malaysia. himawari 8 is a japanese weather satellite operated by the japan meteorological agency. it was launched on 7 october 2014 and it carries the advanced himawari imager (ahi) sensor, which operates at 16 bands from visible to infrared (bessho et al., 2016) . the level 3 (l3) product of himawari-8 is an improved version of the l2 aod product that minimized cloud contamination (kikuchi et al., 2018) . this l3 product is reported every 1 hour and it has a spatial resolution of 5 km. aerosol products (l2 v1.0, v2.1) from himawari-8 have been compared and evaluated against aeronet and modis c6.1 aerosol products over asia and the oceanic regions with satisfactory agreement . furthermore, himawari-8 observations have been widely used for aerosol studies and for estimations of solar radiation over east asia yan et al., 2018; hou et al., 2020) . in this study, the himawari-8 merged l3 aod product, covering the period 15 july 2015 to 31 december 2019, was downloaded from the japan aerospace exploration j o u r n a l p r e -p r o o f 6 agency (jaxa) website (http://www.eorc.jaxa.jp/ptree/index.html). himawari-8 aods were first evaluated against aeronet aods in order to assess their robustness to be used for studying the aerosol patterns and spatial-temporal variability over the sea region. aeronet (aerosol robotic network) is a global network for ground-based aerosol monitoring using cimel sun photometer that provides aod data at 7 wavelengths with a temporal resolution of 15 minutes under cloudless skies (holben et al., 1998) . in this study, level 2 (cloud screened and quality assured) data were used from 2 stations in malaysia i.e. university science malaysia, penang (5.36, 100.30) and kuching (1.49, 110.35), 1 station (songkhla) in southern thailand (7.18, 100.60) and 1 station in singapore (1.30, 103.78), in order to validate the himawari-8 aods during the period 15 july to 31 december 2019 for the singapore station and from 15 july 2015 to 31 december 2018 for the rest. the himawari-8 l3 aod at 500 nm was directly compared with the aeronet aods. in order to collocate the himawari-8 aod, the aeronet data were averaged for ±30 minutes of the himawari-8 overpass time (zhang et al., 2019) . a single satellite pixel (fine scale aod) that lies over or closest to the aeronet stations was used for the validation, a method similar to that adopted by yang et al. (2020) and emili et al. (2011) . statistical measures such as the root mean square error (rmse), relative bias (rb) and mean absolute error (mae) were used to quantify the accuracy of the himawari-8 l3 aod against aeronet. the tropospheric no 2 column density is systematically measured by the dutch-finnish omi sensor on board aura satellite, which follows a sun-synchronous orbit with an equator crossing time near 13:45 local time (nasa, 2020) . omi measures the backscattered radiation from the sun using spectral bands ranging from the ultraviolet (uv) to infrared wavelengths (levelt et al., 2018) . in this study, no 2 concentrations were obtained from the nasa website (https://so2.gsfc.nasa.gov/no2/no2_index.html). the no 2 maps over sea were produced using high resolution daily gridded at 0.1 x 0.1 spatial resolution, which is then averaged over a 15-day j o u r n a l p r e -p r o o f 7 window. therefore, we produced maps that represent 1 march, 31 march, and 17 april (the latest available data at the time of writing the original manuscript). we also used no 2 data averaged over 2015 -2019 (baseline) , in order to detect the absolute differences between 2020 and the baseline data. we did not use the no 2 data from tropomi because data prior to 2020 is limited. furthermore, ground-based measurements of pm 10 and pm 2.5 concentrations, along with other pollution gases, such as so 2 , no 2 , co and ozone (o 3 ), were obtained from several monitoring stations across malaysia operated by the department of environment (doe) (kanniah et al., 2016; kamarul zaman et al., 2017) . a total of 65 continuous air quality monitoring (caqm) stations that are strategically located at residential, industrial, busy-traffic and rural areas provide systematic measurements of air pollution. the instruments and procedures used to regularly monitor the nearsurface atmospheric aerosols and pollutants in malaysia are described in kanniah el al. (2016) . initially, the himawari-8 aods were validated against aeronet aods from three stations in the sea region. the validation results show a good consistency between himawari-8 l3 and aeronet aods with r 2 =0.81, rmse =0.13, mae = 0.09, a bias of 1.38% and an overall overestimation of 1% (suppl. fig. 1 ). the excellent agreement between himawari-8 aod and aeronet data allows for using the satellite aod to investigate the aerosol levels and variability in the sea region before and during the covid-19 period. composite aods are examined and compared between three periods, covering 18 march to 30 april of the years 2018, 2019 and 2020, in order to reveal possible changes over the sea region during the covid-19 period in spring 2020 ( fig. 1 ). it should be noted that for a detailed analysis and quantification of the impact of covid-19 on the columnar aod over sea, climatological and meteorological factors should be taken into consideration as well as the effect of the extensive biomass burning in this season that are independent from the restriction measures and the general j o u r n a l p r e -p r o o f 8 lockdown. a qualitative overview shows that the sea pollution outflow (wang et al., 2015) over the oceanic regions has been reduced during 2020, compared to the previous years, as also observed over the southern china sea due to restriction measures and the general lockdown in china wang and su, 2020) . lower aods are also seen over the northern bay of bengal, which is highly affected by the ganges valley pollution outflow (kharol et al., 2011; srinivas and sarin, 2014) . however, higher aods over the northern parts of the peninsular sea (northern thailand and laos) are seen in 2020, despite the restriction measures in anthropogenic activities and malfunction in industries. these high aods, which are characteristic for the pre-monsoon season, are attributed to forest and vegetation fires (biswas et al., 2015; pani et al., 2018; vandrevu et al., 2019) , being responsible for the haze conditions usually covering the whole indochina (gautam et al., 2013; kanniah et al., 2016) . besides the large spatio-temporal variability in aod over sea, a close inspection into the major cities in the region ( among the sea countries, malaysia enforced the movement control order (mco) for a longer period, starting from 18 march until 6 june 2020. in addition, for a more detailed analysis over malaysia, which is only marginally affected by the forest and vegetation fires in the northern part of sea, the aod values were extracted for a single pixel emili et al., 2011 ) that is located over or closest to the 65 monitoring stations including industrial (7), urban (10) cultivation, biogenic emissions, dust, peat and vegetation fires, which explain the comparable or even higher aods than the urban sites, a large part of the significant aod decrease at all sites is attributed to the general shutdown of the anthropogenic activities in order to restrict the expansion of covid-19. in a previous study, it was shown that the pm 10 concentrations alone can explain about 60% of the variation in aod over malaysia (kamarul zaman et al., 2017) and, therefore, notable reductions in the near-surface aerosols are also detected in the columnar. nitrogen oxides (no x ) are primarily emitted as no from combustion sources i.e., vehicle exhausts, industries, power plants, residential heating (e.g. dumka et al., 2019) and is converted to no 2 after fast oxidation processes, which is recognized as a tracer of anthropogenic combustion activities and j o u r n a l p r e -p r o o f precursor of nitrate aerosol and ozone . as a major pollutant, no 2 can cause respiratory diseases, asthma and cellular inflammation and is considered highly lethal to human health (faustini et al., 2014; he et al., 2020) and harmful for the total environment through the formation of nitric acid (hno 3 ) and acid rain (kouvarakis et al., 2001; zhang et al., 2020) . observations from aura-omi satellite sensor generally show a decrease in the concentrations of columnar no 2 over the most parts of the sea region in march and april 2020 compared to the mean 2015-2019 (fig. 4) . the largest reductions are detected over and around major urban centres like manila, bangkok, kuala lumpur, singapore, while over low-dense populated and forested areas in sumatra and borneo, changes in no 2 are rather marginal. on contrary, the large increase in no 2 concentrations over the northern part of sea in march 2020 is characteristic for the high intensity of the forest and agricultural fires. a more detailed visualization for the aura-omi tropospheric no 2 concentrations over major cities in sea is shown in suppl. fig. 2 . in general similarity to the aod patterns observed over manila, kuala lumpur and singapore (fig. 2) , the no 2 concentrations recorded a large reduction during spring 2020 compared to the previous years. this decrease approached -34%, -27% and -30% over manila, kuala lumpur and singapore, respectively, on 17 april (15-day averages) compared to no 2 baseline data (averaged over 2015-2019) (table 1) , which is ascribed to shutting down of businesses and factories and restriction in traffic due to partial/general lockdown (muhammad et al., 2020; tosepu et al., 2020; zhang et al., 2020) . note that in the strait of singapore, the reduction in no 2 was much lower due to continuous emissions from shipping for the international trade (suppl. fig. 2 ). other cities that also documented reduction in no 2 levels during the same time period are bangkok (-22%), jakarta (-34%) and phnom penh (-6%) ( (pani et al., 2018; bukowiecki et al., 2019; nguyen et al., 2019) . this is also supported by the large inter-annual and intra-seasonal variability in no 2 levels around vientiane, laos due to severe biomass burning on certain periods, like 15-31 march 2020 (suppl. fig. 2) , which prevents the extraction of robust results regarding the impact of lockdown on atmospheric pollution. tropospheric no 2 levels are highly associated with biomass-burning activity over the sea region (itahashi et al., 2018; ul-haq et al., 2016 and can be influenced by several other factors, including meteorology (such as insolation, precipitation, advection) and other pollution emissions. however, at local level, above and around the urban areas, no 2 levels seem to be significantly lower in 2020 (suppl. fig. 2 ; table 1 ). this section investigates the changes in pm 10 and pm 2.5 concentrations and in air pollutant (no 2 , so 2 , co, o 3 ) levels at 65 air-pollution monitoring stations located all over malaysia and include industrial (7), urban (10), suburban (36) and rural (12) in general, the comparison shows a notable decrease in pm 10 , pm 2.5 and no 2 concentrations at the industrial and urban sites during the mco period. the pm 10 levels are much lower than the limit of 50 μg m -3 and in 2020 they are close to the 20 μg m -3 recommended by the who, indicating good air quality conditions across the country, with pm 2.5 levels below 25 μg m -3 . more specifically, the pm 10 concentrations reduced by 28-39% (statistically significant at 95% confidence level) at the industrial sites and by 26-31% in the urban areas (statistically significant at 95% confidence level) in 2020 compared to 2019 and 2018, respectively (fig. 5a) . the respective reductions for pm 2.5 were found to be 19-42% at industrial and 23-32% at the urban sites (fig. 5b) . even larger decreases occurred in no 2 levels, which have been reduced by 33-46% in the industrial areas and by 63-64% in the urban centres relative to 2018 and 2019 (fig. 5c) . the respective decreases at the suburban and rural sites, not j o u r n a l p r e -p r o o f directly or less affected by anthropogenic emissions, were found to be slightly lower, since pm 10 revealed a decrease of 22-27% at suburban and 10-24% at rural sites, pm 2.5 a decrease of 15-28% (suburban) and 4-27% (rural areas), while reductions in the range of 55-56% was found for no 2 in the suburban areas and much lower (26-34%) at the rural background sites. during daytime, no 2 reacts with oh radicals for the formation of hno 3 , while at night-time, reactions with no 3 radicals are an important source of hno 3 , which is the precursor for nitrate aerosol (no 3 -) formation (sheinfeld and pandis, 2016) . therefore, the large reduction in no 2 levels during the covid-19 period may limit the built-up of hno 3 and no 3 aerosols (bardouki et al., 2003; cuccia et al., 2013; titos et al., 2014) . in addition, the limitation in combustion activities resulted in a decrease in co levels, a direct pollutant from incomplete combustion sources (vehicular traffic and biomass burning). the reduction in co is higher (25-32%) at the urban and suburban (25-27%) sites, whereas the rural background sites do not display any significant variability between the three years (6-7%), implying rather different sources of co, most likely agricultural burning or even a rather stable background days in the free troposphere, so it presents mostly regional characteristics (ealo et al., 2018) . as a major emission pollutant from stationary sources (industries and power plants), so 2 displays reduction at the urban (9-20%) and suburban (17-19 %) sites in 2020 compared to 2019 and 2018, but not at industrial ones, since major power plants and industries were continuously operating for reasons of common good and welfare (fig. 5e ). at the rural areas, so 2 concentrations are more variable between the years and may be highly influenced by local/regional meteorology and downwind impact from nearby urban areas or industrial units (collivignarelli et al., 2020) . in contrast, o 3 did not record significant changes in the examined periods between the years, since it's a secondary pollutant formatted by no titration in the presence of uv light or via volatile organic j o u r n a l p r e -p r o o f 13 compounds (vocs) (reche et al., 2018) and its levels are kept mostly unchanged in malaysia over a certain period of the year. however, a small increase (3-7%) was observed at the urban sites during 2020 (fig. 5f ) due to reduction in no levels, similarly to other urban environments (dantas et al., 2020; kerimray et al., 2020; li et al., 2020; nakada and urban 2020; tobias et al., 2020) . for after/before the mco to be 0.9 at the industrial sites and 0.85 at the urban ones. as pm 10 and pm 2.5 may have various sources, apart from the anthropogenic ones, the mco had a larger effect on the no 2 levels. therefore, in 2020, no 2 has been reduced by 34% (54%) after the mco compared to the period before at industrial (urban) sites, whilst the no 2 ratios in 2019 were found to be 1.04 and 1.06, and those in 2018 were 1.17 and 1.00 for the industrial and urban sites, respectively. this analysis further highlights the significant decrease in no 2 emissions at the industrial and urban areas in malaysia, as a result of the restriction measures for preventing the dispersion of covid-19. during the last 1-2 months, several studies have been published dealing with the impact of the lockdown on air quality at several cities in developed and developing countries around the world. nearly all these studies revealed large declining trends in pm concentrations and in a series of air j o u r n a l p r e -p r o o f pollutants, with these trends being strongly related to the specific characteristics of each site, the relative influence from traffic and industrial sources, the impact of natural emissions (forest fires, desert dust) and the proximity to major power plants that are under continuous operation. this section discusses results from recent studies dealing with the decreasing trends in aerosols and air pollutants due to covid-19 lockdown at several places around the world. according to the ministry of ecology and environment of china, (report, 2020), the concentrations of six major air pollutants during the covid-19 period (january -march 2020), have been drastically reduced compared to previous year(s), recording a mean reduction of -20% for pm 10 , -15% for pm 2.5 , -25% for no 2 , -6% for co, and -21% for so 2 , while o 3 remained rather steady from year-to-year (wang and su, 2020) . especially in wuhan, where the general lockdown first established on 23 january 2020, the no 2 levels have reduced by about 50% compared to the previous year (wang and su, 2020) . another study , reported an average reduction of 52% in no x emissions in east china during the period after the lockdown compared to the levels before. average decreases of 24.7%, 13.7%, 6.8%, 5.9%, and 4.6%, for no 2 , pm 10 , so 2 , pm 2.5 and co, respectively were reported in 44 cities in northern china (bao and zhang, 2020) , while significant reductions in air pollutants due to lockdown were also observed at the yangtze river delta, also captured by the wrf-camx model . however, nowadays, the no x levels have been gradually regained in some chinese provinces after the termination of the quarantine period and return-to-work day . continuous monitoring of the pollution levels and future studies will reveal the degree of the pollution re-appearance over major urban areas in malaysia as well, after the re-opening on the economy. in india, pm 10 , pm 2.5 , no 2 and co concentrations analyzed during 16 march -14 april from 2017 to 2020 in 22 cities over the country revealed reductions by 43%, 31%, 18% and 10%, respectively during the lockdown period compared to previous years. on contrary, so 2 exhibited marginal changes, whereas an increase of 17% was seen for o 3 . other studies in delhi, revealed maximum reductions for pm 10 and pm 2.5 concentrations (50%) compared to the pre-j o u r n a l p r e -p r o o f 15 lockdown period (mahato et al., 2020) , while compared to 2019, pm 10 and pm 2.5 decreased by about 60% and 35-39%, respectively (chauhan and singh, 2020; mahato et al., 2020) . in addition, no 2 decreased by 52.7% and co by 30.4% during the lockdown period (mahato et al., 2020) . large reductions in co (37.0% -64.8%) and no 2 (24.1% -54.3%) levels were also observed in megacities in south america, like rio de janeiro (dantas et al., 2020) and sao paolo (nakada and urban, 2020) , during the lockdown phase compared to the period before or previous years. in almaty, kazakhstan, co and no 2 levels reduced by 49% and 35%, respectively during the lockdown compared to the 2018-2019 averages of the same period, while pm 2.5 reduced by 21% (kerimray et al., 2020) . the large atmospheric impact of covid-19 in barcelona, spain was detected with a reduction of -45.4% in the bc concentrations and of -47.0% and -51.4% of the no 2 levels at urban-background and traffic sites, respectively (tobias et al., 2020) . lower reductions in the pm 10 concentrations were recorded, in the range of 27.8% and 31.0% at urban-background and traffic sites, respectively, since pm 10 is related to several other sources like regional recirculation, dust resuspension or longrange transport, secondary aerosol formation, constructions, biogenic and marine emissions. this is in agreement with the lower (%) reductions in pm 10 and pm 2.5 concentrations in malaysia compared to those of no 2 . the daily o 3 levels in barcelona increased by 29% to 58% at the urbanbackground and traffic sites (tobias et al., 2020) , while at the urban sites in malaysia, the average increase was much lower (7.3%). the increase in o 3 is mostly attributed to the large decrease in no x levels within a vocs limited urban environment, and to reduction in primary no emissions that lower down the o 3 consumption via titration (kerimray et al., 2020; tobias et al., 2020) . however, changes in o 3 may be also related to changes in insolation that facilitates its production. in milan, italy, which has been severely affected by sars-cov2 (conticini et al., 2020) , lockdown determined a period with a significant reduction in pm 10 , pm 2.5 , no x , co, black carbon and benzene levels, while so 2 remained rather unchanged and o 3 increased due to lower no concentrations (collivignarelli et al., 2020) . a new unpublished research at the time writing this article (shrestha et al., 2020, environ.poll. submitted), analyzed the changes in concentrations of six air pollutants (pm 10 , pm 2.5 , no 2 , so 2 , co and o 3 ) in 40 cities all over the world in february-march 2019 and 2020. in the majority of the cities, the 2020 levels were lower than those in 2019, while after lockdown, significant reductions in no 2 , co, pm 2.5 and pm 10 levels were found in 19, 9, 8 and 7 cities, respectively. summarizing, the worldwide lockdown due to covid-19 pandemic drastically reduced the anthropogenic emissions and air pollution, which, however, is diachronically responsible for acute health issues like chronic obstructive pulmonary disease, which increased significantly the mortality risk due to covid-19. in this study, the impact of the lockdown due to covid-19 on the spatio-temporal variation of main atmospheric pollutants over sea, and particularly in malaysia, was investigated. 39% in the industrial and by 26-31% in the urban areas) and pm 2.5 (20-42% at industrial and 23-32% at urban sites) compared to previous years. a larger decrease occurred in no 2 levels, which reduced by 33-46% in the industrial sites and by 64% in the urban centres. lower reductions were observed for so 2 and co, while o 3 did not record significant changes over the years. the results of this study are indicative of the degree that the restriction measures and the regional lockdown due to covid-19 affected the air pollution over a region with high levels of aerosols and pollutants from non-traffic and non-industrial activities. therefore, aiming to evaluate the covid-19 impact on air quality over the sea region is a real challenge, especially during the pre-monsoon (march-april) period with 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aerosol optical depth over land nox emission reduction and recovery during covid-19 in east china the authors extend their thanks to the ministry of education, malaysia via the fundamental research grant (r.j130000.7852.5f216) and wni wxbunka foundation, japan via research grant r.j130000.7352.4b406 and for providing research funding. we would like to thank the japan aerospace exploration agency (jaxa) and nasa for making himawari-8 and omi data available key: cord-261218-tgbw81ua authors: vardoulakis, sotiris; salmond, jennifer; krafft, thomas; morawska, lidia title: urban environmental health interventions towards the sustainable development goals date: 2020-08-07 journal: sci total environ doi: 10.1016/j.scitotenv.2020.141530 sha: doc_id: 261218 cord_uid: tgbw81ua abstract the aim of the un sustainable development goals (sdgs) is to achieve a better and more sustainable future for all by 2030. since the majority of the global population lives in cities, it is crucial to identify, evaluate and implement urban interventions (such as such as zero carbon housing, active transport, better urban connectivity, air pollution control, clean household fuels, and protection from heat and flood events) that will improve health and wellbeing and make our natural and built environment more sustainable. this virtual special issue (vsi) comprises of 14 diverse case studies, methods and tools that provide suggestions and interventions which directly or indirectly support the achievement of the un sdgs. the united nations 2030 agenda for sustainable development, and its sustainable development goals (sdgs) in particular, have focused the attention of researchers, practitioners and policy-makers on interventions that have the potential to provide multiple benefits ("co-benefits") for health, the environment, and the economy, particularly in urban settings were two-thirds of the world population will live by 2050 (un 2018) . progress towards the sdgs has being made in many areas, but, overall, action to meet the goals is not yet advancing at the speed or scale required to achieve their specific targets and bring about transformational change. in september 2019, the un secretary-general called on all sectors of society to mobilize for a decade of action to accelerate sustainable solutions to the world's biggest challenges, ranging from poverty and gender to climate change, inequality and closing the finance gap (un 2020). many of these challenges are experienced in cities around the world, and particularly in rapidly urbanising low and middle-income countries, which face overpopulation, lack of adequate resources and infrastructure, climate change, urban heat islands, extreme weather, air pollution, and related illnesses, inequalities and productivity losses (salmond et al. 2018; vardoulakis et al. 2016; vardoulakis and kinney 2019) . at the same time, the complex links between the growing burden of non-communicable diseases (such as cancer, cardiovascular, respiratory, neurodegenerative and autoimmune diseases), urban form and environmental quality are becoming increasingly recognised. identifying and promoting effective urban environmental health interventions for addressing the sdgs, such as reducing carbon emissions (goal 13), which can enhance good health and wellbeing (goal 3), is urgent (howden-chapman et al. 2020) . well-planned, sustainable, changes to urban transport, housing, land use, renewable energy generation, and waste management have the potential to lead to improvements in air and water quality and liveability of urban environments providing multiple benefits including improved public health, reduced inequalities and higher productivity in cities . furthermore, the use of smart sensing technologies and mobile platforms, and the development of advanced techniques for the analysis of big data, when applied appropriately, can revolutionise environmental and public health management in cities (salmond et al. 2017) . citizen science, awareness raising and behaviour change campaigns are also expected to have an impact on environmental sustainability and urban health, although it is currently unclear whether benefits of such interventions can be sustained over time (bonney et al. 2016 ). the healthy-polis consortium for urban environmental health and sustainability (www.healthy-polis.org) aims to contribute to the implementation of the sdgs by identifying and evaluating specific policy initiatives, case studies, evidence gaps, and opportunities for research and translation into environmental public health practice in cities around the world. in this virtual special issue, we present a collection of such case studies from 10 countries (4 high income, and 6 middle or low income countries; table 1 ) and discuss their implications for achieving the sdgs (figure 1 ). the research presented in this this virtual special issue, highlights a number of key interventions aimed at achieving the sdgs and their consequent pathways to health and environmental impact. one of the main direct effects of climate change is the increase in global average temperature, as well as in the frequency and severity of extreme weather events (e.g. heatwaves). this has a disproportionate impact on built up areas due to the urban heat island effect, housing overheating and overcrowding, and the vulnerability of the resident population (heaviside et al. 2017) . two of the studies included in the special issue focus on temperature related impacts on health and wellbeing due to the poor thermal performance of houses in brisbane, australia (asumadu-sakyi et al. 2019), and the mitigation strategies aiming to reduce radiant heat load on buildings in korea (park et al. 2020 ). one of the key challenges when attempting to address goal 3 (health and wellbeing) is to improve both ambient and household air quality. xue et al. (2020) focused on satellite-derived air pollution (pm 2.5 ) as an evaluation index for health and wellbeing. in their paper, the temporal trends of pm 2.5 and the quantitative potential impact of environmental governance on pm 2.5 were analysed for china. using environmental regulation intensity and synergy to quantify the influence of governance, they concluded that regulatory measures should be enhanced to further decrease pm 2.5 in the future ( in a different context, adesina et al. (2020) assessed the impact of solid fuel burning in an indoor and ambient environment near coal-fired power plants in south africa using continuous monitoring of pm 4 in two houses, of which only one used coal as a primary source of energy. they found significant differences in indoor air pollution levels during the winter season, but also at times high ambient concentrations, which indicated that decarbonisation of household energy and power generation could bring significant benefits for air quality and public health (adesina et al. 2020) . in a comprehensive analysis of cooking solutions in western africa, co-benefits of clean cooking solutions (goal 7, affordable and clean energy) at household level were analysed in relation to goals 3 (health and wellbeing), 5 (gender equality), and 13 (climate action). interestingly, the most important co-benefit was related to gender equality (goal 5), representing 60-97% of the total economic benefit of the intervention (mazorra et al. 2020). carmichael et al. (2020) explored the use of public health research and evidence in policy to regulate new buildings in england to deliver improved public health, climate resilience and a reduced carbon footprint. they showed that public health evidence was hardly referenced in policy, and that a narrow focus on climate mitigation in building regulations results in both positive and negative impacts on health. this highlights the need for a systems approach around urban interventions (carmichael et al. 2020 ). human vulnerability assessment is an important tool within the scope of goal 13 (climate action), as it can help develop adaptation strategies in the context of regional climate change. vommaro et al. (2020) demonstrated the application of a modelling method to evaluate human vulnerability to climate change in the state of maranhão, brazil. using a municipal vulnerability index based on socioeconomic, demographic, climate, epidemiological, and environmental aspects, they identified the most vulnerable areas under climate change (vommaro et al. 2020 ). wu et al. (2019) identified good practice and lessons learned from china's response to severe flooding in anhui province in 2016. good practice included using early warning systems to advise communities of risks and enforce evacuation in the flood zone, preparing and using schools as shelters with open-ended periods of operation, and providing stable shelter accommodations with medical and public health services, clean drinking water and food, sanitation, and toilet hygiene through multiagency cooperation. they concluded that disaster mitigation strategies needs to be integrated with climate adaptation plans in cities (wu et al. 2019) . two studies from new zealand focused on active transport (macmillan et al. 2020) , and on integrated urban planning and regeneration (howden-chapman et al. 2020) . macmillan et al. (2020) used an active transport case study from auckland to illustrate the complex causal pathways that contribute to achieving several sdgs, including goal 11 (sustainable cities) and goal 10 (reduced inequalities there is limited evidence in research, policies and in the sdgs about the impact of environmental factors on non-communicable diseases (ncds) in urban areas of sub-saharan africa, although 80% of ncds are taking place in low-and middle-income countries and are linked to a third of the deaths in sub-saharan africa. rother (2020) poses the question: what would these statistics look like if environmental risk factors (e.g., pollution, climate change) were prevented and controlled. rother (2020) presents a framework for understanding climatic impacts on climate-sensitive ncds and achieving the sdgs. this explains how current global mitigation interventions in high income urban settings, with implied health co-benefits for ncd reduction (i.e. use of less polluting vehicles, cycling, walking, public transport, green spaces), experience major implementation challenges in sub-saharan african cities (i.e. too costly, lack of availability, poor road conditions, gender and cultural norms, security problems). the article recommends more support for research on the climate-ncd nexus, ensuring health professional training includes sustainable health education, and including a focus on climate change and health in primary and secondary school curricula (rother 2020) . in the decade of action for sdg implementation (un 2020), the recovery pathways from covid-19 are an opportunity for governments, urban planners, environmental public health practitioners, and other stakeholders to build back better our cities (wri 2020). the healthy-polis vsi: urban environmental health interventions towards the sustainable development goals provides diverse evidence, case studies and tools to inspire action in cities and regions around the world, so they can emerge healthier and more sustainable future post covid-19. the interventions and tools discussed can be used to provide multiple environmental health solutions, which are context specific. for this reason, it is important to consider the intended and unintended consequences of these interventions by using a cross-disciplinary systems approach and involving all relevant stakeholders in discussions and decision making. promoting climatesensitive urban policies, such as zero carbon housing, active transport, better urban connectivity, clean household fuels, and protection from heat and flood events, will help improve health and wellbeing in cities as we move towards achieving and sustaining the sdgs. contrasting indoor and ambient particulate matter concentrations and thermal comfort in coal and non-coal burning households at south africa highveld seasonal temperature patterns and durations of acceptable temperature range in houses in brisbane, australia can citizen science enhance public understanding of science? healthy buildings for a healthy city: is the public health evidence base informing current building policies? the urban heat island: implications for health in a changing environment evaluating natural experiments to measure the co-benefits of urban policy interventions to reduce carbon emissions in new zealand verification of a bioclimatic modeling system in a growing suburb in melbourne suburb-level changes for active transport to meet the sdgs: causal theory and a new zealand case study integrating four radiant heat load mitigation strategies is an efficient intervention to improve human health in urban environments controlling and preventing climate-sensitive noncommunicable diseases in urban subsaharan africa towards the integrated study of urban climate, air pollution, and public health can big data tame a "naughty" world? the canadian geographer microenv: a microsimulation model for quantifying the impacts of environmental policies on population health and health inequalities sustainable development goals decade of action challenges and opportunities for urban environmental health and sustainability: the healthy-polis initiative local action on outdoor air pollution to improve public health grand challenges in sustainable cities and health contributions of municipal vulnerability map of the population of the state of maranhão (brazil) to the sustainable development goals after the crisis: how covid-19 can drive transformational change in cities planned sheltering as an adaptation strategy to climate change: lessons learned from the severe flooding in anhui province of china in 2016 satellite-derived spatiotemporal pm2.5 concentrations and variations from 2006 to 2017 in china simulation analysis of natural lighting of residential buildings in xi'an, china we acknowledge in-kind contributions and support from the healthy-polis international consortium for urban environmental health and sustainability. key: cord-286230-0si3pv3e authors: wang, wenlu; yoneda, minoru title: determination of the optimal penetration factor for evaluating the invasion process of aerosols from a confined source space to an uncontaminated area date: 2020-06-10 journal: sci total environ doi: 10.1016/j.scitotenv.2020.140113 sha: doc_id: 286230 cord_uid: 0si3pv3e abstract due to the outbreak and spread of covid-19, sars-cov-2 has been proven to survive in aerosols for hours. virus-containing aerosols may intrude into an uncontaminated area from a confined source space under certain ventilated conditions. the penetration factor, which is the most direct parameter for evaluating the invasion process, can effectively reflect the penetration fraction of aerosols and the shielding efficiency of buildings. based on the observed concentrations of aerosols combined with a widely used concentration model, four numerical calculations of the penetration factor are proposed in this study. a theoretical time-correction p est was applied to a size-dependent p avg by proposing a correction coefficient r, and the error analysis of the real-time p(t) and the derived p d were also performed. the results indicated that p avg supplied the most stable values for laboratory penetration simulations. however, the time-correction is of little significance under current experimental conditions. p(t) and p d are suitable for rough evaluation under certain conditions due to the inevitability of particles detaching and re-entering after capture. the proposed optimal penetration factor and the error analysis of each method in this study can provide insight into the penetration mechanism, and also provide a rapid and accurate assessment method for preventing and controlling the spread of the epidemic. the global outbreak of coronavirus disease has seriously endangered the health and safety of all human beings. scientists have conducted extensive research on the severe acute respiratory syndrome coronavirus 2 (sars-cov-2), referring to transmission dynamics [1] [2] [3] , removal technology [4] , and climate factor [5] . correia et al. (2020) pointed out that improper use of the ventilation system could aggravate the spread of the virus [6] . doremalen et al. (2020) experimentally generated sars-cov-2-containing aerosols with a diameter of less than 5 m, and illustrated that sars-cov-2 can survive and be infectious in aerosols for hours, in some cases even days on surfaces [7] . moreover, it is well known that coronavirus is more likely to exist in confined and poorly ventilated spaces. in this case, aerosols can carry or combine with viruses into an uncontaminated area under certain ventilated conditions. however, the most effective evaluation method for aerosols penetrating from the polluted area or the source area to the unpolluted space is still not clear. in recent decades, the fate of aerosols penetrating from outdoor has received widespread attention from scientists due to the direct relationship with human health [8] [9] [10] [11] [12] . related penetration research is usually carried out in two ways: field measurement and laboratory simulation. field experiments are always conducted in real buildings such as school classrooms, dormitories, and offices [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] , while a test chamber or a building brick is usually used as the object to simulate the indoor or outdoor environment in laboratory simulations [22] [23] [24] [25] [26] [27] . the difference between laboratory simulation and field testing is a greater control of the conditions in a laboratory setting. additionally, the change in concentration of aerosols is one of the basic characteristics in the penetration process. based journal pre-proof j o u r n a l p r e -p r o o f on the law of mass balance, thatcher et al (2003) had represented the indoor concentration over time "t" as [28] , where, c in and c out are the indoor and outdoor particle concentrations (cm -3 ), a is air exchange rate (aer) (h -1 ) associated with ventilation system, k is the rate of particles deposition loss onto interior surfaces (h -1 ), while p is the penetration factor. g, s, f, k and h represent the particle generation from the indoor source, particles for dissociation/vaporization, the formation of new particles due to chemical reactions, the particles for coagulation and for hygroscopic growth (cm -3 h -1 ), respectively. for the source, concentrations, size of particles and the experimental conditions used in most simulations, it is assumed that the effects of dissociation/vaporization (s), new chemical formation (f), coagulation (k) and hygroscopic growth (h) are avoided in the analysis. if the study only focuses on the single penetration process, the indoor source (g) also has no significance. in this case, eq. (1) is simplified to the expression with parameter a, k and p, as similarly, assuming that the particle flow passing from the outdoor compartment is the only path under ideal conditions, the outdoor particle concentration in a confined space could be affected by the air exchange rate "a" of the indoor compartment and the deposition rate "k" of outdoor particles. therefore, the outdoor particle concentration over time can be expressed as, it is assumed that a certain number of particles tend to penetrate from the outdoor compartment at time "t" under the action of a ventilator, but only a portion enters the indoor journal pre-proof j o u r n a l p r e -p r o o f compartment while the rest is trapped by the sash gap. in this case, "p 0 " represents the total proportion of the particles participating in the penetration at a certain aer "a". if those trapped particles do not detach and re-enter the outdoor compartment, p 0 can be estimated as 1. a review of the literature shows that the portion of "p" entering the indoor compartment can be defined as follows: the parameter p, associated with infiltration airflow, denotes the fraction of outdoor particles passing through building cracks, leakage paths and window openings [29] [30] [31] . in eq. (2), "a" and "k" are the only influencing factors, and the equilibrium in the experiments of penetration simulations in recent decades, eq. (4) is widely used for quantification of the particle penetration through building cracks. thornburg et al (2001) reported penetration factor using this equation, and c in and c out were described as the time average of the indoor and outdoor concentrations [29] ; rim et al (2013) mentioned in the derivation that the equation was for the particle size category [31] ; while other literatures defaulted the p value to the size-resolved one [14, 32, 33] . however, there is little reference to the optimal method for determining the p value. j o u r n a l p r e -p r o o f and continuous particle source could not be provided. this is also the limiting factor for laboratory simulations. therefore, two questions require further discussions: (1) "is the parameter p of eq. (4) without a time attribute suitable for the case where the concentration changes in a confined source space?" and (2) "what is the optimal p value?". based on the aforementioned properties of sars-cov-2 regarding its ability to survive in aerosols for hours, fps/ ufps may carry or combine with sars-cov-2 and then penetrate into uncontaminated areas together. to evaluate the invasion process of aerosols from a confined source space to an uncontaminated area, based on our previous work and the widely used concentration model eq. (2)-eq. (4), we will thus be (1) proposing four numerical calculations of penetration factor, the size-dependent p avg , the time-corrected p est , the realtime p(t), and the direct-derived p d ; (2) comparing and evaluating the observed indoor concentrations and the estimated ones; and (3) selecting the optimal p value for penetration process. the proposed optimal p value and the error analysis could help provide insight into the penetration mechanism, and can also provide a rapid and accurate assessment method for preventing and controlling the spread of the epidemic. based on our previous work on penetration simulation for emergency evacuation, fig. 1 gives the schematic of the whole experimental system, including a simulation system and a in this study, the outdoor compartment simulates a closed source space filled with viruscontaining aerosols, where a certain amount of particles (around 1.010 4 cm -3 ) are introduced at the initial moment; while the indoor compartment with an initial concentration close to zero simulates an uncontaminated room. due to the particle flow gradually passing through the crack and entering the indoor compartment while the ventilation system is in operation, the series of the indoor and the outdoor concentrations recorded at every time "t" reported in our previous research exhibits a tendency for continuous attenuation [27] . the aer of the ventilation system was controlled from 0. j o u r n a l p r e -p r o o f assuming c in (t) and c out (t) as the real-time indoor and outdoor concentrations for instantaneous calculation, respectively, and p(t) as the real-time value of penetration factor at time t, or p avg representing the average penetration factor for a short-term evaluation, eq. (4) can be expressed as, and where, c in,avg and c out,avg are the time-averaged concentrations for each particle size. p(t) is "time-dependent/ size-averaged" penetration factor of the indoor compartment, that is, the penetration factor corresponds to the total concentration per minute at the average diameter. p avg is "size-dependent/ time-averaged" penetration factor of the indoor compartment, representing the penetration factor corresponding to the average concentration of 36 minutes at each particle size. however, p avg is a size-dependent parameter without a time property. therefore, the theoretical value p est is introduced for time correction in this study. in case of c in 0, c in (0) and c out (0) represent for the initial conditions. therefore, by integrating eq. (2) and eq. (3), the real-time concentrations at t time can be obtained as follows, considering the continuous change in concentration from 0 to t time, then combined eq. (6), eq. (10) and eq. (12), here, we defined the item " " involving in the parameters "a" "k" and "t" as "correction coefficient r", then so, in case of c in =0, to search for an approximation close to the expected value, a simple equation is visually derived from the ratio of eq. (7) and eq. (8) (assumed p 0 = 1) to directly estimate the penetration factor, j o u r n a l p r e -p r o o f here, p d represents a time series of approximate values over 36 minutes. in case of c in (0) =0, eq. (18) changes to p d can be also used to estimate the penetration factor at a certain time t. compared to p(t) in eq. (5), p d calculated by eq. (19) ignores the effect of k but adds the time attribute. if taking the indoor compartment as the research object, and also fully considering the situation where c out gradually decreases in the laboratory simulation experiment, eq. (3) is where, t represents time interval, and the indoor concentration at "t+t" time is estimated as, in this study, the deposition rate k was approximated using the model of okuyama according to our published work, the value of which is less than 0.25 h -1 with a particle size of less than 500 nm [27, 34] . the penetration factor p, denoted as p(t), p avg , p est and p d , respectively, is substituted into eq. (21) , and the optimal p value is discussed and determined by comparing with the observed indoor concentration over time. j o u r n a l p r e -p r o o f in the experiment, four size segments, 69-100 nm, 100-200 nm, 200-300 nm and 300-500 nm, were divided according to their similar p avg in each segment. fig. 3 gives the relationship between correction coefficient r and the elapsed time (taking 69-100 nm as an example). these curves are extended indefinitely, and they all finally equal to 1. the larger the aer, the shorter the time. as displayed in table 1 , each time average value of p(t), p avg and p d shows a growth trend with the increase of aer, which is consistent with the literature that a high aer corresponds to a high p value when c out is higher than c in [27] , but for p est . in addition, the average values of p avg in the four size segments are gradually approaching that of p est as aer is increasing. moreover, p(t) at an aer of 3.70 h -1 , p d at aers of more than 1. in fig. 4 , the dotted curves present the observed indoor concentration and the estimated concentrations from p(t), p avg , p est and p d at 0.31 h -1 , 1.20 h -1 and 3.70 h -1 , respectively. the curve using the p est value clearly deviates from the observed concentration. it means the time-corrected p est has a large error, while the real-time p(t), the size-dependent p avg and the direct-derived p d are much closer to the expected value. additionally, the change trend of the curves, growth, maintenance and decline, is summarized in table 2 , referring to c out > c in , c out = c in and c out < c in , respectively, which are consistent with the previous reported results j o u r n a l p r e -p r o o f in the case of c in 0, eq. (16) gives the theory relationship between p est and p avg . numerically, the two values gradually approach each other as aer increases (see table 1 ). in eq. (16) there are two terms, " 1 " and " + • (0) (0) ". in the laboratory simulation, the initial concentration can be seen as a constant, and the value of "a" ranges from 0.31 h -1 to 3.70 h -1 with k being negligible compared to the increased aer. therefore, " + " tends to 1 with the increases of aer and the term " " has little effect on the value p est . in the term " 1 ", r plays an important role. as shown in table 3 , the correction coefficient r for different size segment at different aer values will have similar maximum and minimum. generally, correction coefficient r values are all less than 1, ranging from 0.006 to 0.737. therefore, the estimated-p est is around 1.37-167 times larger than the size-dependent p avg . therefore, the time correction under the effect of the correction coefficient r is of little significance due to the simulated ideal experimental conditions in the laboratory, including the good airtightness of the experimental chamber, the mild testing environment, and the controllable particle concentration and ventilation power. in this case, the controllable concentration ratio of the indoor and the outdoor results in the averaged concentrations being similar to the real-time ones. in contrast, it can be speculated that p est could become necessary for the system if the outdoor concentration is much higher than the indoor one, or if there is a large aer (i.e. a »3.70 h -1 ), but further demonstration it still needed. found for smaller ufp (d p <30 nm) the loss due to deposition is substantially higher than that due to aer, and deposition rate k usually decreases to less than 0.1 h -1 at a particle size of more than 100 nm [33] . additionally, both p(t) and p avg originate from eq. (4) and this equation has set "c in (0) = 0" as a prerequisite while p est in eq. (16) and p d in eq. (18) include the condition of "c in (0)  0". it can be considered that p est in eq. (16) and p d in eq. (18) are the corrections of the default item of the initial indoor concentration. in terms of p values, table 1 shows the average and standard deviation of p(t), p avg , p est and p d in four size segments, respectively. a large standard deviation indicates that the variation of p value in the size segment fluctuates greatly over 36 minutes, with the largest errors appearing on p(t) at the aer of 3.70 h -1 . p(t) in eq. (5) contains two terms, " + " and " ( ) ( ) ". for the first term " + ", it has reported that deposition rate k usually < 0.1 h -1 as d p > 100 nm and k < 0.25 h -1 as d p < 100nm [33] [34] , so the term is around 1 to 2 (aer ranges from 0.30 h -1 to 3.70 h -1 ). as we can see in table 1 , the values of p(t) is greater than 1 at a large aer of 3.70 h -1 with the term " based on the experimental basis [27] , the curve of indoor concentration shows three trends during 36 minutes at the three different settings of aers (table 2) . before the decline, the curve of growth and maintenance last 0.233 h (first 14 minutes) at the aer of 3.70 h -1 , that is, p(t) can only be ensured ranging from 0 to 1 before the occurrence of "c out < c in ". additionally, the real-time value is greater than 1, indicating that the indoor concentration is already higher than outdoor and p(t) is no longer applicable for evaluation. different with p(t), the aer "a" and the time attribute "t", contained in the term " 1 ", gives the main contribution to the p d value. as shown in table 1 , p d indicates a higher value than other three p values at a small aer of less than 1.20 h -1 , but the relative errors between the estimated results at p d and the observed concentrations are similar to p(t) and p avg in table 5 ; while in the later period (last 22 minutes) and at a large aer of more than 1.20 h -1 , "a" and "t" " tends to zero). the concentrations estimated from p(t) and p d therefore have more significant errors than the actual observed concentration in the early period prior to 0.233 hours, especially when the aer is more than or equal to 1.20 h -1 (table 5) . similarly, p d in eq. (18) including the term of " " has insignificant correction because the initial indoor concentration tends to zero in this study. additionally, as described in eq. (8), we assumed "p 0 = 1" under the ideal condition, indicating that those trapped particles do not detach and re-enter the outdoor compartment. however, the errors indicate that the assumed p 0 exists and the value of p 0 is less than 1, j o u r n a l p r e -p r o o f implying that detaching and re-entering are inevitable in the actual situation. therefore, in a 36-minute penetration evaluation, both p(t) and p d are applicable to conditions where the aer is less than 1.20 h -1 , but they cannot be equal due to the different derivations. in addition, p(t) can be also used for the late stage at the aer as 1.20 h -1 , and unlike " 1 " in p d , " + " in p(t) has a certain correction effect on the p value under the condition of aer less than 1.20 h -1 . it is worth noting that the estimated result at p avg has small errors among all the p values at each size segment and at each aer in table 5 . like p(t) in eq. (5), the " + " term eliminates the effect from aer to some extent, and c in, avg and c out, avg in eq. (6) therefore, the estimation at p avg is more stable than other values. in contrast, the increase of the aer value tends to decrease the error from p est , i.e. from similarly, a large aer reduces the action time of the r value. in addition, the overall p est value far exceeding 1 indicates its inapplicability in the 36-minute evaluation. similar to p d in eq. (18) , p est in eq. (16) includes the condition of "c in (0)  0" and is insignificant for the correction of p avg due to a low ratio of " " in this study, and may even cause large errors. additionally, for systems with large indoor and outdoor concentration changes or an existing large aer (i.e. a > 3.70 h -1 ), whether or not the error caused by p est would decrease still needs further demonstration. this work proposes four numerical calculations of penetration factor to select the optimal value. in addition, a widely used concentration model is employed to evaluate the penetration process of aerosols from a confined source space to an uncontaminated area within 36 min, and the following conclusions can be applied to the invasion evaluation of virus-containing aerosols. during the 36-minute penetration process in this study, the proposed correction coefficient r has its own time limit if time-correction is necessary under some non-ideal condition. j o u r n a l p r e -p r o o f additionally, size-dependent p avg is time-corrected to be p est by the correction coefficient r. however, the time correction is of little significance due to the simulated ideal experimental conditions in the laboratory within the current experimental 36 min. p est was assumed to be necessary for the system if the confined source space has a much higher initial concentration than the indoor one or there is a large aer (i.e. a »3.70 h -1 ), but it still needs further demonstration. the error analysis of the real-time p(t) and the direct-derived p d proves that the assumed p 0 exists and the value of p 0 is less than 1 in the actual situation, indicating that detaching and re-entering are inevitable. both of them are only suitable for rough evaluation in the case of aer less than 1.20 h -1 and p(t) is also applicable to the later stage when the aer is equal to 1.20 h -1 . additionally, the size-dependent p avg is the optimal value among the four under current experimental conditions, due to minimal 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title: impact of city lockdown on the air quality of covid-19-hit of wuhan city date: 2020-06-30 journal: sci total environ doi: 10.1016/j.scitotenv.2020.140556 sha: doc_id: 344423 cord_uid: jhdfscyw abstract a series of strict lockdown measures were implemented in the areas of china worst affected by coronavirus disease 19, including wuhan, to prevent the disease spreading. the lockdown had a substantial environmental impact, because traffic pollution and industrial emissions are important factors affecting air quality and public health in the region. after the lockdown, the average monthly air quality index (aqi) in wuhan was 59.7, which is 33.9% lower than that before the lockdown (january 23, 2020) and 47.5% lower than that during the corresponding period (113.6) from 2015 to 2019. compared with the conditions before the lockdown, fine particulate matter (pm2.5) decreased by 36.9% and remained the main pollutant. nitrogen dioxide (no2) showed the largest decrease of approximately 53.3%, and ozone (o3) increased by 116.6%. the proportions of fixed-source emissions and transported external-source emissions in this area increased. after the lockdown, o3 pollution was highly negatively correlated with the no2 concentration, and the radiation increase caused by the pm2.5 reduction was not the main reason for the increase in o3. this indicates that the generation of secondary pollutants is influenced by multiple factors and is not only governed by emission reduction. j o u r n a l p r e -p r o o f recently, a new type of coronavirus has caused mass viral pneumonia , thus posing a major threat to international health . at present, the epidemic constitutes a public health emergency of international concern (who, 2020). since the middle of december 2019, a number of family clustering outbreaks and transmission from patients to health-care workers have occurred, which shows that human-to-human transmission has happened through close contact . most countries have imposed city lockdown and quarantine measures to reduce transmission to control the epidemic. the chinese health authorities have made considerable efforts, including the positive detection of cases and retrospective investigation of patient clusters. public risk communication activities have been performed to improve public awareness of self-protection (hui, 2020) . the chinese government has gradually implemented a strict lockdown on wuhan and surrounding cities as of january 23. some processing and light industries have been shut down, and the catering and entertainment industries have temporarily closed, and flights, trains and public transport have been suspended . in addition to reducing the spread of the disease, the lockdown measures may also have additional health benefits. after the lockdown of city traffic, personnel flow control became the most important aspect. traffic pollution produces nitrogen monoxide (no), carbon monoxide (co), carbon dioxide (co 2 ), diesel-exhaust particles, and ozone (o 3 ), nitrogen dioxide (no 2 ), secondary aerosols formed through physical and chemical processes, and pollutants that arise from brake wear, tire wear and re-suspended particles (e.g., trace metals) j o u r n a l p r e -p r o o f 4 (beckerman, 2008 , guo, 2020 . there was a notable association between traffic-related air pollution and premature mortality, and the risk of respiratory and cardiovascular diseases increased in residents living close to high-traffic pollution areas (brugge, 2007 , im, 2019 . reducing the emissions from motor vehicles, especially trucks and buses, could produce considerable health benefits (kheirbek, 2016) . a survey of hospital visits in busan city before and after the asian games shows that the traffic flow control over 14 consecutive days is associated with a significant decline in the hospitalization rate of children with asthma (lee, 2007) . in addition, the reduction in industrial activities after the lockdown also imposes certain environmental and health effects. for example, oil shale mining and power generation processes discharge excessive sulphur dioxide (so 2 ), particulate matter (pm 10 ) and nitrogen oxides (no x ), as well as various other industrial pollutants, such as benzene and phenol, and trace elements (saurabh, 2016) .the spatial lag model with fixed effects demonstrates that industrial air pollution causes an increase in medical expenses (zeng, 2019) . compared to nonindustrial areas, the residents of industrial areas more frequently reported wheezing, chest tightness, shortness of breath, hypertension, heart diseases, etc (orru, 2018) . wuhan is the transportation and trade center of central china, a megacity and national central city of china, with a well-developed transportation system and a large number of motor vehicles. due to the lack of central heating and chemical industry, in addition to the emissions from coal-fired enterprises such as power plants and the pollution transported from surrounding rural biomass burning activities, vehicle emissions are responsible for the most important pollution source affecting the air quality and public health in wuhan (daoru liu, j o u r n a l p r e -p r o o f 5 2020). wang et al. found that regional traffic has a significant impact on the formation of haze in wuhan, and the main potential pollution sources are located in the north and south of wuhan (si wang, 2017) . liao et al. found that the increase in secondary organics (nh 4 ) 2 so 4 and nh 4 no 3 caused by vehicle exhaust and coal burning as well as the increased environmental moisture absorption were the main causes of pollution in wuhan (liao weijie, 2020). in this report, we studied the change in air quality one month before and after the lockdown in wuhan and compared it to that during corresponding periods. we analyzed the real-time concentrations of the six air pollutants monitored by the state control station, including fine particulate matter (pm 2.5 ), pm 10 , so 2 , no 2 , co, and o 3 , and compared the effects of the lockdown on the concentrations of the different pollutants. we studied the changes in pm 2.5 , no 2 , and o 3 in hubei province one month before and after the closure of major cities severely affected by the epidemic and to further analyze the impact of human activities and the lockdown on atmospheric pollutant concentrations. the daily aqi data of wuhan, from 1 january 2016 to 31 february 2020, were provided by the wuhan ecology and environment bureau (http://hbj.wh.gov.cn/). the ground observation daily data of hubei province were provided by the china national environmental monitoring centre (http://www.cnemc.cn/). considering the retention of air pollutants, the data from 24 january 2020, to 23 february 2020, are selected as the representative data after j o u r n a l p r e -p r o o f 6 the lockdown, and the data from 24 december 2019, to 23 january 2020, are selected as the representative data before the lockdown. the historical data for the sake of comparison during the same period is from 24 january to 23 february, 2015-2020, which includes the yearly chinese spring festival holiday. all monitoring instruments of the wuhan air quality automatic monitoring system operate automatically 24 h a day. the monitoring items are pm 2.5 , pm 10 , so 2 , no 2 , co and o 3 . the automatic monitoring of pm 2.5 and pm 10 adopts the micro-oscillating balance method and the β-absorption method, respectively (ambient air quality standards, gb 3095-2012), and their measuring instruments are a tapered element oscillating microbalance (teom) (rupprecht & patashnick co, usa) and a bam 1020 (met one instrument, usa), respectively. so 2 , no 2 , co and o 3 were measured by instruments of tei-43i, tei-42i, tei-48i and tei-49i (thermo fisher scientific, usa), respectively. the experimental methods are as follows the ultraviolet fluorescence method (so 2 ), the chemiluminescence method (no 2 ), the nondispersion infrared absorption method and gas filter correlation infrared absorption method (co), and the uv-spectrophotometry (o 3 ). the average air quality index (aqi) is a dimensionless index, which is calculated according to the chinese ambient air quality standard (g b3095-2012) and includes six pollutants in the calculation, i.e., so 2 , no 2 , pm 10 , pm 2.5 , o 3 and co. the subindex of each pollutant is first calculated according to the fractional concentration and is labeled iaqi p . in equation (1), iaqip is the air quality subindex of pollutant p; c p is the mass concentration of pollutant p; bp hi is the upper limit value of the pollutant concentration close (1) j o u r n a l p r e -p r o o f 7 to c p in table 1 ; bp lo is the lower limit value of the pollutant concentration close to c p in table 1 ; iaqi hi is the air quality subindex corresponding to bp hi in table 1 ; and iaqi lo is the air quality subindex corresponding to bp lo in table 1 . when the aqi is higher than 50, the pollutants with the highest air quality subindex are the primary pollutants. if there are two or more pollutants with the highest air quality subindex, they are listed as the primary pollutants. in addition, the pollutants with an iaqi higher than 100 are overstandard pollutants. a high aqi indicates that serious and concentrated air pollution will not only affect the outdoor activities of humans but also damage their health. the main administrative regions of wuhan are relatively concentrated and the population difference is notable, the population density decreases from the central regions to the peripheral regions ( fig. 1a) . after the lockdown, the aqi in the different administrative regions in wuhan decreased, of which the air quality at wujiashan station and qiaokou gutian station exhibited the most notable improvement (decreasing 37.4% and 37.3%, respectively), while xinzhou district station attained the smallest decrease of 15.5%. the results show that the aqi improvement rate increased with the increase in population density ( fig. 1b) . the average aqi improvement rate in districts with a population density of less than 5,000 was 25.7%, whereas that in areas with a population density of more than 20,000 was 34.9%. this difference was due to the frequent traffic congestion in populated areas j o u r n a l p r e -p r o o f 8 before the blockade, leading to additional emissions of exhaust gas. the wear and tear of roads, tires, and brakes caused by congestion are also sources of particulate matter (han, 2019) . furthermore, the high density of buildings reduces the wind speed and the diffusion of air pollution . after lockdown, of the nine state-controlled monitoring sites (excluding the background station), hanyang yuehu station had the lowest aqi (54.1) because the site is far from the city's main roads and industrial areas. qingshan ganghua station had the highest aqi (73.2) because it is close to wuhan iron and steel corporation. studies have shown that the contribution rate of pm 2.5 from steel industry pollution sources in wuhan in winter is second only to traffic sources, up to 30.8% (huang, 2019) . therefore, the high aqi of the site during the implementation of government intervention measures may be mainly influenced by heavy industry sources. 3.2. a comparison of the aqi from 2020 with that in 2015-2019 for the same period and before the control. we selected the period december 24, 2019 to january 23, 2020 as the period before the lockdown, and compared this period with the historical corresponding periods of january 24 to february 23 from 2015 to 2019. after the lockdown, the average aqi in wuhan was 59.7, a decrease of 47.5% compared to that during the corresponding period from 2015-2019 (fig. 2a ). compared with before the lockdown, the average aqi decreased by 33.9%, and the differences among monitoring sites also decreased significantly (fig. 2b) . the rate of days j o u r n a l p r e -p r o o f 9 with an aqi <100 was 96.8%, of which 41.9% had an aqi < 50, without moderately and severely polluted days. compared with the corresponding periods, the rate of good days (aqi < 100) increased by 37.4%, which means that during the lockdown, the air quality in wuhan had no significant effect on human health, and only some pollutants may have had a weak impact on the health of a small number of unusually sensitive people. among the 18 pollution days, pm 2.5 was the primary pollutant on 16 days (88.9%), pm 10 and o 3 were the primary pollutants on 1 day (5.6%). on the lightly polluted day (february 5), pm 2.5 and pm 10 both increased considerably. therefore, after the lockdown, the most important influencing factor of the aqi is pm 2.5 in wuhan. the proportion of days with an iaqi pm2.5 < 100 increased substantially, with three stations reaching 100%. this is due to reductions in vehicle emissions and the closure of some industrial plants during government controls, which caused black carbon, organic components, sulphate particulate matter and important precursors such as so 2 , no x and hydrocarbons (ch x ) to be reduced to some extent (richmond-bryant, 2009 ), (daellenbach, 2016) . after the lockdown, the rise of o 3 led to the first polluted day in winter in wuhan with o 3 as the major pollutant since 2015. there were no days with no 2 as the main pollutant during the control, which was a significant improvement compared with the historical period from 2015 -2019 and before the control period. 3.3. the evolution of the pollutant concentration during the lockdown. compared with the average concentration during the historical 2019 period and before the lockdown, the pm 10 , pm 2.5 , so 2 , no 2 , and co concentrations all decreased to some extent, whereas the o 3 concentration increased greatly during the lockdown (fig. 3) . the spatial differences in the pollutant concentrations were small. due to the reduction in fugitive dust caused by the reduction in vehicles and the stoppage of construction after the lockdown, pm 10 decreased by 40.2% compared to before the lockdown. the monthly average pm 2.5 /pm 10 ratio was 0.9, so pm 2.5 was the main particle pollutant that decreased by 36.86% (aldabe, 2011) . no 2 exhibited the most notable improvement, with an average concentration reduction of approximately 53.3%, due to no 2 is highly correlated with traffic pollution. according to the transportation index data, the decrease in national traffic volume was estimated to be 70% during the lockdown (xin .o 3 is an important secondary pollutant in warm months but is generally less important in winter. compared with the conditions before the control measures, the o 3 concentration increased by approximately 116.6%. this may be related to the change in the primary pollutant concentration and meteorological conditions. in addition, o 3 lasts longer in cold weather, which may contribute to its accumulation . the smaller decrease in so 2 of only 3.9% may be related to the increase in domestic heating and cooking during the lockdown period. compared with the summer of 2019, the so 2 concentration only increased by approximately 0.6 μg/m 3 . this shows that the so 2 emissions in wuhan mainly come from power plant emissions and industrial and domestic coal combustion, and the correlations with traffic and heating were low. co is a product of domestic combustion and power generation. the average co j o u r n a l p r e -p r o o f 11 concentration was 0.9 mg/m 3 (down 22.7%), and the decrease in co varied greatly among different sites, from 3.2% to 34.5%. 3.4. the diurnal variation in the pm 2.5 , no 2 and o 3 concentrations. the average daily variation data for 1 month before and after the blockade were selected to analyze pm 2.5 , no 2 , and o 3 . because pm 2.5 comes from complex sources and the generation of secondary aerosols is affected by a variety of factors, the average daily variation range of pm 2.5 is small and highly discrete. the daily variation trend in pm 2.5 after the lockdown was similar to that before, although the range of variation increased and a significant decrease occurred at 18:00, which was attributed to the vertical expansion of the boundary layer and the vertical diffusion of pollutants during the day. (shi, 2020) (fig. 4a) . the concentration of no 2 prior to the lockdown showed a peak in the morning and during evening traffic hours (8-11 a.m. and 6-9 p.m., respectively). however, during the lockdown, no 2 did not exhibit peaks associated with morning rush hours, further indicating that traffic was not a major source of no 2 during this period (fig. 4b) . before the lockdown, the diurnal peaks in o 3 occurred at 7:00 and from 15:00. after the lockdown, the range of the daily variation increased considerably. only the peak from 15:00 was retained and some deviation occurred. in contrast to the control before the lockdown, o 3 showed a downward trend from 00:00 to 10:00, which may be related to the decrease in no 2 in the peak morning period. when o 3 reached its maximum value, no 2 and pm 2.5 decreased to the minimum values. this was probably due to the photolysis consumption of no 2 and the attenuation of solar radiation j o u r n a l p r e -p r o o f 12 caused by the reduction of pm 2.5 accelerating the formation of o 3 . (ma, 2019) (fig. 4c) . in the actual atmosphere, the o 3 concentration is also affected by meteorological elements and important precursors such as volatile organic compounds (vocs) and co. when the voc concentration and no x ratio are unbalanced, this will also affect the steady-state cycle (chung, 1996) . in the atmosphere, [no 2 ]/[so 2 ] is often adopted to indicate the change in the contribution rates of mobile and fixed emission sources. studies have reported that the so 2 emissions from motor vehicles in northern china is far lower than the nox emissions, and the emission ratio of [no 2 ]/[so 2 ] from motor vehicles ranged from 24 to 119 (fiedler et al., 2009 ). both no x and so 2 are discharged from stationary sources, with relatively more so 2 . the ratio of [no 2 ]/[so 2 ] from stationary sources ranged from 0.2 to 0.8 (fiedler et al., 2009) . after the lockdown, [no 2 ]/[so 2 ] decreased significantly (p < 0.01), and the contribution rate of fixed sources increased (factories, power plants, chimneys and boilers, etc.), while the contribution rate of mobile sources decreased, which was consistent with the reduction in vehicle emissions (fig. 5a) can be adopted to roughly evaluate the impact and contribution of local pollutant discharge and external pollutant transportation on the pollution process, with higher ratios indicating higher local contributions (tang, 2015) . after the lockdown, [co]/[so 2 ] decreased significantly (p < 0.01) in wuhan, which indicated that the contribution rate of local emissions decreased, and the air pollution in local areas was affected by surrounding or remote sources (fig. 5b) . the transport pathways in wuhan were identified to be the northwest, east and south pathways (with relative contribution rates of 40%, 17% and 43%, respectively), and the major potential source regions were western henan, northern shanxi and southwestern shanxi (huang, 2019) . 3.6. the air quality improvement in hubei province during the lockdown period. as shown in fig. 6 , 12 cities in hubei province were selected for analysis. after the lockdown, the average monthly pm 2.5 concentration in each city ranged from 31.2 μg/m 3 (xianning) to 64.6 μg/m 3 (xiangyang). according to the chinese ambient air quality standards (caaqs) (gb3095-2012), the average monthly iaqi pm2.5 in xianning city was 44, thus reaching good level, and the average monthly iaqi pm2.5 values in the other 11 cities were moderate. the reason for the high pm 2.5 concentration in xiangyang may be that the area has a large population, and the area of cultivated land ranks first in hubei province, which generates more agricultural pollution (ammonia-nitrogen fertilizers) (wu, 2016) . the improvement rate of no 2 is substantially higher than other pollutants, with an average concentration range of 8.1 μg/m 3 (xianning) -21.4 μg/m 3 (wuhan) after the lockdown. the j o u r n a l p r e -p r o o f 14 average concentration range of o 3 was 73.0 μg/m 3 (xianning) -88.2 μg/m 3 (jingmen), which was much higher than that before the lockdown, and it did not exceed the air quality standards in terms of potentially harming human health. the improvement rates of the aqi and pm 2.5 are lowest, 23.7% and 28.6%, respectively, when the population density ranged from 400-800 person/km 2 . the population density of wuhan reached 1,304.6 person/km 2 , and the improvement rate was significantly higher than that in the other cities except yichang and xianning. the transportation industry in yichang and xianning is relatively well developed, and the passenger traffic volume was larger than 50 million in 2018 in xianning (statistics., 2020). the restrictions on vehicles during the control period may be the main reasons for the high improvement rate of pm 2.5 in the two regions. (khalil, 1988) . after the lockdown, the decline in co was far lower than 50%, and there was no clear trend of daily co change, which shows that after the lockdown, the co emissions from industrial boiler fuel and domestic coal combustion in the wuhan area j o u r n a l p r e -p r o o f 15 account for a large proportion. the main source of gaseous so 2 is the combustion of sulfur-containing fuels (oil, coal and diesel) . after the control period, the so 2 improvement was not distinct. on the one hand, many coal-fired industries were not shut down, mainly due to the effectiveness of pollution control in recent years. compared to 2015, the so 2 concentration decreased 20.5 μg/m 3 , which is due to the upgrading of key industrial industries (power and steel), especially the role of the ultralow emissions of electric power generation, elimination of small and medium-sized coal-fired boilers, conversion of rural heating from coal to gas and electricity and other policies in recent years. the drop in pm 2.5 and pm 10 after the lockdown was not as major as expected, which may be related to a number of factors. first, after the lockdown, the most intensive control concerned traffic, and traffic pollution is not the most important source of pm 2.5 in wuhan (zong, 2020) . second, since the implementation of the national policy on smog governance, the fine particulate emissions in china have been effectively controlled, especially in areas where central heating is generally not provided, such as central and southern china . since 2013, the national average annual concentration of pm 2.5 has dropped substantially, and the number of heavily polluted days has decreased drastically, especially in autumn and winter (ministry, 2020b). third, due to the epidemic control period and the return of migrant workers, the proportion of bulk coal heating users has increased, which may also have mitigated some of the reductions in pm 2.5 , no x and so 2 due to the decreased vehicle emissions (ministry, 2020a) . recently studies have shown that the formation of secondary particles significantly enhanced during the lockdown (xin huang, 2020). in the j o u r n a l p r e -p r o o f 16 early stage, wuhan coal combustion was the main source of no x (41.0% ± 13.7%), and motor vehicle emissions were the second main source (21.8%) from 2013 to 2014 (zong, 2020) . after the implementation of emission standards of coal-fired power plants, multiple technical improvements such as scr, sncr, etc, greatly decreased the no 2 emissions from coal-fired sources, which further led to the most notable improvement in no 2 after the traffic control due to the increasing of the proportion of no 2 traffic source emissions. at present, o 3 pollution has occurred in most parts of china in summer and tends to be a complex type of air pollution (pm 2.5 pollution in winter and o 3 pollution in summer). this study shows that the o 3 concentration may also become a major pollutant in winter, requiring further analysis of the reasons for its rise to avoid more serious o 3 pollution in winter. after the lockdown, the no x control effect is very distinct; however, the effectiveness of the voc control measures needs to be further studied. a change in no x to voc ratio may also lead to an increase in o 3 generation (owoade, 2015) . the transformation and connection between pollutants in terms of the quality and quantity are very complicated. although no x is one of the precursors of o 3 , no x reduction has a negative effect on the o 3 concentration. therefore, the generation of secondary pollutants is affected by multiple factors, and its governance is not only related to emission reductions. meteorological elements play significant roles in air pollution formation, transport, deposition and transformation. the relatively low relative humidity and wind speed in winter are conducive to the generation and resuspension of dust, and the height of the boundary layer is low, while precipitation is low, which is conducive to the accumulation of secondary j o u r n a l p r e -p r o o f sulfate and nitrate (miao, 2018) . in wuhan, the formation of o 3 at the urban site is controlled by voc s , while the formation of o 3 at the urban site is controlled by voc s and no . voc s is greatly affected by pollution sources, photochemical reaction processes and regional transportation . a recent study by wang et al suggested that meteorological conditions in most chinese cities caused an increase in pollutants that outweighed the positive impact of emission reductions during covid-19 outbreak, but for wuhan, unfavorable meteorology had less effect compared with emission changes . however, the reason for the increase in o 3 needs to be combined with meteorological conditions of photochemical production for further research. our results show that the air quality in hubei province and wuhan improved significantly during the covid-19 lockdown, with concentrations of all six standard pollutants, except o 3 , dropping to some extent with the largest decrease in no 2 . the significant increase in the o 3 concentration may be related to the changes in no 2 , voc s , and pm 2.5 , and the reaction mechanism should be studied further in combination with meteorological elements and the photochemical mechanism. air pollution is a complex problem linked to multiple factors. the reduction in pollutant discharge will improve air quality, but it may also bring new problems. the generation mechanism of secondary pollutants should be investigated to provide a more comprehensive scientific basis for formulating pollution prevention and control policies. dr. jianping huang(hjp@lzu.edu.cn)and dr. rujin huang are co-corresponding author. chemical characterisation and source apportionment of pm 2.5 and pm 10 at rural, urban and traffic sites in navarra (north of spain) correlation of nitrogen dioxide with other traffic pollutants near a major expressway near-highway pollutants in motor vehicle exhaust: a review of epidemiologic evidence of cardiac and pulmonary health risks development of ozone-precursor relationships using voc receptor modeling characterization and source apportionment of organic aerosol using offline aerosol mass spectrometry variation trends and principal component analysis of nitrogen oxide emissions from motor vehicles in wuhan city from east asian so 2 pollution plume over europe &ndash; 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nascimento, maria são josé; soares, ruben r.g.; sousa, sofia i.v.; mesquita, joão r. title: airborne spread of infectious sars-cov-2: moving forward using lessons from sars-cov and mers-cov date: 2020-10-08 journal: sci total environ doi: 10.1016/j.scitotenv.2020.142802 sha: doc_id: 350925 cord_uid: 1h6pbfwp background although an increasing body of data reports the detection of sars-cov-2 rna in air, this does not correlate to the presence of infectious viruses, thus not evaluating the risk for airborne covid-19. hence there is a marked knowledge gap that requires urgent attention. therefore, in this systematic review, viability/stability of airborne sars-cov-2, sars-cov and mers-cov viruses is discussed. methods a systematic literature review was performed on pubmed/medline, web of science and scopus to assess the stability and viability of sars-cov, mers-cov and sars-cov-2 on air samples. results and discussion the initial search identified 27 articles. following screening of titles and abstracts and removing duplicates, 11 articles were considered relevant. temperatures ranging from 20 °c to 25 °c and relative humidity ranging from 40% to 50% were reported to have a protective effect on viral viability for airborne sars-cov and mers-cov. as no data is yet available on the conditions influencing viability for airborne sars-cov-2, and given the genetic similarity to sars-cov and mers-cov, one could extrapolate that the same conditions would apply. nonetheless, the effect of these conditions seems to be residual considering the increasing number of cases in the south of usa, brazil and india, where high temperatures and humidities have been observed. conclusion higher temperatures and high relative humidity can have a modest effect on sars-cov-2 viability in the environment, as reported in previous studies to this date. however, these studies are experimental, and do not support the fact that the virus has efficiently spread in the tropical regions of the globe, with other transmission routes such as the contact and droplet ones probably being responsible for the majority of cases reported in these regions, along with other factors such as human mobility patterns and contact rates. further studies are needed to investigate the extent of aerosol transmission of sars-cov-2 as this would have important implications for public health and infection-control policies. hcov-oc43, hcov-nl63, hcov-hku1, severe acute respiratory syndrome virus (sars-cov), middle east respiratory syndrome virus (mers-cov) and the emerging sars-cov-2 (responsible for covid-19) (shereen et al., 2020; ye et al., 2020) . coronaviruses usually infect the cells from the respiratory tract and are responsible for different respiratory diseases that range from mild disease to severe acute respiratory syndromes (rothan and byrareddy, 2020; talbot et al., 2008) . human coronaviruses represent a major problem for human health and impose a tremendous economic burden (keogh-brown and smith, 2008; paules et al., 2020) . these viruses are considered a leading cause of morbidity and mortality in humans worldwide, as seen with the past sars and mers outbreaks (kim et al., 2017; qiu et al., 2018) and the current covid-19 global pandemic (peeri et al., 2020) . globally, as of 10:52am cest, 24 september 2020, there have been 31,664,104 confirmed cases of including 972, 221 deaths, reported to the world health organization (who) (who, 2020). viral respiratory infections are known to be spread by contact (direct or indirect) with secretions expelled by the infected person, or through air via droplets and aerosols (kutter et al., 2018) . contact transmission can happen when a healthy person comes in close contact with an infected person (direct contact) or surfaces (fomites) where viruscontaining droplets expelled by an infected person have been deposited (indirect contact) (morawska and cao, 2020) . transmission of viruses through air can happen via droplets or aerosols generated during coughing, sneezing, talking, singing or breathing (jones and cov-2 is that most studies performed only focused on the detection of viral rna and do not correlate to the infectivity of these viral particles. there is an inherent high technical complexity that also hampers the confirmation of the aerosolized sars-cov-2 infectiousness, requiring viral replication to differentiate viable from non/viable virus and including a number of particular methodological requirements, namely proper specimen selection, collection, transport, and storage that preserve viral infectivity (leland and ginocchio, 2007) . provided recent guidelines recommending that handling of material with high concentrations of viable sars-cov-2, such as when performing virus propagation, should be performed only in laboratories capable of meeting strict containment requirements and practices (biosafety level-3), limiting the number of institutions capable of assessing aerosolized sars-cov-2 viability (blacksell et al., 2020; cdc, 2020) . considering the many structural and genetic similarities between sars-cov, mers-cov, and sars-cov-2 (petrosillo et al., 2020) , and taking into consideration previous studies about sars-cov and mers-cov that point out the potential for airborne transmission of these viruses (eissenberg et al., 2020; kutter et al., 2018; olsen et al., 2003; pyankov et al., 2018; qian and zheng, 2018; ramanathan et al., 2020; tellier et al., 2019; yu et al., 2004; zhao et al., 2011) , the likelihood for airborne transmission of sars-cov-2 is very high (morawska and cao, 2020; tellier et al., 2019) . however, to date, only five studies have provided information on sars-cov-2 viability in air (binder et al., 2020; lednicky et al., 2020; lednicky et al., 2020a; santarpia et al., 2020; van doremalen et al., 2020) . thus, there is a marked knowledge gap that requires urgent attention. an opportunity for advancing research in airborne transmission of sars-cov-2 j o u r n a l p r e -p r o o f journal pre-proof is by comparison to the viability of sars-cov and mers-cov. therefore, in this systematic review, the viability/stability of aerosols containing sars-cov and mers-cov viruses will be discussed to provide information on potential mitigation strategies for sars-cov-2 airborne transmission. the present review includes studies published in the past 18 years (1 january 2002 to 25 september 2020), since the emergence of sars-cov (who, 2002) and mers-cov (who, 2012) , in the following databases: pubmed/medline, web of science and scopus. no language restrictions were imposed during the search, retrieving only one article in chinese. with no prior review articles on this topic, an exhaustive search was made, and published research articles were included. the following search terms were used: -sars‖, -mers‖, -airborne‖, -viability‖, -stability‖, -virus‖, -aerosol‖, -coronavirus‖, and -air sample‖. a total of 27 articles were found with potential interest from the initial search and their titles were screened based on their context of research. from those, 20 articles remained, and their abstracts were appropriately reviewed. after this, exclusions were performed based on the following criteria: i) if the virus studied was sars-cov, mers-cov or sars-cov-2; and ii) if the viability of the virus sampled from air was assessed. using these criteria, 18 articles were excluded and 10 additional relevant articles were found while reading the selected articles, with 1 article being excluded. summarizing, 11 articles were reviewed in detail. figure 1 shows the flowchart with the number of studies identified and included/excluded following the preferred reporting items for systematic reviews and meta-analyses (prisma) statement (moher et al., 2009 ). the databases were independently screened by all authors, and relevant information j o u r n a l p r e -p r o o f was extracted. differences on opinions about whether to include an article or not were solved by consensus between all the authors. the selected articles evaluated concerning the objective of the research, sampling site/methods and main conclusions are compiled in table 1 . viral infectivity is defined as the capacity of the virus to attach and enter the host cell and use its resources to ultimately produce new infectious virions (rodríguez et al., 2009 ). in the case of enveloped viruses such as coronaviruses, viral entry is initiated by the interaction of the viral particle with specific proteins on the cell surface. after initial binding of the receptor, these enveloped viruses fuse their envelope with the host cell membrane to deliver their capsid to the target cell (belouzard et al., 2012) . the capsid also confers protection to the viral genome by preventing its degradation by nucleases and other abiotic stresses. therefore capsid integrity is a critical attribute for the virus to successfully infect a host cell (cliver, 2009 ). among the reviewed literature, only a few papers explored viral viability in air samples (agranovski et al., 2004; binder et al., 2020; booth et al., 2005; kim et al., 2016; lednicky et al., 2020; lednicky et al., 2020a; pyankov et al., 2018; santarpia et al., 2020; van doremalen et al., 2013 van doremalen et al., , 2020 xiao et al., 2004) . remarkably, the majority of the literature focuses exclusively on the detection of viral rna in air samples (cheng et al., aiming at simplifying the determination of viral infectivity, alternative strategies to cell culture and tcid 50 determination have been explored. these strategies resort typically combining rt-pcr with a pre-processing step aiming at deconvoluting viable from non-viable virus particles prior to amplification (goyal and cannon, 2006) . a few examples of these methods are (1) enzymatic pre-treatments (such as ribonuclease) (escudero-abarca et al., 2014; monteiro and santos, 2018; nuanualsuwan and cliver, 2002; rönnqvist et al., 2014) ; (2) pre-treatments with intercalating dyes for detection of damaged capsids (leifels et al., 2015; moreno et al., 2015; parshionikar et al., 2010; randazzo et al., 2018) ; (3) porcine gastric mucin binding (dancho et al., 2012; kingsley et al., 2014) ; (4) antibody binding (ogorzaly et al., 2013) ; and (5) integrated cell-culture pcr assays (blackmer et al., 2000; dunams et al., 2012) . overall, developments in these alternative viral infectivity analytical strategies, largely unexplored in the context of current and past coronavirus pandemics, is of paramount importance to enable not only routine fundamental insights into the effective spread of the virus and its societal impact, as well as enabling effective biosensing strategies for on-site determination of viral infectivity. both these currently unpaved avenues are critical to uncover the true impact of airborne spread of sars-cov-2. lednicky et al., 2020; razzini et al., 2020; santarpia et al., 2020; santarpia et al., 2020a santarpia et al., , 2020b zhou et al., 2020) . previous work with sars-cov showed that viral rna, as well as viable virus, were found in air samples (booth et al., 2005; xiao et al., 2004) . several other studies have reported that sars-cov airborne transmission was the main transmission route in indoor cases studied in hong kong's prince of wales hospital xiao et al., 2017; yu et al., 2005) , health care facilities in canada (booth et al., 2005) and in aircraft (olsen et al., 2003) . these results suggest that both sars-cov and sars-cov-2 can potentially be transmitted by aerosols and cause disease, therefore supporting potential airborne transmission. the presence of mers-cov was also confirmed by rt-pcr of viral cultures of 4 out of 7 air samples from two hospitals in south korea (kim et al., 2016) , and showed to be very stable in aerosol at 20°c and 40% relative humidity (van doremalen et al., 2013) . furthermore, the virus demonstrated relatively high robustness in the airborne form under controlled laboratory conditions (pyankov et al., 2018) , suggesting that mers could also be transmitted by aerosols. although not investigating sars-cov-2 viability, some studies suggested that j o u r n a l p r e -p r o o f airborne transmission might occur (buonanno et al., 2020; cai et al., 2020; hamner et al., 2020; . reported that up to 73% of infected patients reported having had no contact with a person with respiratory symptoms or exposure to relevant contaminated areas, which could be explained by a possible airborne transmission of the virus. ong et al., (2020) also showed that air outlet fans located high on the wall behind the bed of one infected patient were contaminated with sars-cov-2, suggesting that virus-containing aerosols produced by the isolated patient were displaced by airflow and deposited on the vents. moreover, sampling methods and environmental conditions are very important factors to consider when studying viral viability and stability in aerosols because air sampling techniques can also affect the viability of virus recovered from air (tseng and li, 2005; verreault et al., 2008) . problems such as inefficiency at the collection of fine particles, dehydration of viruses during the collection process, damage of the viruses during collection due to impaction forces resulting in the loss of viability of some or all the collected viruses, re-aerosolization leading to the loss of viruses from the collection media, and losses due to viruses being trapped by the inlet or the samplers' wall should be taken into consideration when interpreting the results of experiments involving air sampling. noteworthy, samplers based on technologies such as the water-based condensation are considered more suitable for these studies (pan et al., 2016; yu et al., 2018) . physical characteristics of the environment such as ultraviolet light (uv), temperature, relative humidity, as well as wind currents and ventilation systems, are critical environmental factors that will determine the settling time of airborne particles (alonso et al., 2015) . there are three types of uv light: uva (320-400 nm), uvb (280-320 nm), and uvc (200-280 nm) . uvc is known to be absorbed by rna and dna bases, resulting in the photochemical fusion of two adjacent pyrimidines into covalently linked dimers, which in turn lose the ability to pair with each other (perdiz et al., 2000) . previous studies have shown that uvc is able to inactivate aerosolized coronaviruses (darnell et al., 2004; walker and ko, 2007) , with more recent studies on the subject reporting that simulated sunlight is also able to inactivate airborne sars-cov-2, highlighting the hypothesis that persistence and exposure risk to airborne viruses might vary between indoor and outdoor environments schuit et al., 2020) temperature is another significant factor for virus survival because it can affect the state of viral proteins and the virus genome (price et al., 2019) . temperatures above 60 °c for more than 60 min are thought to be sufficient to inactivate most enveloped viruses, and depending on the presence of any surrounding organic material such as saliva, the virus might be insulated against extreme environmental changes (tang, 2009) . in a study by pan et al. (2019) , it was reported that artificial saliva could better protect infectious viruses from deactivation by preventing viruses of reaching the air-water-interface, possibly due to the complex structure of the mucin component. in a similar study, woo et al. (2012) reported that the inactivation efficiency of droplet and aerosolized viruses under different humidity levels and uv irradiation at a constant intensity were low in artificial saliva, indicating that solids present in it might exhibit a protective effect. the relative humidity is also significant for virus survival and stability because phospholipid-protein complexes in enveloped viruses are usually more likely to denature in the air at medium to high relative humidity. in contrast, the protein coats of nonenveloped viruses denature easier at low relative humidity (sobsey and meschke, 2003) , which explains why most enveloped viruses tend to survive longer at a lower relative j o u r n a l p r e -p r o o f humidity (tang, 2009 ). in addition to that, when faced with high humidity, such as in tropical regions as the amazon rainforest where relative humidity values can get close to 100% during the rainy season, viruses are associated with larger droplets that settle down much faster, which can be a limiting factor to transmission (yang and marr, 2011) . in an attempt to study the effects of temperature and relative humidity on the viability of the sars-cov, a study found that low temperature and low humidity was able to prolong survival of virus on contaminated surfaces (chan et al., 2011) . the same was found to be true for mers-cov. a study reported the stability of mers-cov at 20°c and 40% relative humidity; 30°c and 30% relative humidity; and 30°c and 80% relative humidity, and concluded that mers-cov was more stable at lower temperature and lower humidity conditions (van doremalen et al., 2013) . in another study, two sets of climatic conditions were used in order to establish the inactivation of mers-cov: one represented the common indoor office environment (25°c and 79% relative humidity) and the other represented the climatic conditions of the middle eastern region where the virus outbreak started (38°c and 24% relative humidity) (pyankov et al., 2018) . authors found that the virus had a better survival rate at a lower temperature, with virus decay being higher in hot and dry air. in a recent study, atomic force microscopy was applied to investigate the topographical changes of sars-cov-2 virions exposed to high-temperature treatments, reporting that after the treatment, the virus had much fewer less distinct spikes, their trigonal shape not being able to be resolved, suggesting heat-induced inactivation of sars-cov-2 (kiss et al., 2020). another study reported that the virus was stable at 4 °c in virus transport medium, but sensitive to heat, and that at 22 °c and 65% relative humidity had a negative effect on viral survival on smooth surfaces (chin et al., 2020) . other studies have reported the effects of humidity and temperature on sars-cov-2 j o u r n a l p r e -p r o o f transmission based on meteorological data and statistical analysis (auler et al., 2020; ma et al., 2020; méndez-arriaga, 2020; meo et al., 2020; meyer et al., 2020; sajadi et al., 2020; ward et al., 2020; wu et al., 2020; xie and zhu, 2020; yao et al., 2020) . although all of them have reported a correlation between temperature and relative humidity and the number of new covid-19 cases, there is still some controversy regarding whether one or both variables have a positive, negative or no effect on the number of new cases. the main outcomes of these studies are presented on table s1 (supplementary material). given the genetic and structural similarities between sars-cov, mers-cov and sars-cov-2, one might suggest that higher temperatures and relative humidities could have an impact on the viability of sars-cov-2 in the environment. nonetheless, the effect of these conditions seems to be residual (meyer et al., 2020; wu et al., 2020) considering the increasing number of cases in the south of usa, brazil and india, where high temperatures and humidities have been observed. moreover, it should be noted that although sars-cov and mers-cov can give us an idea of how sars-cov-2 might behave, using sars-cov and mers-cov to predict the behaviour and spread patterns of sars-cov-2 is not advisable, as these three viruses are different, and sars-cov-2 might not necessarily follow the same patterns as the aforementioned viruses and more studies are needed in this subject to determine how these environmental variables might impact the virus transmission. other factors, such as human mobility patterns and contact rates, should also be taken into consideration as contributing factors to the different transmission rates in different countries (badr et al., 2020) . in developing countries such as brazil and india, other transmission routes (e.g., the contact and droplet routes) may account for the increasing number of cases rather than the airborne route, as these countries are very densely populated, have overcrowded accommodations and lack of access to basic services, j o u r n a l p r e -p r o o f therefore enabling the contact and droplet routes of transmission and spread of the virus. these individual and collective factors such as political, social, economic and cultural conditions should be considered when analyzing the spread of the virus in these countries, as they may play a more significant role than temperature and relative humidity (auler et al., 2020) . specific measures such as quarantines and lockdowns can also affect the incidence of the virus, as different countries have different approaches and mitigation strategies to deal with the pandemic. among the reviewed literature, only a few papers explored viral viability in air samples, which is probably due to the difficulty and limitation of many research groups regarding bsl-3 facilities. nonetheless, efforts should be directed towards the development of novel or adapted analytical methods to reliably and systematically determine the infectivity of sars-cov-2 viral particles as this would enable not only routine fundamental insights into the effective spread of the virus and its societal impact, as well as enabling effective biosensing strategies for on-site determination of viral infectivity as previously mentioned. currently, there is still debate about whether or not sars-cov-2 is transmitted through aerosols produced by infected people during talking, singing sneezing, coughing and breathing, and further studies regarding this route of transmission are needed in order to explore the feasibility of a new personal bioaerosol sampler for monitoring of viable airborne sars virus. pc4 facility with hepa filters installed in the pipeline connecting sampler and vacuum pump to prevent the equipment contamination. contaminated air was bubbled through porous medium submerged into liquid and subsequently split into multitude of very small bubbles. the particles are scavenged by these bubbles, and, thus, effectively removed. natural decay of the virus in the collection fluid was around 0.75 and 1.76 log during 2 and 4h of continuous operation, respectively. a much higher decay rate (2.58 log) was observed for the bubbling through viral suspension in sterile water. yes. the device filled with virus maintenance fluid was capable of providing a relatively low level of microbial decay and can be evaluated for monitoring of such microorganisms in the air. w. xiao et al., (2004) sars-cov-1 to assess the risk of aerosol transmission in sars patients admitted to a hospital through testing the air samples. air samples were collected from 7 wards and 1 balcony of the hospital, 3 times a day for 3 continuous days. the bioaerosol sampler type fa-2 was used. rt-pcr was used to amplify the n protein gene of the sars-cov. the residual solutions were inoculated into prepared cell cultures to isolate live virus. the positive samples were then identified by indirect immunofluorescence assay and sequence analysis of the pcr products. air sampling was performed using a high-resolution slitsampler system and samples were tested for the presence of sars-cov by rt-pcr and cell culture isolation. pcr-positive viruses were collected from wet and dry air samples but results of viability assays of the samples for infectivity in vero-e6 cell culture were negative. no. not specified. kim et al., to study the possible contribution of contaminated hospital air and surfaces to mers transmission. a suspension containing virus was prepared and aerosolized aerosolised to the experimental aerosol chamber by a 3-jet collison nebulizer nebuliser at the flow rate of 6 l/min of hepafiltered compressed air over 2 mins time. then the nebulizer nebuliser was switched off. the experiments were performed for two sets of parameters of the air. on completion of sampling at each time interval, the bioaerosol samplers were disconnected and aliquots of collecting liquid were acquired and analyzed analysed by end-point titration in vero e6 cells. to evaluate the stability of sars-cov-2 and sars-cov-1 in aerosols and on various 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outbreak in hong kong association between ambient temperature and covid-19 infection in 122 cities from china dynamics of airborne influenza a viruses indoors and dependence on humidity on airborne transmission and control of sars-cov-2 zoonotic origins of human coronaviruses an j o u r n a l p r e -p r o o f journal pre-proof efficient virus aerosol sampler enabled by adiabatic expansion evidence of airborne transmission of the severe acute respiratory syndrome virus temporal-spatial analysis of severe acute respiratory syndrome among hospital inpatients role of two-way airflow owing to temperature difference in severe acute respiratory syndrome transmission: revisiting the largest nosocomial severe acute respiratory syndrome outbreak in hong kong investigating sars-cov-2 surface and air contamination in an acute healthcare setting during the peak of the covid-19 pandemic in london figure 1 key: cord-298990-bjv6xnqp authors: zhang, minsi; song, yu; cai, xuhui title: a health-based assessment of particulate air pollution in urban areas of beijing in 2000–2004 date: 2007-04-15 journal: sci total environ doi: 10.1016/j.scitotenv.2007.01.085 sha: doc_id: 298990 cord_uid: bjv6xnqp particulate air pollution is a serious problem in beijing. the annual concentration of particulate matter with aerodynamic diameter less than 10 μm (pm(10)), ranging from 141 to 166 μg m(− 3) in 2000–2004, could be very harmful to human health. in this paper, we presented the mortality and morbidity effects of pm(10) pollution based on statistical data and the epidemiological exposure–response function. the economic costs to health during the 5 years were estimated to lie between us$1670 and $3655 million annually, accounting for about 6.55% of beijing's gross domestic product each year. the total costs were apportioned into two parts caused by: the local emissions and long-range transported pollution. the contribution from local emissions dominated the total costs, accounting on average for 3.60% of gdp. however, the contributions from transported pollution cannot be neglected, and the relative percentage to the total costs from the other regions could account for about 45%. an energy policy and effective measures should be proposed to reduce particulate matter, especially pm(2.5) pollution in beijing to protect public health. the beijing government also needs to cooperate with the other local governments to reduce high background level of particulate air pollution. it is well known that air pollution can harm human health. worldwide, there are more than 2.7 million deaths due to air pollution (world health organization (who), 2003). among air pollutants, particulate matter (pm) has been found to be the most damaging to human health (usaepa, 1997 (usaepa, , 1999 . many epidemiological studies in the past 20 years have revealed that the pm pollution, especially the fine particles (pm 2.5 , particulate matter with an aerodynamic diameter less than 2.5 μm) are associated with higher rates of mortality and morbidity under long-or short-term exposure (morgan et al., 2003; pope et al., 1995a pope et al., ,b, 2002 pope et al., , 2004 schwartz et al., 1996; xu et al., 1995a,b) . the rapid urbanization experienced in china since the 1980s has been accompanied by increasingly poor air quality. according to the world bank, 16 of the world's 20 most polluted cities are in china (economist, 2004) . urban air pollution has become a barrier to sustainable development. beijing, as a megacity (with a population of ≥ 10 million; gurjar and lelieveld, 2005) and the capital of china, has a very serious air pollution problem. the concentration of particles with aerodynamic diameters less than 10 μm (pm 10 ) monitored by the beijing environmental protection bureau (bjepb) science of the total environment 376 (2007) 100 -108 www.elsevier.com/locate/scitotenv from 2000 to 2004 indicated that particulate matter was a major problem in beijing (bjepb, 2000 (bjepb, -2004 . during these years, the annual pm 10 concentrations ranged between 141 and 166 μg m − 3 and were nearly three times the grade 1 national standard, i.e., 50 μg m − 3 . epidemiological research using time series methods has shown the relationship between ambient pm concentrations and human health in beijing (dong et al., 1995; chang et al., 2003a,b) and has quantified the daily mortality and morbidity relative to pm concentrations. with the 2008 olympic games approaching, the air quality in beijing must be improved to project a positive image of the city to the world. while toxicological studies can determine how pm impacts the human respiratory system, economic assessments are also required for the public and the policy makers. relevant research has been carried out in some cities and countries around the world (beirut, lebanon: el-fadel and massoud, 2000; singapore: quah and boon, 2003; shanghai, china: kan and chen, 2004) , indicating that the total economic cost of pm accounted for 4.31% and 1.03% of the gross domestic product (gdp) of singapore and shanghai, respectively. the present study evaluated the health impacts of pm 10 pollution in beijing from 2000 to 2004 and estimated the economic costs. the results should provide a useful reference for pollution control policies. monitoring stations often measure several air pollutants, e.g. pm 10 , so 2 , no 2 , co, o 3 . the variation in ambient concentrations of these pollutants may be dominated by atmospheric diffusion, so that levels of the different pollutants are correlated. to avoid overestimating health effects, künzli et al. (2000) derived estimates from a single indicator pollutant. although fine particle (pm 2.5 ) pollution has a stronger association with adverse human health effects, it has not been measured in china. researchers (quah and boon, 2003; kan and chen, 2004 ) therefore used pm 10 as an indicator. the annual pm 10 concentrations for [2000] [2001] [2002] [2003] [2004] in beijing were reported in the bjepb annual reports (table 1) , the data were averaged over seven urban substations. consequently, the domain of the health effects being studied in the present study is the urban areas of beijing. the high annual concentrations could have originated from several emission sources. the population of beijing, both total and urban, continues to increase (table 1; bmbs, 2005) . coal remains a major energy source in beijing; in 2003 nearly 27 million tons of coal provided more than 50% of the total energy consumption (bjepb, 2003) . the capital steel corporation, located west of urban beijing, has the capacity to produce 6 million tons of steel each year. sand storms frequently affect beijing in the spring. road dust is resuspended by shearing force as well as by the turbulent wakes of vehicles (song et al., 2006) . the health effects of pm 10 include mortality, especially from cardiovascular and respiratory problems, and morbidity, e.g., acute and chronic bronchitis and asthma attacks, accompanied by outpatient visits to internal medicine and pediatrics and hospital admission (pope et al., 1995a) . data were obtained from the yearbooks of the beijing municipal bureau of public health (bmbph) for 2000-2004; incidence rates are listed in table 2 . the health endpoints were excluded if they were not available or difficult to assess, e.g., lung function changes or restricted activity days. exposure-response functions are used in epidemiologic studies to link air pollution and its adverse health effects. such exposure-response functions often include various forms, such as exponential form (kan and chen, 2004) and linear form (quah and boon, 2003; seethaler et al., 2003; wang and mauzerall, 2006) . the cox's proportional hazard model was often selected to determine the effect of air pollution on morbidity and mortality rates after adjusting for other factors such as cigarette smoking, education level, body mass index, occupational exposure to dust or fumes, as well as age and sex of the subjects. however, some study showed the increase of adverse health effects in the lower range of air pollution was rapid than that in the higher range of air pollution (e.g., xu et al., 1995a) . they were at variance with exponential exposure-response function. thus, the linear function is selected in this study. the adverse health efforts of air pollution were calculated as: where β is the exposure-response coefficient, c and c 0 are the ambient and threshold pollutant concentrations and e and e 0 are the health effects at c and c 0 , respectively. the δe or the health damage caused by increased pollution can be calculated if β, c, c 0 , and e are known. the β values for short-time mortality and morbidity in this study are listed in table 3 , they were selected as follows: data from epidemiologic studies in beijing were compared with data from the studies in china in general; if the data from these two groups of studies differed, the meta-analysis results were used. aunan and pan (2004) provided exposure-response coefficients for china according to a meta-analysis, based on the review of the exposure-response function for health effects and pm pollution. the results were very close to those used in kan and chen (2004) , as both cited literatures were almost same. for long-time mortality, we acknowledge that the cohort studies were absent in china and the pm pollution level is much higher than that in western countries. the meta-analysis results from short-time studies in asia (almost from china and korea) for pm 10 pollution on all-case mortality were similar with the studies in american and europe (see table 20 in hei, 2004) . the relative risks could be transferred. aunan and pan (2004) also suggested that the estimates from us cohort studies may be used in china and the results be likely to be on the high side. therefore, the results for long-time mortality from cohort studies from dockery et al. (1993) and pope et al. (1995b) were used in this study. the threshold concentration, c 0 , considered the "reference concentration", is an important and sensitive parameter in the determination of the health effects of pollution. who's guideline on environmental impact assessment (who, 2000) recommended such values could be an ambient concentration of zero, some nonzero "clean" concentration, or a concentration mandated by an air quality standard. ezzati et al. (2002) used a background value, 15 μg m − 3 . quah and boon (2003) (2002) note: except data from bmbph, other data cited from epidemiological papers were same in the 5 years, because we could not find precise research data annually. used the minimum monthly pm 10 concentration, 24.7 μg m − 3 . kan and chen (2004) used an average value from a background site, 73.2 μg m − 3 for shanghai research. however, morgan et al. (2003) showed that even the levels of particulate air pollution in sydney were relatively low, e.g., the pm 10 concentrations ranged only in 16-26 μg m − 3 , it was still found the pm pollution were consistently associated with both daily mortality and hospital admissions, which indicated no threshold concentrations for health effects were present. who has concluded that there is no zero-effect threshold for particulates and the health risks are present at any level of exposure (who, 1999) . therefore, we selected zero as the threshold concentration. although there are ethical arguments against placing a value on human life, the value of a statistical life (vosl) concept was adopted to assess the health effects of pm pollution. vosl is the value of a small change in the risk associated with the dying of an unnamed member of a large group. it represents an individual's willingness to pay (wtp) for a marginal reduction in the risk of dying. for the valuation of reduced morbidity, besides wtp, the cost of illness (coi) approach could also be used. coi measures the total cost of illness that is imposed on a society (quah and boon, 2003) . because a survey of the economic cost of mortality and morbidity from air pollution was not available for china, the benefit transfer approach (bta) was required. it uses the values of environmental loss of a project to estimate the values of a similar project, assuming that the latter project will have a similar impact (quah and boon, 2003; kan and chen, 2004) . most vosl estimates are for the united states, but results have also been reported for lebanon and mexico (el-fadel and massoud, 2000; lopez et al., 2005) . in their shanghai research, kan and chen (2004) used wtp results for mortality in chongqing, china, and usaepa morbidity results. we used data from a contingent valuation study (cvm) conducted in chongqing (wang et al., 2001) , where the vosl of a local resident was about us$34,750 and could increase by us$14,550 with an annual income increase of us$145.8. based on the chongqing resident income data from 1998 (chongqing municipal bureau of statistics, 1999 , we computed the vosl in chongqing in 2000 to be about $44309. the adjustment considered the difference between the annual income in chongqing and beijing, while the estimation of vosl in beijing was transferred on the marginal wtp and income. referencing the chongqing research, the vosl in beijing could be calculated as follows: where vosl bj and vosl cq are the vosl of beijing and chongqing, respectively, i bj and i cq are the personal income of beijing and chongqing, respectively, and e is the elastic coefficient of wtp and is assumed to be 1.0. the shanghai study results and the income difference between beijing and shanghai were consulted to get health endpoint values for bronchitis and asthma in beijing. for respiratory and cardiovascular hospital admissions and outpatient visits to internal medicine and pediatrics, the coi was used for estimates. the health impact value was equal to the sum of hospital admission costs, fees for service, and lost wages during days spent in hospital. because of a lack of hospital admissions expense data for beijing, we used data from the china statistical yearbook of public health (china ministry of health, 2003 and considered the average expense for the same kind of disease as the expenses of respiratory and cardiovascular hospital admissions. the uncertainties were considered both in exposureresponse functions and the economic valuation. the monte carlo method was used to estimate the uncertainties (mean and 95% ci). the calculations were performed by the fortran programme. even though the problem was serious every year, pm pollution levels can be divided into two categories. the first 3 years, from 2000 to 2002, were more polluted, with concentrations of 162-166 μg m − 3 . the next 2 years, 2003-2004, were a little better with concentrations of 141 and 149 μg m − 3 respectively. we should acknowledge that chronic effects of long-term exposure that take years to develop cannot be fully quantified in such studies. there is no evidence that all health effects, for example, pollution exposure in 2003, will be experienced in the same year. however if this were the case, the estimated health effects, e.g., the annual numbers of mortality and morbidity due to pm 10 pollution in the urban areas are listed in table 4 . briefly, the status of pm pollution could be divided into two stages, even though the problem was serious in 2003, both the pm 10 concentration (141 μg m − 3 ) and the attributable number of cases were relatively lower among the 5 years, with the exception that the number of outpatient visits to internal medicine was somewhat high (374562) because of the outbreak of severe acute respiratory syndrome (sars) in spring of 2003. the concentration in 2004 (149 μg m − 3 ) was close to that in 2003, but the estimated number of deaths due to pm pollution was higher (23,733) because of increased population (9.431 million) in the area. table 5 gives the unit values for various health endpoints in beijing. according to only one survey study of chong qing in china, the vosl values in our study are much lower than the us values. the valuation parameters differ by year due to different economic development level, income level, law system etc. using the estimated data in tables 4 and 5, the economic cost of health impacts of pm pollution in beijing from 2000 to 2004 was obtained (table 6) ; the annual figures for 2000-2004 were about 1669.7, 2122.5, 2797.3, 2977.0, and us$3655.5 million, respectively. gdp is a common indicator that reflects the overall economic situation, the economic burden of disease that the public have to endure cannot be expressed in the macroeconomic method (wan et al., 2005) . however, in order to let the public have impression on the quantitative assessment of their public welfare loss, we still compare the economic valuations with beijing's annual gdp. the economic valuations accounted for 5.58, 6.17, 7.21, 6.73, and 7.06% of the annual beijing gdp for the 5 years from 2000 to 2004, and were comparable to results for shijiazhuang (4.3%; peng et al., 2002) and singapore (4.31%; quah and boon, 2003) , and higher than the shanghai valuation (1.03%; kan and chen, 2004 ). in the shanghai study, a background site annual average was treated as the reference concentration, as high as 73.2 μg m − 3 , which could contain pollution transported from the urban area of shanghai and the other districts, such as jiangsu province. hence, the estimated cost due to air pollution was lower than that in this study. while beijing's gdp maintained fast growth at 14.0, 14.8, 12.9, 14.0, and 16.9% from 2000 to 2004, respectively, the economic cost of air pollution could not be neglected. the air pollution costs as a percentage of gdp were lowest in 2000 and highest in 2002. among all the health impact endpoints, premature death played a dominant role in total costs. chronic bronchitis also made an important contribution. moreover, the cost of cardiovascular hospital admission was correspondingly high, while asthma attack contributed the least. 525 (153,278, 272,345) 195,594 (132,223, 244,199) 205,354 (138,759, 255,932) as mentioned above, the annual pm 10 concentrations include two parts: one is caused by local emission in beijing, and one is long-range transported from other cities. the annual background pm 10 concentration in beijing was found at 70 μg m − 3 (ministry of science and technology, 2002), it is calculated by deducting the effects of the downtown from the measurements in a background site, ming tombs, where fewer people live and far away from the city center. such background concentration could be treated as that principally caused by the human activity from other distant cities. in other words, the annual pm 10 concentration contributed by the local emissions in beijing was 92, 95, 96, 71 and 79 μg m − 3 in 2000-2004. the total costs due to air pollution are apportioned into such two parts: local pollution and long-range transported pollution. they were listed in table 7 . the cost contributions from local emission were dominant in the total costs in the 5 years. however, the contributions from the other regions cannot be neglected, as the background concentration (2003) (2004) (2005) acute bronchitis 6 (2.3, 9.8) 6 (1.9, 10.2) 7 (2.5, 11.5) 7 (2.0, 12.1) 8 (2.4, 13.7) wtp kan and chen (2004 ), cmh (2003 asthma attacks 4 (1.6, 6.4) 4 (1.3, 6.7) 5 (2.1, 7.9) 5 (1.8, 8.2) 6 (2.4, 9.6) wtp kan and chen (2004 ), cmh (2003 note: for admission and outpatient visit, the available data did not provide the distribution of the values. was still high of 70 μg m − 3 . to reduce the costs by air pollution in beijing, both the local and distant emissions should be well controlled. we should acknowledge that the air pollution from beijing could be transported to other districts in china, which should lead to the increases of mortality and mobility there. moreover, only the health endpoints that could be quantitatively valued were selected in this study. some health endpoints, such as lung function changes, pain and suffering, and restricted activity days, which are known to be associated with pm pollution, were not included, as these data were not available or difficult to assess; in addition, while the outbreak of influenza and sars could have been included in the raw data we collected, this would have led to the overestimation of health damages. we should also point out that the results in this study could probably be overestimated on some other important reasons. the soil dust (including the primary and resuspended dusts) could accounted for nearly 50% of pm 10 concentrations in the northern cities of china (bi et al., 2007) , however, the recent studies mar et al., 2006) found that soil dusts in particulate matter were not associated with daily mortality. particulate air pollution is a serious health problem in beijing. using statistical data for beijing from 2000 to 2004 and the exposure-response function, we quantified the health impact of pm pollution. the economic cost was high, accounting for about 6.55% of beijing's gdp on average, while the gdp maintained a fast growth rate of about 14%. the costs from local emissions dominated the total costs, but the long-range transported pollution from the other districts also had a relative high contribution to the health costs in beijing. however, we should point that pm 2.5 pollution was more associated with premature mortality than pm 10 in the epidemiological studies. the validity in this study depends on the extrapolating the observed effects of pm 2.5 to pm 10 . moreover, the present measurements showed annual pm 2.5 concentration in beijing could account for 60% of the pm 10 concentrations in beijing (he et al., 2001) , which is much higher than that in western countries (dockery et al., 1993; morgan et al., 2003) . thus, the long-time series measurements and epidemiological related pm 2.5 study should be performed in beijing in the future. at present, policy to reduce air pollution, especially the pm 2.5 pollution is needed urgently and effective measures should be carried out as soon as possible. the emissions from combustion sources, such as coal burning and oil burning, and the secondary products from photochemical reactions contributed mostly in pm 2.5 in beijing (song et al., 2006) . coal is still a dominant energy source in beijing, especially in industry for electricity generation (egu). it could be an effective way to use the advanced coal gasification technologies in the coal-fired egu. raw coal used in industrial plants could be replaced by cleaner energy sources, such as natural gas or electric power. a remarkable problem is that the number of motor vehicles is increasing rapid from 1.5 million in 2000 to 2.4 million in 2004. conversely, the bicycle use is declining. beijing government should preserve or restore bicycle lanes and provide free parking facilities to encourage the bicycle use. on the other hand, both the control technologies on tailpipe emission and gasoline quality should be improved in motor vehicles. reduction of gaseous pollutants, volatile organic compounds and nitrogen oxides from tailpipe exhaust and sulfur dioxide from coal burning could alleviate the fine particles pollution transferred through photochemical reactions. as some toxic organics, such as black carbon could be still abundant in the fine part of road dust in beijing (song et al., 2006) , the bare soil surfaces should be grassed or wooded. however, china is a developing country with a rapid economy increase; we acknowledge the large gap between the air pollution level in china and in western countries. to control the high background level needs the collaboration with other local governments. it is not an easy way to catch up the level in other developed countries. this study was based on the assumption that the entire population, across urban areas of beijing, was exposed to the average concentration levels, as recorded at the seven urban air quality monitoring stations. this was a rough estimate. we suggest using atmospheric diffusion models (e.g. isc3, calpuff, and model3-cmaq) to obtain concentrations at finer spatial resolutions. more surveys are needed to determine the appropriate economic cost of adverse health effects from pm pollution. exposure-response functions for health effects of ambient air pollution applicable for china -a meta-analysis beijing health yearbook. beijing: beijing science and technology press beijing: china statistics press source apportionment of pm 10 in six cities of northern china time-series analysis on the relationship between air pollution and daily mortality in beijing study on the associations between ambient air pollutant and hospital outpatient visit or emergency room visit in beijing 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particulate air pollution cardiovascular mortality and long-term exposure to particulate air pollution, epidemiological evidence of general pathophysiological pathways of disease the economic cost of particulate air pollution on health in singapore is daily mortality associated specifically with fine particles? economic costs of air pollution related health impactsan impact assessment project of austria, france and switzerland source apportionment of pm 2.5 in beijing by positive matrix factorization the final report to congress on benefits and costs of the clean air act the final report to congress on benefits and costs of the clean air act considerations in applying the general equilibrium approach to environmental health assessment willingness to pay for reducing the risk of death by improving air quality: a contingent valuation study in chongqing, china, presented at the third international health economic association conference in a survey on acute respiratory disease evaluating impacts of air pollution in china on public health: implications for future air pollution and energy policies relation analysis of air pollution and children's respiratory system disease prevalence a tale of two cities: effects of air pollution on hospital admissions in hong kong and london compared air quality guidelines. geneva: world health organization quantification of the health effects of exposure to air pollution world health organization (who) association of air pollution with hospital outpatient visits in beijing air pollution and unscheduled hospital outpatient and emergency room visits we would like to thank the anonymous reviewers for their valuable comments, which greatly improved the quality of the manuscript. key: cord-287751-52e0tlcu authors: dai, qili; ding, jing; song, congbo; liu, baoshuang; bi, xiaohui; wu, jianhui; zhang, yufen; feng, yinchang; hopke, philip k. title: changes in source contributions to particle number concentrations after the covid-19 outbreak: insights from a dispersion normalized pmf date: 2020-11-06 journal: sci total environ doi: 10.1016/j.scitotenv.2020.143548 sha: doc_id: 287751 cord_uid: 52e0tlcu factor analysis models use the covariance of measured variables to identify and apportion sources. these models, particularly positive matrix factorization (pmf), have been extensively used for analyzing particle number concentrations (pncs) datasets. however, the variation of observed pncs and particle size distribution are driven by both the source emission rates and atmospheric dispersion as well as chemical and physical transformation processes. this variation in the observation data caused by meteorologically induced dilution reduces the ability to obtain accurate source apportionment results. to reduce the influence of dilution on quantitative source estimates, a methodology for improving the accuracy of source apportionment results by incorporating a measure of dispersion, the ventilation coefficient, into the pmf analysis (called dispersion normalized pmf, dn-pmf) was applied to a pnc dataset measured from a field campaign that includes the spring festival event and the start of the covid-19 lockdown in tianjin, china. the data also included pollutant gases and hourly pm2.5 compositional data. eight factors were resolved and interpreted as municipal incinerator, traffic nucleation, secondary inorganic aerosol (sia), traffic emission, photonucleation, coal combustion, residential heating and festival emission. the dn-pmf enhanced the diel patterns of photonucleation and the two traffic factors by enlarging the differences between daytime peak values and nighttime concentrations. the municipal incinerator plant, traffic emissions, and coal combustion have cleaner and more clearly defined directionalities after dispersion normalization. thus, dispersion normalized pmf is capable of enhancing the source emission patterns. after the covid-19 lockdown began, pnc of traffic nucleation and traffic emission decreased by 41% and 44%, respectively, while photonucleation produced more particles likely due to the reduction in the condensation sink. the significant changes in source emissions indicate a substantially reduced traffic volume after the implement of lockdown measures. positive associations between ambient particulate matter (pm) pollution and subsequent detrimental health outcomes have been well documented in many epidemiologic studies (song et al., 2017; yin et al., 2019) . given the severe fine pm (pm 2.5 , with aerodynamic diameter less than 2.5 µm) pollution in china, pm 2.5 was ranked as the first leading mortality risk factor in 2015 (cohen et al., 2018) . compared with larger sized particles with higher mass concentrations, smaller particles have lower mass concentrations but higher particle number concentrations (pncs) and larger surface areas that are more likely resulting in increased adverse health effects (meng et al., 2013; yin et al., 2019) . a recent time-series analysis in northern china (shenyang) reported that short-term exposure to increased pncs for particles with size less than 0.5 µm were significantly associated with total and cardiovascular mortality (meng et al., 2013) . they found that these associations between mortality and pncs tended to be independent of particle mass concentrations and simultaneous exposures to gaseous pollutants. previous studies also highlighted that the limited availability of size-resolved pnc measurements prevented obtaining adequate epidemiologic evidence regarding associations with pncs (ibald-mulli et al., globally (isaifan, 2020; venter et al., 2020) . for example, air quality in china has improved with the reduction of non-essential industrial and motor vehicle usage as reported by liu et al. (2020) , who has investigated the spatial and temporal characteristics of nighttime light radiance and air quality index values before and during the pandemic in mainland china. the covid-19 outbreak provides an opportunity to evaluate the public health benefits of air quality improvement. a recent study found that covid-19 forced-industrial and anthropogenic activities lockdown are likely have saved more lives by preventing ambient air pollution than by preventing infection . their cross-sectional study conducted in the united states indicated that an increase of only 1 μg m -3 in pm 2.5 was associated with an 8% increase in the covid-19 death rate. thus, an emphasis is needed on the importance of continuing to enforce existing air pollution regulations to protect human health both during and after the covid-19 crisis. the environmental impact of the pandemic is of particular interest to governments and the public since it is crucial for developing post-pandemic pollution control strategies. however, there are no reports to date on changes in source contributions to health risk relevant pncs during the outbreak of covid-19. to identify particle sources and calculate their contributions, source apportionment studies have been conducted to support control strategies that can further reduce the health burden of pm. positive matrix factorization (pmf) has been widely applied to 6 et al., 2011; lorelei de jesus et al., 2020) . dilution is recognized as a crucial process that induces other processes to alter the particle number and size distributions (gidhagen et al., 2005; jacobson and seinfeld, 2004; ketzel and berkowicz, 2004) . kumar et al. (2011) reviewed the dynamics and dispersion modelling of nanoparticles from road traffic in the urban atmospheric environment and concluded that dilution is the most important process that needed to be considered with highest priority in dispersion models irrespective of any spatial scales. freshly emitted particles and new particles formed via nucleation process are diluted in the air and undergone transformation processes. the conventional use of pmf to apportion pncs is to extract size distribution profile from observed particle size distributional data on the basis of the internal covariance of particles from different detected sizes. due to the variation in dispersion, some of the information content in the observation data will be certainly lost. to investigate the changes in source contributions to pncs after the outbreak of covid-19, a newly proposed dispersion normalized pmf (dn-pmf) that incorporated the ventilation coefficient (vc) into the pmf analysis aimed of reducing meteorological influence on the analysis was applied to a pncs dataset measured from january 15, 2020 to february 13, 2020, included the start of the covid-19 lockdown in tianjin, china. the database also included pollutant gases and hourly pm 2.5 speciated composition data. suburban site surrounded by several universities, and distant from major highways and high traffic zones. a suite of instruments was operated in the supersite building with sampling inlets on the roof terrace. particle number concentrations with sizes ranging from 7.2 nm to 778 nm were measured using a universal scanning mobility particle sizer spectrometer (u-smps) (palas, germany). other air pollutants, including pm 1 and pm 2.5 , sulfur dioxide (so 2 ), nitrogen oxides (no 2 ), carbon monoxide (co) and ozone (o 3 ) were also recorded hourly. organic carbon (oc) and element carbon (ec) were measured hourly using a semicontinuous thermal-optical carbon analyzer (focused photonics inc., china) and water-soluble ions (so 4 where is dispersion normalized concentrations, is the concentration observed during period i, and is the average value of vc over the entire measurement campaign. in this case, is 582 m 2 s -1 . the concentrations and uncertainties of pnc dataset were normalized on a sample by sample basis. the dispersion normalized concentrations and uncertainties were used as the input matrix to the pmf analysis. us epa pmf 5.0 was used for pmf analyses. details of pmf are available elsewhere (hopke, 2016; paatero, 1999) . in addition to measured pnc data, auxiliary variables include gaseous pollutants (so 2 , no 2 , co and o 3 ), pm 1 , pm 1-2.5 (pm 2.5 -pm 1 ), radiation and selected potential source tracer species (oc, ec, no 3 -analyses to support factor interpretation. adding additional variables increases the numbers of edge points and thereby reduce rotational ambiguity (emami and hopke, 2017) . all missing data values were replaced by the median value for the given size bin or species and the uncertainty was set to three times that value. measurement errors for pnc were estimated as follows (ogulei et al., 2006b; squizzato et al., 2019) : where is the estimated measurement error for size bin j of i th sample, nij is the measured concentration for size bin j of i th sample, ̅ is the arithmetic mean of the measured concentration for size bin j. was commonly used as a constant throughout all size bins and pollutants ( =0.01). given that the lowest and highest bins of pnc were reported with elevated measurement error (liu et al., 2014; wiedensohler et al., 2018) , we set higher uncertainties to these size bins. the first two lowest size bins and highest size bins were assigned with a multiplier of , and the second two lowest size bins and highest size bins were assigned with multiplier of . for subsequent lower and higher size bins, the multiplier was set with a decrement of 0.5 until it approaches unit. the overall uncertainty matrix was computed as (ogulei et al., 2006a) : where was estimated from eq. 3 and is a constant. c 3 values from 0.01 to 0.5 were tested. a value of 0.1 was assigned to c 3 for all size bins and 0.15 to so 2 , no 2 , co, o 3 , pm 1 , pm 1-2.5 and radiation, while c 3 was set as 0.2 for the total pnc to obtain an optimal solution in mathematical sense. for selected chemical species, these species concentrations below method detection limit (mdl) values were replaced by j o u r n a l p r e -p r o o f journal pre-proof half of the mdl value. the corresponding uncertainties of these values were set at five sixths of the mdl values (polissar et al., 1998) . missing chemical species values were estimated by linearly interpolating the closet non-missing values and the corresponding uncertainties were increased by a factor of 3. all auxiliary variables were assigned as "weak" and the total pnc was set as the "total variable" with uncertainty tripled. the f-value for total pnc was used to normalize the size bin data and factor contributions. the f-value for pm 2.5 was used to normalize the chemical the time series of pnc, pm 1 mass concentration and vc values are shown in fig. 1 . the hourly average total pnc from 7.2 to 778 nm over the measurement campaign was 14397 ±5695 pt cm -3 , ranged from 5490 to 48372 pt cm -3 . the average mass concentration of pm 1 was 52.2 ± 42.6 µg m -3 , ranged from 1.0 to 224.1 µg m -3 . in solutions using pmf with four to nine factors were explored for the original data and dispersion normalized data. the best solution with the optimal number of factors was evaluated with selection criteria of appropriately narrow distributions of scaled residuals of pncs and the physical interpretability of factors in terms of (a) examination of size factor profiles and its association with external variables, (b) source directionality from cbpf plots, and (c) diel patterns. eight-factor models were finally selected as the best solutions for both the s4 and 3, respectively. the factors are interpreted and discussed individually in the following section. this factor presented three major size modes: a nucleation mode peaked at ~8-20 nm, a small sized mode peaked around 30-50 nm and an accumulation mode peaked at 100-200 nm (fig. 3 ). on-line measurements of the size distribution of particles in flue j o u r n a l p r e -p r o o f and stack gas of a municipal waste incineration plant in europe showed a bimodal size distribution with peak mode at 90-140 nm and a smaller mode at approximately 40 nm (maguhn et al., 2003) . it was also found that particles tend to growth by absorption and coagulation after the boiler. the chemical species profile had high contributions of cr and cu with narrow disp intervals (fig. 3) , which are tracers of municipal waste incineration. lu et al. (2018) reported abundant cr in bottom ash from plastic materials incineration. the cbpf plot of incinerator also shows a very clear nw wind direction pointing to the municipal incineration plant. thus, this factor was assigned to municipal incinerator. on average, municipal incinerator had the lowest contribution to total pnc during the campaign (3.2%, fig. s5 ). traffic has been recognized as one of the major sources of pnc. two traffic factors were identified as traffic nucleation and traffic emission with particle major size modes about 10-30 nm and 30-150 nm, respectively. as been previously reported in literature (morawska et al., 2008; vu et al., 2015) , diel pattern of the traffic nucleation factor has a sharp morning rush hour peak (6:00-8:00 am) and had enhanced contributions more broadly distributed beginning in the afternoon. while the traffic emission factor showed a strong peak in the morning after the rush hour (8:00-10:00 am) and a minor peak in the evening rush hour. both traffic factors had high concentrations of no 2 and explained 5-10% of the ec variation, indicating its traffic exhaust nature including diesel emissions . the presence of some o 3 and radiation in the traffic emission factor, suggests that particles exhaust from vehicle emitted in the morning were possibly subjected to photochemistry processes. the cbpf plot of traffic nucleation indicates its directionality corresponded to the roads located ~1.5 km and 3.0 km southwest of the measurement site (fig. s1 ). the traffic emission factor has a stronger association with southeasterly winds and a predominant occurrence for wind speeds between 3-5 m s -1 . there are two major highways situated ~18 km east of the measurement site and a highway extending to the southeast. both traffic factors are heavily affected by local traffic emissions. the sia (ammonium nitrate and sulfate) had three modes in the particle number size profiles with the major size mode between 180-600 nm, an aitken mode and an ultrafine mode size ranges, which is similar with the observations such as in rochester, ny (squizzato et al., 2019) . the explained variations of particles in the accumulated mode increased with increasing size. the presence of high nitrate, sulfate and ammonium in the species profile support its assignment as secondary inorganic material. the wide particle size range of sia factor suggests that it originated from both gas-to-particle conversion of local no x and regional transportation of sulfate. some ec present in the species factor may be caused by the condensation of secondary material on freshly emitted ec particles. the morning peak of sia at 9:00-10:00 am likely resulted from downmixing of transported secondary particles from aloft after the breakup of overnight inversions. the broad afternoon minimum was likely due to the mixing layer height dynamics. the cbpf plot of sia shows higher probability values with moderate speed winds (~2 m s -1 ) come from downtown tianjin (nw) more than other directions, highlighting the regional transport nature of sia during heavy particulate pollution episodes. it was the largest contributor to pm mass concentration but accounted for only 6.2% of total pnc over the measurement campaign. in addition to new particle formation from traffic emission with a dominant particle size ranged from ~10-30 nm as typically observed during rush hour as discussed above, a factor with particle size peaking in the nucleation mode size range (<20 nm), and characterized by high explained variations of o 3 and solar radiation with narrow disp bands was identified as new particle formation (npf) through photochemistry. it shows a strong sharp increase around midday (12:00) concurrent with the highest solar intensities that drive photochemical processes. photonucleation occurred primarily during clean days with low pm mass concentrations (rivas et al., 2020) . the low pm concentrations result in low condensation sinks and allow for npf to occur (mcmurry and friedlander, 1979) . as suggested by the cbpf plot, this factor is associated primarily with relatively higher wind velocities for east-south-easterly winds and southerly winds. the cbpf plot of photonucleation overlaps with traffic nucleation in south-south-west direction, suggesting air masses from this direction j o u r n a l p r e -p r o o f likely facilitate npf. easterly winds often associated with relatively clean bohai bay air possibly favors the nucleation process because of its low condensation sink. interestingly, the non-local feature of photonucleation tends to indicate that the measurement site is likely well separated from the emission sources. on average, this factor contributed 7.8% of total pnc. coal combustion was reported as an important source of ambient particles with size ranged from nanoparticles to coarse particles, depending upon various factors such as coal type, combustion condition, dilution ratio and residence time, and pollution control device (vu et al., 2015) . the formation of particles emission from coal combustion involved in complex chemistry as it will undergo vaporizationnucleation/condensation-growth processes (carbone et al., 2010) . lipsky et al. (2002) reported a nucleation peak mode around 10 nm in the stack plume of coal combustion. particles tend to shift to large sizes after release into ambient air experiencing dilution, cooling, and condensation/coagulation processes. an experimental measurement of pulverized coal combustion suggested that ultrafine particles exhibited a unimodal distribution under 1500 k with size peak shifting from 10.76 nm to 38.46 nm as time evolved (gao et al., 2017) . there is a paper mill with hot steam supplied by pulverized coal boilers situated ~6.5 km se from the measurement site (fig. s1 ). the cbpf plot presents a clear se direction linking this factor to the paper mill. thus, this factor with particle sizes peaking around 30 nm was attributed to coal combustion. the gaseous and species profiles corroborate the assignment of this factor to coal combustion since it had relatively high concentrations of no 2 , ec, so 4 2and no 3 -, and explained some of the so 2 , co, and as variations. the diel pattern presents a j o u r n a l p r e -p r o o f journal pre-proof middle day peak as the particles can be transported by the afternoon sea breeze from bohai bay. the factor has a size mode ranging from ~50 nm to 300 nm and peaked in the accumulation mode (~120 nm). it was identified as residential heating. its size distribution is similar with particles emission from residential wood pellet boilers (chandrasekaran et al., 2011; wang et al., 2019) . it is associated with some so 2 , no 2 , and co with tight disp bands, and moderate loading of pm mass concentration. the chemical species profile also supports coal as it explained ~15% of cland ~10% oc with small intervals in mass fractions. cl is a common marker of coals in northern china (yu et al., 2013; li et al. 2019 ). the diel pattern for this factor presents a clear morning peak (7:00-8:00 am) during stable atmosphere conditions with low wind speeds. pnc of residential heating during nighttime appears to be higher than that during daytime. the cbpf plot of residential heating factor has an association with all wind directions and low wind speeds (<2 m s -1 ). the festival emission factor is attributed largely on the basis of strong chemical association with oc, ec, no 3 -, so 4 2-locations (joshi et al., 2019; kong et al., 2015; moreno et al., 2010; tian et al., 2014) . these species have relatively narrow disp intervals in the species profiles supporting the inclusion of firework emissions in this factor. oc, ec and sulfate in the profile were also likely emitted from coal/wood burning in large bond fires to celebrate the festival as reported in dai et al. (2020) . fireworks were generally banned in urban areas and tianjin implemented a no-fireworks policy this year. however, people still likely utilize fireworks during these holiday periods. based on the cbpf plot, the origins of these particles were located in residential areas where coal/biomass was burned for heating/cooking during the spring festival. people were required to stay at home after the implement of lockdown measures to prevent the spread of covid-19 and thus, more people were in residential areas throughout the day requiring more heating and cooking than under normal circumstances. fireworks emissions were correlated with residential coal/biomass burning. it should be noted that this factor contributed significantly to pm mass concentration, particularly pm 1 in the period after the start of the spring festival (january 24, 2020). since the dn-pmf reduced the influence of dispersion, the cbpf plots derived from dn-pmf results tend to have better defined directionality than the regular pmf based plots. this measurement campaign included the unusual event of the chinese spring festival (sf) and lockdown measures enforced to prevent the spread of covid-19. unlike the common sources under the "business as usual" scenario prior to january 24, there was a change in the number of sources due to the fireworks displayed during the sf. source emission strengths also changed after the covid-19 outbreak as emergency responses were implemented beginning on january 25 in tianjin. to j o u r n a l p r e -p r o o f to reduce the influence of meteorology on quantitative source estimates, dispersion normalized pmf incorporating data normalized with the ventilation coefficient into pmf analyses, was applied to a pncs dataset measured from a field campaign that includes the spring festival event and the start of the covid-19 outbreak in tianjin, china. in addition to pncs data, other variables include solar radiation, gaseous pollutants, particle mass concentrations and chemical compositional data were measured and included to facilitate the interpretation of factors. the pncs dataset combined with these additional variables were normalized by vc values and then subjected to pmf analysis. eight factors were resolved and labelled as municipal incinerator, traffic nucleation, secondary inorganic aerosol (sia), traffic emissions, photonucleation, coal combustion, residential heating and festival emission. to examine the effects of reducing meteorological influence on estimated source patterns, the diel pattern and source directionality for each source derived from conventional pmf (unnormalized) and dn-pmf were compared. the dn-pmf enhanced the diel patterns of photonucleation and the two traffic factors by sharpening the differences between daytime peak values and nighttime concentrations. after dispersion normalization, pmf yielded better defined directionality of sources. the directionalities of municipal incinerator plant, traffic emission and 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covid-19 lockdowns cause global air pollution declines with implications for public health risk. medrxiv review: particle number size distributions from seven major sources and implications for source apportionment studies emissions from in-use residential wood pellet boilers and potential emissions savings using thermal storage exposure to air pollution and covid-19 mortality in the united states: a nationwide cross-sectional study. medrxiv associations between size-fractionated particle number concentrations and copd mortality in characterization and source apportionment of pm 2.5 in an urban environment in beijing particle size and mixing state of freshly emitted black carbon from different combustion sources in china methodology, writing-original draft preparation jing ding: assisting in sample collection, data curation congbo song: result interpretation, writing -review & editing baoshuang liu: writing -review & editing xiaohui bi: resources, investigation jianhui wu: sample collection and analysis yufen zhang: writing -review & editing yinchang feng: resources result interpretation, writing -review & editing this work was financially supported by the national key r&d program of china key: cord-351665-6gwb900b authors: sarkar, priyanka; debnath, nirmal; reang, demsai title: coupled human-environment system amid covid-19 crisis: a conceptual model to understand the nexus date: 2020-08-18 journal: sci total environ doi: 10.1016/j.scitotenv.2020.141757 sha: doc_id: 351665 cord_uid: 6gwb900b abstract the world today is dealing with a havoc crisis due to the pervasive outbreak of covid-19. as a preventive measure against the pandemic, government authorities worldwide have implemented and adopted strict policy interventions such as lockdown, social distancing, and quarantine, to curtail the disease transmission. consequently, humans have been experiencing several ill impacts, while the natural environment has been reaping the benefits of the interventions. therefore, it is imperative to understand the interlinked relationship between human society and the natural environment amid the current crisis. herein, we performed a meta-analysis of existing literature reporting the various impacts of covid-19 on human society and the natural environment. a conceptual model was developed to portray and address how the interaction of the existing elements of both sub-components of the coupled human-environment system (ches) – human society and natural environment – are impacted by the government interventions. results revealed a suite of positive and negative impacts of covid-19 on both the sub-components. our model provides an explicit impression of the complex nexus of ches amid the current crisis. the proposed conceptual model could help in understanding the complex nexus by identifying the route of short-term impacts of covid-19 measures and thus may aid in identifying priority areas for discussion and planning in similar other crises as well. coupled human-environment system (ches) represents a complex, dynamic, interconnected, and integrated system in which humans and the natural environment interact with each other (turner et al. 2003; liu et al. 2007; galvani et al. 2016) . in recent centuries, humans have been remarkably intervening with the environment to fulfill the demands of the growing population and rapid economic development (myers and patz 2009) . such a plethora of anthropogenic interventions poses long-term repercussions i.e., extreme climatic events and other natural calamities, food, and water scarcity, increased exposure to infectious diseases, population displacement, etc. on the human society (myers and patz 2009; galvani et al. 2016 ). therefore, understanding the complex ches is important for recognizing and addressing the vulnerability of the situation on human society, and natural ecosystems amid any local or global crisis (turner et al. 2003) . the world today is dealing with a havoc crisis due to the pervasive outbreak of coronavirus disease 2019 . the vicious covid-19 is an infectious disease caused by a new 2020), and exhibits a higher human to human transmissibility (chan et al. 2020) . the pandemic has posed a great threat to the global-public health and economic recession and is still ongoing (bogoch et al. 2020; wu et al. 2020) . so far, no proven pharmaceutical treatment has been developed to combat the pandemic (singhal 2020). given its severe impact, the world health organization (who) has declared covid-19 as a public health emergency of international concern on january 30, 2020. as a preventive measure against the pandemic, the government authorities worldwide have implemented and adopted strict policy interventions to maintain social (physical) distancing and curtail the transmission of covid-19. almost one-quarter of the global population is now confined within their homes, experiencing several negative/ill impacts in terms of socioeconomic and psychological well-being. on the contrary, there are several hidden benefits of the interventions on the environment or natural world. therefore, it is imperative to understand and appreciate the mutually-affective relationship between human society and the natural environment amid the current crisis (kumar 2020a ) and identify the priority areas for designing necessary action plans for a balanced state. although, few studies have highlighted the impacts of covid-19 and relevant policy actions on the environment, and social aspects like economic and health consequences (hevia and neumeyer 2020; lin et al. 2020; muhammad et al. 2020; sharma et al. 2020; zambrano-monserrate et al. 2020) , the complexity of ches amid the current crisis has not been well understood. unpredictability and vulnerability of ches require a case or situation-specific assessment to consider appropriate relationships of variables with a set of standardized methods (polsky et al. 2003; turner et al. 2003) . in this regard, our study attempted to understand the processes, responses, and feedbacks within the complex ches amid the crisis through a conceptual model. such models are valuable communication tools that represent the current knowledge of a system and illustrate its complex interactions in a simplified way (gross 2003; imgraben j o u r n a l p r e -p r o o f journal pre-proof et al. 2019) . conceptual models may thus assist in identifying the priority areas that require further research or monitoring and build a basis for discussion and planning (roman and barrett 1999) . the specific objectives of the study were to (i) perform a meta-analysis of existing literature reporting various impacts of covid-19 on human society and the natural environment, and (ii) develop a conceptual model to illustrate and understand the complex nexus of ches amid the pandemic. our conceptual model could be helpful in clearly portraying the complex and coupled nature of the system amid the current crisis. thus, aid in identifying the priority areas and intrigue the discussion for further planning towards mitigating the effects of the current-as well as similar crisis. we performed a systematic review of peer-reviewed scientific articles on the impact of covid-19 on human society and the natural environment worldwide written in english using the isi web of science (wos) -core collection database published until april 30, 2020 (with an open initial date). a literature search was conducted using a combined search string with two topic fields. search strings in the first topic field included different terms denoting covid-19 outbreak, restrictions and their impacts ("covid-19", 'coronavirus', the conceptual model was developed based on the information collected from the literature review, and the previous experience and expertise of the first author on model development -'expert-based models' approach (ferrier et al. 2016 ). this was followed by brainstorming amongst all the authors to improvise the model. during the entire process of model development, authors' practical experiences and in-depth understanding of the context of ecological and environmental studies, and associated socio-economic factors were advantageous. the literature review revealed a suite of impacts (positive and/or negative) of covid-19 and lockdown/restrictions on human society and the natural environment (table 1) on both human society and the environment were also recorded (table 1) . the proposed conceptual model comprises of two modules, (i) drivers of change: covid-19 (direct driver) and lockdown/restrictions (indirect driver), and (ii) our focal point: coupled human-environment system (ches) (fig. 1) . drivers of change refer to the factors that directly or indirectly cause changes in nature and its components, anthropogenic assets, and good quality of life (ipbes, https://ipbes.net/glossary/driver). the conceptual model illustrates how the different elements of two sub-systems: human society and natural environment, interact with one another -directly and/or indirectly, through forming a network of associations. the relationships between the elements of the two sub-systems are depicted by arrows, which also shows the direction of impacts, positive and/or negative ( fig. 1 ). for example, for the sub-system: human society, limited transportation had a positive impact in containing the disease, thus lowering infection & death. similarly, limited transportation due to lockdown resulted in reduced fuel consumption, generating positive impacts on the sub-system: natural environment, characterized by reduced-air pollution (lower conc. of co 2 , co, nox, pm 2.5 , pm 10 ) and environmental noise, leading to flourished biodiversity/wildlife. the conceptual model also displayed two feedbacks -(i) between the primary and secondary drivers -covid-19 and lockdown/restrictions, and, (ii) between covid-19 and the health workers. to illustrate, the spreading of the virus has mandated the implementation of lockdown inducing grief to human society worldwide, which on the other hand, had a positive impact on suppressing the pandemic. covid-19 crisis is considered one of the worst pandemics in history which has further complicated the entire coupled human-environmental system. lower adaptability of human society to various socio-environmental crises arises mainly due to the poor understanding of the complex and interconnected nature of the human-environment system (dearing et al. 2006 ). hence, understanding the complexity of any system is pressing to avoid any environmental ensue on a regional or global scale (roberts et al. 2002) . conceptual models assist in envisioning the complex interactions in a simplified manner and recognize priority areas for the implementation of necessary management strategies. our conceptual model explicitly illustrates the impacts of covid-19 and lockdown/restriction -directly or indirectlyagainst the pandemic on the various elements of the intricate and coupled humanenvironment system and/or the feedbacks amongst them as described below: as depicted in the model, covid-19 has a direct negative impact on human health owing to its high risk of infection and death. the fatal impact of covid-19 on global human health has surpassed the number of infections and deaths caused by its ancestors and is still accelerating (bogoch et al. 2020; chan et al. 2020; lin et al. 2020; wu et al. 2020) . grech (2020) suggested that the pandemic may lead to half a billion deaths i.e., ~ 6% of the global population or more; likely due to the absence of a concrete approved treatment to combat the pandemic (singhal 2020). the pandemic has led to the increased generation of tons of medical/healthcare wastes several folds when compared to before the disease outbreak (adb j o u r n a l p r e -p r o o f journal pre-proof calma 2020; isdm 2020; saddat et al. 2020) . as highlighted in the model, increased generation of medical wastes, in turn, led to unmanageable medical waste triggering other human health risks (alverson 2020; jiangtao and zheng 2020; zambrano-monserrate 2020). for example, health-& sanitation workers, rag pickers, trash cleaners, etc. are at high risk of infection due to close contact with the patients and/or unmarked medical wastes such as discarded masks, gloves, etc. (mallapur 2020; saddat et al. 2020 ). in addition, the model also depicts the existence of feedback between covid-19 and health workers. for instance, while the health workers are at the front line of the pandemic outbreak, their exposure to the virus has put them at the risk of infection and death, coupled with other health risks such as fatigue, occupational burnout, psychological distress, etc. making them vulnerable to the current crisis. as of april 12, 2020, the who reported that the pandemic has already hit over 22,000 health workers across 52 countries (the economies times 2020a). on the contrary, health workers stand as an important potential barrier to minimize the risk of covid-19 infections and death as feedback and contribute largely to the wellbeing of the global public. the pandemic has plunged the entire world into a looming global economic recession (corlett et al. 2020; giles et al. 2020; ozili and arun 2020) . as depicted in the model, the the model depicts a direct negative impact of lockdown on human society in terms of inducing poverty and food insecurity/crisis. however, the impact of lockdown on the poor and wealthy sections of society has been disparate. for instance, while the period of total lockdown has been easier for the rich and middle-class society to pull through with assured incomes, health insurance, adequate spaces at home to maintain physical distancing & running water supplies, daily sustenance of the weaker section of the society has been very miserable. insecure sources of income for billions of the poor people worldwide due to loss of jobs amid lockdown as discussed in section 4.1.2 have severely affected their livelihoods pushing them towards extreme poverty. in addition to the instability of food availability due our model highlights both positive and negative impacts of lockdown due to the limitedtransportation and movement. the model depicts the positive impact of lockdown through limiting movement/transportation, thus ceasing all events -social, political, sports, academic, and other gatherings (breeding grounds of the virus) to maintain social distancing and curtail the disease transmission as mandated by government authorities worldwide (financial express 2020). more than 3.9 billion people or half of the world's population are currently under containment (sandford 2020) . consequently, the lockdown has posed a negative impact on the psychological resilience of people (homes et al. 2020; li et al. 2020; qiu et al. 2020; wang et al. 2020) . however, it is worth mentioning that homestay due to limited movement may likely bring a positive impact in terms of enhancing the family bonding. as shown in the model, paralyzed transportation due to lockdown has negatively impacted the global economic recession. for instance, lockdown against covid-19 has caused the shutdown of national borders in nearly 100 countries which have dropped air travel by 96% j o u r n a l p r e -p r o o f journal pre-proof (wallace 2020) , causing a loss of us$ 113 billion to the air travel industry (appleton 2020). the tourism industry has also come to halt, causing 1% global economic contraction as reported by the un (the statesman 2020). similarly, the lockdown has also hit the railway industry in terms of financial loss as reported by western railways, govt. of india (the economic times 2020). limited transportation has also caused unemployment and job insecurity for people involved in the private transport sector, which would ultimately affect their psychological resilience. . esa also reported the changing density of harmful gases emitted due to fossil fuel burning (child 2020) . in addition, the carbon emissions in china, the epicenter of the covid-19 pandemic, has dropped by ~ 25% over four weeks at the beginning of 2020 (child 2020) . in northern india, the residents now could view the himalayan mountain range due to increased visibility, which otherwise has been concealed by pollution for ~ 30 years (child 2020) . the air quality index (aqi) in delhi and ncr's, india, has reduced to 60, which otherwise scores an aqi of 600 during the smoggy winter months (the economic times 2020). while in venice, italy, restrained tourism industries have improved the water quality of winding canals (child 2020) . moreover, paralyzed transportation has also plummeted environmental noise due to the slowdown of traffic (gibney 2020, schuster 2020). all these factors are likely to contribute to the flourishing and liberation of biodiversity and wildlife. our model also shows an indirect positive impact of improved air quality in containing the disease transmission and death. air pollution is known to have a strong association with a high incidence of various respiratory infections (cipolla et al. 2018; silva et al. 2014; zhang et al. 2020) , and higher mortality rates (lelieveld et al. 2015) . evidence shows high cases of covid-19 in highly polluted areas of china, italy, and the united states, the countries with higher cases (pansini and fornacca 2020) . in addition to the impact of covid-19 in terms of infection and death as discussed in section 4.1, extended lockdown and stay-at-home regulations against the pandemic has associated human health risks such as weight gains due to sedentary lifestyle, psychological/behavioral changes, etc. (lippi et al. 2020) parivaar, govt. of india, https://www.gangaaction.org/actions/issues/solid-waste/). all these activities are very likely to contribute to flourishing biodiversity/wildlife. the shutdown of offices, business centers, industries, and other workplaces due to the pandemic (muhammad et al. 2020, richards and rickard 2020) has both negative and positive impacts on the ches as identified in the model. nickle (2020) suggested that 86% of industry members such as the growers, shippers, retailers have been reported to be affected due to the lockdown. this instigated a high negative impact through a looming global economic recession, leading to unemployment/job insecurity and lower psychological resilience. on the contrary, the model also identifies the positive impact of the shutdown of workplaces on the natural environment. for example, reduced generation of industrial and commercial wastes contributed to the improvement of air quality, creating a similar situation like halted transportation as discussed in section 4.3. in addition, the shutdown of the industrial sector that releases a huge quantity of pollutants has contributed to improving the air and water quality as identified in the model. for some years now, the river ganga and yamuna of india were considered amongst the most polluted water bodies. however, due to the lockdown, the rivers have been reported to appear cleaner and brighter owing to the temporary shutdown of the chemical industries; the major source of river pollution in india (times of india 2020; the economic times 2020c). all these factors are likely to contribute to enhancing the overall environmental quality and flourishing biodiversity/wildlife. benefits for the wildlife in terms of higher reproductive success, less migration, and lower mortality rates (ro 2020) . seismologists suggest that such noise reductions have resulted in less seismic noise, or vibrations in the earth's crust by ~ one-third compared to pre-lockdown levels (ro 2020) . moreover, decreased noise in oceans due to halted cruises is likely to decrease the production of stress hormones in sea fauna (koren 2020) . as shown in the model, humans are also likely to be beneficial given the harmful physical effect of chronic noise such as high stress, disrupted sleep, high blood pressure, cognitive impairment in children, hearing loss, heart disease, etc. (ro 2020). owing to the indirect positive impact of lockdown on the natural environment as discussed above, nature is reviving, thereby contributing to flourished wildlife and biodiversity as depicted in the model. due to the improved water quality in rivers, many of the rare animals have been spotted in the places not seen earlier. for example, the indian gangetic dolphins (one of the four freshwater dolphin species in the world; an iucn endangered species) could be spotted more in vikramshila gangetic dolphin sanctuary, bihar, india, as a result of limited human activity along the river ganga due to lockdown (khan 2020) . the presence of dolphins is a bio-indicator of a healthy river ecosystem (khan 2020) and hence, the lockdown in human society has turned to be a 'blessing in disguise' for the dolphins. elsewise, degradation of water quality in indian rivers due to dumping of municipal and industrial wastes is known to have a negative impact on human health and other aquatic fauna (ganga action plan, govt. of india, https://www.gangaaction.org/actions/issues/solid-waste/). das (2020) reported mass nesting of the endangered olive ridley sea turtles at rushikulya rookery in odisha, india due to the shutdown of touristic activities. in thailand, restriction of fishing and touristic activities has favored the increased spawning of rare leatherback sea turtles (a vulnerable iucn species) (the guardian 2020). basu (2020) reported that restricted j o u r n a l p r e -p r o o f journal pre-proof transportation due to nationwide lockdown has led to flourishing bird diversity in kolkata, india. our model identified the negative impacts of lockdown on education. for instance, government authorities worldwide have mandated shutdown of academic sectors including schools, colleges, and universities in 166 countries to maintain social distancing to curtail the transmission (corlett et al. 2020) . as a result, more than 1.52 billion students, and nearly 60.2 million teachers are no longer in the classroom (un 2020), postponing and/or canceling of examinations and subsequent delay in graduating. nevertheless, the lockdown of academic institutions has provided an opportunity and platform for digital education and online/elearning. yet, the negative impacts of lockdown on education is more overpowering on its positive aspect. on the other hand, we identified both positive and negative impacts of lockdown on research. for instance, the lockdown has frozen many laboratories, and field-based research, thus halting the ongoing research and instigation of new research as well (corlett et al. 2020 ). moreover, travel restrictions have canceled and/or postponed many national and international conferences, meetings, and research stays. yet, the lockdown has also provided ample time for research and innovations (paital et al. 2020) , and to collaborate among the experts globally. given the complexity of ches, the emergence of unprecedented uncertainties is inevitable for a pandemic like covid-19 which was not evidenced in the last century (who 2020). uncertainties mainly arise due to limited current knowledge about the virus and how people j o u r n a l p r e -p r o o f journal pre-proof across the globe modify their behaviors in response to the pandemic (chater 2020) . hence, uncertainty can accelerate fear, stress, panic, anxiousness, loss of trust amongst human society, making us powerless over the direction of life (robinson and smith 2020; who 2020) . in absence of the covid-19 vaccine, it is uncertain if the virus will flare up as restriction gets relaxed; or, whether the lockdown & personal safety measures in addition to contact-tracing and testing, might be able to stamp it out. over time, the ongoing restrictions due to the current crisis are likely to surge the uncertainty over the various elements of human society such as the economy, health, psychological well-being, etc. as discussed in section 4.1.1, governmental intervention such as strict lockdown has potentially impeded the spreading of the virus saving billions of lives worldwide. however, this has come at the cost of doomed economy and income loss due to the shutdown of industry and transportation sectors, etc. as discussed in section 4.1.2, creating a 'health-wealth trade-off'. in the opposite scenario, the relaxation of lockdown would involve a reverse trade-off where the economy recovers at the expense of an increased threat of mass contamination and death. it is therefore uncertain or unclear to decide the best policy measure yet as covid-19 would take a toll either way. this scenario is likely to be worse especially in the developing countries due to the differences in population structure, fiscal capacity, healthcare capacity, higher prevalence of "hand-to-mouth'' households, and the size of the informal sector (alon et al. 2020) . herein, the quantification of trade-offs for a better understanding of the current crisis is urgent for the decision-makers to develop effective policy measures that account for different resource allocation strategies (daher and mohtar 2015) . such quantitative analyses may also assist in understanding how the different policy response priorities to the current pandemic should differ in the developed and developing nations (alon et al. 2020) . another important instance worth mentioning amid the current crisis is the differential scenario of water security in the developed and developing world. until the discovery of j o u r n a l p r e -p r o o f journal pre-proof medicine or vaccine to control the disease, the who has recommended basic protection measures such as the frequent washing of hands and the use of face masks and hand gloves to curtail/spread the virus infection, in addition to maintaining social (physical) distancing. while frequent hand washing is well-practiced in the rich/developed societies/countries having better availability of safe water, millions of people especially in the poor countries/societies are highly susceptible to the virus due to the lack of safe water supply (ndaw 2020). however, in a world with the frequent outbreak of similar pandemics, it is uncertain if only the countries/communities with low/no access to safe water would be affected more. there is a high chance of water scarcity due to water overuse for domestic and hygiene-related practices to prevent or suppress the potential pandemics throughout the world irrespective of its economic stability (kumar 2020b; rohila 2020) . the abatement of air pollution due to lockdown is another instance with high uncertainty. although the emission of co 2 has reduced due to the lockdown/restrictions as discussed in section 4.1.4, such short-term drops in gas emissions are likely to have very little impact on the overall co 2 concentration in the atmosphere given its relentless pile-up and longer residence in the atmosphere. as mentioned in section 4.1.9, flourished biodiversity due to governmental interventions has been one of the bright sides of the current crisis for the natural environment. however, it is uncertain if such liberation would be favorable for the wildlife in the long run. as wild animals venture into settlement areas and human-modified landscapes in search of food and resources, unexpected threats such as human-animal conflicts might arise. this may favor the poachers and opportunistic delinquents as the lockdown prevails, ultimately leading to conservation threats. in addition, the toll on the global economies might also reflect in reduced funding for wildlife conservation and management. illegal encroachment of forested lands is also likely to arise when the forest officials split their time between regular duties and j o u r n a l p r e -p r o o f journal pre-proof helping out with the covid-19 situation. another instance could be the risk for biodiversity and natural habitat by forcing poor people to adopt hunting and illicit lopping of trees for daily livelihood sustenance as a result of the loss of employment as mentioned in section 4.1.7. in-depth and country-tailored assessment & quantification of such uncertainties through developing multiple scenarios for both the developed and developing nations is therefore important to better understand the long-term impacts of such crises on ches. future studies may consider quantifying the trade-offs and uncertainties of the current crisis on ches to assist the decision-makers for better policy-making process. overall, our study demonstrates how the different policy actions i.e., lockdown, socialdistancing, quarantine, etc. against covid-19 has changed the way ches interacts and influences each other. although the crisis has instigated severe ill impacts on human society, it has proved to be a 'blessing in disguise' for the natural environment as discussed in sections 4.1.6, 4.1.8, 4.1.9. restricted/regulated anthropogenic interventions against covid-19 have given rise to a better natural environment for which governments and scientists worldwide have been investing time and money for decades. on the contrary, the current situation urges for the adoption of preventive measures to mitigate ill effects faced by human society as discussed in sections 4.1. 1-4.1.5, 4.1.7, & 4.1.10 . however, the recent situation does not reflect sustainable earth, given the overpowering negative impact of the current crisis on human society. thus, even if the natural environment is benefited due to the ongoing crisis, several uncertainties persist as discussed in section 4.2. the situation is likely to reverse once the lockdown is withdrawn, and both the sub-systems would be affected -the worst-case scenario. over the centuries, humans have imposed dazzled pressure on nature and experienced its repercussions from time to time. thus, in both cases, the benefits are shortterm, which is likely to lead to a pessimistic future where both the sub-system of ches is negatively affected. thus, with a prolonged crisis, it is likely that the aspects of ches would j o u r n a l p r e -p r o o f give rise to several trade-offs and many more uncertainties as discussed in section 4.2. our study, therefore recommends that new policies should aim to convert the short-term gains into long-term benefits, creating an optimistic post-coronavirus world, beneficial for both the sub-systems. given the fact that the human sub-component of ches is experiencing the worst impacts of the crisis, policy actions should primarily focus on mitigating the ill impacts faced by human society. in this regard, our model could help identify the priority areas to understand the vulnerability of the current situation. however, incorporating the perspective of the local stakeholders and policymakers is important while developing a conceptual model. this allows covering the gaps and variations in external political and economic forces on the regional and local environment, which is a limitation of the present study given the sensitivity of the current crisis. the covid-19 crisis might be an 'eye-opener' for humanity. the current predicament reflects that nature has the potential to revive itself given that the anthropogenic interventions are checked. therefore, it is high time to understand and appreciate the complexity of ches and adopt appropriate measures towards tackling the current crisis while maintaining harmony with nature. the main purpose of the study was to propose a conceptual model to portray and address how the interaction of the existing elements of both sub-components of ches -human society and natural environment -are impacted by the various governmental interventions i.e., lockdown, social distancing, quarantine, etc. towards combating the crisis. the merit of our model is that it comprises all possible elements of ches and provides an explicit impression of complex ches amid the crisis. the proposed conceptual model provides an insight into the intricate linkage of ches and helps in understanding the j o u r n a l p r e -p r o o f journal pre-proof complex nexus by identifying the route of short-term impacts of covid-19 measures. thus, our model may be considered as a baseline for further studies and may serve as a precursor towards building quantitative modeling. the model thus may aid in policymaking by identifying the priority areas for discussion and planning in similar other crises as well. future studies may focus on forecasting the long-term impacts of the current crisis through developing scenarios considering the different components of the ches identified in the present study. the first author would like to acknowledge the ipbes and bpbes experts from the 'são dutheil, f., baker, j.s., navel, v., 2020. covid-19 as a factor influencing air pollution?. j o u r n a l p r e -p r o o f how should policy responses to the covid-19 pandemic differ in the developing world? 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indirect effects of covid-19 on the environment short-term effects of ambient pm1 and pm2.5 air pollution on hospital admission for respiratory diseases: case-crossover evidence from shenzhen, china j o u r n a l p r e -p r o o f key: cord-296618-aw4zm23z authors: huang, guanyu; sun, kang title: non-negligible impacts of clean air regulations on the reduction of tropospheric no2 over east china during the covid-19 pandemic observed by omi and tropomi date: 2020-07-21 journal: sci total environ doi: 10.1016/j.scitotenv.2020.141023 sha: doc_id: 296618 cord_uid: aw4zm23z abstract we study the variation of tropospheric no2 vertical column densities (tropno2vcds) over east china during the 2005–2020 lunar new year (lny) holiday seasons to understand factors on the reduction of tropospheric no2 during the outbreak of covid-19 in east china using ozone monitoring instrument (omi) and tropospheric monitoring instrument (tropomi) observations. tropno2vcds from omi and tropomi reveal sharp reductions of 33%–72% during 2020 lny holiday season and the co-occurring outbreak of covid-19 relative to the climatological mean of 2005–2019 lny holiday seasons, and 22%–67% relative to the 2019 lny holiday season. these reductions of tropno2vcd occur majorly over highly polluted metropolitan areas with condensed industrial and transportation emission sources. covid-19 control measures including lockdowns and shelter-in-place regulations are the primary reason for these tropospheric no2 reductions over most areas of east china in 2020 lny holiday season relative to the 2019 lny holiday season, as covid-19 control measures may explain ~87%–90% of tropospheric no2 reduction in wuhan as well as ~62%–89% in beijing, yangtze river delta (yrd) and pearl river delta (prd) areas. the clean air regulation of china also contributes significantly to reductions of tropospheric no2 simultaneously and is the primary factor in the sichuan basin area, by explaining ~56%–62% of the tropospheric no2 reduction there. the covid-19 disease caused by sars-cov-2, a novel coronavirus, was first reported in wuhan, capital of hubei province in china, in december 2019 . this disease had spread quickly in wuhan city and surrounding areas with 258 confirmed cases on january 21, 2020 (world health organization, 2020). by then, confirmed cases were also found in japan, south korea, thailand and eventually worldwide, respectively (world health organization, 2020). the chinese government had announced a strict lockdown and shelter-in-place law in wuhan city on january 23, 2020 tian et al., 2020) . these regulations required people to stay at home without using cars, suspended all public transportations and closed nonessential businesses and manufacturing factories. a day later, other cities in hubei province also conducted similar lockdown and shelter-in-place regulations (tian et al., 2020) . in the following week, the government of china had announced mandatory "shelter-in-place" orders. these covid-19 control measures and consequently minimized human activities in china and worldwide are expected to result in substantially reduced no x (no x = no+no 2 ) emissions due to the dominancy of anthropogenic no x sources (bauwens et al., 2020; collivignarelli et al., j o u r n a l p r e -p r o o f tropspheric monitoring instrument (tropomi) with fine resolutions but only available in 2019-2020 lny holiday seasons. the lny day is set according to the lunar calendar and varies from late january to early february on julian calendars. figure 1 shows the distribution of lny days and the official national holidays during 2005-2020. millions of people in mainland china return to their hometowns from working places in the beginning of the holiday season and travel back to work sites towards the end of the holiday season (li et al., 2016) . the lny holiday season with a large migration usually lasts approximately 40 days, 14 days before the lny's day and 25 days after, as shown in figure 1 . the industrial and transportation-related emissions decrease before the lny's day, stay at a relatively low level during the lny holiday, and then gradually increase back to normal after the holiday. this consequent impacts on air pollution levels is known as the "holiday effect" that shifts with lny days (feng et al., 2016; huang et al., 2012; ji et al., 2018; tan et al., 2009; yao et al., 2019) . as shown in figure 1 , the variation of lny dates on the julian calendar is blurred since we averaged over a 40-day period. the natural emissions of no x is considerably small during lny periods (january to early march) because of low j o u r n a l p r e -p r o o f 6 2.2 omi and tropomi observations level 2 omi tropospheric no 2 product (omno2 version spv3) (krotkov et al., 2019) and tropomi tropospheric no 2 product (version 1.3.0) ( copernicus sentinel-5p, 2018) are used in this study. omi is a push room uv-vis spectrometer that measures the earth's backscattered sunlight since october 2004 aboard the aura satellite (levelt et al., 2006) . the aura satellite is on a sunsynchronous polar orbit with an equator crossing time of approximately 1345 local time (levelt et al., 2006) . the swath width of omi is 2600 km, enabling global daily coverage with a resolution of 13km ×24 km (along × across-track) at nadir. the omi level 2 no 2 standard product is retrieved through a variation of differential optical absorption spectroscopy algorithm (bucsela et al., 2013; krotkov et al., 2017) . omi has been proved with considerably stable performance since the launch in 2004, although omi's global coverage and data sampling have been affected by the "row anomaly" that was first found in 2007 (krotkov et al., 2017) . the impacts of row anomaly on data sampling are shown in figure s1 . as a result, only omi tropospheric no 2 observations of rows 5-23 on clear sky scenes (with cloud coverage less than 0.3) are used, excluding those affected by the row anomaly, to avoid inconsistent sampling of data (duncan et al., 2016; krotkov et al., 2017; krotkov et al., 2019) . tropomi is the single payload aboard the sentinel 5 precursor (s5p) satellite that has a sunsynchronous orbit with local overpass time of approximately 1330 with a near-daily global coverage since april 2018 (veefkind et al., 2012) . the tropomi no 2 retrieval algorithm is j o u r n a l p r e -p r o o f 7 × 3.5 km with a change in the s5p operation scenario since august 6, 2019 (orbit 9388) (eskes and eichmann, 2019) . similar to omi data, we only use tropomi observations with cloud coverage less than 0.3 (eskes and eichmann, 2019) . although tropomi recommended pixels with quality assurance (qa) values greater than 0.75, we use tropomi pixels with qa values greater than 0.5, which includes good quality retrievals over clouds and over snow/ice scenes and is "useful for assimilation and model and model comparison studies" (eskes and eichmann, 2019) , to add more observations to this study in wintertime. in addition, since pixels with qa greater than 0.75 removes cloud scenes with cloud coverage greater than 0.5 (eskes and eichmann, 2019), we use a stricter threshold (<0.3) for cloud coverage to remove pixels that may be influenced by clouds and maintain sampling consistency. furthermore, the difference is small between selecting 0.5 and 0.75 for qa value thresholds with both cloud threshold (<0.3) applied in this study as shown in figure s2 . consequently, the combination of omi and tropomi provides us a long temporal coverage of tropno2vcd observations with a moderate resolution in 2005-2020 lny holiday seasons and a fine spatial resolution in 2019-2020 lny holiday seasons. it is critical to ensure data consistency due to the use of long-term data from two spaceborne data sources. we produce level 3 data over lny holiday seasons by averaging level 2 data to a common, regular 0.125°×0.125° grid and apply corrections to these regridded level 3 tropospheric no 2 data. we use the physical oversampling method by sun et al. (2018) to average temporally and spatially level 2 satellite observations to level 3 grid. two-dimensional super journal pre-proof j o u r n a l p r e -p r o o f 8 gaussian functions are used to represent the spatial response functions of satellite sensors. in comparison with conventional approaches that only consider the pixel corners, this method gives considerable advantages of visualizing the distribution and local gradients of trace gases and for scenarios with short temporal windows (sun et al., 2018) . we directly regrid omi level tropospheric no 2 data to the 0.125°×0.125° grid, while we regrid tropomi level 2 data to 0.01°×0.01° first and then aggregate them to 0.125°×0.125° through area-weighted averaging (sun et al., 2018; zhu et al., 2017) . this is because the physical oversampling method assumes that the sensitivity of a satellite observation is represented by a continuous spatial response function, which is feasible when the grid size is not significantly larger than the satellite footprint. the overpass times of omi and tropomi are 1345 and 1330 local time, respectively (levelt et al., 2006; veefkind et al., 2012) . it is reasonable to assume that omi and tropomi have similar observations on tropospheric no 2 , since the lifetime of no 2 in the troposphere is much longer than 15 minutes (shah et al., 2020) . omi tropno 2 vcds during 2019 and 2020 lny holiday seasons (figure 2 including spectral fitting algorithms, atmospheric mass factor (amf) calculation, and spatial sampling discrepancies due to different pixel size and omi's row anomaly (omi and tropomi spatial sampling on selected days in 2020 are shown in figure s3 ) (cheng et al., 2019; griffin et al., 2019; krotkov et al., 2017) . as a result, a correction should be applied to omi and tropomi level 3 data to reconcile the discrepancies. since we focus on spatially regridded and temporally averaged tropno 2 vcds over lny holiday seasons in china instead of individual retrievals, we apply a simple correction to omi and tropomi level 3 tropno 2 vcds. we obtain mean differences between omi and tropomi level 3 data during 2019 and 2020 lny holiday seasons as: where i, j are latitude and longitude, respectively. omi 2019 , omi 2020 , tropomi 2019 and tropomi 2020 represent level 3 tropno 2 vcds measured by omi or tropomi during 2019 and 2020 lny holiday seasons, respectively. the correction term c(i,j) accounts for the potential sampling and algorithm biases between the omi and tropomi no 2 products, which are assumed to be steady over all lny holiday seasons. therefore, we apply the same corrections to both omi and tropomi level 3 data as follows: corrected omi tropno 2 vcds are defined as wuhan had conducted the strictest lockdown and shelter-in-place regulations in the world (tian et al., 2020) . in the beijing area, ~11%-32% and ~68%-89% of the tropospheric no 2 reduction is caused by the clean air regulations and covid-19control measures, as beijing city has conducted considerably strict control measures (beijing municipal health commission, 2020). ~77%-86% and ~62% of the no 2 reduction in yrd and prd is caused by the covid-19 control measures, as cities of yrd (e.g., shanghai city) and prd (e.g., guangzhou city) had conducted similar control measures as beijing city (health commission of guangdong province, 2020; shanghai people's government, 2020). in the sichuan basin area, however, only 38%-44% of the reduction is caused by the covid-19 measures with the remaining 56%-62% explained by the clean air regulations, due to less strict control measures (health commission of sichuan province, 2020). overall, the ratio of no 2 reduction caused by clean air regulations and covid-19 control measures is associated with how strict the local covid-19 control measures were conducted. we studied the variation of tropno 2 vcds in east china during the 2005-2020 lny holiday seasons and the outbreak of covid-19 by using omi and tropomi tropospheric no 2 observations. we have converted level 2 data of omi and tropomi to 0.125°×0.125° grid level 3 data by using the physical oversampling method (sun et al., 2018) and applied corrections to omi and tropomi no 2 level 3 data to obtain a consistent dataset for this study. the corrections were obtained through the mean difference between omi and tropomi tropospheric no 2 in the 2019 and 2020 lny holiday seasons. impact of coronavirus outbreak on no 2 pollution assessed using tropomi and omi observations beijing city covid-19 prevention information a new stratospheric and tropospheric no 2 retrieval algorithm for nadir-viewing satellite instruments: applications to omi tropospheric no 2 vertical column densities retrieved from ground-based max-doas measurements at shangdianzi regional atmospheric background station in china lockdown for covid-2019 in milan: what are the effects on air quality? satellite no2 retrievals suggest china has exceeded its nox reduction goals from the twelfth 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china. science (80-. ). eabb6105 changes in air quality during the lockdown in barcelona (spain) one month into the sars-cov-2 epidemic tropomi on the esa sentinel-5 precursor: a gmes mission for global observations of the atmospheric composition for climate, air quality and ozone layer applications novel coronavirus (2019-ncov) situationa report-1 the effects of firework regulation on air quality and public health during the chinese spring festival from 2013 to 2017 in a chinese megacity characterization of lead-containing atmospheric particles in a typical basin city of china: seasonal variations, potential source areas, and responses to fireworks long-term trends in no2 columns related to economic developments and air quality policies from formaldehyde (hcho) as a hazardous air pollutant: mapping surface air concentrations from satellite and inferring cancer risks in the united states kang sun acknowledges support from nasa acmap and rrnes programs. the authors declare no conflict of interest. this research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.journal pre-proof j o u r n a l p r e -p r o o f key: cord-269704-ax306loy authors: hospers, lily; smallcombe, james w.; morris, nathan b.; capon, anthony; jay, ollie title: electric fans: a potential stay-at-home cooling strategy during the covid-19 pandemic this summer? date: 2020-07-25 journal: sci total environ doi: 10.1016/j.scitotenv.2020.141180 sha: doc_id: 269704 cord_uid: ax306loy abstract current public health guidance designed to protect individuals against extreme heat and the ongoing covid-19 pandemic is seemingly discordant, yet during the northern hemisphere summer, we are faced with the imminent threat of their simultaneous existence. here we examine the environmental limits of electric fan-use in the context of the united states summer as a potential stay-at-home cooling strategy that aligns with existing efforts to mitigate the spread of sars-cov-2. mitigating extreme heat at home during the covid19 pandemic 4 a growing body of scientific evidence strongly supports the efficacy of several low-resource home-based cooling solutions. for example, skin-wetting has been shown to reduce physiological heat strain, dehydration, and thermal discomfort at temperatures up to 47°c, irrespective of humidity (9) . electric fans are another low-cost, low-energy demand (i.e. ~20-50-times less a/c) (10, 11) cooling strategy. however, their cooling effect during a heatwave is dependent on the prevailing combination of temperature and humidity (12) , which can vary greatly across the united states. fans improve skin surface evaporation in humid conditions, but in low humidity conditions sweat evaporates readily, even without a fan, and therefore fans provide no additional benefit (12) . when air temperature exceeds skin temperature (~35˚c/95˚f) fans also accelerate dry heat transfer towards the body, via convection (13) . a recent clinical trial (12) showed that increases in physiological heat strain and thermal discomfort were lower with fan use during an acute exposure to the peak conditions of the most deadly hot/humid heat wave in recent us history (chicago, 1995; 40˚c/104˚f, 50%rh). while in very hot/arid heat wave conditions (e.g. los angeles, 2018; 47˚c/117˚f, 10%rh) fan-use was clearly detrimental, accelerating body heating and exacerbating cardiovascular strain and discomfort relative to a no-fan control condition. other studies have shown that fans can provide physiological cooling up to air temperatures of 42°c/108°f with ~50%rh (13) . heat loss may also be compromised by a reduced physiological capacity to secrete sweat, common in older adults (14, 15) and individuals taking certain medications (e.g. anticholinergics) (16) , effectively reducing the range of conditions under which a fan is beneficial (15) . however, any potential decrements in sweating can be compensated by externally applying water directly j o u r n a l p r e -p r o o f mitigating extreme heat at home during the covid-19 pandemic 6 ( fig.2a) . according to our model, electric fan use would have been detrimental in a further 15 metropolises, mainly in the south (e.g. austin, tx), on <0.5% of summer days; equivalent to 1-10 days in 20 years (fig.2b ). in the remaining 10 metropolises, mostly in the hot-arid interior of the southwest, fan use would have exerted a heating effect on up to 43.5% of summer days (phoenix, az; fig.2b ). discussion. the present analysis indicates that electric fan-use with light water-spraying potentially offers a feasible stay-at-home cooling strategy during heat extremes for large parts of the us historically experiencing hot-humid summer conditions. in comparison to existing experimental data that demonstrates fan-use providing physiological cooling up to air temperatures of 42°c/108°f with ~50%rh (11) our modelled thresholds appear conservative. the aforementioned study (12) and others (13) were undertaken using young, healthy participants, but it is known that other factors such as age alter the environmental limits for fan-use (16) likely due to age-related decrements in sweating (15) , that limit the potential increase in evaporative heat loss a fan can provide. to establish environmental limits more generalizable to the american public that can be easily adopted in at-home settings we chose to incorporate several conservative components in the current model. examples include the assumption of a low maximal sweat rate (440 mlh -1 ), more representative of an older adult (15) and considerably lower than sweat rates reported in previous experimental research examining fan effectiveness (i.e. average sweat rate in 47˚c/117˚f, 10%rh fan condition = 691 mlh -1 , (12)) and a low volume of water used for skin-wetting (115 ml⸱h -1 / 0.5 cup⸱h -1 ), relative to previously reported self-dousing values (i.e. = 698 j o u r n a l p r e -p r o o f mitigating extreme heat at home during the covid-19 pandemic 7 targeted as a stay-at-home cooling solution, rather than for use in public spaces. there is a lack of evidence suggesting fan-use may aid virus transmission, but given the suggested occurrences where air ventilation systems may have acted as a vector for virus transmission (18, 19) and our constantly developing knowledge of the nature of its spread (20, 21) , it is possible that fan-use may accelerate the distribution of virus particles present in the home. there is indeed inherent transmission risk associated with co-habitation (23, 24) . importantly though, fan use during heat extremes in the home prevents people seeking cooling in public places among individuals whose virus status is less likely to be known than cohabitants, thus limiting personal risk of transmission and further spread in the community. finally, our model identifies the point at which using a fan is better than not using a fan, and therefore does not quantify the amount of cooling, and whether it is sufficient to maintain body temperature within safe limits. nevertheless, even with the conservative approach taken in developing the current model, for 200 million of the ~221.5 million residents (according to 2018 census estimates) in the 105 metropolis areas assessed, fan-use with light water-spraying would have been beneficial (i.e. exerted a cooling effect) relative to not using a fan on more than 199 of every 200 summer days in the past 20 years (fig.2c ). it is therefore clear that public health officials should not advise people to turns fans off during heat waves as is current practice in a range of jurisdictions (25,26). while public health officials strive to protect all citizens during the current pandemic, parallel efforts are also required to proactively prepare for the likely overlap of covid-19 with extreme heat. heatwave preparation plans are increasingly centred on building community resilience and protecting the most vulnerable members of society (27, 28, 29) . whilst this approach must continue, we require adaptive, yet evidence-based, efforts to protect against the ill-effects of extreme heat that align with current public methodological overview. the present model was created based around an elderly adult (+65 y), with a body mass of 70 kg, a height of 1.73 m, and a calculated body surface area (bsa) (30) of 1.83 m 2 , seated at rest, in light clothing, while wetting their skin either with or without the use of an electric fan in a variety of heatwave conditions. the model was created using standard partitional calorimetry equations (13, 31) and has been updated from an earlier model4 based upon the findings of several clinical laboratory experiments (9, 12, 14, 16, 32) . the partitional calorimetry method relies upon first principles thermodynamic heat transfer equations, which determine the body's net heat flow by comparing the total amount of heat produced within the body to the total amount of heat gained or lost to the environment, through all available avenues of heat transfer (i.e. conduction, convection, radiation and evaporation) (27) . accordingly, fan use was determined to be detrimental when the net amount of heat lost to the environment was greater with the fan off compared to having the fan on. below are the detailed equations and assumptions used to produce the model. partitional calorimetry equationsdetermining the required amount of evaporation. the primary argument informing this model is that, once ambient air temperature exceeds skin temperature, fan use will increase heat gain from the environment through dry heat transfer via convection (i.e. like a convection oven), necessitating a greater required amount of evaporation to maintain heat balance. however, fan use will simultaneously increase the maximal amount of heat that can be lost to the environment through evaporation, as well as improve sweating efficiency (10) . accordingly, to determine whether fan use is overall beneficial or detrimental during a heatwave, the amount of total heat gain and loss from fan use needs to be assessed. this was done using the conceptual heat balance equation ( as evaporation is the primary method by which humans lose heat during moderate and more severe heat stress conditions (34) , and that this is the primary heat loss avenue controlled by the autonomic nervous system (34) , this equation was subsequently reorganized to determine the required amount of evaporation (e req ) to maintain heat balance (i.e. establish a steady-state core temperature): eq2: here, when all other variables are held constant (as they would be at rest), an increase in dry heat transfer (primarily via convection) would necessitate an increase in e req . within the present model (seated rest) w can be eliminated as no external work is performed. for m, we assumed a resting metabolic rate of 65 w·m -2 , which is equivalent to a person standing (35). a typical value for m when seated could be as low as 58 w·m -2 , however, the highest potential value was selected to represent the worst-case scenario in terms of metabolic heat that must be dissipated to maintain a stable body temperature (35). in order to account for heat loss due to respiration, the following equation was used (36): eq3: where p a is the partial pressure of water vapor of ambient air in kp a and t a is ambient air temperature in ºc. next, dry heat transfer (the combined effect of convection and radiation) was accounted for (37): where t sk is mean skin temperature in ºc (assumed to be 35.5°c based on the literature (38, 39) ; t o is operative temperature in ºc, which in this case was equal to ambient air temperature; r cl is dry heat transfer resistance of clothing in m 2 ·k·w -1 ; f cl is the unitless clothing area factor (see eq5) and h is the where is skin wettedness (i.e. proportion (0 through to 1) of bsa covered with sweat (48); p a the water vapor pressure in the ambient air in kpa; p sk,s is the partial water vapor pressure at the skin in kpa (equal to saturated water vapor pressure at skin temperature (35.5ºc), i.e. 5.78 kpa); r e,cl is the evaporative resistance of clothing in m 2 ·kpa -1 ·w -1 ; f cl is clothing area factor [see eq. (2) employed. similarly to r cl , this value was determined using iso 9920 (2007) (40) and was equivalent to a typical summer ensemble, inclusive of air layers. for the "fan off" condition, an r e,cl value of 0.0237 m2·kpa -1 ·w -1 was used for the whole body. in addition to e max , which is determined by the physical properties (i.e. temperature, water vapor content and air speed) of the skin and the surrounding the environment as well as reductions alterations in actual attainable skin wettedness, the actual attainable e max will be dictated by the maximum amount of sweat which can be produced. for the purpose of our model this was assumed to be 440 mlh -1 based upon the j o u r n a l p r e -p r o o f where sr is the sweat rate (in our model assumed to be (440 mlh -1 ), sw latent is the latent heat of the vaporization of sweat (2426 jg -1 ) (46), 3600 is the factor needed to convert mlh -1 to gs -1 and sw eff is the sweating efficiency, i.e. the proportion of sweat produced that is evaporated from the skin surface (thereby contributing to evaporative heat loss) as opposed to sweat that drips off the body and does not contribute to heat loss. sweating efficiency is calculated by (52): where  req is the skin wettedness required for heat balance determined by (47): eq13: = (no units) weather data analysis. finally, to determine whether (in conjunction with exogenous skin wetting) an electric fan should be used in given environmental conditions, a final equation was generated: where e reqoff and e reqon are the required amount of evaporation with a fan off or on, respectively, and e maxloff and e maxlon was the lower value of the calculated e max and sw max terms with fan off or on, respectively. this equation was subsequently entered into an environmental conditions matrix that ranged from 30°c to 50°c in 2°c increments and from 5% to 100% relative humidity in 10% increments (with the exception of 5% to 10% relative humidity). in order to ensure only the hottest weather was included in the analysis, only weather from daylight hours during the months of june, july and august were analyzed. from this data, the following metrics were ascertained: the peak temperature and corresponding relative humidity, the number of days where recorded temperatures exceed the calculated upper temperature limit at which point fan use is no longer beneficial and the total number of days included in the analysis (typically 1839 days, but this differed slightly due to missing data from select weather stations). these data are displayed in supplementary table a1 as well as within the manuscript figure 1 . clinical characteristics of patients who died of coronavirus disease 2019 in china this time must be different: disparities during the covid-19 summertime acute heat illness in u.s. emergency departments from tips for preventing heat-related illness protect yourself from the dangers of extreme heat coronavirus makes cooling centers risky, just as scorching weather hits will summer kill coronavirus? cities fear heat waves will quickly becomes deadly interim guidance to reduce the risk of introducing and transmitting sars cov-2 (the agent responsible for causing covid-19 disease) in cooling centers a preliminary study of the effect of dousing and foot immersion on cardiovascular and thermal responses to extreme heat fanning as an alternative to air conditioning-a sustainable solution for reducing indoor occupational heat stress an intelligent approach of regulating electricfan adapting to temperature and relative humidity the effects of electric fan use under differing resting heat index conditions: a clinical trial corp: partitional calorimetry heart rate and body temperature responses to extreme heat and humidity with and without electric fans regional differences in the sweating responses of older and younger men cardiac and thermal strain of elderly adults exposed to extreme heat and humidity with and without electric fan use daily indoor-to-outdoor temperature and humidity relationships: a sample across seasons and diverse climatic regions role of air distribution in sars transmission during the largest nosocomial outbreak in hong kong evidence of airborne transmission of the severe acute respiratory syndrome virus aerosol and surface stability of sars-cov-2 as compared with sars-cov-1 transmission of sars-cov-2: implications for infection prevention precautions household transmission of sars-cov-2 characteristics of household transmission of covid-19 department of homeland security. when it's too hot for a fan drug-induced hyperhidrosis and hypohidrosis assessing health vulnerability to climate change: a guide for health departments; climate and health technical report series climate and health program heat response plans: summary of evidence and strategies for collaboration and implementation; climate and health technical report series climate and health program integrating public health into climate change policy and planning: state of practice update a formula to estimate the approximate surface area if height and body mass be known thermal interchanges between the human body and its atmospheric environment age modulates physiological responses during fan use under extreme heat and humidity. medicine and science in sports and exercise thermometry, calorimetry, and mean body temperature during heat stress steady-state sweating during exercise is determined by the evaporative requirement for heat balance independently of absolute core and skin temperatures. j 36. handbook a. fundamentals mechanisms of heat exchange: biophysics and physiology sweating sensitivity and capacity of women in relation to age thermal and metabolic responses to heat exposure in obesity ergonomics of the thermal environment--estimation of thermal insulation and water vapour resistance of a clothing ensemble a comprehensive data base for estimating clothing insulation heat loss from animals and man: assessment and control the stress of hot environments convective and radiative heat transfer coefficients for individual human body segments calculation of thermal comfort-introduction of a basic comfort equation heat of evaporation of sweat: thermodynamic considerations j o u r n a l p r e -p r o o f key: cord-264152-0jr5nlli authors: bhattacharya, raj kumar; chatterjee, nilanjana das; das, kousik title: sub-basin prioritization for assessment of soil erosion susceptibility in kangsabati, a plateau basin: a comparison between mcdm and swat models date: 2020-05-16 journal: sci total environ doi: 10.1016/j.scitotenv.2020.139474 sha: doc_id: 264152 cord_uid: 0jr5nlli abstract kangsabati basin located in tropical plateau region faces multiple problems of soil erosion susceptibility (ses), soil fertility deterioration, and sedimentation in reservoirs. hence, identification of ses zones in thirty-eight sub-basins (sb) for basin prioritization is necessary. the present research addressed the issue by using four multi-criteria decision-making (mcdm) models: vlsekriterijumska optimizacija i kompromisno resenje (vikor), technique for order preference by similarity to ideal solution (topsis), simple additive weighing (saw), compound factor (cf). to determine the best fitted method from mcdm for erosion susceptibility (es), a comparison has been made with soil and water assessment tool (swat), where fifteen morphometric parameters were considered for mcdm, and meteorological data, soil, slope and land use land cover (lulc) were considered for swat model. two validation indices of percentage change and intensity change were used for evaluation and comparison of mcdm results. with swat model performance, swat calibration and uncertainty analysis programs (cup) was used for sensitive analysis of swat parameters on flow discharge and sediment load simulation. the results showed that 23, 16, 18 sb have high es; therefore they were given 1 to 3 ranks, whereas 31, 37, 21sb have low es, hence given 38 to 36 rank as predicted by mcdm methods and swat. mcdm validation results depict that vikor and cf methods are more acceptable than topsis and saw. calibration (flow discharge r2 0.86, nse 0.75; sediment load r2 0.87, nse 0.69) and validation (flow discharge r2 0.79, nse 0.55; sediment load r2 0.79, nse 0.76) of swat model indicated that simulated results are well fitted with observed data. therefore, vikor reflects the significant role of morphometric parameters on es, whereas swat reflects the significant role of lulc, slope, and soil on es. however, it could be concluded that vikor is more effective mcdm method in comparison to swat prediction. soil is the most sustaining natural resource for all living organism, and it determines geomorphic processes widely (keesstra et al., 2016; ameri et al., 2018; hembram and saha, 2018) . sustainable agricultural development and natural resource utilization both are largely determined by soil erosion; furthermore, this erosion is controlled by several hydrological functions in the watersheds worldwide (molla and sisheber, 2017; of morphometric parameters at sub-basin level. in swat model, various weather datasets including temperature, humidity, wind speed, solar radiation at 12 grid points in kangsabati basin were automatically collected from climate forecasting system reanalysis (cfsr) world climatic database (http://globalweather.tamu.edu/). while rainfall database has been modified with thirty five years average dataset of sixteen local rain gauge stations in this basin as provided by indian meteorological department (imd), for getting better accuracy of model. average rainfall datasets were further fed into swat database through the incorporation with nearest cfsn grid points. in term of spatial resolution scale, temperature data was only available with coarser resolution scale of 1"×1" (approximately 110km×110km), but other weather databases were available with finer resolution scale of 0.25"×0.25" (approximately 27.5km×27.5km), respectively (himanshu et al. 2019) . data processing phase involved with two major steps, where first step comprises on scanning georeferences and image rectification. after that, rectified images were converted into resembled sheet, passes with masking and mosaic processes, derived from universal transverse mercator projection of wgs 1984 (45°n) using arc gis 10.2. second step comprises of boundary demarcation for extraction of stream number and its contributing area of specific outlets, flow direction, and flow accumulation in each dem pixel, using arcswat tools. in order to attain high accuracy value, srtm dem was used for comparison and clarification of sub-basin boundary with topographical maps, and extracted three dominant morphometric aspects i.e. basin shape, linear and landscape. table 1 presents the measuring techniques of nineteen major morphometric parameters following such literature. after extracting morphometric parameters, four mcdm methods of topsis, vikor, saw, and cf were applied to predict the sub-basins priority for estimating es in kangsabati basin at sub-basin level, retrieved from their validated results of percentage change and intensity change. in contrary, swat model was applied to estimate the flow discharge and sediment load, as well sediment yield for the assignment of actual sub-basin priority rank, and then make a comparison between effective mcdm methods and swat model. vlse kriterijumska optimizacija i kompromisno resenje (vikor) is used for comprising of alternative conflicting criteria based on ranking sets under optimizing complex systems, introduced by opricovic and tzeng (2004) . performance of vikor method as closeness of ideal is entirely depended on well organization following nine steps (huang et al., 2009; ameri et al., 2018) . where pij means element of normalized decision matrix and rij mean i-th alternative sets in j-th criteria. (iii) third stage comprises of weight assignment for each requiring criteria using analytical hierarchical process (ahp). vikor method also helps to re-evaluate all criteria, makes pair wise comparison, using saaty's method (1977) in expert choice software. (iv) after that, weighted normalized matrix has been computed through the multiplying normal matrix in each criterion weight, given by huang et al. (2009) and sanayei et al. (2010) as eq. (2): where t ij means element of the weighted normalized decision matrix, p ij means element of normalized decision matrix and w j mean computed weight criteria given by ahp model. (v) fifth stage mainly involved with the determination of best value (xj ) and worst value (x ̶ j ) of all standard criteria functions; if j=1, 2...n: where j-th criterion as most benefited criterion for the causes of maximum j-th value. this criterion becomes more relevant for this purpose. then xj =max ƒ ij , ƒ̶ ij = min ƒ ij . (vi) purpose of this stage is to compute maximum group utility index (si) and minimum individual regret index of opponent group values (r i ) following respective eq. (3) and (4): where w i mean jth criterion weight that means relative importance of criteria, v * j mean maximum x ij , and v * j mean minimum vj . (vii) computation the value of q i following i=1, 2...m as eq. (7) (el-santawy, 2012): where s * mean minimum s j , s mean maximum s j , r * mean minimum of r i , r means minimum of r i , and v as introductory weight strategy of maximum group utility (s j ) and maximum criteria (r j ). q value generally ranges from 0-1; in terms of range value, v> 0.5 denotes that trend value of q index reaches in majority rule. (viii) alternative rank order has considered as sorting measurement from s, r and q values, where suitable alternative values are assigned from least value of three major parameters. (ix) two conditions are used to determine the best alternative value from highest rank order of q values as follow eq.6 (el-santawy, 2012; ameri et al., 2018): c1 or acceptable advantage: j o u r n a l p r e -p r o o f 7 where a 1 , a 2 means first and second alternative position in the ranking list; n is the number of alternative criteria. c2 or acceptable stability in decision making: in terms of satisfaction level, alternative rank values are assigned as rank 1 in q, s and r or both of them. on the contrary or unsatisfactory level, ranking order of alternative value would be assigned as a 1 , a 2 ...am where am measured by following eq. 7: according to tzeng (2004, 2007) , a 1 and a 2 must be selected for best solution, where outcome of c1 does not satisfy. technique for order preference by similarity to an ideal solution (topsis) is a distance-based method, presented by hwang and yoon (2012) . principle of topsis indicates that measurement of alternative choice has been computed by euclidean distance from shortest distance of positive ideal solution (pis) and largest distance of negative ideal solution (nis). in this context, closeness coefficient is used to express the results of pis and nis distances. in order to closeness coefficient value, preferred alternative value is taken as a higher coefficient value from a set of alternatives (liou and wang, 1992; kannan et al., 2009) . this model has detected rating option following some calculation steps (hwang and yoon, 1981) : (i) this step estimated normalized decision matrix (r ij ) as eq. (8): where r ij presents normalized decision matrix element and a ij mean alternative performance of i-th under j-th criteria. (ii) this step computed as weighted normalized decision matrix (v ij ) following eq.9: where r ij mean normalized matrix elements and w j mean weight of j-th criteria (iii) this step computed the pis and nis using eq. 10 and 11 (ameri et al., 2018) where j mean benefitted criteria and j mean cost criteria, respectively. (iv) this step computed as separation measures from ideal solution using euclidean distance (n-dimension). separation from ideal distance of pis and nis measured as following eq. 12 and 13 j o u r n a l p r e -p r o o f (v) purpose of the final step, is detect closeness coefficient of alternatives from ideal solution ranges 0 to 1 using eq. 14. superior values are estimated from higher relative closeness alternative values. where cl i+ mean closeness coefficient, d i+ mean positive ideal solution (pis) and d i-mean negative ideal solution (nis). this is another leading mcdm method, which assigned score in each option, and obtained by aggregating values in different criteria. relative weights are taken for assigning each criteria score using decision maker (hwang and yoon, 1981; sargaokar et al., 2010) . simple additive weighting (saw) model estimated rating option following consecutive steps as (i) decision matrix is used for the determination of normalized initial matrix (r ij ) of j-th criterion as eq.15 (ameri et al., 2018): where x ij mean initial weights and m means criteria number (ii) this step involved mainly determined the relation as r ij = r ij min or r ij = r ij max two different relation can be obtained from normalized weight, where minimum value in efficiency index represent as r ij =r ij min , and maximum value in efficiency index represent as r ij =r ij max . (iii) consistency index helps to determine as normalized value following eqs. 16 (maximum efficiency index) and 17 (minimum efficiency index): (iv) the purpose in this step is determining the weighted normalized decision matrix (v ij ) following eq.18: where w j mean criteria weight of analytical hierarchical process (ahp) model (v) final step of saw model involved mainly data integration, acquired from final score value in each option (a i ) following eq.19 (ma et al., 1999; ameri et al., 2018) : compound factor (cf) is an important mcdm methods, which is used for subject base conversion phenomena obtaining from two estimation of logical learning estimation and knowledge-driven framework codes based numerical estimation (todorovski and dzeroski, 2006; ameri et al., 2018; hembram and saha, 2018) . in this study, cf method was applied for assignment of rank order in each estimated morphometric parameters that are where r denote parameters rank value, pn denote watershed rank from each parameter cf is estimated rank order or erosion priority scale of sub-basin level from fifteen morphometric parameters in thirty-eight sub-basins of kangsabati basin. according to patel et al. (2012) and balasubramanian et al. (2017) , high es has corresponded with maximum compound value of areal and linear aspect, which is given rank 1 and second highest compound value is given rank 2 and others in same assigning manner. while high es has corresponded with minimum compound value of shape aspect, which is given rank 1 and so on. percentage change and intensity change are uses for the assessment of validation performance and comparison among four mcdm methods results that are predicted ses at sub-basin level (badri, 2003; ameri et al., 2018) . percentage of changes is expressed as eq. 21: where δp denote percentage of changes, n denote alternative numbers, and n constant denote alternative numbers of same rank intensity of changes is expressed as eq.22: where δi denote intensity of changes, r1 denote first method of alternative rank, and r2 denote second method of alternative rank several predominant parameters like weather condition, topographic characteristic, soil properties, and land use land cover (lulc) were required for successful set-up and run the swat model on a monthly time-scale (1.1.2010-31.12.2015) using the arcswat interface (neitsch et al., 2005; markhi et al., 2019) . database of slope, soil and lulc distribution map over the thirty-eight sub-basins including 12387 hrus are presented in fig.3a , b, c. the unique combinations of lulc and soil type were separately represented by two different hru. 5% of slope, 5% of soil and 5% of lulc were assigned as user threshold values for the determination of in hru tool box. other important data sets like weather databases including rainfall, temperature, and evaporation etc. were extracted from imd and cfsr world weather gridded database. on the other hand, hydrological data sets of monthly flow discharge or outflow data and sediment load were collected from mohanpur station, only available monthly flow discharge data set was and collected from irrigation office of paschim medinipur, but there is no record of any observed data on sediment load. in this context, total sediment load (q t ) was computed from field observation database of nine fluvial and sediment hydraulic variables (average flow velocity, water depth, weight of specific water, kinematic viscosity of water, gravity acceleration, sediment diameter, weight of specific sediment, shear velocity, bed shear stress) in mohanpur station. total sediment load was calculated in ton unit using fluid weight of ackers and white (1973) method (bhattacharya et al., 2019a) ; furthermore, those results were comparing with the swat simulation results. moreover, sediment load data sets helped in swat sensitivity analysis, including calibration and validation test on observed and simulated sediment load. total sediment load (q t ) has measured from eq. 23: j o u r n a l p r e -p r o o f = . (23) where q denote water discharge, x denote sediment concentration sensitive analysis of swat parameters must be needed for the determination of significant contribution on model outputs that are measured by ranking method ( parameters are selected for the analysis of calibration and validation performance in swat model using p-value (mittal et al., 2015) . p-value means fraction values of observed discharge data under 95 percent prediction uncertainty (95ppu) band, which ranges from 0 to 1 (vaghefi et al. 2013; mittal et al., 2015) . in this study, pvalue of <0.05 was considered for selection of sensitive parameters in calibration and validation analysis. to determine the calibration and validation of results, iteration steps were required to find out the optimum values for two different times (yang et al., 2008) . therefore, the calibration (1.1.2010-31.12.2013) and validation (1.1.2014-31.12.2015) tests between observation and simulation data were applied to determine the model performance. in this context, mohanpur gauge station was taken for this purpose to make a comparison between observed data and swat simulated results for both flow discharge and sediment load estimation. nash-sutcliffe efficiency criterion (nse) was used for the determination of calibration result in observation data (nash and sutcliffe, 1970) . this well-known statistical criterion provided the coefficient determination (r 2 ), nash-sutcliffe efficiency criterion (nse), and percent bias (pbias) values that were obtained from eq.24, 25, 26, respectively. where y sin denote simulated value, and y obs denote observed value; z obs refer to mean of observed value as n; and z sin refer to mean of simulated values as n j o u r n a l p r e -p r o o f basin morphometric parameters play significant role to determine the earth system processes in surface, incorporating geomorphology, geology and hydrological sets-up (ifabiyi and eniolorunda, 2012; balasubramanian et al., 2017) . moreover, relief and drainage system in the entire basin, have great influence on soil erosion vulnerability, whereas three major morphometric aspects like linear, relief and shape, have control the runoff volume and infiltration capacity (sharma et al., 1985; hembram and saha, 2018) . this basin area is extended to 6480 km 2 with perimeter of 3306 km 2 , and texture with 6971 stream number, including 833 km 2 stream lengths. 5321 first stream order were identified in high erosion prone sites in the entire catchment area. according to erosion rate, fifteen morphometric parameters were taken from thirty-eight sub-basins to assign the (2012) denoted that all shape parameters are inversely correlated with es. in order of erosion priority rank, this study considered maximum value of mean bifurcation ratio and relief ratio that were assigned as highest rank and minimum value of those parameters assigned as lowest rank. in this research, weight assignment in each criterion was computed from final matrix table that was prepared from fifteen morphometric parameters using ahp method. according to saaty (1977) , weight assignment becomes accepted; if incompatibility rate in a final matrix is lower than 0.1. in this study, consistency index (ci) and randomness index (ri) in comparison matrix table is 0.08 and 1.59, respectively; however, incompatibility rate of final matrix become 0.054; therefore, weight assignment of effective morphometric parameters on es are within acceptable range (table 2 ). in addition, weight assignment of fifteen morphometric parameter in matrix after the weight assignment, all morphometric parameters were calculated for the preparation of decision matrix and data normalization that are essential for priority rank of vikor, topsis, saw, and cf models. in this study, fifteen morphometric parameters were used for the computation of priority rank in each sub-basin, where all data sets were normalized to prepare the rank value in four different mcdm methods. linear vector method j o u r n a l p r e -p r o o f was used for the computation of data normalization in topsis model , whereas data normalization of vikor and saw models were computed following eqs. 1-7, 15-19 (ameri et al., 2018) . in vikor model, best and worst values in each criterion helps to normalization of regret levels; however, based on perspective of regret theory, only best values in each criterion play dominant role to determine the regret levels, and worst values in each criterion play dominant role to determine the effective role of normalized s and r values on regret levels (huang et al., 2009) . in this study, best and worst values are calculated in table 3 using eqs. 1-2, whereas utility index, regret index both were determined the priority rank as ascending order in the thirty-eight sub-basins using eqs. 3-5 (table 3 ). in topsis model, positive value, negative value and euclidean distance between them were calculated using eqs. 8-13 and is presented in (fig. 5a ). in respectively. it is a point that sub-basins with more complex score have high sensitivity to erosion, and subbasins with least final score have low sensitivity to erosion (fig.5c) (fig. 5a, b, c) . on the other hand, based on compound values from selected morphometric parameters, cf model has classified into four categories i.e. very high (>100), high (50-75), medium (25-50) and low (>25). in this study, only two cf categories of moderate and low are identified in the thirty-eight sub-basins (fig.5 d) in general, swat model performance is evaluated by three different analysis of sensitivity, calibration, and validation from assigned parameters (welde, 2016) . in this study, sensitive analysis was done in a latin hypercube sampling at 12 intervals, where twenty parameters were considered for flow discharge and sediment load estimation. 1000 iterations were used for the determination of following parameters, where 500 iterations for flow parameters (10×50 per iteration), and 500 iterations for sediment parameters (10×50 per iteration) were required with the help of swat-cup software. table 7 denotes maximum, minimum and fitted values of ten sensitive parameters for flow discharge simulation. table 8 denotes maximum, minimum and fitted values of ten parameters for sediment load simulation. sensitivity analysis reveals that cn2.mgt (number of scs runoff curve in moisture condition ii) is more sensitive followed by gwqmn.gw (occurring of return flow for threshold depth of water) in flow discharge calibration and validation. while r_spexp.bsn (exponent parameter for calculating sediment recent rained in channel sediment) is more sensitive followed by r__slsubbsn.hru (average slope length) in sediment load calibration, but hru_slp.hru (average slope steepness) is more sensitive followed by r_spexp.bsn in sediment load validation. after the successful run of calibration procedure on sensible parameters, table 7 therefore, based on all statistical indices of calibration and validation, simulated results are considered as goodness of fit with observed data. suspended sediment load and its movement in stream has entirely depended on several hydraulic variables like stream discharge, watershed slope, including flow and sediment regime characteristics (sridhar et al., 2018; bhattacharya et al., 2020a) . huge sediment load helps to accumulation of sediment yield at sub-basin level where swat model is applied to estimate the amount of yield following some considerable hydrological parameters (welde, 2016 figure 7 showed that most of the basin area come under low to medium sediment yield priority class, whereas high and very high sediment yield classes are mainly concentrated at outlets or confluence points. generally, absences of flow discharge, low drainage density and lower catchment area helps to generate low sediment yield, while presence of confluence points, high drainage density and large catchment area helps to accumulate of high sediment yield (bhattacharya et al., 2020a) . in terms of es at sub-basin level, monthly sediment yield priority is classified into four classes i.e. according to assigned rank of simulated sediment yield, very high erosion priority class mainly concentrated in sb 13, 16, 18, 19, 23 , while high erosion priority class concentrated in sb 2, 6, 14, 17, 20, 22, 25, 26, 28 and 31, respectively (fig. 8 ). in addition, sb 1, 3, 4, 5, 7, 8, 9, 10, 12, 15, 24, 29, 30, 32 and 34 having monthly sediment yield of 0.70-0.93 m ton/ha comes under moderate erosion priority class, and sb 1, 3, 4, 5, 7, 8, 9, 10, 12, 15, 24, 29, 30, 32 and 34 having monthly sediment yield of 0-0.69 m ton/ha comes under low erosion priority class. therefore, it is pointed that amount of sediment yield are fully dependent with es level throughout the basin. classes throughout the basin. these susceptible classes are major sediment source sites where huge sediment load supply helps to vast accumulation of sediment yield. therefore, vikor method is an effective mcdm model, which helps to identify the erosion-prone sites, sediment load supply, and sediment yield accumulation throughout the basin. morphometric parameters are not considered as only key factors for the determination of es, but other dominant geo-environmental parameters such as lulc, soil erodibility, slope length-steepness, lithology, geomorphic setup, etc. are also important (chauhan et al.,2016; bhattacharya et al., 2019b) . in comparison between mcdm methods and swat model, effective mcdm methods are helpful to identify the significant role of morphometric parameters on es; furthermore, linear and aerial aspects are positively correlated with es (nooka ratnam et al., 2005; bhattacharya et al., 2019b) , but shape aspects are inversely correlated with es (patel, 2012 (patel, , 2013 . in contrary, when preparing sediment yield distribution map from seven considerable factors: lulc, slope, soil, ground water depth, run off volume, precipitation lapse rate and channel hydro-morphogenetic properties (markhi et al., 2019; himanshu et al., 2019) , swat model also helps to assess es in each sub basin. therefore, in this study, lulc and morphometric parameters are considered for es assessment following the validation performance of mcdm and swat models, respectively. in terms of response to erosion priority, land covers like laterite with barren land, wasteland, and settlement are positively related to es, while agricultural land, dense forest, pasture land are inversely related to es (altaf et al., 2014) . based on mcdm validation performances; topsis, saw and cf does not give satisfactory results due to disadvantages of unavailable data sets for all decision-making problems and assumption based relative weight assignment in each variables (khosravi et al., 2019) . in contrast, vikor method has given better results than other mcdm methods, which are validated by swat model for its advantages: hierarchical formulating issue, pair wise comparison using expert quantitative and qualitative knowledge, and assessment of compatibility and incompatibility decision (saaty, 1980; arabameri et al., 2019) . swat and vikor helps to understand the role of lulc and morphometric properties on es in kangsabati basin. in spite of dense vegetation cover and pasture land, sb 13, 16, 18, 23 are more susceptible to erosion due to maximum values of linear morphometric parameters (mean bifurcation ratio, drainage density, drainage texture, stream frequency) and relief morphometric parameters (slope, ruggedness index, relief ratio, basin relief) as well as minimum values of basin form parameters (form factor, shape factor, compact coefficient and circular ratio) (fig.9 ). in contrast, despite the presence of barren land, double crop practice and dense settlement, of 0.8073 m ton/ha. thus, based on the above discussion, it can be said that among all the available mcdm methods for es, vikor model is more pragmatic for es in respect to simulated sediment yield rank as predicted by swat. in order to es and sediment yield deposition at sub-basin level, in this study demonstrated that vikor is fittest mcdm model for suitable selection of best and worst values from morphometric parameters using normalize decision matrix of ahp, maximum group utility index, minimum regret index of opposite group value, as well as assessment of compatibility and incompatibility decision among effective morphometric parameters. therefore, vikor model is useful mcdm method to prepare rational sub-basin prioritization from linear normalize ranking of all morphometric parameters. moreover, vikor method helps to identify the five critical sub-basins that are most sensible to erosion due to presence of responsible morphometric parameters in line with the results of bhattacharya et al. (2020a) . on the other hand, swat parameters helps to determine the significant role of morphometric parameters on es in response to sediment yield deposition throughout the basin. therefore, it can be stated that morphometric parameters are considered as crucial contributing parameters for es generation in this plateau fringe basin, followed by lulc patterns, climate, and soil characteristic. these agreements are validated with the findings of biswas et al. (1999) , hembram and saha (2018) , sridhar et al. (2018) . based on literature review in introduction, previous researchers have presented sub-basin prioritization in order to es using mcdm methods; however, there is no hydrological model to measure the significant role of hydrological parameters like runoff volume, sediment load, sediment concentration, etc. on sub-basin prioritization. in this context, there is research gap in previous studies of sub-basin prioritization. present study tried to address this research gap using a comparison between mcdm and swat models. in term of es, present study humbly argues that effective morphometric and hydrological parameters are prerequisite for sub-basin prioritization in any region in the world as assigned by vikor and swat models. moreover, both models reveal that all morphometric and hydrological parameters are not equally significant in every sub-basin as they have own characteristics. the findings in this research might help to identify critical sub-basins where es has been found most severe with the presence of responsible factors, thus vikor and swat could provide important tools for planner or policy maker to take rational strategies for soil and water conservation in watershed management. the present study demonstrated that es is a sensitive criterion to determine the sub-basin prioritization using a and suggestions which were immensely benefitted to improve our manuscript during revision process. abbaspour prediction of land use changes based on land change modeler and attribution of changes in the water balance of ganga basin to land use change using the swat model identification of erosion-prone areas using different multi-criteria decision-making techniques and gis a comparison of statistical methods and multi-criteria decision making to map flood hazard susceptibility in northern iran a topsis-based multicriteria approach to the calibration of a basinscale swat hydrological model models of rural planning. pamphlets practical lesson in geography rural planning prioritization of subwatersheds based on quantitative morphometric analysis in lower bhavani basin, tamil nadu, india using dem and gis techniques multi-criteria-based sub-basin prioritization and its risk assessment of erosion susceptibility in kansai-kumari catchment area land use and land cover change and its resultant erosion susceptible level: an appraisal using rusle and logistic regression in a tropical plateau basin of west bengal effect of instream sand mining on hydraulic variables of bedload transport and channel planform: an alluvial stream in south bengal basin estimation of erosion susceptibility and sediment yield in ephemeral channel using rusle and sdr model: tropical plateau fringe region, india gully erosion studies from india and surrounding regions prioritisation of sub watersheds based on morphometric analysis of drainage basin: a remote sensing and gis approach simulation of sediment yield using swat model: a case of kulekhani watershed geospatial assessment of soil erosion vulnerability at watershed level in some sections of the upper subarnarekha river basin quantitative geo-morphometric and land cover-based micro-watershed prioritization in the tons river basin of the lesser himalaya integration of hydrological factors and demarcation of groundwater prospect zones: insights from remote sensing and gis techniques a vikor method for solving personnel training selection problem the index of drainage intensity-a provisional new drainage factor the soil and water assessment tool: historical development, applications, and future research directions gully erosion susceptibility assessment and management of hazard-prone areas in india using different machine learning algorithms multi-criteria decision making on the energy supply configuration of autonomous desalination units characterization and evolution of laterites in west bengal: implication on the geology of northwest bengal basin electre: a comprehensive literature review on methodologies and applications grundriß der gesamten gewasserkunde, band 1: flußkunde. compendium of hydrology, i prioritization of sub-watersheds for soil erosion based on morphometric attributes using fuzzy ahp and compound factor in jainti river basin evaluation of best management practices for sediment and nutrient loss control using swat model drainage basin characteristics erosional development of streams and their drainage basins: hydrophysical approach to quantitative morphology a revised vikor model for multiple criteria decision making-the perspective of regret theory multiple attribute decision making: methods and applications a state-of-theart survey watershed characteristics and their implication for hydrologic response in the upper sokoto basin hydrological modeling for micro watersheds using swat model. 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laffey, john g. title: challenges and solutions for addressing critical shortage of supply chain for personal and protective equipment (ppe) arising from coronavirus disease (covid19) pandemic – case study from the republic of ireland date: 2020-07-10 journal: sci total environ doi: 10.1016/j.scitotenv.2020.138532 sha: doc_id: 256112 cord_uid: zg63v8hh coronavirus (covid-19) is highly infectious agent that causes fatal respiratory illnesses, which is of great global public health concern. currently, there is no effective vaccine for tackling this covid19 pandemic where disease countermeasures rely upon preventing or slowing person-to-person transmission. specifically, there is increasing efforts to prevent or reduce transmission to front-line healthcare workers (hcw). however, there is growing international concern regarding the shortage in supply chain of critical one-time-use personal and protective equipment (ppe). ppe are heat sensitive and are not, by their manufacturer's design, intended for reprocessing. most conventional sterilization technologies used in hospitals, or in terminal medical device sterilization providers, cannot effectively reprocess ppe due to the nature and severity of sterilization modalities. contingency planning for ppe stock shortage is important. solutions in the republic of ireland include use of smart communication channels to improve supply chain, bespoke production of ppe to meets gaps, along with least preferred option, use of sterilization or high-level disinfection for ppe reprocessing. reprocessing ppe must consider material composition, functionality post treatment, along with appropriate disinfection. following original manufacturer of ppe and regulatory guidance is important. technologies deployed in the us, and for deployment in the republic of ireland, are eco-friendly, namely vaporised hydrogen peroxide (vh2o2), such as for filtering facepiece respirators and uv irradiation and high-level liquid disinfection (actichlor+) is also been pursed in ireland. safeguarding supply chain of ppe will sustain vital healthcare provision and will help reduce mortality. • there is pressing need to find solutions for reprocessing of ppe for covid19 • reprocessing of ppe is challenging as made for one-time-use • most sterilization technologies are not suitable for ppe reprocessing • use of vaporised hydrogen peroxide and uv irradiation may prove effective for ppe a b s t r a c t a r t i c l e i n f o coronaviruses (covs) (order nidovirales, family coronaviridae, subfamily coronavirinae) are enveloped viruses with a positive sense, single-stranded rna genome (schoeman and fielding, 2019) . with genome sizes ranging from 26 to 32 kilobases (kb) in length, covs have the largest genomes for rna viruses. coronavirus is one of the major pathogens that primarily targets the human respiratory system (rothan and byrareddy, 2020) . previous outbreaks of coronaviruses (covs) include the severe acute respiratory syndrome (sars)-cov and the middle east respiratory syndrome (mers)-cov that are a great public health threat (carty and dinicolantonio, 2020) . a global pandemic status has been recently declared by the world health organization (who) for covid19. the first number of cases were identified in wuhan, a large city of 11 million people in central china in december 2019, which were linked to the huanan (southern china) seafood wholesale market (rothan and byrareddy, 2020) . these were identified by local hospitals using a surveillance mechanism for "pneumonia of unknown etiology", which was established in the wake of the 2003 severe acute respiratory syndrome (sars) outbreak with the aim of allowing timely identification of novel pathogens such as 2019-ncov (li et al., 2020) . globally, the number of confirmed cases as of this writing (3 april 2020) has reached 1,000,249 including 51,515 deaths (https://www.ecdc.europa.eu/en/geographical-distribution-2019ncov-cases) (fig. 1 ). covid19 is now globally distributed (fig. 2) , suggesting that universal solutions are required to prevent or slowdown its rapid spread until effective control measures are developed and deployed, such as vaccine (fig. 3) . covid19 is much more lethal than the typical flu, where former has a mortality rate of about 2.92% (carty and dinicolantonio, 2020) . the annual flu has a mortality rate of just 0.05 to 0.1%, inferring that covid-19 is around 30 to 60 times more lethal (carty and dinicolantonio, 2020) . covid19 causes an inflammatory storm in the lungs and it is this inflammatory storm that leads to acute respiratory distress, organ failure, and death. swaminathan et al. (2007) previously considered that while a new influenza pandemic may appear inevitable, critical parameters of transmissibility and attack rate are uncertain. these authors reported that estimates based on extrapolations from the 3 influenza pandemics of the 20th century suggest that healthcare facilities in the united states alone may be required to cope with 314,000-734,000 additional hospitalizations and 18-42 million outpatient visits (meltzer et al., 1999) . during the early containment phase of a pandemic, patients with suspected infection are likely to be referred to hospitals for isolation, diagnosis, and treatment until the transmissibility and virulence of the pandemic strain are known. although social distancing and school closures may reduce risk in the wider community, healthcare workers (hcws) are likely to encounter repeated close exposures. swaminathan et al. (2007) suggested that if hospitals are to continue to function adequately, reliable access to effective personal protective equipment (ppe; gowns, n95 masks, gloves, and eye protection) and antiviral drug therapy will be necessary for an unpredictable period. with awareness of the recent severe acute respiratory syndrome (sars) outbreak and with growing concern about human deaths from avian influenza (h5n1), governments worldwide have begun to stockpile ppe and antiviral medication. key strategies to control the speed and extent of viral spread within healthcare settings have been advocated by national government guidelines and the who (swaminathan et al. (2007) . these include rigorous infection control practices, prescriptive instructions for the use of ppe, and dissemination of antiviral medication. these authors reported that information regarding the required quantity and rate of use of these valuable resources in an outbreak situation is lacking, thereby limiting valid assessments of the adequacy of current stockpiles. this was corroborated by a previous simulation study conducted by mitchell et al. (2012) , where a patient with suspected avian or pandemic influenza (api) sought treatment at 9 australian hospital emergency departments where patient-staff interactions during the first 6 h of hospitalization were observed. based on world health organization definitions and guidelines, the mean number of "close contacts" of the patient was 12.3 (range 6-17; 85% hcws); mean "exposures" were 19.3 (range 15-26). overall, 20-25 ppe sets were required per patient, with variable hcw compliance for wearing these items (93% n95 masks, 77% gowns, 83% gloves, and 73% eye protection). these data indicate that many current national stockpiles of ppe and antiviral medication are likely inadequate for a pandemic. at this time of writing, in the republic of ireland, there is a national lockdown imposed by the irish government where citizens are requested to remain at home to prevent the spread of covid-19 infection. where new positive covid19 cases arise, the role of contact tracing and data analytics are important. social distancing and cocooning of the elderly and vulnerable groups has been adapted. only essential services, such as agriculture and fisheries, manufacturing and healthcare, have been granted permission to travel. there is a concerted effort to slow the rate of infection so as align with capacity of healthcare to meet fig. 1 . distribution of covid19 worldwide, as of 3 april, 2020. (source https://www.ecdc.europa.eu/en/geographical-distribution-2019-ncov-cases) number of cases, thus avoiding a mismatch in early peak in infections (fig. 3) . given need for react quickly, solutions (where appropriate) are based upon adaptation, blending and re-purposing of existing products, processes, technologies and infrastructures. solutions and challenges to address shortage of ppe in a regional irish hospital are described. use of smart software and networking with various distribution channels to meet shortfall in ppe and infection prevention and control (ipc) methods. a new team of experts was formed (designated rea-ppe) to deploy effective solutions in a short time frame, which included those from across academia, healthcare, enterprise ireland-funded technology gateways, science-foundation-ireland (sfi)-funded research centres (curam for medical device, command for software) and industry. rea_ppe team also links with the crisis management team in the regional hospital where solutions is to implemented by manager of the hospital sterile services department (hssd). this rea_ppe team comprises experts representative of anaesthesia and intensive care, medical device technology, infection control, hospital disinfection and sterilization, minimal processing; microbiology, toxicology, virology, material science, software engineering, and social marketing priority initially focused on delineating effective communication channels in order to inform stocks within healthcare from several routes that include use of dedicated webpage [https: //covidmedsupply.org/] established by researchers from nui galway and university of limerick (ireland) that collects donations of ppe from regional industries and academic institutions. given volatility in the global supply chain for ppe, ireland's health service executive (hse) actively purse ppe orders from china and other sources to meet specific requirements that are quality checked on arrival. upon arrival, ppe are distributed to primary healthcare, stepback healthcare facilities or nursing homes. hcw arededicated to one site to avoid risk of cross-infection. aer lingus (ireland's main national airline), made no-stop flights with a team of volunteer rotating pilots to china in order to collect vital ppe stock, where this process was repeated several times in the same week. covid19 pandemic caused uncertainty to the established norm that is addressed by teamwork, learning, adaptation and adjustment. stock usage will also be tracked through a new ppe mobile phone app that uses (1) backend database to save all information on ppe stock and distribution running on a cloud, such as aws, (2) webserver as a gateway between the mobile app and the database, such as aws, and (3) two functions for updating the database with latest ppe status along with querying the same database. provision has been made for use of smart blockchain system to replace the database, if the system becomes too complicated for mobile phone usage, such as data immutability, where possible, where there was identified shortages in ppe, bespoke production occurred to make these items using medical grade materials, such as continuous positive airway pressure (cpap) helmets for use in intensive care. cpap provides the maximal amount of mean airway pressure without intubation and promotes a more lungprotective ventilation pattern. various other bespoke manufacturing initiatives have commenced in ireland linked to international collaborators that included use of crowdfunding by group of researchers and scientists who raised €134,000 in order to develop an easy-to-build and inexpensive ventilator for covid-19 patients with first prototype now in place (https://www.thejournal.ie/emergency-ventilators-irishresearchers-crowdfund-5061521-mar2020/). other irish researchers in university college dublin and it sligo made easy-to-assemble ventilators using 3d printers and off-the-shelf components that will be validated by ireland's hse (https://www.irishtimes.com/business/ health-pharma/irish-project-for-easy-to-assemble-covid-19-ventilatorsbears-fruit-1.4205999). facial visors were also made using 3-d printers for use in regional hospitals and nursing homes. at the time of writing, it is uncertain as to what if not all bespoke manufactured ppe in ireland that will be inspected by hse before deployment and usage by frontline healthcare workers. the trend by many medical device manufacturers and academic institutions to redeploy expertise and resources to make ppe to address covid19 crisis is also emerging in other international countries (https://www.cam.ac.uk/business-and-enterprise/help-ustackle-covid-19). at this time of writing, there is a dearth in published literature on efficacy of innovations for reprocessing ppe. this is due to fact that ppe are manufactured for single use. threfore, there is reliance on information generated by medical device manufacturers and related sterilization industries to help understand how best to address this shortage of ppe and the need for reprocessing in a pandemic. traditionally, limited knowledge sharing occurs in the medical technology sector due to the need to protect ipr, which is is understandable given nature of commerce and competitiveness. however, there is an increasing trend by leading industries to publish findings that also assists in shaping iso standards, guidelines and regulations with a focus on future-proofing, greater resource utilization and sustainability (mcevoy and rowan, 2019; chen et al., 2019) . original equipment manufacturers (oems) of one-time-use ppe have recently provided new information on possible methods for reprocessing these items given the universal need to consider contingency plans arising from shortages during this pandemic (such as 3m science of life, 2020). ppe used in healthcare includes gloves, aprons, long sleeved gowns, goggles, fluid-repellent surgical masks, eye, nose and mouth protection, face visors and respirator masks. healthcare workers should wear protective clothing when there is a risk of contact with blood, body fluids, secretions and excretions. hcw should select the appropriate ppe based on a risk assessment of the task to be carried out (table 1) . there is particular focus airborne droplets (splatter) liberated through breathing or expelled through sneezing of infected covid19 patients may travel several meters and remain suspended for ca 30 min and survive on surfaces for potentially several days. surface, or contact surface, disinfection or sterilization of ppe will suffice, as coronavirus does not penetrate materials. however, greatest challenge to reprocessing on one-time-use ppe relates to ensuring material functionality post effective treatments. if one considers medical equipment designed for pre-processing, such as endoscope, there is pre-cleaning stage to reduce bioburden in advance of sterilization processes to ensure efficacy. this is relevant as unlike therapeutics (such as vaccines and antibiotics) that rely on a specific mechanistic target for model of action, sterilization modalities are non-specific with reliance upon ensuring that processes run full cycles for achieving sterility assurance level (sal) of products (mcevoy and rowan, 2019). for example, the presence of organic matter may affect the oxidative nature of the gas sterilization process, vaporised hydrogen peroxide (vh2o2). pre-cleaning presents an issue in hospitals as there is commensurate need to decontaminate equipment used in this process for covid19. onsideration was given to use of actichlor plus as a wash/disinfection phase. to prevent the spread of health-care-associated infections, all heat-sensitive endoscopes (e.g., gastrointestinal endoscopes, bronchoscopes, nasopharygoscopes) must be properly cleaned and, at a minimum, subjected to high-level disinfection after each use. high-level disinfection can be expected to destroy all microorganisms, although when high numbers of bacterial spores are present, a few spores might survive (cdc, 2008) . the medical device industry replies upon significant lethality of predetermined populations of a biological indicator (bi) that is typically a recalcitrant bacterial endospore (such as geobacillus stearothermophilus or bacillus atrophaeus). these bis are carefully selected for this purpose as they are more resistant to that of pathogenic microorganisms including covid19, which are typically orders of magnitude more sensitive to same applied lethal stress (fig. 4) . these are a highly validated and controlled sterilization processes. however, sal for these sterilization are endpoint-determination processes that rely upon 12 log reduction in bis that is excessive duration of treatment for reprocessing single-use ppe (fig. 5 ) (mcevoy and rowan, 2019) . there has been no reported cases of patient illness arising from a terminal sterilization of medical devices. furthermore, sterilization technologies are validated for full treatment regimes. there is an absence of publish knowledge as to the efficacy of operating same sterilization modalities under reduced exposure or cycle conditions, such as for the treatment of ppe. therefore, use of penetration technologies such as gamma, electron-beam and x-ray will not be appropriate as likely to affect material and functionality of ppe post treatments. gas-plasma generated hydrogen peroxide vapour will also be unsuitable as the plasma-process affects materials during treatment. steris ast have commenced studies on the combined use of real-time flow cytometry with conventional culture-based enumeration methods that will elucidate this gap, which includes frontier microbial inactivation kinetic modelling. kinetic modelling is important for informing changes in technologies, even for potential disruption potential in emerging innovations, such as in adjacent food industry . this pandemic situation will also present emerging minimal treatment opportunities for materials and treatments in medtech and sterilization industries, which will require greater flexibility in approach, such as for in situ 3d printing of medical devices in healthcare. future reduction in sterilization modality usage would also improve resource utilization and facilitate greater sustainability of the industries. this would also have significant knock-on influence for treated products, with quicker turn-around supply time to clients. however, it is essential that future reductions in sterilization processes are informed by best evidence and do not compromise on product safety, which require validation and regulatory approval before usage. it is appreciated that under pandemic situations, there is a need to do things differently, along with urgency. however, this must be measured, appropriate and best informed by critical information such as that supplied by original manufacturers of single-use devices (such as 3m announcement, 2020), along with international standards and regulators, such as aami and the fda. there is a gap in knowledge on extensive studies relating to reprocessing by this source too. 3m™ stated that "filtering facepiece respirators (ffrs), such as n95, ffp2, kn95, and similar are commonly used to help provide respiratory protection in a variety of workplaces, including healthcare settings. 3m™ reiterated that a common infection prevention practice employed by healthcare organizations is to utilize ffrs as one-time-use items when worn in the presence of infected patients. in the face of a global pandemic, associated ffr shortage, and based on currently available data, 3m™ does not recommend or support attempts to sanitize, disinfect, or sterilize 3m™ ffrs" (3m announcement, 2020). 3m™ reiterated the importance that such reprocessing methods do not compromise the respirator's filtration performance or the ability of the respirator to seal to the wearer's face as intended. albeit conducting additional research, 3m did not recommend or support any specific ffr disinfection method at this time (3m science of life, 2020). however, 3m™ noted that the u.s. centers for disease control and prevention (cdc) has published guidance on managing respirators during pandemics including the reuse and extended use of respirators at: https://www.cdc.gov/ niosh/topics/hcwcontrols/recommendedguidanceextuse.html what potential options are available for reprocessing of ppe to address shortage of supply chain arising from this coronavirus disease (covid19) pandemic? the contingency approach to be adapted by rea_ppe team in ireland will make provision for the deployment of vaporised hydrogen peroxide, such as for ffrs, on site at or near the hospital. this approach is to align with columbus-based battelle process, where it has been reported that up to10,000 n95 masks will be sterilized by vh2o2 in the united states, which has been authorised by the food and drug administration (fda, 2020a; fda, 2020b). final report for the bioquell hydrogen peroxide vapour decontamination for reuse of n95 respirators is available at fda (2020a). the fda (2020b) also released details on enforcement policy for face-masks and respirators during the coronavirus disease (covid19) public health emergency (revised april 2020)guidelines for industry and food and drug administration staff. these are important documents to inform reprocessing of ppe. this battelle approach involves filling a room or enclosed environment (up to 200m 3 ) with vh2o2 for the treatment of ppe. vh2o2 is an emerging technology for the medical device sterilization industry where its application, opportunities and discussed limitations by mcevoy and rowan (2019). vh2o2 technology is operative in united states now at steris ast. however, there is also a pressing need for rapid turn-around for reprocessed ppe on site in the hospitals, such as for critical support in icu. vhp has potentially additional benefits over use of eto (which currently sterilizes ca. 50% of medical devices globally) as it is safer and environmentally acceptable from a future sustainability perspective. use of gamma irradiation and eto constitutes ca. 95% of the terminal sterilization market (mcevoy and rowan, 2019). vh2o2 has great promise, but exhibits limitations such as against cellulose-based medical materials whereas eto has broad material compatability (mcevoy and rowan, 2019) . there is still uncertainty as to ensuring safe distribution of contaminated ppe for external contract vh2o2 sterilization services for treatment that negates reprocessing of ppe at plant level. the rappe team have placed an order for bq50 hpv system, similar to what is been deployed in the us. strict procurement rules on purchasing of assets over €25 k were relaxed to enable rapid uptake of technologies during this pandemic. recent studies supports that rna viruses, including coronavirus, are highly susceptible to hydrogen peroxide exposure where significant lethality is achieved with 0.5% hydrogen peroxide (a fraction to what is used in standard contact lens disinfection) in b1 min on glass. studies recently reported from china have also revealed that introducing hydrogen peroxide inhalation may improve covid19 patient outcomes (http://www.adledlight.com/news_show34.html). reappe contingency plan also includes provision for deploying uv-c at 254 nm (nanoclave cabinet, ireland) and broad-spectrum pulsed light (claranor, france) technologies for high-level disinfection of ppe. uv-c technology is a very effective technology for disinfection and used extensively by adjacent food and water industries. given that coronavirus (cov) and other respiratory viruses are significantly less resistant to that of bis used in sterilization modalities, the use of high to moderate-level disinfection is conceivable sufficient to meet needs for reprocessing of ppe (fig. 3) . these are also turnkey commercial technologies for ease of operation and integration within hospitals that also considers usage by existing decontamination staff and by the manager of hssd. efficacy of uv-irradiation technology is governed by the applied uv dose or fluence (w/m 2 ) and is affected by shading where it only inactivates what it irradiatesthus, ppe will need to be turned during treatments (rowan, 2019) . nanoclave chamber has 32 × 30 w and 16 × 25 w sylvania uvgi lamps that delivers a uv-c dose of 52 w/m 2 for 60s. nanoclave cabinet was shown to disinfect 3-log viral unit of adenovirus in 3 min at fixed wavelength of 254 nn that targets vital genetic material, such as rna (moore et al., 2012) . high intensity, pulsed uv technology (puv) uses broad spectrum pulsed light that is delivered at ca. 50,000 times the intensity of sunlight at contact surface where treatment time is exceptionally short duration, mere seconds (farrell et al., 2011; barrett et al., 2016) . previous researchers have demonstrated efficacy for extensive range of pathogens, but puv also affected by shading rowan, 2019) . puv is currently been used for high-throughput food packaging disinfection commercially (rowan, 2019) . puv has also been shown to be more effective and environmentally-friendly as a surface disinfection system compared with other minimal processing technologies tested, such as pulsedplasma gas-discharge that produced short-lived oxidising biocidal water (hayes et al., 2013; garvey et al., 2015) . there has been limited studies on use of uv-disinfection technology for ppe treatment. 3m™ recently referred to a previously published study by bergman et al. (2010) where these authors evaluated a multiple (3-cycle) decontamination processing for filtering facepiece respirators (ffrs) (3m science of life, 2020). the uv-germincidal-irradiation (uvgi) method described was operated for 30 min at 254 nm (15-min per side) for 3m™ 1860 and 1870 ffrs where straps on 1870 lost elasticity with a strong burning odour, and the nosefoam compressed on 1860 ffr model. this study did not assess the efficiency of disinfection method to inactivate microorganisms where it would be relevant to report on uv dose over treatment regime. prolonged and excessive exposure using low-pressure uv light source can produce significant thermal effects along with material damage over repeated use. bergman et al. (2010) also reported on the use various other unknown ffr makes and models and reported no observable physical change using same (1) uvgi for 15 min at 254 nm using one side of ffr facing lamp with strap removed, (2) ethylene oxide for 1 h in 100% eto sterilizer, and (3) vhp treatment for 15 min dewell, 125 min total cycle at 8 g/m 3 concentration. however, it is also unclear as to what specific ffr models were used and functionality post treatments. fisher and shaffer (2011) reported on the development of a method to assess modelspecific parameters for ultraviolet-c (uv-c, 254 nm) decontamination of filtering facepiece respirators (ffrs). uv-c transmittance was quantified for the distinct composite layers of six n95 ffr models and used to calculate model-specific α-values, the percentage of the surface uv-c irradiance available for the internal filtering medium (ifm). circular coupons, excised from the ffrs, were exposed to aerosolized particles containing ms2 coliphage and treated with ifm-specific uv-c doses ranging from 38 to 4707 j/m 2 . models exposed to a minimum ifm dose of 1000 j/m 2 demonstrated at least a 3 log reduction in viable ms2. model-specific exposure times to achieve this ifm dose ranged from 2 to 266 min. overall, fisher and shaffer (2011) found uv-c transmits into and through ffr materials. log reduction of ms2 was a function of model-specific ifm uv-c doses. the supply of national institute for occupational safety and health (niosh)-certified n95 filtering facepiece respirators (ffrs) may become limited during an influenza pandemic [institute of medicine (u.s.) committee on the development of reusable facemasks for use during an influenza (cited in fisher and shaffer, 2011) . extending the lifetime of ffrs for multiple uses (e.g. multiple donnings) may help to alleviate the supply demand (viscusi et al., 2007 (viscusi et al., , 2009a (viscusi et al., , 2009b . fisher and shaffer (2011) also advocated that an option that may permit ffr reuse is the decontamination or removal of the infectious material from the ffr through one or more physical or chemical treatments. for this option to be practical, the decontamination treatment must maintain ffr fit and filtration performance and not leave hazardous residues. other desired attributes for a decontamination method for ffr reuse would be low cost, high throughput and ease of use (viscusi et al., 2009b) . uvgi technology has been suggested as a viable option for ffr reprocessing application where nine ffr models were evaluated for changes in physical appearance, odour and laboratory performance (filter aerosol penetration and filter airflow resistance) following simulated decontamination using five different methods, including uvgi (viscusi et al., 2009b) . in latter study, uv-c treatment did not affect the filter aerosol penetration, filter airflow resistance or physical appearance of the ffrs. uv-c, as a decontamination method, is affected by several parameters, including the topography of the contaminated surface and the location of the microorganisms within the substrate. the use of uv-c for surfaces is mainly for hard, nonporous substrates (fisher and shaffer, 2011) . therefore, at this time of writing, while uvgi and puv methods appear promising, no validated decontamination methods for ffrs exist. lessons can also be gleamed from best-published information and hurdles arising from minimal processing technologies that have been exploited by the food industry for commercial applications (deng et al., 2019) . these technologies rely upon reduced severity of nonthermal treatments that equate to moderate of high-level decontamination gerard et al., 2019) . however, review of bestpublished approaches suggest that these technologies, in their current configurations, would not be suited for ppe reprocessing. these unsuitable technologies include high hydrostatic pressure, pulsed electric fields, pulsed-plasma gas-discharge, ultrsound and so forth (deng et al., 2019) . also, the majority of chemical biocides deployed in the food industry as liquid decontaminants for surface-treatments would not be effective for ppe as these cannot be easily used in the hospital setting. however, kampf et al. (2020) recently reported that coronaviruses persist on inanimate surfaces, such as glass, plastic and metal for up to 9 days, but they are efficiently inactivated on these surfaces with use of 62-72% alcohol, 0.5% hydrogen peroxide, or 0.1% sodium hypochlorite within 1 min exposure. use of high level disinfection with actichlor-plus served as both a detergent and biocide for reprocessing starmed hoods used by covid19 patients in icu. testing of starmed hoods in heated washer at 90°c caused damage to the pvc component. high level disinfection was applied in advance of lead-time for vhp and uv technologies arriving to hssd and as use of sodium hypochlorite was suggested as possible approach to cleaning and disinfecting 3m™ powered air purifying respirators following potential exposure to coronaviruses (https://multimedia.3m.com/mws/media/1793956o/ cleaning-and-disinfecting-3m-paprs-following-potential-exposure-tocoronaviruses.pdf). there is potential for use of combined hepa filtration with uv light disinfection for air disinfection in critical areas that will reduce aerobiology or airborne bioburden. however, consideration would need to be given to efficacy of reduction of covid19 or similar respiratory viruses. perceived benefits and future directions for the control of covid19 with a focus on addressing shortages in supply chain. the perceived indicative benefits of deploying solutions for reprocessing ppe to address front-line shortage have listed in terms of making potentially significant qualitative and quantitative difference are listed in table 2 . the world, as we know it, will be a changed place post covid19, where there will be greater focus on mitigation planning for managing pandemics nationally and transnationally with either increased provision and/or less reliance on one-time-use medical devices and ppe. future provision in hospitals and healthcare will also consider duality of sterilization treatments with reduced processing capability for to deliver if required, high or moderate level of disinfection. there will be increased emphasis on convergence of technologies and knowledge from adjacent disciplines, such as the food industry, to improve our understanding of minimal processing linked to sterilization. this will be framed upon increased demand for evidence-based research and shared publications so to inform validation and new regulations using potentially new smart innovations and services or adapting existing modalities. it is envisaged that there will be a commensurate push to promote more eco-innovations, along with review of exiting sterilization processes, for sustainability of resources and to meet existing needs arising and emerging from this covid19 pandemic. this pandemic also highlights the value of converging areas of expertise that will inform education and workforce training processes. this pandemic also highlights that despite staggering advancements in innovation, society is still very vulnerable to global treats to our health from what is a microscopic virus. commensurately, our collective creativity and ingenuity will enables us to countermeasure these challenges. in summary, providing solutions for the shortages in supply chain for one-time-use ppe is extremely complex. preference would always be for usage of single-use items as described by the manufacturers as ensuring the safety of our healthcare workers is paramount. logical first step solutions would be to improve communication lines for better stock management of ppe that exploits webpage and mobile phone app development along with dual bespoke production of ppe using medical grade materials where gaps are identified, such as ventilators. however, a pandemic foists untold and unexpected demands on society that includes provision or contingency planning for reprocessing ppe. under such situations, it is imperative to follow closely advice from original manufacturer of ppe on material composition and design features with view to making reprocessed ppe (where possible), fit for purpose. this also includes adhering to close advice provided by regulators, such as fda. the majority of existing in house hospital, external terminal sterilization and adjacent minimal processing technologies (as used in food industry) will not be effective for reprocessing ppe. however, review of best evidence suggest that preferred candidate methods for meeting this gap appears to be use of vaporised hydrogen peroxide (vhp) and uv irradiation technologies, which are likely be deployed in the republic of ireland. science foundation ireland -rapid covid19 fund grant with curam edical device centre. nr and jgl conceptualised the manuscript. nr drafted the manuscript. both authors read, edited, and approved the final manuscript. not applicable. the authors declare that they have no competing or conflict of interests. disinfection of filtering facepiece respirators detection, fate and inactivation of pathogenic norovirus employing settlement and uv treatment in wastewater treatment facilities evaluation of multiple (3-cycle) decontamination processing for filtering facepiece respirators nutraceuticals have potential for boosting the type 1 interferon response to rna viruses including influenza and coronavirus 3d printed polymers are less stable than injected moulded counterparts when exposed to terminal sterilization processing using novel vaporized hydrogen peroxide and electron beam processes emerging chemical and physical disinfection technologies of fruits and vegetables: a comprehensive review studies on the relationship between pulsed uv light irradiation and the simultaneous occurrence of molecular and cellular damage in clinically-relevant candida albicans final report for the bioquell hydrogen peroxide vapor (hpv) decontamination for reuse of n95 respirators enforcement policy for face masks and respirators during the cornovirus disease (covid19) public health emergency (revised) a method to determine the available 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of the 2009 influenza a (h1n1) pandemic on canadian health care workers: a survey on vaccination, illness, absenteeism, and personal protective equipment use of uvc radiation for disinfecting non-critical patient care items -a laboratory assessment of the nanoclave cabinet the epidemiology and pathogenesis of coronavirus disease (covid-19) outbreak pulsed light as an emerging technology to cause disruption for food and adjacent industries -quo vadis? a review of quantitative methods to describe efficacy of pulsed light generated inactivation data that embraces the occurrence of viable but non culturable state microorganisms coronavirus envelope protein -current knowledge personal and protective equipment and antiviral drug use during hospitalization for suspected avian or pandemic influenza disinfection of healthcare equipment -guideline for disinfection and sterilization in healthcare facilities effect of decontamination on the filtration efficiency of two filtering facepiece respirator models evaluation of the filtration performance of 21 n95 filtering face piece respirators after prolonged storage evaluation of five decontamination methods for filtering facepiece respirators decontamination, disinfection, and sterilisation the authors would like to thank dr. emma murphy for assisting with graphics editing of figures. key: cord-269423-p73bszlq authors: zhao, fei; liu, cheng; cai, zhaonan; liu, xiong; bak, juseon; kim, jae; hu, qihou; xia, congzi; zhang, chengxin; sun, youwen; wang, wei; liu, jianguo title: ozone profile retrievals from tropomi: implication for the variation of tropospheric ozone during the outbreak of covid-19 in china date: 2020-10-13 journal: sci total environ doi: 10.1016/j.scitotenv.2020.142886 sha: doc_id: 269423 cord_uid: p73bszlq during the outbreak of the coronavirus disease 2019 (covid-19) in china in january and february 2020, production and living activities were drastically reduced to impede the spread of the virus, which also caused a strong reduction of the emission of primary pollutants. however, as a major species of secondary air pollutant, tropospheric ozone did not reduce synchronously, but instead rose in some region. furthermore, higher concentrations of ozone may potentially promote the rates of covid-19 infections, causing extra risk to human health. thus, the variation of ozone should be evaluated widely. this paper presents ozone profiles and tropospheric ozone columns from ultraviolet radiances detected by tropoospheric monitoring instrument (tropomi) onboard sentinel 5 precursor (s5p) satellite based on the principle of optimal estimation method. we compare our tropomi retrievals with global ozonesonde observations, fourier transform spectrometry (fts) observation at hefei (117.17°e, 31.7°n) and global positioning system (gps) ozonesonde sensor (gpso3) ozonesonde profiles at beijing (116.46°e, 39.80°n). the integrated tropospheric ozone column (toc) and stratospheric ozone column (soc) show excellent agreement with validation data. we use the retrieved toc combining with tropospheric vertical column density (tvcd) of no2 and hcho from tropomi to assess the changes of tropospheric ozone during the outbreak of covid-19 in china. although no2 tvcd decreased by 63%, the retrieved toc over east china increase by 10% from the 20-day averaged before the lockdown on january 23, 2020 to 20-day averaged after it. because the production of ozone in winter is controlled by volatile organic compounds (vocs) indicated by monitored hcho, which did not present evident change during the lockdown, the production of ozone did not decrease significantly. besides, the decrease of nox emission weakened the titration of ozone, causing an increase of ozone. in early 2020, a novel coronavirus sarscov-2 (covid-19) emerged in the city of wuhan, china, and has spread all over the world by march 2020 (world health organization, 2020) . to curb the transmission of covid-19 in china, many policy interventions, such as the travel restrictions, the shutdown of factories and halting mass transportation, have been implemented by the chinese government, which was marked by the lockdown of wuhan on january 23, 2020. these measures have also caused a great impact on the environment (wang and su, 2020; xu et al., 2020; zambrano-monserrate et al., 2020) . many previous researches indicate that the concentrations of primary air pollutants, such as like no 2 , so 2 , have sharply reduced due to large decrease of emissions . however, the changes of secondary pollutants like secondary aerosol and ozone were various, and their concentrations in some cities even increased due to the change of chemical reactions (chinazzi et al., 2020; le et al., 2020; shi and brasseur, 2020) . ozone has different effects at different altitudes in the atmosphere. most of the ozone distributed in the stratosphere can absorb strong ultraviolet radiation that can cause health problems in humans (bell et al., 2004; norval et al., 2007; su et al., 2017; nuvolone et al., 2018; zhang et al., 2020) . a small amount of ozone in the troposphere, which is mainly produced from the photochemical reaction between volatile organic compounds (vocs) and nitrogen dioxides (no x ) (littman and magill, 1953; sillman, 1995) , shows harmful effects to humans. therefore, the vertical distribution of ozone is very important for us to understand the physicochemical process of ozone. especially, zoran j o u r n a l p r e -p r o o f journal pre-proof 3 et al. (2020) found that ambient ozone may increase the covid-19 infections, in addition to direct harm to human health. however, previous studies were all confined in the scale of city. spatial distribution of ozone on regional and national scales should be obtained due to complex ozone chemistry in different regions. satellite-based remote sensing can monitor several species of trace constituents in the atmosphere on the global scale, which is an ideal means to analyse the spatio-temporal distribution of air pollutants. total ozone column has been measured using backscattered uv radiation since 1970 with instruments like backscatter ultraviolet (buv) and solar backscatter ultra violet (sbuv) instruments (bhartia et al., 1996) , as well as since 1995 by the global ozone monitoring experiment (gome) (hoogen et al., 1999) ). the sbuv make ~ 10 monochromatic measurements at the spectral resolution of ~ 1.0 nm. therefore, the profile information is limited to the stratosphere with sbuv and the tropospheric column ozone is estimated using residual-based methods with a lot of approximations. the gome first measures the full uv/vis spectrum with a moderate spectral resolution of 0.2-0.4 nm and ozone profile retrievals down to the troposphere have been implemented (van der a et al., 2002; liu et al., 2005) . ozone monitoring instrument (omi) on aboard the eos aura spacecraft, gome-2 aboard the metop and ozone mapping and profiler suite (omps) aboard the suomi national polar-orbiting partnership (snpp) continued observation of atmospheric ozone as successors of gome (dirksen et al., 2006; seftor et al., 2014) . ozone profiles retrieved from omi has been extensively validated using ground-based data (huang et al., 2017a; xing et al., 2017; zhang et al., 2019) and satellite data (liu et al., 2010a; huang et al., 2017b; su et al., 2017) . the omi instrument provides a favorable opportunity to contribute to the understanding of chemical and physical functions especially in the troposphere due to its high spatial resolution (13 km along the track × 24 km across the track at nadir). however, since the occurrence of omi row anomaly in 2007 and worsened in 2009, a portion of cross-track positions have been affected and the data from these positions can no longer be used for scientific research (huang et al., 2017a) . the omps is designed to measure total column and stratospheric ozone profile with spatial resolution of 50 x 50 km 2 , but bak et al. (2017) retrieves the tropospheric column ozone with careful measurement calibration in spite of insufficient spectral information. tropomi, which is the only payload of sentinel-5 precursor mission, was launched on 13 october 2017. the tropomi works on a 817 km sun-synchronous polar orbit with a mean local solar time of 13:30 at ascending node (veefkind et al., 2012) . tropomi has a similar instrument concept to omi but has higher spatial resolutions and extend spectral range than those of omi. details on tropomi instrument parameters are discussed in later sections. the purpose of this paper is to describe the inversion algorithm of tropomi ozone profile and validate the results using various in-situ measurements as well as satellite data, which is further used to evaluate the variation of tropospheric ozone in different regions in china. to the best of our knowledge, tropomi ozone profiles have not been published in the literature. for this purpose, we adopt an optimal estimation based the algorithm which has been implemented for gome, gome-2, omi and omps instruments (liu et al., 2010b; cai et al., 2012; bak et al., 2017) . accurate forward model simulation, absolute wavelength/radiometric calibration and good knowledge of a priori are essential for ozone profile retrievals. the adopted algorithm needs to be modified for tropomi, mainly with respect to the fitting windows, instrument slit function, wavelength/radiometric correction. therefore, to improve the fitting accuracy, we thoroughly characterize the radiometric calibration spectrum from the comparison between simulated and measured radiances. we present a validation of the retrievals including ozone profile, soc and toc. this paper proceeds as follows: section 2 introduces the retrieval algorithm and tropomi l1b data, description of the forward model, retrieval scheme and examination of different slit function impacts on the reduction of fitting residuals and radiometric calibration and evaluate the effect of soft calibration by comparison of spectral fitting residuals with and without correction at all latitudes. in section 3, we talk about retrieval characterization. the validation results of retrievals are discussed in section 4, the impact of covid-19 on tropospheric ozone are discussed in section 5 and conclusions are described in section 6. the s-5p is a polar orbiting satellite, which was launched on 13 october 2017. the s-5p will fill the gap between the end of omi and the sentinel-5 mission. the tropomi is the only payload of the s-5p (veefkind et al., 2012) . there are four different spectrometers, each with its own optics and detector: medium-wave uv, longwave uv combined with visible (uvis), nir, and swir (kleipool et al., 2018) . tropomi is a double channel push-broom imaging spectrometer measuring radiance and irradiance in the ultraviolet (band-1: 267-300 nm, band-2: 300-332 nm), visible (band-3: 305-400 nm, band-4: 400-499 nm), near-infrared (band-5: 661-725 nm, band-6:725-786 nm), and the shortwave infrared (band-7: 2300-2343 nm, band-8: 2343-2389 nm) that provide daily global trace gases concentration information. the spectral resolution varies from 0.5 nm in uv, uvis, and nir bands, to 0.23 nm in swir band. ozone profile information is contained in band 1-3 measurements. but we found that band-1 radiances have opposite systematic biases between tropics and mid/high j o u r n a l p r e -p r o o f journal pre-proof 5 latitudes and band-2 noise is larger than band-3 (fig. 2) . therefore, we retrieve ozone profile using optimal estimation technique from the band-3 (314-340 nm) where typical resolution is 0.54 nm. tropomi has a wide field-of-view (108º) across the track and a small field-of-view along the track and the instantaneous swath width is 2600 km at the earth's surface. there are 450 cross-track positions used for spatial coverage and hence a smaller pixel size of 7 km (along the track, now reduced to 5.5 km) × 3.5 km (across the track) is acquired compared to its precursors omi and omps. tropomi is commanded to perform a solar irradiance measurement every 15 orbits. if no solar measurements are available in the data granule being processed, no irradiance product will be generated. the solar irradiance measurement follows the same binning scheme as the earth radiance measurements. the impact of the reflectance degradation on retrieved ozone profiles is shown to be large . the comprehensive long-term analysis of the reflectance degradation for tropomi shows that the irradiance degrades 5 % around 314 nm and by 2 % around 340 nm from april 2018 through april 2019. however, we found that the reflectance changes less over time by comparing with soft calibration spectrum (more details in section 3) of different months in 2018. therefore, the radiance shows similar attenuation and long-term changes as the irradiance and we use the daily solar irradiances to normalize the earthshine radiances. the omps-lp ozone product measures the vertical distribution of ozone in the stratosphere and lower mesosphere. the algorithm derives ozone profile values along with errors in the uv from 29.5 km and 52.5 km, and in the visible from 12.5 km to 37.5 km (deland, 2017) . the fts observation station, located in hefei city in central-eastern china, has continuously measured ozone profile since april 2014. thus it is significant to validate the retrieved profile in this region. the precision of the tropospheric ozone column (0-12 km) is approximately ~3 % and the accuracy is estimated to be ~8 %. a detailed description of the fts station can be see in sun et al. (2018) and tian et al. (2018) . a total of 129 days of data from 1 march 2018 to 1 may 2019 are available. 6 ozonesonde data during 2018-2019 are obtained from the world ozone and ultraviolet data center (woudc, http://www.woudc.org) and the southern hemisphere additional ozonesondes (shadoz, https://tropo.gsfc.nasa.gov/shadoz/) witte et al., 2017; sterling et al., 2018; witte et al., 2018) . ozonesonde data with vertical resolution ~100-150 m and typically 5-10 % accuracy and 3-5% precision have been widely used and validated (huang et al., 2017a; xing et al., 2017; sterling et al., 2018) . the "soft-calibration" spectra can be derived by comparing measured radiance and simulated radiance with "true" atmosphere as an input. following the method proposed by liu et al. (2010b) , the vector linearized discrete ordinate radiative transfer (vlidort) is used to simulate radiances and weighting functions (liu et al., 2005; liu et al., 2010b; cai et al., 2012) . the ring spectrum is directly characterised by a single scattering rrs model has been used in previous ozone profile retrievals (sioris and evans, 2000; liu et al., 2010b; cai et al., 2012) .the radiance is simulated for a rayleigh atmosphere which excludes the effects of water vapor and aerosols. the surface and clouds are assumed to be lambertian equivalent reflections. we treated clouds as a lambertian surfaces at cloud-top with a fixed reflectivity of 80%. we use the independent pixel approximation (ipa) to assume that partial clouds are a mixture of clear and cloudy scene. in the ipa, the cloud-top pressure we used are derived from the tropomi fresco algorithm (coldewey-egbers et al., 2018) . we acquired an initial cloud fraction at 347 nm based on surface albedo derived from the omi surface climatology. high-resolution ozone absorption cross section is determined from brion et al. (1993) according to the recommendation made in liu et al. (2007) and liu et al. (2013) . daily temperature profiles and surface pressures derived from national centers for environmental protection (ncep) final (fnl) operational global reanalysis data (1°×1°) (https://rda.ucar.edu/) are used in our retrievals. table 1 summarizes the vlidort inputs used in simulation. (kleipool et al., 2008) ozone cross sections (brion et al., 1993) a priori ozone profile (bak et al., 2013) j o u r n a l p r e -p r o o f the instrument spectral response function (isrf) has a crucial influence on the high fitting precision. we the retrieval algorithm, that has been applied to gome (liu et al., 2005) , gome-2 , omi (liu et al., 2010b) , and omps (bak et al., 2017) , is based on principle of optimal estimation method (rodgers, 2000) . the algorithm simultaneously minimize the difference between calculated and measured radiances, and between a priori (x a ) and retrieved ( ) state vectors during iteration. the state vectors are constrained by a priori error covariance matrix and measurement error covariance matrix. the cost function and a posteriori solution can be given as: (1) where and +1 are the previous and current state vectors contains the ozone profile and other parameters, respectively. is the measured radiance normalized to the daily solar irradiance; is the radiation transfer model; ( ) is the computed radiances using the radiation transfer model and normalized with ; is the diagonal covariance matrix calculated from the measurement error. is defined as the weighting function matrix, = ⁄ ; partial ozone column densities in 24 layers are divided by 25 pressure levels. the j o u r n a l p r e -p r o o f journal pre-proof 8 state vector consists of 33 parameters, including 24 partial ozone columns, one cloud parameter and three reflectivity parameters. it also includes two wavelength shift parameters, one ring effect scaling parameter, bro and hcho vertical column densities (vcds). table 2 summarize the fitting variables, a priori and corresponding a priori errors. the measurement errors are derived from tropomi level 1b random-noise errors. the a priori ozone profile and a priori error covariance matrix is derived from the ozone climatology calculated based on tropopause that has been use in retrievals by (bak et al., 2013) . it can improve the precision of retrieved ozone profile, especially in the upper troposphere and lower stratosphere (utls). in the omi retrievals, invariable floor noise errors are used as preliminary measurement constraint (liu et al., 2010b) . for tropomi, we directly use the tropomi radiance random-noise errors constrain our retrievals. the high quality of reflectance is required to extract the independent information on the ozone profile, especially for the tropospheric ozone. the reflectance however is strongly affected by instrument performance and pre-launch calibration. similar to omi, 2-dimensional ccd array is used to measure tropomi radiance and irradiance and the ccd detector array is susceptible to systematic wavelength registration errors and cross-j o u r n a l p r e -p r o o f journal pre-proof 9 track dependent biases, which are likely to cause striping in ozone and other trace gas retrievals. to evaluate and eliminate such systematic biases, the "soft calibration," implemented in omi (liu et al., 2010b) , omps (bak et al., 2017) and gome-2 ozone profile retrievals, is also applied to tropomi radiances in this paper. this soft calibration is in general based on the comparison of measured radiances with expected values. the keys to soft calibration are the choice of regions, the a priori profile and the use of daily means. the a priori ozone profile from toa(top of atmosphere)to 215 hpa are derived from the latest version 4 aura microwave limb sounder (mls) instrument (waters et al., 2006) . this version and earlier versions have been extensively validated (liu et al., 2010a; huang et al., 2017b) and been used as a priori profile by liu et al. (2010b) and . we obtain a priori profiles by merging ozone climatology from mcpeters et al. (2007) for pressure greater than 215 hpa with zonal mean mls ozone profiles below 215 hpa. the tropical measurements were typically characterized where ozone change is relatively small (bak et al., 2017) , and cloud-contaminated pixels and extreme viewing-geometries are screened out to reduce the errors in radiative transfer calculation, with the criteria: latitude < 10°n/s, cloud fraction < 0.2, and solar zenith angle < 40°. the correction spectrum is the ratio of measured radiances and simulated radiances. the correction can be written as follows: = where is the measured radiance at wavelength and is the corresponding simulated radiance. in this paper, one day of tropomi measurements on 3 april 2018 is used to characterize ratios of measured to calculated radiances in the spectral range 305-360 nm (band-3) for all cross-track positions (fig.1) . at wavelengths longer than 314 nm, the mean differences steadily decrease from ~10% with fluctuations at 314 nm to a few percent at ~350 nm, and increase sharply at wavelengths below 314 nm to 40-50 %. the standard deviations vary from 0.01-0.5% at wavelengths longer than 346.7 nm to 0.5-9.5% between 305-346 nm. these spectral variations do not change much with cross-track position. therefore, we do not use wavelengths below 314 nm for ozone profile fitting. the cross-track dependent correction spectra shown in fig. 1(a) are applied to tropomi radiances before the fitting starts. fig. 2 (c) and (d) show comparisons of fitting residuals both with and without correction at all latitudes for band-3. before applying the correction spectrum to tropomi radiances, the mean fitting residuals are within 1%, 0.8% and 0.45% for high-latitude, mid-latitude and tropics regions, respectively. the soft calibration remarkably reduces the fitting residuals for all latitudes, especially for tropics and mid-latitudes. fitting residuals are improved to 0.1-0.2 % in the tropics and 0.2-0.4% in the mid-latitudes. however, there are large systematic measurement biases in high latitudes with the fact that the derived soft calibration does not account for the dependence of systematic fitting residuals on the solar zenith angle. therefore, our retrievals are still susceptible to these errors that vary latitudinally and seasonally. to determine the temporal variation of the soft calibration spectra, we derived the correction spectrum every month between april 2018 and december 2018. the mean differences can vary by up to ~2 % at center cross-track position and ~1 % at the edge crosstrack position from month to month, respectively, but the overall structure is similar and there is no noticeable time-dependent degradation. therefore, we do not account for the time dependence in the soft calibration. we also calculate correction spectrum from 300-330 nm of band-2 and 270-330 nm of combination of band-1 and band-2 ( fig. 2 (a), (b) ). however, we found that there are large systematic biases in radiance at wavelength shorter 290 nm and the retrieval residuals in the 314-330 range of band-2 are larger than those of band-3 ( fig.2 (c), (d))). we also compare the retrievals, using spectral in the wavelength range 302.5-330 nm of band-2, with ozonesonde profiles and ground total ozone taken from woudc. the difference of retrieved and ground total column ozone (to) using band-2 spectral are larger than that using band-3. the retrieved profiles in the spectral range 302.5-330 nm show larger positive biases at higher altitudes than those using band-3 (not shown here). journal pre-proof to screen out tropomi data for comparisons, we only use tropomi data under the following conditions: cloud fraction < 30 %, solar zenith angle < 75°. the collocation criteria is similar to that used by huang et al. (2017a) . we first selected tropomi data with cloud fraction < 0.3, a time difference within 6 hours and within ±1° latitude, ±1°longitude from the ground site and then obtain the nearest tropomi pixel for comparison. the ozonesonde profiles are interpolated to the tropomi grid and then tropomi averaging kernels are convolved with the interpolated profile to remove smoothing errors. after filtering out tropomi data that does not meet the above conditions, approximately 120 coincidence pairs are used in the comparison. fig. 5 shows the comparisons of the retrieved, a priori and fts toc with and without tropomi ak. the integrated toc shows good agreement with fts measurements. the a priori toc is much lower than the fts toc with the mean bias of -16.9 du and standard deviation of 12.01 du. the correlation coefficient between fts and a priori toc is we validate tropomi ozone profile, toc and soc retrievals with global ozonesonde data except for in the northern high latitudes from 2018 to 2019. there are no sufficient ozonesonde data for statistical analysis in the northern high latitudes. we only used ozonesonde profiles with correction factors between 0.8 and 1.15. the tropopause pressure derived from tropomi and ozonesonde burst pressure are used to calculate toc and soc. the column concentration integrated from the surface to the tropopause is defined as toc and the soc is defined as the integral of ozone profile from the tropopause pressure to the burst pressure. we selected 5 stations to compare ozone profiles between ozonesondes and the retrieved (fig. 7) . the a priori profiles show a large negative bias, with a maximum negative bias of -80%, below 30 hpa at most stations. tropomi agrees with ozonesonde to within ±5 % from 0.8-30 hpa and within ± 15 % below 30 hpa. tropomi retrievals show significant reduction in mean biases over the climatological profiles below 30 hpa. the retrieved ozone profiles above 20 hpa show worse agreement with ozonesonde than the a priori profile mainly due to not using information below 314 nm. (sterling et al., 2018) . 20-day average of tropomi no 2 (copernicus sentinel-5p (processed by esa), 2018a), hcho (copernicus sentinel-5p (processed by esa), 2018b) tvcd and the retrieved toc before and during the lockdown of wuhan on january 23, 2020 (hereafter referred to as the "pre-lockdown" and "post-lockdown" periods) are shown in fig. 8 . no 2 tvcd over east of china fell by as much as 63 % and hcho tvcd slightly reduced by 6 % from pre-lockdown period to lockdown period, respectively. however, the tropomi toc over east of china increase by 10 % due to the temperature rise and the uncoordinated reduction of no 2 and hcho tvcd. tropospheric ozone is mainly formed through photochemical reactions of nitrogen oxidation (nox=no+no 2 ) indicated by no 2 and volatile organic compounds (vocs) indicted by hcho (sillman, 1995) . however, the interrelations among ozone, nox and vocs are nonlinear. the chemical formation of ozone is controlled by nox or vocs, namely nox-limited or voc-limited regimes, depending upon which substance is inadequate in the reactions (chameides et al., 1992) . because ozone production in the winter in china is usually controlled by vocs, slight decrease of vocs in eastern china may not cause an obvious declining of ozone formation from photochemical reaction (lu et al., 2019) . besides, the decrease of no x emission would reduce the concentration of no, which can titrate ozone in the ambient (li et al., 2016; zou et al., 2019) , causing more accumulation of ozone. especially, in the bth region, the no 2 tvcd sharply reduce by 77% much higher than the average decreasing amplitude in the eastern china; however, hcho tvcd even increased by 18 %. this variation tendency of no x and vocs caused toc in bth region greatly increased by 17 %. the yangtze river delta (yrd) and pearl river delta (prd) regions show similar ozone pollution characteristics to eastern china. the variation of tropospheric ozone in eastern china during the outbreak of covid-19 was evaluated using satellite-based observation. we have adapted and modified the omi ozone profile algorithm to retrieve tropomi ozone profiles. compared to the derived on-orbit isrfs assuming standard gaussian and super gaussian, the pre-flight isrf measurements (tropomi isrfs v3.0.0) is demonstrated as a best representative in term of the spectral fitting accuracy. to eliminate the effect of systematic measurement errors in the tropomi radiances that depend on wavelength and cross-track positions, we apply "soft calibration" to tropomi radiances before the fitting starts. j o u r n a l p r e -p r o o f journal pre-proof 21 after applying the correction spectrum to tropomi, the fitting residuals have been significantly improved for five latitude bands, especially in the tropics and mid latitudes. the fitting residuals reduce by ~71 % and 46 % in the low and middle latitudes, respectively. we have validated our retrievals against fts data and gpso 3 ozonesonde data observations in china between march 2018 and december 2019. the integrated toc shows excellent agreement with fts and gpso 3 toc after the application of tropomi aks, respectively. the comparisons of the retrieved and ozonesondes profiles show that the retrievals have better consistency with the ozonesonde profile than a priori at most of selected stations, especially in the troposphere. however, the mean biases and standard deviations between tropomi and ozonsondes profiles above 20 hpa are larger than those between a priori and ozonesondes profiles partly due to missing information below 314 nm. the retrieved soc show good agreement with ozonesonde data. the validation of integrated toc with applying tropomi aks against ozonesonde shows that tropomi is in very good agreement with ozonesonde within 2.4 du at all latitudes. the correlations are greater than 0.922 except for 0.703 in the tropics partly due to a "drop off" in shadoz data after ~2014. based-on the retrieved toc as well as tcvd of no 2 and hcho from tropomi, we evaluated the change of ozone in the lockdown period during which special measures were conducted to prevent the spread of covid-19 and also caused large decrease of primary pollutant emission. the retrieved toc over east of china increased by 10 % compared with that during the pre-lockdown period, due to the uncoordinated reduction of no 2 and hcho tvcd. in the bth region, the no 2 tvcd sharply reduce by 77 % but hcho tvcd increased by 18 %. this variation tendency of no x and vocs caused toc in bth region greatly increased by 17 %. it indicated that in the voc-limited region, sharp reduction of no x emission took no role on the mitigation of ozone pollution, but even caused the increase of ozone concentration. improvement of omi ozone profile retrievals in the upper troposphere and lower stratosphere by the use of a tropopause-based ozone profile climatology characterization and correction of omps nadir mapper measurements for ozone profile 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troposphere in eastern china derived from high-resolution fourier transform spectrometry (fts) observations, atmospheric chemistry and physics comparisons with satellites and ground-based instruments characterisation of methane variability and trends from near-infrared solar spectra over hefei, china ozone profile retrieval from recalibrated global ozone monitoring experiment data tropomi on the esa sentinel-5 precursor: a gmes mission for global observations of the atmospheric composition for climate, air quality and ozone layer applications a preliminary assessment of the impact of covid-19 on environment -a case study of china tropospheric ozone trend over beijing from 2002-2010: ozonesonde measurements and modeling analysis the earth observing system sounder (eos mls) on the aura satellite, ieee transactions on geoscience and remote sensing first reprocessing of southern hemisphere additional ozonesondes (shadoz) profile records first reprocessing of southern hemisphere additional ozonesondes profile records: 3. uncertainty in ozone profile and total column observations of the vertical distributions of summertime atmospheric pollutants and the corresponding ozone production in possible environmental effects on the spread of covid-19 in china indirect effects of covid-19 on the environment satellite uv-vis spectroscopy: implications for air quality trends and their driving forces in china during first observation of tropospheric nitrogen dioxide from the environmental trace gases monitoring instrument onboard the gaofen-5 satellite development and preliminary evaluation of a double-cell ozonesonde assessing the relationship between ground levels of ozone (o 3 ) and nitrogen dioxide (no 2 ) with coronavirus (covid-19 the weekday/weekend ozone differences induced by the emissions change during summer and autumn in guangzhou, china fei zhao: software, writing-original draft preparation methodology. xiong liu: writing-reviewing and editing. juseon bak: writing-reviewing and editing. jae kim: writing-reviewing and editing. qihou hu: writing-reviewing and editing. congzi xia: data curation. chengxin zhang: data curation. youwen sun: data curation. wei wang: data curation for providing the fts data, omps science team for providing omps-lp data. we thank woudc for proving the ozonesonde data. we are grateful to tropomi science team for providing level 1 data. j o u r n a l p r e -p r o o f journal pre-proof key: cord-285620-oawrnmhy authors: fahimirad, shohreh; fahimirad, zahra; sillanpää, mika title: efficient removal of water bacteria and viruses using electrospun nanofibers date: 2020-08-16 journal: sci total environ doi: 10.1016/j.scitotenv.2020.141673 sha: doc_id: 285620 cord_uid: oawrnmhy abstract pathogenic contamination has been considered as a significant worldwide water quality concern. due to providing promising opportunities for the production of nanocomposite membranes with tailored porosity, adjustable pore size, and scaled-up ability of biomolecules incorporation, electrospinning has become the center of attention. this review intends to provide a detailed summary of the recent advances in the fabrication of antibacterial and antiviral electrospun nanofibers and discuss their application efficiency as a water filtration membrane. the current review attempts to give a functionalist perspective of the fundamental progress in construction strategies of antibacterial and antiviral electrospun nanofibers. the review provides a list of antibacterial and antiviral agents commonly used as water membrane filters and discusses the challenges in the incorporation process. we have thoroughly studied the recent application of functionalized electrospun nanofibers in the water disinfection process, with an emphasis on their efficiency. moreover, different antibacterial and antiviral assay techniques for membranes are discussed, the gaps and limitations are highlighted and promising strategies to overcome barriers are studies. removing bacteria from water supplies which meet the requirement of effective antimicrobial activity, superior filtration flux with acceptable retention potentials (zodrow et al., 2014) . nanofiber membranes, because of their high surface area to volume ratio, nano-sized pores, and high porosity, have been illustrated to improve the efficiency of conventional materials employed for the filtration and separation of particulate materials (aussawasathien et al., 2008) . a number of processing techniques including melt-blown, self-assembly, phase separation, template synthesis, and electrospinning have been employed to prepare nanofibers in recent years. among them, electrospinning is the most promising, efficient method to produce web-like non-woven ultrafine fibers including microfibers (>1 μm) or nanofibers (<1000 nm) from different kinds of polymers. moreover, incorporation of bioactive, antimicrobial and antiviral agents into nanofiber structure is easily possible through the electrospinning process fahimirad and hatami, 2019; faccini et al., 2015) . the present work reviews previous studies on the production and application of electrospun nanofibers as antimicrobial water filtration membranes. the merits and demerits of these novel water microfiltration tools are discussed. moreover, their antibacterial efficiency and disinfection activities are compared with commercial water membrane filters comprehensively. finally, some points are recommended to be noticed as the subsequent future research plans. the objectives of this review were to: (i) introduce the different procedures, which have been applied for incorporation of the various antimicrobial agents into electrospun nanofibers (ii) discuss the different antimicrobial tests used for proving antimicrobial activity of the fabricated electrospun water filters (iii) study the efficiency of the produced antimicrobial electrospun application in the water treatment industry. j o u r n a l p r e -p r o o f the electrospinning approach was invented by cooley in 1900 (cooley, 1900 . this method is easy, cost-effective, uncomplicated, and has the potential for scale-up production. the flexibility in material selection and additive incorporation to obtain appropriate functionality, as well as its considerable capability to produce fibers in the sub-micron range with the high surface-area (up to 40 m 2 g -1 based on the fiber diameter), are prominent privileges of electrospinning process for fabrication of nanofibers. in addition, effective porosity of electrospun nanofibers (almost about 80% with no upper limit) with many small pores, interconnected pore structure directly promote both infiltration rate and contaminant rejection ratio in comparison with conventional materials being used for mf applications (nasreen et al., 2013; wang et al., 2013) . in this process, a prepared solution of polymer is loaded into a syringe and fed at a set flow rate to the spinneret. due to the needle connected to a high voltage power supply under the electric field with a specific voltage, a taylor cone is constructed by elongation of the polymer droplet at the end of the syringe into a characteristic conical shape. enhancing the electrical field causes the formation of a steady jet elongated and whipped consecutively by electrostatic repulsion. the solvent evaporates when electrostatic forces prevail over surface tension and the jet gets finer, so electrospun nanofiber in mf application, such as uniform fiber morphology with controllable pore size, interconnected open pore structure, high porosity, and membrane thickness, turn them to a superior substitute to replace the conventional mf membrane such as the millipore gswp mf membrane with an average pore size of 0.22 mm (wang et al., 2012; barhate and ramakrishna, 2007) . another novel application of electrospun nanofiber in water purification and bacterial rejection is thin-film nanocomposite membrane (tfnc), a major type of reverse osmosis (ro) and nanofiltration (nf) membranes, which compromises of three layers including the first barrier layer of interfacial polymerization, a polyacrylonitrile or poly (vinylidene fluoride) electrospun membrane as the second layer and nonwoven polyethylene terephthalate (pet) as the third layer. the third layer employed as a substructure layer to provide the whole membrane adequate mechanical strength (subramanian and seeram, 2013; yin et al., 2012; fig 2) . high water flux, great solute rejection, minimum membrane fouling, and perfect mechanical persistence are main properties of an ideal tfc membrane and turn it into an excellent candidate for microfiltration and ultrafiltration applications (li and wang, 2010) . sato et al., (2013) fabricated a novel composite fibrous membranes, consisting of an ultra-fine cellulose nanofibrous infused into electrospun polyacrylonitrile (pan, with an average diameter of 0.2 μm a mean diameter of about 30 μm as the barrier layer (40-100 μm in thickness) to provide filtration attributes) nanofibrous scaffold on a melt-blown polyethylene terephthalate (pet, with a mean diameter of 30 μm as the support layer (about 100 μm thick) to sustain mechanical strength) non-woven substrate for water purification. the nanostructure showed a retention rate of 99.9999% for e. coli filtering and the high percent of the ms2 virus, with 30 nm sizes, captured in the electrospun pan scaffold infused with m-ufcns (sato et al., 2013) . recently, taheran et al. (2019) j o u r n a l p r e -p r o o f fabricated a methodical portable water purification instrument using electrospun nanofiber. the device contained three distinct electrospun membranes. the first membrane was made by electrospinning of polyacrylonitrile/chitosan solution at 85:15 mass ratio as an antibacterial membrane, the second membrane was produced from laccase (10 unit g -1 ) immobilized onto pan/biochar 95:05% electrospun mat for removal of micro-pollutants and the third layer was fabricated by electrospinning of pan/biochar at 95:05 ratio as an adsorptive membrane. the applied technology led to approximately 99% removal of microorganisms, 83% of micropollutant removal, and more than 77% of turbidity decline during less than 5 min contact time (taheran et al., 2019) . the important characteristics of a nanofiber mat membrane for application as filters for the separation of contaminations and pathogens from a continuous fluid phase are wetting properties, permeability, porosity, fiber size distribution, and fiber structure. for water filtration, a membrane must be wet-table and surface wetting properties are generally specified by the contact angle. a surface with a low contact angle (below 90 degrees) is considered a hydrophilic surface, while a surface illustrating a high contact angle (over 90 degrees) is referred to as a hydrophobic surface. sessile drop and the captive bubble method are two common techniques used for measuring the nanofibers' contact angle (nuraje et al., 2013) . one of the key parameters in filter design and its performance is porosity. generally, porosity is calculated from the apparent density and bulk density of the membrane. however, other alternative procedures inclusive of image analysis and mercury porosimeter are frequent methods j o u r n a l p r e -p r o o f applied for the evaluation of porosity in the nanofiber membrane (ghasemi-mobarakeh et al., 2007) . electrospun nanofibers are highly porous with interconnected pores in the size range of just a few times the fiber diameter. the small pore size of the nanofibrous membrane introduces a higher retention rate, the interconnected pores leads to better tolerance against fouling and the high porosity defined a higher permeability capability (homaeigohar et al., 2010) . clean water permeability (cwp (l/m2 •h•bar)) illustrates the highest amount of attainable flux dependent on the membrane condition. it can be assayed by calculating the flux at various trans membrane pressures (tmp). the slope of the eventuated curve is regarded as the cwp (bjorge et al., 2009) . the high cwp grants high flux operation to the membranes, introduces the nanofiber mat as an energy-saving membrane, and means that if fouling does not happen, enormous volumes can be treated (daels et al., 2011; he et al., 2018) . the surface charge on membranes is related to affinity corresponding interactions and considered as a significant parameter influencing the disinfection capabilities of the membrane. surface charges can qualify the strength of biomolecular or even pathogen affinity on a material surface. in virus removal, surface charged nanofibers adsorb virus via electrostatic interactivity between the nanofibers and the counter-charges of virus and signify virus remediation improvement (cho et al., 2012) . a series of studies have confirmed that electrostatic attraction between the cationic membrane and the anionic surface of bacteria may lead to morphological defects in consequence of ros generation and cell membrane destruction. indeed, anionic membranes act as powerful non-adhesive site of bacteria attributable to electrostatic repulsion (mukherjee and de, 2018; kolewe et al., 2016) . operating conditions influence the antibacterial activity performance of the nanofibrous membrane. as proved by several experiments, bacterial cells are able to decline their size at higher operating pressure, hence resulting in enhancing permeation through the filter. therefore, less trans membrane pressure (tmp) is usually desired, to retain antibacterial activity during long term application of the membrane. the tmp is described as the mean feed pressure minus the permeate pressure that is essential to push down water through a membrane (mukherjee and de, 2017; . different factors including surface area, surface roughness, pore diameter, zeta potential, and inclusion of biocides or antibacterial agents determine the antimicrobial performance of membrane (rahaman et al., 2014; mukherjee and de, 2018) . accordingly, the employing of electrospun polymeric membranes in bacterial and virus removal from water is performed in two procedures including size exclusion and adsorption (lee et al., 2016) . in most cases, the diameter of water-borne bacteria is more than 0.2 μm. for example, the e. coli size is 0.5-2.0 μm and brevundimonas dimimuta dimension is 0.3-0.9 μm. previous studies have confirmed that using a 0.45 μm pore sized mf leads to a 2 log-4 log bacteria reduction (gómez et al., 2006; ghayeni et al., 1999) . thus, based on the degree of exclusion, the electrospun membrane should have an average pore size of fewer than 0.2 μm. in addition, the narrow pore size distribution is requisite for achieving a high retention rate (ma et al., 2014) . there is a direct relationship between the pore size and the fiber diameter of a porous nonwoven structure. the relationship has been confirmed as the average pore size was approximately 3±1 times the mean fiber diameter, and j o u r n a l p r e -p r o o f the greatest pore size was about 10±2 times the mean fiber diameter. thus pore size of electrospun fiber generally grows with increasing fiber diameters (ma et al., 2011) . various conventionally employed membranes for the application as micro-filters have 0.2 μm theoretical pore sizes. the advantage of electrospun nanofiber membranes in comparison to conventionally used membranes are the simplicity of manufacture, adjustable size of the pores and high porosity (saleem et al., 2020) . in view of the fact that the membrane pore sizes can be controlled by adjusting the electrospinning parameters and besides the fact that the most aquatic bacteria dimensions are more than 0.2 mm, electrospun nanofibers can be designed efficiently with smaller pore dimensions suitable for mf applications (wang and hsiao, 2016) . for instance, accelerating the flow rate raises the pore diameter by enhancing the fiber diameter. moreover, increasing polymer solution concentration and using higher molecular weight polymer increases fiber diameter. employing a secondary ring electrode circling the nozzle cause reducing the fiber deposition and consequently decrease the density of the membrane, the parameter which reduces the pore size. in addition, controlling fiber distribution, post electrospinning modification and using temporary spacers can be utilized for controlling pore size (dong et al., 2015; haider et al., 2018) . as discussed above and based on the size exclusion process, microfiltration larger sized bacteria are substantially seized by the membrane but it is not efficient in separating small sized viruses within 0.01-0.1 µm range size (mi et al., 2014a; barhate and ramakrishna, 2007) . so, rejection of bacteria smaller than membrane pores or viruses needs the incorporation of antiviral or antibacterial agents into the membrane. also, after size-exclusion microbial removal of the membrane, intercepted bacteria can be released and induce membrane biofouling during subsequent filtration. therefore, antimicrobial agents are commonly used to prohibit bacterial j o u r n a l p r e -p r o o f growth and biofoul formation that would decline filter efficiencies (botes and cloete, 2010; wen et al., 2017) . various bioactive agents with different fundamental properties may have consequential impacts on bacteria removal. plus, nanofiltration membranes or ultrafiltration membranes with a positive charge on the surface are able to remove viruses selectively (mukherjee and de, 2017). moreover, incorporating antimicrobial agents into electrospun nanofibers enhance the antimicrobial activity of fabricated nanofibrous membrane (nasreen et al., 2013; park and kim, 2017 ). an ideal bioactive agent incorporated into the functionalized membrane should be nontoxic, water insoluble with no or slight leaching property. also, the functionalization process should not cause adverse influences on the quality and overall performance of the membrane. based on the majority of researches studied in this review, blending and post-modification strategies are two commonly used techniques to incorporate biocide agents into nanofibers aiming for water disinfection application (shalaby et al., 2018; he et al., 2018; makaremi et al., 2016) . blend electrospinning is an easy one-step procedure, mostly used for agents' incorporation into nanofibers (shabafrooz et al., 2014) . using the same solvent, the bioactive agent is dissolved directly into the polymer solution and a homogeneous blended solution of the incorporating agents in the polymer solution is prepared for the electrospinning step (pillay et al., 2013; fahimirad and ajalloueian, 2019). j o u r n a l p r e -p r o o f the agents incorporation into electrospun fibers can be performed after the electrospinning process by physical or chemical treatments. covalent and non-covalent immobilizations are fundamental methods for molecules attached to the fiber surface. non-covalent immobilization is performed by immersion of electrospun mats in a solution compromising the bioactive molecules. by treating with plasma the surface gets activated for subsequent modification using specified ligands like active amine groups. the affinity of incorporated agents to the electrospun nanofiber surface improves by covalent immobilization (wang and windbergs, 2017; kurusu and demarquette, 2019) . some commonly used antimicrobial or antiviral agents in electrospun nanofibers are discussed in this section. silver nanoparticles (agnps) are considered the most efficient nanoparticles for biological applications and the most extensively applied antibacterial agent for water disinfection mukherjee and de, 2018) . agnps are capable to puncture the microorganisms' cell walls, interact with their nucleic acids and attach to their enzymes, which cause the cell membrane destruction and finally growth inhibition. different feasible interactions of ag + ions with various bacterial biomolecules are documented. furthermore, the extended range of antibacterial activities and virulence effects of ag + ions toward several microorganisms (e.g. bacteria, viruses, and fungi) at only a few mg ml -1 are confirmed in previous studies. thus, silver nanoparticles are recognized as potent disinfection agents (lópez-heras et al., 2015) . in water purification, nanosilver materials have been mainly applied to prevent the formation of there are three main methods for agnps incorporation into electrospun nanofibers including 1) blending of prepared synthesized agnps solutions to the polymer solution, 2) agnp synthesis in the polymer solution by employing a precursor, and 3) post-treatments of the electrospun nanofibers for agnp synthesis by reduction of the precursor that has been spun along with the electrospinning solution (fahimirad and ajalloueian, 2019). there are three main approaches to produce iron oxide nanoparticle-nanofiber composites, including (1) electrospinning of solution containing prepared ionps, (2) in-situ synthesizing of ionps during the electrospinning process or in the solution to be electrospun and (3) it has been indicated that due to electrostatic interaction, cunps illustrate antibacterial functions on the bacterial cell through different mechanisms, such as adhesion to the bacterial cell wall, lead to detrimental impacts on protein structure within the cell membrane, denaturation of j o u r n a l p r e -p r o o f proteins in inertial parts of the cell , and adverse effects on phosphorus-and sulfur-containing compounds like dna (raffi et al., 2010) .recently, cunps have gained considerable interest because of their broad-spectrum and acutely effective antibacterial activity with comparatively low cost and high scalability (taner et al., 2011) . recently, zinc oxide (zno) has received much attention due to its non-toxic profile, effective antibacterial activity, adsorptive properties, mechanical, chemical, and thermal stability while encountering diverse environmental conditions (tiwari et al., 2018) . zno particles have illustrated antimicrobial activity against both gram-positive, gram-negative bacteria and even against spores wagner et al., 2016) . zno nps are considered bio-safe, nontoxic, and biocompatible (hameed et al., 2016; farrokhi et al., 2019) . in comparison with bulksized particles, nanoparticles can pass through bacterial cell walls more simply. the release of zn 2+ ions from nps destroy the cell membrane and subsequently enhance cellular internalization of the nanoparticles. it is also confirmed that the antimicrobial function of zno can be ascribed to photocatalytic activity. by receiving uv light which promotes its interaction with bacteria, ros, which has a phototoxic effect on bacteria, will be produced (dimapilis et al., 2018) . journal pre-proof tio 2 is a biocompatible chemical thermally stable compound with high photocatalytic activity and has shown good antimicrobial activities with wide spectrum function against microorganisms (gram-negative and gram-positive bacteria, fungi, and virus). the generation of reactive oxygen species (ros) is the major mechanism of tio 2 . due to its photocatalytic nature, antimicrobial activity of tio 2 nps enhances by exposing uv light on its surface (de dicastillo et al., 2020; levchuk et al., 2018b; levchuk and sillanpää, 2020) . it is proved that lanthanum compounds, such as lanthanum hydroxide (la(oh) 3 ), lanthanum carbonate (la 2 co 3 ), and lanthanum hydroxide (la(oh) 3 ) can attach to phosphate so firmly that they can generate lapo 4 and remove redundant phosphate in a bacterial cell. according to the very significant band to phosphate, nano-lanthanum (la) species represent high effectiveness adsorption and suppress microbial growth by inhibition of the microorganism growth liu et al., 2017) . carbon is the chemical element with atomic number 6 and six electrons situate 1 s 2 , 2 s 2 , and 2p 2 atomic orbital. graphene is a one-atom-thick hexagonal structure consisting of a 2-dimensional bhatnagar et al., 2013) . furthermore, the existence of these functional groups advances the interactions with biomolecules and leads to bacterial death with no intracellular process. go nano-sheets with sharpe edges hurt the bacterial cell membranes, lead to leakage of the intracellular matrix and eventually cause inactivation of bacteria. plus, go generate oxidative stress by producing ros and lead to dna damage and mitochondrial dysfunction (kumar et al., 2019) . in addition, the antiviral activity of go is confirmed by several experiments (ye et al., 2015) . single-walled carbon nanotubes (swnts) are nanometer diameter cylinders fabricated of rolled up graphene sheet in the form of a tube. generally, swcnt length is in the micrometer range and their diameters vary from 0.4 to 2 to 3 nm (eatemadi et al., 2014) . swnts have presented strong and board spectrum antimicrobial activities. the antimicrobial activity of swcnts has been confirmed to be varied by several factors. for instance, longer length nanotubes exhibited superior antimicrobial activity, swcnts having surface groups of -oh and -cooh illustrate more strong antimicrobial activity in comparison with swcnts-nh 2 , also the diameter of nanotubes is an important factor governing their antibacterial effects (dong et al., 2012) . chitosan [poly-(b-1/4)-2-amino-2-deoxy-d-glucopyranose] is quaternary ammonium cations are positively charged polyatomic ions. these ions contain a positively charged nitrogen "head" binding four bonds r including an alkyl group or an aryl group. quaternary ammonium compounds are salts of quaternary ammonium cations (tezel and pavlostathis, 2012) . because of their positively charged sites, they are able to generate electrostatic bonds with the negatively charged sites on bacterial cell walls, resulting in disruption of a cell wall, defect cell membrane permeability and consequently sever leakage of intracellular low-molecular-weight materials (chen et al., 2014) . qacs target bacterial cell membranes. therefore, they illustrate extended-spectrum antimicrobial activity and have been widely employed to construct an antibacterial surface (jennings et al., 2015) . quaternized poly benzalkonium chloride (bac) are some important kinds of qacs (zhu et al., 2018) . easy release of biocides from the membrane improves their exposure rate to bacterial cell. there is a challenging point since the leaching profile of incorporated biocides determines long term bactericidal efficiency of the membrane. leaching of bactericidal agents resulted in the diminution of the membrane antimicrobial performance over time. gradual leaching of the blended biocides during the filtration process not only declines the antibacterial activity, but may j o u r n a l p r e -p r o o f also lead to secondary pollution (fu et al., 2014) . besides chemical contamination and cytotoxicity issues, the continuous release of bactericidal agents causes the development of bacterial resistance due to being exposed to sub-inhibitory concentrations of biocides (sile-yuksel et al., 2014; mukherjee and de, 2018) . thus, there is a challenge to provide process eluding leaching of toxic materials while illustrating rapid pathogens killing ability. nanofiber coatings based methods which promote contact pathogen-killing capacity are promising and can be obtained by chemical modification with tethered biocides functionalities. these strategies may be successful by regarding the right control over the binding quality between the active agent and the underlying biomaterial surface (zhang et al., 2016; bazaka et al., 2015; hilpert et al., 2009) . despite there are numerous researches on application of antibacterial electrospun nanofiber membrane in water filtration, the leaching pattern and durable bactericidal efficiency of the membranes have not been studied comprehensively. this method is generally used for testing the inherent antibacterial performance of fabricated electrospun nanofibers as a membrane. this assay generally consists of qualitative detection and quantitative measurement techniques (zhu et al., 2018) . the inhibitory activity of electrospun nanofibers is assayed by the inhibition zone diameter or agar diffusion method toward the considered bacterial sample, based on the clinical and laboratory standards institute (clsi document m02-a12) (clsi, 2015) . for this reason, 100 μl overnight culture of the tested bacteria (10 6 cfu/ml) is spread across the surface of an appropriate agar plate, the electrospun nanofiber is cut to disk with about 10 mm diameters, sterilized under uv light for 20 min and then incubated on the plates for 18-24 h at 37 °c. then, the area of bacteria growth is detected, and the diameter of the inhibition zone around the electrospun nanofiber is measured. this procedure modifications are also used (santos et al., 2016; jatoi and al mamun, 2020; fig.3 a) . the antibacterial function of the membrane will lead to changes in the bacteria cell morphology. this method is a shaking flask method. briefly, an appropriate amount of sample sterilized nanofiber is weighted, dipped into a flask containing pbs buffer with a cell concentration of 1-4 × 10 5 cfu ml -1 . the flask is incubated with continuous shaking at 37 • c for a determined time. after serial dilutions by the phosphate buffer, the bacterial suspensions are plated in the agar plate. the inoculated plates were incubated at 37 • c for 24 h and the viable bacterial cells are counted by a colony counter (kleyi et al., 2015) . also, the number of bacteria after incubation for a determined time can be indirectly measured by spectrometric optical density at 625 nm . then, the reduction rate is calculated with the following equation: where r is the reduction rate, a is the number of bacteria isolated from the inoculated electrospun nanofibers after defined time contact time, and b is the number of bacteria isolated from the inoculated electrospun nanofibers at zero contact time (yao et al., 2016) . j o u r n a l p r e -p r o o f the aatcc 100 test method quantitatively evaluates the bacteriostatic (growth inhibition) or bactericidal (killing of bacteria) ability of textiles over a 24 hours contact. for this test, firstly a defined weighted of nanofiber is cut (about 3 mg), get sterilized by uv light, then inoculated with 0.1 ml microbial suspension (1-1/5 × 10 5 cfu ml -1 ) and finally overnight incubated at 37 • c. over determined contact period, 10 ml pbs buffer is added to the falcon tubes containing the inoculated treated electrospun nanofiber. after 1 min shaking, 10 µl of the solution is cultured on nutrient agar plates and incubated for 24 h (ardekani et al., 2019). astm e2149 is another antimicrobial standard method used for evaluating the antibacterial function of immobilized antimicrobial nanofibers under dynamic contact conditions. the antibacterial efficiency is evaluated depending on the contact time from several mints to 24 h between the bacterial solution and the sample (ungur and hrůza, 2017) . for both methods, the percentage of growth reduction is calculated with the r equation, mentioned above. in this method, some known dyes are been used to probe if the entrapped bacteria are inactivated by membranes and quantify surviving bacteria, representing an operative, visual and precise antibacterial assay (zhu et al., 2018) . for example, a common dye-based method is detecting the optimal analytical parameters for fluorescence measurements from the dyes syto and propidium iodide (pi). the basis of this approach is the attachment of syto to live-cell and propidium iodide (pi) to dead cells or cells with defected membranes. the optimal analytical parameters are used for measurement fluorescence by evaluating the intensity of emissions at 505-515 nm for syto and 600-610 nm for pi which interpret to quantify of the live cells minimum inhibitory concentration (mic) represents the minimum amount of antibacterial membrane, which could inhibit bacterial growth. in this method, the defined weighted of nanofiber is dissolved in water (or proper dissolvent), 100 µl of this solution is added to the first well and serially diluted by transferring 50 µl of the well pipetted content to the next well containing 50 µl media. thereafter, 50 µl of bacterial cultures (1×10 6 cfu ml -1 ) is poured to each well and plate is incubated at 37 ºc for 24 h. to detect the bacterial growth, resazurin or piodonitrotetrazolium chloride is added to wells. the wells that turned pink (if resazurin used) or purple (if p-iodonitrotetrazolium chloride used) represents the surviving of bacteria, hence no growth inhibition. the nanofiber concentration in the last growth inhibited well is considered as the mic value (nthunya et al., 2017). the bacteria retention test can also be performed with a dead-end filtration module using a vacuum filtration cell, a syringe filter holder 25mm, millipore and a dead-end filtration cell j o u r n a l p r e -p r o o f system (jabur et al., 2016; daels et al., 2011; son et al., 2009) . before the experiments, the membrane cut diameter and sterilized. all pieces of filtration equipment are sterilized with an autoclave method for 20 min at 121 °c. the membrane is fitted into the device. after passing sterile water from the filter, the bacterial suspension is filtered through the membranes using a pressure. in this step there are two different techniques for evaluation of bacterial retention: 1) the filtrate is serially diluted with sterile distilled water and viable counts are assayed by plate counts. the colony count can be facilitated by staining bacterial cells with syto 9 fluorescent dye and using a fluorescence microscope . then the bacterial retention ratio is calculated in terms of lrv (log reduction value) by the equation: lvr= log (c f /c p ) where r= (1-(c p /c f )) × 100 electrochemical disinfection can destroy bacteria and viruses by electroporation and reactive oxygen species (ros) during a short time. electrochemical treatment devices electrochemical disinfection regarded as an effective portable water disinfectant. fabrication of electrospun j o u r n a l p r e -p r o o f porous membrane filter using agents to provide a conducting bed and a strong electric field, facilitate electroporation and production of ros, which signifies the disinfection process (hong et al., 2016; huo et al., 2018) . for testing this ability, an electrochemical filtration device with electrospun nanofiber as a filtration membrane is used. then, a saline solution containing bacterial suspension flows through the nanofiber filter using low voltages at a defined flow rate. the bacterial removal efficiency is calculated by the lvr equation (wen et al., 2017; tan et al., 2018; xie et al., 2020) . in order to determine the deposition of bacteria on a filtrated membrane and the possibility of biofouling, instantly after filtration, the membrane is transferred to an autoclaved beaker filled with pbs buffer and sonicated. the bacteria in the suspended membranes are measured by counting the number of colony cells. moreover, the morphology of trapped bacteria is investigated using sem (xie et al., 2020; makaremi et al., 2016; wen et al., 2017) . different kinds of electrospun nanofibers have been recently fabricated for bacterial removal from water are illustrated in tables 1. usually, evaluation of the antiviral function of nano-filters is carried out using bacteriophage and polypropylene nonwoven textile as support layer, the structure shows excellent retention of bacteria and fine solids, with 240 -400 nm pore size and operating pressure < 2 000 mbar. naked filter is anther novel commercially application of nanofiber in household/bottled water filter with ability to remove 99.9999% of the micro-organic contaminants. nanotrap is another commercial household water filter produced by coway company. astrapool, fluidra has introduced nanofiber based product applied in filtration system for residential pools (http://electrospintech.com/products.html#.xvs_nm0zbiu). liquidity nanotech corporation has created electrospun nanofiber membrane made water purification cartridge with superior flow rate, about a cup per minute, good microbiological retention, 6-log bacteria reduction, 4-log virus reduction and 6-log cyst reduction and simple usage process (https://product.statnano.com/product/1981/liquidity-water-purification-cartridge). pentair company has produced polyethersulfone nanofiber-based cartridge for industrial water purification applications. the cartridge is an absolute barrier to bacteria and viruses: with more than 4-log reduction rate (https://www.directindustry.com/prod/pentair-x-flow/product-71363-1779744.html). the researcher's and industry's attention to research and development of electrospun nanofibrous membranes has been growing because of its simplicity, low-cost, scalable molecules incorporation process on the fabricated non-woven mats, production of membranes with the high surface area.. high surface area to volume ratio, uniform pore size, and high pore interconnectivity and adequate antibacterial property improve the performance of the nanofibrous membrane in water disinfection application (subramanian and seeram, 2013) . however, there are several major concerns to be noticed for the application of electrospun nanofiber in water disinfection. although high surface area and porosity of the electrospun nanofiber are significant advantages, which enhance permeability and selectivity, they also lead to higher mechanical stresses. consequently, the membrane might be compacted or deformed through the filtration process, which causes loss the porosity and subsequently decreases the also, further experimental studies needed to conduct proper control of biomolecules release rate from nanofiber, to ensure a balance between successfully deactivate the bacteria strains and lengthen the period of the function, and minimize contamination. therefore, fabrication of membrane representing inherent self-cleaning, antiviral, and the antibacterial and anti-biofouling feature has gained immense attention for industrial application. recently, focusing on the production of smart antibacterial surfaces has led to a promising "kill−release" strategy. this approach proposed the fabrication of dual-functional antibacterial surfaces by incorporating biocides into non-fouling materials. these membranes are able to maintain their long-term antibacterial activity by killing bacteria attached to their surface and subsequently are potent to release the dead bacteria to reveal a clean surface (wei et al., 2017) . although these smart membranes are applied for biomedical applications, the strategy can be promising for further j o u r n a l p r e -p r o o f designing of novel electrospun nanofiber with these dual functions and strong long-term functional ability in water disinfection. as it is illustrated in tables 1 and 2, despite the significant results obtained from the application of electrospinning in water filtration membrane designing, there are some gaps in this research area. for instance, there are no unanimous standard methods for evaluating the antibacterial or antiviral potential of fabricated electrospun water disinfecting filters. moreover, most of the researchers have 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science & technology photo-crosslinked pva/pei electrospun nanofiber membranes: preparation and preliminary evaluation in virus clearance tests. separation and purification technology polyvinylidene fluoride membrane blended with quaternary ammonium compound for enhancing anti-biofouling properties: effects of dosage progress and challenges in photocatalytic disinfection of waterborne viruses: a review to fill current knowledge gaps polyethyleniminemodified chitosan materials for the recovery of la (iii) from leachates of bauxite residue polymeric antimicrobial membranes enabled by nanomaterials for water treatment mitigating biofouling on thin-film composite polyamide membranes using a controlled-release platform key: cord-354254-89vjfkfd authors: peng, shanbi; chen, qikun; liu, enbin title: the role of computational fluid dynamics tools on investigation of pathogen transmission: prevention and control date: 2020-08-31 journal: sci total environ doi: 10.1016/j.scitotenv.2020.142090 sha: doc_id: 354254 cord_uid: 89vjfkfd transmission mechanics of infectious pathogen in various environments are of great complexity and has always been attracting many researchers' attention. as a cost-effective and powerful method, computational fluid dynamics (cfd) plays an important role in numerically solving environmental fluid mechanics. besides, with the development of computer science, an increasing number of researchers start to analyze pathogen transmission by using cfd methods. inspired by the impact of covid-19, this review summarizes research works of pathogen transmission based on cfd methods with different models and algorithms. defining the pathogen as the particle or gaseous in cfd simulation is a common method and epidemic models are used in some investigations to rise the authenticity of calculation. although it is not so difficult to describe the physical characteristics of pathogens, how to describe the biological characteristics of it is still a big challenge in the cfd simulation. a series of investigations which analyzed pathogen transmission in different environments (hospital, teaching building, etc) demonstrated the effect of airflow on pathogen transmission and emphasized the importance of reasonable ventilation. finally, this review presented three advanced methods: lbm method, porous media method, and web-based forecasting method. although cfd methods mentioned in this review may not alleviate the current pandemic situation, it helps researchers realize the transmission mechanisms of pathogens like viruses and bacteria and provides guidelines for reducing infection risk in epidemic or pandemic situations. volume, contact angle and environmental temperature were analyzed and the lifetime of droplets under those conditions was investigated. the evaporation of droplets will also be affected by the dust in the air, and this factor should be also considered in the future. different from other particles, pathogens are much smaller and their diameters are generally no more than 100nm and their motion is largely affected by flowing air, hence it is difficult to analyze their trajectories directly in the atmospheric environment. with the development of computer science, a new method based on computation fluid dynamics (cfd) can be used to solve this problem and it has been already well developed over the years. [20] and in the next decades, an increasing number of investigations about air pollution, atmosphere environment and pathogen transmission can be found. as mentioned above, the droplet can bring the pathogen into the airflow and hence cause infectious diseases due to the spread of it. normally the droplet with pathogens is generated by coughing or sneezing from the infected and the procedure of droplets generated by sneezing is shown in fig.2 : the impact of covid-19 is global and the pandemic situation is closely related to the health of every individual. it does not mean that there is no way to prevent or control it effective vaccines are unavailable though. understanding the transmission of infections such as covid-19 in various media is of great importance. in this review, the principles of different cfd algorithms are described concisely and intuitively; theories and applications of cfd in investigations of pathogen transmission are summarized. the objective of this research work is to indicate the important role of cfd method in analyzing pathogen transmission. through summarizing various applications of cfd method, the transmission mechanism of pathogens and prevention methods are also concluded in this work. three steps are necessary for numerical analysis by using cfd tools: (1) generating the mesh model with high quality is the key to ensure the accuracy of calculation; (2) boundary conditions are required to define variables at the boundary. (3) different algorithms that can be selected in cfd determine the way of iteration. this work carried out in this section is to summarize the feature of cfd from three aspects: simplification, algorithms diversity and maneuverability. different from experimental methods, the cfd method based on mathematical models that can be operated on computers is effective and cost-saving. in numerical simulations, the pathogens are carried by small particles like solid particles or droplets can be defined by calculation models. although the biological properties of the pathogen are complicated and various, the shape feature of the pathogen carrier is relatively simple to describe. in cfd, those particles can be defined as spheres, tetrahedrons, hexahedrons and even by the shape factor, then the pathogen transmission in different environmental fluids can be solved by utilizing multiphase models. moreover, the transport species model can be also applied to simulations of it. in this model, the infectious pathogen in the air is defined as the pollutant source with a constant concentration (generally measured by the field experiment). characteristics of fourier heat transfer law used to describe the heat exchange: fick law used to describe the mass exchange: (j 1j is the source diffusion relative to coordinates, d 12 is the diffusion coefficient between two sources) 1 1 1 1 12 12 12 () reynolds transportation law calculates the source quantity in control volume at time "t", which can be described as: introducing the continuous equation: and guass law (divergence law) then, the improved transportation can be written as: combining the balance equation of forces: then, the equation can be written as the form shown below: considering the acceleration caused by forces except the drag force and solving the particle motion in each step by iterative calculation: besides, the volume of fluent (vof) model performs well in simulating pathogen transmission, especially in the gas-liquid interface. in a control volume, the total value of each phase equals 100% and there are three situations in vof: if the volume fraction of "q" phase is  ,then: (1) 0 α  , no "q" phase in this cell; (2) 1 α  , the cell is full of "q" phase; (3) 0< α <1, interface between "q" phase and other phases can be found in the cell. the momentum equation and the energy equation of vof are determined and shared by each phase. the momentum equation mainly depends on characteristics and volume fraction of each phase and it can be written as below: energy equation of vof can be written as: j o u r n a l p r e -p r o o f k eff is effective thermal conductivity; j j,q is diffusion flux of "j" phase in "q" phase while the h j,q represents the enthalpy of it; s h is the volume of the heating source defined by users. the energy was defined as a variable relating to the average quality in vof: (17) resistance characteristics in all directions are assumed the same, and the equation can be written as: generally, the inertia resistance coefficient c 2 and viscous coefficient   are needed as the parameter of the boundary condition. taking the medical mask as an example and the way of obtaining these parameters are shown in fig.3 : the pressure difference (p 1 -p 2 ) between both ends of material from the mask as shown in fig. 3 j o u r n a l p r e -p r o o f can be measured under a velocity input (v i ). the relationship between pressure difference and the input velocity can be described by the equation as: then the coefficient c 2 and   can be calculated in the case of density  and thickness n  are known. some of investigations about transport species model and multiphase model are listed in tab several algorithms are mainly used in recent as summarized in table. 3. although the mechanism of pathogen transmission in the fluid is complex, the motion of pathogens still follows the hydrodynamics law and can be solved by mathematics models of cfd algorithms. for example, the lbm method can be used to solve pathogen transmission in small-scale while fdm method can be applied on the large-scale transmission of the pathogen. cfd tools are in high compatibility and their computing files can be transferred in a variety of software. in general, the structure of cfd software consists of three parts: pre-processing, solver and post-processing and fig. 4 below shows some options of each part. pathogen transmission in the environment is a complex process. for the sake of the accurate simulation result, the calculation model and parameters of the simulation are necessary. furthermore, epidemic models should be taken into account in numerical simulations. by using experimental methods to get the data that is required in the boundary condition is important, besides, experimental data are also needed to validate the simulation result. this section summarizes various epidemic models that should be used in the simulation. moreover, experimental methods which can be applied to analyzing pathogen transmission are presented in this section as well. although some of the experiments summarized were not used in combination with cfd methods, they can provide valuable references for similar studies by using numerical simulations. poussou, et.al [44] investigated the effects of moving people on pollutant diffusion and airflow. by combining the piv experiment technology, they used cfd method with a second-order upwind scheme to simulate the airflow. the re-normalization group (rng) k-ε was used in simulation in order to solve the turbulence with the good performance of accuracy, efficiency and robustness; in gao and niu [45] study, rng k-ε model including the effect of low-reynolds-number is used to solve the airflow and the diffusion of tracer gas which can represent the contaminant transmission are calculated by the equation below: where t,  and  are time, air density and tracer gas concentration respectively. unsteady flow is a big challenge in accurate simulation as zhang, et.al [46] indicated. flow in the environmental channel is always unsteady, and it hence increases the complexity of simulation on pathogen transmissions. how to treat an unsteady flow as the steady flow in practice is still a difficulty. by defining the wave in hydraulic calculation can effectively simplify the disturbance in unsteady flow. capillary wave [47] can reflect the disturbance brought by some factors to surface of fluid which can be written as: (1) for shallow waves: (2) for deep waves: ku [48] presented a "waveform" method to model unsteady flow in blood which reflects the relationship between time and volumetric flow rate: fig.5 volumetric flow rate mantha, et.al [49] used this method in the simulation of biological flows and found the relationship between wall shear stress and the location of the aneurysm; nanduri, et.al [50] also used "waveform" to solve the unsteady laminar flow and the objective of this study is to build a human body surface model to simulate the airflow around the body. although this method is useful for analyzing particle transportation in biological flows, it is not suitable for simulating unsteady flow in the atmosphere due to greater disturbance. more, in order to simplify the model for analyzing the airflow in building, axley [51] presented a multi-zone model which allows users to calculate the hourly rate of airflow between various rooms and dols and walton et.al [52] improved this model by providing the equation of mass conversion as: based on the dispersal theory which is not limited to the wall-mixed region, multi-zone model parameters should also be considered as well. airflow caused by temperature difference will affect pathogen transmission. chen, et.al [56] simulated the three cases by combing the multi-zone model and two-way air flow effect in order to demonstrate the effect of temperature difference on air quality of indoor. it can be found from one of the cases they studied, the airflow generated by the temperature difference between bathroom and corridor can transport infectious pathogens, and hence the door of infected zoom should be closed as they suggested. closing doors and windows in a room is not equivalent to obtaining a closed space. the crack of the door and windows is always ignored by researchers when simulating the airflow or pathogen spreading in the building or a single room. by using multi-zone method in cfd simulation, yang, et.al [57] analyzed the effect of stack and wind effect on contaminating dispersion and found that these factors will cause the contamination horizontally or vertically spread. their research also indicated that the pollutant gas can be transported through cracks of doors and windows and may cause infectious disease. because of the great effectiveness, multi-zone method was widely used in many cases which can be found in wu (1 ) where s is the susceptible people in an area, i is the number of infectious people and p represents the pulmonary ventilation rate of susceptible people. zhu, et.al [64] investigated the potential risk of infection in public transportation by using wells-riley model in cfd simulations. it was proved in their study that the closer to the operating exhaust in the bus the infected person is, the smaller the infection risk bringing to others is. besides, this study indicated that the ventilation system of most of buses is not effective because there is only one single exhaust was located in the middle of the cabin or the back wall. yan, et.al [65] studied the transmission of coughing particles in the breathing zone of people. in their investigation, the method that combines the wells-riley model and the lagrange model in cfd was used. it was illustrated from this study that the location of releasing particles will affect the particle travel distance. based on the well-riley model, this research work has also presented a quantifiable approach to assess the infection risk of passengers. these studies are helpful for improving the design of the vehicle ventilation system and hence reduce the infection risk though, they did not consider the effect of altitude on airflow patterns in vehicles. the wells-riley model can also be applied to building simulation. niu based on physical characteristics like aerodynamics of respiration droplets, chaudhuri, et.al [82] proposed a numerical model for the early state of covid-19 pandemic by integrated the chemical mechanism and pandemic evolution equations. the " " this work derived by using the theory of collision rate represents the lifetime of the droplet. it can be written as: some investigations based on these models are listed below in tab.5: more, hathway [92] combined the cfd method and sir model in order to analyze pathogen transmission in hospital space and asanuma and kazuhide ito [93] predicted the exposure risk of the population in the hospital by using cfd with considering the sir model. from these investigations, it can be found that this epidemic model is well performed in simulating the spread of infectious diseases. however, the number of researches that applied these models to cfd simulation is still a small amount due to the complexity of modelling and calculation in simulating the airflow or particle transport among a crowd of people. in cfd simulation, not only the mesh model is crucial but also the parameter of simulation is of great importance to let users obtain the results they require. generally, the boundary condition such as velocity, pressure, turbulence intensity can be measured from experiments. in recent, micro-particles experiments and tracer gas experiments are most used in investigations of airborne transmission. romano, et.al [94] simulated the airflow pattern and concentration of airborne particles in an operating theater (ot) by using cfd method. they also conducted an experiment in order to verify the accuracy of simulation results and in their experiment, a six-way aerosol distributor was used to convey the generated aerosol particles; opc (optical particles counter) equipped with a dilution system was used to measure the particle concentration; a rotating vane anemometer and a thermo-anemometer were used to measure the velocity and temperature respectively. they also validated the simulation result by comparing the data measured from the experiment and found that the experimental and numerical data were well coincided (error is less than 2% for temperature and 10% for velocity). the value of mean absolute percentage error for particle concentration is 42% though, the experimental curve and the numerical curve are similar in changing trends. therefore, experiments involving particle-fluid flow are more suitable for qualitative analysis, because it is hard to accurately control conditions such as temperature, pressure, stable velocity of flow. zhou, et.al [95] established a model which can be used to predict the distribution of negative ions produced by the air ionizer and the efficiency of this device. in their experiment, an emission system consisting of a compressor and nebulizer was used to compress the filtered air and aerosolize the j o u r n a l p r e -p r o o f bacteria; an ion counter was used to test the emission concentration. in order to present their experiment clearly, the installed experimental system is shown below in fig. 6 : fig. 6 the detailed experimental setup [82] the objective of the experiment carried out in this work was to measure the susceptibility besides, it was proved that the bacterial load in the shower air will increase while turning on the shower spray. the effect of droplet velocity and distribution on aerosolized bacterial groups was not given this study, more, the parameter of shower such as water temperature, nuzzle structures should be also considered in the experiment as well. choi, et.al [97] classified the airborne particle according to their optical properties by using experimental methods. ink-jet aerosol generator (ijag) was used to generate, dry the airborne particle, the light-scattering signal was used to estimate the correlation value in the classification analysis of airborne particles. the correlation value proposed in this work is helpful for particle detection and classification though, how to apply this method to detect other airborne pathogens with more complicated biological characteristics is required to be furthered. mei (1) conveyed air from experiment needs to be filtered; (2) particles should be uniformly delivered. j o u r n a l p r e -p r o o f experiments to analyzed the particle are useful for understanding the motion law of it. however, it is difficult to massively measure the characteristic of nano-scale particles. the tracer gas method is also a common method in analyzing the pollution diffusion and airflow patterns. tracer gas can be mixed with air without any changes and it can be easily detected because of special physical characteristics. helium, nitrogen, argon and carbon dioxide are always chosen to carry out the experiment as a tracer gas. gao, et.al [102] combined the use of experiment and cfd method to study airborne transmission in different flats of a high-rise building and to verify their simulation, the data of tracer gas experiment from denmark aalborg university [103] is used. the analysis of this work is comprehensive by illustrating the transmission mechanism of the airborne virus and how to control virus transmission in a high building based on this investigation is needed to be furthered. to investigate airborne transmission between horizontal adjacent units, wu, et.al [104] analyzed influence factors of transmission route especially the contribution of wind force and thermal buoyancy force and found from the result that the wind force is the main driving force to affect the inter-unit dispersion. the experiment conducted in this work is conducted in a slab-type building in hongkong, sf 6 was used as the tracer gas and injected by the air samples; co 2 was used to calculate the ventilation rate and monitored by tsi q-trak and co 2 sensor. although the spread risk may be overestimated in the analysis because the crack of the door and windows can cause the pathogens aerosol deposit, this work still provides a valuable study in identifying the possible transmission route of the airborne. ai, et.al [105] used a tracer gas (no 2 ) experiment to examine the characteristics of airborne transmission of the exhaled droplet between two people in an experimental room. two manikins were used to represent an exposed people and an infected people; air velocity was measured by the swema 3000 omnidirectional anemometer; pt100 sensor was used to monitor the air temperature; to test the tracer gas concentration, a faster concentration meter (fmc) and innova multi-gas sampler and monitor are used. this work has indicated an interaction between exhaled gas and supply flow and analyzed the impact of these factors on infection risk for an exposed person facing an infectious person. although the experiment carried out in this work was based on a steady-state condition without taking the impact factor of time into consideration, it provided an effective method for researches afterward. (1) culturing and filtering the suitable bacteria; (2) aerosolizing the bacteria particles and conveying into measuring environment; (3) analyzing the airborne transmission of e. coli by using pcr. and the flow chart given by them is shown below in fig. 7 : fig.7 experiment process of tracing bacteria [110] it will be more persuasive if this process can be carried out in an experiment of researches by using the tracer gas method or particle experiment. however, it will also increase the risk in conducting experiments if the bacteria or virus are highly infectious. overall, both the particle experiment and tracer gas experiment can help people understand the process of pathogen transmission, moreover, it provides crucial information for cfd users. on the one hand, the information including experimental data can be used as boundary conditions in cfd simulation; on the other hand, the results of the experiment can be quantitively or qualitatively verified to ensure the accuracy of cfd simulation. therefore, designing an effective experiment in analyzing pathogen transmission is necessary, it makes the simulation result more convincing. j o u r n a l p r e -p r o o f transmission of pathogens can be different in various spaces and when the epidemic outbreaks caused by infectious pathogens, hospitals will become a high-risk place and may lead to a second infection. how to control the pathogen in hospitals by using an effective ventilation system becomes a great concern. kao et.al [111] [112] they used the tracer gas no 2 to replace the viral gas emitted from the patient and simulated three cases under different volumes of supplied air and exhausted air, the simulation results presented the diffusion process of tracer gas as in fig. 9 : fig. 9 the simulation of tracer gas diffusion [112] in the same year, this research group studied a similar topic by using the tracer gas and cfd method. in this analysis, the stack effect of high rise building on airflow is considered and the simulation model is based on the general hospital k in korea as shown in fig.10 . fig. 10 the prince of wales hospital and the simulation model of it [113] they have simulated the spread of tracer gas in the wards of both on the lower floor (5f) and higher floor (15f) to demonstrate the stack effect. some of the simulation results are shown as shown in fig. 11 : figure. 11 simulation results of the tracer gas transmission in wards of different floors [113] j o u r n a l p r e -p r o o f these researches above mainly investigated pathogen transmission inside the hospital and they are meaningful in protecting patients and hospital staff. however, not only pathogen transmission inside the hospital is dangerous, but the pollutant emission from the hospital is also a great concern for public health. chang et.al [114] by using cfd modeled the atmospheric environment out the hospital and simulated the spread of the viral (sars) gas emitted from the hospital. the mesh model of simulation is shown in fig. 12 : fig. 12 mesh model of simulation [114] this model was generated by tetrahedral grids; the wind velocity as a boundary parameter was measured by the hot-film probe and anemometry equipment; 16 wind directions were considered in the calculation. moreover, in order to verify this model, tracer gas was used in the experiment model with a 1:50 scale. the simulation result below in fig. 13 respectively shows the concentration contour of pollutant gas at both the height of the roof chimney (right) and 1.5m (left) above the ground. fig. 13 diffusion of pollutant gas emitted from hospital [114] by the simulation results, they indicated that both the maximum concentration and mean concentration of pollutant gas in small and would not affect residents' health. however, when a large number of sars patients were arranged in the hospital, it is still a bit risky for people who actives in the high-concentration area on the ground level. research works above were mainly focused on the airflow pattern or impact of ventilation on pathogen transmission. however, cross-infection frequently happened in hospitals and should be paid attention to in case studies of pathogen transmission. based on eulerian-lagrangian method, a case study proposed by wang, et.al [115] has illustrated that the sneezing process from a virus carrier is ventilation is easier to be controlled, hence, it is necessary to ensure safety when emitted the viral gas from the exhausted system from the hospital. without professional medical equipment, the buildings with high population density such as residential buildings, commercial buildings and campus buildings are in higher infection risk. yang, et.al [116] studied natural ventilation in teaching buildings by using cfd method. in their investigation, phoenics with rans model was used to simulate the ventilation; the simple algorithm was used to calculate and presto scheme was used to staggered the pressure interpolation; the wind profile at inlet boundary of the simulation was determined by the equation of ashrae [117] as: 0.22 () ref u y y uh     (27) through the simulation, they indicated that the ventilation of the teaching building with a "line-type" corridor is better than that of the inside corridor; they have also presented an optimization design for better ventilation in teaching buildings by determining the best wind angle. moreover, cuce, et.al [118] studied the natural ventilation in school buildings based on its working principles and limitation of passive ventilation; in a crowded room, the concentration of volatile organic substances generated by human skin oil is high, xiong, et.al it can be observed from simulations that particles will spread in flushing because of the turbulence generated by the high speed of flowing water. more, it was obtained that 40%~60% of particles can reach above the toilet seat. the research of this work is meaningful and it was indicated that before flushing, laying down the lid is useful for preventing the virus transmission. more, washing the seat of the toilet is necessary because the floating virus may deposit on the surface of it. this research group has also analyzed the movement of a virus-laden particle in the process of urinal flushing [122] . without the prevention, over 57% of particles can escape from the urinal and the particle can reach the highest position of 0.84m at only 5.5s . so it is mandatory to wear a mask in public to reduce infection risk. furthering this study about virus transmission in the squat toilet by applying the method j o u r n a l p r e -p r o o f proposed in this work is important because, in many places such as china, the use of the squat toilet is higher than that of the sitting toilet in public. some investigations of cfd simulations of ventilation or pathogen transmission in the building environment are summarized below in tab. 6: it can be obtained from these investigations: (1) ventilation is one of the most effective methods to control the pathogens transmission and the reasonable arrangement of the ventilation system is necessary. (2) the effect of the stack effect should be considered when analyzing the ventilation in high-rise buildings. (3) rooms with infected patients need to be diluted with plenty of fresh air. traffic vehicles are also dangerous when there are infectious patients. under the high personnel density and weak ventilation system, it is difficult to control the pathogen such as the airborne virus. according to this problem, more and more researchers investigated airflow in various kinds of vehicles by using cfd methods. (1) two particles collisions are mainly considered; (2) the velocity distribution of each particle exists independently; (3) the external force does not affect the dynamic behavior of the local collision. there are various models that can be used in the simulation of lbm and these models can be defined by the layout of lattice, some models which are in common use are shown in fig. 17 (2d) and face masks have been used to prevent virus transmission and it is necessary for the epidemic situation. li [155] simulated the aerodynamic behavior of a gas mask which consists of two filter layers. fig. 19 : fig. 19 grid model of the gas mask (left) and the flow field of simulation (right) [155] this research indicated that the design of the mask such as the hole properties is important: larger hole area and greater hole distribution lead to a lower pressure drop, a smaller dead zone, and so on. theoretical analysis was mainly studied in this work and it has also provided a reference in designing a sufficient mask. dbouk, et.al [156] analyzed the role of the mask in preventing the droplet transmission by utilizing openfoam with a combination of the use of turbulence model and porous model. in the simulation model, the mask fitting to the face was considered which is shown as in fig.20 : turbulent flow in the atmosphere is unsteady due to the changing weather and it is difficult to measure the airborne transmission in the atmospheric environment directly. although aerodynamics models of airborne transmission based on cfd method have been greatly developed, it is still a big challenge for applying them to the large-scale environment. seo, et.al [159] presented a method based on meteorological information from web-system that can help for solving this problem. this research group analyzed the relationship between foot-and-mouth disease (fmd) spread and hourly wind in anseong. moreover, they collected the infection data and built a model by using the gis method. then, they used a code division multiple access (cdma) to send the weather data to a weather data acquisition server (wdas) in every 10 minutes and interlock the data with geographical information. the openfoam code was used to simulate the spread of the airborne virus the simulation result can well describe the virus transmission. the process of the cfd simulation based on web-based forecasting system can be described as below in fig. 22 : fig. 22 detailed process of cfd simulation based on web-based forecasting system the web-based forecasting system has been widely used in various cases such as flooding (li, j o u r n a l p r e -p r o o f et.al [160] ), tourism demand (song, et.al [161] ), monitoring of marine pollution (kulawiak, et.al [162] ), etc. however, there are few studies about pathogen transmission based on combing the web-based forecasting system and cfd method. hence, more databases of pathogen transmission and meteorological information are needed to develop the web-based forecasting system in the analysis of pathogen transmission. from investigations summarized in this review, it can be found that ventilation is one of the most effective methods to control pathogen transmission in the air. different environments require different ventilation systems, the building environment such as teaching building and residential building and the natural ventilation method is the main way to dilute the concentration of the pathogen. however, in high-risk zones such as hospitals, not only the reasonable ventilation of indoor is required, but also the infectious risk due to emission needs to be considered. besides, pathogen transmission in j o u r n a l p r e -p r o o f journal pre-proof different vehicles is distinct, a proper strategy of ventilation is necessary for transportation especially the airplane and high-speed train with an enclosed environment. this review also presented some advanced methods for cfd application on pathogen transmission according to recent investigations as: (1) lbm simulation allows researchers to investigate pathogen transmission from the mesoscale level; (2) based on the porous media model, researchers can better analyze the transport of pathogens in complex media, such as medical masks, human organs, etc. (3) web-based forecasting system can be combined with the cfd method to analyze the transmission of infectious pathogens in the atmospheric environment and predict the cross-regional transmission of pathogens. covid-19): dashboard data last updated: 2020/8/10, 3:06pm cest phagocytic cells contribute to the antibody-mediated elimination of pulmonary-infected sars coronavirus immunobiology of ebola and lassa virus infections clonal vaccinia virus grown in cell culture as a new smallpox vaccine limited airborne transmission of h7n9 influenza a virus between ferrets violent expiratory events: on coughing and sneezing sneezing and asymptomatic virus transmission on coughing and airborne droplet transmission to humans 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for fluid dynamics and beyond pore-scale modelling of dynamic interaction between svocs and airborne particles with lattice boltzmann method lattice boltzmann method simulation of svoc mass transfer with particle suspensions modeling of dynamic deposition and filtration processes of airborne particles by a single fiber with a coupled lattice boltzmann and discrete element method lattice boltzmann method and rans approach for simulation of turbulent flows and particle transport and deposition multi-block lattice boltzmann simulations of solute transport in shallow water flows large-scale oil spill simulation using the lattice boltzmann method, validation on the lebanon oil spill case lattice boltzmann simulations of anisotropic permeabilities in carbon paper gas diffusion layers drag correlation for dilute and moderately dense fluid-particle systems using the lattice boltzmann method lattice boltzmann simulation of liquid water transport in microporous and gas diffusion layers of polymer electrolyte membrane fuel cells an immersed boundary-lattice boltzmann model for simulation of malaria-infected red blood cell in micro-channel aerodynamic behavior of a gas mask canister containing two porous media on respiratory droplets and face masks 3-d numerical simulation of main sieve diaphragm with three types passageway design in a gas mask canister the role of porous media in modeling fluid flow within hollow fiber membranes of the total artificial lung web-based forecasting system for the airborne spread of livestock infectious disease using computational fluid dynamics a web-based flood forecasting system for shuangpai region developing a web-based tourism demand forecasting system interactive visualization of marine pollution monitoring and forecasting data via a web-based gis the authors are grateful for the research support received from applied basic the authors declared that they have no conflicts of interest to this work as: we declare that we do not have any commercial or associative interest that represents a conflict of interest in connection with the work submitted.j o u r n a l p r e -p r o o f key: cord-263801-01goni72 authors: sobral, marcos felipe falcão; duarte, gisleia benini; da penha sobral, ana iza gomes; marinho, marcelo luiz monteiro; de souza melo, andré title: association between climate variables and global transmission of sars-cov-2 date: 2020-08-10 journal: sci total environ doi: 10.1016/j.scitotenv.2020.138997 sha: doc_id: 263801 cord_uid: 01goni72 in this study, we aimed at analyzing the associations between transmission of and deaths caused by sars-cov-2 and meteorological variables, such as average temperature, minimum temperature, maximum temperature, and precipitation. two outcome measures were considered, with the first aiming to study sars-cov-2 infections and the second aiming to study covid-19 mortality. daily data as well as data on sars-cov-2 infections and covid-19 mortality obtained between december 1, 2019 and march 28, 2020 were collected from weather stations around the world. the country's population density and time of exposure to the disease were used as control variables. finally, a month dummy variable was added. daily data by country were analyzed using the panel data model. an increase in the average daily temperature by one degree fahrenheit reduced the number of cases by approximately 6.4 cases/day. there was a negative correlation between the average temperature per country and the number of cases of sars-cov-2 infections. this association remained strong even with the incorporation of additional variables and controls (maximum temperature, average temperature, minimum temperature, and precipitation) and fixed country effects. there was a positive correlation between precipitation and sars-cov-2 transmission. countries with higher rainfall measurements showed an increase in disease transmission. for each average inch/day, there was an increase of 56.01 cases/day. covid-19 mortality showed no significant association with temperature. • first study covering all countries affected by covid-19 verifying the association with climate variables. • negative association between country average temperature and covid-19 infections. • positive associations between country precipitation and covid-19 infections. • no association between deaths and country temperature or precipitation. a b s t r a c t a r t i c l e i n f o this is the third time in less than two decades that the world authorities are facing an epidemic with high transmissibility, caused by subtypes of a coronavirus (munster et al., 2020; gorbalenya, 2020) . the first epidemic occurred during [2002] [2003] in guangdong province, china. the disease was termed 'severe acute respiratory syndrome' (sars) and was caused by a newly identified coronavirus that was named sars coronavirus (sars-cov) (lin et al., 2006) . sars-cov infected 8000 individuals from several countries and resulted in 774 deaths. the second epidemic occurred in 2012 in the middle east. this disease was termed 'middle east respiratory syndrome' and was caused by a new virus called mers coronavirus (mers-cov). mers-cov infected 2494 individuals and resulted in around 860 deaths (munster et al., 2020) . at the end of 2019, a third epidemic occurred. this was caused by another new type of coronavirus designated by the world health organization as sars-cov-2. the resultant disease was named 'coronavirus disease' ; the disease is now a worldwide pandemic (gorbalenya, 2020) . the recently emerged sars-cov-2 was first identified in the city of wuhan, hubei province, china. the virus infects humans and a variety of animals, mainly pigs and bats (velavan and meyer, 2020) . infection results in a spectrum of clinical manifestations, which are mainly respiratory, ranging in severity from benign to lethal, and it is sometimes asymptomatic (velavan and meyer, 2020; fehr and perlman, 2015) . in an attempt to understand these epidemics, studies have examined factors that could influence the spread of coronaviruses (chan et al., 2011) . in general, three factors affect the epidemiology of communicable diseases: the agent of transmission, the host, and the environment (lin et al., 2006) . historically, the occurrences of sars were partly associated with environmental factors (lin et al., 2006) . an ecological study conducted in china found that air pollution was associated with lethality in individuals affected by sars. this was attributed to the fact that short-or long-term exposure to certain pollutants can compromise lung function (cui et al., 2003) . another environmental factor was air temperature. lin et al. (2006) identified, for the first time, that the incidence of sars was 18 times higher at lower air temperatures than at higher temperatures. the authors reported that respiratory system diseases are more common in colder environments and that the virulence of agents deteriorates at higher climatic temperatures, as they may not be able to withstand the environmental changes. in addition, they pointed out that the transmissibility of sars-cov, in terms of climatic fluctuations, is similar to that of the influenza virus. furthermore, the incidence of influenza increases significantly with low temperatures and high relative humidity (park, 2020) , indicating that climatic factors can significantly affect viral transmission. in the case of sars-cov-2, meteorological factors seem to influence the spread of the virus (oliveiros et al., 2020; bao et al., 2016) . oliveiros et al. (2020) identified that the speed of transmission was positively correlated with temperature and correlated with humidity. thus, it is expected that if the temperature rises to 20°c, transmission rates increase by an average of 1.8 days. regarding temperature and mortality rate, a study conducted in four chinese cities found that colder temperatures had a greater effect on mortality (bao et al., 2016) . this is in contrast to the results of the study by li et al. (2019) , which showed that both cold and heat can adversely impact the mortality resulting from respiratory syndromes. on the basis of the assumption that different climatic conditions play a significant role in the course of covid-19, it is essential to identify associations between environmental factors, such as average, maximum, and minimum temperatures; precipitation; and demographic density, and sars-cov-2 transmission and covid-19 mortality in humans. data for the period from december 1, 2019 to march 30, 2020 were collected. for meteorological variables, weather station data were extracted from the national oceanic and atmospheric administration (noaa) database. daily data from meteorological stations were segregated by country, and the following variables were recorded: precipitation, average temperature, maximum temperature, and minimum temperature (noaa, 2020). daily averages of each meteorological variable for the different countries were calculated. finally, data on daily infection and death rates were extracted from world health organization reports (who, 2020). the demographic density of each country was used as a control variable, with data obtained from the food and agriculture organization and world bank population estimates for the year 2018 (world bank, 2020). the country's time of exposure to the epidemic was calculated from the temporal distance, in days, between the first case registered in the territory and the time of study. a summary of the variables is provided in table 1 . to analyze the association between the number of cases of and deaths from covid-19 and climatic aspects, we used eq. (1), as estimated by a panel data strategy (wooldridge, 2002) : where y it is the dependent variable (total number of cases of sars-cov-2 infections or total number of deaths from covid-19) for 249 countries "i" over the period "t" from december 1, 2019 to march 30, 2020; σ is a constant; u i is the control for specific characteristics of the countries that are fixed over the analyzed period; and x it is a vector that includes all explanatory variables of the model, including the variable of interest, that is, the mean temperature. in addition, we included other controls that may be related to the disease, such as average rainfall and the country's time of exposure to the epidemic. we included as binary variables d t , which captures specific effects associated with the months of january and february, and ε it , which is the error term of this equation that includes all factors that are associated with y it and are not included in the equation. the advantage of this strategy in relation to a traditional ordinary least squares estimate is that we can control for some country-specific factors that are fixed in time and associated with the number of deaths associated with sars-cov-2 infection. two specific outcomes measures were considered. for the first, we analyzed the influence of climatic variables on sars-cov-2 infections, and for the second, we analyzed the influence of climatic variables on covid-19 mortality. three estimates were tested for each outcome and are shown in fig. 1 . the first included only the average temperature; the second included the average temperature, minimum temperature, maximum temperature, precipitation, and the country's time of exposure to the epidemic; and the third included the average temperature, minimum temperature, maximum temperature, precipitation, the country's time of exposure to the epidemic, population density, and a variable to capture the specific month effects (complete specification). table 2 shows the results of correlation analysis between the number of confirmed covid-19 cases and the average temperature by country. in the first estimated model, there is a negative correlation between the two variables. the significance of this relationship remains even after the inclusion of additional variables such as maximum and minimum temperatures (averages) and time of exposure to the disease. even with the complete specification that includes two binary variables capturing specific effects for the months of the year and controlling for population density, the results suggest that an increase in temperature is associated with a decrease in the number of infections. the coefficients shown in table 2 cannot measure causality. there are several other factors that can affect the variable of interest, on which we do not have information, such as the number of beds and the patients' respective levels of social isolation. however, an association was observed between the climate and the number of covid-19 cases. these models appear to be quite robust, particularly after the incorporation of controls such as additional climate variables and also month fixed effects. table 3 shows the results of correlation analysis between covid-19 mortality and climatic variables. for this outcome measure, there were no significant associations between the coefficients and mortality or average temperature. it is possible that factors other than climate are related to mortality. in the first estimate, we evaluated only the relationship between covid-19 mortality rates and the average temperature by country, which was significant. in the second estimate, we included the average, minimum, and maximum temperatures as well as the country's time of exposure to the disease and did not identify any significant association. in the last estimate, in addition to the controls already included in the previous specification, we also incorporated binary variables to capture any effects that were specific to this period. however, no significant correlation was identified between covid-19 mortality rates and temperature. several factors can influence sar-cov-2 transmission, including environmental variables, population density, and medical care . this study aimed to identify the associations between environmental variables and sars-cov-2 transmission/covid-19 mortality. a negative correlation was identified between temperature and the number infections. although it is known that the influence of temperature on human health can vary between countries and even regions (hajat and kosatky, 2010) , the findings of this study are in agreement with the current literature in that temperature influences the transmission of viruses that cause respiratory syndromes, such as the influenza virus (park, 2020) and sars-cov-2 (ma et al., 2020) . by investigating the relationship between temperature and respiratory diseases, studies have indicated that sars-cov and the influenza virus survive only under certain climatic conditions and that their transmissibility is sensitive to rising temperatures (jaakkola et al., 2014; chan et al., 2011) , similar to the transmissibility of sars-cov-2 . the influenza virus is more transmissible at lower temperatures (lowen and steel, 2014) because cold weather results in the weakening of host immunity, increasing susceptibility to infection (kudo et al., 2019) . considering that the transmissibility of coronaviruses is similar to that of the influenza virus (lin et al., 2006) , it can be assumed that these mechanisms also apply to the transmission of sars-cov-2 . in the model in which we considered only the average temperature, the observed correlation indicated that for every one degree fahrenheit increase in temperature, there was a reduction in the number of infections by 1.44 cases/day. under the composite model (estimate 3 of outcome measure 1), the association was stronger in that there was a decrease in the number of infections by 6.40 cases/day for each degree increase in temperature. the second finding of this study was the significant association between mortality and average temperature, which was not maintained when other variables were added, indicating that non-climatic variables may be related to covid-19 mortality. this finding differs from the findings of ma et al. (2020) , who stated that temperature and covid-19 mortality are negatively associated. one possible reason for the conflicting results is the limited geographical scope of the study by ma et al., which focused only on china and its climate. our study included data from a range of countries and climatic regions. environmental factors that influence the relationship between temperature and mortality, such as latitude (bao et al., 2016) ; humidity (jaakkola et al., 2014; kudo et al., 2019) ; air pollution (cai et al., 2007) ; and sociodemographic factors, such as age, sex, and income (bao et al., 2016) , have been reported. chan et al. (2011) reported that people who live at low latitudes have a relatively weak adaptive capacity to cold and a strong adaptive capacity to heat, and the reverse has also been shown. high humidity, which is associated with low temperatures, is an important factor in the transmissibility of the influenza virus, either by conserving virulence or weakening the host by cooling the body or drying the respiratory tract (jaakkola et al., 2014) . a study reported that temperature and humidity are associated with a higher risk of covid-19 . therefore, although humidity was not considered in our research because of the lack of information on this variable from some meteorological stations, precipitation seems to be an important factor that must be considered. we found that there was a positive correlation between precipitation and sars-cov-2 transmission, showing that for each 1-in. increase in precipitation/day, there was an increase of 56.01 cases/day. another result concerns the country's time of exposure to sars-cov-2. as expected, this variable also showed a positive correlation, showing that for each additional day of exposure there was an average increase of 15.73 cases/day. this finding is consistent with the behavioral evidence on sars-cov-2 transmission, that is, after community infection, transmission follows the same geometric progression (correia et al., 2020) . it is important to mention that our study only interpreted the significance of the coefficients and not their magnitude because of the probable existence of endogeneity in the estimated relationships, considering that a series of regressors are associated with temperature and disease mortality at the same time. this is the first global study covering all countries affected by covid-19. we examined the associations between climatic variables and sars-cov-2 transmission and covid-19 mortality. the findings showed a negative correlation between a country's average temperature and the number of covid-19 cases, the absence of a correlation between mortality and the average temperature, and a positive correlation between the country's time of exposure to the virus and the number of cases. in addition, this study reported that precipitation as an important factor in the transmissibility of the virus. this research provides important information that can inform the decisions of local and global health authorities. as climatic variations are associated with the transmissibility of sars-cov-2, new policies to reinforce health systems or social isolation methods can be adopted, depending on temperature and precipitation patterns. as a limitation, we highlight the absence of humidity data, in view of its important role in the virulence of respiratory syndromes. however, because of the current data restrictions, this factor could not be considered, and it should be included in future studies. we also suggest that future studies focus on micro-regions to capture temperature patterns and include variables related to solar radiation. the authors declare that they have no conflict of interest. the influence of temperature on mortality and its lag effect: a study in four chinese cities with different latitudes influence of meteorological factors and air pollution on the outbreak of severe acute respiratory syndrome the effects of temperature and relative humidity on the viability of the sars coronavirus os cirurgiões e a pandemia do covid-19. revista do colégio brasileiro de cirurgiões air pollution and case fatality of sars in the people's republic of china: an ecologic study coronaviruses: an overview of their replication and pathogenesis severe acute respiratory syndrome-related coronavirus: the species and its viruses -a statement of the coronavirus study group heat-related mortality: a review and exploration of heterogeneity decline in temperature and humidity increases the occurrence of influenza in cold climate low ambient humidity impairs barrier function and innate 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authors: chen, l.-w. antony; chien, lung-chang; li, yi; lin, ge title: nonuniform impacts of covid-19 lockdown on air quality over the united states date: 2020-07-21 journal: sci total environ doi: 10.1016/j.scitotenv.2020.141105 sha: doc_id: 311827 cord_uid: jfdlb2g8 abstract most of the state governments in united states (u.s.) issued lockdown or business restrictions amid the covid-19 pandemic in march 2020, which created a unique opportunity to evaluate the air quality response to reduced economic activities. data acquired from 28 long-term air quality stations across the u.s. revealed widespread but nonuniform reductions of nitrogen dioxide (no2) and carbon monoxide (co) during the first phase of lockdown (march 15–april 25, 2020) relative to a pre-lockdown reference period and historical baselines established in 2017–2019. the reductions, up to 49% for no2 and 37% for co, are statistically significant at two thirds of the sites and tend to increase with local population density. significant reductions of particulate matter (pm2.5 and pm10) only occurred in the northeast and california/nevada metropolises where no2 declined the most, while the changes in ozone (o3) were mixed and relatively minor. these findings are consistent with lower transportation and utility demands that dominate no2 and co emissions, especially in major urban areas, due to the lockdown. this study provides an insight into potential public health benefits with more aggressive air quality management, which should be factored into strategies to reopen the u.s. and global economy. the ongoing pandemic of coronavirus disease has created challenges for governments around the world to balance public safety and economy. in the u.s., following the national emergency declared by president trump on march 13, 2020, states and municipalities have issued various degrees of lockdown and/or stay-at-home policies suiting local specific conditions (lin et al., 2020) . such policies impact air quality through, most notably, declined "non-essential" transportation and energy consumption (le quéré et al., 2020) . among the criteria air pollutants (caps), the u.s. environmental protection agency (epa)'s national emissions inventory attributes 74% of nitrogen oxides (no x , sum of nitrogen dioxide [no 2 ] and nitric oxide [no] ) and 59% of carbon monoxide (co) emissions to on-and off-road traffic and electric generation (u.s. epa, 2016) . ambient levels of the two pollutants might be most affected by the lockdown, compared with primary pm 2.5 and pm 10 (particulate matter with aerodynamic diameters below 2.5 and 10 micrometers, respectively) of which only 10% and 4% result from traffic and electric generation. ozone (o 3 ) is formed in the atmosphere through photochemical reaction of no x and volatile organic compounds (vocs). reduced no x and vocs emissions could either lower or lift o 3 concentrations depending on the local photochemical regime (sillman and he, 2002) . the unprecedented situation of covid-19 pandemic creates an opportunity to assess the contribution of transportation and commercial activities to local air quality and the potential outcome of more stringent emission regulations. such assessments have been carried out for many large cities around the world (kerimary et al., 2020; nakada and urban, 2020; sharma journal pre-proof j o u r n a l p r e -p r o o f 4 et al., 2020; tobías et al., 2020) , but the evidence in the us is lacking. this paper analyzed data from long-term air quality monitoring stations across the u.s. and estimated reductions of caps during the first phase of extensive lockdown. findings can inform future modeling studies that attempt to capture policy outcomes by simulating state-wise emission reductions. such information is also important for the post-pandemic air quality management. the epa national core (ncore) network tracks long-term trends of caps across the u.s. (scheffe et al., 2009) . daily ncore data for january 1, 2020 -april 30, 2020 were acquired from airnowtech (https://www.airnowtech.org/) and cross-verified with those reported to the u.s. epa airdata website (https://www.epa.gov/outdoor-air-quality-data). the six weeks or 42 days between march 15 and april 25, 2020 was designated as the first-phase lockdown period (p1), as many states began restricting businesses and schools in the week of march 15 but relaxed the restrictions somewhat coming into may 2020 (lin et al., 2020; raifman et al., 2020) . a reference period deemed business as usual between january 25 and march 7, 2020 (p0) was also selected, and the relative concentration of a pollutant i, i.e., [i] year should not affect the inter-annual comparison because those effects are mostly canceled in the p1/p0 ratio. p1 and p0 with more than one third of missing data (i.e., >14 days out of the 42-day period) were excluded. for the 28 sites selected, [ ] ′ resulted from at least 2 years of valid data. to estimate the confidence interval of %, a bootstrapping procedure (mooney and duval, 1993 ) based on 12,000 resampling/recalculation of the data were carried out using the matlab® statistics toolbox. the type i error was set to 5%. twenty-eight ncore sites with 2017-2020 no 2 , o 3 , and pm 2.5 data mostly available through the end of april 2020 were identified for this analysis. these sites are in or proximate to 28 different metropolises among 23 states. co and pm 10 were also reported from 21 and 13 of the 28 sites, respectively. there are also significant associations among ∆no 2 %, ∆co%, and ∆pm 2.5 % (see table s2 ). for the top 9 sites in table 1 with the most reductions in no 2 concentration, all the other pollutants except o 3 also declined. as a secondary pollutant, o 3 did not show a clear pattern across the country, with significant increases and decreases observed at 2 and 7 sites, respectively, for the lockdown period. the lockdown appeared to lower no 2 and co more broadly and significantly than pm, consistent with declining mobile and power plant emissions and similar to observations in europe (sicard et al., 2020; tobías et al., 2020) . on a national scale both pm 2.5 and pm 10 are (komenda, 2020) . this is in contrary to states such as north dakota and wyoming where schools were closed but businesses remained open (no stay-at-home order). significant co reductions nonetheless were observed at bismarck, nd and cheyenne, wy during the lockdown (table 1 ). there could also be an urban-rural contrast in how the lockdown affects air quality, as fewer non-essential commercial activities occur in rural and suburban areas than in urban centers. enforcing such policies in rural areas is also more difficult. population density of the zip code where a site is located serves as a surrogate of urbanization and is plotted against ∆no 2 % in population density does explain the different ∆no 2 % between the two oh sites and between the two md sites that bore a uniform lockdown policy within the respective state. in both cases, no 2 reduction increased with the local population density (figure 1) sommer et al. (2020) . the lockdown or stay-at-home orders issued by the u.s. government to counter the covid-19 pandemic has nonuniformly impacted air pollution in the u.s. more consistent no 2 and co declines than other pollutants coincide with reduced transportation and utility demands, while inter-site differences reflect not only the local lockdown policy but also population density. the first phase of lockdown in general affected urban more than suburban air quality. although these effects are temporary, public health benefits from more aggressive air quality management should be considered in the recovery efforts, such as accelerating the transition into cleaner fuels and mass transportation. black and organic carbon emission inventories: review and application to california the impact of covid-19 partial lockdown on the air quality of the city of rio de janeiro assessing air quality changes in large cities during covid-19 lockdowns: the impacts of traffic-free urban conditions in almaty a comparative study of ozone production in five us metropolitan areas covid-19: sisolak bans gatherings of 10 or more people temporary reduction in daily global co 2 emissions during the covid-19 forced confinement statewide stay-at-home directives on the spread of covid-19 in metropolitan and nonmetropolitan counties in the united states sisolak orders statewide closure of nonessential businesses, including casinos, following in footsteps of other states. the nevada independent bootstrapping: a nonparametric approach to statistical inference covid-19 pandemic: impacts on the air quality during the partial lockdown in são paulo state covid-19 us state policy database the national ambient air monitoring strategy: rethinking the role of national networks effect of restricted emissions during covid-19 on air quality in india some theoretical results concerning o 3 -no x -voc chemistry and no x -voc indicators traffic is way down because of lockdown, but air pollution? not so much utah governor asks, salt lake city mayor orders residents to stay home to slow the spread of the coronavirus. the salt lake tribune changes in air quality during the lockdown in barcelona (spain) one month into the sars-cov-2 epidemic national emission inventory (nei) 16) or1 portland -11 (-33, 15) -21 (-19, 74) -6 (-12, 26) wa1 seattle -11 the authors thank staffs from sailbri cooper inc. for collecting and organizing the ncore air quality data, and support from school of public health, university of nevada, las vegas for publishing the paper. key: cord-275565-xerr4vki authors: kumar, manish; kuroda, keisuke; patel, arbind kumar; patel, nidhi; bhattacharya, prosun; joshi, madhvi; joshi, chaitanya g. title: decay of sars-cov-2 rna along the wastewater treatment outfitted with upflow anaerobic sludge blanket (uasb) system evaluated through two sample concentration techniques date: 2020-09-15 journal: sci total environ doi: 10.1016/j.scitotenv.2020.142329 sha: doc_id: 275565 cord_uid: xerr4vki for the first time, we present, i) an account of decay in the genetic material loading of sars-cov-2 during upflow anaerobic sludge blanket (uasb) treatment of wastewater, and ii) comparative evaluation of polyethylene glycol (peg), and filtration as virus concentration methods from wastewater for the quantification of sars-cov-2 genes. the objectives were achieved through tracking of sars-cov-2 genetic loadings i.e. orf1ab, n and s protein genes on 8th and 27th may 2020 along the wastewater treatment plant (106 million liters per day) equipped with uasb system in ahmedabad, india. peg method performed better in removing materials inhibiting rt-qpcr for sars-cov-2 gene detection from the samples, as evident from constant and lower ct values of control (ms2). using the peg method, we found a reduction >1.3 log10 in sars-cov-2 rna abundance during uasb treatment, and the rna was not detected at all in the final effluent. the study implies that i) conventional wastewater treatment systems is effective in sars-cov-2 rna removal, and ii) uasb system significantly reduces sars-cov-2 genetic loadings. finally, peg method is recommended for better sensitivity and inhibition removal during sars-cov-2 rna quantification in wastewater. wastewater-based epidemiology (wbe) has already proved its capability as a tool of environmental surveillance of epidemic and pandemic in a given community through viral load detection in the wastewater, shredded both from symptomatic and asymptomatic covid-19 patients (bivnis et. al., 2020; xagoraraki and o'brien, 2020; choi et al. 2018; yang et al., 2015; hellmér et al., 2014; asghar et al., 2014; ahmed et al., 2020a , hata et al., 2020 wölfel et al., 2020a; zhang et al., 2020; randazzo et al 2020) . the second quarter of 2020 has been exceptional in discovering several new knowledge pertaining to sars-cov-2 genetic material loading, its analytical methods, and various strong implications pouring around the world (ahmed et al., 2020a; bar-or et al., 2020; haramoto et al., 2020; la rosa et al., 2020; medema et al., 2020; nemudryi et al., 2020; randazzo et al., 2020a; rimoldi et al., 2020; wurtzer et al., 2020a; wurtzer et al., 2020b kumar et al., 2020a . while most of the studies could explicitly prove the correlation of sars-cov-2 genetic loading with the covid-19 patients in the area, some compared the methods to improve srs-cov-2 rna extraction (ahmed et al., 2020b) and some studies traced back the sars-cov-2 genes in the wastewater long before any covid-19 patient were declared, implying high early warning capability of wbe (randazzo et al 2020a , prevost,et al 2015 , lodder and husman 2020 , prussin et al 2020 , ahmed et al., 2020c , sherchana et al., 2020 . however, the great majority of the existing studies are based on analysis of raw wastewater only, or just a comparison of influent and final treated effluent samples from wastewater treatment plants (wwtps). thus, there still remains questions pertaining to: i) capability of conventional wwtps to reduce the abundance of sars-cov-2 rna, ii) better understanding of the protocol, virus j o u r n a l p r e -p r o o f journal pre-proof precipitation through peg and filtration which one is better methods for concentrating the samples before rna isolation. further, while in wbe surveillance is being accelerated in india upon phasing out of lockdown, several questions are raised around its capability owing to incomplete sewer systems, significant wastewater leak, high ambient temperature, open defecation, strong seasonality component, and common sewer overflow (cso) situations in india. overall, there are several apprehensions about infectivity through genetic material present in the wastewater become a pertinent question. these all warrants a study that can track the genetic loading after each wastewater treatment stage in indian settings and highlight the effects of wastewater treatment on rna decay of the corona virus. such study will help curing the commonly perceived fear of the commons pertaining to the effectiveness of wwtps. further, the number of confirmed cases in india has passed 0.5 million as of the last day of june, 2020 (ministry of health and family welfare, india) with >16000 official casualties. in gujarat province, which is a hotspot and our study site, the confirmed cases will soon reach to 25,000 in ahmedabad city. (ministry of health and family welfare, india) indicating the need of immediate attention. at this juncture keeping the pulse of wbe progression as mentioned above, we focused on three major objectives i.e.: i) tracking the conventional treatment system for genetic loading decay of sars-cov-2 along the treatment process and evaluate its effectiveness, ii) appraising the genetic loading reduction through upflow anaerobic sludge blanket (uasb) systems, and iii) comparing the performances between peg and filtration as virus concentration methods in terms of sars-cov-2 rna sensitivity and inhibition removal. we thus hereby present the first ever data pertaining to uasb performances in sars-cov-2 rna j o u r n a l p r e -p r o o f journal pre-proof removal; and comparisons of two most frequently used techniques of virus concentration in wastewater samples for sars-cov-2 rna detection. we collected wastewater samples on 8 and 27 may, 2020 from old pirana wwtp at ahmedabad, gujarat that receives wastewater of 106 million liters per day (mld), including the wastewater from hospitals treating covid-19 patients. confirmed cases of covid-19 patients in ahmedabad was 56,352 and 150,857 respectively on 7 th and 26 th may 2020 (kumar et. al., 2020a) . the wwtp employed upflow anaerobic sludge blanket (uasb) after the primary treatment of raw sewage water ( figure 1 ). three separate streams join three inlet chambers (7.5 m x 5 m x 2.5 m) that uses six grit chambers (10.2 m × 10.2 m x 1.0m) i.e. viral rnas were isolated from sewage samples using the following steps: precipitation of viral particle; viral rna isolation and quality checking of rna; rt-pcr analysis of viral rna for the presence of sars-cov-2. the procedure was followed as described in an earlier report with minor modifications (hjelmsø mh et al., 2017) . the sewage samples (50 ml) were centrifuged at 4500×g (model: sorvall st 40r, thermo scientific) for 30 min to remove the sludge particles. the supernatants were filtered with 0.22 micron filters (mixed cellulose esters syringe filter, himedia) to remove bacterial and eukaryotic cells. further each sewage filtrate was concentrated (for viral precipitation) using two methods: 1) using 96 well filter plate and 2) j o u r n a l p r e -p r o o f poly ethylene glycol (peg) method. for the first method filtrate was concentrated using the 96 well filter plate (acroprep tm advance 350 10k omega tm ; pall corporation) with a capacity to filter less than 10kd molecules and samples were concentrated 30 times for before rna isolation. for the second method, peg 9000 (80 g/l) (make: srl) and nacl (17.5 g/l) (make: vetec) were mixed in 25 ml filtrate and incubated at 10°c, 100 rpm (model: incu-shaker tm 10lr, benchmark) overnight. the next day the mixture was centrifuged at 13000×g (model: kubota 6500, kubota corporation) for 90 mins. after centrifugation supernatant was discarded and the remaining pellet was resuspended in 300µl rnase free water. this was further used as a sample for rna isolation. rna isolation was carried out using a commercially available kit ( quantitation of sars-cov-2 viral rna was carried out by real-time pcr with an instrument control), one negative control (from extraction run spiked with ms2), and no template control (ntc) were included. the real-time pcr thermal profile was a primary ung incubation step of 1 cycle of 25°c 2 minutes, 1 cycle of reverse transcription 53°c 10 minutes, 1 cycle of activation 95°c 2 minutes which was followed by 40 cycles of amplification including denaturation at 95°c for 03 seconds and extension 60°c for 30 seconds. interpretation of the result was performed by the applied biosystems interpretive software. in the process, the probes anneal to three specific sars-cov-2 target gene sequences: orf1ab, n protein, s protein, ms2 (internal process control). all control wells must pass for the real-time rt-pcr plate to be considered valid. if all genes show amplification then the sample will be considered as the positive. detailed procedures were carried out as described in the product manual and interpretations of results were analysed as instructed in manual. although there is no direct correlation of the c t value to copy numbers as the kit j o u r n a l p r e -p r o o f used for the detection is absent present assay but considering 500 copies of sars-cov-2 genes taken as positive control with c t values of average 26 for all the three genes i.e. orf1ab, n and s, the same was extrapolated to compare it with sample c t values and derive approximate copies of genes in the wastewater sample, using the well-established principle of 3.3 c t change corresponding to a 10-fold gene concentration change. in this semiquantitative assay, the amount of rna used as template was multiplied with the enrichment factor to derive copy numbers for each waste water sample i.e. the enrichment factor with peg method i.e. 80x and filtration methods (30x) was taken into the account to maintain the equivalence. we analyzed orf1ab, n protein genes and s protein gene from the raw wastewater, influent of uasb, effluent of uasb, water in the aeration pond, and the final effluents from wwtp old pirana after treatment by polishing pond, sampled on may 8 and may 27, 2020. the obtained amplification cycles (c t ) and concentrations of sars-cov-2 using peg for virus concentration are shown in table 1 , and those using filtration method in table 2 . the positive control sample had c t values of the three sars-cov-2 genes ranging 27.92 to 29.52, while the sars-cov-2 genes were not detected from the negative control sample. the limit of quantification (loq) of the overall method was defined as sample concentration equivalent to 1 copy per reaction tube, which was 1.7×10 2 copies/l. our results showed that peg was more suitable than filtration as a concentration method of sars-cov-2 rna in terms of sensitivity and inhibition removal. ms2 was added in each superior performance over filtration method in terms of sars-cov-2 rna sensitivity and inhibition removal. in the following sections, we evaluated sars-cov-2 rna reduction based on results with peg method. we observed a reduction of sars-cov-2 rna both during uasb treatment and during treatment at the aeration tank and the polishing pond. on may 8, all the samples were detected but inconclusive (only 1 out of 3 sars-cov-2 genes was positive) and/or not quantifiable (concentration below the loq of 1.7×10 2 copies/l). on may 27, on the other hand, raw wastewater and uasb inlet samples were detected above the loq at 1.8×10 3 copies/l and 3.5×10 3 copies/l, respectively. these sars-cov-2 rna abundance of raw wastewater in old pirana wwtp were comparable to those of untreated wastewater samples in istanbul, turkey (kocamemi et al 2020) infection density of surveyed catchment. on may 27, the sars-cov-2 rna concentration was reduced to a level with inconclusive detection after uasb treatment. when the loq of 1.7×10 2 copies/l was used as a maximum concentration after uasb, the viral reduction during uasb treatment was more than 1.3 log 10 . comparison of sars-cov-2 rna abundance during various wastewater treatment processes are provided in table 3 . the reduction of sars-cov-2 rna during wastewater treatment processes have been observed for treatments including secondary treatment (activated sludge/a2o/extended aeration) and tertiary treatment (decantation, coagulation, flocculation, sand filtration, disinfection and naclo/uv; randazzo et al 2020a, balboa et al 2020) in spain and an unspecified wastewater treatment process in paris (wurtzer et al 2020 , borchardt et al 2007 . in those studies, the log 10 reduction of sars-cov-2 rna was inferred to be 2 in wurtzer et al (2020) and from >0.1 to >0.8 in randazzo et al (2020) . in the present study, the resulting log 10 reduction of >1.3 during uasb was well within the ranges above. to our knowledge, this is the first report on sars-cov-2 rna during uasb treatment. in the case of sewage sludge digestion, anaerobic treatment has shown to be less effective in inactivation of poliovirus 1, echovirus 1 and rotavirus sa-11 in sludge (scheuerman et al 1991) . anaerobic wastewater treatment has been employed for treating variety of wastewaters, such as industrial, agricultural and municipal wastewater (mccarty 1981; mccarty and smith 1981) . therefore, reduction of sars-cov-2 rna during various anaerobic wastewater treatment, such as uasb, must be investigated in more details in the future. in the case of treatment at the aeration tank and the polishing pond, the sars-cov-2 rna was detected but inconclusive and/or not quantifiable in the aeration tank water, but the final effluents were negative with all three genes on both may 8 and may 27, potentially suggesting a reduction of sars-cov-2 rna in the aeration tank and the polishing pond. in wastewater treatment ponds, viruses are removed through various mechanisms, including adsorption, predation and sunlight inactivation (verbyla and mihelcic, 2015) . in the study j o u r n a l p r e -p r o o f site, significant degradation by sunlight and constant high temperature (~40 o c in average) in the polishing pond is very likely, but further study needs to be substantiated through high data resolution. in summary, we have successfully evaluated peg and filtration as concentration methods for sars-cov-2 rna detection. we also demonstrated the removal of sars-cov-2 during uasb treatment process. note that our results are based on small number of samples and semiquantitative analytical method, therefore our results must be substantiated through more thorough investigation in the future. we tracked the sars-cov-2 genetic loading i.e. orf1ab, n protein genes and s protein genes along the conventional treatment system outfitted with uasb system. we have found a gradual decrease in rna copies of sars-cov-2 from the raw wastewater to influent of uasb after primary treatment, effluent of uasb, aeration pond, and the final effluents after polishing pond at the study cite of 106 mld wwtp of pirana, ahmedabad, india. higher rna loading detected in the influent of 27 th may, 2020 owing to higher covid-19 active cases in ahmedabad than that on 8 th may, 2020 directly translated into higher decay along the treatment. on may 27, the sars-cov-2 rna concentration was reduced to a level with inconclusive detection after uasb treatment owing to a reduction >1.3 log 10 . to our knowledge, this is the first report on sars-cov-2 rna during uasb treatment, yet a detailed research pertaining to the reduction of sars-cov-2 rna during various anaerobic wastewater treatment, such as uasb, is further required. as we could not detect any genes j o u r n a l p r e -p r o o f in the final effluents on both may 8 and may 27, a remarkable reduction of sars-cov-2 rna in the aeration pond followed by polishing pond is evident. among the concentration methods of wastewater sample, our results explicitly indicated that peg has an advantage over filtration in terms of sensitivity and inhibition removal for rt-qpcr run and gene detection. we conclude this on the basis of c t values of ms2 which was nearly constant for peg method but varying in nature with filtration method, particularly for the raw wastewater samples. it implies that filtration method was not capable of sufficiently removing sample matrix in the sample water, and thus resulted in greater inhibitory effect of rt-qpcr than peg method. overall, implications of our study can be expressed through three major findings i.e.: i) conventional treatment system seems to be effective in reducing the sars-cov-2 genes, ii) uasb system enhances the decay of genetic loading, and iii) on this first-time comparison of peg method and filtration method, peg method has shown superior performance over filtration method in terms of sars-cov-2 rna sensitivity and inhibition removal. the authors declare no 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faecal samples prolonged presence of sars-cov-2 viral rna in faecal samples time course quantitative detection of sars-cov-2 in parisian wastewaters correlates with covid-19 confirmed cases evaluation of lockdown impact on sars-cov-2 dynamics through viral genome quantification in paris wastewaters wastewater-based epidemiology for early detection of viral outbreaks community sewage sensors for monitoring public health molecular and serological investigation of 2019-ncov infected patients: implication of multiple shedding routes. emerging microbes & infections viral load dynamics and disease severity in patients infected with sars-cov-2 in zhejiang province acknowledgement: key: cord-345347-wrgg8met authors: campling, paul; joris, ingeborg; calliera, maura; capri, ettore; marchis, alexandru; kuczyńska, anna; vereijken, tom; majewska, zuzanna; belmans, els; borremans, lieve; dupon, elien; pauwelyn, ellen; mellander, per-erik; fennell, christopher; fenton, owen; burgess, edward; puscas, alexandra; gil, elena isla; de alda, miren lopez; tudel, gemma francès; andersen, erling; højber, anker lajer; nowakowska, marzena; suciu, nicoleta title: a multi-actor, participatory approach to identify policy and technical barriers to better farming practices that protect our drinking water sources date: 2020-10-17 journal: sci total environ doi: 10.1016/j.scitotenv.2020.142971 sha: doc_id: 345347 cord_uid: wrgg8met despite an improvement of water quality across europe there are many pollution hotspots for both nitrates and ppps, mainly due to agricultural activities. the bmps and mms to reduce pollution from agriculture are well known, and there are policy instruments in place to ensure drinking water standards, but the current approach has not been efficient enough. within the h2020 water protect project the premise was that there is a need for a multi-actor, participatory approach to tackle the issue from a new angle, and to assess why the uptake of known bmps and mms was not better among farmers. seven “action labs” were selected that represent major physical, socio-economical, cultural and farming settings across europe. a methodology of multi-actor engagement was chosen but with different approaches due to the local context. initially the level of farmers' awareness about water quality issues was matched to the observed uptake rates of bmps and mms. in a second survey barriers hindering the uptake of measures were identified. the first survey revealed a low general awareness on the potential pollution to drinking water sources. despite this, between 24% to 88% of the surveyed farmers per action lab were already voluntarily adopting one quarter of the selected bmps and mms. the second survey demonstrated the need to address organisational, legislative, sociological and technical barriers. the lack of coordination between different institutional bodies promoting measures and the financial incentives needed to invest and operate these often-costly measures need to be considered. the multi-actor, participatory approach with its improved awareness and collaboration made it possible to identify the crucial factors for improvement to build a social acceptance among all actors and communicate the issues and solutions from the start. high-quality, safe, and sufficient drinking water is essential for life: we use it for drinking, food preparation and cleaning. however, more than half of the river and lake water bodies in europe are reported to be in less than good ecological status. the main environmental pressures are point (38%) and diffuse source pollution (18%) and about 25% of groundwater across europe is in poor chemical status (eea,2018) . the wider research community recognises that management of water in a sustainable way "is the key for the future of food and agriculture" (oecd, 2020a) . the 2030 agenda for sustainable development acknowledges the importance of water quality and includes a specific water quality objective in sustainable development goal (sdgs, 2020) . farming accounts for between 30% and 60% of local water used across europe and contributes to water pollution sourced from nutrient, pesticide and other pollutant discharges (e.g. tractor oils) (oecd, 2020b) . through pollution from nitrates and plant protection and policy-makers in designing cost-effective measures for addressing water pollution in agriculture (mateo-sagasta, j., et. al., 2017) . water quality in surface and ground waters has generally improved across europe thanks to the adherence to waste water treatment standards for point emissions and the uptake of bmps and mms by the farming sector for diffuse emissions. however, there are still a number of pollution hotspots across europe for both nitrates and ppps, largely due to agricultural activities. the bmps and the mms to reduce pollution from nitrates and ppps are well known, there are also policy instruments in place to ensure that drinking water standards are met, but drinking water companies are still being required to invest and operate drinking water treatment facilities to deliver drinking water that meet the required standardsso in essence the current approach is not working and more should be done to reduce costly end of pipe drinking water treatment solutions. therefore, the h2020 water protect project started with the premise that a different multi-actor, participatory approach was needed to tackle the issue from a new angle and to get to the bottom of why farmers are not sufficiently taking up known bmps and mms to protect drinking water sources. we selected seven action labs across europe that represent some of the major differences in physical, socio-economical, cultural and farming systems across europe. best management practices (bmps) and mitigation measures (mms) are key elements to limit or prevent water and environmental pollution from agricultural activities. the analysis of their efficacy has thus raised several scientific projects and multiple exchanges between regulatory authorities. a number of initiatives have been undertaken across member states to stimulate their uptake (topps http://www.topps-life.org, magpie https://www.setac.org/magpie, compass https://balticcompass.org/). this has resulted in the genesis of a wide variety of approaches, implemented at national levels such as good agricultural practices or legislative measures. the increased uptake of measures to reduce nitrogen pollution from agriculture and improvements in urban waste water treatment have led to a steady reduction in average nitrogen concentrations in rivers from 2.7 to 2.1 mg no3/l (1992 to 2012) and average concentrations in groundwater are well below the groundwater quality standard of 50 mg no3/l (european commission, quality standard (eqs). the reduction of the pollution of drinking water sources by ppps and fertilisers used by the agricultural sector remains the biggest challenge. despite the increased integration of policies to deliver clean and safe drinking water over the last 30 years there is clearly a need to increase the engagement between interdependent actors and stakeholders (european environment agency, 2012) . efficiency and innovation do not seem to be the only parameters that can solve the challenge of sustainable and low-impact agriculture, which instead requires a much more complex analysis with an integrated approach. an integrated approach involves an understanding of technological problems, social behaviour of rural communities, economic constraints, the legal and institutional framework and contextual agricultural practices (chartzoulakiset and bertaki, 2015) . belmans (2018) suggests that a move towards a more "horizontal" and "participatory" water governance between the various actors and stakeholders would be more productive: water companies, farmers, nature conservation ngos, plant protection product producers, fertilizer producers, food and retail businesses, consumer organisations, environment agencies and ministries. there are other approaches, such as stewardship programmes, financed by food and drink companies to protect the quality of local water supplies (newborne and dalton, 2019) . in a similar vein certification schemes such as the european water stewardship (ews) certification scheme (https://ews.info/) have the same goal to organize companies to improve the environmental footprint of their value chain and protect water resources (jones et. al., 2014) . in this framework, the h2020 funded project waterprotect was established with the aims to: (1) analyse whether the solutions offered by the existing governance systems can adequately cover the impact by the agriculture; (2) demonstrate how selected mitigation measures have an impact on improving water quality; and (3) contribute to the effective uptake and realisation of best management practices to deliver good water quality. a pan-european, multi-actor approach was adapted in the context of seven rural or mixed rural/urban action labs (also known as living labs) to determine barriers and factors that hinder the uptake of bmps and mms to protect drinking water sources from nitrates and ppps and that have an impact on farmers' decision making and strategies. the hypothesis is that water and agriculture policy reforms to support farmers and policy makers in their decision-making requires an in-depth understanding of the local context and of the policy-related driving factors that impact on water quality. on the basis of this understanding, recommendations were provided to improve awareness, collaboration and in some case the uptake of bmps j o u r n a l p r e -p r o o f journal pre-proof and mms in the action labs. the seven action labs are located in six different environmental zones (wur, 2011) which cover 75% of the area relevant for agriculture ( figure 1 , table 1 ). the main farming systems in the eu are considered: mixed farming (two action labs), field crops (three action labs), and permanent crops (two action labs). among the seven action labs, there are three rural land uses (romania, ireland, denmark) and one mixed urban and rural land uses (belgium) with small water supplies. larger action labs, including two mixed urban and rural land uses (italy, spain) and one rural land use (poland), are delivering drinking water to hundreds of thousands of inhabitants. in five of the action labs the focus is on groundwater that is used either in public supply (denmark), or both public and private supply (ireland) or used locally from private wells as drinking water or for agricultural use ( spain, italy, romania). in the action labs, the water quality of water resources is under pressure from manuring and agro-chemicals, but different action labs chose specific targeted pollutants: four action labs focussed mainly on ppps (belgium, italy, ireland, spain), whereas three worked mainly on nitrates (denmark, poland, romania). sustainable agriculture is the result of complex "systemic interactions" between different actors involved in various ways, such as researchers, farmers, entrepreneurs, regional and national organizations, etc. indeed, a complex socio-ecological issue such as water quality related to agriculture cannot be solved by just one actor but rather from a multi-actor approach perspective (belmans, 2018). all of them have different forms of knowledge (practical, scientific, policy based, etc.) and there is the need to create conditions for interaction between them and combine their knowledge, perspectives, resources, and experiences, to identify and discuss solutions and new ideas. therefore, all the actors identified in the seven action labs that were considered to have an influence on or to be influenced by the environment and the farming systems, were invited to engage in the study development and activities. since it is recognised that at the context level there is not a "one fits all approach", in each action lab the stakeholder involvement was conceptualised as an "active engagement" that followed a stepwise approach. the approach included both j o u r n a l p r e -p r o o f water quality analysis (e.g. participatory monitoring) and stakeholders' analysis, with different levels of participation based on actors' roles that ranged from specific consultations to active involvement in the project (e.g. hosting demonstrations, facilitating meetings, field visits etc…). based on the initial knowledge status of each action lab, the level of collaboration and the specific local objectives, the approach led to a range of different strategies throughout the overall process. a detailed description of each strategy adopted is provided by calliera et al. (2020, submitted to this vsi) . in summary, the strategies included: (i) face-to-face meetings (such as seminars, workshops, community events, or site tours), an exchange/informing qualitative "dialogue-based method" that allows greater spontaneity and interaction between the researchers and participants; (ii) surveys, exchange questionnairebased quantitative tools, where stakeholders are requested to individually answer questions by choosing from a limited number of provided answers; (iii) participatory monitoring, the engagement of farmers, farmers associations and farmer's consultant organisation in the design and the setup of water monitoring for the catchment; (iv) participatory training approach and demonstration farm, exchange/informing activities able to identify and bridge "the gap between what is and what should be in terms of incumbents' knowledge, skills, attitudes, and behaviour for a particular situation at one point in time" (farm path project, 2014) . the collation of information underpinning the multi-actor engagements allows us to summarise the level of stakeholder awareness at the beginning of the project in each action lab, list the stakeholders involved and define the strategies for engagement (table 2 ). to better define the context of the study, it was necessary to carry out an analysis of the water and agriculture related policies, so as to identify the policy-related driving factors that impact on water quality in the action labs. the analysis considers the critical success factors that enhance the effective integration of environmental water concerns into agricultural practices, including the contribution of agricultural and environmental policies and regulatory frameworks. agriculture and water management go hand in hand, and within the eu policies related to these two sectors there are many opportunities for synergies and reinforcements (european commission, 2017) . however, j o u r n a l p r e -p r o o f the eu water and agriculture policies also have individual objectives and different implementation mechanisms, which creates differences in the depth and coherence of their coordination. the first element worth noting is that the common agricultural policy (cap) for the period 2013-2020 is a fully integrated policy, meaning that standards are set at eu level with member states having little room for flexibility in the implementation, except for the rural development pillar measures. consequently, the eu legal framework is built on directly applicable regulations, so there is no requirement for transpositions. on the other hand, environmental policy, including water policy, has been founded completely on the subsidiarity principle. this means that major policy goals are agreed at the eu level, while member states are given the powers to implement and enforce by transposing the directives into national legislation. the main environmental policy instruments related to water that are to be considered here are: directive (wfd) and sets groundwater quality standards, introducing measures to prevent or limit inputs of pollutants into groundwater (european parliament and council, 2006) ; and, for eu agriculture policies, the cross-compliance requirements (set of minimum agricultural production standards) and the measures included in the rural development plans are those that define the framework for the farmers, in order to benefit from eu subsidies. being part of cross-compliance, directive 128/2009 for the sustainable use of pesticides (sud) (european parliament and council, 2009 ) is an important instrument to help achieve good water status, although broader in scope, it includes relevant measures aimed at protecting the water resources by restricting the use in certain areas and by implementing buffer zones and other measures to reduce run-off and leaching. also included in cross-compliance is the nitrates directive (council of the european union, 1991) that aims at the reduction of pollution from agricultural nitrogen. several other eu policies have a rather indirect impact on water and will not be considered in this analysis. for example, the recent eu circular economy package includes provisions like the rules for water reuse or the new rules on fertilisers that open the door to a different approach in water and nutrient management. another piece of legislation that can play a role in water management and agriculture is the habitats directive. the policy analysis focuses on two fundamental questions: 1. what are the interactions between the various policies as well as the coherence, exchange of information and coordination at the implementation level? 2. how are the guidelines, requirements and rules in various policy instruments translated at farmer level in the action labs? the choice of methodology was to structure the evaluation around the main stages of the policy cycle. the policy cycle-based assessment has at the centre the policy instruments, hence facilitating the formulation of specific policy suggestions and recommendations ( figure 2 ). the evaluation of the water and agriculture policies coherence, coordination and interaction has included an extensive literature review on existing relevant reports and policy documents produced at eu level and/or commissioned by eu institutions. to answer the first fundamental question the analysis has established a framework for all potential and possible interactions within the intervention logic for water and agriculture policies of the eu. the realities of implementation in the seven action labs areas were judged against this framework (see results 3.1.). for the second fundamental question, the analysis has included a structured questionnaire collecting expert opinions from the action labs (see results 3.2). the seven action labs (case studies) cover different climatic conditions, different types of farming systems, different legal frameworks, larger and smaller water collection areas. each action lab was chosen, based on the local specificities and pressures on water resources, to focus on nitrates and/or ppps (table 1) . hence, each action lab gave a different weight on what is considered relevant in the policy framework, based on the pollutant (s) of concern. the action lab leaders were asked to evaluate the policy implementation realities in their study area using the following criteria:  effectiveness of the exchange of information and interaction;  coherence of the requirements, rules and guidelines (as perceived by the farmer);  relevance of the implementation mechanism in relation to the objectives; and,  added value of coordination and synergies between policy areas. due to non-availability of information or data on the efficiency and effectiveness of individual policy instruments in the action labs the assessment was based on expert opinions on the integration of water and agriculture policies using a structured set of 10 key questions (s1). the first step in the analysis of the uptake of bmps and mms to prevent the pollution of drinking water sources from agriculture was to match the wealth of information from previous european projects that assess mitigation measures with the local knowledge of the farming systems and the focus issues in the seven action labs. the three projects consulted were topps, magpie and compass: the bmps selected were chosen on the basis of protecting drinking water sources from nitrates and/or plant protection products. while some technical measures provide solutions for a wide range of pollution problems, such as grass buffer zones or constructed wetlands, others are more problem specific, such as phytase supplementation or drift reducing nozzles. non-technical measures focus on changes in behaviour rather than the use of technology or techniques, such as only spraying when weather and field conditions allow safe ppps use. other bmps require new or improved technologies or infrastructure, such as the management of polluted water derived from cleaning of sprayers. many of these measures are well known across europe but are not all fully implemented. in addition, these measures may simply not be appropriate for a given farming system, due to the physical characteristics of the area and / or the prevailing socioeconomics of the farming sector in an action lab. therefore, the action lab leaders did a first assessment of the relevance of selected bmps in the action labs, including a discussion with stakeholders in the field (farmers, farm advisors, government and non-government officials). this resulted in an extension of the basket of bmp measures from 56 to 77 (s2). these are grouped into seven categories of bmps (table 3) reflecting the pollutant focusnitrates and / or ppps and whether the measures are related to soil management, farm operations, or animal husbandry. one category of measures focuses on practices in animal husbandry and manure management (n1manure) and contains farm practices such as e.g. reducing the dietary nitrogen and phosphorus intake or adopting phase feeding of livestock. also, in this category are management practices on the field such as incorporating manure immediately after application on cultivated land. another category of bmps & mms focusing on nitrate is related to soil management plant production practices (n2soil). included here are e.g. making a nutrient balance on farm and/or field level, using treated urea or liming. a specific subgroup of soil management practices is related to mitigating runoff and is equally relevant for nitrates and ppps (n&ppp). this category contains runoff control measures such as grass buffer zones, crop rotation to preserve organic matter or establishing retention structures. a small category of measures is related to control of diffuse losses specifically for ppps (ppp1soil): permanent grassing in the interrow and weeding the row, considering alternative systems for pest control. for ppps, three more categories are delineated focusing on point source prevention (ppp2point, e.g. use a safe filling and cleaning place for the spraying equipment), on spray drift mitigation (ppp3drift, e.g. use drift reducing nozzles) and general precautionary measures (ppp4general, e.g. ensure adequate training for sprayer operator). in each of the action labs a questionnaire was developed to take to the farmers. the objective of the survey was to gather information regarding the uptake of bmps and mms within the action labs (table 4 ), and to assess the willingness of farmers to implement additional, innovative measures, depending on costs and benefits. each action lab selected a number of bmps and mms from the basket of measures based on the relevance for the area (targeted type of pollutant, well established and novel approaches, critical pollutant routes in the area). this resulted in 7 different questionnaires that started from the same objective but contained different lists of bmps and mms. the coverage of the survey in the different action labs varies but is considered good: for bollaertbeek the 49 farmers represent 44% of the farmland and 30% of all farmers, with a relatively higher proportion (56%) of farmers that spray themselves compared to farmers using a contract sprayer. in wexford, 44% of the farmers responded to the survey. in val tidone the survey was conducted in two stages with 175 farmers (38%) taking part in the general survey including bmps on point pollution (4 bmps) and 50 farmers (11%) in the second survey including bmps on diffuse pollution (14 bmps). in gowienica 60% of the farmers took part in the survey covering 93% of the farmland. in mara river 29% of the farmers j o u r n a l p r e -p r o o f responded representing 6.2% of the catchment. in lower llobregat river the survey was taken by 24 farmers that are members of a plant protection association (receiving training and advice) and by 5 farmers that are not. non-professional farmers could not be reached but the overall response rate was 12%. in vester hjerk 7 out of 8 farmers in the capture area were reached (representing 90% of farmland in the capture area) and some additional farmers in the supply zone. the majority of the action labs also included obligatory bmps and mms in the questionnaire (between 10% of the list in gowienica up to 56% in lower llobregat) while two action labs only focused on the uptake of voluntary measures (val tidone, vester hjerk) ( table 4 ). obligatory bmps and mms are either mandatory by national law (evaluated in each action lab separately) or, in the case of bollaertbeek, mandatory for certification to be allowed to sell the crop (vegetables) on the market. voluntary measures are not mandatory by law and can in some cases be eligible for funding from rural development funds (e.g. as erosion-control or biodiversity promoting measures). follow up work was carried out after the questionnaire surveys, in line with the multi-actor engagement techniques (described in section 2.2), with the specific objective to establish the barriers to the uptake of bmps and mms, so as to understand what motivates farmers to adopt voluntary measures and what holds them back. an iterative process was adopted by the action lab leaders (table 1) from which a check list of possible barriers was establishedthis was used as a template to interview the farmers again to understand the underlying barriers that influence decision making. the checklist of barriers was further organised into the following categories: organizational, legislative, sociological, political and technical. the basket of collaborative tools and results were further used to reflect on how the policy instruments could be better used to improve awareness, collaboration and in some cases the uptake of bmps and mms in the action labs in the future. the intervention logic describes the way various elements of a policy aim at influencing the target groups towards achieving common objectives. the eu policies are developed in an intervention logic that seeks to combine various policy instruments and secure synergies to achieve a multiplier effect on the ground. journal pre-proof however, the reality is much more complex in the action labs where various specific conditions, administrative organisation or local culture and ways of working, can facilitate or hinder such policy interactions. this enabled us to develop an evaluation framework that maps out the potential interactions that exist between policy implementation instruments (figure 3 ), leading to an assessment of what the intensity and effectiveness of policies are in each action lab. the general assessment is that the rural development plans do make use of the information collected in the implementation of the water related policy instruments. in general, this is done at a higher integration level and contextualising the information into the specific objectives of rural development. the type of data used is not homogenous in the eu, some countries make use of general statistical data, some explore the monitoring data in detail while others integrate such data with specific assessments and evaluations done by recognized national or local organisations. when it comes to evaluating the coherence between rural development and rbmps, again, the level of integration varies between countries. however, in general, the two programming instruments seem to be generally correlated. national action plans adopted, as required by the sustainable use of pesticides directive 2009/128/ec (european parliament and council, 2009) , include quantitative objectives, targets, measurements and timetables to reduce the risks and impacts of pesticide use. water resources and recommendations are made j o u r n a l p r e -p r o o f for taking appropriate risk mitigation measures on the territory to avoid pesticides contamination of water resources. farmers receive information on the standards to be followed through many channels, mainly from the farmer associations and farmer advisory centres. they issue guidelines and management practices to make requirements clear and feasible in practice, which is not always possible since the legislation is not always coherent in definitions and concepts. through the expert analysis we can conclude that there is a certain level of complexity for the implementation of the eu legislation at national level, which is often influenced by the political context, administrative or organisational specificities, history or culture of participatory policy making and public consultation. provisions and national level requirements on water protection are considered to be generally coherent and no contradictions between objectives or measures for their implementation were identified by experts. however, the complexity of the implementation arrangements translates into a difficult communication on the objectives and the related means or measures in place for their achievement. the bmps which are currently implemented and those that were deemed to be implementable mostly are small and simple measures that do not require big investments or big adaptations in the farming system and/or offer clear benefits to farmers; examples of these are keeping soil cover in autumn and winter (high uptake in wexford, bollaertbeek, gowienica and mara river) or not spraying non-target areas (high uptake in val tidone, gowienica, wexford (mandatory) and bollaertbeek). increase in productivity is a strong incentive for farmers to implement bmps (e.g. crop rotation to preserve soil organic matter) while environmental aspects such as need for minimization of the risk of drift of ppps or nutrient losses to the environment are poorly recognized by farmers in some cases, depending on the awareness of the water quality issues. knowledge on and perception of effectiveness and usefulness of different bmps varies between countries. for example, results of the survey in wexford suggest poor performance of constructed wetlands and therefore low potential for implementation of this measure. in contrast to that, in vester hjerk landscape level bmps such as constructed wetlands, set aside and afforestation seem to have a relatively high potential. larger and more expensive measures are more difficult to implement; nonetheless measures perceived as being immediately beneficial for farmers (i.e. giving long term financial benefits) have relatively high potential for implementation. for example, the use of gps technology in farming shows high potential for implementation in wexford, gowienica and vester hjerk. other measures recognized as effective but not giving direct benefits to farmers, e.g. anti-hail nets are not considered interesting or applicable, mainly due to the excessive costs. for these measures, financial incentives would be necessary to increase their implementation. implementation of measures that require land area, such as for example vegetated buffer strips at the edge of a field or within a field, are not welcomed by farmers due to loss of land for agricultural production. however, farmers in gowienica indicated that they would be in favor of them if given land tax exemptions for these areas and/or state/commune support in preventing weed infestations. in some cases (vester hjerk, bollaertbeek, gowienica) there is a positive approach to collaborative solutions, where more farmers and stakeholders are involved. for example, farmers indicated they would welcome a solution where a common, public cleaning place for cleaning sprayers was provided. organising these solutions needs facilitation of dedicated institutions and/or a leader with good communication skills, j o u r n a l p r e -p r o o f as making a consensus among farmers themselves to work together has also been identified as a potential barrier. some cases (val tidone, bollaertbeek) highlighted that farmers showed to be open for cooperation and expressed their interest in obtaining more information about specific bmps or how to mitigate defined problems. in another action lab (gowienica) farmers admitted to participating in many trainings related to bmps, however these were "too theoretical" and hence were not effective since they did not sufficiently contribute to understanding the problem. the follow up survey after the formal questionnaire to determine the rate of uptake of and potential interest in voluntary bmps and mms revealed that there are a wide range of barriers that can be categorised under: organisational, legislative, sociological, political and technical (table 5 ), which are fully described in s3 based on accompanying field notes. the barriers that occur in three or more of the action labs provide guidance in terms of commonality and provide policy makers the required focus on the issues that are troubling farmers. the barrier that was most commonly pointed out (by 6 out of 7 participating action labs) was too complex organizational set up of institutions responsible for implementation and execution of water management policies. this was highlighted by poland, italy, spain, romania, ireland and belgium. the general conclusion is that there are too many institutions involved in water management at national and regional/local levels, which causes roles and responsibilities to be unclear and sometimes overlapping. many countries noted a definite dispersion of competences and a large variability in the stakeholders' perception of the water governance structure and the stakeholders' roles. this confuses farmers and discourages them to contact specific authorities and inhibits uptake of measures. little cooperation between stakeholders at local level was pointed out by 5 of out 7 action labs (poland, italy, spain, belgium and romania) as another important factor hindering the effectiveness of measures. by lack of cooperation it is understood that there is not only little integrated effort in defining and implementing measures (which relates to point 2), but also a lack of communication and exchange of information. this further implies that the voices of some stakeholders are not heard by others and that actions taken by the government officials favour specific groups of stakeholders. this was highlighted by farmers during multiple workshop meetings in poland, belgium, italy, romania and spain. regulations from different policy areas, such as groundwater, surface water, drinking water, agriculture and nature conservation are poorly coordinated. this was indicated by 4 action labs: poland, italy, belgium and denmark. regulations developed by different governmental departments are only focused on their own interests. this creates situations where finding practical solutions at a local level is very difficult, as requirements of one regulation often contradict requirements of the other. on the other hand, the implementation of one measure can often fulfill requirements of more than one regulation and this could significantly boost their effectiveness, reduce costs and allow for more measures to be introduced. this requires good coordination and an integrated water management at local levels. in addition, low awareness of farmers regarding impacts they may cause on the environment has also been identified as an important barrier, noted by 4 out of 7 action labs (poland, italy, romania, belgium). the field assessments revealed that farmers in general still have a problem with linking how their everyday activities may affect the environment. it has been noted that the economic sustainability of the activity prevails over environmental sustainability. the family economy and personal goals influence the transition to sustainable agriculture. nonetheless, this links closely to the problem of little transparency of environmental monitoring programmes which do not inform farmers about their findings. farmers are not aware about water quality results from national/regional water monitoring campaigns in their areas and as such are not aware of impacts they make. another common barrier highlighted by 3 out of 7 action labs (poland, italy and belgium) was the multiplicity of regulations, which often are unclear. farmers need to be aware of multiple regulations regarding nitrates, ammonia, ppp, erosion control, etc. some of which are very long and complex. this causes regulations to be difficult to apply and to control in practice not only by farmers, but also by civil servants. three out of seven action labs (poland, romania and belgium) indicated inefficient control mechanisms to be factors inhibiting implementation of measures. there are two aspects in here to be considered. first of all, lack of actions taken towards those that do not fulfill legal requirements makes farmers to feel above the law and do not motivate them to take actions. another aspect that has been highlighted by farmers themselves is that the lack of control and actions towards those who break the law discourages farmers that take actions and do things according to legal protocols. an additional problem highlighted by farmers in poland is that the level of environmental fines is too low for large scale farmers to respect. farmers often j o u r n a l p r e -p r o o f journal pre-proof admitted themselves that breaking laws and paying fines was more worthwhile to their business than taking up mitigation measures required by law. farmers in poland, spain and belgium pointed out that the lack of long-term vision for environmental protection with respect to water and agriculture is an important problem. this relates to frequent changes in regulations and lack of continuity in approaches taken. the environment needs time to respond to changes that have been introduced. belgium highlighted that regulations change too often and become stricter and stricter every few years. farmers, who already implement measures and try to do their best are often 'penalised' when stricter rules are imposed. as a result, farmers lose their faith in legislations; they become suspicious and refuse to implement measures on a voluntary basis. in the water protect workshops, farmers asked for a clear and long-term vision from the government. the typical 4-years duration of governments does not allow to advance in questions that require more time for its implementation. in italy, spain and ireland farmers noted that time is needed for stakeholders to adapt to changes. this regards not only logistical issues such as time needed for utilization of older products that have been made prohibited but may still be stored by farmers, but also mental ability of people to adapt to changes such as the implementation of new measures. in poland, spain and ireland farmers think that standards and recommendations from applicable law and action programs are not fully adapted to climate changes (e.g. mild winters and earlier start of the growing season, and periods of allowed fertilization). farmers in poland, romania and belgium advocated that systems of support incentives for best practices in relation to water management as well as for agro-ecological approaches are too little. in poland, there are premises that cultivation on a particular land is more beneficial than applying new voluntary bmps and receiving subsides for that action. this is especially visible in areas with rich soils that can be cultivated intensively with profitable results. as a result, little interest is given for new more environmentally friendly initiatives on a voluntary basis. in italy, spain and ireland farmers highlighted that there is too little financial support for implementation of more advanced measures that are expensive. these measures can be attractive to implement but their cost and complexity can hinder straightforward implementation. too much bureaucracy is a common complaint expressed by the farmers. filling of paperwork required from farmers causes additional costs and confusion (poland, italy and spain). three countries, namely, italy, poland and ireland noted the lack of knowledge transfer from science to policy. policy and science are not commonly integrated causing knowledge gaps where decisions are made. important research findings are not efficiently disseminated to the right stakeholders or are not acknowledged enough in order to support decisions on the right measure, in the right places and at the right time. for example, the action lab studied in poland has a very long-lasting history of research, yet their findings have not led to changes in local policies and regulations. lack of interest in participation in the process of law creation. polish, spanish and romanian partners informed that consultation (in general, and specifically with respect to water management) is still a process that needs to be learnt and few people are interested to participate in the consultation, mainly specialized ngo's or directly interested stakeholders. farmers have little confidence that their opinions will be incorporated, so they have little motivation to participate. as a team we set out a methodology of multi-actor engagement that started at the same point but needed to be adapted to the local context, meaning that the execution of the approach was different. the strength of this method meant that the individual teams in the action labs could ensure that farmers and other actors were properly engaged in a meaningful and relevant way, with a consistent policy and field assessment framework. the weakness was that standard statistical comparisons concerning the uptake of bmps and mms to protect drinking water sources from nitrates and ppps cannot be inferred. we therefore discuss our results in a qualitative manner to guide our recommendations and conclusions. we look to match the level of awareness that farmers expressed about water quality issues at the start of the process (table 2 ) to the uptake rates of bmps and mms observed at the action lab level (figure 4 ). this is further discussed in light of the barriers to taking up measures identified during the follow-up surveys (table 5 ), accounting at the same time for the policy evaluation framework that identifies potential interactions between policy instruments ( figure 3 ). a herbicide) is a potential problem for drinking water supplies further down the catchment, although there was inadequate knowledge about the pollutant transfer pathways. at the lower llobregat (spain) basically all stakeholders, including farmers and citizens, were aware of the general bad quality of the water, but due to the complexity of the area it is difficult to know which activities are the most polluting. on the whole farmers believe that agriculture is not the main source of pollution. in val tidone (italy) there was also very little awareness from the farmers that ppps might have a deleterious effect on the local groundwater. participatory monitoring in all action labs was therefore essential to show farmers and other stakeholders mms in all action labs were complaints about the complexity of the legislation and follow-up, including the inherent bureaucracy involved. in addition, farmers in bollaertbeek also found that some of the mitigation measures, such as buffer zones, were technically confusing and difficult to implement, whereas on the other hand they are looking for measures that could reduce spray drift better. it was felt that there were also not enough control mechanisms to deal with non-compliant farmers, which was a complaint. in addition, farmers in these action labs indicated that there was insufficient financial support now to encourage them to step into the voluntary measures requiring major investments. the farmers in val tidone also found that some of the measures being promoted were not even suitable for their particular landscape and setting. action labs that focussed mainly on nitrates (gowienica -poland, mara -romania and vester at gowienica (poland), even though the environmental agency has been operating a nitrate vulnerable zone for more than 12 years, the farmers in the area had very little awareness that nitrates are polluting the surface and ground waters. in mara (romania) this lack of awareness was also apparent. in vester hjerk being implemented by 64% of the farmers surveyed, but almost 90% of the farmers were considering implementing additional selected measures in the future. in addition to low awareness the other typical barriers to the uptake of bmps and mms in all action labs were the complex and poorly coordinated legislation and actions from the different government agencies, the lack of specialised personnel to provide professional guidance on measures, and the perception that there were insufficient control mechanisms for compliance. in gowienica and maraformerly eastern bloc countriesthe farmers found the approach of authorities too centralised with a lack of information. in vester hjerk the hydrogeology is very complicated so that it was questionable whether there is a direct link between surface measures carried out by farmers and the impact on groundwater water quality. in terms of using the policy evaluation framework that identifies interactions between policy instruments it is clear that policy instruments have to begin to address the organisational, legislative, sociological and technical barriers to the uptake of bmps and mms. at the farmer level the most important barrier after low awareness is that the process for them to take up bmps and mms is too complex and uncoordinated. this calls for legislation and regulations from both the ministries (or departments) of agriculture and environment to be simplified and integrated. clear and unambiguous messages on production standards and requirements is needed. the measures should also be selected in an open and constructive dialogue, which j o u r n a l p r e -p r o o f journal pre-proof take into account aspirations but also limitations and difficulties of the different actors. furthermore, the measures should be feasible in practice and if the measure involves extra costs without any return on investment for the farmer, it is clear that improved financial incentives need to be provided. with limited public finances it is therefore necessary that cooperation and synergies between the various institutional actors funding measures to be improved. while the purpose and technical aspects are usually quite clear and straight forward, the desired transition towards a 'new normal', including standardization and education of best management practices is almost never completed towards satisfying and long-lasting levels. matters of organizational, financial or cultural origins, which are inevitable occurrences of life seem to keep us away from what is sensible to do. the long value chains that we have built for our food production dilute both the impact and responsibility which the involved people experience. there is however, a huge common success factor: bottom up societal support. this creates peer pressure to continue performing, when times are getting tough. sometimes, extreme events like water quality issues, drought, heavy rain, covid-19, trigger the justification of rapid implementation of bmps, and addressing the barriers for uptake is an important outcome of waterprotect. this can go very fast, whereas the usual uptake is often a long and difficult process. a conclusion is that the building of societal acceptance, the communication of issues and solutions before the start, are the crucial success factors for a multi-actor, participatory approach to improve farm management practices and protect our drinking water sources. the eu policy architecture that governs the water and agriculture areas is complex, partially due to the historical evolution of the two eu policy areas, but also partially due to the complexity of the challenges these need to address. coherence of water and agriculture policies at eu level is recognized as an area where improvement is needed. several actions have been taken at political and technical level, but there are also further opportunities for improvement. we have first taken the step to assess the situation by embarking on a multi-actor engagement strategy in the seven action labs. from this assessment we can conclude that the general awareness of farmers about the potential pollution problems caused to drinking water sources by the applications of nitrates and ppps is low. despite this low awareness between 24% to 88% of the surveyed farmers per action lab were already voluntarily adopting one quarter of the selected bmps and mms.information about the potential uptake of voluntary measures in the action lab ranges j o u r n a l p r e -p r o o f journal pre-proof from 13% to 90% of the farmers being willing to adopt additional selected measures. the follow up surveys provided us a better understanding of what is preventing farmers from taking the step to incorporate voluntary bmps and mms in their farm management. therefore, we can conclude that the next steps are to address the complexity of the process (administrative and technical), the lack of coordination between the different institutional bodies promoting measures, and the financial incentives needed to invest and operate these often-costly measures will increase the likelihood of more farmers taking up bmps and mms. with these points in mind and using the analysis on the coherence of water and agricultural policies and cross-referencing those with the implementation realities, we can make the following policy recommendations: 1. the eu should exploit the cycles of policy revisions to better integrate objectives and create mechanisms and structures of coordination. needs to be fully exploited to ensure coherence of objectives for water management and agriculture at national level, given that the new policy implementation arrangements give more flexibility to eu member states in deciding agricultural policy priorities, and to allocate much needed resources for farmers to make a positive contribution to sustainable water management. 3. member states should strive to streamline the implementation structures and procedures based on sound governance concepts that ensure the involvement of all concerned stakeholders in sustainable management of water resources & agriculture. 4. future policy implementation approaches should state the need for further exchange of information and data between the various programmatic and enforcement instruments and structures. results of controls over agricultural activities will have to influence priorities in water management and, equally, information on water quality and quantity issues, should be better transferred to the farmers. promoting multi-actor, participatory water governance models are recommended due to their capacity to: easily transfer information on the water management challenges, collaborative development of solutions, capacity to address local specificities and limitations and can create synergies with other action areas. j o u r n a l p r e -p r o o f 6. proactive provision of information on the challenges in water quality and their potential cause are essential to ensure awareness at farm level and understanding of the positive contribution farmers can make. currently, information is often unclear, scattered or not easily accessible. in many cases farmers rely on informal channels (farmer associations, media, extension consultants, etc) to obtain such information. 7. the positive contribution to sustainable water management of agriculture, including through implementing bmps and mms should be evaluated, recognized and communicated. a set of indicators that highlight the contribution agriculture has into water management (able to capture positive and/or negative trends) will help with farmers' involvement of and will stimulate ownership of the process. impact on the willingness of farmers to implement them. hence, direct information, know-how and as well as support for actual investments needed for implementation of will play a key role in the future uptake of such measures by farmers. finally, on the basis of the approach to improve awareness, collaboration and in some cases the uptake of bmps and mms in the action labs the crucial success factors to achieve this are to build social acceptance among all actors and to communicate the issues and potential solutions right from the start. directive 2009/128/ec of the european parliament and of the council of 21 october 2009 establishing a framework for community action to achieve the sustainable use of pesticides directive 2013/39/eu of the european parliament and of the council of 12 august 2013 amending directives 2000/60/ec and 2008/105/ec as regards priority substances in the field of water policy transition pathways towards sustainability in agriculture: case studies from water stewardship and corporate sustainability: a case study of reputation management in the food and drinks industry water pollution from agriculture: a global review executive summary agriculture and the environment: better policies to improve the environmental performance of the agriculture sector water and agriculture: managing water sustainably is key to the future of food and agriculture corporate water management and stewardship: signs of evolution towards sustainability. london, overseas development institute this research is part of the waterprotect project and has received funding from the european union's key: cord-266052-rcuzi70u authors: liu, lilong; hu, junyi; hou, yaxin; tao, zhen; chen, zhaohui; chen, ke title: pit latrines may be a potential risk in rural china and low-income countries when dealing with covid-19 date: 2020-10-29 journal: sci total environ doi: 10.1016/j.scitotenv.2020.143283 sha: doc_id: 266052 cord_uid: rcuzi70u according to the latest reports, severe acute respiratory syndrome coronavirus 2 (sars-cov-2), which caused coronavirus disease 2019 (covid-19), was successfully isolated from the excreta (stool and urine) of covid-19 patients, suggesting sars-cov-2 could be transmitted through excreta contaminated water. as pit latrines and the use of untreated excreta as fertilizer were common in rural china, we surveyed 27 villages of jiangxi and hubei provinces and found that pit latrines could be a potential source of sars-cov-2 water pollution. recently, bats have been widely recognized as the source of sars-cov-2. there were many possible intermediate hosts of sars-cov-2, including pangolin, snake, bird and fish, but which one was still not clear exactly. here, we proposed a hypothesis to illustrate the mechanism that sars-cov-2 might spread from the excreta of infected humans in pit latrines to potential animal hosts, thus becoming a sustainable source of infection in rural china. therefore, we believe that abolishing pit latrines and banning the use of untreated excreta as fertilizer can improve the local living environment and effectively prevent covid-19 and other potential waterborne diseases that could emanate from the excreta of infected persons. although this study focused on rural areas in china, the results could also be applied to low-income countries, especially in africa. the ongoing pandemic of coronavirus disease 2019 is an emerging respiratory infectious disease caused by the severe acute respiratory syndrome coronavirus 2 (sars-cov-2), which was named 2019-ncov previously , posing an unprecedented challenge to global public health. the most common symptoms of covid-19 patients include fever (80%-99%, 90% on average ), cough (59%-82%, 69% on average), fatigue (70%), sore throat (5%-40%, 21% on average), shortness of breath (31%-55%,39% on average), rhinorrhea (4%-20%, 12% on average) and muscle ache (11%-35%, 23% on average) (cai et al., 2020; chen et al., 2020a; huang et al., 2020; wang et al., 2020a) , while diarrhea (2%-10%, 5% on average), nausea (10%), vomiting (4%) and abdominal pain (2%) were also reported (huang et al., 2020 , chen et al.,2020a . significantly, sars-cov-2 ribonucleic acid (rna) was detected in the stool of 53%-83% (64% on average) covid-19 patients (including patients with severe symptoms, asymptomatic status, and treated patients with no further sign of the symptoms), and the duration of positive stool ranged from one day to more than a month (cai et al., 2020; chen et al., 2020b; holshue et al., 2020; lescure et al., 2020; pan et al., 2020; tang et al., 2020; wang et al., 2020b; wu et al., 2020c; xiao et al., 2020a; xu et al., 2020; zheng et al., 2020) . among all patients, 23%-43% (33% on average) of all age groups and 80% of children were still positive in stool even after the respiratory tract samples infections (leung et al., 2003; zhou et al., 2017) , zhou et al. (2020a) isolated sars-cov-2 from differentiated bat small intestinal organoids and human intestinal organoids, an in vitro model of the human intestinal epithelium. they found that both bat and human intestinal organoids developed progressive cytopathic changes after sars-cov-2 inoculation and accompanied by a substantially increased viral load in the culture media (zhou et al., 2020a) , suggesting that active replication of sars-cov-2 in human intestinal organoids. notably, infectious sars-cov-2 was successfully isolated from the stool specimen of a patient with diarrheal covid-19 (zhou et al., 2020a) and 2 patients without diarrhea (wang et al., 2020d) . another study showed that infectious sars-cov-2 virus were successfully isolated from 2 of 3 patients with viral rna-positive, indicating that infectious virus in feces was a common manifestation of covid-19 and confirmed the potential of fecal-oral or fecal-respiratory transmission (xiao et al., 2020b) . in addition, recent studies showed that human angiotensin-converting enzyme ii (ace2), which had been proved to be a cell receptor for sarscov-2 (lu et al., 2020; zhou et al., 2020b) , was highly expressed in glandular cells of human gastric, duodenal, and rectal epithelia, supporting the entry of sars-cov-2 into host cells (xiao et al., 2020a) . moreover, viral nucleocapsid protein (np)-positive cells were not only observed in the cytoplasm of gastric, duodenal, and rectum glandular epithelial cells from the biopsy specimens of covid-19 patients (xiao et al., 2020a) , but also in human intestinal organoids (zhou et al., 2020a) . collectively, the available evidence demonstrated that the occurrence of sars-cov-2 infection in human intestinal organoids might recapitulate enteric infection of covid-19 patients, and the human intestinal tract might represent an additional route of sars-cov-2 transmission (zhou et al., 2020a) . in the meantime, sars-cov-2 rna was also detected in the urine sample (sun et al., 2020) , sink, and toilet (ong et al., 2020) of covid-19 patients, and the positive urine duration j o u r n a l p r e -p r o o f journal pre-proof was more than one month (sun et al., 2020) . notably, sun et al. (2020) successfully isolated infectious sars-cov-2 from the urine of a covid-19 patient, suggesting that sars-cov-2 might be secreted through the human urinary system. considering that infectious sars-cov-2 virus was found in urine and stool samples from covid-19 patients on days 11-15 of the clinical process (jeong et al., 2020) , and the duration of sars-cov-2 rna positive in stool and urine would last more than one month (cai et al., 2020; chen et al., 2020b; holshue et al., 2020; lescure et al., 2020; pan et al., 2020; tang et al., 2020; wang et al., 2020b; wu et al., 2020c; xiao et al., 2020a; xu et al., 2020; zheng et al., 2020; sun et al., 2020) , we believed that sars-cov-2 might exist in the stool and urine of patients with covid-19 for a long time. according to the available literature, sars-cov-2 rna was detected in wastewater samples from the netherlands (lodder and de roda husman, 2020) , australia (ahmed et al., 2020), france (wurtzer et al., 2020) , usa (wu et al., 2020a) , italy (la rosa et al., 2020b), and spain (randazzo et al., 2020) , we inferred that sars-cov-2 contaminated water might be a potential sustainable source of infection, thus threatening the local individuals' health. previous studies have shown that water contaminated by bacteria, viruses, and chemicals was closely related to the use of pit latrines and septic tanks (gerba, 1999; graham and polizzotto, 2013; hammoud et al., 2018; ngasala et al., 2019) . herein, this study aims to comprehensively evaluate the potential risks of covid-19 in rural china through the investigation of rural geographical environment, the use of pit latrines, and the villagers' daily life, then try to find out the solutions. although this study focused on rural areas in china, the results could also be applied to other low-income countries, especially in africa. in order to prevent the spread of covid-19, several versions of the prevention guidelines were issued in china, suggesting that people with a history of living or traveling in epidemic areas should carry out self-health monitoring twice a day for 14 days from the time of leaving the epidemic area, and try to live alone or in a single room with good ventilation to minimize close contact with their families (national health commission of the people's republic of china, 2020). zhang et al. (2020a) proposed a home confinement guideline for rural areas, emphasizing that people from the epidemic areas of covid-19 should use tableware and sanitary items alone to avoid or control the suspicious transmission of sars-cov-2. however, the living conditions of some rural residents were difficult to meet the criteria for home confinement during the outbreak response. for example, some villagers who did not have flush toilets at home must leave their rooms and use the nearby shared pit latrines for defecation, which might increase the close contact between people and also increase the transmission of sars-cov-2. in addition, sars-cov-2 could be transmitted through the human excreta as mentioned above. a field investigation was carried out in 3 villages of jiangxi province, china, which contained returnees from wuhan. the survey included the sources of domestic water, the structure, distribution and use of pit latrines among villages, and the excreta management pattern in rural china, to find out whether there was a systematic disinfection process and analyze the possibility of fecal contamination of drinking water. in addition, we also conducted a detailed survey on the distribution of family houses and daily life routes of villagers with a history of being in epidemic areas in wuhan and other cities of hubei province to identify the impact of pit latrines on the risks of covid-19 j o u r n a l p r e -p r o o f journal pre-proof transmission. village committees are grass-roots mass organizations of self-governance elected by villagers of the administrative village under the jurisdiction of a township in mainland china, a village committee shall be composed of 3-7 members, including the chairman, vice-chairmen and members (chinese government, 2010 ). their functions mainly include self-management, self-education, self-service by villagers, and carry out democratic elections, democratic decision-making, democratic management and democratic supervision. the village committees handle the village's public affairs and public welfare undertakings, mediate civil disputes, assist in maintaining public order, and report to the people's government the opinions, requirements and suggestions of the villagers (chinese government, 2010) . thus, the village committees know the basic situation of the village very well. to understand the prevalence of pit latrines in rural china, we contacted to the village committees from 27 villages in jiangxi and hubei provinces by phone, email and wechat to survey the number of households, the total population, the average household size, whether there are flush toilets at family, whether villagers use pit latrines, and whether villagers use untreated excreta as fertilizer among the rural households. here, we define flush toilets as flushing human excreta (urine and feces) chinese villages have long been known for their small bridges and flowing water, which means that chinese villages are usually built near streams, where great rivers originated. during the field investigation of 3 villages in jiangxi province, china, we found that they all located upstream of the river, and many pit latrines are scattered around the rural houses throughout the villages. as shown in figure 1 , a typical pit latrine in rural china consists of 3 main parts: a shelter for creating a private space, a slab or floor with a small hole for villagers to defecate, and a cesspool for storing feces and urine. besides, there was usually a small window on the wall of cesspool for farmers to take the excreta as a natural fertilizer. to make it easier for farmers to get the excreta, some cesspools were built on the open next to the shelter. as described in available researches (heinonen-tanski and van wijk-sijbesma, 2005; lam et al., 2020a; mamera et al., 2020) , human urine and feces as fertilizer could meet the needs of plants for potassium and phosphorus, and improve soil structure, and using human excreta as fertilizer is free, which leads to the villagers like to use excreta as fertilizer. through surveying 27 villages in jiangxi and hubei provinces by contacting the village committees through phone, email and wechat, it was found that about 0%-60% (31% on average) of rural households used the excreta directly from the pit latrines as crop fertilizer in recent 3 years. in addition, according to the villagers, we learned that the excreta in the open cesspools may be washed to everywhere by rainwater, or be carried to everywhere by animal like dogs, cats, or field mouse, eventually polluting the local water. fortunately, the villagers' domestic water is all diverted from the mountain stream by water pipes rather than groundwater. although the water from mountain stream j o u r n a l p r e -p r o o f journal pre-proof was not treated before using, it was not polluted by excreta as the source of water was far away from the pit latrines. it was well documented that the bacteria, viruses, and chemicals within drinking water sources or agricultural soil posed a great threat to human health (gerba, 1999; gerba and bitton, 1984; graham and polizzotto, 2013; hammoud et al., 2018; jamieson et al., 2002; leung et al., 2020; mamera and van tol, 2018; mamera et al., 2020; nganje et al., 2020; tallon et al., 2005) . for example, wells in nearby septic tanks and pit latrines were found to be significantly contaminated in dar es salaam, tanzania, leading to more than 80% of wells contained with escherichia coli and 58% of wells with nitrate levels higher than who guidelines (ngasala et al., 2019) . it has been recognized that the consequent movement of pathogens along with subsurface drainage systems to surface water systems was the main route of pathogen transport (jamieson et al., 2002; prüss-ustün et al., 2019) , and it was possible that slimy bacteria form a thin coat over the pipelines to aid in the spread of sars-cov-2 (naddeo and liu, 2020). thus, sars-cov-2, as a virus, may also be transmitted through water. a study from australia (ahmed et al., 2020) showed that the number of infected individuals in the catchment areas could be reasonably estimated by detecting the copy numbers of sars-cov-2 rna in the wastewater, which verified that early detection of coronavirus in wastewater might be a viable surveillance strategy for covid-19 infections (daughton, 2020; orive et al., 2020; wu et al., 2020b) as previously demonstrated for hepatitis a virus, norovirus (hellmér et al., 2014) and poliovirus (asghar et al., 2014; lodder et al., 2012) . although there was no sufficient evidence that fecal-oral transmission of covid-19 was viable, while there was evidence showed that sars-cov-2 could be easily and sustainably transmitted in the community in shenzhen, china, because the proportion of covid-19 patients without definite exposure from january 25 through february 5 (11%) was much j o u r n a l p r e -p r o o f journal pre-proof higher than that before january 24 (6%) . this suggests that there may be other potential routes of transmission, such as exposure to sars-cov-2 that survive in community environment. given that the infectious sars-cov-2 was found to be secreted through the human urinary system (sun et al., 2020) and intestinal tract (wang et al., 2020d; xiao et al., 2020b; zhou et al., 2020a) , and sars-cov-2 rna was detected in wastewater worldwide (randazzo et al., 2020), many studies have suggested the possibility of wastewater transmission of covid-19 disease (adelodun et al., 2020; arslan et al., 2020; foladori et al., 2020) . however, the direct use of untreated excreta as a fertilizer and the flushing of excreta from open cesspools into the waters on rainy days might lead to serious water pollution, including the sars-cov-2 within human excreta. thus, the possibility of sars-cov-2 transmission through water contaminated with human excreta cannot be ignored. coronaviruses are present in a variety of animals and can cause respiratory, enteric, hepatic, and nervous system diseases of varying severity (lau et al., 2005) . the members of the coronavirus family, sars-cov (drosten et al., 2003) , mers-cov (chan et al., 2015) and the current sars-cov-2 (zhu et al., 2020) have caused severe respiratory illness and high mortality to humans since 2002. studies have shown that both sars-cov and mers-cov were likely originated from bats and then crossed species barriers to infect humans through an amplification mammalian host, the paguma larvata for sars-cov and the camelus dromedarius for mers-cov (chan et al., 2015; cheng et al., 2007; lau et al., 2005) . similarly, recent studies have shown that sars-cov-2 might originated from bats with the genome of sars-cov-2 has 88%-96% (91% on average) nucleotide j o u r n a l p r e -p r o o f journal pre-proof identity with several bat coronaviruses and 79%-82% (80% on average) with human sars-cov, but might with more proximal origins from a potential intermediate animal host ji et al., 2020; lu et al., 2020; zhou et al., 2020b) . it has been reported that pangolins (lam et al., 2020b; lopes et al., 2020; wahba et al., 2020; xiao et al., 2020c; zhang et al., 2020b) and snakes (ji et al., 2020 ) might be the intermediate hosts of sars-cov-2. however, the possibility of snakes as intermediate hosts of sars-cov-2 was questioned by the scientific community , and the existing evidence was not sufficient to either confirm or rule out the role of pangolins as an intermediate host (tiwari et al., 2020; wahba et al., 2020) . in other words, it is still not clear which animal is the intermediate hosts that brings sars-cov-2 to human hosts. (chan et al., 2013) . as described in the latest review (tiwari et al., 2020) , many coronaviruses have bats, birds, or pigs as the primary host, in addition to infecting animals such as civets, pangolins, and camels, coronaviruses also could be harbored by a range of animal species, such as fish, snake, cattle, horse, dog, cat, rabbit, rodent, ferret, minks, frog, marmot, and hedgehog. moreover, damas et al. (2020) had greatly expanded the potential number of intermediate hosts that might be infected by sars-cov-2 through ace2 receptors by protein structural analysis, which means that plenty of wild animals might be novel sars-cov-2 hosts. the results highlight the importance of wildlife and biosecurity in farms and wet markets, which may serve as the potential source and amplification centers for emerging infections (cheng et al., 2007; tiwari et al., 2020) . previous studies have elucidated that sars-cov could survive for 4 days in diarrheal stool samples with an alkaline ph (lai et al., 2005) , 14 days in sewage at 4 degrees celsius and 2 days at j o u r n a l p r e -p r o o f journal pre-proof 20 degrees celsius (wang et al., 2005) , and retained its viability for over 5 days at temperatures of 22°c -25°c and relative humidity of 40%-50% (chan et al., 2011) . kampf et al. (2020) analyzed 22 studies and found that human coronaviruses such as sars-cov, mers-cov or endemic human coronaviruses could persist on inanimate surfaces like metal, glass or plastic for up to 9 days. another study (casanova et al., 2009) found that two surrogate coronaviruses, transmissible gastroenteritis (tgev) and mouse hepatitis (mhv) remained infectious in water and sewage for days to weeks at 25 degrees celsius, the time for 99% reduction was 9 days for tgev and 7 days for mhv even in the pasteurized settled sewage, suggesting that contaminated water might a potential vehicle for human exposure if aerosol was generated. notably, recent studies demonstrated that sars-cov-2 was highly stable at 4°c with only around a 0.7 log-unit reduction of infectious titre on day 14, but was sensitive to heat as the time for virus inactivation was reduced to 5 minutes (chin et al., 2020) . besides, no infectious virus was detected from treated smooth surfaces on day 4 (glass and banknote) or day 7 (stainless steel and plastic), but a detectable level of infectious virus could still be present on the outer layer of a surgical mask on day 7 (chin et al., 2020) . sars-cov-2 could be highly stable in a favorable environment (van doremalen et al., 2020) , for example, sars-cov-2 is extremely stable in a wide range of ph values at room temperature (ph 3-10) (chin et al., 2020) . infectious sars-cov-2 has been found in human excreta samples of covid-19 patient in many previous studies (sun et al., 2020; wang et al., 2020d; xiao et al., 2020b; zhou et al., 2020a) , and the sars-cov-2 embedded in stool particles in septic tanks could escape from disinfection and slowly release into aqueous phase, behaving as a secondary source of sars-cov-2 and potentially contributing to its spread through drainage pipelines . former study has found that particles (kaolin clay, humic acid powder, and activated sludge) ＜2μm in diameter were large j o u r n a l p r e -p r o o f journal pre-proof enough to protect viruses from 254-nm ultraviolet (uv) light (templeton et al., 2005) , suggesting that the protection of faecal particles might make the survival of sars-cov-2 more easier. the sars-cov-2 within the excreta of covid-19 patients can be released into the water (natural environment) when farmers use untreated excreta as fertilizer in agricultural fields, and the excreta been washed into water by rainwater or be carried to water by animal. then the sars-cov-2 survived in the natural environment would be available absorbed by wild animals (such as bats, birds, fishes, and snakes) by drinking or contacting contaminated water, and become a secondary source of human sars-cov-2 infection. this hypothesis was consistent with another study that sars-cov-2 spilled into novel wild hosts in north america, as demonstrated by franklin and bevins (2020) through a conceptual model for the perpetuation of the pathogen. owing to the typically high mutation rates of rna viruses, coronaviruses (including sars-cov-2) can rapidly increase their virulence and adapt to new hosts (duffy, 2018; elena and sanjuán, 2005) . besides, the potential aquatic animals that may be infected with sars-cov-2 in the river may reach cities downstream of the river, then may be caught and eaten by city dwellers, further expanding the range of transmission. as excreta was directly used as fertilizer, fruits and vegetables grown in rural areas might be contaminated by sars-cov-2 and then eaten by wild animals, or purchased and eaten by rural and urban residents through wet markets. long-term exposure to contaminated environmental sources, such as the air pollutants, extended exposure to aerosols produced by contaminated water, and the inadequate cleaning processes of food and the surfaces of some materials, may resulted in an increased risk of sars-cov-2 transmission (adelodun et al., 2020; carraturo et al., 2020) . thus, it was seemly reasonable that the sars-cov-2 survives in nature could be a potential sustainable source of infection (figure 2) , particularly for those people in rural areas who relied on untreated j o u r n a l p r e -p r o o f journal pre-proof drinking groundwater sources (hammoud et al., 2018; mamera and van tol, 2018; rosa and clasen, 2010) and who practiced open defecation (adzawla et al., 2020), the increased sars-cov-2 load in the natural environment might increase the possibility of human infection. through contacting the village committees by phone, email and wechat, a total of 9606 households were investigated in 27 villages of jiangxi and hubei provinces, china, involving 34,101 persons with an average household size of 3.6 persons (1-12 persons per household) and an average number of 355.8 ± 126.4 households per village. the average proportion of households using pit latrines was 40% (0%-75%) (figure 3, table 1 ). existing reports indicated that pit latrines were one of the most common human excreta disposal systems in low-income countries (heinonen-tanski and van wijk-sijbesma, 2005; mamera and van tol, 2018; mamera et al., 2020) with approximately 1.77 billion of the world's population (graham and polizzotto, 2013) . according to a recent survey (mutyambizi et al., 2020) , pit latrines was the most common toilet facilities in informal settlements in south africa (53%), followed by flush toilets (24%), with approximately 6% reported not having access to any toilet facilities. similarly, the most common type of toilet facilities was shared pit latrine with a slab (67%) with no hand-washing facilities in kampala, uganda (ssemugabo et al., 2020) . in ghana, 40% of commonly used toilet facilities were dry toilets (pit latrines), and between 2 and 21 households, or 4 and 84 people shared one facility, (antwi-agyei et al., 2020) , and more than 25% of households engaged in open defecation (adzawla et al., 2020) . in short, toilet facilities in low-income countries are critical and need to be improved. in contrast to pit latrines, flush toilets have septic tanks that collect excreta through water-closed drainpipes, allowing for microbial degradation and disinfectant treatment of excreta when necessary (for example: to kill potential sars-cov-2). as generally considered that coronaviruses were very sensitive to oxidants, such as chlorine, ozonation, and uv irradiation (la rosa et al., 2020a; quevedo et al., 2020; wang et al., 2020c; zhang et al., 2020c) , the sars-cov-2 released from human excreta during flush toilets-drainpipes-septic tanks could be inactivated by conventional disinfection. however, pit latrines with an open cesspool are not easy to be disinfected, because the excreta may be washed to everywhere by rainwater or be carried to everywhere by dogs or field mouse. coupled with the fact that villagers usually use untreated excreta as agricultural fertilizer, we believe that the use of pit latrines in rural china and other low-income countries increases the possibility of sars-cov-2 contaminating the surrounding natural environment and ultimately harms human health. human to human contact is the most important factor to increase the transmission rate of covid-19. according to recent reports, the transmission routes of sars-cov-2 mainly include the respiratory tract by droplets or respiratory secretions, and contact with infected persons or contaminated surface and these measures were effective and have been confirmed by multiple reports (mwalili et al., 2020; ngonghala et al., 2020; teslya et al., 2020; tian et al., 2020) . during the field investigation of 3 villages in jiangxi province, china, we found that it was common for villagers to live with scattered houses and share pit latrines, with 1 to 5 households (an average of 2.2) sharing one pit latrines. as shown in figure 4 , of the 8 households in a-h, only household a included a member with a history of being in epidemic areas (wuhan), family members of both c and h households all defecated in pit latrines, other households' members defecated in flush toilets at their home and occasionally used the pit latrines. the houses of a, b, and c households were scattered, naturally, the daily life routes of family members were significantly larger than those of other families. notably, the use of pit latrines expanded the daily life routes of c and h households' members and increased the possibility of close contact and exposure to sars-cov-2 between individuals. ultimately, it might increase the risk of covid-19 transmission. given that plentiful households shared toilet facilities (most of them were pit latrines) with poor ancillary facilities (such as hand-washing facilities) were common in low-income countries (antwi-agyei et al., 2020; ssemugabo et al., 2020) , we believed that the use of pit latrines in rural china and low-income countries would increase the contact between human, thus increasing the risk of covid-19 transmission to a certain extent. we proposed this hypothesis to illustrate the mechanism that sars-cov-2 might spread from the excreta of infected humans in pit latrines to potential animal hosts and then become a sustainable source of infection in rural china and other low-income countries. the widely use of pit latrines and j o u r n a l p r e -p r o o f journal pre-proof open cesspools coupled with agricultural fields application of untreated excreta could act as a potential route for the spread of covid-19 disease and other possible waterborne diseases that could emanate from the excreta of infected persons. we suggest for further implementation of the toilets revolution in rural china and also low-income countries in the world, completely replace pit latrines by flush toilets. next, according to the division of the residential area, using drainage systems to collect human excreta centrally and then used as agricultural fertilizer after unified disinfection treatment. through these preventive measures, the local living environment will be 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novel coronavirus from patients with pneumonia in china conceptualization, data curation, formal analysis, investigation, methodology, roles/writingoriginal draft. junyi hu: data curation, formal analysis, investigation, methodology, roles/writing -original draft. yaxin hou: investigation, methodology. zhen tao: conceptualization, investigation, methodology, writing -review & editing. zhaohui chen: conceptualization, formal analysis, methodology, writing -review & editing. ke chen: conceptualization, formal analysis, investigation, methodology key: cord-263550-wjdmzmdg authors: bashir, muhammad farhan; ma, benjiang; bilal; komal, bushra; bashir, muhammad adnan; tan, duojiao; bashir, madiha title: correlation between climate indicators and covid-19 pandemic in new york, usa date: 2020-08-01 journal: sci total environ doi: 10.1016/j.scitotenv.2020.138835 sha: doc_id: 263550 cord_uid: wjdmzmdg this study analyzed the association between covid-19 and climate indicators in new york city, usa. we used secondary published data from new york city health services and national weather service, usa. the climate indicators included in the study are average temperature, minimum temperature, maximum temperature, rainfall, average humidity, wind speed, and air quality. kendall and spearman rank correlation tests were chosen for data analysis. we find that average temperature, minimum temperature, and air quality were significantly associated with the covid-19 pandemic. the findings of this study will help world health organization and health regulators such as center for disease control (cdc) to combat covid-19 in new york and the rest of the world. • the study examines the impact of climate indicators on covid-19 epidemic in new york city. • average temperature, minimum temperature and air quality have significant correlation with covid-19 epidemic. • currently there is no scientific evidence that warm weather would suppress covid-19 epidemic. a b s t r a c t a r t i c l e i n f o on december 31, 2019, the world health organization (who) reportedly received information about an epidemic with unidentified etiology (deepak et al., 2020) from wuhan, hubei, china (zhu et al., 2020) . on february 11, 2020, this epidemic was officially named as covid-19 and was acknowledged as an infectious disease resulting in public health emergency, as it quickly spread within china and to further 24 countries is situated geographically between 42.937084°n and − 75.6107°e (anderson et al., 2020) . clinical studies relating to covid-19 reported that most patients suffer from difficulty in breathing and pneumonia (holshue et al., 2020; perlman, 2020) . symptoms reported in clinical treatments were similar to other coronavirus illnesses such as mers and sars e.g. cough, fever, and difficulty in breathing due to respiratory disorder, and in worst-case scenario covid-19 causes kidney failure, pneumonia, and even death . in the usa, the first covid-19 patient was reported in the washington state on january 15, 2020, and coronavirus quickly spread throughout the country as the usa became the epicenter with most deaths and the most number of patients or cases which are seen on map in fig. 1 . and after wisconsin reported its first death on april 13, 2020, all 50 states had at least one casualty from covid-19 in the usa. as of april 13, 2020 new york (195,749) , florida (123,019) and new jersey (64,584) are worst-hit states in america. new york state quickly became epicenter within the usa with the majority of cases and deaths reported in new york city, which reported its first case on march 1, 2020, and after initial days saw a rapid rise in the number of patients and deaths from march 12, 2020, onwards. similar quick spread of covid-19 in italy, france, and south korea, led to who declaring it as a pandemic (cucinotta and vanelli, 2020) . current studies have shown that the transmission route of covid-19 is bat-human, with intermediate host yet to be identified; it was transmitted mainly by respiratory droplets, as well as human-human transmission (ge et al., 2013; huang et al., 2020) . climate conditions are classified as top predictors of coronavirus illnesses (dalziel et al., 2018) as wind speed, humidity, temperature and wind speed are critical in the transmission of infectious diseases (yuan et al., 2006) . bull (1980) reported that pneumonia's mortality rate is highly correlated with weather changes. new york city is the capital of new york state and is described as media, cultural and financial hub of the world. new york is one of the densely populated cities in the usa with 8.54 million people residing within 302.6 squares miles and is situated geographically between 42.937084°n and − 75.6107°e. dataset for covid-19 is taken from march 1, 2020 -april 12, 2020, from covid-19 data archive from the new york city health department. and data for climate indicators was taken from national weather service, usa. dataset for the climate indicators includes temperature, humidity, wind speed, air quality, and rainfall. as the data was not normally distributed therefore kendall and spearman rank correlation tests were utilized to examine the correlation between variables. fig. 2 observes a sharp increase, both in daily new cases and total confirmed cases for new york city from march 12, 2020, onwards. the first week beginning from march 1, 2020 to march 7, 2020, confirmed cases are 12, which rose to 185 until the second week on march 14, 2020, 8,115 until the end of third week, 30,765 until the fourth week, 60,850 until the fifth week on april 4, 2020 and 104,410 until april 12, 2020. fig. 3 shows the maximum, minimum, and average temperature. lowest maximum temperature of 44°f (highest maximum 77°f), lowest average temperature was 35.2°f (maximum average 59.3°f) and the minimum lowest temperature was 26°f (highest lowest 56°f), average lowest wind speed 6.1 mph (maximum average 21.6 mph), average lowest humidity 25.8% (highest average humidity 91.8%) and average lowest rainfall 0 mm (average highest rain fall is 1.44 mm) are the statistical indicators of new york city. table 1 indicates empirical estimations of seven weather indicators. for kendal correlation test minimum temperature and average air quality are significant for new cases, and average temperature, minimum temperature, and average air quality are significant for total cases and average temperature and air quality are significant for mortality among new york citizens. for the spearman test, average temperature and average air quality are significant for new cases and average temperature and average air quality are significant for the total number of cases, also average temperature and air quality are significant for mortality. for the current research project, the occurrence of covid-19 in new york city is analyzed by climate change patterns. our findings estimate that minimum temperature and average temperature are correlated with the spread of covid-19 in new york city. previous studies of tan et al. (2005) and vandini et al. (2013) support our findings. shi et al. (2020) also researched climate indicators and stated that temperature serves as a driver for the covid-19. as a cultural and financial capital of the world, new york city also oversees high mobility from local as well as constituents from other major places to seek employment and business opportunities. humidity is another contributor for the spread of covid-19 as it contributed in the rapid transmission within new york city and empirical estimations of this study will be useful in the outcome of efforts to suppress covid-19. according to official census data, new york city is resident to 8.54 million people with population increasing at 4.6% per year and 26,403 residents living per square mile. the reason for such a dense population is the average life expectancy of new york residents, which is 80.9 years, this is 2.2 years longer than the national average of life expectancy in america. such statistics make new york an ideal epicenter for the spread of infectious diseases (zu et al., 2020) . humidity and temperature also play significant role in the seasonal spread of coronaviruses (sajadi et al., 2020) . wang et al. (2020) also reported similar findings for the case of china. covid-19 outbreak from wuhan showed a strong association between disease spread and weather conditions, with predictions that warm weather will play an important role in suppressing the virus. other meteorological indicators such as wind speed, air quality, and humidity also affect the spread of infectious diseases. furthermore, air temperature also contributes towards the transmission of the virus . ma et al. (2020) suggested that humidity and temperature will play an important role in mortality rate from covid-19 as climate indicators and temperature correlate with the spread of covid-19 (poole, 2020) . this study, despite strong evidence of climate indicators' association with covid-19, provides the following limitations. first, more variables are needed to conduct a comprehensive study as covid-19 is an infectious disease and it is affected by many variables such as social distancing, people's endurance and availability of health facilities. second, data about personal hygiene indicators such as hand wash needs to be explored in further studies. climate indicators are integral in the fight against covid-19 in new york. this study finds that average temperature, minimum temperature, and air quality are significant correlated with covid-19 pandemic and will be useful in suppressing covid-19. also, significance of air quality implies that green environment policies should be promoted as it would reduce the spread of infectious diseases such as covid-19. current study is of exploratory nature and in order to conduct a comprehensive investigation, future research direction should examine daily carbon emission data as current lockdown measures have greatly reduced carbon emissions. another research direction is to include regional and cross-country investigations for most affected countries to provide better insight for the fight against covid-19. we acknowledge the financial support by the ministry of education-china mobile joint laboratory grant number: 2020mhl02005. authors would also like to acknowledge the editors and two anonymous reviewers, who contributed immensely in improving the quality of this publication. how will country-based mitigation measures influence the course of the covid-19 epidemic? the weather and deaths from pneumonia roles of meteorological conditions in covid-19 transmission on a worldwide scale who declares covid-19 a pandemic urbanization and 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temperature and its variation respiratory syncytial virus infection in infants and correlation with meteorological factors and air pollutants unique epidemiological and clinical features of the emerging 2019 novel coronavirus pneumonia (covid-19) implicate special control measures a climatologic investigation of the sars-cov outbreak in beijing a novel coronavirus from patients with pneumonia in china coronavirus disease 2019 (covid-19): a perspective from china. radiology key: cord-290458-5fwbh9t9 authors: lal, preet; kumar, amit; kumar, shubham; kumari, sheetal; saikia, purabi; dayanandan, arun; adhikari, dibyendu; khan, m. l. title: the dark cloud with a silver lining: assessing the impact of the sars covid-19 pandemic on the global environment date: 2020-05-08 journal: sci total environ doi: 10.1016/j.scitotenv.2020.139297 sha: doc_id: 290458 cord_uid: 5fwbh9t9 abstract the severe acute respiratory syndrome-coronavirus disease 2019 (covid-19) pandemic caused by a novel coronavirus known as sars-cov-2 has caused tremendous suffering and huge economic losses. we hypothesized that extreme measures of partial-to-total shutdown might have influenced the quality of the global environment because of decreased emissions of atmospheric pollutants. we tested this hypothesis using satellite imagery, climatic datasets (temperature, and absolute humidity), and covid-19 cases available in the public domain. while the majority of the cases were recorded from western countries, where mortality rates were strongly positively correlated with age, the number of cases in tropical regions was relatively lower than european and north american regions, possibly attributed to faster human-to-human transmission. there was a substantial reduction in the level of nitrogen dioxide (no2: 0.00002 mol m−2), a low reduction in co (<0.03 mol m−2), and a low-to-moderate reduction in aerosol optical depth (aod: ~0.1–0.2) in the major hotspots of covid-19 outbreak during february–march 2020, which may be attributed to the mass lockdowns. our study projects an increasing coverage of high covid-19 hazard at absolute humidity levels ranging from 4 to 9 g m−3 across a large part of the globe during april–july 2020 due to a high prospective meteorological suitability for covid-19 spread. our findings suggest that there is ample scope for restoring the global environment from the ill-effects of anthropogenic activities through temporary shutdown measures. j o u r n a l p r e -p r o o f in 2020 a novel coronavirus known as sars-cov-2 struck the world through widespread human transmission (bukhari and jameel, 2020), creating fears of a new plague similar to the spanish flu in 1918 , mexican smallpox in 1967 , aids in the early 1980s, sars in 2002 /03, bird flu in 2005 , swine flu in 2009 /10, and ebola in 2014 (harari et al., 2007 . first discovered by the chinese center for disease control and prevention , the first case of covid-19 was reported in the region of wuhan in the central hubei province of china on 31 st december 2019 twc india, 2020) . rising global death tolls combined with the high infectivity of the virus, mild clinical symptoms, an uncertain incubation period, lack of pre-existing human immunity, and the possibility of asymptomatic healthy carriers (bouey, 2020) led to the who declaring covid-19 a "public health emergency of international concern (pheic)" on 30 th january 2020 (world health organization, 2020a) . covid-19 is transmitted via droplets and fomites (contact with contaminated surfaces) (bouey, 2020), with children less affected than adults and the elderly. a coronavirus patient can transmit the disease to three people on average without intervention (compared with one for the common influenza, two for ebola, and 18 for measles) . symptoms of covid-19 range from mild clinical symptoms similar to the common cold or flu (guo et al., 2020; peeriet al., 2020; shi et al., 2020; wang et al., 2020) , with major symptoms appearing 2-14 days from infection and including trouble breathing, persistent pain or pressure in the chest, mental confusion or inability to arouse, and bluish lips or face (cdc, 2020) . those with persistence symptoms often require specialized respiratory management at intensive care units (chan et al., 2020; rodriguez-morales et al., j o u r n a l p r e -p r o o f to-date there is no known specific and effective pharmacological treatment for covid-19 (cortegiani et al., 2020) . despite china's preventative measures to control the spread of covid-19, several other countries are still struggling to contain the virus (dong et al., 2020) . various pandemic risk reduction measures such as social distancing, cluster lockdowns, mass quarantines, extensive travel bans, and disruptions to transportation systems have had a direct impact on local and global socio-political relations and economic growth (long and feng, 2020) . such extreme measures to control the virus have potentially resulted in decreases of aerosols and atmospheric pollutants due to the disruption of anthropogenic-based emissions (https://www.theguardian.com/world/2020/mar/20/coronavirus-the-week-the-world-shutdown). aerosols have direct and indirect contributions on climate change at regional and global scales (huang et al., 2014; menon et al., 2002; qian and giorgi, 1999) as increased levels of aerosol optical depth (aod) affects atmospheric stability and precipitation as aerosols disturb the scattering and absorption of solar radiation (jiang et al., 2016) , the hydrological cycle (prasad et al., 2004) and vegetation cover and its growth (lal et al., 2019; sarkar and kafatos, 2004) . in addition to climatic effects, aerosols increase respiratory problems in humans and decrease visibility in urban areas (prasad et al., 2005) . a study on the 2002/03 severe acute respiratory syndrome (sars) showed a positive relationship between long term exposure to air pollution (pm 10 , no 2 , co, o 3 , and so 2 ) in china and a higher risk of dying (84%) in regions of moderate and high air pollution index (cui et al., the covid-19 pandemic outbreak had brought major economic disruption in the world (khan et al., 2020; wto, 2020) , with disruptions in global supply chains, business and consumer confidence, the decline in commodity prices, international tourism and business travel, and less demand for imported goods and services (boone et al., 2020) . the long-term economic impacts include changes in health care expenditure as well as downstream impacts of covid-19 on mortality and morbidity (abiad et al., 2020) , with a rapid increase in economic anxiety in the population at-large (fetzer et al., 2020) . human coronaviruses have shown strong winter seasonality between december and april, becoming undetectable in the summer months in temperate regions of the world (gaunt et al., 2010) . average temperature (5-11°c), relative humidity (rh: 47-79%) and latitude profiles exhibited similarity in the timing of covid-19 outbreak during january 2020 in wuhan, china, and february 2020 in other affected regions (sajadi et al., 2020) . similarly, 90% of covid-19 cases have been reported in countries with a temperature range of 3° to 17°c and between an absolute humidity (ah) of 4 to 9 g m -3 (bukhari and jameel, 2020). laboratory conditions conducive to the survival of the members of the coronavirus family are low temperatures (4°c), and moderate to high rh (20-80%) (casanova et al., 2010) . however, the sars-cov-2 may survive for several days on plastics and metals at moderate temperatures (between 21-23°c) and a rh of 40% (van doremalen et al., 2020) . this suggests there may be a direct relationship between temperature, humidity, environmental pollutants, and the spread of sars-cov-2. therefore, the objectives of the present study are to (i) assess the status of covid-19 cases across the globe, (ii) study the meteorological correlates of covid-19 occurrences, and (ii) assess the impact of covid-19 pandemic on the quality of j o u r n a l p r e -p r o o f we used satellite data, covid-19 reported case data, and meteorological data (table 1) to assess the impacts of covid-19 on the global environment. the country-wise cumulative cases of covid-19 affected-population and death tolls were acquired from who (https://www.who.int) and analyzed on a weekly basis until 10 april 2020 in a gis environment. temperature and relative humidity hourly datasets of 0.25° were taken from the copernicus climate data store (cds), and european center for medium-range weather forecast (ecmwf) (https://cds.climate.copernicus.eu) used to calculate absolute humidity. data on the weekly concentration of carbon monoxide (co), no 2 , and aod for the period of 01 january to 21 april 2020 were acquired and analyzed. the same datasets were acquired for the period of 01 january to 21 april 2019 to compare the variability of said parameters. standardized anomalies (sa) of aod and near-surface air temperature (2m above the surface) for january to march was estimated using equation 1. .…. eq 1 climate data operator (cdo) tool was used to estimate standard deviations and climatological mean. projected near-surface air temperature, and relative humidity (rh) datasets acquired from cimip-5 model at rcp 8.5 scenario until november 2020 and were used to estimate the possible impacts of covid-19 on different countries under future meteorological conditions. absolute humidity was calculated using clausius clapeyron j o u r n a l p r e -p r o o f and jameel, 2020). therefore, global covid-19 hazard assessment was estimated based on ah on future projected data for the period of april to november 2020. the ah-based hazard map was classified into 4 different classes considering their possible habitat suitability viz., high hazard (ah: 4 to 9 g m -3 ), moderate hazard (ah: 2 to 4 g m -3 and 9 to 12 g m -3 ), low hazard (ah: <2 and 12 to 15 g m -3 ) and very low hazard (ah: >15 g m -3 ). the cases related to covid-19 affected population and death tolls were mapped and analysed ( figure 1 ). a total of 1240239 persons with confirmed cases and 81661 deaths occurred due to covid-19 around the world till 10 th april 2020 (world health organization, 2020b). the majority of covid-19 infected cases, as well as death, were reported in the european region (52.6% of total infected persons and 71.4% of total death tolls) followed by the region of americas (32.4% infections and 18.4% deaths), western pacific region (7.7% infections and 4.3% deaths), eastern mediterranean region (5.8% infected persons and 5.0% deaths), south-east asian region (0.9% infections and 0.6% deaths) and african region (0.6% infections and 0.4% deaths) ( figure 1 ). on the other hand, the percentage of deaths with reference to the total number of confirmed cases was highest in the european region (8.3%), followed by the eastern mediterranean region (5.2%), south-east asian region (4.4%), and african region (4.3%) with the lowest deaths as compared to confirmed cases reported from the region of americas (3.5%) and western pacific region (3.4%) ( table 2) . the global country-wise assessment indicated the majority of affected populations were from the united states of america (34.34% of the global cases), followed by spain (12.29%), italy j o u r n a l p r e -p r o o f (11.58%), germany (9.15%), france (6.88%), china (6.72%), iran (5.34%) and uk (5.25%). while covid-19 initially came to attention in the hubei province of china and subsequently spread to many other regions of the world through global travel (huang et al., 2020) due to its highly transmissible nature (bogoch et al., 2020), a consistent pattern of covid-19 cases was observed from east to west along the 30 o to 50 o n latitude including south korea, japan, iran, and northern italy. notably, covid-19 failed to significantly spread to countries immediately south of china as the number of patients and reported deaths in southeast asia was much lower compared to temperate regions (dong et al., 2020) . high temperatures (> 40°c) and extremely low temperatures (< 4°c) restrict the spread of the members of the coronavirus family (casanova et al., 2010) and is expected to diminish covid-19 considerably in affected areas above 30°n in the coming months (sajadi et al., 2020) . the continent level assessment showed that europe (799696) was severely affected, with the country of spain (152446) being the most affected country followed by italy (143626) (3512) were moderately affected, though the number of cases was increasing rapidly. a very low number of cases were reported from j o u r n a l p r e -p r o o f hands could be another reason for widespread of covid-19. however, the transportation mechanism in western countries, which enables less person to person contact due to usage of personal transport, in contrast to public transport in tropical countries, could be a major source of spread of covid-19. health organization, 2020b), and this pattern proved to be true in other heavily infected countries in europe and north america. in the united states, 80% of deaths were individuals over 65 years of age (cdc, 2020). meanwhile, italy the home to the oldest population in europe and the second-oldest population in the world, was the most prone to the virus, with 12.8% of the 70-79 age category and 20.2% of those over 80 years of age more likely to die upon infection by covid-19 (dutta, 2020; horowitz, 2020) . despite this higher death rate, individuals living in italy have a significantly longer life expectancy than those individuals living in china (godin, 2020) . this figure is difficult to determine as age-related comorbidities such as cardiovascular disease, diabetes, and hypertension have also been shown to be highly correlated with covid-19 deaths. the death of covid-19 patients j o u r n a l p r e -p r o o f without pre-existing medical conditions was very low (only 0.9%), while the likelihood of dying for patients with pre-existing medical conditions like cardiovascular disease (10.5%), diabetes (7.3%) and chronic respiratory disease (6.3%) was very high ( global temperature and absolute humidity were mapped using era-5 reanalysis data during the covid-19 outbreak period (january to march 2020) on a weekly basis to deduce spatiotemporal variations. an increase in temperature was observed in tropical regions (30°s to 30°n latitude) as compared to temperate regions due to seasonality variations (figure 3). nearly half of the world is under partial or complete lockdown due to the covid-19 outbreak, leading to the shutdown of industries and motor vehicles and an associated reduction in the concentration of atmospheric pollutants. in the present study, the direct and indirect impact of the covid-19 outbreak on environmental pollution has been studied using spatio-temporal satellite-based products related to no 2 , co, and aod. major changes were observed in south asia and south-east asian countries including major parts of indian regions like the igp, where no 2 concentration was drastically reduced during the 12 th to 16 th week as compared to previous weeks due to the shutdown of various industries and a travel ban issued on 24 th march 2020. in western africa, major changes were observed from 7 th and 8 th week and had been continuously decreasing, whereas major changes in europe were observed 12 th week onwards. besides, the variation in global no 2 concentration is influenced by global wind circulations (arya, 1999; grundstrom et al., 2015; santurtún et al., 2017) . a sharp reduction in no 2 concentration occurred across the globe, j o u r n a l p r e -p r o o f primarily in the southern hemisphere and tropical regions during january to march 2020. as compared to 2019, other highly populated regions of the world (europe, north america, and igp) had also observed low (<0.00003 mol m -2 ) to moderate (<0.00005 mol m -2 ) reductions in no 2 during 2020. these trends may be attributed to regional variations in the timing of the covid-19 outbreak, as well as the implementation of preventive measures. the incomplete burning of carbon-based fuels leads to the generation of co which is spread by wind circulation patterns throughout the lower atmosphere (novelli et al., 1998) . the weekly monitoring of global co column number density based on daily observation of showing an increase with reference to the previous weeks, which may be attributed by the coverage of desert or proximity to the sea. the standard anomaly of aod with reference to the long term monthly mean (2000) (2001) (2002) (2003) (2004) (2005) (2006) (2007) (2008) (2009) (2010) (2011) (2012) (2013) (2014) (2015) (2016) (2017) (2018) (2019) was also evaluated. the study exhibited an increase in area under negative anomaly ( the future projections of absolute humidity based on the cimip-5 model at rcp 8.5 scenario until november 2020 were used to deduce the possible contribution of meteorological conditions to covid-19 spread following january-march 2020 variations in ah and bukhari and jameel, (2020) concepts of virus transmission at the different threshold of ah. ah plays a significant role in the transmission of sarscov-2 (carleton and meng, 2020; ficetola and rubolini, 2020; luo et al., 2020; oliveiros et al., 2020) . a peak rate of spread of covid-19 in temperate regions of the northern hemisphere having a mean temperature of ~5°c, and ah of 4 to 9 g m -3 during the outbreak period was observed, while it was lower both in warmer/wetter and colder/drier regions (ficetola and rubolini, 2020). nevertheless, j o u r n a l p r e -p r o o f changes in weather alone (i.e., increases or decreases of temperature and humidity) will not necessarily lead to declines in case counts without the implementation of extensive public health interventions (luo et al., 2020) . therefore, a prospective global covid-19 hazard based on ah from april to november 2020 was mapped and analysed (figure 8). the study projected an increasing coverage of high covid-19 hazard in a large part of the globe during april to july 2020 due to high prospective meteorological suitability (ah: 4 to 9 g m -3 ). the study illustrated a severe and high probability of covid outbreak in major parts of the northern hemisphere as compared to the southern hemisphere during may-july 2020 barring primarily tropical regions. thereafter, a reduction in covid-19 hazard may be evident in the tropical and subtropical regions during august-september 2020 due to variations in regional meteorological conditions. later, in october-november 2020, covid-19 hazard will be resurgent in the tropical and subtropical regions (primarily in the northern hemisphere) and reduced in temperate and sub-temperate regions of the globe. in the asian continent, virus transmission has a low possibility except in china as the majority of countries will have moderate ah (2 to 4 g m -3 and >10 g m -3 ) until september 2020 ( figure 8 ). the study indicated severe covid-19 pandemic hazard in the coming months due to meteorological suitability apart from local transmissions. thus, there are uncertainties associated with our model predictions. hence, we advise the end users to practise caution while using the predictions. based on the above discussion, we conclude that the intensity of transmission of covid-19 is not uniform in spite of its global spread. mortality is positively correlated with age-group as well as severe pre-existing medical conditions. there has been a substantial reduction in the emission of atmospheric pollutants viz., no 2 and aod because of forced shutdowns reflecting high fossil fuel consumption based human lifestyles in the developed countries. in general, meteorological factors may not be directly related to the number of outbreaks. however, countries with temperatures between 4°c±2°c to ~19°c±2°c and ah: 4 to 9 g m -3 are at a higher risk of covid-19 outbreak despite preventive measures. therefore, in the upcoming months, i.e., may-july 2020, the northern hemisphere may be more susceptible to outbreaks compared to tropical regions. however, tropical regions may be prone to outbreaks during the onset of winter in october, and november 2020 and appropriate actions and policy interventions should be implemented at local as well as international levels to contain covid-19 outbreaks and minimize the consequent damages. international consensus is required for such extreme measures to take place and to ensure the long-term survival of table 1 : details of data used j o u r n a l p r e -p r o o f sar-optical remote sensing based forest cover and greenness estimation over india early transmission dynamics in wuhan, china, of novel coronavirus-infected pneumonia the reproductive number of covid-19 is higher compared to sars coronavirus research report on companies' survival and development strategy during a novel coronavirus epidemic climate effects 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relationship with atmospheric circulation interannual variability of vegetation over the indian subcontinent and its relation to the different meteorological parameters radiological findings from 81 patients with covid-19 pneumonia in wuhan, china: a descriptive study the novel coronavirus pneumonia emergency response epidemiology team, 2020. the epidemiological characteristics of an outbreak of 2019 novel coronavirus diseases (covid-19) in china who names new coronavirus disease as covid-19 aerosol and surface stability of sars-cov-2 as compared with sars-cov-1 tropomi on the esa sentinel-5 precursor: a gmes mission for global observations of the atmospheric composition for climate, air quality and ozone layer applications. remote sensing of environment unique epidemiological and clinical features of the emerging 2019 novel coronavirus pneumonia (covid-19) implicate special control measures aboriginal peoples and the response to the 2019-2020 bushfires report of the who-china joint mission on coronavirus disease world health organization, 2020b. coronavirus disease 2019 ( co id-19) : situation report, 81. world health organization trade set to plunge as covid-19 pandemic upends global economy a novel coronavirus from patients with pneumonia in china relative humidity 1.2676° x 2.5° monthly 2 cimip-5 (ipsl-cm5a-mr) 4who / 5 john hopkins week 15: 09 apr to 15 apr and week j o u r n a l p r e -p r o o f (platnick et al., 2014) key: cord-317355-z5tk3v3b authors: dunker, susanne; hornick, thomas; szczepankiewicz, grit; maier, melanie; bastl, maximilian; bumberger, jan; treudler, regina; liebert, uwe g.; simon, jan-christoph title: no sars-cov-2 detected in air samples (pollen and particulate matter) in leipzig during the first spread date: 2020-10-13 journal: sci total environ doi: 10.1016/j.scitotenv.2020.142881 sha: doc_id: 317355 cord_uid: z5tk3v3b the sars-cov-2 pandemic co-occurred with pollen season in europe 2020 and recent studies suggest a potential link between both. air samples collected at our measuring station in leipzig and purified pollen were analyzed for sars-cov-2 typical signals or for virus-induced cytopathic effects, to test if the virus could bind to bioaerosols and if so, whether these complexes are infectious. the results show that neither air samples nor purified pollen were infectious or could act as carrier for virus particles. the analysis of the first pandemic phase of severe acute respiratory syndrome coronavirus 2 in europe 2020 demonstrated that infections co-occurred with the pollen season (brandstetter et al., 2020) . moreover, pollen may interfere with antiviral immunity, e.g. pollen significantly diminish the epithelial response to rhinovirus infection (gilles et al., 2020) . to date it is not known, if pollen allergy has an impact on the prevalence or severity of the sars-cov-2 pandemic. in china, allergic diseases, asthma, and copd were not shown to be risk factors for sars-cov-2 infection (zhang et al., 2020) , but in this region the maximum peak was reached during winter time, outside the pollen season and patients were not interviewed for any history of pollinosis. importantly, pollen can act as a carrier for various bacteria and moulds (heydenreich et al., 2012; obersteiner et al., 2016; oteros et al., 2019) , and sars-cov-2 remained viable in aerosols for several hours (van doremalen et al., 2020) . furthermore, morawska & cao (2020) (morawska and cao, 2020) speculate that wind-induced dispersion may occur. it was speculated, if bioaerosols may serve as carriers for the virus as regions with high air pollution were more severely affected (conticini et al., 2020) and just recently it could be demonstrated that sars-cov-2 rna can be present on pm (setti et al., 2020) . we therefore aimed at investigating whether sars-cov-2 can bind to pollen or other kind of particulate matter within bioaerosols sampled at our station in leipzig and if so, whether these complexes are infectious. j o u r n a l p r e -p r o o f fresh pollen samples from betula pendula, quercus robur and ostrya carpinifolia were collected (tab. a1). inflorescences were dried in paper bags at 30 c and pollen were sieved through a 70 µm filter (celltrics, sysmex, norderstedt, germany) and stored dry upon analysis. highly purified reference material (alnus glutinosa, betula pendula and corylus avellana) were purchased from allergon ab (ängelsholm, sweden). attempts of sars-cov-2 isolation were made using natural environmental samples (described above, table 1 ). following centrifugation at 11,000 rpm (5 min/ room temperature) supernatant was removed and saved for pcr testing (cov pcr day 0). the pellet was resuspended in dmem supplemented with nystatin/ amphothericin (40 µg/ ml/ 50 µg/ ml), seeded onto vero e6 cells in a 2.5 cm 2 petri dish, incubated at 37 °c/ 5 % co 2 and observed for 5 days for the occurrence of virus-induced cytopathic effects (cpe). negative at a final concentration of 0.2 µm, and 1 µl ssiii/platinum tag. input-rna was 5 µl, and 2.6 µl of water was added to reach a final reaction volume of 20 µl. alternatively rdrp_sarsr-f2/r1 and rdrp_sarsr-p2/p1 were used for amplification and detection of the respective gene. rt was done at 55 °c for 10 min, followed by 3 min denaturation at 94 °c and 45 amplification cycles with denaturation for 15 sec at 94 °c, annealing for 30 sec at 58 °c and elongation for 30 sec at 60 °c. amplification was monitored after each elongation step at 530 nm. the pollen season in leipzig, germany started with a high number of hazel (corylus sp.) pollen at the beginning of february 2020, followed by alder (alnus sp.) one week later (fig. 1 ). nine days after the last higher alnus sp. pollen peak (94 pollen/ m³), the first covid-19 cases were documented. overall, low case numbers were registered in leipzig in contrast to other german cities, most likely related to an early lockdown (red bar in fig. 1 ). the birch (betula sp.) pollen season started during the decrease of registered covid-19 cases in april and was followed by pollen emission from oak (quercus sp.) and pine (pinus sp.). particulate matter (pm 2,5 ) concentrations were partially higher than the threshold level of 10 µg/m³ (annual mean) defined by the who (dotted grey line in fig. 1) . however, the concentrations were still lower than in regions of northern italy (bianconi et al., 2020; conticini et al., 2020) or wuhan (ma and kang, 2020) and could be an additional reason for low registered case numbers in leipzig. air samples containing bioaerosols and particulate matter were collected starting with the first wave of infections (grey bars in fig. 1 ). in none of these samples sars-cov-2 typical for a detailed analysis of a possible correlation between concentrations of the most abundant pollen, particulate matter and registered covid-19 cases, a correlation matrix was created with r (package "performanceanalytics") (fig. 2) . the number of registered cases (green box, fig. 2 ) was positively correlated with the pollen-concentration of corylus sp. and negatively correlated with the concentrations of grasses (poaceae). (table 1) . next, we wished to determine whether pollen can bind sars-cov-2 at all. to address this issue, commercially available, highly purified pollen (alnus glutinosa, betula pendula and corylus avellana) were incubated in vitro with sars-cov-2 (3x10 4 tcid 50 in 0.5 ml dmem, i.e. approx. 1x10 7 genome equivalents) for 1 hr. thereafter, pollen was washed, centrifuged as indicated in the supplement before they were screened for presence of viral rna and infectious sars-cov-2. again, no sars-cov-2 typical signal was detected by rt-pcr or cpe at any time point (table 1) . moreover, we could exclude the possibility that components of the air samples interfered with virus detection since geq of sars-cov-2 spiked to original samples were clearly detected by rt-pcr or cpe (fig. a1 , table a2 ). we are somewhat consoled by this negative finding since a positive result would have had severe implications for sars-cov-2 restrictions, as pollen can be transported over long distances (up to several 100 km) (hjelmroos, 1991) . it should be noted however, that due to a low number of registered covid-19 cases in leipzig, it may be difficult that a measurable virus load can be detected in the air due to low number of emitters, especially since infected persons also had to go into quarantine immediately. therefore, a negative result for sars-cov-2 is not surprising for this case study, but could j o u r n a l p r e -p r o o f potentially be different in cities with much higher infection rates. statistically, it is highly probable to find virus on pollen and particulate matter when the concentration of both is really high also meaning that there is a coalescence effect between droplets and pm. this probably confirms that the spread effect in leipzig was essentially due to the direct contact human-to-human and not mediated by a vehicle, while in regions with higher pm load, transmission via pm could be an additional pathway (setti et al., 2020) . we also considered technical limitations to account for our failure to detect sars-2 cov-2 signals in air samples and in purified pollen preparations. air sampling: several authors have shown, that cyclone samplers are suitable to collect virus particles in the air (d'arcy et al., 2014; kim et al., 2018; verreault et al., 2008; west and kimber, 2015) . d`arcy et al. (2014) (d'arcy et al., 2014) successfully detected airborne virus particle in hospital air with a cyclone sampler, which is in accordance with the fact that this technology was originally developed to collect biological warfare agents in the air. the height of our measurement station was chosen to guarantee a representative measurement in contrast to near-ground stations which show higher variability in pollen concentrations (rojo et al., 2019) . nevertheless, it would be interesting to analyze if sars-cov-2 signals in near-ground traps, e.g. on crowded public places can be detected. sars-cov-2 detection: nucleic acids were analyzed by rt-pcr and infectivity was tested by analysis of cpe on vero indicator cells. we could exclude that suspended air samples or purified pollen interfered with sars-cov-2 replication since sars-cov-2 spiked to the original samples was readily detected (fig. a1 , table a2 ). our in vitro incubation experiments of highly purified pollen and sars-cov-2 were performed in fluid suspension. however, the binding pattern between pollen and virus particles could be potentially different in the air, e.g. due to electrostatic effects. such effects might be of interest in future studies. in summary, this is a first study investigating the relation of pollen and sars-cov-2 pandemic. the results show that neither air samples nor purified pollen of different taxa were infectious or could act as a carrier for virus particles. this leaves open the possibility that pollen or particulate matter within bioaerosols may affect sars-cov-2 susceptibility indirectly for example by perturbing nasal or bronchial epithelial barrier function or anti-viral immunity as shown by others for rhinovirus infection (gilles et al., 2020) . the leipzig e.v. as potential conflicts of interest. note: there was no inhibition of sars-cov-2 replication. * sars-cov-2 pcr; e, rdrp and n gene, measured without prior cell cultivation, day 0 ** sars-cov-2 pcr; e, rdrp and n-gen, measured after cultivation for 8 days j o u r n a l p r e -p r o o f particulate matter pollution and the covid-19 outbreak: results from italian regions and provinces symptoms and immunoglobulin development in hospital staff exposed to a sars-cov-2 outbreak can atmospheric pollution be considered a co-factor in extremely high level of sars-cov-2 lethality in northern italy? detection of 2019 novel coronavirus (2019-ncov) by real-time rt-pcr. euro surveillance bulletin europeen sur les maladies transmissibles environmental viral contamination in a pediatric hospital outpatient waiting area: implications for infection control pollen exposure weakens innate defense against respiratory viruses grampositive bacteria on grass pollen exhibit adjuvant activity inducing inflammatory t cell responses evidence of long-distance transport of betula pollen electrochemical detection of airborne influenza virus using air sampling system air quality variation in wuhan, daegu, and tokyo during the explosive outbreak of covid-19 and its health effects airborne transmission of sars-cov-2: the world should face the reality pollen-associated microbiome correlates with pollution parameters and the allergenicity of pollen artemisia pollen is the main vector for airborne endotoxin nearground effect of height on pollen exposure sars-cov-2rna found on particulate matter of bergamo in northern italy: first evidence aerosol and surface stability of sars-cov-2 as compared with sars-cov-1 methods for sampling of airborne viruses. microbiol innovations in air sampling to detect plant pathogens clinical characteristics of 140 patients infected with sars-cov-2 in wuhan studies were co-financed by the german science foundation via the idiv-flexpool (project 100269858). we especially want to thank the dr. födisch umweltmesstechnik ag for the author regina treudler indicated sanofi genzyme, novartis, alk-abello, abbvie, shire, fraunhofer institute izi and hautnetz leipzig e.v. as potential conflicts of interest.j o u r n a l p r e -p r o o f key: cord-296661-6ndn2qxc authors: lu, dingnan; huang, zhuangrong; luo, jiayue; zhang, xiaoqi; sha, sha title: primary concentration – the critical step in implementing the wastewater based epidemiology for the covid-19 pandemic: a mini-review date: 2020-07-25 journal: sci total environ doi: 10.1016/j.scitotenv.2020.141245 sha: doc_id: 296661 cord_uid: 6ndn2qxc abstract the recent outbreak of a novel coronavirus sars-cov-2 has posed a significant global public health threat and caused dramatic social and economic disruptions. a new research direction is attracting a significant amount of attention in the academic community of environmental sciences and engineering, in which rapid community-level monitoring could be achieved by applying the methodology of wastewater based epidemiology (wbe). given the fact that the development of a mass balance on the total number of viral rna copies in wastewater samples and the infected stool specimens is the heart of wbe, the result of the quantitative rna detection in wastewater has to be highly sensitive, accurate, and reliable. thus, applying effective concentration methods before the subsequent rna extraction and rt-qpcr detection is a must-have procedure for the wbe. this review provides new insights into the primary concentration methods that have been adopted by the eighteen recently reported covid-19 wastewater detection studies, along with a brief discussion of the mechanisms of the most commonly used virus concentration methods, including the peg-based separation, electrostatically charged membrane filtration, and ultrafiltration. in the end, two easy and well-proven concentration strategies are recommended as below, aiming to maximize the practical significance and operational effectiveness of the sars-cov-2 virus concentration from wastewater samples. strategy1: prefiltration-salt addition-electronegative membrane filtration (for initial volume ≤ 50 ml). strategy2: prefiltration-peg-based separation-overnight standing (for initial volume from 50 to 1000 ml). the recent outbreak of a novel coronavirus sars-cov-2, also known as the covid-19 disease, has posed a significant global public health threat and causes dramatic social and economic impacts. as of june 19, 2020, the world health organization (who) has reported more than 14,000,000 infected people globally (who, 2020) . as a completely novel human coronavirus, the response of the global public health authorities and the academic communities to the covid-19 demonstrated an inevitable lag due to the lack of understanding of the sars-cov-2 virus as well as rapid detection methods. indeed, the conventional epidemiology highly relies on the systematic diagnosis of excretion samples and clinical symptoms, which is inherently difficult for the detection of a highly infectious disease from a large population in a timely manner. in 2001, a concept, namely wastewater based epidemiology (wbe), was first proposed to estimate the drug abuse situation in a community by analyzing the pharmaceutical concentration in wastewater (daughton and jones-lepp, 2001) . as described by daughton and jones-lepp (2001) , any substance excreted by humans in wastewater could be traced back to its initial source concentration, as j o u r n a l p r e -p r o o f 4 long as the substance or its metabolites are stable in wastewater to some degree. a similar concept of wbe has been previously adopted to evaluate the prevalence of infectious diseases caused by pathogens. for example, kazama et al. (2017) successfully conducted a cross-correlation analysis between the concentrations of norovirus gi or gii in weekly collected sewage samples and the reported number of gastroenteritis cases. as a result, applying the methodology of wbe to achieve rapid community-level monitoring of the covid-19, along with the fast-rising public awareness and emerging scientific studies, has attracted a significant amount of attention. the development of a rapid and economical wbe can facilitate and empower a local public health authority to achieve real-time surveillance and future outbreak prediction of the covid-19 pandemic (lesté-lasserre, 2020; mallapaty, 2020; murakami et al., 2020; sims and kasprzyk-hordern, 2020 ). there are some critical challenges that we have to overcome before wbe can be applied to accurately reflect the real-time situation of the covid-19 pandemic within a sewer-delimited community. among all the challenges, the most immediate one is the relatively low viral particle loadings in large volumes of wastewater (ikner et al., 2012) . thus, to obtain accurate results with statistical significance, applying effective concentration methods before the subsequent extraction and detection of virus particles is a must-have procedure for wbe. as a result, the primary concentration method is the core process because it has the most significant influence over a complete concentration process. for example, an early method for concentrating poliovirus from various water samples was developed using a soluble material of sodium alginate to build filters to concentrate viral particles (gaertner, 1967; nupen, 1970) . after filtration, the adsorbed filters will then be dissolved in a small volume of sodium citrate to elute the viral particles and subsequently conducted cell culture infectivity assays for virus detection. it is clear that the development of the soluble sodium alginate filters as the primary concentration method directly determines the next elution step to must adopt sodium citrate as the eluting reagent. furthermore, due to the nature of soluble alginate filter materials, water samples with high turbidities, such as wastewater, have to conduct pretreatment by passage through a series of filters to reduce the clogging risk during the final virus concentration. in summary, the characteristics of a primary concentration method can exert significant influence on the overall concentration process by determining if the subsequent extraction and detection method can be successfully applied to fulfill the goals of wbe. according to a recent review, some early developed methods that have been historically used to concentrate enteric viruses from wastewater samples may be subject to some technical issues, due to the sars-cov-2 virus is relatively unstable in the environment and is more susceptible to common oxidants (la rosa et al., 2020a) . therefore, an effective concentration strategy has to be selected or developed in the first place. given that many relevant techniques have been developed and refined over the past decades, this mini-review discusses the potential advantages and disadvantages of different concentration strategies with an emphasis on the primary concentration methods and the suitability for the covid-19 web. meanwhile, this mini-review puts a particular focus on several existing analytical studies of the sars-cov-2 virus in the wastewater matrix and evaluate their concentration strategies before the subsequent extraction and detection processes. at last, two concentration strategies are recommended to maximize the practical significance and operational effectiveness of the sars-cov-2 virus concentration from wastewater samples. a number of methods have been developed to effectively concentrate viral particles from water samples. based on various concentrating mechanisms, we can classify all the different primary concentration methods into four broad types, namely (1) two-phase separation/partition precipitation, (2) particle exclusion, (3) viruses adsorption -elution (viradel), and (4) ultrafiltration. it is worth mentioning that the viradel method using electrostatically charged microporous materials as filtration media is the most prevalent technique used today (ikner et al., 2012) , which can be further categorized as electronegative membrane filtration and electropositive membrane filtration based on surface charge differences (see table 1 ). along with the continuous evolution of the primary concentration methods, many of early methods have been scarcely used or phased out due to some inherent disadvantages, such as small treatment volumes (hydroextraction), poor recovery performance (cotton gauze pads), and excessive pretreatment processes (soluble membrane filtration). in this section, three of the most j o u r n a l p r e -p r o o f commonly used methods (i.e., peg-based two-phase separation, viradel method, and ultrafiltration) will be briefly discussed and compared on the basis of recovery performance, ease of operation, and consistency of concentrating outcome. also worth noting is that the peg-based two-phase separation and the viradel method currently are the only two standard methods adopted by the world health organization (who/v-b03.03) and the u.s. environmental protection agency (epa method 1615) respectively. using polyethylene glycol (peg) based two-phase separation on concentrating viruses between two immiscible aqueous polymer phases was first proposed by albertsson and frick (1960) . during the 1960s and 1970s, the method of aqueous polymer two-phase separation was continuously refined for the purpose of concentrating enteroviruses over a broad spectrum of water quality matrices, such as river water, tap water, groundwater, and wastewater (shuval et al., 1969; wallis et al., 1969) . based on the result reported by shuval et al. (1969) , after mixing with a combination of organic polymers (i.e., dextran and peg), a sewage sample of several liters can be successfully concentrated for subsequent viruses detection with an average nominal concentration factor of 220-fold and an average recovery efficiency of 72 %. the peg-based separation method was eventually adopted by the who as a standard method for conducting environmental surveillance of poliovirus circulation (who, 2003) . in summary, the pegbased separation method has been extensively studied to concentrate and purify various viruses (e.g., bacteriophage t2, adenovirus, poliovirus, and echo virus) and found to be rapid, inexpensive, consistent, and non-destructive of viruses. in addition, commercial peg virus precipitation kit (biovision) has recently become available as a convenient, affordable alternative (~$4 -$6 per unit). however, due to the limited size of most separation funnels (maximum for several liters), the peg-based separation method has an apparent drawback, which is only useful for concentrating samples with a relatively small volume (as shown in figure 1a) . as a result, a raw water sample must contain a moderate to high viruses loading to ensure enough viruses get concentrated from the limited initial treatment volume. j o u r n a l p r e -p r o o f the first attempt of the viradel method to concentrate enterovirus can be traced back to the 1960s when wallis and melnick (1967) found the addition of sodium chloride (nacl) or magnesium chloride (mgcl 2 ) can lead to the adsorption of poliovirus on cellulose nitrate ha membranes (0.45 µm). superior performances of virus concentration were achieved with much less addition of trivalent aluminum salts (alcl 3 and al 2 (so 4 ) 3 ) when controlling the ph to below 5 (wallis et al., 1972) . this phenomenon is mainly associated with the adsorption of metal ions to the electronegatively charged surface of cellulose nitrate ha membranes, thereby facilitating the attachment of polioviruses via saltbridging (ikner et al., 2012) . although the electronegatively charged membranes can effectively extract viruses from water samples, the addition of polyvalent salts makes it difficult for concentrating large volume samples. as a result, a number of early studies tried in situ charge modification of electronegative filters and successfully developed electropositive membrane filtration method, the most common technique (i.e., viradel) currently used for concentrating viruses from water (farrah and preston, 1985; haramoto et al., 2004; sobsey and jones, 1979; zerda et al., 1985) . according to the standard method (i.e., epa method 1615), electropositive filters (e.g., nanoceram and 1mds) are capable of continuously extracting enterovirus and norovirus from groundwater and surface water with the minimum specified volumes of 300 l and 1,500 l, respectively (see figure 1b ) (fout et al., 2015) . however, the presence of organic matter can lead to significantly reduced efficiency of virus concentration due to a preferential attachment of dissolved organic molecules over virus particles. in addition to the presence of organic matter, high water turbidity ( 50 ntu) can directly lead to the failure of sampling when applying the epa method 1615 with the recommended nanoceram virus sampler (fout et al., 2015) . it is, therefore, inappropriate to apply the epa method 1615 directly to concentrate virus particles from raw wastewater samples that are usually turbid and contain a substantial amount of dissolved and suspended organic matter. j o u r n a l p r e -p r o o f 8 unlike the peg-based separation and electropositive membrane filtration, using ultrafiltration to extract viruses will not be subject to preconditioning of the water samples, which allows this method to be used over a broad range of water quality (hill et al., 2007) . the earliest study that used ultrafiltration to concentrate poliovirus from a water sample was designed using multiple layers of asymmetric cellulose acetate membranes to separate flow channels for raw water samples and driving solution, and achieved recovery efficiency of 95 -100 % from a large volume of water of 10 l (sweet et al., 1971) . later studies using polysulfone hollow fiber ultrafilters demonstrated better resistance to ph and temperature variations, biological degradation, and showed less penetration of target virus particles due to the dense inner surface (ikner et al., 2012) . in terms of the ultrafiltration flow types, tangential crossflow ultrafiltration is a commonly used configuration, which can effectively prevent fouling due to the rapid, tangentially directed crossflow. it is, therefore, particularly suited for extracting viruses from lower quality water samples such as wastewater (ikner et al., 2012) . although tangential flow crossflow ultrafiltration can provide superior virus recoveries from low-quality water, the equipment required for conducting crossflow ultrafiltration is usually large, immobile, and not field portable (hill et al., 2007) . high recovery rate; useful over a broad spectrum of water quality matrices small treatment volumes; inhibition of virus activity (adams, 1973; colombet et al., 2007; lewis and metcalf, 1988; who, 2003) multistage ultracentrifugation (1,000 to 100,000g) small treatment volumes; largescale instrument required; excessive processing time (fumian et al., 2010; gias et al., 2008) dialysis separation (hydroextraction) preferable recovery rate small treatment volumes; inhibition of virus activity (ramia and sattar, 1979; ramia and sattar, 1980) metallic oxides /peroxides/salts precipitation large treatment volumes pretreatment required for raw aqueous samples; excessive chemical consumptions (farrah et al., 1986; preston and farrah, 1991) particle exclusion non-cytotoxic; preferable recovery rate small treatment volumes; pretreatment required for raw aqueous samples (gaertner, 1967; nupen, 1970) cotton gauze pads filtration large treatment volumes; inexpensive low recovery rate; poor quantitative performance (hill et al., 1971; liu et al., 1971) viradel 1 large treatment volumes; preferable recovery rate preconditioning required; highly sensitive to organic matters in aqueous samples (chalapati rao et al., 1972; haramoto et al., 2004; hata et al., 2015) electropositive membrane filtration large treatment volumes; preferable recovery rate; no need of preconditioning highly sensitive to organic matters in aqueous samples (hsu et al., 2007; ikner et al., 2011; lambertini et al., 2008) ultrafiltration high recovery rate; consistent performance; no need of eluting addition of blocking solution required (e.g., glycine or beef extract); backflushing may be needed (divizia et al., 1989; hill et al., 2007; liu et al., 2012; rajal et al., 2007; winona et al., 2001 ) 1 viradel stands for viruses adsorption -elution. it is clear that the primary concentration methods described above are all developed and refined to concentrate the non-enveloped enteric viruses, which are naturally acclimated to the water environment and capable of causing waterborne infectious disease via fecal-oral route (ikner et al., 2012) . compared with the non-enveloped viruses, the enveloped viruses possess outer surface structures consisting of different functional groups, which may significantly impact their survival and partitioning behavior in an aqueous environment (ye et al., 2016 ). an early study focusing on the evaluation of the survivability of an enveloped human coronavirus (hcov) in the wastewater environment, reported that the time required for the hcov titer to decrease by 99.9 % (t 99.9 ) is substantially shorter than the non-enveloped poliovirus 1 (pv-1) (gundy et al., 2008) . in terms of the primary concentration performance, as shown in table 2, under the same conditions, most of the enveloped viruses showed relatively lower recovery rates compared to the non-enveloped viruses. for example, with the optimized ultrafiltration method, ye et al. (2016) reported mean recoveries of 25.1 ± 3.6 % and 18.2 ± 9.5% for the enveloped murine hepatitis virus (mhv) and pseudomonas phage ϕ6, respectively. meanwhile, the non-enveloped enterobacteria phage t3 and ms2 demonstrated significantly higher mean recoveries of 55.6 ± 16.7 % and 85.5 ± 24.5%, respectively, when using the same ultrafiltration method. in randazzo et al. (2020) 's study, the aluminum hydroxide precipitation method showed the closest primary concentration recovery when concentrating wastewater influent samples with spiked porcine epidemic diarrhea virus (pedv), an enveloped virus member of the coronaviridae family, and mengovirus (mgv), a non-enveloped member of the picornaviridae family, of 11 ± 3.5 and 11 ± 2.1 %, respectively. however, the overall low recovery rate (~ 3 to 11 %) may hinder this method to be widely adopted for the detection of the sars-cov-2 virus. due to the characteristics of the enveloped viruses, including the sars-cov-2 virus, most of the concentration methods tend to result in a higher decay or inactivation for the enveloped viruses than the non-enveloped viruses. another risk we face is the reduced viability and infectivity of the virus after a concentrating process. the increased sensitivity of the molecular detection method (i.e., rt-qpcr) has partially alleviated the problem of reducing the viability and infectivity of the viruses because the j o u r n a l p r e -p r o o f quantitative determination is no longer based on the traditional cell culture infectivity assays, which heavily relied on the viability, infectivity, and structural integrity of the concentrated viruses (ikner et al., 2012) . however, it is critical to recognize the technical capabilities/limitations of all the processes and techniques used so we can optimize each step involved to help minimize the loss of the original characteristics of the samples. j o u r n a l p r e -p r o o f 13 after carefully identifying the methodologies of these articles, we found the majority of them (17 out of 18) applied primary concentration methods to concentrate the sars-cov-2 virus particles or the genomic fragments from the wastewater samples (see table 3 ). the peg-based separation is the most used technique (7 out of 18) among all concentration methods, and all four studies that adopted this concentration method showed positive results regarding the sars-cov-2 detection in wastewater samples (bar or et al., 2020; hata et al., 2020; la rosa et al., 2020b; wu et al., 2020) . as summarized in table 3 , most of the studies that implemented the peg-based separation method (6 out of 7) also had additional follow-up processes, such as ultracentrifugation and overnight standing, to further condense the obtained peg layer. although ultracentrifugation can significantly reduce the final water content in the obtained peg layer, the initial cost to obtain an ultracentrifuge may pose a cost-prohibitive obstacle for many analytical laboratories, especially for those in the wastewater treatment plants that typically can only conduct routine wastewater analyses. in comparison, overnight standing at 4 °c in a separation funnel maybe not as effective as the immediate ultracentrifugation. however, this approach is significantly easier to achieve because it only requires a refrigerator, which is readily available in most of the laboratories. in terms of the preconditioning process, most of the studies using the peg-based separation method (5 out of 7) had applied the centrifugation method to remove sediment and large particles from raw wastewater samples. similarly, centrifugation is a fast and effective method to precondition a raw wastewater sample, but it requires sizeable centrifuges when handling a relatively large volume of wastewater samples. thus, we believe the prefiltration method adopted by wu et al. (2020) using 0.2 μm membranes is more feasible and accessible than centrifugation. it should be noted that the prefiltration method may capture viruses that were previously attached to large particles during the preconditioning process, and therefore, retaining the resulted cake for the subsequent elution together with the separated peg-layer is highly recommended. (rimoldi et al., 2020) a murine hepatitis virus (mhv), was used to test the efficiency of seven wastewater virus concentration methods: (a, b, c) electronegative membrane with three different pretreatment options, (d, e) centrifugal ultrafiltration with two molecular weight cut-off, (e) peg-based two-phase separation, and (g) ultracentrifugation (ahmed et al., 2020b) , b sampling volume based on the container size mentioned in the reference (rimoldi et al., 2020) . among all the sars-cov-2 detection studies, the electronegative membranes filtration technique was adopted for primary concentration in 3 of the 18 studies. in terms of the preconditioning method, these three studies are highly representative of the current development of the electronegative membrane filtration technique. specifically, ahmed et al. (2020a) (pmmov) as a detection biomarker and resulted in high rna results of 2.6  10 6 copies/l. as previously mentioned, using electrostatically charged membranes filtration to concentrate viruses from turbid water, such as raw wastewater, can be subject to a significant reduction of virus recovery efficiency due to the presence of organic matter and high turbidity, which can lead to a preferential attachment to the charged filters and raise the risk of detrimental clogging. however, in these studies, there is no compelling evidence to suggest that the organic materials from wastewater have a severe impact on the virus adsorption. this phenomenon is probably attributed to the relatively small volume that both studies involved, therefore alleviated the adverse impact from the high organic content in the wastewater samples. we found four studies that implemented the ultrafiltration technique as the primary concentration strategy. among them, two studies chose 100 kda as the molecular weight cut-off (medema et al., 2020; nemudryi et al., 2020) , and the other two studied chose to adopt a much smaller molecular weight cut-off, such as 10 kda and 30 kda (ahmed et al., 2020b; wu et al., 2020) . interestingly, all these studies employed, to some extent, precondition step, which is unnecessary when using the ultrafiltration j o u r n a l p r e -p r o o f technique to conduct the primary concentration (fout et al., 2015; rajal et al., 2007) . for example, nemudryi et al. (2020) (hart and halden, 2020) . however, it should not be ignored the ultrafiltration method used by hart and halden (2020) is one of the essential requisites which played vital roles in this successful effort. collectively, all concentration methods showed positive results regarding the sars-cov-2 virus detection in wastewater. in terms of treatment volume, all studies tend to work with a small amount (e.g., less than 1 l), which is likely due to the risk of potential enteric transmission of the covid-19 in a wastewater sample. also, handling a large volume of wastewater in an epidemic area may pose a significant infectious risk to the research team members. another critical factor in the wastewater virus concentration lies in the degree of the primary concentration efficiency (i.e., the recovery rate of the primary concentration step). a superior concentration efficiency indicates a relatively small portion of virus loss during the concentrating procedure, ensuring a higher sensitivity of the overall detection process. most importantly, the final concentration of the virus in a wastewater sample has to be calculated by dividing the subsequent rt-qpcr result by the primary concentration efficiency. technically, spiking of a surrogate virus (e.g., f-specific rna phage) with known concentrations as an internal reference is the most common practice to obtain this critical efficiency information. after screening all the found j o u r n a l p r e -p r o o f studies, five different research teams did employ internal reference(s) to facilitate the analysis of the primary concentration efficiency, and the result is presented in table 4 . as of now, we have found only one comprehensive study that systematically compares the efficiency of different primary concentration methods for the covid-19 wastewater analysis (ahmed et al., 2020b) . as shown in table 4 , four types of primary concentration methods were conducted to concentrate the spiked murine hepatitis virus (mhv) in the wastewater influent. according to the reported concentration efficiencies, the electronegative membrane filtration method with the addition of magnesium chloride resulted in the highest mean recovery rate. it appears that the high recovery rate of the electronegative membrane filtration method was mainly associated with skipping over any prefiltration and pre-centrifugation step, which maximized the internal reference (i.e., the spiked mhv) to be adsorbed from both the liquid and solid fractions of the wastewater sample simultaneously (ahmed et al., 2020b) . such approach will significantly improve the adaptability of this method when it comes to handling a highly turbid influent sample. again, the risk of membrane clogging has to be carefully addressed when dealing with a medium-sized turbid influent sample (e.g., 500 ml). this is because the electronegative membrane filtration method requires a sample to pass through a membrane filter, which typically has a small pore size of less than 1.0 µm. in terms of the peg-based separation method, both studies showed moderate-to-high recovery efficiencies of 44 % and 57 %, respectively (ahmed et al., 2020b; hata et al., 2020) . the relatively higher recovery rate of 57 % reported by hata et al. (2020) was achieved with a single-step pretreatments of centrifugation at 5,000 g for 5 minutes to remove large particles from raw influent samples. in comparison, hata et al. (2020) adopted a more complex pretreatment process of (1) ultracentrifugation at 10,000 g for 20 min, (2) resuspension of the obtained pellet in 0.05 m glycine, (3) ultracentrifugation at 10,000 g for 10 min, (4) combination of the supernatants from both ultracentrifugation processes, and (5) ph neutralization by adding 2 m hcl. as the peg-based separation method have been developed and j o u r n a l p r e -p r o o f refined since 1960s, different pretreatments aiming to improve its efficiency and adaptability have also been proposed and applied, which may result in overly complicated procedures. as a result, particular attention should be paid to the additional pretreatment steps used in the overall concentration process because of the possibility of the unforeseeable loss of viruses along with the processing. as mentioned previously in section 3, the aluminum hydroxide precipitation method showed low recovery rates (~ 3 to 11 %) in all wastewater samples, and the difference in recovery rate between the spiked enveloped and non-enveloped virus in influent samples is statistically insignificant, indicating the method has a similar efficiency of concentrating enveloped and non-enveloped virus from an influent sample (randazzo et al., 2020) . comparing to the aluminum hydroxide precipitation method, all other techniques showed better recovery rates. for example, medema et al. (2020) reported a significantly higher recovery rate of 73 ± 50 % by concentrating the f-specific rna phages with centrifugal ultrafiltration (100 kda molecular weight cut-off). however, the high recovery rate of 73 % was subject to a noticeably large relative standard deviation (rsd) of ± 50%, which may reduce the application implication of the centrifugal ultrafiltration method. it should be noted that the issue of a low average recovery rate can be compensated, to some extent, by applying a large initial volume. however, the issue of data scattering (i.e., large rsd) might have a more detrimental effect on the accuracy of the finalized virus concentration estimation because the final virus concentration has to be normalized by a recovery rate, and a large rsd can significantly increase the uncertainty. by combining the previously published studies of virus detection in wastewater with the most recent reports regarding the covid-19 wbe, this review will provide some specific suggestions, in the section entitled "5. recommendations," for which technique(s) should be chosen and what preconditioning approach(es) should be adopted when conducting the sars-cov-2 wastewater detection. j o u r n a l p r e -p r o o f in 18 studies that we found relevant to the wastewater sars-cov-2 detection, the initial sampling volume was all relatively small. for example, a small volume of 40 ml prefiltered wastewater sample can be successfully concentrated by using the peg-based separation combined with the ultracentrifugation and subsequently detected via rt-qpcr to result in the sars-cov-2 n1 genomic fragments of 50 to 250 copies /ml of raw wastewater (wu et al., 2020 including a small to medium-sized concentrating capacity, an easy to access and operate procedure, a reliable and efficient performance, and, most importantly, strong adaptability to a broad range of water quality. as a result, we highly recommend using the electronegative membrane filtration method with the addition of magnesium chloride as the primary concentration method when dealing with a small initial volume (i.e., less than 50 ml). in case of the potential clogging risk, when handling a medium-sized influent sample (i.e., 50 to 1,000 ml), we suggest using the peg-based separation method followed by overnight standing at 4 °c in a separation funnel as the alternative primary concentration method. due to the typically high turbidity of an untreated influent sample, the removal of large particles, such as sand, debris, and hair, could be achieved by passing through filters with a large pore size (e.g., 5 or 20 μm), if needed. the recommended two primary concentration processes can be achieved without any large laboratory equipment. at the same time, the main consumables are limited to the filter membranes and chemicals (i.e., magnesium chloride for the electronegative membrane filtration method and polyethylene glycol for the peg-based separation method, respectively) (see figure 2 ). in summary, these two proposed methods are easy to use, free of large laboratory equipment, proven concentration efficiency, and highly accessible over a broad range of research facilities. due to the recent outbreak of the covid-19 pandemic, wastewater based epidemiology starts to attract a significant amount of attention. the fundamental idea is to quantitatively detect the sars-cov-2 virus rna from wastewater samples and then use this information to conduct infection prevalence estimation. to accurately reflect the epidemic situation, the detection technique must be highly sensitive and reliable. therefore, developing a simple, effective primary concentration method before the sars-cov-2 rna extraction and detection processes is of great significance. this mini-review first discussed several commonly used primary concentration methods, including the peg-based separation, electrostatically charged membrane filtration, and ultrafiltration. after that, a particular emphasis was put on the eighteen existing sars-cov-2 wastewater analytical studies. based on the primary concentration methods implemented in these studies, we present the following conclusions: 1. this review work highlights the importance of having an easy to access and operate primary concentration method because implementing the real-time wastewater surveillance has to be based on the high availability of wastewater data. 2. due to the positive results obtained with small initial volumes in all the reported studies, the main drawback (i.e., small concentrating capacity) of the peg-based separation and the electrostatically charged membrane filtration can, to some extent, be ignored. 3. as of now, the peg-based separation method is the most prevalent method used for the covid-19 wastewater based epidemiology. 4. the electronegative membrane filtration method can be carried out without any prefiltration and pre-centrifugation and still produce the most desirable concentration efficiency. 5. although the electronegative membrane filtration method has been proved experimentally, future studies should be careful about the preferential adsorption of organic matter on the charged membrane surface and the potential risk of clogging when handling turbid samples. j o u r n a l p r e -p r o o f 23 6. ultrafiltration can provide high recoveries and consistent performance, but an ultrafiltration system is usually large, immobile, and not readily available in most laboratories. 7. we recommend two simple and straight-forward primary concentration strategies: (1) prefiltration -salt addition -electronegative membrane filtration (volume  50 ml). 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cellulose membranes concentration of enteroviruses on membrane filters concentration and detection of sars coronavirus in sewage from xiao tang shan hospital and the 309th hospital world health organization, switzerland, 2003. who. coronavirus disease 2019 (covid-19) situation report -181. world health organization sars-cov-2 titers in wastewater are higher than expected from clinically confirmed cases evaluation of lockdown impact on sars-cov-2 dynamics through viral genome quantification in paris wastewaters survivability, partitioning, and recovery of enveloped viruses in untreated municipal wastewater adsorption of viruses to charge-modified silica the authors would like to acknowledge the university of massachusetts lowell (uml) andmassachusetts institute of technology (mit) for the acquisition of the latest literature and information regarding the covid-19 pandemic used in this analysis work. the authors declare no competing interests. key: cord-284583-urh0xk7r authors: singh, vikas; singh, shweta; biswal, akash title: exceedances and trends of particulate matter (pm2.5) in five indian megacities date: 2020-08-11 journal: sci total environ doi: 10.1016/j.scitotenv.2020.141461 sha: doc_id: 284583 cord_uid: urh0xk7r abstract fine particulate matter (pm2.5) is the leading environmental risk factor that requires regular monitoring and analysis for effective air quality management. this work presents the variability, trend, and exceedance analysis of pm2.5 measured at us embassy and consulate in five indian megacities (chennai, kolkata, hyderabad, mumbai, and new delhi) for six years (2014–2019). among all cities, delhi is found to be the most polluted city followed by kolkata, mumbai, hyderabad, and chennai. the trend analysis for six years for five megacities suggests a statistically significant decreasing trend ranging from 1.5 to 4.19 μg/m3 (2%–8%) per year. distinct diurnal, seasonal, and monthly variations are observed in the five cities due to the different site locations and local meteorology. all cities show the highest and lowest concentrations in the winter and monsoon months respectively except for chennai which observed the lowest levels in april. all the cities consistently show morning peaks (~08: 00–10:00 h) and the lowest level in late afternoon hours (~15:00–16:00 h). we found that the pm2.5 levels in the cities exceed who standards and indian naaqs for 50% and 33% of days in a year except for chennai. delhi is found to have more than 200 days of exceedances in a year and experiences an average 15 number of episodes per year when the level exceeds the indian naaqs. the trends in the exceedance with a varying threshold (20–380 μg/m3) suggest that not only is the annual mean pm2.5 decreasing in delhi but also the number of exceedances is decreasing. this decrease can be attributed to the recent policies and regulations implemented in delhi and other cities for the abatement of air pollution. however, stricter compliance of the national clean air program (ncap) policies can further accelerate the reduction of the pollution levels. air quality in megacities is a major concern for human health where a large portion of the population lives, and the pollution levels often exceed the limit values (kumar et al., 2015; zheng et al., 2017) . among all pollutants, pm 2.5 (particles less than 2.5 micrometers in diameter) poses a greater risk as it can penetrate deep into the human body (xing et al., 2016) . it has been estimated that exposure to outdoor pm 2.5 is the fifth leading risk factor worldwide and the third leading risk factor in india (gbd 2015 risk factors collaborators, 2016 . globally, exposure to pm 2.5 accounts for 4.2 million deaths and over 100 million disability-adjusted life-years in 2015 (gbd 2015 risk factors collaborators, 2016 . a growing number of epidemiological evidence of acute and chronic impacts of pm 2.5 on human health, besides its role in perturbing weather and climate (fuzzi et al., 2015) , has led the scientific community to monitor levels of pm widely across urban, suburban and rural regions of different countries in the last decade. however, inter-comparison of these results is not always possible either because of the difference in sampling or monitoring instrument or due to different sampling duration. this requires a sampling network that works on one principle with large spatial coverage. in recent times, united states environment protection agency (us-epa) has come up with pm 2.5 monitoring at the u.s. embassy and consulates (usec) in various countries using federal equivalent method (fem) approved instrument beta attenuation monitor (bam-metone 1020) and is providing hourly measurements of pm 2.5 in 27 countries of the world. this usec data has been used for the study of pm 2.5 levels in the urban environment for different purposes viz; to study the trend and characteristics of pm 2.5 ( chen et al., 2020; fontes et al., 2017; sreekanth et al., 2018; liang et al., 2016; batterman et al., 2016; san martini et al., 2015) , to compare with other data and model evaluation (jiang et al., 2015; li, figure 1 . open street maps of the 2km × 2km area surrounding the embassy/consulates (red circle) to show the geographical location of the five indian megacities (a. chennai, b. kolkata, c. hyderabad, d. mumbai, e. new delhi) . while meteorology plays an important role in controlling the air quality, the local emission sources mainly household and traffic emissions (singh et al., 2018a) the pm 2.5 concentrations across all the sites are monitored in real-time using fem bam-1020, having a standard range of 0-1000 µg m -3 , resolution of ±0.1 µg m -3 and 24 h average lower detection limit less than 1.0 µg m -3 , and the data is processed using a common quality control protocol defined by usepa (ray & vaughn, 2013) . however, we find that there are still negative values with valid flag and outliers (sudden spikes) present in the data set. therefore, we have further processed a quality control check to remove the outliers. any data point which is more than three local scaled median absolute deviations (mad) from the local median of the data within a running window of 6 hours has been considered as an outlier. as 7 the modern-era retrospective analysis for research and applications, version 2 (merra-2) hourly surface reanalysis meteorological products from 1 january 2014 to 31 december 2019 has been obtained from nasa's global modeling and assimilation office (gmao). these products are available at a horizontal resolution of 0.5°× 0.625° (https://gmao.gsfc.nasa.gov/reanalysis/merra-2/). details of the merra-2 products and evaluation has been reported by gelaro et al., (2017) , randles et al., (2017) and . the hourly meteorological data (wind, temperature, precipitation, planetary boundary layer height-pblh) have been extracted from the corresponding grids of the latitude and the longitude of the five megacities (supplementary table 2 the air quality data has been analyzed from 2014 to 2019. we have used seasonal trend decomposition procedure based on loess (locally weighted scatterplot smoothing) smoothing (stl) (cleveland et al., 1990) to estimate the trend in pm 2.5 as adopted by bigi and ghermandi (2016) to study the trend in pm 2.5 in the po valley, italy. stl is a widely used filtering procedure for decomposing time series into three components: trend, seasonal, and remainder or residual. the decomposition is based on a sequence of smoothing procedures using a locally weighted regression known as loess (cleveland et al. 1990 ). the loess smoother is based on fitting a weighted polynomial regression for a given time of observation, where weights decrease with distance from the nearest neighbor. time-series of monthly mean pm 2.5 concentration at all five megacities were decomposed in trend, seasonal, and remainder components using stl procedure (cleveland et al., 1990) . as the pm 2.5 data is not normally distributed (supplementary figure 1) , time-series data were log-transformed before stl decomposition to attain normally distributed residuals and to control heteroscedasticity. time-series data were back-transformed from logarithmic decomposed data to analyse the trend. a significant slope in the monthly trend component was calculated using generalized least squares (gls) regression (brockwell and davis, 2002) for each site within a 95% confidence interval (ci) with a significance level (alpha=0.05). gls is used to j o u r n a l p r e -p r o o f journal pre-proof estimate the linear relation between an autocorrelated time series and time to obtain independent residuals and a correct estimate of the variance of the regression coefficients. stl and gls analysis were performed using r software. exceedance analysis has been performed and the number of threshold exceedances has been calculated by keeping the threshold of daily mean pm 2.5 equal to 60 µg/m 3 and 25 µg/m 3 as per naaqs (cpcb, 2009) and who (who, 2005) standards respectively. the linear trend (singh et al., 2018b) in the annual exceedances in six years has been calculated for each site within 90% confidence interval (ci) with a significance level (alpha=0.1) because of the small sample size (labovitz, 1968) . we have also calculated the number of pollution episodes and the length of each episode. an episode has been considered when the daily mean pm 2.5 has exceeded continuously for three or more days. the variation in the pm 2.5 levels for a location is an interplay of emissions, geography, and meteorological conditions (alimissis et al., 2018; ganguly et al., 2019; nair et al., 2007) . previously, the diurnal and seasonal variations have been reported for five cities for the period of fewer than four years 2013-2016 by sreekanth et al. (2018) and for four cities excluding kolkata for four years (2015-2018) by chen et al. (2020) . however, these studies did not discuss the trend in the pm 2.5 . various pollution mitigation schemes along with the public awareness programs (ncap, moefcc, 2019) have been implemented in india since the availability of the usec data. therefore, we analysed the data for a longer period of six years for all available usec sites in india to study the trend, exceedance and variations in details. the diurnal variation of pm 2.5 for chennai, kolkata, hyderabad, mumbai, and new delhi is presented in figure 2 all the cities consistently show morning peaks around (~08:00-10:00 hrs). a shift of up to two hours in the morning peak hours is due to the season and the geographical location. for a city, the winter peak appears at a later hour of the day than the summer peak hour because of late sunrise and onset of human activities in winter. among all, the cities located in the eastern side of india (kolkata, chennai, and hyderabad) show a peak around an hour earlier than the cities located further west (delhi and mumbai) because of the early sunrise and human activities in the eastern cities. the cities hyderabad and chennai show a sharp peak during morning traffic hours, whereas the same is not true for new delhi, mumbai, and kolkata. the higher levels of pm2.5 during nighttime leads to a smaller peak during morning traffic peak hours. a similar study carried out by chen et al. (2020) has attributed this to the higher population of mumbai and new delhi. this may not be the sole reason as the population of hyderabad and chennai are also large enough to enhance the nighttime emissions. the traffic sources in the vicinity of the monitoring station ( figure 1 ) along with the local meteorology may be responsible for the sharp peak during the morning hours. the morning peak is attributed to the morning fumigation effect after the sunrise (stull, 2012; nair et al. 2009 ), along with morning traffic and household emissions (tiwari et al., 2013b) trapped within the evolving shallow boundary layer. the diurnal peak of pm 2.5 occurs in the morning hours for all the cities except for kolkata where the peak pm 2.5 is found at midnight. for kolkata, a similar variation in bc has been reported by talukdar et al. (2015) who have also shown the highest peak for bc during midnight rather than morning traffic peak time. this could be due to the late evening household emissions. moreover, higher wind prevalence in the day time on account of stronger sea breeze during the early morning to afternoon as compared to the other periods of the day (gururaja et al., 2019) can also explain the lower concentration in the day time as compared to the night in kolkata. we also calculated the ratio of the highest to the lowest monthly mean pm 2.5 concentration for a city to know the extent of the variability within a year. as the highest pollution levels are found in winter and lowest in monsoon, it can also be considered as the most polluted to the cleanest ratio. this ratio is found to be high for kolkata (6.98) and delhi (6.82) followed by mumbai (4.9), hyderabad (3.18), and chennai (2.98). this suggests that for kolkata and delhi, the winter months pm 2.5 levels can be 7 times higher than the monsoon levels. journal pre-proof here we utilize the usec pm 2.5 data to calculate the annual trend with the monthly mean pm 2.5 across all five indian cities for six years. monthly mean pm 2.5 time series at all five locations were decomposed in trend, seasonal and remainder components using stl procedure and the slope in the trend component was calculated using gls. stl decomposition of the monthly mean pm 2.5 along with gls fitted models for the five cities are shown in figure 4 . the equation shown in the figure depicts the gls linear regression slope with 95% ci and the same has been shown in table 1 . as can be seen from figure 4, all the cities show a significant decline (negative) trend ranging from 1.5 to 4.19 µg/m 3 per year. the highest decline trend of 4.19±1.12 µg/m 3 per year was found for new delhi whereas we have also checked whether the trend in the pm 2.5 is affected by trend in the meteorological parameters such as wind speed, pblh, and precipitation during the six years. these meteorological parameters are obtained from merra-2 reanalysis and have been validated (supplementary table 3 ) against the surface observations at the airports. the trend in the meteorological parameters has been calculated in the same way as it was done for pm 2.5 . the calculated trend in wind speed, temperature, pblh, and annual precipitation is shown in supplementary figure 5 . it is found that wind speed, temperature, pblh and precipitation do not exhibit a significant change during the study period. therefore, this analysis confirms that the reduction in pm 2.5 is not due the meteorology but due to the reduction in emissions. various pollution mitigation schemes along with the public awareness programs (ncap, moefcc, 2019), could have led to the reduction of pm 2.5 levels in delhi. j o u r n a l p r e -p r o o f air quality standards, guidelines, objectives, targets, and limit values are defined by the local authorities to control air pollution. the levels below the standard or limit value are (bran & srivastava, 2017) for the year 2008 found pm 2.5 mass concentration 2-3 times higher than indian naaqs and who standards. moreover, remote sensing based study by dey et al. (2012) has shown that 51% of the indian population is exposed to the levels that exceed the who annual air quality threshold of 35 μg/m 3 . the chemical composition of pm 2.5 offers vital information on the contributions of specific sources and help to understand aerosol properties and processes. pm 2.5 chemical components have been found to vary considerably among different sites across the globe (snider et al., 2016) . global population-weighted pm 2.5 concentrations were dominated by particulate organic mass, secondary, mineral dust as well as secondary inorganic aerosols such as sulfates, nitrates and ammonium (philip et al., 2014) . in addition to the observed trend of pm 2.5 , it is also important to know the variability and trend in the chemical composition. the relation between pm 2.5 exposure and associated health effects is linked with physical and chemical characteristics of the pm 2.5 , and therefore requires attention along with its sources for better management of urban air pollution (braziewicz et al., 2004; srimuruganandan and nagendra, 2011) . however, the unavailability of long-term chemical composition records restricts the detailed analysis of the possible sources. moreover, one can conduct modelling analysis of pm 2.5 composition but it is considerably challenging because of the combination of uncertainties in the magnitude and spatial and temporal allocation of primary pm 2.5 emissions and our limited understanding of the chemical production pathways for secondary constituents (mathur et al., 2008 , appel et al., 2008 were observed to be highest during winter followed by post monsoon>summer>monsoon (jain et al., 2020; kota et al., 2018, sharma and pant et al., 2015) , so 4 2− was reported to be most abundant during summer followed by monsoon>post monsoon>winter (jain et al., 2020; pant et al., 2015) . secondary no 3 − is thermally unstable at higher j o u r n a l p r e -p r o o f journal pre-proof temperatures whereas at low temperatures during winter its formation is favorable (cesari et al., 2018) . higher photochemical activities during the summer season and high humid conditions during monsoon favors the formation of secondary so 4 2− (jain et al., 2020; goel et al., 2018 , pant et al., 2015 . while na + is observed highest during monsoon owing to its sea origin (jain et al., 2017; saxena et al., 2017) , cl − is also significantly linked with wood combustion, open waste burning, coal combustion and industries (rai et al., 2020; ali et al., 2019; pant et al., 2015) , and therefore is observed highest during winter sharma and mandal, 2017; jain et al., 2017; sharma et al., 2016; ) along with the biomass burning marker ion k + (sudheer et al., 2014; tiwari et al., 2013a) . organic components of pm 2.5 like levoglucosan has been linked with biomass burning in winter (pant et al., 2015) . pahs, linked with biomass burning and road transport, showed the highest concentration during winter, followed by post monsoon> summer>monsoon (gadi et al., 2019; singh et al., 2011) . ec and oc which are emitted from vehicular emissions and biomass burning (ram and sarin, 2011; sharma et al., 2016) are reported to be higher during winter than summer (jain et al., 2017; sharma and mandal 2017; tiwari et al., 2014) . elemental contribution analysis showed the higher contribution of road dust and soil (marked with higher si value) during summer whereas for the winter season, the contribution of biomass burning was high (marked with higher k value) saxena et al., 2017; jain et al., 2020; pant et al., 2015) . for kolkata, roughly 50% of the pm 2.5 mass was reported to be constituted of ions (na + , k + , mg 2+ , ca 2+ , nh 4 + , so 4 2− , no 3 − , cl − ) and carbonaceous particles (ec, oc) (chatterjee et al., 2012) . higher concentrations of nh 4 + , so 4 2− , and no 3 − were observed during winter than summer, however, the so 4 2− oxidation ratio, which is an indicator of secondary so 4 2− formation, was found to be highest during summer months. kolkata showed the highest na + during monsoon, whereas higher cl − was observed during dry seasons (chatterjee et al., 2012) and were linked with biomass and coal burning. ec and oc for kolkata as well showed the highest levels during winter, followed by summer and lowest in monsoon (chatterjee et al., 2012; talukdar et al., 2015) . for mumbai, the major chemical constituents observed were ions (na + , k + , ca 2+ , nh 4 + , so 4 2− , no 3 − , cl − ) and carbonaceous particles (ec, oc) and some trace and heavy metals. while secondary ions (nh 4 + , so 4 2− , and no 3 − ), ec and oc were observed higher either during winter or post-monsoon season owing to inland contribution. non-sea salt sources were of anthropogenic origin (joseph et al., 2016) . elemental analysis showed a significant contribution of the sea during monsoon, and soil dust j o u r n a l p r e -p r o o f journal pre-proof during the summer season (police et al, 2018) . for hyderabad, the studied chemical constituents were ec and oc (ali et al., 2016) . while both ec and oc showed the highest winter concentration than during summer, followed by the monsoon, the concentration variation during winter to summer transition for the two carbonaceous fractions is quite different. ec showed a significant decrease during the transition of winter to summer, the same was not true for oc as secondary organic carbon formation and biomass burning added to the total oc levels during summer. elemental analysis showed the importance of sources like resuspended dust and vehicular emission for the city (gummeneni et al., 2011) . for chennai, the reported chemical constituents of pm 2.5 were ions (na + , k + , ca 2+ , mg 2+ nh 4 + , so 4 2− , no 2 − no 3 − , cl − , f − ) and some trace and heavy metals (jose et al., 2019; srimuruganandam and nagendra, 2011 showed higher concentration during monsoon, followed by summer>winter (srimuruganandam and nagendra, 2011) . marine aerosols showed a significant contribution for the coastal city (jose et al., 2019) . we also performed the five days backward trajectories analysis using the hybrid single particle lagrangian integrated trajectory (hysplit version 4) model (stein et al., 2015; draxler and rolph, 2003) major sources of primary pm 2.5 in india are emissions from the household, power sector, industries, transport, open burning (crop and waste) and dust (conibear et al., 2018; guo et al., 2017; venkataraman et al., 2018) . although the household emissions are dominant across india (apte and pant, 2019) , vehicular exhaust and dust resuspension (singh et al., 2020a) remain the dominant local source in indian cities (guttikunda et al., 2014 . other urban sources include construction dust, industrial exhaust, and domestic cooking and heating . most of the sources of pm 2.5 in urban areas are local, however nonlocal contribution can be significant guo et al., 2017) . for eg.in delhi, local sources contribute ~70% of total pm 2.5 , but the non-local sources contribute over 30% especially in winter (guo et al., 2017) . the emissions neighboring rural areas, contribute to the urban pollution in india ravindra et al., 2019a; 2019b) . rural households in india rely on kerosene for light in the absence of electricity, and on wood, j o u r n a l p r e -p r o o f journal pre-proof dung, and other solid fuels for cooking and heating. (chowdhury et al., 2019 , ravindra et al., 2019c . use of these fuels emit particles, gaseous pollutants, and volatile organic compounds, and therefore are a significant source of secondary particulate matter in both rural and urban areas (pervez et al., 2019; rooney et al., 2019) . in addition to household and traffic emissions, open waste burning is also a significant contributor to the total pm 2.5 in indian cities kumari et al., 2019) . the open waste burning is prevalent during winter and over the urban areas with low socioeconomic status (nagpure et al., 2015) . other sources that determine the urban pm 2.5 levels include industries, thermal power plant, brick production, and use of diesel generator sets, however, the influence of these sources is highly variable . future emissions scenario studies conducted over india predict an increase in pm 2.5 (venkataraman et al., 2018; pommier et al., 2017) , however studies (chowdhury et al., 2019; purohit et al., 2019; venkataraman et al., 2018; conibear et al., 2018; bhanarkar et al., 2018) have shown that significant reduction in pm 2.5 is achievable by implementation strict measures to reduce the pm 2.5 emissions. it has been shown by chowdhury et al., (2019) that a transition from bad fuel to clean fuel in the household has the potential to significantly reduce the pm 2.5 levels at the national level. however, at the urban or city level, where cleaner fuel is used, reduction in vehicular emissions (exhaust and non-exhaust) can bring down the pm 2.5 levels as observed during the covid lockdown in indian cities and significantly reduce the traffic exposure (singh et al., 2020b) . we propose that the reduction in pm 2.5 levels across the cities is due to the recent measures taken to reduce the ambient pollution levels in india. the major recent initiatives that might have helped in the reduction include the launch of the national air quality index (aqi) for public awareness, the formation of environment pollution (prevention and control) authority, implementation of a graded response action plan (grap) and comprehensive action plan lpg is lower than that of solid fuel (deepthi et al., 2019) , the implementation of pmuy across india would have reduced pm 2.5 levels mainly at the regional level (chowdhury et al., 2019) . however, people's attitudes towards fuel usage may lessen the expected reduction in emission linked with this switch to cleaner fuel usage as solid fuels are much cheaper and easily available (ravindra et al., 2019c) . although waste management is a major challenge (kumar et al., 2017) , a major step to improve the door-to-door waste collection and disposal as a part of swachh bharat mission (swachhbharatmission.gov.in; ghosh, 2016) in urban areas could have resulted in the improvement in air quality. for the reduction of traffic exhaust emissions, the emission standard of the fleet was improved to bs-iv from april 2017 and bs-vi was scheduled from april 2020. the old fleet scrappage program was launched, and electric vehicles are being promoted. apart from this, shifting to alternate cleaner fuels like cng, ethanol blending in petrol are some of the steps taken for the cleaner transport sector. moreover, the use of a modern public transport system was promoted in recent years to reduce traffic emissions. while these measures reduce the exhaust emissions, the maximum reduction is expected in road dust resuspension emission by regular road dust cleaning by mechanized vacuum dust cleaners (goyal et al., 2019; gulia et al., 2018) . other measures include dust control from the building and road construction activities. the stringent measures to limit the crop residue burning. this study reports a detailed analysis of the variabilities and trends in the pm 2.5 concentration measured at the us embassy and consulates in the five megacities (chennai, kolkata, analysis of merra-2 meteorological parameters suggests no significant change in the annual mean wind speed, temperature, pblh, and precipitation in the past six years. despite that, pm 2.5 has been found to exhibit a declining trend. we have also reported the number of threshold exceedances of daily mean pm 2.5 as per the who (25 µg/m 3 ) and indian naaqs (60 µg/m 3 ). in addition, the number of pollution episodes and length of each episode (levels above limit values continuously for three or more days) has been reported. we found that the pm 2.5 levels in the cities exceed who standards for more than 50% of days in a year with a few exceptional years in chennai. j o u r n a l p r e -p r o o f so far, we have not come across any study that has suggested a significant decline trend in air quality in indian cities despite the measures by the local authorities. this is the first study, to the best of our knowledge, that has reported statically significant decreasing trends of pm 2.5 in indian megacities. this decrease can be attributed to the recent policies and regulations (ncap, moefcc, 2019) implemented in delhi and other cities for the abatement of air pollution. the implementation of source sector-specific measures related to vehicular emissions, road dust re-suspension and other fugitive emissions, bio-mass/ municipal solid waste (msw) burning, industrial pollution, construction, and demolition activities, etc. were the major steps towards the mitigation of air pollution. the mitigation measures implemented until june 2018 were expected to deliver an overall decline of ambient pm 2.5 despite economic growth (purohit et al., 2019) . while a reduction in pm 2.5 is found in delhi, it continues to be the most polluted city among five megacities. with the annual rate of reduction observed here, it may take another two decades for the pollution levels to come within indian naaqs levels. therefore, stricter compliance of the ncap policies can further accelerate the reduction of the pollution levels to reduce the health impacts across all india. the results 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pm2. 5 concentration and the seasonality of tuberculosis for beijing and the authors are thankful to the national atmospheric research laboratory (narl) andministry of earth sciences (moes) for providing the necessary support. we acknowledge key: cord-306124-sn780ike authors: jakariya, md.; alam, md. sajadul; rahman, md. abir; ahmed, silvia; elahi, m. m. lutfe; khan, abu mohammad shabbir; saad, saman; tamim, h. m.; ishtiak, taoseef; sayem, sheikh mohammad; ali, mirza shawkat; akter, dilruba title: assessing climate-induced agricultural vulnerable coastal communities of bangladesh using machine learning techniques date: 2020-06-16 journal: sci total environ doi: 10.1016/j.scitotenv.2020.140255 sha: doc_id: 306124 cord_uid: sn780ike abstract the agricultural arena in the coastal regions of south-east asian countries is experiencing the mounting pressures of the adverse effects of climate change. controlling and predicting climatic factors are difficult and require expensive solutions. the study focuses on identifying issues other than climatic factors using the livelihood vulnerability index (lvi) to measure agricultural vulnerability. factors such as monthly savings of the farmers, income opportunities, damage to cultivable lands, and water availability had significant impacts on increasing community vulnerability with regards to agricultural practice. the study also identified the need for assessing vulnerability after certain intervals, specifically owing to the dynamic nature of the coastal region where the factors were found to vary among the different study areas. the development of a climate-resilient livelihood vulnerability assessment tool to detect the most significant factors to assess agricultural vulnerability was done using machine learning (ml) techniques. the ml techniques identified nine significant factors out of 21 based on the minimum level of standard deviation (0.03). a practical application of the outcome of the study was the development of a mobile application. custom rest apis (application programming interface) were developed on the backend to seamlessly sync the app to a server, thus ensuring the acquisition of future data without much effort and resources. the paper provides a methodology for a unique vulnerability assessment technique using a mobile application, which can be used for the planning and management of resources by different stakeholders in a sustainable way. the intergovernmental panel on climate change (ipcc) highlights that the vast low-lying coastal region of bangladesh is particularly vulnerable to risks from climate change (ipcc, 2014) . increase in temperatures, changing rainfall patterns, sea-level rise, and increase in frequency and intensity of extreme climatic events are negatively impacting agriculture, water resources, human health, and the ecosystem (wheeler and von braun, 2013) . climate change has already had major impacts on the lives and livelihoods of the people in the coastal areas of bangladesh (gob, 2018 (gob, , 2011 . the greater reliance of the people on the agricultural sector has made it more challenging today as a sustainable livelihood. agriculture will become even more susceptible in the future due to changes in climate variables (ipcc, 2007; islam et al., 2011) . one predominant impact of climate change will be fluctuations in crop yield due to frequent changes in climatic variables (mendelsohn & dinar, 2003) . moreover, extreme climatic events, soil salinity in coastal areas, and incidence of pests and diseases due to the increased temperature and humidity may result in additional adverse effects on the agriculture sector (rosenzweig et al., 2001) . despite technological development, climatic factors are still fundamental dominators of agricultural productivity. addressing the issues to find solutions to reduce agricultural vulnerability would require an integrated and comprehensive management plan with particular consideration for hazard vulnerability and the resilience of the coastal population to climate change (sajjad & chan, 2019) . the authors recognize that long-term measures will be required to address the climatic factors of vulnerability and, therefore, the paper suggests methods to find the second most significant factors that can be addressed more easily and can reduce agricultural vulnerability in the short run. an effort was made to find the crop yield vulnerability of the farmers of the three coastal districts of bangladesh by identifying the significant factors that have increased effects on the vulnerability score by machine learning models. this was done by first calculating the vulnerability livelihood index of agriculture for each of the study areas. vulnerability indicators help monitor and keep track of the changing vulnerability over time and space (shah et al., 2013) . the three components that characterize vulnerability include j o u r n a l p r e -p r o o f 3 to cope with vulnerabilities related to rice production that would be specific for each region and could be managed locally with the help of mobile applications. developing such technology-based solutions has become extremely important, especially considering the scarcity of global resources and, more importantly, the recent covid-19 pandemic, which has emphasized the need to address the issue further. bangladesh, as a country, with its unique geographical location, is prone to natural disasters and climatic effects. therefore, at a time of such disasters, be it geographical or in the health-sector when mobility needs to be limited, it becomes next to impossible to maintain proper resource management. the work in this paper thus presents a complete system for the coastal areas of bangladesh that work with data acquisition using mobile applications, data processing using machine learning techniques, and interpretation through web-based interfaces. in addition, the architecture that was designed for this system is quite generalized and can be adopted for work in other domains as well, with minimal modifications. three coastal districts of bangladesh, namely, patuakhali, kutubdia, and khulna were selected for this research study. the maps of the study area are shown in figure 1 . the vulnerability assessment method used in the study was based on the vulnerability assessment method of giz vulnerability sourcebook (fritzsche et al., 2014) , which is built upon the ipcc framework. it should be noted that the giz study only addressed specific methods of the vulnerability score calculation, but this study goes a step further and puts forth a practical application and usability of the score, giving policymakers a chance to apply the vulnerability information for functional purposes. moreover, while giz only identified the main components of vulnerability (e.g., exposure, sensitivity, and potential impacts), this research project identified the significant factors for all components of vulnerability, as shown in figure 2 through engaging in extensive discussions with local communities. (2), (3), and (4) below: (1) where, w = weight and n = total number of factors. the categories assigned for the vulnerability score is shown in table 1 . the regions were assigned into a category of low, medium, and high vulnerability based on the vulnerability score along with consultations with experts and local villagers (schiffman & kanuk, 2004 ). random sampling methods were used to select the study areas and study population (bernard, h.r. 2002) . a total of 930 households were selected to collect preliminary data in order to get a general overview of the study area. broadly, socio-economic, climatic, water and sanitation, and disaster management related issues were covered in the questionnaire. a separate set of 297 samples were chosen from the preliminary selection of households to assess agricultural production and related vulnerability issues. the average vulnerability index and the spatial distribution of the houses according to vulnerability were prepared using j o u r n a l p r e -p r o o f 5 of each respondent, stores the result in a database and sends the data to a web dashboard. the web dashboard summarizes results for all respondents and also provides individual level vulnerability scores. administrators can use information from this dashboard to determine how resources can be optimally allocated to provide personalized help to each vulnerable individual. the factors related to three different variables of vulnerability, e.g., exposure, sensitivity, and adaptive capacity, were identified through focus group discussions (fgd) with the local farmers in each village. climate change-related exposures are global issues, whereas sensitivity and adaptive capacity are location-specific and can be addressed with local interventions (wilbanks, 2003; hess, et al., 2008) . the results of the fgds are presented in the vulnerability weights reflect the perception of farmers regarding the factors related to vulnerability in the study areas. weights measured from the ranking exercise conducted with farmers are displayed in table 2 . across the coastal region of bangladesh, the climatic conditions were amongst the factors with the highest weights, which illustrate their importance to assess vulnerability levels. the climatic conditions include average rainfall, average humidity, and average temperature (weight = 0.3), which holds a weight of particular importance that could disrupt farming activities. during fgd sessions, farmers often mentioned price and market conditions as vital factors for sustaining livelihoods. the factors shown in table 2 are location-specific and were collected through focus group discussions with the local farmers. the parameters with the highest vulnerability weights belong to exposure: average rainfall community response variations about different vulnerability factors in the three districts are shown in figure 5 . among the parameters for sensitivity, the parameter with the highest weight in cox's bazar and patuakhali that affects agricultural productivity is rain availability (weight = 0.2287, weight = 0.2181 respectively), whereas, in khulna and patuakhali, the parameter that holds the highest weight in the vulnerability calculation is the percentage of damaged crops (weight = 0.2181). the factors of adaptive capacity help to overcome the exposure and sensitivity factors when measuring the vulnerability of a community or household. the factors that hold the highest weight in the vulnerability calculation for cox's bazar were education level and seasonal crop diseases (weight = 0.134). the adaptive capacity factor with the highest weight in khulna was also observed to be seasonal crop diseases (weight = 0 .1081). in patuakhali, the factor with the highest weight for adaptive capacity was the education level (weight = 0.1171). table 3 shows the state of crop yield vulnerability of the three coastal regions of bangladesh, which is reflected in the vulnerability scores of different villages in the study area. each village's vulnerability score was derived from analyzing the individual score of each household. every household's individual score was then examined and the cumulative score was achieved to obtain the vulnerability score. the maps in figure 6 of three coastal regions show geographical areas of vulnerability, which is the subject matter of the study. the spatial map shows the vulnerability level of the villagers according to the household survey. similar to hazard maps, the vulnerability maps in figure 6 highlight the zones where farmers and farming land are most vulnerable to a variety of factors, which include social, physical, and economic aspects of rice production, as discussed above. (bathrellos et al., 2011 (bathrellos et al., , 2013 (bathrellos et al., & 2017 ). the overall average vulnerability level was found to be relatively moderate in all three study areas. this shows an overall similar vulnerability situation in the coastal region of the country. however, slight variations in terms of vulnerability were seen in maheswaripur it is apparent from the study that the vulnerability in the crop yield sector varies according to regional and temporal variations of natural disasters in the coastal areas of bangladesh. it was observed that among the 297 farmers, about 46%, 34%, and 55% were vulnerable to the risk of humidity, temperature, and precipitation, respectively. all the significant factors for vulnerability assessment were filtered using two different methods of statistical analysis and machine learning methods. later, a comparative analysis of both the methods identified the best method to use for developing the mobile application. it was done with an understanding to develop a mobile application that was simple and convenient for the users in terms of handling fewer vulnerability factors for input. the following sections discuss both methods. the multivariate logistic regression model was performed to screen out the non-significant factors of sensitivity and adaptive capacity (tolles & meurer, 2016; brunner & giannini, 2011) . the goodness of fit of the model was high because the value of r 2 is 0.70 (draper & smith, 1998) . on the basis of the wald test, five variables for sensitivity and five variables for adaptive capacity showed significance (p-value < 0.01) out of a total of 19 variables, which were considered initially for the vulnerability score calculation (fahrmeir et al. 2013; j o u r n a l p r e -p r o o f ward & ahlquist, 2018) . the vulnerability score was measured by integrating the significant factors related to sensitivity and adaptive capacity without influencing the original score (table 4) . though the statistical analysis gave a primary list of important variables, the correlation of the vulnerability scores generated only using these variables with those generated using the full list of variables under the giz framework was not high (r 2 = 0.7). so, using machine learning, we opted to find a better approach that would generate vulnerability scores closer to the original ones with fewer variables. the distribution of individual vulnerabilities, calculated as per the giz method, is plotted in figure 7 . it can be seen that vulnerability follows a normal distribution and that there are no extreme vulnerability scores. it was assumed that the distribution is such because the agriculture-dependent coastal people are generally more or less vulnerable. of the 297 data points that were collected, three had null values for different factors, which might have been caused by erroneous data entries. since the number of erroneous data points was very small, they were simply dropped and the remaining 294 data points were considered for the ml models. moreover, in the dataset, there were only three distinct values for temperature, humidity, and precipitation. this occurred because each district was given a single value for each of these factors. as a result, there was minimal variance in the data for these factors and thus, was excluded from the ml models. finally, to check whether any factor had little influence in predicting vulnerability, a column with random floating-point values taken from the half-open interval [0, 1) was added, entitled "random". the intention was to make an importance ranking of the factors where any factor ranked below "random" could easily be disregarded. thus, in the end, 294 data points having 20 actual factors and one random factor were considered. randomly chosen, 80% of these data points were kept for training the models and the remaining 20% for testing the performance of the models. before training the models, to ensure that there were no factors with high correlation, the spearman's rank correlation coefficient between each pair of factors in the training set was calculated and no two factors with high correlation were found. later, the vulnerability scores obtained by using the giz formula were taken as ground truths and five different regressors j o u r n a l p r e -p r o o f 9 were tested to generate vulnerability scores as close as possible to the ones attainted using the giz method. the models and their respective performances are shown in table 6 . it can be seen that linear regression and bayesian ridge regression performed well in predicting vulnerability scores while random forest regression, xgb regression, and extremely randomized trees regression overfitted the training data. the hyperparameters for the random forest, xgb, and extremely randomized trees regression (breiman, 2001; chen and guestrin, 2016; geurts, et al., 2006) through bayesian optimization were attempted to be tuned but were not successful in reducing the variance of these models without reducing their predictive capacity on the test set. this might be attributed to the fact that, in this case, these models are too complex for the small dataset being used. linear regression and bayesian ridge regression, on the other hand, did not require any hyperparameter tuning. as these models were functioning well, they were finally selected to generate the importance ranking of different factors. in order to obtain the importance scores of different vulnerability factors, permutation importance was used, which works by measuring the r 2 score on the original set of factors for a model and then calculating the decrease in r 2 by randomly permutating the values of each of the factors one at a time (altmann et al., 2010) . in this way, the factors with a larger decrease in r 2 value are considered to be more important. figure 8 although linear regression and bayesian ridge regression did not produce the same rankings, it was noticed that the two ranking schemes were similar in putting the same factors in higher or lower positions. to get a unified ranking, the ranks produced by the two regression models were summed up and sorted, with the factors in ascending order according to their sum of ranks. later, the factors with smaller sums of ranks were considered more important than those with bigger sums of ranks. this unified ranking is shown in table 6 . the vulnerability factors with the lowest rank to the second-highest rank and so on were dropped one by one and trained new linear and bayesian ridge regression models with continuously reducing sets of factors. table 7 lists how the new models performed with the reduced sets of factors. it was noted that the factor "random" was already dropped from our dataset before training the new models because it was no longer necessary. it can be seen from table 7 that up to 11 factors can be dropped and the vulnerability scores that have under 0.03 standard deviation from the original vulnerability scores while retaining a pearson correlation coefficient of 0.93 can still be predicted. since temperature, humidity, and precipitation were not included in the ml model like the original vulnerability calculation, it can be stated that, in actuality, up to 14 factors can be reduced and reasonable predictive capacity of vulnerability scores can still be maintained by asking only 9 questions. the ml method demonstrated successfully in identifying significant factors for vulnerability score calculation than that of the statistical approach. the ml method also demonstrated that it could strategically identify the significant vulnerability factors with the highest rank for designing program intervention without considering all significant factors to reduce a specific community vulnerability in a resource constraint situation. a mobile application was developed after a successful reduction of non-significant factors, which later was used to assess the vulnerability scores. the design of the user interface (ui) and user experience (ux) were heavily considered while developing the mobile application so that people of any age with little educational background can use it. farmers can log into this mobile application and answer the questions corresponding to the top 9 vulnerability factors, which were discussed in the previous section. to avoid any false input data, unrealistically large integer numbers of any input field can be filtered. later, the responses of each individual will be sent to the central virtual server and vulnerability scores will be calculated for each individual household using the bayesian ridge regression model. to reduce agricultural vulnerability, it is important to consider the factors identified as being significant, such as soil and existence of groundwater, crop diseases, etc. along with the physical process of the area which provided issues related to agricultural vulnerability and this ultimately would help planners and policymakers to develop sustainable agricultural planning for the coastal communities of bangladesh (bathrellos et al., 2013) . vulnerability assessment and planning are highly inter-dependent. in order to become more accurate in assessing farmers' vulnerability, it is important to consider environmental, social, economic, and other relevant factors such as culture, ethical issues, the proper understanding of the static relationships between man and nature, etc. while designing such an intervention (ford et al., 2018 , bathrellos et al., 2017 . a proper method of data collection, journal pre-proof j o u r n a l p r e -p r o o f such as, if possible, an anthropogenic approach, could be applied for collecting such important information from the villagers. if the significant factors for vulnerability are identified properly, it would be easier for policymakers and planners to allocate scarce resources in a sustainable way. the mobile application, for example, provided a dynamic vulnerability score. the score, in reality, is not static and changes continuously. the application also allows scores to be upgraded as frequently as required by relevant stakeholders to address a particular situation. as the application will be available to farmers for data input, the collected information will be more accurate while keeping expenses low as there will be no physical involvement for data collection and storage activities. the method of a mobile application-based quick vulnerability assessment technique can also be applied to assess other livelihood aspects simply by identifying significant factors responsible for vulnerability as the factors responsible for vulnerability are highly location and subjectspecific. agricultural production in the coastal regions of bangladesh is highly vulnerable to changes in weather conditions. the prevailing situation demands the development of a dynamic agricultural plan that considers the future consequences of climatic change and vulnerability to natural hazards. the study identified the most vulnerable agriculture-dependent households using a rapid and cost-effective method. the study focused on the development of a practical and community-friendly application to assess the vulnerability scores to aid local government institutions and other similar organizations with planning and management. spatial maps were also prepared to show the locations of vulnerable households along with the extent to which they were vulnerable (tambe et al., 2011) . the study also provided a description for the application of the vulnerability scores, which can later be used to understand the vulnerability issues of certain livelihood options, such as agriculture, fishermen, health, etc. climate change-related exposures are global issues, whereas sensitivity and adaptive capacity are local issues and can be addressed with local interventions (wilbanks, 2003; hess, et al., 2008) . community response to the identified vulnerability factors of sensitivity and adaptive capacity varied significantly due to the diverse developmental profile and geographical characteristics of the study areas. statistical and machine learning methods were initially used to filter the most significant factors. the ml method was more successful in this aspect and was used to develop a mobile application that helped in vulnerability assessment by figuring out the factors which require immediate government intervention. the climate resilient vulnerability assessment tool, which provides an authentic and faster process of identifying vulnerability, would be able to bring about a revolutionary change in resource distribution and, more importantly, the allocation of scarce resources in a sustainable way. the vulnerability assessment process is usually highly technical, whereas the mobile application, which is based on a built-in system, provides a more user-friendly approach and can be used independently. the research findings provided an important starting point for directing future research into crop yield vulnerability to climate variability and change. it is expected that the output of the study can be used by policymakers and other stakeholders for better designing and targeting climate change adaptation policies and programs to ensure sustainability. permutation importance: a corrected feature importance measure potential suitability for urban planning and industry development by using natural hazard maps and geological -geomorphological parameters assessment of rural community and agricultural development using geomorphological -geological factors and gis in the trikala prefecture suitability estimation for urban development using multi-hazard assessment map random forest trial design, measurement, and analysis of clinical investigations study on livelihood systems assessment, vulnerable groups profiling, and livelihood adaptation to climate hazard and long-term climate change in drought prone areas of north-west bangladesh. centre for environmental geographic information services (cegis) and food and agricultural organization of the united nations (fao) proceedings of the 22nd acm sigkdd international conference on knowledge discovery and data mining -kdd '16 applied regression analysis the dynamics of vulnerability: locating coping strategies in kenya and tanzania regression: models, methods, and applications vulnerability and its discontents: the past, present, and future of climate change vulnerability research the vulnerability sourcebook: concept and guidelines for standardised vulnerability assessments. bonn and eschborn: deutsche gesellschaft fã¼r internationale zusammenarbeit (giz) gmbh extremely randomized trees climate change climate change climate variations: farming systems and livelihoods in the high barind tract and coastal areas of bangladesh total vulnerability of the littoral zone to climate change-driven natural hazards in north brittany climate, water, and agriculture climate change and extreme weather events: implications for food production, plant diseases, and pests. global change and human health risk assessment for the sustainability of coastal communities: a preliminary study consumer behavior this research was supported and funded by the climate change trust fund (cctf), the government of the people's republic of bangladesh and the department of environment (doe). the authors declare that there is no conflict of interest..016journal pre-proof j o u r n a l p r e -p r o o f key: cord-317042-dll3qt4g authors: lv, jun; yang, jin; xue, juan; zhu, ping; liu, lanfang; li, shan title: detection of sars-cov-2 rna residue on object surfaces in nucleic acid testing laboratory using droplet digital pcr date: 2020-06-19 journal: sci total environ doi: 10.1016/j.scitotenv.2020.140370 sha: doc_id: 317042 cord_uid: dll3qt4g abstract the rapid development of global covid-19 pandemic poses an unprecedented challenge to the safety and quality of laboratory diagnostic testing. little is known about the laboratory surface areas and operation behaviors that may cause potential contamination in sars-cov-2 nucleic acid testing. this study aims to provide reference basis for the improvement of laboratory disinfection programs and personal operating protocols. in this study, we compared the qrt-pcr and ddpcr in detecting of residual virus that existed on the object surfaces from sample transportation and reception related facilities, testing related instruments, personal protective equipment and other facilities in nucleic acid testing laboratory. all samples were negative by qrt-pcr, in contrast, 13 of 61 samples were positive for sars-cov-2 by ddpcr. the areas with highest density of sars-cov-2 nucleic acid were the outer gloves of operator a (37.4 copies/cm2), followed by door handle of 4 °c refrigerator (26.25 copies/cm2), goggles of operator a (22.16 copies/cm2), outer cover of high speed centrifuge (19.95 copies/cm2), inner wall of high speed centrifuge (14.70 copies/cm2) and others. we found that all the positive objects were directly or indirectly contacted by the operator's gloved hands, suggesting that hands contact was the main transmission pathway that led to laboratory environmental contamination. in summary, ddpcr has an advantage over qrt-pcr in tracing laboratory contamination. we evaluated the risk areas and operation behaviors that may easily cause contamination, and provided recommendation for improving the laboratory disinfection programs and personal operating specifications. covid-19 is highly infectious and causes relatively high mortality especially among the elderly and people with underlying conditions (boccia et al., 2020; david m. studdert, 2020; liu et al., 2020a; wayne c. koff, 2020) . according to the world health organization, as of june 16, 2020, the covid-19 pandemic has spread to 216 countries areas or territories, and resulted in 7,941,791 confirmed cases with 434,796 deaths. sars-cov-2 as the causative pathogen of the covid-19 outbreak was first sequenced and identified by chinese scientists in early january, 2020 (huaiyu tian, 2020; ictv, 2020; li et al., 2020) . nucleic acid detection of sars-cov-2 is the main method for confirming cases of covid-19. the detection work needs to be carried out in the negative pressure bsl-2, and operators should wear proper personal protective equipment (ong et al., 2020) . the sars-cov-2 is transmitted mainly through human respiratory droplets and contact. due to the lack or improper use of personal protective equipment, in many countries including china, a large number of healthcare workers on the front line have been infected with sars-cov-2 (megan l. ranney, 2020; yu et al., 2020) . effective disinfection of the environment for nucleic acid testing laboratory and good operation habits are essential to ensure the detection quality and personal safety. the operator needs to understand the possible contamination areas of a nucleic acid testing laboratory to take appropriate disinfection measures. however, until now, little is known about the laboratory surface areas and operation behaviors that may cause potential contamination in sars-cov-2 nucleic acid testing. in this study, we aimed to 1) determine the concentration of sars-cov-2 present on the object surfaces and personal protective equipment after the nucleic acid test, 2) identify the risk areas and operation behaviors that may cause contamination, and 3) provide reference basis for the targeted formulation of laboratory disinfection programs and personal operating specifications. taihe hospital is a grade a class three general hospital in shiyan city, hubei province, china. the testing team carried out nucleic acid detection of sars-cov-2 since january 23, 2020. screening of suspected covid-19 cases was mainly in february and no new cases were confirmed since march 1 (fig. 1) . in february, the average daily sample size and positive rate were 86 and 10.57%, respectively. the sampling of nucleic acid testing laboratory environment was conducted on february 12, 2020, on which day the sample size and positive rate was close to the average (fig. 2 ). after the sars-cov-2 nucleic acid test for clinical case samples, four types of j o u r n a l p r e -p r o o f samples from the nucleic acid testing laboratory, including sample transportation and reception related facilities, testing related instruments, personal protective equipment, and other facilities, were collected. a total of 61 samples were shown in table 1 . if the surface area of an object exceeded 100 cm 2 , the sampling area of the object surface was limited to 100 cm 2 , otherwise the entire surface was sampled. a 5cm×5cm standard specification board was placed on the surface of the object, then a sterile cotton swab soaked with viral transport medium (yocon, cat: mt0301) was used to wipe the specification plate for 5 times. after four specification board areas were sampled continuously, the cotton swab was cut off from the hand contact part and put into a test tube containing 3.5 ml of viral transport medium. for small objects such as door handles, faucets, and pipettes, a sterile cotton swab soaked with viral transport medium was used to wipe the entire surface, and the surface areas were estimated. qrt-pcr and ddpcr were applied to detect sars-cov-2 simultaneously. after collection, all samples were processed immediately in the bsl-2 of taihe hospital. the sample tubes were gently shaken for 1 min to elute the virus into preservation solution. rna was extracted from the elution using the viral nucleic acid isolation kit (bioperfectus, cat: sdk60102) according to the manufacturer's instruction. j o u r n a l p r e -p r o o f qrt-pcr was carried out using the novel coronavirus(2019-ncov) nucleic acid diagnostic kit (sansure biotech, cat: 20203400064 ) for amplifying specific genes (orf1ab and n). the amplification reaction has a total volume of 25 μl containing 10 μl rna template. the reaction conditions were: 50 °c 30 min for reverse transcription, then 95 °c 1 min for pre-denaturation, followed by 45 cycles of 95 °c 15 s for denaturation and 60 °c 30 s for annealing, extension and fluorescent signals collection. cycle threshold (c t ) ≤ 40 was interpreted as positive, and c t > 40 as negative. the primers specific for the orf1ab and n gene targeting the sars-cov-2 were adopted from chinese center for disease control and prevention (cdc). the ddpcr was performed on the bio-rad qx200 system with manufacturer's instructions. the reaction mixtures (20 μl) contained 5 μl of 2x one-step rt-ddpcr advanced kit for probes (bio-rad, 1864021), 2 μl of reverse transcriptase, 1 μl of 300 mm dtt, 900 nm of target primers, 250 nm of probe, and 10 μl of extracted rna. for the detection and quantitative enumeration of sars-cov-2, the mixture was transferred into the dg8 cartridge with 70 μl of droplet generation oil for probes (bio-rad, 1863005) to generate droplets. it took about 2 min to generate a set of eight processed samples by the using qx200tm droplet generator. then the pcr reaction was performed using the following cycling protocol: 42-50 °c 60 min for reverse j o u r n a l p r e -p r o o f transcription, 95 °c 10 min for enzyme activation, 40 cycles of 95 °c 30 s for denaturation, 60 °c 1 min for annealing and extension, and 98 °c 10 min for enzyme deactivation. the fluorescence was acquired by qx200tm droplet reader after amplification and the output data were analyzed using quanta soft tm analysis software. the detection threshold and positive samples were determined by the negative and positive control. the sars-cov-2 test results of object surface samples from nucleic acid detection laboratory were shown in table 1 . test results for all samples (n=61) were negative by qrt-pcr. in contrast, 13 out of 61 samples were positive by ddpcr. the highest concentration of sars-cov-2 rna molecules was from outer gloves of operator a (37.4 copies/cm 2 ), followed by the door handle of 4 °c refrigerator (26.25 copies/cm 2 ), goggles of operator a (22.16 copies/cm 2 ), outer cover of high speed centrifuge (19.95 copies/cm 2 ), inner wall of high speed centrifuge (14.7 copies/cm 2 ), protective mask of operator a (5.25 copies/cm 2 ), inner wall of sample transport box c (2.63 copies/cm 2 ), outer gloves of operator b (1.58 copies/cm 2 ), 200 μl pipette (1.16 copies/cm 2 ), 1 ml pipette (0.88 copies/cm 2 ), 10 μl pipette (0.5 copies/cm 2 ), door handle of biological safety cabinet (0.84 copies/cm 2 ) and handle of sample transport box a (0.86 copies/cm 2 ) ( table 1 ). all the positive objects were directly or indirectly contacted by the operator's gloved hands. the results of ddpcr detection for sars-cov-2 by sample type are shown in fig. 3 . while the overall positive rate was 21.31%, personal protective equipment had the highest positive rate of 28.57%. lower rates were found in testing related instruments (28%) and sample transportation and reception related facilities (12.5%). all six samples belonging to other facilities were negative for sars-cov-2 by ddpcr. how to ensure the safety of medical staff as much as possible is one of the key factors for the prevention and control of covid-19. nucleic acid detection of sars-cov-2 currently is the most accurate and direct method for the diagnosis of covid-19 and has been widely used by most countries in the world (corman et al., 2020; yan et al., 2020) . in addition to ensuring adequate access to personal protective equipment, thorough disinfection of the bsl-2 and proper use of personal protective equipment are very important to protect operators from infection . in this study, all objects in nucleic acid detection laboratory that tested positive for sars-cov-2 were directly or indirectly contacted by the operator's gloved hands. the outer gloves of operator also showed the highest viral rna concentration. these results supported the notion that hand contact transmission was the main way of laboratory environmental contamination. the second highest concentration of sars-cov-2 was found on the door handle of 4 °c refrigerator, while the door handle of -20 °c refrigerator was negative. the upper part of the refrigerator was 4 °c for storing samples temporarily, and the lower part j o u r n a l p r e -p r o o f was -20 °c for storing reagents. after an initial test, clinical samples were usually packaged and temporarily stored in a refrigerator at 4 °c for several hours to wait for the decision to test again or destroy. the concave of refrigerator door handle has a shadow area that couldn't be irradiated by ultraviolet rays, and the sars-cov-2 might be concentrated there. in order to solve this problem, the operators were recommended to wipe the refrigerator door handle with disinfectant to kill the virus after each detection immediately. the high-speed centrifuge was another instrument that was easily contaminated. in this research, both the outer cover and the inner wall were contaminated with sars-cov-2. after detection, the outer cover of the centrifuge was often closed by operators, and disinfected through disinfectant wipe and ultraviolet radiation. however, the inner wall of the centrifuge was usually ignored. it was suggested that the inner wall should be disinfected in the same way to eliminate the virus. pipettes of various ranges were the most frequently used instruments in nucleic acid detection of sars-cov-2. therefore, it was not surprising to detect sars-cov-2 from the pipette surfaces. from high to low, the virus concentration on the surfaces was 200 μl pipette, 1 ml pipette, and 10 μl pipette, and this order was consistent with the order of the pipette use during nucleic acid extraction. nucleic acid detection for sars-cov-2 usually requires two laboratory technicians to operate together. they examine each other's personal protective equipment, check sample information, and cooperate with each other during operations. different operating habits will cause different levels of contamination in personal protective journal pre-proof j o u r n a l p r e -p r o o f equipment. in this study, the protective mask, goggles and outer gloves of operator a were positive for sars-cov-2, while for operator b, sars-cov-2 could only be detected from the outer gloves. our subsequent investigation indicated operator a 's mask and goggles were not worn properly, causing goggles to become fogged which affected the sight. therefore, operator a had to adjust the mask and goggles repeatedly with gloved hands during operation. as a result, the mask and goggles of operator a were contaminated by sars-cov-2 from the outer gloves. this indicated that it is very important to wear personal protective equipment correctly before entering into bsl-2. during the operation, one should avoid using gloved hands to touch one's own masks, goggles, and other personal protective equipment. in this study, we analyzed the qrt-pcr results of clinical samples and found that the average ct value of human endogenous reference gene and viral target gene were 21.78 and 31.84, respectively. for object surface detection, 46 out of 61 samples tested positive for human endogenous reference gene by qrt-pcr, with the average ct value being 38.36, which nearly approached the threshold (40) of the kit. it indicated that the amount of contaminated samples on the surface of the object was extremely small. moreover, positive rate of clinical samples and the proportion between human endogenous reference gene and viral target gene would make it almost impossible to detect viral gene by qrt-pcr, which was supported by the results of this study with all samples testing negative for sars-cov-2. in contrast, j o u r n a l p r e -p r o o f 21.31% of samples were positive for sars-cov-2 with ddpcr, which suggested that ddpcr was more sensitive (hindson et al., 2013; liu et al., 2020b) and has broad application prospects in detecting extremely small amounts of samples. the culture of sars-cov-2 is required to be conducted in a bsl-3 according to the biosafety requirements. there was only bsl-2 facility in this hospital, a situation likely to be true in most inpatient hospitals globally, which precluded the determination of whether the detected sars-cov-2 was still alive. nevertheless, the test results could still show the high-risk areas contaminated by sars-cov-2 in nucleic acid detection operation, which indicate that all the operators need to develop good operating habits and thoroughly disinfect the laboratory without blind areas after the experiment. fortunately, during the entire covid-19 outbreak, all the operators of nucleic acid testing in this hospital benefited from good laboratory conditions and proper use of personal protective equipment and no laboratory-acquired infections were found. the authors declare that they have no competing interests. what other countries can learn from italy during the covid-19 pandemic mental health care for medical staff in china during the covid-19 outbreak detection of 2019 novel coronavirus (2019-ncov) by real-time rt-pcr civil liberties, and mass testing -calibrating restrictions during the covid-19 absolute quantification by droplet digital pcr versus analog real-time pcr an investigation of transmission control measures during the first 50 days of the covid-19 epidemic in china the species severe acute respiratory syndrome-related coronavirus: classifying journal pre-proof and naming it sars-cov-2 early transmission dynamics in wuhan, china, of novel coronavirus-infected pneumonia the reproductive number of covid-19 is higher compared to sars coronavirus aerodynamic analysis of sars-cov-2 in two wuhan hospitals critical supply shortages -the need for ventilators and personal protective equipment during the covid-19 pandemic surface environmental, and personal protective equipment contamination by severe acute respiratory syndrome coronavirus 2 (sars-cov-2) from a symptomatic patient covid-19 and immunity in aging populations -a new research agenda key: cord-299889-x6c3p195 authors: tirkolaee, erfan babaee; abbasian, parvin; weber, gerhard-wilhelm title: sustainable fuzzy multi-trip location-routing problem for the epidemic outbreak of the novel coronavirus (covid-19) date: 2020-11-10 journal: sci total environ doi: 10.1016/j.scitotenv.2020.143607 sha: doc_id: 299889 cord_uid: x6c3p195 the performance of waste management system has been recently interrupted and encountered a very serious situation due to the epidemic outbreak of the novel coronavirus (covid-19). to this end, the handling of infectious medical waste has been particularly more vital than ever. therefore, in this study, a novel mixed-integer linear programming (milp) model is developed to formulate the sustainable multi-trip location-routing problem with time windows (mtlrp-tw) for medical waste management in the covid-19 pandemic. the objectives are to concurrently minimize the total traveling time, total violation from time windows/service priorities and total infection/environmental risk imposed on the population around disposal sites. here, the time windows play a key role to define the priority of services for hospitals with a different range of risks. to deal with the uncertainty, a fuzzy chance-constrained programming approach is applied to the proposed model. a real case study is investigated in sari city of iran to test the performance and applicability of the proposed model. accordingly, the optimal planning of vehicles is determined to be implemented by the municipality, which takes 19.733 hours to complete the processes of collection, transportation and disposal. finally, several sensitivity analyses are performed to examine the behavior of the objective functions against the changes of controllable parameters and evaluate optimal policies and suggest useful managerial insights under different conditions. the most recent epidemic outbreak that caused a pandemic and public health emergencies is the spread of the novel coronavirus disease , threatening the health of the world population (kargar et al., 2020) . the covid-19 has quickly spread from wuhan to other regions and influenced more than 200 countries throughout the world by the end of march, 2020 (ahmadi et al., 2020 govindan et al., 2020) . it is now a pandemic due to the rapid rise in the number of infected people and the lack of initial attention to the covid-19 pandemic from world's leaders (mardani et al., 2020) . so, we have encountered a critical and challenging period for the control and prevention of the pandemic. one of the serious concerns about the outbreak of covid-19 is the incubation period, which fluctuates from 3 to 14 days (issa and elaziz, 2020) . it is obvious that the spread of covid-19 may be increased through an inefficient waste management system (sarkis et al. 2020 ). in line with the significance of providing medical items, another substantial issue is handling the infectious medical waste related to covid-19 generated in diagnosing and treating patients at health centers including hospitals and infirmaries. with the growing rate of confirmed cases, the amount of medical waste related to covid-19 increases significantly, which is now considered as critical hazardous materials (hazmat). in other words, medical waste disposal is regarded as a significant way to handle the source of infection, strict establishment and standardization of the waste management of covid-19 (peng et al. 2020 ). hospitals and infirmaries), transportation (through the road network) and disposal of the covid-19 related waste at pre-established disposal sites. the main idea is to provide a decision support system (dss) ensuring that covid-19 related medical waste is timely, regularly, harmlessly and effectively is disposed by considering sustainable development. to this end, the sustainable multi-trip location-routing problem with time windows (mtlrp-tw) is introduced to address the collection, transportation and disposal processes considering the priorities of services and available budget of the system. here to address the sustainable development, the objectives are defined to concurrently minimize the total traveling time of waste-collection vehicles, total violation from time windows (service priorities) and the number of people live around disposal sites. accordingly, a novel momilp model is developed to formulate the problem and then to be validated using a real-life case study problem. the location-routing problem (lrp) is an extension of the classic routing problem that integrates the strategic and operational decisions by facility location problem (flp) and vehicle routing problem (vrp), respectively. each of these problems has been frequently investigated in the literature as can be seen in erkut et al. (2008) and tirkolaee et al. (2018 tirkolaee et al. ( , 2019 tirkolaee et al. ( , 2020a . due to the high application of lrp in supply chain and waste management systems, it has been studied by many researchers in different cases (drexl and schneider, 2015) . to be more specific, zografros and samara (1989) , as one of the pioneering research, suggested an lrp model for transportation and disposal of hazmat considering three minimization-type objectives of routing risk, disposal risk and travel time. they applied a goal programming (gp) approach to solve the model. (2007) das et al. (2012) designed a multi-objective framework for routing of hazmat between generating nodes and disposal sites with the aim of total transportation cost and risk minimization. they conducted a real case study using posteriori technique with multi-objective programming approach to provide non-dominated solutions for the waste management system. a multi-objective mixed-integer linear programming model (momilp) was designed by samanlioglu (2013) to address the industrial hazmat lrp. the objectives were to minimize total cost, total transportation risk and total risk for the population around treatment facilities. they investigated a real case study in turkey using lexicographic weighted tchebycheff formulation and cplex software. zhao and ke (2017) analyzed the incorporation of inventory risks in lrp for explosive waste management. they developed a bi-objective model to concurrently minimize total cost and total risk. they investigated some numerical experiments using real-world data in china. aydemir-karadag (2018) offered a profit-oriented model for hazmat lrp considering energy recovery and the application of polluter pays principle. she tested the applicability of the proposed model using hypothetical problem instances based on a real-life case study. two meta-heuristic algorithms were proposed by rabbani et al. (2018) to tackle an industrial hazmat lrp considering incompatible waste types. the objectives were to simultaneously minimize total cost, total site risk for people and total transportation risk. beneventti et al. to the best of our knowledge, there is no study yet dealing with the efficient treatment of covid-19 related medical waste at the operational level; i.e., in terms of timely collection, j o u r n a l p r e -p r o o f transportation and disposal within a waste management system. moreover, this is the first study that introduces the mtlrp-tw under uncertain conditions. therefore, due to the instability and uncertainty of the demand parameter, fuzzy chance-constrained programming approach is applied. furthermore, a weighted goal programming (wgp) technique is then implemented to deal with the multi-objectiveness of the model. this section describes the suggested methodology of the study to establish an efficient waste management system during the covid-19 pandemic. to have an overall view, figure 1 represents the execution steps. consider a network including parking site, demand nodes (hospitals and infirmaries) and preestablished and post-established disposal sites. the aim is to make locational and routing decisions under a specific situation imposed by the covid-19 pandemic. accordingly, at the first stage, the required additional disposal sites are established at the beginning of the time horizon, which are called post-established disposal sites. vehicles routing plan is made at the second stage such that a fleet of vehicles is considered to start their first trip from the parking and end it at one of the available disposal sites. furthermore, the next possible trips of these vehicles start from that disposal site and end at available disposal sites. it means that the destination and departure can be different, so the concept of "intermediate depots" is associated. for more information, see tirkolaee et al. (2020b) . according to this pandemic situation, it is necessary that the waste should be instantly collected, transported and disposed. each demand node has its own service time window that should be served. so, the objective functions are to simultaneously (i) minimize the total traveling time, (ii) minimize total violation from time windows and (iii) minimize total infection/environmental risk imposed on the population around disposal sites. iii. each vehicle has a maximum service time. iv. demand parameters are considered as triangular fuzzy numbers. v. there are both pre-and post-established disposal sites that have limited capacity. vi. candidate disposal site can be established just at the beginning of the planning periods. vii. each demand node should be served only by one vehicle. viii. from second trips onwards, vehicles may unload the collected waste in a different disposal site from which the trip has been already started. now, the mathematical notations of the proposed model including sets and indices, parameters and variables are listed as follows. set of nodes ( ); ; here, 1 represents the parking, (1) j o u r n a l p r e -p r o o f (10) , objective function (1) minimizes the total traveling time of vehicles. objective function (2) minimizes the total violation from time windows defined by demand nodes. objective function (3) minimizes the disposal sites risk; i.e., the number of people around disposal sites is minimized. constraint (4) represents the flow balance equation for each node. constraint (5) guarantees that each demand node should be served in each period. constraint (6) indicates the capacity limitation of each vehicle in each trip. constraints (7) and (8) (19) and (20) guarantee that vehicles should start the first trip from parking and end it at a disposal site, respectively. constraints (21) and (22) ensure that vehicles start the potential next trips from the disposal site (as the final node of its j o u r n a l p r e -p r o o f journal pre-proof first trip) and end it at a disposal site, respectively. constraints (23) and (24) guarantee that vehicles should move back to the parking in their last trip to complete their tour in each period. constraint (25) indicates the budget limitation of the waste management system. constraint (26) expresses that vehicles can construct a route only when they are already assigned. constraints (27) and (28) show the types of the variables. to deal with the uncertain nature of parameters and to develop a more realistic model, fuzzy mathematical programming is applied as an efficient approach (tirkolaee et al., 2020c) . here, constraints. the triangular fuzzy numbers have the appropriate applicability to cope with data which suffer from accuracy or information (li et al., 2012) . if ̃ is taken into account as a triangular fuzzy number and the confidence level (ρ) is greater than 0.5, considering the confidence level of the fuzzy number versus the random number r, we have: eqs. (35) and (36) in the proposed model, demand parameter ̃ is the uncertain parameter of the model as an independent triangular fuzzy number. now, the constraints that include this parameter are rewritten based on the fuzzy chance-constrained programming model. therefore, eqs. (6) and (7) are reformulated based on the chance-constrained planning approach. now, based on eqs. (35) and (36), eqs. (37) and (38) are defuzzified. it is noticeable that eq. (38) should be regarded as two inequalities: one of the most attractive multi-objective programming approaches is gp that was introduced by charnes and cooper (1977) . this method addresses optimization problems with multiple conflicting objectives. the main advantage of gp over other multi-objective programming techniques is the concurrent consideration of different objectives, and also permissibility of deviation from ideal objectives (goals) which makes the decision-making process flexible. on the other hand, since we usually encounter multiple objectives with multiple units and importance degrees, it is required to normalize the objective function of gp and assign weights to the objectives to tackle the importance levels. accordingly, wgp is proposed with the following mathematical structure: this section investigates the validation of the proposed model using a real case study problem in sari, the capital of mazandaran province, iran. according to figure 3 , 1 pre-established disposal site (node number 1) and 3 candidate locations (nodes numbers 2, 3 and 4) are given in the map. it should be noted that the candidate locations are adapted from the study conducted by lahmian (2018). he evaluated the potential locations to establish disposal sites considering the criteria of i. geology, ii. land use, iii. slope, iv. vegetation, v. access roads, and vi. distance from towns of sari city. finally, the land use and distance from towns of sari city were determined as the main effective criteria. moreover, based on figure 4 , 16 hospitals and infirmaries are distributed within the city networks which generate covid-19 related medical waste. moreover, 4 vehicles are available at the parking site. the confidence levels of eqs. (6) and (7); i.e., and are set to 0.7. the maximum available time for vehicles and available budget are set to 480 minutes and 1 million usd, respectively. furthermore, = 0.8 and = 1.2 . sciences (2020). to obtain the values of the triple goals, the single-objective model is separately solved by each objective function. the proposed model is implemented using cplex solver/gams software. table 1 represents these values. now, the proposed milp model in section is implemented to attain the optimal policy for the case study problem and evaluate its performance and complexity. vehicles. moreover, the total violation time is equal to 2.982 hrs within a working weak and total infection risk size is 13214 people. since the pre-established disposal site is also used for household waste, the 4 th candidate location is established. table 3 represents the optimal routing plans of vehicles in the first time period. now, to investigate the effects of key parameters on the objective functions, a sensitivity analysis is performed on the confidence levels ( , ) and budget level of the waste management system (ϒ). the obtained results are given in tables 4 and 5 and figures 5 and 6 . as can be seen in figure 5 , the objective functions reflect a direct behavior against the increase of the confidence levels. in other words, the objective functions grow with a different range of fluctuations in various change intervals. it means that reaching high confidence levels needs more resources and management should analyze and consider these behaviors to prevent any potential failures in the system. on the other hand, according to figure 6 , the objective functions show an indirect behavior against the increase of budget level. as an interesting point, the problem becomes infeasible j o u r n a l p r e -p r o o f for the 20% decrease in the budget level and the waste management system cannot provide a solution. so, it is indispensable that management considers the amount of available budget as an effective and critical parameter, and provides the required level under different real-world conditions, particularly for the covid-19 pandemic. the covid-19 pandemic is still far from the over, and it is not certain that the future trends would confront any region of the world. getting closer to the peak of the pandemic, waste management has not been receiving the priority which is required to minimize the detrimental impacts on the health and environment. the collected information from mazandaran university of medical science and sari municipality demonstrates a variable trend on the decreasing or increasing in covid-19 related medical waste amount. designing and establishing an efficient dss for controlling this problem can help the sari city and provide a useful example for other cities and countries so that they can handle the spread of the disease using the same dss. hence, this study tried to efficiently collect, transport and dispose the covid-19 related medical waste by modeling the problem as an mtlrp-tw. the following main conclusions are yielded according to the numerical results of this study: (1) a novel momilp formulation was proposed for the mtlrp-tw considering real-life assumptions for the waste management application, such as multiple planning periods and separate locations for the disposal sites and parking, (2) fuzzy chance-constrained programming was utilized to study the significant uncertainty of demand parameter that denotes the amount of covid-19 related medical waste generated at hospitals and infirmaries, parking-3-5-10-9-ds1 ds1-1-11-2-4-6-ds4 j o u r n a l p r e -p r o o f a profit-oriented mathematical model for hazardous waste locating-routing problem a multi-product maximin hazmat routing-location problem with multiple origin-destination pairs goal programming and multiple objective optimizations: part 1 pareto frontier analyses based decision making tool for transportation of hazardous waste a survey of variants and extensions of the locationrouting problem a multicriteria facility location model for municipal solid waste management in north greece a decision support system for demand management in healthcare supply chains considering the epidemic outbreaks: a case study of coronavirus disease 2019 (covid-19) using metaheuristic algorithms to solve a multi-objective industrial hazardous waste location-routing problem considering incompatible waste types a stochastic multi-period industrial hazardous waste location-routing problem: integrating nsga-ii and monte carlo simulation environmental perspective of covid-19. science of the total environment a bi-level and robust optimization-based framework for a hazardous waste management problem: a real-world application a multi-objective mathematical model for the industrial hazardous waste location-routing problem solid waste management through the applications of mathematical models a robust periodic capacitated arc routing problem for urban waste collection considering drivers and crew's working time developing an applied algorithm for multi-trip vehicle routing problem with time windows in urban waste collection: a case study a robust green location-allocation-inventory problem to design an urban waste management system under uncertainty a robust green traffic-based routing problem for perishable products distribution fuzzy mathematical programming and self-adaptive artificial fish swarm algorithm for just-in-time energy-aware flow shop scheduling problem with outsourcing option disinfection technology of hospital wastes and wastewater: suggestions for disinfection strategy during coronavirus disease 2019 (covid-19) pandemic in china key: cord-254638-f86irz06 authors: sunday, michael oluwatoyin; sakugawa, hiroshi title: a simple, inexpensive method for gas-phase singlet oxygen generation from sensitizer-impregnated filters: potential application to bacteria/virus inactivation and pollutant degradation date: 2020-07-23 journal: sci total environ doi: 10.1016/j.scitotenv.2020.141186 sha: doc_id: 254638 cord_uid: f86irz06 abstract airborne infectious diseases such as the new coronavirus 2019 (covid-19) pose serious threat to human health. indoor air pollution is a problem of global environmental concern as well. singlet oxygen (1o2) is a reactive oxygen species that plays important role in bacteria/virus inactivation and pollutant degradation. in this study, we found that commercially available filters typically deployed in air purifier and air conditioning units, impregnated with rose bengal (rb) as a 1o2 sensitizer, can be used for heterogeneous gas-phase generation of 1o2. it was confirmed that irradiation of the rb filter under oxygen gas stream produced 1o2, which was measured using furfuryl alcohol trapping method followed by hplc analysis. it was also observed that the amount of 1o2 generated increases as the light intensity increased. similarly, the sensitizer loading also positively influenced the 1o2 generation. the heterogeneous gas-phase generation of 1o2 can find potential applications in air purifier and air conditioning units for the purpose of bacteria/virus inactivation and/or pollutant degradation thereby improving indoor air quality. j o u r n a l p r e -p r o o f 3 pollutants (latch et al., 2003; liu et al., 2011; kim et al., 2012; xie et al., 2018; blacha-grzechnik et al., 2020) and inactivation of bacteria/virus (banks et al., 1985; dahl et al., 1987 dahl et al., ,1988 lenard et al., 1993; nitzan et al., 1995; wainwright et al., 1998; usacheva et al., 2001; villen et al, 2006; bartusik et al, 2012; costa et al., 2012; felgenträger et al., 2014; kim et al., 2020) . photodynamic inactivation (pdi), which involves generating ros such as 1 o 2 upon irradiation of a sensitizer, has been deployed to inactivate a wide range of bacteria and viruses. pdi occurs via two mechanisms, namely: type i mechanism involving the generation of free radicals, and type ii mechanisms involving 1 o 2 . type ii mechanism involving generation of 1 o 2 has been shown to be the predominant mechanism of bacteria/virus inactivation (costa et al., 2012) . comprehensive reviews highlighting the various bacteria (hamblin and hasan, 2004; liu et al., 2015) and viruses (costa et al., 2012) inactivated by 1 o 2 are available in literature. viruses including human immunodeficiency virus (hiv), influenza virus, sendai virus (lenard et al., 1993) , dengue virus (huang et al., 2004) , vaccinia virus (turner and kaplan, 1968) , adenovirus (schagen et al., 1999) , enterovirus (wong et al., 2010) etc. have all been reported to be inactivated by 1 o 2 . in addition, it was showed that herpesvirus and influenza virus (enveloped type) and adenovirus and poliovirus (unenveloped type) were inactivated by 1 o 2 using a spray of j o u r n a l p r e -p r o o f the above-mentioned reports majorly involved homogeneous 1 o 2 generation. however, homogeneous generation in aqueous phase cannot be easily deployed to provide 1 o 2 needed in the gas phase for potential indoor air purification. 1 o 2 can also be generated from heterogeneous systems where a solid-state sensitizer, either in isolation or deposited by physical and/or chemical modification onto another solid substance, is irradiated in the presence of oxygen gas to generate 1 o 2, which flows along with the gas stream into a collecting solution where it reacts with a substrate. reaction of the formed 1 o 2 with the selective substrate in solution provides evidence of 1 o 2 generation from the solid-gas heterogeneous system. in addition to substrate solution, involvement of 1 o 2 in the deactivation of bacteria and viruses in air has also been reported. kim et al (2020) showed that 1 o 2 inactivated micro-organisms in air up to a distance of 10 -15 cm away from the source. several researchers have presented different experimental set-ups based on this heterogeneous system and demonstrated 1 o 2 generation from them with further application of the generated 1 o 2 for substrate degradation or bacteria/virus inactivation (bartusik et al., 2012a (bartusik et al., , 2012b zamadar et al., 2009; aebisher et al., 2010; carpenter et al., 2015; zhao et al., 2014; hettegger et al., 2015) . nevertheless, the potential application of 1 o 2 for the purpose of improved air quality has not been well explored. one way of achieving that is to develop products that can generate 1 o 2 in the gas phase. such products will help to inactivate micro-organisms in the indoor environment and may find applications as air purifiers in places like small rooms or offices, on automobiles, trains and even hand dryers. this will make a significant contribution towards cleaner indoor air by removing bacteria/virus or pollutants present in the air. in this study, we present a simple, inexpensive set-up, designed from commonly available materials, for gas-phase 1 o 2 generation. a filter material typically employed in the air purifier j o u r n a l p r e -p r o o f 5 and air conditioning units was impregnated with rose bengal and irradiated using a panel of led lights. furfuryl alcohol (ffa) in solution was used as a substrate to provide qualitative and quantitative evidence of 1 o 2 generation from the filter. the reagents and materials used are listed in supplementary information (s1). rb stock was prepared by dissolving 10 g rb in 150 g of the supplied gel. two pieces of filters of the same dimension (l × w: 7 × 2.2 cm) were cut-out from the same filter material and their initial weights were obtained. rb was physically impregnated into one of the filters by completely immersing it in the rb-dissolved gel for 5 minutes. the gel was necessary to help impregnate rb in the filter because of the hydrophobic nature of the filter. the other filter was treated with a blank gel and used as the control filter. both filters were dried overnight using cold air from an air drier. treating the control filter with the blank gel helped to account for the contribution of the gel to the weight of the filters after drying. the rb-treated filter was further subjected to air blowing to remove any loosely adhered rb particles on the filter. the images of the rb-treated and control filters are presented in fig s2. thereafter, the amount of rb impregnated into the filter was determined gravimetrically from the difference in the weight of the filter before impregnation and weight after impregnation (dry, rb-impregnated filter). the amount of rb per area of filter (mg/ cm 2 ) was then calculated. to investigate the effect of sensitizer loading on 1 o 2 generation, different filters were impregnated with varying amounts of rb. this was done by firstly preparing serial dilutions (10, j o u r n a l p r e -p r o o f 6 with these dilute solutions ( fig s2) . the amount of rb impregnated into the filters from treatment with different solutions of rb was also calculated. a schematic diagram of the set-up in this study is shown in fig. 1a the glass column where the rb-impregnated filter had been attached was then covered by a hydrophobic ptfe filter which was glued to the edges of the glass column and secured tightly to the sides of the column using transparent tapes. the column was stoppered at the top using a silicon stopper with hole. a capillary tube was inserted into the glass column through the hole of the stopper. the tube delivered oxygen gas to the surface of the rb-impregnated filter at a rate of 0.1 -0.2 l/min. the stopper ensured that the top of the column was air-tight preventing any loss of oxygen through the top. the stability of this assembly and monitoring potential leakage or damage was ensured by immersing the assembly firstly in ultrapure water for about 5 minutes prior to immersion in the substrate solution. this preliminary immersion test showed that there was no leakage or leaching of rb into the solution. this rules out any possibility of aqueous phase contribution to 1 o 2 generation. the test also showed that at the immersion depth, the gas stream was sufficiently contacting the solution and was not just directly escaping into the air in the laboratory. this was necessary to ensure optimal contact between the 1 o 2 in the gas stream journal pre-proof j o u r n a l p r e -p r o o f 7 and the substrate solution. this shows that potential 1 o 2 exiting the filter along with oxygen flow will contact the reacting solution. the irradiation light was suspended above the glass column. the light was from a locally fabricated led panel (excel co. ltd., fukuyama, japan) consisting of 60 led bulbs emitting white light with a power output of up to 144 w when the full irradiation mode is adopted. the spectrum of the irradiation light was obtained using a miniature spectrophotometer device four ml solution of 100 µm ffa in d 2 o was employed as a substrate to demonstrate 1 o 2 generation from the irradiation of impregnated filter. 1 o 2 reacts with ffa to produce 6-hydroxyl-2h-pyran-3(6h)-one (6-hp-one) as a major product (haag et al., 1984) . 1 o 2 arriving in the solution was monitored indirectly through the degradation of ffa and corresponding formation of 6-hp-one by hplc analysis (supplementary info. s2). although 1 o 2 was not generated in solution in this experiment, but in the gas-phase from the irradiation of rb-treated filter, the determined photoformation rate (calculated in solution) is indicative of the amount of 1 o 2 arriving in the substrate solution. this is expected to be lesser than that generated from the filter due to quenching of some 1 o 2 as it travels through the pores of the filter, or by the gas stream before successfully contacting the substrate solution. therefore, the obtained information on 1 o 2 generation from the filter can be regarded as an estimate. j o u r n a l p r e -p r o o f 8 the 1 o 2 in the oxygen gas stream passing through the filter and arriving in the substrate solution was monitored indirectly by following the peaks of ffa degradation and 6-hp-one formation. monitoring 6-hp-one formation confirms that the degradation of ffa is due to chemical reaction with 1 o 2 arriving from the filter into the substrate solution. a typical plot showing the degradation of ffa and corresponding formation of 6-hp-one is shown in fig. 2a . furthermore, the degradation of ffa due to 1 o 2 followed a first order kinetics. the first order plot of ffa degradation during irradiation of rb-treated filter and untreated (blank) filter is shown in fig. 2b . irradiation of the rb-treated filter caused a significant degradation of ffa compared to the blank filter. the value obtained for the blank filter was similar to that obtained when the ffa solution was directly irradiated with oxygen flowing into the solution in the absence of the filter assembly. this suggests that the blank filter had no significant contribution to 1 o 2 formation and that the rb-treated filter was solely responsible for the formed 1 o 2 . in addition, there was no leaching of rb into solution during the irradiation. this is because the hydrophobic ptfe filter shielded the rb-treated filter from directly contacting the solution. this is a very important precaution because rb is highly soluble (100 mg/ml) in water. therefore, any contact between the rb-treated filter and the solution will encourage a massive leaching or dissolution of rb. under such scenario, there will be aqueous phase contribution to 1 o 2 generation. no leaching of rb, in part or whole, was observed during our experiments. this shows that the only source of the solvent isotope effect and the influence of 1 o 2 scavengers are two important ways of demonstrating the generation and involvement of 1 o 2 in a particular reaction. to confirm the presence of 1 o 2 in the gas stream arriving in the substrate solution, the solvent isotope effect was (haag et al, 1984) for the reaction of 1 o 2 with ffa in h 2 o, the 100 µm ffa concentration only made an insignificant 4% contribution to the deactivation rate constant of 2.5 × 10 5 s -1 for 1 o 2 in h 2 o. this shows that the solvent isotope effect is mainly due to collision with the solvents, without any significant contribution from the physical quenching of 1 o 2 by ffa. in addition, the effect of 1 o 2 scavenger on the degradation of ffa in d 2 o was studied using nan 3 as a scavenger. nan 3 is an efficient scavenger of 1 o 2 with a second order rate constant of journal pre-proof j o u r n a l p r e -p r o o f 7.8 × 10 8 m -1 s -1 (wilkinson and brummer, 1981) . the degradation of ffa in d 2 o was observed to reduce significantly in the presence of 1 mm nan 3 compared to its absence (ffa + d 2 o, no nan 3 ) (fig. 3) . this further confirms the generation of 1 o 2 . the results of the solvent isotope effect and nan 3 scavenger experiment clearly confirm that 1 o 2 is present in the gas stream arriving in the substrate solution, and it is responsible for the degradation of ffa. to investigate how light intensity can influence the generation of 1 o 2 , the intensity of the irradiation light was varied by employing the full-power mode and half-power mode of the irradiation light and/or increasing the distance between the filter and irradiation light. a plot of the amount of 1 o 2 detected in solution, during the irradiation of rb-treated filter, as a function of light intensity is shown in fig. 4 . it is observed that the amount of 1 o 2 generated increased as the light intensity increases. the sharp increase between 1196 and 1861 μmole s -1 cm -2 suggest a regime of light intensity where higher production of 1 o 2 is observed. based on the present experimental set-up, the distance between the irradiation light and filter is 11 cm. in an application where the light source is closer to the filter, the light intensity will be much higher and 1 o 2 generation can be expected to be much higher. the effect of the amount of rb adsorbed by the filter on 1 o 2 production was investigated by table 1 . it is observed that 1 o 2 generation increased as the amount of rb adsorbed on the filter increased. the maximum solubility of rb in the gel was 10 g rb in 150 g of gel. this was the same solution used as the undiluted stock in table 1 . therefore, the effect of amount of adsorbed rb on 1 o 2 generation could not be studied beyond this point. using the undiluted stock as the highest rb loading possible, the amount of 1 o 2 reaching the solution was calculated to be 12.8 μmole s -1 of 1 o 2 per mole of rb. it should be noted that the amount of 1 o 2 generated on the surface of the filter may be several orders of magnitude higher than the value reported here due to the heterogeneous distribution of 1 o 2 generation. it has been demonstrated for aqueous solutions that 1 o 2 generation in the dom microenvironment could be up to three orders of magnitude higher than in the bulk solution due to physical quenching as the 1 o 2 diffuses into the bulk solution (latch et al., 2006; grandbois et al., 2008) . a similar explanation could be adopted here where the 1 o 2 generated on the surface of the filter may undergo significant quenching before arriving in the substrate solution. this quenching may be caused by the filters (both treated filters and hydrophobic ptfe filter) as the gas stream containing 1 o 2 migrates from the irradiated side of the filter to the substrate solution. also, quenching by ground-state molecular oxygen may also arise. therefore, the quantity of singlet oxygen reported here can only be considered as a minimum. nevertheless, in the real applications, the filters will be directly exposed to light, while air is circulated or brought into contact with the filter. under such circumstances, the amount of generated on the surface of the filter is >> than 1 o 2 migrating further away from the filter into the air. therefore, contaminated air will encounter a large amount of 1 o 2 on the surface of the filter that will be significant towards bacteria/virus inactivation. (schweitzer and schmidt, 2003) while that of ·oh ranges between 0.01 -1s (crosley et al., 2017) . the lifetimes of both ·oh and 1 o 2 may be lower depending on the nature of other substances present. hence, these values can be considered to be their upper limit values at ground-levels in the atmosphere. nevertheless, the use of rb as sensitizer, which has a high 1 o 2 quantum yield (0.76) (wilkinson et al., 1992) , can ensure relatively high production of 1 o 2 . therefore, more 1 o 2 can be available for bacteria/virus inactivation in 1 o 2 -based air purifiers compared to ·oh in ·oh-based systems. in addition, the system proposed in this study makes use of simple, cheap and commercially-available led light sources emitting white light in the visible region, in-line with the λmax of rb (550 nm). such light source is relatively simple, easier to handle and maintain. the findings from this study can contribute significantly to the development of 1 o 2 -based air purifiers with potential applications in small or large indoor environments in offices, at homes or even on automobiles and trains. such products are necessary to contribute to improved indoor air quality considering the outbreak of airborne viral infections such as the present covid-19. although this is a preliminary study, the findings from this study have led to the development of a prototype where additional parameters necessary for its deployment are being studied. generator device serving as a point selective sterilizer the cytotoxic and photodynamic inactivation of micro-organisms by rose bengal bacteria inactivation by a singlet oxygen bubbler. identifying factors controlling the toxicity of 1 o 2 bubbles generating 1 o 2 bubbles: a new mechanism for gas-liquid oxidations in water efficient generation of singlet oxygen by perylene diimide photosensitizers covalently bound to conjugate polymers gas-phase photolytic production of hydroxyl radicals in an ultraviolet purifier for air and surfaces pure 1 o 2 cytotoxicity for bacteria comparison of photodynamic action by rose bengal in gram-positive and gram-negative bacteria inactivation of ebola virus and middle east respiratory syndrome coronavirus in platelet concentrates and plasma by ultraviolet c light and methylene blue plus visible light 1 o 2 generation in porphyrin-doped polymeric surface coating enables antimicrobial effects of staphylococcus aureus microheterogeneous concentrations of singlet oxygen in natural organic matter isolate solutions singlet oxygen in surface waters photodynamic treatment of adenoviral vectors with visible light: an easy and convenient method for viral inactivation physical mechanism of generation and deactivation of singlet oxygen photoinactivation of vaccinia virus with rose bengal comparison of the methylene blue and toluidine blue photobactericidal efficacy against gram-positive and gram-negative microorganisms aerosol and surface stability of sars-cov-2 as compared with sars-cov-1 solar water disinfection by photocatalytic singlet oxygen production in heterogeneous medium photobactericidal activity of phenothiazinium dyes against methicillin-resistant strains of staphylococcus aureus quantum yields for the photosensitized formation of the lowest electronically excited singlet state of molecular oxygen in solution methylene bluemediated photodynamic inactivation as a novel disinfectant of enterovirus 71 a mechanistic kinetic model for singlet oxygen mediated self-sensitized photo-oxidation of organic pollutants in water 1 o 2 delivery through the porous cap of a hollowcore fiber optic device 1 o 2 generation on porous superhydrophobic surfaces: effect of gas flow and sensitizer wetting on trapping efficiency photocatalytic air cleaners and materials technologies -abilities and limitations we are grateful to yokota kogyo shokai co. inc., hiroshima, japan for providing research funding for this study. we also appreciate prof. kazuhiko takeda of the graduate school of biosphere science, hiroshima university, for the advice rendered during this study.journal pre-proof j o u r n a l p r e -p r o o f the authors declare that there is no conflict of interest regarding this publication. key: cord-296986-8fuj072z authors: kumar, manish; taki, kaling; gahlot, rohit; sharma, ayushi; dhangar, kiran title: a chronicle of sars-cov-2: part-i epidemiology, diagnosis, prognosis, transmission and treatment date: 2020-05-15 journal: sci total environ doi: 10.1016/j.scitotenv.2020.139278 sha: doc_id: 296986 cord_uid: 8fuj072z abstract in order to benefit the public, community workers and scientific community, we hereby present a chronicle of sars-cov-2 that leads to the unseen precedent of social distancing and lockdown owing to coronavirus disease (covid-19). information on this life-threatening pandemic of covid-19 is sparse and discrete; and the urgency is such that the dissemination of information is increasing with numerous daily publications on the topic. therefore, we developed a comprehensive review on various aspects of sars-cov-2 and covid-19. we scientifically compiled published research, news, and reports from various sources to comprehend and summarize the information and findings on coronaviruses. the review explicitly covers the aspects like genome and pedigree of sars-cov-2; epidemiology, prognosis, pathogenesis, symptoms and diagnosis of covid-19 in order to catalog the right information on transmission route, and influence of environmental factors on virus transmissions, for the robust understanding of right strategical steps for proper covid-19 management. we have explicitly highlighted several useful information and facts like: i) no established relationship between progression of sars-cov-2 with temperature, humidity and/or both, ii) the underlying mechanism of sars-cov-2 is not fully understood, iii) respiratory droplet size determines drop and airborne-based transmission, iv) prognosis of covid-19 can be done by its effects on various body organs, v) infection can be stopped by restricting the binding of s protein and ae2, vi) hydroxychloroquine is believed to be better than chloroquine for covid-19, vii) ivermectin with vero-hslam cells is able to reduce infection by ~5000 time within 2 days, and viii) nafamostat mesylate can inhibit sars-cov-2 s protein-initiated membrane fusion. we have also suggested future research perspectives, challenges and scope. j o u r n a l p r e -p r o o f 8 overall, who defines covid-19 patient as: i) an individual with acute respiratory illness like fever and/or any sign of respiratory ailments like cough, sore throat, and/or has a travel history to locations reported community covid-19 spread during the 14 days prior to the onset of symptoms. or (2) an individual with any acute respiratory illness and/or been in contact with a confirmed or probable covid-19 individual in the last 14 days. or (3) an individual with severe acute respiratory illness with unexplained clinical diagnosis of alternate reasons for the problem. the central idea is to consider even a slightest probable case as a suspected patient based on above points with inconclusive or awaiting test results. while, a laboratory confirmed case is a person with a laboratory confirmation i.e. tested positive for covid-19, irrespective of clinical signs and symptoms (asymptomatic patient). the trickiest feature of covid-19 has lately been identified as being the asymptomatic (up to 60% in india). the risk is so heavy, spread is so fast and symptoms are of so varying nature that even travelling to a community spread country or being a physical contact of an infected person are being treated as symptoms. diagnostic testing for the sars-cov-2 is currently undertaken using two approaches: whole genome sequencing and real-time reverse transcriptase-polymerase chain reaction (rrt-pcr, nucleic acid testing). table 1 compiles the emerging diagnostics techniques being used/developed for sars-cov-2. the sequencing approach was used primarily in the early days of the outbreak, almost all diagnostic testing for sars-cov-2 is done using rrt-pcr . many companies also launched rt-qpcr test kits to assist clinical diagnosis chu et. al. (2020) described two 1-step rtqpcr assays to detect two different regions (orf1b and n) of the viral genome. saliva serves as a promising non-invasive specimen for the j o u r n a l p r e -p r o o f 9 diagnosis of covid-19 patients with a high positive rate of 91.7% (11/12) in determining the disease using rt-qpcr (non-probes sybr based fluorescence signal) . though this technique has a sensitivity of 50%-79% of detection, depending on the protocol used and the sample type; the number of clinical specimens collected (yam et. al., 2020) , safety hazards and detection time are some issues. ct scan is suggested as an auxiliary diagnostic method to avoid reporting false results and to increase sensitivity . early diagnosis and evaluation of disease severity of covid-19 patients can be performed using high-resolution ct (hrct) scan of the chest . however, inability to differentiate from other viral pneumonia makes the interpretation of the hysteresis of abnormal ct imaging tedious and inadequate . nevertheless, the chest ct had a very low misdiagnosed rate (3.9%, 2/51) in comparison with any other method. in previous studies on sars or mers, lung parenchymal irregularity was reported in the central and bilateral upper lobes of lungs (das et. al., 2016; paul et. al., 2004) . however, li and xia (2020) showed that the peripheral (sub-pleural), and middle and lower zones of lungs showed an abnormality at the initial stages, followed by affecting the upper lobes, and in severe cases, all five lobes of both lungs were affected. recently, the center for disease control and prevention (cdc) is working on serologic (antibody) immunoassays (ias) testing i.e. protein testing, for diagnosis of covid-19 (vashist, 2020 (vashist, 2020) . further, wastewater based epidemiological (wbe) surveillance for the genetic material of sars-cov-19 has drawn loads of attention that can be helpful in early detection as well as resurgence of covid-19 (kumar et al., 2019a,b; kumar et al., 2020a,b,c; kitajima et al., 2020) . wbe surveillance are expected to become handy for the potential eradication of the virus in a community. sars-cov-2 moves from the back of the throat to the lungs and then ultimately into the blood. all coronaviruses contain specific genes in downstream regions of orf1 that encode proteins for viral replication, nucleocapsid, and spikes formation (van et. al., 2012) . sars-cov-2 and sars-cov binds with a receptor called angiotensin-converting enzyme 2 (ace-2) found on the respiratory cells with the help of s protein, which helps in entry and replication for further spreading the infection. the receptor-binding domain (rbd) is loosely attached among viruses leading to infection of multiple host (raj et. al., 2013; perlman and netland, 2009 ). fig. 4 (a) demonstrates the interaction of viral s protein with ace-2 on the host cell surface which is highly significant being an initiation step of infection/pathogenicity. cryogenic electronic microscopic structure analysis revealed that the binding affinity of s protein to ace-2 is about 10−20 times higher for sars-cov-2 than that of sars-cov, which is the reason for the higher transmissibility and contagiousness of sars-cov-2 as compared to sars-cov. after , however, there still exists a lack of information about the antigen presentation of sars-cov-2. therefore, till date, no sars-cov-2 specific antiviral agents could be discovered for a possible treatment to save lives and to produce an effective vaccine for future prevention. demonstrates the progression of sars-cov-2 inside the host body. inflammatory response of ards is mainly caused by the release of large amounts of pro-inflammatory cytokines known as 'cytokine storm' . sars-cov-2 infection undergoes 'cytokine storm' that triggers viral sepsis and inflammatory-induced lung injury leading to complications like pneumonitis, respiratory failure, ards, shock, organ failure, and potentially death , prompetchara et. al., 2020 . during the cytokine storm mechanism in the body a wide variety of cytokines (ifn-α, ifn-γ, il-1β, il-6, il-12, il-18, il-33, tnf-α, tgfβ, and others) and chemokines (ccl2, ccl3, ccl5, cxcl8, cxcl9, cxcl10, and j o u r n a l p r e -p r o o f 12 others) are released william and chambers, 2014; cameron et al., 2008) . although, the detailed beneficial role of cytokines is unclear currently due to the recent progression of the disease, there are already clinically tested drugs available which may add value to the current treatment process of cytokine storm. interleukin-6 inhibitors, or il-6 inhibitors drugs, which were found to be helpful in patients of france, china, and new york works based on blocking a specific cytokine associated with inflammation. further, supplementary table-2 shows various supporting statements given by doctors and researchers regarding 'cytokine storm' mechanisms and response in our body. overall, understanding of immuno-pathological mechanism of sars-cov-2 infection has great potential to develop therapeutic strategies to contain the pandemic. the prognosis of covid-19 can be done by its effects on various body organs. the recovery rate from the infection of covid-19 is varying based on its severity. people with mild condition (with few or no symptoms having a resemblance to some upper respiratory diseases such as common cold) are recovering within two weeks, the recovery duration can go up to six weeks for severe or critical disease cases. two to eight weeks of duration from the symptoms onset has 16-24 february 2020). various complications and health issues associated with covid-19 have been reported, like pneumonia affecting lungs, ards which may lead to respiratory and multiorgan failure (cascella et. al., 2020; heymannand and shindo, 2020) , abnormal clotting, sepsis and damage to kidney, liver, and heart . in order to understand the severity of the virus outbreak, it is crucial to focus on the population groups which are at high risk, which will allow them to direct the resources towards the most vulnerable. high variance among the age groups. the age group of >80 years is considered a vulnerable age group due to highest death risk associated with it in all the countries. however, the age group below 50 years, and children can have mild symptoms, but the risk of death is low. the cfr caused by covid-19 is distinctive than the other historical pandemics like malaria and spanish flu, where the most vulnerable age group was children or young adults. however, in the case of covid-19, along with the age group the underlying health conditions also have a significant impact on the death risk ( fig. 5(b) ). the early-stage cfr data of china shows that people with underlying health conditions such as cardiovascular disease, cancer, hypertension, chronic respiratory disease, and diabetes, are at higher risk (who, 23 rd january 2020). the cfr due to covid-19 was highest for those underlying cardiovascular disease (10.5%), followed by diabetes (7.3%), chronic respiratory disease (6.3%), hypertension (6.0%), and cancer (5.6%). a comparison suggests that people with no previous underlying health condition had ten times lesser cfr (0.9%) and thus the elderly age group with pre-existing health conditions are more. j o u r n a l p r e -p r o o f 14 overall, the susceptibility and recovery of the disease is highly dependent upon the innate immunity of the person. transmission. however, to date, no such study has been conducted that could establish a relationship between the fecal−oral transmission of the sars-cov-2. zhou et. al., 2020b reported that viral shedding is one of the most significant ways of transmission and observed that the viral shedding was found to last for 37 days in survivors. the amount of viral load contributed to the environment by asymptomatic and symptomatic patients was conducted by bai et. al., 2020 and zou et. al., 2020a . the authors reported that transmission was possible even in the case of asymptomatic patients, but in the case of symptomatic patients increase in viral loads was observed. as of now, the environmental factors that has been studied to understand the covid-19 transmissions, are the ambient environmental temperature, humidity but still, no authenticity on the relationship is confirmed yet kumar et al., 2020a ; tobias and molina 2020). apart from climatic conditions (temperature and humidity), the transmission may be further triggered by population and medical facility (dalziel et. al., 2018; hemmes et. al., 1960) . based on the assumption that the sars-cov-2 is similar to sars-cov, it has been hypothesized that the sars-cov-2 may not survive at high temperature and humidity (chan et. al. 2011 , kumar et al., 2020 tobias and molina, 2020) the underlying hypothesis of decrease in the spread of viruses during warmer seasons is higher vitamin d levels, resulting in better immune responses (aranow, 2011; kumar et al., 2020) . interestingly, a common man notion is that in cold weather, people tend to stay inside, often in a closed room, at times close to each other, and that enhances the infection probability. a study confirmed a strong relationship does exist between the reported cases, temperature, and absolute with the findings for the influenza virus (park et. al., 2020; steel et. al., 2011; lipsitch and viboud, 2009; shaman and kohn, 2009) , where the high temperature and high humidity leads to a significant reduction in transmission of the influenza virus. this might be due to the following reasons: (i) cold and dry weather might cause weakness in the immunity of the host (kudo et. al., 2019; eccles, 2002) , (ii) unlike influenza virus they might be more stable in lower temperature and within the respiratory droplets (lowen and steel, 2014; tellier, 2009) . also, the observations made for sars cov for temperature and humidity (chan et. al., 2011; yuan et. al., 2006) were inconsistent with the findings of wang et. al., 2020. li et. al., 2020 reported at present, there is no proven antiviral agent that can control the covid-19 outbreak and inactivate sars-cov-2. by 29 th april 2020, no drug has been approved by us food and drug administration that can prevent covid-19. currently, management strategies for covid-19 patients with mild symptoms include infection prevention by using oseltamivir/ intravenous antibiotics, clinical supportive measures for severe patients such as oxygen and mechanical ventilator support . some of the therapeutics drugs and therapy reduction in viral rna (caly et. al., 2020) . another drug, nafamostat mesylate (fusan) as demonstrated by japanese researchers can inhibit the fusion of sars-cov-2 (s) protein and initiated membrane at achievable and safe concentrations in the patients (hannah, 2020) . remdesivir is an antiviral drug that is intravenous and inhibits the synthesis of viral rna by preventing the replication of rna by early termination of rna transcription . lo et. al. (2017) successfully demonstrated that remdesivir is a potent antiviral towards sars and mers-cov. as per the cdc, "remdesivir has in-vitro activity against sars-cov-2 and in-vitro and in-vivo activity against related beta coronaviruses". hydroxychloroquine and chloroquine are anti-malarial drugs that are taken through oral administration, and both of the drugs belong to the quinolone family. yazdany and kim (2020) demonstrated that both the medicines have a potent antiviral property that can control sars-cov-2 in-vitro. roque (2020) reported that the use of hydroxychloroquine is much safer and has more potential of inhibiting sars-cov-2. hydroxychloroquine has been proven more successful than chloroquine (inhibition rate did not exceed 50% ) at inhibiting sars-cov-2 . paton et. al. (2011 ), ooi et. al. (2006 reported negative results of hydroxychloroquine and chloroquine during random testing for influenza in random patients. henceforth, there is lack of report, facts and figures to support the use of hydroxychloroquine and chloroquine as an efficient treatment mechanism (yazdany and kim, 2020) . j o u r n a l p r e -p r o o f 19 early signs are that convalescent plasma therapy can reduce the mortality rate in sars-cov-2 patients (cheng et. al., 2005; lai, 2005; soo et. al., 2004) . mair-jenkins et. al., 2015 showed recovery from sars-cov-2 at early-stage of treatment with convalesced plasma therapy. unlike sars-cov (mair-jenkins et. al., 2015) and mers-cov (koenig et. al., 2015 , many patients are donating plasma with sars-cov-2 antibodies to control covid-19. duan et. al., 2020 demonstrated the potential of convalescent plasma therapy to treat the severe covid-19 patients. 10 patients were treated with plasma therapy, a 200 ml of convalescent plasma neutralize with antibody titers above 1:640 was given to the patients who showed rapid improvement in symptoms with three days of convalescent plasma transfusion. however, treatment by convalescent plasma therapy is still questionable . covid-19 is a severe global health issue which is caused by sars-cov-2. the genomic study revealed that the phylogeny of the sars-cov-2 is very similar to sars-like bat/pangolin. the disease result in respiratory illness like sars-cov and mers-cov and may cause death in severe cases. the mortality is significantly higher in the elderly age group, mostly having preexisting health conditions. at the initial stage the disease may be identified by symptoms such as fever, dry cough, muscle pain and fatigue but challenge of identifying the asymptomatic patient is huge. the transmission is mainly through the respiratory droplets and their diameters, and through direct contact with an infected surface. in the case of airborne transmission, the probability of being infected is very less and case-specific. the higher transmissibility and contagiousness of sars-cov-2 may be attributed to the high binding affinity of sars-cov-2, s protein to ace2. the rapid transmission is due to the weak linkage between the receptor-j o u r n a l p r e -p r o o f 20 binding domain (rbd) of sars-cov2 and the host cell. some of the profound drugs available to control cytokine storm are interleukin-6 inhibitors or il-6 inhibitors, but for older people or people with past medical histories inhibiting the immune system may result in severe health issues. one of the probable ways to curb the infection is to restrict the binding between s protein of sars-cov-2 to ace2. though the cause and effects are known still the transmission mechanism is not fully understood. 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factors for mortality of adult inpatients with covid-19 in wuhan, china: a retrospective cohort study. the lancet discovery of a novel coronavirus associated with the recent pneumonia outbreak in humans and its potential bat origin sars-cov-2 viral load in upper respiratory specimens of infected patients we acknowledge the moral support of various initiatives started by the administration of iit gandhinagar. we also acknowledge the help received from ms. payal mazumder, dr. arbind patel, mr alok k thakur and anonymous referees. serum gold-coated antibodies produce colorimetric signal on paper in presence of target. 2 bosch et. al., 2017; 3 amer et. al., 2013; 4 martel et. al., 2013; 5 rissin et. al., 2010; 6 wat et. al., 2008; 7 imai et. al., 2007; 8 shirato et. al., 2007; 9 rowe et. al., 1999 key: cord-268278-owmcxq9e authors: lin, yu-kai; chang, chin-kuo; li, ming-hsu; wu, yu-chung; wang, yu-chun title: high-temperature indices associated with mortality and outpatient visits: characterizing the association with elevated temperature()() date: 2012-06-15 journal: sci total environ doi: 10.1016/j.scitotenv.2012.04.039 sha: doc_id: 268278 cord_uid: owmcxq9e this study aimed to identify optimal high-temperature indices to predict risks of all-cause mortality and outpatient visits for subtropical islanders in warm seasons (may to october). eight high-temperature indices, including three single measurements (average, maximum and minimum temperature) and five composite indices (heat index, humidex, temperature humidity index, apparent temperature and wet-bulb globe temperature), and their standardized z scores, were used in distributed lag non-linear models. cumulative 8-day (lag zero to seven days) relative risks (rrs) and 95% confidence intervals were estimated, 1 and 2 standardized deviations above the medium (i.e., at 84.1th and 97.7th percentile, respectively), by comparing with z scores for the lowest risks of mortality and outpatient visits as references. analyses were performed for taipei in north, central taiwan and southern taiwan. results showed that standardized z-values of high-temperature indices associated with the lowest health risk were approximately 0 in taipei and central taiwan, and − 1 in southern taiwan. as the apparent temperature was at z = 2, the cumulative 8-day mortality risk increased significantly, by 23% in taipei and 28% in southern taiwan, but not in central taiwan. the maximum temperature displayed consistently a high correlation with all-cause outpatient visits at z = 1; with the cumulative 8-day rrs for outpatient visits increased by 7%, 3%, and 4% in the three corresponding areas. in conclusion, this study has demonstrated methods to compare multiple high-temperature indices associated with all-cause mortality and outpatient visits for population residing in a subtropical island. apparent temperature is an optimal indicator for predicting all-cause mortality risk, and maximum temperature is recommended to associate with outpatient visits. the impact of heat varied with study areas, evaluated health outcomes, and high-temperature indices. the increased extreme heat is associated with stronger risk for all-cause mortality than for outpatient visits. the association between temperature and mortality has been depicted with u-, v-, or j-shaped curves among various climate regions (curriero et al., 2002; gouveia et al., 2003; mcmichael et al., 2008) . the climate in recent decades is characterized with increased frequency and intensity of extreme temperatures (meehl and tebaldi, 2004) . health effects of global warming are now considered a critical issue (anderson and bell, 2011; kovats and hajat, 2008; kovats and kristie, 2006; o'neill and ebi, 2009) . most studies used ambient temperatures (i.e., average, maximum, and minimum temperature) to evaluate heat-related health effects (hajat et al., 2010; kim et al., 2006; knowlton et al., 2007; kovats et al., 2004; lin et al., 2011; yu et al., 2010; wang et al., 2012) . however, other weather indicators, such as relative humidity (rh), wind speed (ws), water science of the total environment 427-428 (2012) [41] [42] [43] [44] [45] [46] [47] [48] [49] abbreviations: aic, akaike's information criterion; at, apparent temperature; ci, confidence interval; cwb, central weather bureau; dlnm, distributed lag non-linear model; flu, influenza; hi, heat index; nhri, national health research institute; pm 10 , particulate matter less than 10 μm in aerodynamic diameter; rr, relative risk; rh, relative humidity; tcdc, taiwan centers for disease control; thi, temperature humidity index; tepa, taiwan environmental protection administration; wbgt, wet-bulb globe temperature; ws, wind speed; wvp, water vapor pressure. ☆ authors' contribution: all the authors participated in this study and contributed remarkable part of it. yk lin, ck chang, mh li and yc wang designed the study methods and obtained the research data. yc wang and yc wu performed statistical analyses. yk lin, ck chang and yc wang drafted and finalized the manuscript. all the authors have read and approved the final version of the manuscript. ☆☆ conflicts of interest: all the authors declare that this study involves no conflict of interest. vapor pressure (wvp) and thermal radiation, also affect the perception of temperature to humans. several composite indices, including heat index (hi) (hartz et al., 2012; metzger et al., 2009) , apparent temperature (at) (anderson and bell, 2009; chung et al., 2009), humidex (smoyer-tomic and rainham, 2001) and wet-bulb globe temperature (wbgt) (epstein and moran, 2006; kjellstrom et al., 2009) , have been used to evaluate health events associated with heat waves or extremely high temperatures. various high-temperature indices and approaches have been used to assess the association between mortality and heat waves or high temperature. but, no study has determined which index is optimal to predict mortality (hajat et al., 2010; vaneckova et al., 2011; . anderson et al. have indicated that, after adjusting for humidity, the temperature-mortality associations are not significantly different among using average, maximum and apparent temperature metrics (anderson and bell, 2009 ). barnett et al. (2010) suggested that no temperature index can be considered optimal because all indices are highly correlated with temperature measurements. the applied temperature measurement should be chosen according to practical concerns, i.e. the measure may provide comprehensive information (barnett et al., 2010) . thus, studies addressing the determination of an optimal high-temperature index to predict health outcomes were still far from being conclusive. most studies on the high temperature (i.e., heat wave) impact focus on mortality, and only some consider morbidity ye et al., 2012) . moreover, most studies on heat effects are performed in areas with temperate climate rather than subtropical climate (basu, 2009; kovats and kristie, 2006; ye et al., 2012) . therefore, the present study was to report high-temperature indices optimal to evaluate the all-cause mortality and outpatient visits associated with temperatures in taiwan, a subtropical island, located on the west of the pacific ocean. we evaluated models among eight standardized high-temperature indices: average, maximum, and minimum temperature, hi, temperature humidity index (thi), humidex, at, and wbgt. relative risks of all-cause mortality and outpatient visits associated with these indices were evaluated for three areas, taipei in the north, central taiwan and southern taiwan. data used in this study included vital statistics obtained from the department of health (doh), universal health insurance claims data from the national health research institute (nhri), daily meteorological data from the central weather bureau (cwb), and daily air pollution monitoring data from the taiwan environmental protection administration (tepa), all from 2000 to 2008. data representative for population structure, climate and air pollution in taiwan were collected from three major metropolitan areas: taipei, central taiwan (taichung, zhanghua and nantou), and southern taiwan (kaohsiung and pingtung), comprising 63.7% of the total 23 million population in taiwan. daily area-specific all-cause deaths (icd9 codes 000-999) were retrieved from the vital statistics dataset with underlying cause of death coded with the 9th revision of international classification of diseases (icd-9). the nhri has established a cohort of one million residents to represent all insured residents in taiwan with their electronic reimbursement claim records accessible for research purposes. disease diagnoses were coded with the 9th revision of international classification of diseases with clinical modification (icd-9-cm). daily area-specific all-cause outpatient visits (icd9 cm 000-999) were retrieved from the electronic records. cwb provided 24-hour data from 25 real-time weather monitoring stations in taiwan central weather bureau (2011) . weather conditions measured using three stations in taipei, four stations in central taiwan and four stations in southern taiwan were available for determining daily mean, maximum, and minimum temperatures, rh, dew point temperature, wvp, and ws. the tepa established air quality monitoring network in 1993 with 74 stationary monitoring stations throughout the island (taiwan environmental protection administration, 2011; taiwan governmental information office, 2008) . concentrations of ambient air pollutants, including particulate matter smaller than 10 μm in aerodynamic diameter (pm 10 ), nitrogen dioxides (no 2 ) and ozone (o 3 ), were measured and recorded hourly at each station. we analyzed daily levels of pm 10 , o 3 , and no 2 , monitored by 14, 10 and 13 general ambient environment stations in taipei, central taiwan, and southern taiwan, respectively. locations of the weather and ambient environment stations are shown in fig. 1 . the eight high-temperature indices used in this study including single temperature measurements and composite temperature indices that have been widely used in heat-health association studies are detailed in table 1 . briefly, average, maximum, and minimum temperatures were monitored hourly at the regional representative weather stations. the hi based on dry bulb temperature and rh was used in environments with temperatures above 80°f (26.7°c) and with rh above 40% (steadman, 1979) . the humidex developed by environment canada was used as the measure of subjectively perceived temperature and humidity (masterton and richardson, 1979) . to assess the temperature perception in study population (rosenberg et al., 1983) , we used the taiwan cwb adopted thi index. it is similar to the thermal discomfort index developed by the u.s. weather bureau, widely used in europe as well to assess heat discomfort (pantavou et al., 2011) . the at was used as an alternative measure of perceived temperature, which combines several environmental and physiological variables, including temperature, clothing cover, physical activity, ws and wvp (steadman, 1984) . the wbgt developed by the american conference of governmental industrial hygienists was used to estimate heat stress in the working environment. data analyses first transformed the study area (c)-specific temperature index x i (i = 1-8 for eight different high-temperature indices) on day (t) into a standardized value (z i, t c ) based on the following equation: where μ i c is the mean and σ i c is the standard deviation for hightemperature index i in warm seasons of 2000-2008. locally weighted least square regression smoother (loess) was used to test each high-temperature index (original measurements and their standardized values -z score) for associations with allcause mortality and outpatient visits. the span was set to 1, and degree was set to 2 under lag 0 day (present day). for each high-temperature index, data analysis further calculated area-specific cumulative 8-day (from lag 0 to lag 7 days) relative risks (rr) and 95% confidence intervals (ci) to determine associations with daily deaths and outpatient visits, using distributed lag nonlinear model (dlnm) (armstrong, 2006; gasparrini et al., 2010) . the model used to measure expected deaths and outpatient visits at day (t) in each area (c) would be: where y t c is the expected deaths or outpatient visits for area c on day t. a linear relationship was assumed between deaths and outpatient visits, and air pollutants -pm 10 , o 3 , and no 2 with zero thresholds and 5-day lag maximum. the x j, t c represents the air pollutants (j =1-3 for pm 10 , o 3 , and no 2 ) for area c on day t; ns(t i, t c or z i, t c , 5; lag, 3) are natural cubic splines of measurements or z-scores for each hightemperature index i =1-8. five degrees of freedom (df) for hightemperature indices and z-score were set, and the effect was accumulated for 8 days (lag 0 to 7 days) under 3 df lag stratification (also set as natural cubic splines). the smoother term of time ("time" in the model) was set to 3 df per warm seasons. moreover, year was treated as an extra categorical variable in models to control for annual variation in health outcomes (e.g. the sudden drop of outpatient visits due to epidemic of severe acute respiratory syndrome in 2003). other covariates, such as daily deaths and outpatient visits due to pneumonia and influenza (flu t c , icd9 cm codes 480-487), public holiday and day of the week (dow) were also included in the models for adjustment. we used the akaike's information criterion (aic) to measure the relative goodness of fit of statistical models. a lower aic value indicates a better model fit (akaike, 1973) . because values and ranges of the high-temperature index varied dramatically, and we were unable to report the risk estimates per 1 degree change under natural cubic spline function for high-temperature indices. the area-specific cumulative 8-day relative risks for deaths and outpatient visits were reported at standardized deviations of 1 and 2 above mean (i.e., at 84.1th and 97.7th percentile, respectively), and were compared with the standardized score of the lowest health risk for each high-temperature index. basically, the standardized score for the lowest health risk was inspected from each plot of standardized high-temperature index-health association. this method was similar to estimate relative risks of various temperature indices at the 95th, 96th, 97th, 98th, 99th, and 99.5th percentiles, which had been used previously in the australian study (vaneckova et al., 2011) . data management and all statistical analyses were performed using sas version 9.1 (sas institute inc., cary, nc, usa) and statistical environment r 2.12. table 2 depicts the descriptive statistics for climatic factors, hightemperature indices and air pollutants in the three study areas during may-october in 2000-2008. both the highest and lowest average temperatures appeared in taipei. average rh ranged from 53% to 98%, and average ws ranged from 0.60 to 12.0 m/s in study areas. air pollutant concentrations were similar among areas except that average pm 10 and o 3 concentrations were higher in southern taiwan. the correlation coefficients between each pairs of the eight hightemperature indices ranged from 0.61 to 0.99, the lowest correlation was between maximum and minimum temperature, and the higher correlations were among the composite high-temperature (r 2 = 0.89 to 0.99) (data not shown). fig. 2 shows the association between high-temperature indices (lag 0 day) and daily all-cause deaths measured using loess. the high-temperature indices varied among areas, with wider ranges for original high-temperature indices in taipei. after standardization for these indices, the regression lines showed a similar pattern of association for z scores ranged within ±2 standard deviation. a u-shaped temperature-mortality association was observed in taipei. an observed positive linear relationship between mortality and high temperatures was identified in southern taiwan. no significant association with high temperature was detected in central taiwan. fig. 3 shows the association between high-temperature indices and outpatient visits on lag 0 day measured using loess. there were larger variations at z scores lower than −2 (i.e., extremely low percentiles in warm seasons). in contrast with all-cause mortality, the outpatient visits were not significantly associated with extreme high temperatures in any of the study areas. the aic values among various models for associations between high-temperature indices and all-cause models were similar (table 3) . based on the selection criteria for modeling, at was the most optimal index in taipei and southern taiwan, but humidex or wbgt was most optimal in central taiwan. supplemental figures 1-3 show the cumulative 8-day relatively risk of all-cause mortality associated with high-temperature indices and their transformed standardized values. the lowest mortality risks were identified at z = 0 for taipei and central taiwan, and at z= −1 for southern taiwan. therefore, these transformed standardized scores were used as reference values in further analyses. at the transformed high-temperature index of z=1 (84.1th percentile of high-temperature indices), the mortality risk approximately increased by 3%, 1% and 9% in taipei, central taiwan and southern taiwan, respectively. as of z=2 (97.7th percentile of hightemperature indices) for at, the cumulative relative risks for mortality significantly increased by 23% in taipei and by 28% in southern taiwan. there was no significant increase in central taiwan. comparing the risk estimates for the eight high-temperature indices, the rrs were similar at z =1, but the risk estimates at z=2 were higher for composite high-temperature indices than for single high-temperature indices. compared with the association with mortality, there was a greater variation in relationships between selected high-temperature indices and all-cause outpatient visits (table 4 ). based on aic values, the maximum temperature was the most optimal predictor among associations between outpatient visits and temperatures. the lowest outpatient visit risk was observed at z = 0 in taipei and central taiwan, but at z = − 1 in southern taiwan . thus, these standardized scores were used as reference values for further analyses. at z = 1, the cumulative 8-day relative risks for outpatient visits increased by approximately 7%, 3%, and 4% in taipei, central taiwan and southern taiwan, respectively. at z = 2, the estimated cumulative relative risks for these three areas decreased dramatically and were no longer statistically significant. associations between high-temperature indices and mortality and outpatient visits differ among areas and enable to further compare the capacity of prediction. the index of temperature measurement used in the study is as simple as possible. for example, daily average temperature is a simple indicator that the general population can easily understand. average temperature is the most common measurement used for studying the impact of temperature on health outcomes. however, to account for the changes in temperature perceived by humans, recent studies have introduced comprehensive weather variables as composite high-temperature indices such as hi, at, humidex and wbgt to study the temperature-related health outcomes (anderson and bell, 2009; chung et al., 2009; epstein and moran, 2006; kjellstrom et al., 2009; smoyer-tomic and rainham, 2001) . the present study evaluated whether all-cause mortality and outpatient visits are associated with the eight high-temperature indices in warm seasons for population in a subtropical island. we found that the association may vary by the study area, evaluated health outcomes and selected high-temperature indices. apparent temperature is the most optimal high-temperature index associated with all-cause mortality. however, the eight temperature indices performed similarly in models fitting for predicting all-cause mortality. besides, the maximum temperature is consistently the most optimal high-temperature index for predicting all-cause outpatient visits. temperature indices vary based on demographic and geographic status. a korean study suggested that hi and mean temperature performed comparably for predicting mortality (kim et al., 2006) . a toronto study concluded that humidex and at are both effective for predicting excess mortality associated with hot and humid weather (smoyer-tomic and rainham, 2001) . some research teams have used at as the high-temperature index of interest and have found note: tavg.: daily average temperature; tmax.: daily maximum temperature; tmin.: daily minimum temperature; hi: heat index; thi: temperature humidity index; at: apparent temperature; wbgt: wet-bulb globe temperature; s.d.: standard deviation; and aic represents akaike's information criterion values. ⁎ z score of high-temperature indices for lowest predicted all-cause deaths in loess regression (fig. 2) . ⁎⁎ high-temperature indices' value with lowest mortality risk in dlnm model. ⁎⁎⁎ risk estimated based on reference equals to z = 0 in taipei and central taiwan, and z = − 1 in southern taiwan (supplement figs. 1-3 ). significant association between temperature and mortality (chung et al., 2009 ). on the other hand, a study conducted in new york city showed that maximum hi is a better goodness of fit than maximum, minimum or average temperature in estimating the mortality risk during hot weather (metzger et al., 2009) . a chinese study showed that, based on model fitting, the mean temperature was a better predictor of mortality than maximum and minimum temperatures . yu et al. revealed that mean temperature was an accurate index of all-cause death in brisbane, australia . in contrast, anderson et al. reported that temperature-related mortality assessments did not significantly differ among average, maximum and apparent temperature metrics. they found that the association with apparent temperature is nearly identical to that with the mean daily temperature after controlling for humidity (anderson and bell, 2009 ). vaneckova et al. also found that average temperature and composite high-temperature indices perform similarly in estimating mortality risk (vaneckova et al., 2011) . likewise, all high-temperature indices are significantly associated with mortality in this study because temperature indices are highly correlated with each other. the cumulative mortality risks associated with the composite indices are also relatively similar. in subtropical regions, the consistent high temperature and humidity, and other weather characteristics such as ws and wvp result in a relatively smaller effect on perceived temperature. barnett et al. (2010) have concluded that no high-temperature index can be considered superior to others, because an optimal high-temperature index is also associated with age groups, seasons, and areas analyzed. they suggest selecting high-temperature index based on practical concerns such as the accessibility of climate measurements, public familiarity with the index, and data available (barnett et al., 2010) . in terms of morbidity, some studies have reported that hi is an optimal heat index for predicting inpatient cares and heat-related dispatches (hartz et al., 2012; semenza et al., 1999) . the mean apparent temperature is also an indicator that may well predict hospital admissions for several diseases in nine california counties (green et al., 2010) . however, khalaj et al. found that emergency hospital admissions were more likely correlated with maximum temperature (khalaj et al., 2010) . our study found similar results that maximum temperature is an optimal high-temperature index for predicting heat-related outpatient visits. the weather associated morbidity may be different between clinical visits and emergency room visits. the choice of high-temperature indices may thus produce subtle differences in assessing possible health-related effects of heat. this study also showed that the optimal high-temperature index for predicting mortality is different from predicting outpatient visits. no standard methodology has been developed to evaluate the capacity of high-temperature indices for predicting health effects. a common choice is to measure the change in relative risk of mortality associated with one degree temperature increase or decrease. however, this approach complicates comparisons among different hightemperature indices with different scales and ranges. in this study, we standardize the indices to unify the measurement scale and improve the capacity of prediction. most studies assume a linear association between temperatures and health outcomes, which might not be plausible with practical data (metzger et al., 2009) . armstrong et al. (2011) found that a linear relationship seems to fit well above the threshold temperature without controlling other climate status. although, some evidences have shown non-linearity association as the temperature is above ⁎ z score of high-temperature indices for lowest predicted all-cause outpatient visits in loess regression (fig. 3) . ⁎⁎ high-temperature indices' value with lowest outpatient visit risk in dlnm model. ⁎⁎⁎ risk estimated based on dlnm set as centered value equals to z = 0 in taipei and central taiwan, and z = − 1 in southern taiwan . the thresholds, with quadratic or larger relationships at the highest temperatures. the present study proposed an alternative method to estimate the cumulative rr using dlmn and presented non-linear associations between high temperature indices and mortality, and outpatient visits as well. standardization assures the comparability among various high-temperature indices (armstrong et al., 2011) . the cumulative 8-day rrs of health outcomes vary among high temperatures. in summary, our study observes higher cumulative rrs for mortality than for outpatient visits in association with high temperature. the area-specific rrs of mortality associated with observed and standardized high-temperature indices are clearly non-linear with index values (supplemental figs. 1-3) . the corresponding rrs of outpatient visits are more fluctuated and inconsistent . these findings support the study in england that high temperatures have a larger effect on mortality than on morbidity (kovats et al., 2004) . we found the mortality risk increased dramatically as standardized high-temperature indices increased from z = 1 to 2. nonetheless, the standardized high-temperature indices have higher rrs at z = 1 than at z = 2 for all-cause outpatient visits. a possible explanation is that people who have mild illness may take immediate action in response to remit the symptoms. they may stay in air conditioned environment or drink more fluids against the outdoor high temperature. an island located in a subtropical region, separated from the asian continent, with an area of 144 km wide and 394 km long, the weather in taiwan varied from north to south. therefore, the health risks associated with these high-temperature indices are evaluated only for the population residing in the area-specific environment. studies with similar methodologies are thus suggested for populations located in different climates. in addition, this study also found that the risks associated with heat are significant in taipei and southern taiwan rather than in central taiwan. compared with the other two areas, central taiwan has lower income and higher portion of the elders (directorate-general of budget, accounting and statistics, executive yuan, r.o.c. (taiwan), 2012). however, due to limited detail information for social economics, this study may not conclude any effects related with these factors. interactions among these variables are recommended to assess in future study. moreover, this ecological study focused only on all-cause mortality and outpatient visits. further studies of temperature effects on human physical responses, clinical symptoms of heat exposure, and identification of the most vulnerable groups are needed to establish a comprehensive heat wave warning system in the future. the associations between high temperature and all-cause mortality and outpatient visits varied by region, health outcomes and selected high-temperature indices. apparent temperature is the most optimal among high-temperature indices for predicting all-cause mortality. maximum temperature is highly correlated with all-cause outpatient visits. standardized high-temperature indices provided an effective platform for comparing these indices on heat 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canadian hot weather health-response plan the assessment of sultriness. part i: a temperature-humidity index based on human physiology and clothing science a universal scale of apparent temperature the central weather bureau online information taiwan air quality monitoring network taiwan governmental information office. the republic of china year book 2008: chapter 12. environmental protection do biometeorological indices improve modeling outcomes of heat-related mortality? associating emergency room visits with first and prolonged extreme temperature event in taiwan: a population-based cohort study ambient temperature and morbidity: a review of epidemiological evidence is the association between temperature and mortality modified by age, gender and socio-economic status? the effect of various temperature indicators on different mortality categories in a subtropical city of brisbane we appreciate the authorities of department of health, taiwan national health research institute, taiwan environmental protection administration, and taiwan central weather bureau for providing research data. interpretations and conclusions herein do not represent those of these agencies. dr. fung-chang sung and ted knoy are appreciated for their editorial assistance. this study was supported in part by taiwan national science council (nsc 96-3111-b-033-001, nsc 99-2621-m-039-001 and nsc 99-2221-e-033-052), the china medical university hospital (1ms1), and the taiwan department of health (doh100-td-b-111-004, doh100-td-c-111-005). key: cord-282964-dmc8mlxu authors: wathore, roshan; gupta, ankit; bherwani, hemant; labhasetwar, nitin title: understanding air and water borne transmission and survival of coronavirus: insights and way forward for sars-cov-2 date: 2020-08-04 journal: sci total environ doi: 10.1016/j.scitotenv.2020.141486 sha: doc_id: 282964 cord_uid: dmc8mlxu abstract the ongoing pandemic of coronavirus disease 2019 (covid-19) caused by the severe acute respiratory syndrome coronavirus 2 (sars-cov-2) has resulted in unprecedented disease burden, healthcare costs, and economic impacts worldwide. despite several measures, sars-cov-2 has been extremely impactful due to its extraordinary infection potential mainly through coronavirus-borne saliva respiratory and droplet nuclei of an infected person and its considerable stability on surfaces. although the disease has affected over 180 countries, its extent and control are significantly different across the globe, making it a strong case for exploration of its behavior and dependence across various environmental pathways and its interactions with the virus. this has spurred efforts to characterize the coronavirus and understand the factors impacting its transmission and survival such as aerosols, air quality, meteorology, chemical compositions and characteristics of particles and surfaces, which are directly or indirectly associated with coronaviruses infection spread. nonetheless, many peer-reviewed articles have studied these aspects but mostly in isolation; a complete array of coronavirus survival and transmission from an infected individual through airand water-borne channels and its subsequent intractions with environmental factors, surfaces, particulates and chemicals is not comprehensively explored. particulate matter (pm) is omnipresent with variable concentrations, structures and composition, while most of the surfaces are also covered by pm of different characteristics. learning from the earlier coronavirus studies, including sars and mers, an attempt has been made to understand the survival of sars-cov-2 outside of the host body and discuss the probable air and water-borne transmission routes and its interactions with the outside environment. the present work 1) helps appreciate the role of pm, its chemical constituents and surface characteristics and 2) further identifies gaps in this field and suggests possible domains to work upon for better understanding of transmission and survival of this novel coronavirus. j o u r n a l p r e -p r o o f inanimate surfaces, and other chemicals. chemical composition of these factors is also looked into, which can significantly impact sars-cov-2 survival and transmission. finally, this study outlines probable air and water borne routes and suggest a way forward highlighting the need for investigating the effect of particulate matter characteristics on survival and transmission of sars-cov-2 due to the prominent presence of pm in ambient, spaces, and on the surfaces. hospitals and quarantine centres (institutional and residential) are high-risk environment for nosocomial transmission; data which included information on whether the patient was a healthcare worker in the united states, reported that 19% were healthcare workers (n = 49,370) (cdcmmwr, 2020) compared to 20% for mers and around 21% for sars (mackay and arden, 2015; . these numbers suggest that extra disinfection and preventive measures, as well as precautions, need to be taken in the healthcare facilities to minimize the cross infection, as the staff spends most of their time in close vicinity of the infected patients. outside of the hospital, community transmission can happen through close contact with infected family members or in crowded public spaces (jiaye liu et al., 2020) . community transmission from an asymptomatic carrier is also a possibility (al-tawfiq, 2020; bai et al., 2020; gandhi et al., 2020; kaur et al., 2020; . once inhaled , sars-cov-2 targets a cell-surface receptor called angiotensin-converting enzyme 2 (ace2), which is highly expressed in the respiratory tract, lungs, intestine, kidney, and heart; this pathogenesis mechanism is described in detail elsewhere (docea et al., j o u r n a l p r e -p r o o f (van doremalen et al., 2020) . sars-cov-2 can survive on inanimate surfaces such as printing papers and tissue papers for up to 3 hours, treated-wood for up to 2 days; can last longer on smoother surfaces such as glass and banknotes for up to 4 days, and stainless steel and plastic for up to 7 days. interestingly the virus was detected even after seven days on the outer layer of a surgical mask (chin et al., 2020) . the survival of sars-cov-2 on surfaces is summarized in figure 1 . therefore, fomite transmission would depend on the surface characteristics, which can affect virus survival and can help determine extent of spread of the disease. however, it is not justifiable to consider that these surfaces will always be free from dust and particles, which can have significant impacts on virus survival in addition to inherent surface properties as often studied. these interactions have been explored in section 5. the third mode of probable transmission of coronaviruses is via faeces. a controlled study on aerosolization of faecal waste contaminated with avian influenza virus shows that faecal transmission could be a serious risk for both humans and animals (sedlmaier et al., 2009) . in an earlier study, sars-cov is reported to be stable in faeces at room temperature for a minimum of 1-2 days and can survive for up to 4 days in stool from diarrheal patients (lai et al., 2005) . sars-cov-2 is also detected in faeces raising the possibility of faecal-oral transmission yeo et al., 2020) ; especially during flushing which can aerosolize faecal matter, resulting in airborne transmission (section 2.1) (mcdermott et al., 2020) . such probability of transmission is high in hospital and quarantine centers settings where toilets are shared. flushed water entering into sewerage systems also becomes another carrier medium for this virus. a previous study determined that coronaviruses can survive up to 2-3 days in sewage water and up to 10 days in tap water at 23 °c; factors for survival include temperature, organic matter levels and presence j o u r n a l p r e -p r o o f of antagonistic bacteria and oxidants such as chlorine (gundy et al., 2009) . these aspects of aerosolization through flushing and entry into sewage calls for detailed analysis and focused research in this area. such type of probable routes of transmissions should be thoroughly researched for virus transmission and survival in these mediums as these possibilities may aggravate the problem to community transmissions (heller et al., 2020) . some of the early researches in this area has suggested presence of rna of sars-cov-2 in sewage water , however, the persistence of the virus in water and sewage is yet to be determined (la rosa et al., 2020) . the research studies have highlighted that the air-borne transmission of coronavirus is one of the most potential ways of its infection (morawska and cao, 2020; setti et al., 2020) . the studies have also suggested that intractions of virus laden droplet nuclei can possibly infect an individual in direct contact, however the droplet nuclei (diameter < 5 µm) can become air-borne and travel greater distances compared to respiratory droplets (diameter > 5-10 μm), thereby increasing the zone of spread. ultrafine particles present in ambient air have residence times in the order of days or weeks enabling transport up to thousands of kilometers in the atmosphere, while coarser particles, which are heavier tend to deposit quicker and typically travel less than 10 km from their place of generation. ( although the pm can play a role in harboring microorganisms including coronavirus, the interaction of varied composition of the pm with coronavirus remains unaddressed i.e. transmission and survival of virus on pm with different constituents/compositions, including black carbon and heavy metal particulates etc. on the other hand, exposure to pm levels exceeding the guidelines (for yearly average pm 2.5 and pm 10 exposure is 20 µg/m 3 and 40 µg/m 3 respectively) and will adversely affect the immune system (who, 2018) thus further aggravating not only infection potential of virus but also severity of health impacts. there is substantial evidence of both short-term and chronic exposure to high levels of fine-ultrafine pm and other anthropogenic pollutants being associated with detrimental health effects including exacerbating pre-existing respiratory diseases, by deposited deep inside the lungs, especially pulmonary alveoli (chen et al., 2016) , through a combination of inertial impaction, gravitational sedimentation, and diffusion mechanisms (darquenne, 2014) . inhaled pm 2.5 can get deposited in different compartments in the respiratory tract and interact with epithelial cells and resident immune cells, inducing local or systematic inflammatory responses (wei and tang, 2018) . thus, if the particulates are virus laden, the exposure may worsen the health condition of an individual, by not only infecting a person with covid-19 but could also impact the individual immune system, thereby increasing the viral infectivity, morbidity and mortality, especially in children and adults (pope iii, 2007; li et al., 2016; pope et al., 2018; kirrane et al., 2019; tsatsakis et al., 2020) . apart from air-borne intractions of the virus and pm, these intractions could also frequently happen on the different environmental surfaces, where the coarse pm and virus-laden respiratory nuclei can settle and contaminate surfaces. along with the pm, atmospheric bioaerosols including viruses, fungi, journal pre-proof j o u r n a l p r e -p r o o f bacteria, and algae, whose combination with pm, could be associated with improved virus survivability, possibly promoting the ability of the virus to grow and multiply (turaga et al., 2012) . increased abundance of microbes have been reported during high pm pollution and smog events as compared to clear and sunny days (cao et al., 2014; wei et al., 2016) . now, when such infected surfaces are touched, can act as a path to introduce the virus to an individual by mouth, nose, or eyes. these surfaces can also re-suspend in the virus-laden particulates during high wind turbulence, simultaneously enabling airborne infections. it is also critically essential to investigate and to understand the impact of pm compositional charateristics and morphology on virus survival, which will prominently determine its spread from air and surfaces, as many compounds associated with pm can be toxic to the virus survivability. as a first step, highlighting the need, the presence of heavy metal particulate matter and its interaction with the virus is discussed in subsequent section 4.1. it can be inferred that different pm compositions can have different survivability of the virus and thus, the role of pm aiding the air-borne and surface transmission can't be generalized and present an important subject for further study. there has been a substantial number of recent studies characterizing sars-cov-2 and its association with criteria pollutants and environmental parameters. table 1 summarizes outcomes of selected recent studies, which looked into associations of some of these factors with covid-19 transmission and fatality. from table 1 , it could be inferred that higher temperature, uv radiation and wind speeds are associated with lower risk of covid-19 transmission, although other political/administrative, demographic, environmental and scientific factors will have confounding effects (bherwani et al., 2020a (bherwani et al., , 2020c goumenou et al., 2020) . the effect of humidity on the virus transmission, is not clearly understood and would require more scientific evidence to establish the cause and effect relationships. it is also reported that the effect of environmental factors, will be greatly undermined, the social (physical) distancing is not properly followed (bherwani et al., 2020b; gupta et al., 2020) . studies looking into both short-and long-term exposure to criteria pollutants found confirmed associations of pollution levels with covid-19 spread or fatalities, with higher levels resulting in increased fatalities. this could be mainly due to the health impacts of such pollutants, which would make the people more vulnerable to covid-19 infection and may not be actually considering the stability of the virus on polluted surfaces, especially with respect to pm composition. interestingly, short-term exposure to a higher concentrations of so 2 is associated with decreased risk of covid-19 infection (y. , thereby further strengthening and testifying the present hypothesis that atmospheric chemistry and pm characteristics can significantly affect virus survival as this can play a vital role in the spread of disease through both most potential modes of transmissions, i.e. airborne and fomite. studies on virus survival and interaction with different surfaces and chemicals have also been reported in an effort to better understand sars-cov-2 survival characteristics. metal ions play an important role in the survival of viruses. mg, zn, and cu are some of the metal ions that can bind to virus proteins and can be part of rna and dna processes (tunde et al., 2020) . derivatives of bismuth have shown to efficiently inhibit the growth of sars-cov . zinc antiviral properties of essential oils and their components have been well documented and studies have demonstrated substantial inhibition of different strains of the influenza virus, dengue virus, and others (nerio et al., 2010; raut and karuppayil, 2014) . more recently, a study showed that organosulfur hence, pm plays a multifaceted role of providing surfaces for pathogen transmission and interaction, enabling fomite transmission by deposition, as well as chronic weakening of the immune and respiratory system, making the virus more potent in regions with higher pm levels. its omnipresence in the atmosphere and on surfaces (due to deposition), makes it an important subject for further study to understand the impact of pm composition on virus survival, which will prominently determine its spread from surfaces rather than the only type of surfaces as studied so far. further, the chemical composition and mass concentrations of pm is highly variable and dependent on journal pre-proof j o u r n a l p r e -p r o o f local geography, meteorology, seasonal patterns and sources of emissions such as traffic, re-suspended dust, industrial, residential, biomass burning, natural and other sources (karagulian et al., 2015) . sars-cov-2 (diameter 60-140 nm) can attach itself to pm components such as dust or marine organic aggregates and eventually deposit (sanità di toppi et al., 2020) . some of the constituents of pm which may interact with these viruses are compiled in table 2 . this lack of above information prevents complete understanding on the stability of coronavirus on pm and pm-contaminated common surfaces. these particles are almost omnipresent and can significantly influence the interaction of viruses with different surfaces studied so far, as often these surfaces are not completely clean in real world conditions. this certainly presents a very complex matrix to be explored, however considering its presence in spaces and atmosphere, such investigations will be of great influence of meteorological factors and air pollution on the outbreak of severe acute respiratory syndrome inhalable microorganisms in beijing's pm 2.5 and pm 10 pollutants during a severe smog event characteristics of health 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world should face the reality size distribution and sites of origin of droplets expelled from the human respiratory tract during expiratory activities learning from the past: possible urgent prevention and treatment options for severe acute respiratory infections caused by repellent activity of essential oils: a review assessing nitrogen dioxide (no2) levels as a contributing factor to coronavirus review of synthetic human faeces and faecal sludge for sanitation and wastewater research mortality risk and pm 2.5 air pollution in the usa: an analysis of a national prospective cohort mortality effects of longer term exposures to fine particulate air pollution: review of recent epidemiological evidence a status review on the medicinal properties of essential oils deposition rates of viruses and bacteria above the atmospheric boundary layer the characterization of feces and urine: a review of the literature to inform advanced treatment technology dual role of organosulfur compounds in 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interventions for covid-19. front correlation between weather and covid-19 pandemic in jakarta covid-19, an opportunity to reevaluate the correlation between long-term effects of anthropogenic pollutants on viral epidemic/pandemic events and prevalence. food and chemical toxicology 111418 metal ions complexes and viral pathogenicity 12 -advances in materials for chemical, biological, radiological and nuclear (cbrn) protective clothing aerosol and surface stability of sars-cov-2 as compared with sars-cov-1 high temperature and high humidity reduce the transmission of covid-19 reasons for healthcare workers becoming infected with novel coronavirus disease 2019 (covid-19) in china detection of sars-cov-2 in different types of clinical specimens unique epidemiological and clinical features of the emerging 2019 novel coronavirus pneumonia (covid-19) implicate special control measures ambient bioaerosol particle dynamics observed during haze and sunny days in beijing biological effects of airborne fine particulate matter (pm 2.5 ) exposure on pulmonary immune system relationship between the covid-19 outbreak and temperature, humidity, and solar radiation across china mers-cov | epidemic and pandemic diseases mers-cov | epidemic and pandemic diseases modes of transmission of virus causing covid-19: implications for ipc precaution recommendations health risks of particulate matter from long-range transboundary air pollution. world health organization, regional office for europe who | summary of probable sars cases with onset of illness from 1 exposure to air pollution and covid-19 mortality in the united states (preprint) effects of temperature and humidity on the daily new cases and new deaths of covid-19 in 166 countries association between ambient temperature and covid-19 infection in 122 cities from china human transmitted human coronaviruses: sars-cov-2 and sars-cov. viruses characteristics of pediatric sars-cov-2 infection and potential evidence for persistent fecal viral shedding bismuth complexes inhibit the sars coronavirus particulate matter components and health: a literature review on exposure assessment enteric involvement of coronaviruses: is faecal-oral transmission of sars-cov-2 possible? covid-19 pathophysiology: a review a novel coronavirus from patients with pneumonia in china association between short-term exposure to air pollution and covid-19 infection: evidence from china key: cord-265715-u8rc48f4 authors: ishaq, sadia; sadiq, rehan; farooq, shaukat; chhipi-shrestha, gyan; hewage, kasun title: investigating the public health risks of low impact development at residential, neighbourhood, and municipal levels date: 2020-07-06 journal: sci total environ doi: 10.1016/j.scitotenv.2020.140778 sha: doc_id: 265715 cord_uid: u8rc48f4 abstract low impact developments (lids) employ a series of vegetative techniques to retain rainfall close to the origin. although lids offer sustainable runoff management, these infrastructures can be considered a risk to public health due to the presence of pathogens in the runoff and human exposure to contaminated water held in and transported by lids. the objective of this study is to examine the disease burden from exposure to lids at the residential, neighbourhood, and municipal levels. the authors conducted a meta-analysis of literature on three water features: (1) harvested rainwater obtained from lids, (2) surface water, and (3) floodwater. a set of 32 studies were systematically selected to collect values of risks of infection and expressed as the disease burden, i.e. disability adjusted life years (dalys). the results showed that the percentage of gi illness exceeding the health guidelines were high for harvested rainwater, i.e. 22% of annual disease burden exceeded the who guidelines (0.001 dalys/1000 persons), and 2% exceeded the us epa guidelines (5.75 dalys/1000 bathers). among the six exposures for harvested rainwater, exposure to spray irrigation, exceeded us epa guidelines whereas; five exposures, i.e. flushing, hosing, daily shower, spray irrigation, and children playing, surpassed the who guidelines. considering lid treatment, the values of annual disease burden from all the selected barriers were below us epa guidelines however, these values exceeded the who guidelines for three barriers i.e. water plaza, grass swale, and open storage ponds. these findings provide a broader perspective of the disease burden associated with lids and emphasise to consider the type of exposures and required treatment barriers for developing lid infrastructures in urban areas. j o u r n a l p r e -p r o o f requires consideration and management of human exposure to runoff water and reducing public health risks. the presence of pathogenic microorganisms in runoff water has been well documented (albrechtsen h. j., 2002; sakamoto et al., 2009; selvakumar and borst, 2006; sidhu et al., 2012; van heijnsbergen et al., 2014) . these pathogens entering the water system belong to various sources such as animal waste, (un)treated sewage, and solid waste mixing with rainwater when it flows over the urban surfaces (arnone and walling, 2007; hofstra et al., 2011) . exposure to water-borne pathogens during domestic use of water and recreational activities can cause mild health problems (e.g. gastrointestinal, respiratory, skin, ear, and eye infection) or more severe conditions (e.g. hepatitis and meningitis) (white et al., 2010) . the occurrence of health problems incur economic burden in terms of lost productivity, visits to healthcare, hospitalization, sequelae, and mortality. for example, in the us, recreational water-borne illness is estimated to cost a substantial economic burden of approximately usd 2.9 billion/year (deflorio-barker et al., 2018) . since lids are meant to store and transport runoff water, the presence of pathogenic microbes can influence the risk of infection and investigations are needed to compare human exposure versus occurrence of disease and identify critical factors. a substantial amount of research shows the ability of water-borne pathogens to survive on leafy greens and enter the human body during consumption (dicaprio et al., 2012; esseili et al., 2012; ethelberg et al., 2010; hirneisen and kniel, 2013; warriner et al., 2003) . for example, zoonotic pathogens can persist and internalize leaves of lettuce or spinach foliage due to protection from solar irradiation and desiccation (markland, 2015) . similarly, leguminous tree and bryophytes are associated with a large number of facultative human pathogens, including staphylococcus, salmonella, and j o u r n a l p r e -p r o o f 6 residential and neighbourhood levels. surface water includes urban tributaries, rivers, and lakes, which receive runoff and are mainly used for recreational purposes (lim et al., 2015) . floods include rainfallgenerated surface runoff, and/or from the flooded storm sewers, which contain a variety of microbial pathogens and pose risks to public health. the process of systematic review started with the identification of scientific literature on qmra modeling of runoff water flowing through lids, surface water, and floods. for this purpose, a systematic literature search was performed using four electronic databases including science direct, pubmed, engineering village, and google scholar. the combinations of keywords used in this search included the following: "runoff"/"rainwater"/"surface water"/"stormwater"/"floods" and "low impact development"/"green infrastructure"/"water sensitive urban design" and "quantitative microbial risk assessment"/"public health risk"/" disease burden". to identify additional records, initially identified articles were searched for forward/reverse citation. all original articles referenced in reviews were retrieved including qmra of water sensitive urban design (wsud) and green infrastructure. the initial identification of articles was followed by the removal of duplicate records. the screening of articles was performed to determine the eligibility of the articles as per inclusion-exclusion criteria (table 1 s; supplementary document -s2). the titles and abstracts of identified articles were reviewed for the selection of relevant records and, full-text pdfs were obtained for those articles, formatted with adobe acrobat x pro® for text recognition. the selected articles were imported into mendeley library to further proceed with the data extraction and analysis. the key output of this systematic review was a collection of peer-reviewed literature on qmra modeling of runoff water flowing through j o u r n a l p r e -p r o o f 7 from each of the selected studies, the data on risk of infection estimated via qmra modeling was extracted by a single reviewer. in the context of this research, the details of qmra steps are as follows. the health hazards are the water-borne pathogens i.e. virus, bacteria, and protozoa, present in urban runoff; lid infrastructures e.g. rain barrels, grass swales, biofilters; surface water; and floodwater (step 1). during exposure assessment (step 2), all processes of human-water interaction are quantitatively described through the estimation of concentration of pathogens, volume of water ingested/inhaled, and annual exposure frequency (ahmed et al., 2010) . once an episode of humanwater interaction occurs at any of the selected water features, water-borne pathogens transmit into human body via mouth, nose, and/or skin and may cause an infection. in the case of harvested rainwater at residential level, human-water interaction may occur when rainwater is reused during irrigation and non-potable activities, such as toilet flushing, showering, etc. regarding surface water, human-water interaction occurs via primary and/or secondary contact activities. primary contact activities indicate that the whole body is submerged in water (e.g. swimming, bathing, diving, water skiing, etc.) and secondary contact activities indicate that only limbs of an individual is exposed to water (e.g. boating, rowing, fishing, sailing, etc.) (dorevitch et al., 2012) . in dose-response assessment (step 3), mathematical models specific to the type of pathogen are used to calculate the probability of infection (chhipi-shrestha et al., 2017) . this research covered the complete suite of water-borne pathogens responsible for gi infection and the relevant equations for estimating the probability of infection are beta-poisson (eq. 1) and exponential (eq. 2) dose-response models. lastly, risk characterisation (step 4) involves the integration of exposure assessment and dose-response assessment for a specific pathogen and exposure route. typically, the risk of infection is measured for a single-event (p inf ), followed by the estimation of annual risk (p inf(a) ) over a period of one year by using an annual exposure frequency for the exposure activity under consideration (eq. campylobacter, and salmonella (haas et al., 1999) . exponential dose-response model used for adenovirus (vergara et al., 2016) , norovirus (schmidt, 2015) , and cryptosporidium and giardia (robertson et al., 2005) . where p inf represents probability of infection to an individual exposed to a single pathogen dose "d"; d is the pathogen dose; p inf(a) refers to annual probability of infection from "n" exposures/ year due to a single pathogen dose "d"; "α" and "r" are parameters referring to pathogen infectivity constant which characterise dose-response relationships; n 50 is the median infective dose, i.e., the dose required to infect 50% of the exposed population. following data extraction, geometric mean was calculated to estimate central tendency if the data on risk of infection were available as a set of more than one value. in addition to the risk of infection values, the record of review included the details of location of the study, water feature, sampling site, pathogen prevalence, detection method, recovery efficiency, pathogen concentration, exposure assessment, and dose-response model. based on the estimation of annual risk of infection, the annual risk of illness (p ill ) and disease burden (daly) were calculated as follows (eq.4 and 5): j o u r n a l p r e -p r o o f 9 where p ill|inf refers to risk of disease given infection, i.e., morbidity. for the purpose of standardisation, the data were expressed as the burden of disease i.e. daly (eq. 4 and 5). daly is the estimation of the number of healthy years lost due to disease or early death of an individual; a disease with higher values of dalys indicates unhealthy impacts whereas lower values of dalys are beneficial for population health (murray and lopez, 1996) . in this research, the risk is expressed in units of dalys/1000 persons/year. this unit provides an estimate of the risk of illness or disease cases for a population of 1000 individuals in a year and offers a more accurate comparison of the disease cases and health targets. often, the incidence of infection has been considered as the assessment endpoint of risk but, it may lead to over or underestimation of health risk. to overcome this discrepancy, dalys measurement was used to represent the health risks from exposure to lids or related infrastructures. the conversion of risk of infection into dalys requires three conversion factors, i.e. annual exposure frequency, infection to illness ratio, and dalys loss per disease case (table s2 ; supplementary document-s2). the values of these conversion factors were obtained from the literature as given in supplementary document-s2 (table s3 , s4 and s5, respectively). for the purpose of analysis, the health risks from exposure to surface water during primary (e.g. swimming, bathing) and secondary (e.g. rowing, sailing) recreations were assumed comparable to lids present in neighbourhoods and municipalities in terms of water quality, exposure type, and pathogen. the data were analyzed for the disease burden exceeding the health targets, most critical pathogens, water features, exposure activity, and age groups. two widely recognised health risk guidelines were used to examine the risk assessment outcomes, which includes 1) the acceptable disability-adjusted life the current research presents an attempt of examining the public health risks associated with lids at three levels i.e. residential, neighbourhood, and municipal. at the residential level, the use of cisterns and rain tanks is a common practice to overcome water scarcity in many parts of the world such as australia, pakistan, and india. similarly, in urban communities, the development of grass swales, permeable pavement, and retention ponds are considered a sustainable solution to manage rainfall and runoff close to the site of origin thus reducing pollutant loading and stormwater quantity in the drainage system (fletcher et al., 2015) . the water management benefits of lids are well recognised, but the assessments of public health risks associated with these infrastructures are scarce. water-borne pathogens are an increasing public health concern and substantial research is available on quality management of drinking water and wastewater treatment systems. this study builds upon the previous work to determine whether or not the health risks from exposure to lids during recreational and nonpotable activities meet public health guidelines of the who and us epa. a summary of the results from a systematic review are given in tables 1 and 2 for 1) harvested rainwater, 2) surface water, and 3) floodwater). the information on geographical location of the articles included in this review is shown in table 1 . the data on risk of infection and burden of disease were collected from 32 articles ( j o u r n a l p r e -p r o o f 11 data were most abundant for cryptosporidium (n=12), followed by giardia (n= 9), and norovirus (n= 6). regarding floodwater, the data were obtained from five articles and, qmra analysis was mostly performed for cryptosporidium and campylobacter (n=4 for each of these pathogens), followed by giardia (n= 2). table 1 here>> << please insert table 2 here>> the comparison of cumulative probability of exceedance and the annual burden of disease from exposure to the selected water features is shown in fig. 2 . in general, the percentage of diarrheal illness exceeding the two guidelines was highest for floodwater exposures, followed by recreational exposure in surface water, and non-potable exposures to harvested rainwater. in the case of harvested rainwater, almost 22% of annualised disease burden exceeded the who (0.001 dalys/1000 persons), and approximately 2% exceeded the us epa guidelines (5.75 dalys/1000 bathers). the results of surface water revealed that the percentage of exceedance for recreational activities in surface water was considerably high, surpassing the who guidelines up to 73% of the time and us epa guidelines up to 12.3% of the time. considering floodwater, the probability of exceeding the two health guidelines was significantly high, and approximately 87% of the dataset exceeded the who guidelines and 22.5% exceeded the us epa guidelines. these findings support the fact that microbial contamination is more pronounced in floodwater and so is the likelihood of gi illness during wet weather, thus the burden of gi illness or diarrheal problems needs to be considered while developing lids in urban settings. previous studies have confirmed that microbial contamination of floodwater far exceeded the acceptable levels as given in guidelines pertaining to microbial quality of recreational water (xiao et al., 2013) whereas, the harvested rainwater was reported to exhibit a lower level of microbial contamination that lies below the health guidelines (ahmed et al., 2010) . floodwater impacted by j o u r n a l p r e -p r o o f animal waste and human sewage exhibited the highest likelihood of gi illness during withdrawal and the clean-up of contaminated water (fewtrell et al., 2011) . similarly, surface water bodies were reported to receive a high concentration of water-borne pathogens from (un)treated sewage, defecation from animals, sewer overflows which could lead to the widespread occurrence of gi illness during recreational activities (ahmed et al., 2005; gannon and busse, 1989; lechevallier et al., 1998; noble et al., 2006; rajal et al., 2007) . in contrast, harvested rainwater was recorded to be less polluted as the sources of microbial pollution included bird/insects droppings, leaves in the gutter, and condition of the roof, piping, and storage (brodie et al., 2007; evans et al., 2006; huston et al., 2009; lye, 2009 ). the analysis of data of floodwater and surface water presented a worst-case scenario of the disease burden of gi illness, and harvested rainwater depicted the situation of least contamination of runoff water leading to less burden of gi illness. it is important to note that these results do not provide an exact measure of the burden of gi illness from lids. however, broadly, one can infer that the development of lids may negatively affect public health in urban neighborhoods. this study covered the complete suite of pathogens that were examined in the selected literature and can cause gi illness and legionellosis. figure 3 summarises the total annual burden disease of water-borne pathogens from exposure to the selected water features. from exposure to harvested rainwater, the total annual burden of disease, the sum of annual disease burden from each pathogen, was 67.72 dalys/1000 persons. the pathogen with the highest burden was adenovirus, with an estimated value of 48.69 dalys/1000 persons/year, followed by campylobacter, and rotavirus. these three top-ranking pathogens accounted for 96% of the disease burden when harvested rainwater was used for non-potable activities (fig. 3a) . j o u r n a l p r e -p r o o f 13 considering surface water, the total annual burden of water-borne pathogens from exposure to this water feature was 448.9 dalys/1000 persons. the pathogen with the highest burden was giardia, with an estimated annual value of 89.1 dalys/1000 persons, followed by adenovirus, and cryptosporidium. these three top-ranking pathogens accounted for 51.2% of gi illnesses when the population was exposed to surface water through primary or secondary contact recreational activities (fig. 3b ). regarding floodwater, the total annual disease burden from water-borne pathogens was alarmingly high, i.e., 980.2 dalys/1000 persons. the pathogen with the highest burden was virus, having an estimated value of 804.9 dalys/1000 persons, followed by cryptosporidium, and campylobacter. these three top-ranking pathogens accounted for 95.2% of the disease burden of water-borne diseases when the population was exposed to urban floods during clean-up and withdrawal of contaminated water (fig. 3c) . overall, it is found that the total annual burden of disease for water-borne pathogens vary greatly across the three water features. another important finding was that the total annual disease burden was highest for the viral pathogens, followed by protozoal and bacterial pathogens (fig. 3) . these << please insert fig. 3 here>> the comparison of disease burden at individual and population level is given in fig. 4 . for the pathogens examined within the selected water features, rotavirus stood out for having a high impact on individual health, whereas, two bacterial pathogens, campylobacter and salmonella, were identified to have a high impact on population health. overall, viruses make a large contribution to the disease burden at the individual and population level in the selected water features. for prevention-orientated management of water-borne diseases from these water features, intervention strategies must focus to manage risks from viruses, cryptosporidium, and giardia. for harvested rainwater at the residential level, the results of annual disease burden in relation to exposure activity and pathogens are presented in figure 5 . at this level, the analysis of six activities showed that the disease burden from all the exposures were below us epa guidelines ( considering lid treatment train in the neighborhood, the value of annual disease burden was below the us epa guidelines for the selected treatment barriers but, it exceeded the who guideline for three lid barriers i.e. water plaza, grass swale, and open storage ponds (fig. 7) (an analysis of annual disease burden in relation to lid treatment train, water-borne pathogens, and exposure activity is given in fig. 1 s; supplementary document s1). these treatment lid barriers provide desirable habitat to birds and animals, which leads to contamination of water and infects the local population (ahmed et al., 2010; petterson et al., 2016) . on the other hand, the rainwater from biofilters met the who guidelines for use in toilets, showering, and crop irrigation (fig. 7) . toilet flushing using non-potable water is a common practice in many parts of the world. generally, it involves aerosolisation of human waste and vomitus and limited human-water interaction makes the use of harvested rainwater safe in toilet flushing. similarly, the disease burden of cold shower was far below the acceptable level of who guidelines. but, the social acceptance of using harvested rainwater for showering is argued due to close contact of water with the human body. since rainwater flowing in neighbourhoods may contain a high concentration of zoonotic fecal and human fecal pathogens, appropriate treatment of water depending on the level of contamination is recommended before using for showering or other activities that involve close human-water interaction. fig. 7 here>> j o u r n a l p r e -p r o o f 17 i.e. playing in water, jump, and fall ( fig. 8 ) (an analysis of surface water annual disease burden in relation to water-borne pathogens and exposure activity is given in fig. 2 s; supplementary document s1). these high values of disease burden can be attributed to the level of contamination, volume of ingested water during these contacts, exposure duration, and exposure frequency. considering floodwater, the disease burden from one exposure activity, residents' withdrawal of floodwater, surpassed us epa guidelines. the median values of disease burden from water splash were below who guideline whereas, these values for three exposures were above this guideline and included floods clean-ups, splash and play, and playing in floodwater ( fig. 9 ) (an analysis of flood-based annual disease burden from flood water in relation to water-borne pathogens and exposure activity is given in fig. 2 s; supplementary document s1). these findings were similar to the previously observed trends in surface water and can be associated with the high microbial concentration of floodwater and longer exposure duration of these activities. overall, the burden of gi illness in relation to age groups and three water features has shown unevenness. the inconsistency of results for the surface water and floodwater can be attributed to the lack of data as number of data points for children was less than adults in these two water features. considering adult population, the likelihood of developing sequelae or death is higher at old ages (dumic et al., 2019) . also, the disease burden of immune-compromised population cannot be neglected. further research on the role of lids in developing gi infection among these groups would be beneficial for appropriate stormwater management. fig. 10 here>> this research aimed to analyze the burden of respiratory illness from legionella. there was a lack of information and data on the risk of legionellosis from exposure to selected water features. only a few data points were available from previous studies on harvested rainwater, and this discrepancy limited scientific understanding of legionellosis from exposure to lids and related infrastructures. from the available literature, the risk of legionellosis was reported from three exposure activities i.e. daily showering, hose irrigation, and children play in water plaza ( fig. 5 and 6 ). these three activities are related to the generation of aerosols and inhalation of contaminated droplets that may cause respiratory infection. overall, the burden of disease from legionella seems to be low but the unavailability of dataset impedes an in-depth understanding of the burden of legionellosis. more research is necessary to draw any conclusion about the burden of legionellosis for the population exposed to lids in urban neighbourhoods. journal pre-proof j o u r n a l p r e -p r o o f the use of lids is becoming increasingly popular in urban stormwater management. considering the water management benefits of lids, in many developed countries, stormwater management guidelines urge the development of lids for quantity and quality management of urban runoff. for example, the stormwater planning guidelines of british columbia, canada, state that total runoff volume should be 10% of rainfall and 90% must be returned to the natural hydrological cycle through percolation, evapotranspiration, and reuse (finnie et al., 2002) . this means permeable cover should be 90% of the total watershed area. the availability of large amount of green spaces in urban settings combined with increased water retention would possibly offer the most suitable habitat to water-borne pathogens, thus increasing the risk of gi infection and subsequent disease burden. in rotterdam, the netherlands, sales-ortells & medema (2015) reported the campylobacter disease burden of 0.00041 dalys pppy (i.e. 0.258 pppy) for kids playing in water plaza (an infrastructure that combines the storage of runoff with water recreational activities). in another study, nguyen et al., (2017) reported the campylobacter disease burden of 0.0008 dalys pppy for children playing in floodwater. based on these estimates, the authors assumed that during the rainy season, the disease burden of gi illness from exposure to a lid treatment train at neighbour level (i.e. green play areas, grass swales, interactive fountains, retention ponds) for all pathogens could be approximately 50% of the disease burden from floods. considering this assumption, figure 11 shows the annual disease burden of gi illness for children from exposure to neighbor level lids treatment train and expected probability of exceedance for gi illness against who and us epa guidelines. the plot revealed that the percentage of exceedance was considerably high, i.e. 90.9%, for who guidelines whereas, us epa guidelines was met all the time. therefore, it can be deduced that the development of lids in urban communities is associated with the likelihood of gi infections and people exposed to these infrastructures may suffer water-borne gi illness. this research is the first attempt to estimate the disease burden of gi illness and legionellosis from exposure to lids at the residential, neighbourhood, and municipal levels. the authors adopted a meta-analysis methodology and estimated the public health risks of these infrastructures. the review of literature showed a dearth of qmra modeling for lids at neighbourhood and municipal levels, which was overcome by including surface water and floods from rains in the review process. however, understanding the risk of infection associated with lids at these two levels is necessary to obtain insights into the disease burden experienced by the exposed population. this study establishes the conceptual foundation of the effects of lids on public health and presents a wider perspective of the disease burden from exposure to lids. the results revealed that the probability of gi illness exceeding the who and us epa guidelines was highest for floodwater, followed by recreation in surface water, and non-potable exposures to harvested rainwater. among the various microbes, the most critical pathogens of concern were adenovirus, cryptosporidium, campylobacter, and giardia. considering exposure activity, the most critical exposures of concern were hosing and spray irrigation from harvested rainwater at residential and neighbourhood levels. considering lid treatment train in the neighbourhood, the estimated disease burden met the us epa guideline for the selected treatment barriers, but it exceeded the who guideline for three lid treatment alternatives, i.e. water plaza, grass swale, and open storage ponds. within the different population groups, it was found that children could ingest a larger amount of contaminated water and suffer more severe illness from exposure to harvested rainwater. moreover, the likelihood of developing sequelae or death is also an important concern, particularly in elderly and immune-compromised individuals. when designing j o u r n a l p r e -p r o o f 22 future lid in the urban neighborhood, it is recommended to consider the type of exposure activity and lid treatment train. in future work, this research can be extended to assess the safety of these infrastructures in urban areas using modeling tools. in the long-term, an assessment of the disease burden from exposure to lids under the conditions of climate change is important to identify best practices that help to reduce negative health impacts. respectively. the horizontal lines identify the exceedance rate for these two guidelines. legend'a' describes exposure activities and legend'b' describes lid treatments. evidence of septic system failure determined by a bacterial biochemical fingerprinting method health risk from the use of roof-harvested rainwater in southeast queensland, australia, as potable or nonpotable water, determined using quantitative microbial risk assessment † microbiological investigations of rainwater and graywater collected for toilet flushing waterborne pathogens in urban watersheds urban aerosols harbor diverse and dynamic bacterial populations microbial quality of 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of this content analysis. key: cord-304925-9gvx3swf authors: xie, zhixiang; qin, yaochen; li, yang; shen, wei; zheng, zhicheng; liu, shirui title: spatial and temporal differentiation of covid-19 epidemic spread in mainland china and its influencing factors date: 2020-07-14 journal: sci total environ doi: 10.1016/j.scitotenv.2020.140929 sha: doc_id: 304925 cord_uid: 9gvx3swf abstract this paper uses the exploratory spatial data analysis and the geodetector method to analyze the spatial and temporal differentiation characteristics and the influencing factors of the covid-19 (corona virus disease 2019) epidemic spread in mainland china based on the cumulative confirmed cases, average temperature, and socio-economic data. the results show that: (1) the epidemic spread rapidly from january 24 to february 20, 2020, and the distribution of the epidemic areas tended to be stable over time. the epidemic spread rate in hubei province, in its surrounding, and in some economically developed cities was higher, while that in western part of china and in remote areas of central and eastern china was lower. (2) the global and local spatial correlation characteristics of the epidemic distribution present a positive correlation. specifically, the global spatial correlation characteristics experienced a change process from agglomeration to decentralization. the local spatial correlation characteristics were mainly composed of the‘high-high’ and ‘low-low’ clustering types, and the situation of the contiguous layout was very significant. (3) the population inflow from wuhan and the strength of economic connection were the main factors affecting the epidemic spread, together with the population distribution, transport accessibility, average temperature, and medical facilities, which affected the epidemic spread to varying degrees. (4) the detection factors interacted mainly through the mutual enhancement and nonlinear enhancement, and their influence on the epidemic spread rate exceeded that of single factors. besides, each detection factor has an interval range that is conducive to the epidemic spread. j o u r n a l p r e -p r o o f total of 116 countries or regions in the world appeared to be hit by the covid-19 epidemic, and more than 130,000 people have been diagnosed. with the continuous spread of the covid-19 epidemic, several countries or regions of the world have been forced to take emergency measures such as closing cities, stopping production, suspending school classes, and restricting population movement, causing great harm to economic development and residents' health (an and jia, 2020) . therefore, it has become an urgent scientific problem to grasp the spatial and temporal changes of the covid-19 epidemic spread, and clarify the driving mechanism. since the outbreak of covid-19 epidemic, scholars have carried out abundant studies on the epidemic spread and achieved fruitful research results, which are of great guiding significance for the prevention and control of the epidemic. joseph et al. (2020) estimated the size of the epidemic by using a mathematical model based on the data of confirmed cases of covid-19 and residents' travel (including via trains, planes, and roads), and concluded that about 75,815 people were infected in the wuhan city during the early outbreak stage of the epidemic. david et al. (2020) compared covid-19 with other viruses, claiming that a sustained epidemic would pose a serious threat to global health, and proposing that the goal of sustainable development could be achieved by building a human-environment-animal health alliance. liu et al. (2020a) used the exponential growth and maximum likelihood estimation method to determine the transmission dynamics of covid-19 in wuhan, and found that the average incubation period of the virus was 4.8 days, and the basic regeneration index reached 2.90 (95% confidence interval (ci): 2.32-3.63) and 2.92 (95% ci: 2.28-3.67). ai et al. (2020) used the statistical analysis method to investigate the impact of lockdown measures in wuhan (january 23, 2020) on the covid-19 epidemic spread in other parts of china. they claim that if the closure j o u r n a l p r e -p r o o f measures were implemented 2 days in advance, it could have been possible to effectively prevent from being infected of 1,420 people, if the city was closed 2 days later, there would have been 1,462 more infections. bai et al. (2020) used the transmission dynamics model to describe the evolution rule of the epidemic based on the data of confirmed covid-19 cases in the shaanxi province, revealed that the high incidence areas were mainly located in xi 'an, ankang, and hanzhong, and that the outbreak peak period was in early february 2020, with the basic regeneration index of the epidemic spread reaching 2.95. wang et al. (2020a) used the spearman correlation analysis method to find the relationship between the incidence of covid-19 and the baidu migration index in guangdong province, and found that there was a positive correlation between the daily incidence and the 3-day migration index. wang et al. (2020b) used the complex network model to explore the impact of resuming work in surrounding cities on the epidemic situation in hubei province on february 17, february 24, and march 2, and came to a conclusion that resuming work on march 2 would not cause a second outbreak of the epidemic. yan et al. (2020) predicted the trend of the covid-19 epidemic by building a time-delay dynamics model, and claimed that the epidemic could be controlled in the short period if the prevention and control efforts were kept unchanged. chen and cao (2020) made an epidemiological analysis of the daily confirmed cases in china, affirming that the situation of epidemic prevention and control in china was severe, and that targeted control measures should be formulated for the returning of enterprises and personnel in the future. liu et al. (2020b) analyzed the spatial and temporal characteristics of the epidemic spread in guangdong province, and found that the prevention and control measures adopted were effective, and high-risk areas were located in economically developed areas. liu et al. (2020c) used the statistical analysis method to analyze the temporal and spatial j o u r n a l p r e -p r o o f characteristics and the transmission path of the covid-19 epidemic in zhuhai, revealing that the input from the epidemic area and family gatherings were the causes of epidemic spread. the research report published by the yellow river civilization (ai et al., 2020; wang et al., 2020b) . although some scholars try to reveal the epidemic spread rules from a geographical perspective, they mainly focus on the spatial and temporal evolution characteristics of the epidemic, and seldom discuss the driving causes of the epidemic spread (liu et al., 2020c) . (2) in terms of research methods, current studies employ mainly the correlation analyses and regression analyses method, while the application of modern information technology and spatial analysis method are relatively limited (wang et al., 2020a) . (3) in terms of research scale, scholars generally investigate the epidemic spread characteristics at the city or regional scale, and there are few studies at the national level (liu et al., 2020b; liu et al., 2020b) . (4) in relation to data sources, the data of covid-19 cases can be obtained very easily; however, there are great difficulties in obtaining environmental and socio-economic data related to the epidemic spread, which is why current researches lag behind in the driving j o u r n a l p r e -p r o o f mechanism of epidemic spread. in this paper, the number of confirmed covid-19 cases in mainland china was taken as the measurement index, and the spatial and temporal differentiation of the epidemic spread were described by the exploratory spatial data analysis method. then, the key factors affecting the covid-19 epidemic spread were identified by using the geodetector method, so as to provide references for clarifying the epidemic spread rule, formulating some protection policies, and promoting the resumption of work and production. the basic research objects of this paper are the administrative units at prefecturebaidu migration data in the paper is from january 11 to 23, 2020, specifically referring to the top 100 cities toward which people move out of wuhan every day. the winter average temperature data for each unit are from the weather network (https://www.tianqi.com). in addition, since it is impossible to obtain data on the population, gross domestic product, and number of beds in medical institutions for each region during the covid-19 epidemic period, this paper employs the corresponding data in 2018, which is derived from the 2019 provincial statistical yearbooks or the 2018 statistical bulletins. using the cumulative number of covid-19 cases as an indicator to measure the epidemic spread rate is biased due to the large differences in base population for different regions of mainland china. therefore, the cumulative number of covid-19 cases was divided by the number of days to calculate the epidemic spread rate, using the following formula: where v i represents the epidemic spread rate in region i; s i represents the cumulative number of covid-19 cases in region i by february 20; m represents february 20; and n i represents the date of the first confirmed case in region i. j o u r n a l p r e -p r o o f the exploratory spatial data analysis method was used to verify whether the observed value of a unit has spatial correlation with the observed values of its neighboring units (li et al., 2018) . the global moran's i index is used to measure the global spatial correlation, while the local moran's i index in lisa (local indicators of spatial association) was used to measure the local spatial correlation (rong et al., 2016) . their formulas (anselin, 1995; gallo and ertur, 2003) are as follows: where i is the global moran's i index; x i and x j are the observed values of unit i and j; w ij is the spatial weight matrix (with 1 as adjacent, and 0 as non-adjacent), s 2 represents the variance; k represents the number of observation units; i* is the local moran's i index; w pq is the normalized form of the spatial weight matrix; and z p , z q are the normalized forms of the observed values in unit p and q. spatial differentiation is a basic characteristic of geographical phenomena, the geodetector method can measure the degree of spatial stratified heterogeneity and test its significance, through the within-strata variance less than the between strata variance . the geodetector method comprises four modules: factor detection, interaction detection, risk detection and ecological detection. the factor detection is expressed by q value (wang and xu, 2017) , its formulas are as follows: where q represents the explanatory power of detect factor x on the spatial distribution of detected factor y, the value of q ranges from 0 to 1; h=1,…, l, which represents the stratification of the detect factor x and detected factor y; n h and n are the number of samples for the layer h and the whole study area; ℎ 2 and 2 are the variance of y value for the layer h and the whole study area; ssw and sst are the sum of intra-layer variances and the total variance of the whole study area. the interaction detection can identify the explanatory power of the detect factors x1 and x2 to the detected factor y, whose operation steps are as follows: first, we calculate the q values of x1 and x2, respectively. second, a new layer x1∩x2 can be obtained by stacking the layer x1 and x2, on this basis, the q (x1∩x2) value can be calculated. third, the interaction type between x1 and x2 can be determined by comparing q (x1), q (x2), and q (x1∩x2) values. the risk detection is used to determine whether there exists a significant difference in the mean value of an attribute between the two sub-regions, which is tested by the t-statistic. its formula is as follows : where y h represents the average value of epidemic spread rate in the layer h, n h is the number of samples in the layer h, var represents the variance. we can compare whether there are significant differences in the influence of any detect factors x1 and x2 on the spatial distribution of the detected factor y by using the ecological detection, which is measured by the f-statistic. where 1 and 2 represent the sample sizes of the detect factors x1 and x2; 1 and 2 are the sum of the variances in the layers formed by x 1 and x 2 ; and l 1 and l 2 are the number of layers of x 1 and x 2 . the null hypothesis h 0 is: if h 0 is rejected at the significance level of , which indicates that x1 and x2 have significantly different effects on the spatial distribution of y. the arcgis software was used to classify the cumulative number of covid-19 cases in the following categories: 0; 1-50; 51-100; 101-300; and >300 persons. the epidemic spread rate was classified into the following categories: <1; 1-3; 3-5; 5-7; and >7 persons/day ( figure 1 ). j o u r n a l p r e -p r o o f (1) global spatial correlation characteristics in this paper, the cumulative number of confirmed covid-19 cases and the epidemic spread rate were taken as variables, the spatial weight matrix based on geographical adjacency was selected, and the global moran's i index, the p test value and the z statistic score of the cumulative number of confirmed covid-19 cases and the epidemic spread rate were calculated by using the geoda software, so as to clarify the global spatial correlation characteristics (table 1) . respectively, passing the significance test at the 1% level, implying that the spatial pattern of the epidemic spread rate was also characterized by a clustering distribution. (2) local spatial correlation characteristics the global moran's i index has the defect of ignoring the instability of local spatial processes. therefore, it is necessary to draw a lisa cluster map to analyze the local spatial correlation characteristics of covid-19 epidemic (figure 2 ). cluster areas were located in anqing, lu'an, jiujiang, nanyang, qianjiang, shennongjia forest region, and changde; and the range of 'low-low' cluster was basically consistent with that of february 6. in terms of quantity change, the number of units classified in the 'high-high' cluster first increased and then decreased; the number of units included in the 'high-low' cluster continued to decrease until they disappeared; that in the 'low-high' cluster experienced a process of initial decline and then rose again; and the number of units belonged to the 'low-low' cluster showed an increasing trend. therefore, it is not difficult to see that the layout trend of the j o u r n a l p r e -p r o o f cumulative number of confirmed covid-19 cases at the time nodes has not changed fundamentally, and was dominated by the 'high-high' and 'low-low' type. this indicates that the local spatial correlation characteristics of the confirmed covid-19 cases were also dominated by a positive correlation, although the clustering trend was weakened. overall, the 'high-high' cluster areas showed a layout trend from centralization to decentralization, which tended to be stable over time, especially for wuhan and its surrounding areas. there was a contiguous layout trend of the 'lowlow' cluster areas, which were mainly located in inner mongolia, gansu, ningxia, qinghai, tibet, and xinjiang. as for the epidemic spread rate, there were 16 administrative units in the 'high-high' cluster, 0 in the 'high-low' cluster, 5 in the 'low-high' cluster, and 75 in the 'low-low' cluster. the high-high cluster areas were located in wuhan, huangshi, yichang, xiangyang, ezhou, jingmen, xiaogan, jingzhou, huanggang, xianning, suizhou, xiantao, qianjiang, tianmen, nanyang, and xinyang; the 'low-high' cluster areas were located in anqing, lu'an, jiujiang, shennongjia forest region, and changde; and the 'low-low' cluster areas were located in western china. the covid-19 epidemic first occurred in wuhan, and then spread to other parts of china. therefore, people have been the carrier, the transportation network has been the channel, and the social and economic connections have been the internal driving force in the process of the epidemic spread. thus, we selected the indicators reflecting the population distribution, population inflow from wuhan, traffic accessibility, economic connection intensity, average temperature, and medical facilities conditions j o u r n a l p r e -p r o o f as the detection factors (table 2) , and the epidemic spread rate as the detected factor to assess the formation mechanism for the spatial pattern of covid-19 epidemic. note: the gravity model was used to calculate the intensity of economic contact between each region and wuhan, and the distance was the time reachable distance (meng and lu, 2011). firstly, the classification method of natural discontinuities in arcgis10.2 software was used to divide detection factors into 6 categories, the classified maps of the detection factors were drawn (figure 3 ). according to formulas (3)-(8), the determination ability of detection factors was calculated by using the geodetector software to analyze the influencing factors of epidemic spread. j o u r n a l p r e -p r o o f (1) factor detection analysis the q values of all the detection factors passed the significance test at the 5% level, indicating that these factors have a significant determination ability of the spatial distribution of the covid-19 epidemic spread. specifically, the q (p) values of x1, x2, x3, x4, x5 and x6 were equal to 0.060 (0.003), 0.504 (0.000), 0.041 (0.000), 0.404 (0.000), 0.021 (0.028) and 0.078 (0.000), respectively. according to the size of q value, the inflow of population from wuhan was the primary factor affecting the epidemic spread, and its explanatory power reached 50.4%. the economic connection intensity was the secondary determinant factor, and its explanatory power was 40.4%. the availability of medical facilities was the third determinant factor, which accounted for a 7.8% of explanation power. the determination ability of population distribution was 6%, while the traffic accessibility and average temperature were both relatively weak, below 5%. it is worth noting that the differentiation and factor detection analysis discussed only the determination ability of single factor on the epidemic spread rate, and did not consider the interaction effect of factors. (2) interaction detection analysis the interaction detector analysis is used to identify the interactions between any j o u r n a l p r e -p r o o f two factors. table 3 shows the interactions detection results between factors. it can be seen from table 3 (3) ecological detection analysis according to table 4 , it could be found that the differences among the detection factors were statistically significant. specifically, the influence of the population distribution (x1) on the spatial distribution of the epidemic spread rate was significantly different from the population inflow from wuhan (x2), economic connection intensity (x4), and average temperature (x5), but not different from the traffic accessibility (x3) and medical facility conditions (x6). the influence of the population inflow from wuhan (x2) was significantly different from that of the traffic accessibility (x3), economic connection intensity (x4), average temperature (x5), and medical facilities conditions (x6). there was a significant difference between the influence of traffic accessibility (x3) and that of economic connection intensity (x4), but there were no significant difference with the average temperature (x5) and medical facilities conditions (x6). the influence of economic connection intensity (x4) was different from that of the average temperature (x5) and medical facility condition (x6). there was no significant difference between the average temperature (x5) and the medical facilities conditions (x6). generally speaking, the detection factors selected in this paper are reasonable, and the differences among them are statistically significant. note: y means the difference of the influence of the two factors is significant with the confidence of 95%, while n means no significant difference. (4) risk detection analysis table 5 showed that the epidemic had the fastest spread rate when the population density was 1,162-2,564 persons/km 2 . when the proportion of population inflow from wuhan was maintained at 6.94-14.25%, the epidemic spread rate was fastest. when the economic contact intensity with wuhan was kept in the range of 598,158.64-1,524,023.05, the epidemic spread rate was fastest. when the geographical distance from wuhan was 68.38-540.98 km, the spread rate was fastest. when the average temperature in winter was maintained at 11-16°c, the epidemic spread rate was higher. the epidemic spread rate was higher when there were between 9.58 and 14.49 beds for 1,000 persons. it can also be found that the population distribution, population inflow from wuhan, economic connection intensity, medical facilities, and the epidemic spread rate were significantly positively correlated, while the traffic accessibility was negatively correlated with the epidemic spread rate. this paper studied the spatial and temporal variation and the influencing factors of the covid-19 epidemic spread in mainland china, which can provide references for formulating the public health policies and promoting the resumption of production. however, there exist the following problems. in terms of data sources, although many countries or regions have published the epidemic announcements of covid-19 in real time, and the epidemic data was very convenient, virtually most of countries or regions had more people infected than registered, which could affect the accuracy of the evaluation results. then, the population density data in 2018 was used as a replacement due to a fact that the population density for the each administrative unit in mainland china during the epidemic period was unavailable. the treatment method hid the drastic changes in the data because the covid-19 epidemic happened during the chinese spring festival period, which had a characteristic that the scale and frequency of population movements were intensified. it's worth noting that the population density is an important indicator to explain the epidemic spread rate, so the alternative data inevitably weakened the explanatory power of current research from this perspective. in addition, the factors affecting the epidemic spread were complex, and involved both the quantitative and the non-quantitative indicators. this paper constructed an indicator system of the multiple factors influencing the epidemic spread based on the principle of data availability; the other non-quantitative indicators might be ignored, which increased the uncertainty of evaluation results. for the research method, the formula of epidemic spread rate was applicable to compare the epidemic spread rate of different administrative units at three time nodes, which actually did not conform to the exponential growth rule of infectious diseases (such as the covid-19, sars, and mers (middle east respiratory syndrome)) in the exposed population. how to accurately measure the actual spread rate of the epidemic in each region was the direction of future research. second, the exploratory spatial data analysis method investigated the spatial clustering characteristics of covid-19 epidemic in administrative units at prefectural level and above, and did j o u r n a l p r e -p r o o f not consider the agglomeration development situation at a finer spatial scale, which inevitably weakened the application value of the research results. third, the geodetector method was adopted to obtain the most favorable range of the covid-19 epidemic spread in this paper, which was developed from the perspective of statistics. the sample data directly affected the final evaluation result, and no epidemiological investigation on the residents' health status was implemented, so the conclusions drawn from current research were uncertain to some extent. finally, there might have multicollinearity between the strength of economic connection economic and other factors in this paper, and the geodetector method was not used to deal with it, which would weaken the persuasiveness of the research results. (1) the temporal changes of the covid-19 epidemic in mainland china are clear, and the epidemic spread rate has an evident spatial variation. in terms of temporal change, the epidemic quickly spread to most regions from january 24 to february 6. the epidemic spread rate slowed down from february 6 to february 20, although the epidemic situation in some cities worsened sharply. the areas where the epidemic spread quickly were mainly located in the hubei province, its surrounding areas, and some economically developed cities. the western part of china, as well as the remote areas of central and eastern china experienced a slow epidemic spread. (2) the global and local spatial correlation characteristics of the covid-19 epidemic were dominated by clustering situations. specifically, the global spatial correlation characteristics initially increased and then decreased, while the local spatial correlation characteristics tended to be stable with the passage of time, and were mainly composed of the 'high-high' and 'low-low' cluster types. the 'high-j o u r n a l p r e -p r o o f high' cluster areas were located in wuhan, huangshi, yichang, xiangyang, ezhou, jingmen, xiaogan, jingzhou, huanggang, xianning, suizhou, xiantao, qianjiang, tianmen, nanyang and xinyang. the 'low-low' cluster areas were located in parts of inner mongolia, gansu, ningxia, qinghai, tibet, and xinjiang. (3) the population distribution, population inflow from wuhan, traffic accessibility, economic connection intensity, average temperature and medical facilities conditions had significant effects on the epidemic spread rate. the population inflow from wuhan was the primary factor affecting the epidemic spread, followed by the economic connection intensity, and the medical facilities conditions. the population distribution, traffic accessibility, and average temperature also had different degrees of influence on the epidemic spread. from the perspective of action direction, the population distribution, population inflow from wuhan, economic connection intensity and medical facilities conditions played a positive role in the process of epidemic spread, while the traffic accessibility played a negative role. (4) detection factors interacted through mutual enhancement and nonlinear enhancement, and their influence on the epidemic spread rate exceeded that of single detection factors. the interaction between the population inflow from wuhan and medical facilities conditions, as well as that between the population distribution and population inflow from wuhan, that between the population distribution and economic connection intensity, and that between the economic connection intensity and medical facilities conditions had a great influence on the epidemic spread. the interaction between the population distribution and traffic accessibility, as well as that between the population distribution and average temperature, that between the traffic accessibility and average temperature, and that between the average temperature and medical facilities conditions had little impact on the epidemic spread. influencing factors are analyzed. 2) the global and local spatial correlation characteristics of the epidemic distribution present a positive correlation. 3) the population inflow from wuhan and strength of economic connection are the main factors affecting the epidemic spread. 4) the interaction influence of detection factors on the epidemic spread exceeds that of the single factor. 5) when the average temperature in winter is maintained at 11-16°c, the epidemic spread rate is higher. population movement, city closure and spatial transmission of the 2019-ncov infection in china analysis of the economic impact of the ncp and countermeasure study local indicators of spatial association-lisa early transmission dynamics of novel coronavirus pneumonia epidemic in shaanxi province incidence trend of novel coronavirus (sars-cov-2)-infected pneumonia in china the continuing 2019-ncov epidemic threat of novel coronaviruses to global health-the latest 2019 novel coronavirus outbreak in wuhan exploratory spatial data analysis of the distribution of regional per capita gdp in europe nowcasting and forecasting the potential domestic and international spread of the 2019-ncov outbreak originating in wuhan, china: a modeling study evolution of patterns in the ratio of gender at birth in henan province transmission dynamics of 2019 novel coronavirus the diffusion characteristics of an outbreak of 2019 novel coronavirus diseases (covid-19) in guangdong province analysis of the spatio-temporal characteristics and transmission path of covid-19 cluster cases in zhuhai impact of high-speed railway on accessibility and economic linkage of cities along the railway in henan province spatial differentiation patterns of carbon emissions from residential energy consumption in small and medium-sized cities: a case study of kaifeng geodetector: principle and prospective preliminary analysis on the early epidemic and spatiotemporal distribution of new coronavirus pneumonia in guangdong province when will be the resumption of work in wuhan and its surrounding areas during covid-19 epidemic? a data-driven network modeling analysis determinants and identification of the northern boundary of china's tropical zone modeling and prediction for the trend of outbreak of ncp based on a time-delay dynamic system quantifying the influence of nature and socioeconomic factors and their interactive impact on pm 2.5 pollution in china backtracking transmission of covid-19 in china based on big data source key: cord-300435-vs0ntcsb authors: katz, al; peña, stephanie; alimova, alexandra; gottlieb, paul; xu, min; block, karin a. title: heteroaggregation of an enveloped bacteriophage with colloidal sediments and effect on virus viability date: 2018-10-01 journal: sci total environ doi: 10.1016/j.scitotenv.2018.04.425 sha: doc_id: 300435 cord_uid: vs0ntcsb four sediments in the colloidal size range: goethite, montmorillonite, illite, and kaolinite, were suspended with the bacteriophage φ6, a model enveloped virus, to determine relative rates of heteroaggregation and the effect of aggregation on virus viability. turbidity was measured on combinations of virus and each sediment type at low concentration to determine aggregation rates. aggregation of sediment with virus occurred regardless of mineral type, and larger fraction of virus is expected to aggregate with increasing sediment concentration leading to higher deposition rates. the negatively charged sediments, aggregated with φ6 (also negatively charged at neutral ph) at a faster rate than the positively charged sediments, yielding turbidity slopes of 4.94 × 10(−3) s(−1) and 7.50 × 10(−4) s(−1) for φ6-montmorillonite and φ6-illite aggregates, respectively, and 2.98 × 10(−5) s(−1) and 2.84 × 10(−5) s(−1), for φ6-goethite and φ6-kaolinite, respectively. this indicates that the interaction between sediments and virus is hydrophobic, rather than electrostatic. large numbers of virions remained viable post-aggregation, despite the fragility of the viral envelope, indicating that small-sized aggregates, which may travel more readily through porous media, may pose an infection risk. the fraction of φ6 that remained viable varied with sediment type, with montmorillonite-φ6 aggregates experiencing the greatest reduction in infectivity at 35%. tem analyses reveal that in all sediment-φ6 combinations, infectivity loss was likely due to disassembly of the viral envelope as a result of aggregation. • sediments interact with enveloped viruses but effects on viability are unknown. • light scattering measured aggregation rates of virus with four mineral types. • heteroaggregation was hydrophobic and faster with negatively-charged sediments. • the greatest reduction in infectivity occurred in virus-montmorillonite aggregates. • aggregation with sediment caused virus disassembly and infectivity loss. a b s t r a c t a r t i c l e i n f o the mechanisms that influence the transport of viruses are important for management of natural systems and freshwater resources. these may include human pathogens such as those introduced by fecal matter, but, more importantly, bacteriophage which serve to regulate bacterial populations (o'brien et al., 2017) . bacteriophage alter biogeochemical cycles through lysis of bacterial cells (díaz-muñoz and koskella and brockhurst, 2014) and impact eukaryotes that depend on bacterial populations, thus having a significant impact on the greater ecosystem. the distribution and residence time of viruses is affected by the chemistry of the water, e.g., dissolved organic matter, metals, and contaminants, but also the suspended materials, such as particulate organic matter (pom) and suspended sediment, primarily clays, which serve as substrate and habitat for biofilm-producing bacteria (alimova et al., 2006; alimova et al., 2009) . in fact, sediment-bearing biofilms have been shown to sequester virus particles in wetlands where they are subsequently concentrated and subject to re-release (flood and ashbolt, 2000) . furthermore, bacteriophages are utilized as subsurface tracers and indicators for a variety of environmental applications (ghanem et al., 2018; keswick et al., 1982; redman et al., 1997) and, therefore, their interaction with sediments may affect their quantification in hydrological experiments. an estimated 10 31 virus particles world-wide are prevalent in both soils and aquatic systems (breitbart and rohwer, 2005; weinbauer and rassoulzadegan, 2004) . in aquatic systems, the length of time in which a virus can interact with potential hosts is largely controlled by sinking rates (fuhrman, 1999) . these rates are strongly influenced by aggregation with suspended particles. sediments are known to influence virus transport and survival in porous media by controlling the potential for viruses to contaminate groundwater (jin and flury, 2002; chu et al., 2000) and to promote lysis of bacteria in soils (kimura et al., 2008) . the mineralogy and size of suspended sediments affects the extent to which viruses will aggregate and sorb to sediments (chu et al., 2000; jin and flury, 2002; mcgechan and lewis, 2002; syngouna and chrysikopoulos, 2015) . with a few recent exceptions, enveloped viruses (block et al., 2016; block et al., 2014) , have been largely omitted from studies of virus-sediment interaction, aggregation, and viability. enveloped viruses possess different structural properties from nonenveloped viruses and include important plant and animal pathogens such as herpesvirus, coronavirus and influenza a and b, all of which are found in natural and wastewaters (batik et al., 1980; gundy et al., 2008; rosenberg et al., 1980; sharp et al., 1975; stallknecht et al., 1990a; stallknecht et al., 1990b) . virus particles typically range from 20 nm to 500 nm in diameter, and are therefore considered colloidal particles. for non-enveloped viruses, the surface charge is determined by the protonation/deprotonation of amino acids in the capsid (elimelech et al., 1995) . however, for enveloped virions, surface charge is determined by envelope proteins and lipids. the colloidal interaction between virus particles and the small fraction of suspended sediments can be described by dlvo theory (derjaguin and landau, 1941; verwey and overbeek, 1948) , in which the potential between colloidal particles is the sum of the attractive van der waals potential and the coulomb potential (repulsive for like-charged particles and attractive for oppositely-charged particles). dlvo theory has been extended to include hydrophobic forces (van oss, 1993; van oss et al., 1990) . previous research has shown that for non-enveloped viruses, sorption is largely influenced by hydrophobicity. puls (1999), (2000) studied the attachment of three, non-enveloped, bacteriophages, t2, ms2 and φx174 to several clay fractions and calculated the electrostatic and hydrophobic contributions to the free energy. their calculations showed that surface hydrophobicity dictates sorption of viruses to clays. chrysikopoulos and syngouna (2012) looked at attachment of the bacteriophages ms2 and φx174 to kaolinite or montmorillonite, and using extended dlvo energy calculations, concluded that the virus-clay attachment was primarily through hydrophobic interaction. a study of heteroaggregation of the non-enveloped cowpea mosaic virus with colloidal hematite revealed that at ph 6, at which hematite carries a positive surface charge and the virus a negative charge, the aggregates accumulated four times as many viruses as hematite particles vilker et al. (1994) . however, at ph 3, in which both particle types are positively charged, the aggregates contained three times as many hematite particles as virus. from these results, they concluded that attraction between the virus and hematite is mostly governed by electrostatic interactions. the above studies all investigated non-enveloped viruses which are structurally different to viruses with lipid envelopes (e.g. influenza, paramyxovirus). in this work, we employ turbidity measurements to investigate the heteroaggregation of a model envelope virus, the bacteriophage φ6, with colloidal goethite and three clay minerals: illite, kaolinite and montmorillonite. φ6 is a member of the cystoviridae family of bacteriophage. the cystoviridae are the only phage family with an outer bi-lipid envelope. φ6 is a dsrna virus whose host cell is pseudomonas phaseolicola, a common plant pathogen. φ6 consists of an icosahedral nucleocapsid surrounded by a bi-lipid envelope and is therefore employed as a model for virus emergence in evolutionary studies and for human pathogens such as coronavirus (dennehy, 2017; mindich, 2004) . the diameter of φ6 is~80 nm. the φ6 virus carries negative charge at neutral ph (block et al., 2014) . montmorillonite and illite platelets both have positive charged edges and negative charged faces with an overall negative charge at neutral ph (gonzález sánchez et al., 2008; van olphen, 1962) . kaolinite platelets have negatively charged faces, and at neutral ph, negatively charged edges (gupta et al., 2011; schroth and sposito, 1997) . goethite is positively charged at neutral ph (gaboriaud and ehrhardt, 2003; zeltner and anderson, 1988) . the effect of the interaction of colloidal sediments and enveloped viruses on virus viability, the nature of that interaction is unknown. we will present aggregation rates as determined by turbidity experiments, the effect of the interaction between φ6 and sediments on φ6 infectivity, and discuss the environmental implications of our findings. in the early stage of colloidal aggregation, suspensions consist mostly of primary particles and aggregation is a bimolecular process in which the kinetics are dominated by the merging of individual primary particles to form doublets: n + n → n 2 (garcíagarcía et al., 2006; garcía-garcía et al., 2007) . the rate equation for the loss of primary particles into doublets can be written as: where n(t) is the number density of particles and k is the aggregation rate constant for doublet formation. the corresponding rate equation for doublet, n 2 , formation is: integration of eq. (1) gives: where n 0 is the number density of primary particles at t = 0. the average number of primary particles in an aggregate is η = n 0 /n(t) and thus in the early stage of aggregation: from eq. (4) it is seen that in the early growth region, aggregate growth is linear in time (kobayashi and ishibashi, 2011; puertas and nieves, 1997) . the turbidity (τ) for a system of monomeric colloidal aggregates is given by (katz et al., 2013) : where l is the optical path length; k = 2π/λ, is the optical wavenumber; c 0 k 4 a 6 is the scattering cross-section of a primary particle; a is the effective primary particle radius; d f is the fractal dimension of the aggregate; and r is the radius of gyration of the aggregate; ηn is the number density of primary particles and is constant for each individual suspension. in the initial stage of aggregation, the aggregates are small and if the primarily particles are much smaller than the optical wavelength, kr b b1. expanding eq. (5), and keeping only the lowest order terms in kr, it is seen that τ ∝ η, i.e. aggregate size, and at early time, τ ∝ kn 0 t. liu et al. (2007) considered measurements of heteroaggregation rate constants by turbidity for dispersions containing colloids of different sizes. they developed a method based on the t-matrix to evaluate changes in turbidity as two primary particles form a doublet during heteroaggregation. they also considered the effects of multiple scattering on turbidity and determined that multiple scattering effects are not significant when the relative volume of the scatterers is b0.1%. in the case of heteroaggregation of two distinct primary particles, e.g. viruses and sediments, three types of bi-molecular particle mergers are possible: sedimentsediment; virusvirus; and sedimentvirus. eq. (2) is modified to include the three possible modes of doublet formation (yu and borkovec, 2002) : in which n s and n v are the number of primary sediment and virus particles in the suspension, respectively; n ss , n vv and n sv are the number of sediment-sediment, virus-virus and sediment-virus doublets, respectively; and k ss , k vv and k sv are the rate constants for sedimentsediment, virusvirus, and sedimentvirus doublet formation, respectively. the light extinction for a system of heteroaggregation is given by a modification of eq. (5): where a eff is an effective primary particle radius, and the scattering cross-section, c 0 , is an average cross-section weighted by the concentrations of each type of primary particle in the aggregate. as in the case of mono-colloidal systems at early times, i.e. early stage of aggregation, kr b b1 and, keeping only terms in kr, τ is proportional to η. purified cystovirus φ6 was prepared following the procedure described in katz et al. (2012) . after purification, the virus was resuspended in buffer a, modified to have a reduced divalent cation concentration (10 mm kh 2 po 4 and 0.5 mm mgso 4 ). it was confirmed by counting plaque forming units (pfu) of p. phaseolicola infection that φ6 survives in the modified buffer for several days at room temperature. the four mineral types chosen for this study were goethite, kaolinite (city college of new york rock and mineral collection); illite, and montmorillonite (wards science, rochester, ny). composition and purity of mineral specimens was confirmed by x-ray powder diffraction (city college of new york). all sediments were first crushed into powders and each washed with a 5% sodium hypochlorite (bleach) solution overnight to remove any possible organic matter or microbial contaminants. sediments were then washed multiple times in distilled water to remove the sodium hypochlorite residue. the small clay fraction (b0.2 μm) was separated by centrifugation in a sorvall ultracentrifuge (thermofisher scientific, waltham, ma) with an ss34 rotor at 5000 rpm (3000 g) for 1440 s (montmorillonite), 1140 s (illite), 1200 s (kaolinite) or 720 s (goethite). the supernatants containing the small fraction were collected and sterilized by autoclaving at 121°c and 100 kpa above atmospheric pressure for 1800 s to eliminate possible bacterial contamination. turbidity measurements were performed at 20°c and ph = 7 with the aggregates in a 1 cm optical path length quartz cuvette. specimens were illuminated with a broadband halogen lamp (hl2000, ocean optics, inc., dunedin, fl.) coupled to an optical fiber. spectra were collected in the wavelength range of 400 nm to 1000 nm. the transmitted light was collected by a second optical fiber coupled to a spectrophotometer equipped with a ccd (hr2000, ocean optics, inc.) which transferred the data to a personal computer. a 1 mm diameter aperture positioned in front of the collection fiber limited data collection to transmitted light while blocking scattered light. a magnetic stirrer was employed to prevent settling of the suspended colloidal aggregates. the distance between the cuvette and aperture was 5 cm, limiting the collection solid angle to 0.00003 sr and thus restricting the intensity of forward scattered light incident on the collection fiber (katz et al., 2013) . for time-resolved measurements, each spectrum was integrated for 250 ms using a high-speed data acquisition mode which allowed rapid collection and transfer of many spectra (3600 spectra for the typical 900 s experiment) to a pc with no dead-time between spectra acquisitions. for the estimation of φ6 concentration by turbidity, spectra were integrated for 30 s. the φ6 concentration was estimated from turbidity, approximating the φ6 virions as spheres with a refractive index of 1.45 and a diameter of 80 nm. the φ6 turbidity is given by (chýlek and li, 1995; xu, 2003; xu et al., 2003) : where c s is the scattering cross section; n v is the φ6 concentration; l is the optical path length; n w is the refractive index of water; n v is the refractive index of φ6; r is the radius of φ6; and λ is the optical wavelength. φ6 is sufficiently small compared to the wavelength of visible light so that higher order terms can be ignored. based on the measured turbidity, the stock φ6 concentration was determined to be 7.8 × 10 11 cm −3 , prior to the 2× dilution incurred when mixed with an equal volume of suspended sediments. this estimate is slightly larger than the estimate from counting pfus (6.8 × 10 11 cm −3 ) but is likely more accurate as it also includes virions rendered non-infectious due to envelope defects. φ6, due to its lower refractive index and smaller size, scatters less efficiently than the selected sediments. therefore, for the heteroaggregation turbidity experiments, the φ6 concentration was adjusted to have a lower turbidity than the turbidity at the lowest sediment concentration. the φ6 stock suspension was diluted to have a turbidity of 0.128 at 750 nm. heteroaggregation experiments were performed by mixing 1 ml of suspended φ6 with 1 ml of each suspended sediment. this resulted in a further 50% dilution of the cation concentration (5 mm kh 2 po 4 and 0.25 mm mgso 4 ). due to both the larger volume of the sediment primary particles (~0.2 μm) and higher refractive index. refractive indices of the three sediment types are (geometric mean of the three axes): goethite: n = 2.18; illite: n = 1.58; kaolinite: n = 1.56; montmorillonite: n = 1.55 (deer et al., 1992; shannon et al., 2002; weidler and friedrich, 2007) compared to φ6 particles (80 nm), the sediment primary particles have a higher scattering cross-section than the virions. therefore, the heteroaggregation experiments were performed using a higher concentration of viral particles than sediments. the sediment concentrations were adjusted to have a turbidity of~0.6 (after 2× dilution by addition of virus suspension) at 750 nma wavelength in which light extinction losses are primarily due to scattering rather than absorption. the concentrations were chosen so that the total volume of the scatterers was b0.1% of suspension volume, thus staying in the single scattering regime and keeping the incidence of multiple scattering small (katz et al., 2013; wind and szymanski, 2002; xu and sun, 2010) , while still providing a reasonable signal-to-noise level. the sediment and virus concentrations after the 2× dilution are summarized in table 1 . after completion of the turbidity measurements, the suspensions were centrifuged at 13,000 rpm (16,000 g) for 600 s. the centrifugation was sufficient to pellet the smallest heteroaggregates (i.e. doublets) and individual sediment primary particles but not individual virions. the pellets were resuspended in buffer and both the resuspended pellets and supernatants were analyzed for the presence of φ6 proteins by sds-page. the separated heteroaggregate pellets and supernatants were analyzed by sds-page (studier, 1973) . the fraction of φ6 in the pellets was estimated by analyzing the relative densities of the p1, p2 and p3 protein bands of the heteroaggregate pellets and supernatants. it is noted that the sds-page experiment does not resolve p1 and p2 due to the closeness of their molecular weight (85 kda and 75 kda, table 1 concentrations of colloidal particles. primary particles cm −3 goethite 0.096 5.3 × 10 9 illite 1.9 9.6 × 10 10 kaolinite 0.66 3.9 × 10 10 montmorillonite 1.6 9.6 × 10 10 φ6 3.9 × 10 11 respectively). p1 is the largest molecular weight protein in φ6 and has a relatively high copy number (120 per virion). thus, p1 is the highest density sds-page band of all the φ6 proteins. viable virus concentrations after aggregation were calculated using the plaque assay technique. the pelleted aggregates were vortexed prior to plaquing to disaggregate the mixture and separate the viruses from the sediments. the supernatants and final, disaggregated, clay suspensions were spot checked on plates with growing p. phaseolicola to determine number of virions in the system. heteroaggregates from the isolated pellets (section 3.3.3) were prepared for tem using standard techniques. samples were negatively stained with uranyl acetate. a minimal amount of stain was employed to reduce the effect of the stain on abundant viral proteins, which would impede identification of viral particles. micrographs of the heteroaggregates were acquired with a zeiss 902 tem operating at 80 kev with a 2048 × 2048 pixel detector. magnification was 85,000× corresponding to 0.512 nm/pixel. φ6 particles are identifiable in the micrographs from size and morphology. micrograph insets presented in the results section were re-sampled 4:1 using coreldraw (version ×8, corel corp, ottawa, can) to reduce pixelation in the enlarged insets. the contrast of the insets were enhanced using coreldraw's autoadjust function. prior work (block et al., 2014) has demonstrated that φ6 does not aggregate in buffer a at neutral ph, therefore k vv = 0 (eq. (6)). it was next confirmed by turbidity measurements that, individually, the four suspended sediments do not aggregate in the dilute buffer. the time evolution of the sediment turbidities at 750 nm, measured over a 900 s time period, are plotted in figs. 1(a-d) . the turbidities remained constant for these measurements, confirming that the cation concentration in the buffer is sufficiently dilute so as to not cause the sediments to aggregate. thus, k ss in eq. (6) can be taken to be ≈0 and eq. (6) simplifies to: i.e. primarily hetero-doublets are being formed at early time rather than virus-virus or sediment-sediment doublets. in this case, from eq. (7), dτ dt ∝k dnsv dt , i.e. the rate of hetero-doublet formation. the turbidity of the heteroaggregates at 750 nm is plotted in fig. 2 (a-d) . the φ6-goethite and φ6-kaolinite heteroaggregates demonstrated a linearly increasing turbidity over the entire 900 s time frame of the experiments, indicating that aggregation remained in the linear range, i.e. early stage, and consisted primarily of doublet formation. the turbidity slopes for φ6-goethite and φ6-kaolinite were 2.98 × 10 −5 ± 1.2 × 10 −7 s −1 and 2.84 × 10 −5 ± 2.2 × 10 −7 s −1 , respectively. the respective linear fits to the turbidity are shown in fig. 2a and c as dotted lines. the least squares linear fit was performed using originpro software (originlab, northampton ma, usa). in both the φ6-illite and φ6-montmorillonite heteroaggregates the duration of the linearly increasing turbidity was significantly shorter (30 s for φ6-illite and 15 s for φ6-montmorillonite). the early stage turbidity changes for illite and montmorillonite, along with linear fits, are plotted in fig. 3 . the corresponding slopes during the linear region (primarily doublet formation) are 4.94 × 10 −3 ± 1.9 × 10 −4 s −1 for φ6montmorillonite and 7.50 × 10 −4 ± 2.9 × 10 −5 s −1 for the φ6-illite aggregates. exact calculations of the heteroaggregation rates from turbidity require knowledge of the scattering cross-sections of both singlets and the doublet (liu et al., 2007; yu and borkovec, 2002 ). the precise shape of the virus-clay platelet doublet is not well known though there is evidence that virusclay platelet doublets occur as both edge-attached and face-attached (block et al., 2014) . although imprecise knowledge of doublet shape complicates calculations of heteroaggregation rates, analysis of the turbidity slope coupled with particle concentrations allows one to determine relative aggregation rates between φ6 and the four sediment types, elucidating the nature of the interaction. from the aggregation rates, it is observed that doublet formation occurs at a much slower rate for goethite and kaolinite compared to montmorillonite and illite. that the two positively charged sediments (goethite and kaolinite) aggregate more slowly with the negatively charge virions than the two negatively charged sediments (montmorillonite and illite), it is likely that the interaction between φ6 and the sediments is not electrostatic in nature but hydrophobic, similar to that observed for ms2 and φx174 (chrysikopoulos and syngouna, 2012) . the sds-page of the pellets and supernatants for the four heteroaggregates are plotted in fig. 4a along with the non-aggregated φ6 control. comparisons of the density profiles of the p1 and p3 protein bands (fig. 4b) reveal that for all four heteroaggregates, most of the virions aggregated with the sediments (montmorillonite 80%; kaolinite 73%; illite 76%; goethite 68%) and the remaining non-aggregated virions in the supernatant. it is expected that formation of larger aggregates resulting from either higher cation concentrations or greater sediment concentrations would result in a greater fraction of the virions aggregating. it should be noted that the sds-page results do not provide information as to virus viability, since the proteins in partially disassembled virions will likely remain intact and thus appear in their respective sds-page bands. φ6 viability in the supernatants and pellets as determined by plaquing is presented in fig. 5a . the distribution of virions (viable and non-viable) is shown in fig. 5b . the viable virus population in the control was 3.5 × 10 11 , in good agreement with our estimates from turbidity (which includes non-infectious virions). φ6 in the montmorillonite aggregates displayed a significant decrease in infectivity for both virions in the aggregates (14% viable) and planktonic cells (35% viable), which is consistent with results from our previous work (block et al., 2014) . in the φ6-kaolinite and φ6-illite aggregates, the virions in the pellets, i.e. aggregated virions, show an appreciable loss in infectivity (14% and 27% of original virus populations remained viable for kaolinite and illite, respectively), while virions that did not aggregate remained close to 100% viable. for the φ6-goethite heteroaggregates, 49% of the virions in the pellets remained viable, while supernatant virion viability was near 100%. the higher viability values for in the φ6-goethite pellet is likely due to fewer virions aggregating as a result of the lower goethite concentration required to achieve approximately equal turbidity as in the experiments with clay minerals to account for goethite's greater refractive index. analysis of tem micrographs confirmed the presence of φ6 in each of the four heteroaggregate suspensions. the viruses were observed to be attached to both platelet faces and edges of the three clay minerals. distortion of the virus morphology was evident in the micrographs (figs. 6a-d). in the φ6goethite heteroaggregates, the virions appear hexagonal with a 55 nm diameter (fig. 6a ). this morphology is consistent with that in micrographs of the icosahedral nucleocapsid (alimova et al., 2015) , indicating that the viral envelope has been disassembled during aggregation with goethite. analysis of tem micrographs of φ6 heteroaggregated with the three clay minerals (figs. 6b. φ6illite; 6c. φ6kaolinite; 6d. φ6montmorillonite) reveal substantial distortion in the φ6 morphology. the viral particle diameters are similar to the 55 nm diameter of the nucleocapsid rather than the 80 nm diameter of the intact virions and the virions appear to be distinctly non-circular. the morphologic changes indicate that the sediments partially disassembled the viral envelopea process likely responsible for the reduced rate of virus infectivity. turbidity measurements on dilute combinations of bacteriophage φ6 and four sediment types were collected to determine the relative rates of heteroaggregation. negatively charged sediments aggregated with φ6 at a faster rate than positively charged sediments, indicating that the interaction is not electrostatic, but hydrophobic in nature. because k, the rate constant, is independent of concentration, the relative rates for aggregation at low turbidity are a good predictor of rates at higher concentrations. for all experiments, most of the virions aggregated with sediments regardless of mineral type. at higher sediment concentrations, we expect an even larger viral fraction to aggregate, resulting in higher deposition rates. nevertheless, at the low concentrations of our experiments, heteroaggregated viruses experienced a loss of infectivity. despite the fragility of the viral envelope, a large number of virions remained viable, indicating that small-sized heteroaggregates may pose an infection risk. while non-aggregated virions in the φ6goethite, φ6 -kaolinite and φ6illite suspensions remained near 100% viable, in the φ6montmorillonite suspensions, a substantial fraction (35%) of the non-aggregated φ6 also lost viability. tem analysis revealed that the observed reduction in infectivity is likely due to partial disassembly of the viral envelope after aggregation. in conclusion, it is expected that viral disassembly and loss of infectivity is likely to be exacerbated with increased contact between virions and sediments which occurs within larger aggregates. the formation of sediment-virus heteroaggregates and subsequent virus inactivation has potential implications for remediation, spread of disease, and management of wastewater particularly during reintroduction via porous media into groundwater systems. our results suggest that soils containing clay minerals, and in particular, montmorillonite, may potentially serve to inactivate viruses possessing a rigid lipid envelopes during colloidal transport. however, our results also show that even in the case of viruses that are not inactivated by association with a solid phase, colloidal sediments could facilitate the transport of viruses into aquifers as small heteroaggregates. furthermore, because multiple virions aggregate with colloidal sediment even in dilute concentrations, forming heteroaggregates in the colloidal size range, this interaction must be considered in conjunction with specific infectivity (ghanem et al., 2018) when phages are used in tracer experiments. hybrid native phosphorescence and fluorescence spectroscopy for cancer detection bacteria-clay interaction: structural changes in smectite induced during biofilm formation the ϕ6 cystovirus protein p7 becomes accessible to antibodies in the transcribing nucleocapsid: a probe for viral structural elements an epidemiologic study of the relationship between hepatitis a and water supply characteristics and treatment disassembly of the cystovirus ϕ6 envelope by montmorillonite clay montmorillonite-mediated aggregation induces deformation of influenza virus particles here a virus, there a 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toward an understanding of the turbidity measurement of heterocoagulation rate constants of dispersions containing particles of different sizes sw-soil and water transport of particulate and colloid-sorbed contaminants through soil, part 1: general principles packaging, replication and recombination of the segmented genome of bacteriophage φ6 and its relatives diversity of dna viruses in effluents of membrane bioreactors in traverse city, mi (usa) and la grande motte (france) a new method for calculating kinetic constants within the rayleigh -gans -debye approximation from turbidity measurements filtration of recombinant norwalk virus particles and bacteriophage ms2 in quartz sand: importance of electrostatic interactions the risk of acquiring hepatitis from sewage-contaminated water surface charge properties of kaolinite refractive index and dispersion of fluorides and oxides nature of the surviving plaque-forming unit of reovirus in water containing bromine effects of ph, temperature, and salinity on persistence of avian influenza viruses in water persistence of avian influenza viruses in water analysis of bacteriophage t7 early rnas and proteins on slab gels experimental investigation of virus and clay particles cotransport in partially saturated columns packed with glass beads unit layer interaction in hydrous montmorillonite systems acid-base interfacial interactions in aqueous media dlvo and non-dlvo interactions in hectorite theory of the stability of lyophobic colloids interaction between a plant virus and colloidal hematite determination of the refractive index of particles in the clay and sub-micrometer size range are viruses driving microbial diversification and diversity? quantification of scattering corrections to the beer-lambert law for transmittance measurements in turbid media light extinction and absorption by arbitrarily oriented finite circular cylinders by use of geometrical path statistics of rays evaluation of the uncertainties caused by the forward scattering in turbidity measurement of the coagulation rate anomalous diffraction of light with geometrical path statistics of rays and a gaussian ray approximation distinguishing heteroaggregation from homoaggregation in mixed binary particle suspensions by multiangle static and dynamic light scattering surface charge development at the goethite/aqueous solution interface: effects of co 2 adsorption partial support for this project was provided by psc-cuny award trada-46-247, jointly funded by the professional staff congress and the city university of new york. key: cord-258595-bk35vxlr authors: westhaus, sandra; weber, frank-andreas; schiwy, sabrina; linnemann, volker; brinkmann, markus; widera, marek; greve, carola; janke, axel; hollert, henner; wintgens, thomas; ciesek, sandra title: detection of sars-cov-2 in raw and treated wastewater in germany – suitability for covid-19 surveillance and potential transmission risks date: 2020-08-18 journal: sci total environ doi: 10.1016/j.scitotenv.2020.141750 sha: doc_id: 258595 cord_uid: bk35vxlr abstract wastewater-based monitoring of the spread of the new sars-cov-2 virus, also referred to as wastewater-based epidemiology (wbe), has been suggested as a tool to support epidemiology. an extensive sampling campaign, including nine municipal wastewater treatment plants, has been conducted in different cities of the federal state of north rhine-westphalia (germany) on the same day in april 2020, close to the first peak of the corona crisis. samples were processed and analysed for a set of sars-cov-2-specific genes, as well as pan-genotypic gene sequences also covering other coronavirus types, using reverse transcription-quantitative polymerase chain reaction (rt-qpcr). additionally, a comprehensive set of chemical reference parameters and bioindicators was analysed to characterize the wastewater quality and composition. results of the rt-qpcr based gene analysis indicate the presence of sars-cov-2 genetic traces in different raw wastewaters. furthermore, selected samples have been sequenced using sanger technology to confirm the specificity of the rt-qpcr and the origin of the coronavirus. a comparison of the particle-bound and the dissolved portion of sars-cov-2 virus genes shows that quantifications must not neglect the solid-phase reservoir. the infectivity of the raw wastewater has also been assessed by viral outgrowth assay with a potential sars-cov2host cell line in vitro, which were not infected when exposed to the samples. this first evidence suggests that wastewater might be no major route for transmission to humans. our findings draw attention to the need for further methodological and molecular assay validation for enveloped viruses in wastewater. the current sars-cov-2 pandemic has far-reaching global consequences on public health, economic activities, and societies as a whole, which are unprecedented in many respects and cannot be fully assessed yet (who, 2020) . the number and proportion of persons infected with covid-19 are mainly determined based on individual testing and laboratory-based bio-molecular diagnostics using, e.g., reverse transcription-quantitative polymerase chain reaction (rt-qpcr). covid-19 cases are reported by regional health authorities and aggregated on the level of, e.g., the federal states in germany, as well as on a national level (rki, 2020) . it is expected that, based on the individual testing that is often triggered by symptoms of test candidates or their respective risk profile, the actual state of infection in a specific region can only be very roughly estimated (wurtzer et al. 2020) . oral swab samples (wu et al. 2020a) . therefore, it must be systematically assessed whether the virus might, in addition to respiratory droplets, also be transmitted via feces in wastewater (nemudryi et al. 2020 , wu et al. 2020a . it could be shown that the duration of viral shedding differed among patients between 14 and 21 days past the onset of the infection . furthermore, the magnitude of shedding varied from 10 2 to 10 8 rna copies per gram feces (lescure et al. 2020 , pan et al. 2020 . wastewater-based epidemiology (wbe) has been suggested as a potentially useful complementary tool to gain insights into the degree of infection spread in a population , choi et al. 2018 , rodriguez-manzano et al. 2010 . recently, various studies detected sars-cov-2 rna in wastewater worldwide (cf. (medema et al. 2020) , france (wurtzer et al. 2020) , usa , australia , and italy (la rosa et al. 2020) . wurtzer et al. (2020) reported the analysis of sars-cov-2 genes in the greater paris (france) area and were able to correlate trends in gene occurrence in the wastewater of different wastewater treatment plants (wwtp) with the number of infected individuals. medema et al. (2020) have shown a good correlation between the number of covid-19 cases and the gene concentration in the wastewater of different dutch cities. however, the studies differed in, e.g., the type of samples, processing procedure, and targeted genes (like n1, n2, n3, and orf1ab) in rt-qpcr analysis. only a few studies were complemented by infectivity tests of the genes to determine whether the genetic material was present in intact virus particles or as free nucleic acids. furthermore, only a few studies comprised phylogenetic analyses to better identify the genetic profile of the obtained material. an overview of recent studies conducted and reported in 2020 is given in table 1 . nine municipal wwtp operated by six different water boards were selected for analysis throughout north-rhine westphalia (germany). the plants differed in their design capacity, treatment processes, and connected catchment area characteristics (table 2 ). using installed autosampler devices, the operators of the wwtp collected 24 h flow-dependent composite samples on april 8 th , 2020, during dry-weather conditions, either midnight to midnight or between the morning of april 8 th , and the morning of april 9 th . in addition to raw wastewater (sewage) inflow samples collected after the sand trap, treated sewage was sampled at selected locations ( j o u r n a l p r e -p r o o f j o u r n a l p r e -p r o o f frozen wastewater samples were thawed at 4°c, and a total of 45 ml were further processed. first, wastewater was centrifuged at 4,700x g for 30 minutes without break, and the clear supernatant was harvested. purified wastewater was then concentrated using centrifugal ultrafiltration units (amicon® ultra-15 centrifugal filter unit, sigma). therefore, 15 ml of wastewater was added to the filter unit and centrifuged for 15 minutes at 3,500x g, and the concentrated supernatant was harvested. this was repeated twice until 45 ml of wastewater were completely concentrated (final volume of concentrated supernatant approximately 450 µl). for the solid phaseof the wastewater sample, the pellet of the 45 ml sample was first washed with deionized water to remove aqueous remains from the sample and centrifuged at 4,700x g for five minutes before being resuspended in 150 µl deionized water and centrifuged at 4,700x g for five minutes again. a volume of 150 µl of the supernatant was then harvested for further rna extraction, and the mass was determined (approx. 150 mg in influent and 5-10 mg in effluent). contaminated equipment (e.g., reaction tubes, tips, filter units) were collected and autoclaved according to the daily cleaning program in the lab. rna was isolated using the nucleospin rna virus kit (macherey nagel) following the manufacturer's instructions. briefly, 150 µl supernatant was mixed with lysis buffer supplemented with carrier rna. after binding on silica membranes, samples were washed several times and eluted in 50 µl rnasefree water. isolated rna was stored at -80°c. probe-based luna universal one-step rt-qpcr kits, 2 µl of rna were subjected to reverse transcription performed at 55°c for 10 minutes. initial denaturation was performed for 1 min at 95°c j o u r n a l p r e -p r o o f table 3 : sequences of primers and probe established and verified for the detection of sars-cov-2 (in patient material) by rt-qpcr. e_sarbeco_f1 acaggtacgttaatagttaatagcgt figure s1 . purified wastewater samples that tested positive for sars-cov-2 (p2, p5, p11, p12) were investigated for replication-competent viruses following a recently published procedure (hoehl et al. j o u r n a l p r e -p r o o f all physicochemical and chemical parameters were analyzed immediately after sampling following din, en, or iso standard protocols. if this was not possible, the samples were chemically stabilized and then measured within the approved timeline of the standard protocols. the ph and conductivity were measured using a sension mm374 hach lange instrument (en iso 10523 (2012-04), en 27888 ). for the content of the dry residues, a defined volume of wastewater sample was dried at 105°c for 24 h (din 38409-1 (1987-01)), and the residue was weighed by a sartorius a 120 s balance. ready-to-use-cell test kits were used to analyze the chemical oxygen demand (cod) with a macherey & nagel pf12 and vario 4 (test kits 985022, 985033 and 98029, iso 15705 (2003-01)). total organic carbon (toc) and total bounded nitrogen (tn b ) were analyzed via combustion using a shimadzu carbon/nitrogen analyzer (en 1484 (en (1997 , en 12260 (2003-12)). for the analysis of ammonia, nitrate, nitrite, total organic nitrogen, ortho-phosphate, and other ions such as chloride and sulfate, a gallery discrete analyzer with photometric and turbidity methods were used after filtration through a 0.45-µm filter (thermo fisher scientific, iso 15923-1 (2014-07)). two different types of population size markers (exogenous and endogenous) were measured by liquid chromatography coupled with mass spectrometric detection (lc-ms) and photometric detection with a discrete analyzer (choi et al. 2018 j o u r n a l p r e -p r o o f acetic acid were added to the methanol and water. the separation was run after injection of 10 µl sample with a linear gradient starting with 20% up to 90% and ending again with 20% methanol. all data were collected in srm mode by using mass-labeled internal standards (supplementary table s1) and xcalibur 2.0.7. sp1 software for data acquisition and quantification. the loqs are in the range of 10 to 30 ng/l. as endogenous parameters, creatinine and urea were quantified after filtration via a 0.45µm filter by using a gallery discrete analyzer (thermo fisher scientific). creatinine was measured by photometry at 540 nm as quinonimine-chromogen after enzymatic reactions of creatine with creatinase, sarcosine oxidase, and ascorbate oxidase with a modified clinical method using thermo fisher scientific reagent kit (enzyme. colortest pap 981896) (dörner 2003) . the urea-method is based on a standardized bathwater method. in the first step, the contents of urea and ammonium are detected simultaneously. after enzymatic reaction of urea with urease to ammonium, ammonium reacts with nicotinamide adenine dinucleotide phosphate (nadph) in a buffered solution at ph 8. the loss of nadph is directly proportional to the ammonium content (thermo fisher scientific test kit 981820). the urea content is calculated by subtraction of the ammonium content (iso 15923-1 (2014-07) from the total content of urea + ammonium. in germany, local health authorities report the number of covid-19 cases confirmed by laboratory diagnosis after aggregation from the community to district level to state and federal authorities. whenever available, the cumulative prevalence and the cumulative number of covid-19 patients recovered and deceased were obtained from community-level reports published on the homepages of the responsible local health authorities on april 9 th , 2020. if community-level reports were not available, district-level data published by the state health ministry of north rhine-westphalia (mags) on april 9 th , 2020, was used. since the catchment areas of wwtps rarely correspond to administrative boundaries, the cases were estimated by calculating weighted sums relative to the j o u r n a l p r e -p r o o f residents of each community connected to that sewer network. acute prevalence was calculated by subtracting reported recovered and deceased patients (table 4) . nominal incidences (i nom ) were calculated by dividing the estimated number of cases (n nom ) in a catchment area by the nominal number of connected residents to the sewer (pe nom ). we note that these are estimates with considerable uncertainty since cases might be unevenly distributed between neighbouring districts, and recovered cases are often not based on laboratory diagnosis but the end of ordered quarantine. in addition, the actual number of persons staying in the catchment area on the day of sampling (pe actual ) may also differ from the nominal number of connected residents (pe nom ). treating the complete flow of the river emscher, wwtp klem is partly treating water that was treated upstreaming by other treatment plants. based on the assumption of poor removal of sars-cov-2 in conventional wwtp, reported cases for klem in table 4 are upper estimates covering the complete upstream catchment. showed a sequence identity above 90%. the similarity of c2 and c4 amplicons to the sars-cov-2 specific sequence was 50% and 47.3%, respectively ( figure 4) . therefore, we conclude that the retained samples were negative for sars-cov-2. in wastewater treatment, solid residues are largely removed. we thus compared the amount of viral rna in the aqueous and solid-phase of both inflow and effluent samples. during centrifugation in j o u r n a l p r e -p r o o f the processing of the wastewater samples, solid and aqueous phases are separated. to our understanding and as shown in other studies (kocamemi et al. 2020 ), viral rna of solid and liquid phase needs to be considered in wastewater surveillance. when comparing the aqueous and solid phase of the samples, we found a one log unit higher sars-cov-2 rna copy number per ml in the solid phase (25 copies/ml) compared to the aqueous phase of the inflow sample (1.8 copies/ml), respectively ( figure 5a ). the difference between the aqueous and solid phase was less evident in the effluent sample, with 8.8 and 13 gene equivalents per ml, respectively ( figure 5b ). when comparing the aqueous phase only, the effluent exhibited a higher gene equivalent concentrations than the influent, which we attribute to repartitioning of gene material from the solid-to the liquid phase during wastewater treatment. in contrast, a difference of total viral copy numbers per ml between untreated and treated wastewater was not detectable ( figure 5a and b). this might be explained by the sample conditions. while the residence time of the wastewater is about one day at the wwtp, sludge is continuously exchanged with an average sludge age of 10 to 14 days. we assume that solidphase concentrations are lower-estimates since we did not test whether further extraction steps could mobilize additional sars-cov-2 rna from the solid phase. results are shown as mean + sd of two independent pcr measurements from same sample material. rdrp rt-qpcr c t values for standard range between 18 (standard 1 = 10 8 ) and 37 (standard 6 = 10 2 ). values of tested wastewater above c t 38 were considered negative for sars-cov-2. standard curve was calculated using bio-rad cfx manager software with e = 96.5 %, r 2 = 0.990 and slope = -3.408. although the wastewater in the investigated plants was treated by different processes, viral rna is not eliminated, as shown above. to test the infectious potential of untreated and treated wastewater, a cell culture model was used to analyse that impact ( figure 6 ). infection of differentiated caco-2 cells with cell culture grown, replication-competent sars-cov-2 (moi 0.01) led to the induction of a cytopathic effect (cpe after 48-72 hours). the cpe is characterized by round and shrinking cells that detach from the culture surface. observation of cpe after two to three days at a low moi indicated rapid to moderate replication of the virus. inoculation of differentiated caco-2 cells for ten days with purified and concentrated wastewater (p2, p5, p11, and p12) did not result in the production of infectious sars-cov-2 particles (data not shown), which suggests that treated sewage appears to be non-infectious even though viral rna fragments can be detected. due to the lack of cpe, quantification and verification by rt-qpcr was not performed. the wastewater samples analysed showed typical wastewater characteristics for the different types of wwtps studied (brückner et al. 2018; metcalf and eddy 2012; supplementary j o u r n a l p r e -p r o o f 4. discussion during the sars-cov-2 pandemic, testing different sample material (e.g., throat swabs) was a crucial step in the detection of hotspots and limiting transmission. . the first sars-cov-2 pcr assays were developed against the e-gene and the n-gene to detect the virus in patient samples, and numerous studies analysing wastewater for sars-cov-2 surveillance used e-gene or n-gene specific pcrs (medema et al., ahmed et al., wu et al., 2020) . to a minor proportion, also pcr targeting sars-cov-2 rdrp was used (wurtzer et al., 2020) . in this study, wastewater samples were analysed with two different pcrs targeting sars-cov-2 rdrp and m-gene. in an initial analysis, a control sample when sequencing the different pcr amplicons obtained using wastewater samples taken during the sars-cov-2 pandemic and long before the outbreak (retained samples), distinct results for the test sample (p12) which fits sars-cov-2/human/usa/ca-czb-1525/2020 isolate from ncbi database was found, but not for the retained samples suggesting an unspecific signal in rt-qpcr, respectively. although rna samples used for pcr are highly purified, there might have been environmental contaminants affecting pcr. pcr is a highly sensitive method to detect nucleic acid and is strongly affected by ph, salt concentration, and contamination with extraneous nucleic acids that lead to false-negative or false-positive results, respectively (schrader et al. 2012; paul et al. 1991 which are complicated to sequence. establishing qualitative nested pcr could be an option to improve sequencing results. furthermore, extraneous nucleic acids can be accumulated during the concentration process of the wastewater sample. while single studies may avoid the accumulation of extraneous nucleic acids using filter units with 10 kda cut-off and therefore also could limit detection of sars-cov-2, most studies used filter units with 100 kda cut-off or other methods for concentrating wastewater samples medema et al. 2020; nemudryi et al. 2020; la rosa et al. 2020a) . although no false-positive results are described in these analyses, these studies did not use retained wastewater samples before the sars-cov-2 pandemic as control. nevertheless to establish sars-cov-2 wastewater-based epidemiology as a reliable tool for early-warning and surveillance of the current or future covid-19 outbreaks, the method´s detection limit, precision, accuracy, and reliability must meet certain criteria to be useful for public surveillance. for example, early-warning requires a low detection limit to detect the very first cases, while in later phases of the epidemics, high precision and accuracy are needed to survey whether certain thresholds are exceeded, for example, the threshold currently set in germany of 50 active cases per 100,000 residents. on the day of our sampling campaign, we estimate the nominal acute incidence of covid-19 to range between 30 and 174 cases per 100,000 residents in the nine catchment areas studied (table 4 ). based on surveillance results (figure 4 ), our findings indicate that the rt-qpcr employed is capable of resolving acute incidences of 50 cases per 100,000 residents in dry-weather conditions, although the method has not yet been optimized in terms of sensitivity and precision to detect even lower incidence. the nine catchment areas studied differ considerably in size, wastewater flow (table 2) , and nominal numbers of covid-19 cases at the day of sampling ranging from 36 to 1,037 acute cases and from 85 to 1924 cumulative cases (table 4) . inter-comparing these nine catchment areas, we plotted the estimated cumulative and the acute prevalence against the measured sars-cov-2 load (figure 8 ), the latter calculated from rt-qpcr measured m-gene copy concentration ( figure 4 ) and the actual wastewater flow q actual on the day of sampling (table 2) . clearly, the estimated nominal number of j o u r n a l p r e -p r o o f covid-19 cases increases with increasing measured sars-cov-2 load, resulting in correlations both for cumulative and acute prevalence ( figure 8a and b). scatter in the correlations might be attributed to various reasons, including variations in virus rna recovery and uncertainty in the estimated prevalence data. in contrast, plotting the incidence against sars-cov-2 concentration did not yield a conclusive correlation (not shown), likely because the precision of the qpcr employed was not sufficient to discriminate relatively minor differences in the incidence prevailing in the studied catchment areas at the time of sampling, ranging from 30 to 174 cases per 100,000 residents (less than an order of magnitude, figure 8c and d). although it cannot be evaluated based on the available data, if this correction is superior, it illustrates the potential of bioindicators to account for differences in wastewater composition. in contrast to our approach, medema et al. (2020) reported catchment-specific correlations plotting the increase in concentration (not load) of the n gene assays (and cycles of the e gene assays) against the increase in cumulative incidence from 0.1 to 100 cases per 100,000 residents (3 log 10 units) over a 7-weeks outbreak of the pandemics. while catchment-specific temporal correlations may be less susceptible to interference with other factors, we consider rna load-based evaluations more reliable to cope with variations in wastewater flow, for example, stormwater events in combined sewer systems or variations in industrial wastewater production during a lockdown of industry and businesses. table s5 . our results suggest that detected rna fragments appear to be non-infectious based on smallvolume laboratory studies testing about 1 to 10 gene copies in one reaction. however, given the large capacity and flow rate of wwtps (table 2) , we calculate that each of the studied wwtp emits 6*10 10 to 6*10 12 sars-cov-2 gene equivalents per day to the receiving water bodies, some of which serve as crucial water resources for drinking water production, cooling water abstraction, public swimming, irrigation, recreation, and natural habitats. this viral load can be very roughly compared to the potential viral shedding by infected persons in the catchment area, although many uncertainties come with such an appraisal: rose et al. (2015) report a mean amount of feces probably depending on factors such as the stage of infection, and are given in the range of 10 2 -10 8 gene copies per g feces . wölfel et al. (2020) showed the development of gene copy findings on the time course of the infection. with, e.g., 100 infected persons in a sampled catchment, these assumptions would yield a viral load in a range as broad as 10 6 -10 12 gene copies per d in the wastewater. the findings, as shown in figure 8 , are within but on the upper end of this broad range. few studies have evaluated the fate of coronaviruses and other enveloped viruses in wastewater treatment and surface water (gundy et al. 2009 , ye et al. 2016 . in a recent review by kitajima et al. (2020) , it is stated that currently no applicable dose-response models exist for sars-cov-2, which would allow for a better risk assessment. in a recent review by foladori et al. (2020) , the current knowledge about the fate of sars-cov-2 in wastewater treatment systems was summarized, and the few studies undertaken indicate that there is a significant reduction in viral load through the treatment process, but still, gene fragments are detectable in effluents. although it cannot be excluded with the current testing system of rt-qpcr targeting sars-cov-2 genes that virus emitted in large quantities is still infectious, studies analyzing sars-cov-2 environmental stability support the suggestion that infectivity and replication-competence of released viral particles are very unlikely , van doremalen et al. 2020 . based on our findings, we conclude the following:  sars-cov-2 rna was detected in the inflow of all 9 studied wwtp at concentrations similar to those reported in other studies. our screening of different target genes points to shortcomings in the selectivity of gene primers used in studies previously published by other authors that might also detect genes non-specific to sars-cov-2 viruses.  using sanger sequencing, we confirmed human sars-cov-2 for the investigated sample taken during the sars-cov-2 pandemic outbreak. in contrast, positive signals in rt-qpcr were not  quantification of sars-cov-2 gene concentrations and loads in wastewater needs to consider both aqueous and solid-phase sars-cov-2 detection methods and establish robust standard protocols for clean-up and rt-qpcr measurements.  we observed poor removal of sars-cov-2 in all three of the studied conventional activatedsludge wwtp. full-scale ozonation at one plant seemed to reduce sars-cov-2 fragments in the effluent. membrane-based wwtp planned to be included in future studies.  we found that the total load of gene equivalents in wastewater correlated with the cumulative and the acute number of covid-19 cases reported in the respective catchment areas. we consider load-based correlations superior to gene copy concentration-based approaches. analysis of suitable bioindicators in the wastewater may improve the assessment of sars-cov-2 loads data in catchment areas.  while our results indicate that rna fragments are not infectious to caco-2 cells in cell culturebased assays, further studies are needed to evaluate the risk sars-cov-2 may pose in the water cycle. it is recommended to further develop and implement the concept of wastewater-based epidemiology as a complementary measure to survey the outbreak of the sars-cov-2 pandemic and impose catchment-specific measures if necessary. j o u r n a l p r e -p r o o f highlights:  the first study that reports the detection of sars-cov-2 in wastewater in germany using rt-qpcr.  the presence of sars-cov-2 was confirmed by sequencing, but also the risk of false-positive results has been elucidated.  in raw wastewater, 3.0 to 20 gene equivalents per ml were found in raw wastewater.  the replication potential tests were negative for wastewater samples.  sanger sequencing was required to 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sars-cov-2 in wastewater: potential health risk, but also data source presence of sars-coronavirus-2 rna in sewage and correlation with reported covid-19 prevalence in the early stage of the epidemic in the netherlands wastewater engineering : treatment and reuse editorial perspectives: 2019 novel coronavirus (sars-cov-2): what is its fate in urban water cycle and how can the water research community respond temporal detection and phylogenetic assessment of sars-cov-2 in municipal wastewater. preprint not yet peer reviewed asymptomatic cases in a family cluster with sars cov-2 infection concentration of viruses and dissolved dna from aquatic environments by vortex flow filtration sars-cov-2 rna titers in wastewater anticipated covid-19 occurrence in a low prevalence area presence and vitality of sars-cov-2 virus in wastewaters and rivers analysis of the evolution in the circulation of hav and hev in eastern spain by testing urban sewage samples the characterization of feces and urine: a review of the literature to inform advanced treatment technology pcr inhibitors-occurrence, properties and removal first detection of sars-cov-2 rna in wastewater in north america: a study in louisiana on the origin and continuing evolution of sars-cov-2 optimized rt-qpcr approach for the detection of intra-and extra-cellular sars-cov-2 rnas aerosol and surface stability of sars-cov-2 as compared with sars-cov-1 water, sanitation, hygiene, and waste management for the covid-19 virus. interim guidance virological assessment of hospitalized patients with covid-2019 prolonged presence of sars-cov-2 viral rna in faecal samples sars-cov-2 titers in wastewater are higher than expected from clinically confirmed cases evaluation o flockdown impact on sars-cov-2 dynamics through viral genome quantification in paris wastewaters clinical findings in a group of patients infected with the 2019 novel coronavirus (sars-cov-2) outside of wuhan, china: retrospective case series survivability, partitioning, and recovery of enveloped viruses in untreated municipal wastewater we thank the water boards emschergenossenschaft und lippeverband (eglv), erftverband, linksniederrheinische entwässerungs-genossenschaft (lineg), niersverband, ruhrverband, and wasserverband eifel-rur (wver) for their participation in the sampling campaign on short notice and for ongoing support to fiw e.v. in difficult times. we acknowledge the work of all water-sector and health-care personnel for their continued service to society throughout the pandemics. m.b. was supported through the global water futures (gwf) program that is funded through the canada first research excellence fund (cfref). key: cord-314992-vhjuus50 authors: matthews, blake; jokela, jukka; narwani, anita; räsänen, katja; pomati, francesco; altermatt, florian; spaak, piet; robinson, christopher t.; vorburger, christoph title: on biological evolution and environmental solutions date: 2020-07-01 journal: sci total environ doi: 10.1016/j.scitotenv.2020.138194 sha: doc_id: 314992 cord_uid: vhjuus50 drawing insights from multiple disciplines is essential for finding integrative solutions that are required to tackle complex environmental problems. human activities are causing unprecedented influence on global ecosystems, culminating in the loss of species and fundamental changes in the selective environments of organisms across the tree of life. our collective understanding about biological evolution can help identify and mitigate many of the environmental problems in the anthropocene. to this end, we propose a stronger integration of environmental sciences with evolutionary biology. all ecosystems, be they natural or engineered, contain biological organisms that are bound by the principles of biological evolution. as such, biological evolution is often a central feature of many problems that are currently being tackled by environmental scientists. yet fundamental principles from the discipline of evolutionary biology are rarely used in the analysis and mitigation of environmental problems, even when evolutionary processes are closely linked to their manifestation (carroll et al., 2014; jørgensen et al., 2019) . environmental scientists are particularly adept at reaching across disciplines to ensure that they have the knowledge and tools necessary to tackle complex environmental problems. here we propose that a wider application of principles of science of the total environment 724 (2020) 138194 ⁎ corresponding authors at: eawag, department of aquatic ecology, überlandstr. 133, 8600 dübendorf, switzerland. url's: blake.matthews@eawag.ch (b. matthews), christoph.vorburger@eawag.ch (c. vorburger). evolutionary biology would help us achieve more sustainable solutions to environmental problems. in brief, evolution is a process of heritable change in the phenotype of a population of organisms (box 1). while evolution can result from random genetic drift (representing "neutral" evolution), here we focus on adaptive evolution, defined as a change in population mean fitness in response to natural selection (box 1). genetic and trait variation, and how such variation changes over time and space, are fundamental properties of living systems. there is mounting evidence that evolution is sufficiently fast in natural populations to be highly relevant for understanding how populations will respond to human-mediated environmental change (hendry and kinnison, 1999; hendry, 2017) . applying evolutionary principles to understand environmental problems is not a novel idea (gunderson and holling, 2002, santamaria and mendez, 2012) , but widespread application is still limited (jørgensen et al., 2019) . in the context of the biodiversity crisis ecologists are increasingly using evolutionary theory to help mitigate the https://doi.org/10.1016/j.scitotenv.2020.138194 0048-9697/© 2020 elsevier b.v. all rights reserved. science of the total environment j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / s c i t o t e n v loss of genetic and species diversity due to climate change and environmental pollution (bell and gonzalez, 2009; kristensen et al., 2018) . evolutionary theory is also critical to understanding the emergence of antibiotic resistance in microbes (palmer and kishony, 2013) and chemical resistance in pests (fisher et al., 2018) . plainly, evolutionary theory can be highly relevant to pertinent environmental problems, but it is not broadly applied. there is a frequent use of methods and technologies originating from evolutionary biology. in particular, molecular genetic methods are often used to characterise microbial community composition (das and dash, 2019) , and the patterns of gene expression of individual organisms and communities (oziolor et al., 2017) . while such methods are undeniably useful to gain functional insights, they are rarely used in environmental science to study evolutionary processes. the potential for evolutionary applications in environmental sciences is far reaching, and in the next sections we focus on core concepts of evolution and exemplify how they can be applied to a range of environmental problems in aquatic ecosystems. the structure and rate of change of heritable trait variation in living systems are particularly relevant for understanding environmental problems. living systems are hierarchically structured, where the traits of individuals arise from the interpretation of the environment by genes (so called genotype-phenotype maps; (houle et al., 2010) ). individuals interact within populations, where average trait values change through evolutionary and environmental processes (burns, 1992; frank, 2011; pedersen and tuomi, 1995) , and populations interact and evolve within multi-species communities (weber et al., 2017) . as a result of this hierarchical structure, human activities affecting one level of biological organization can have unanticipated outcomes at another level (gunderson and holling, 2002; melián et al., 2018) . for example, human activities that affect gene flow among populations can lead to the introduction of either beneficial alleles that help populations adapt to changing environments, or deleterious alleles that contribute to maladaptation of natural populations and thereby can potentially hinder conservation efforts (leitwein et al., 2019) . despite the long held view that evolution is a slow process, it is now well established that the pace of heritable trait change can be sufficiently fast to affect population dynamics, species interactions, and ecosystem processes -i.e. evolution can act at ecological time scales (hairston et al., 2005; stockwell et al., 2003) . the dynamics of species interactions in natural communities are hence not simply a product of past evolution. rather, evolutionary processes can shape trait distributions of populations (i.e. mean and variance) at a pace that is highly relevant for many environmental problems. evolutionary processes can either ameliorate or exacerbate environmental problems. evolutionary adaptation, for example, can drive the recovery of populations, or even multi-species communities, from decline, in a process known as "evolutionary rescue" (bell and gonzalez, 2009; low-décarie et al., 2015) . in natural populations, evolution has rescued killifish from chemical pollution (whitehead et al., 2017) and amphibians from acidification (hangartner et al., 2012) . in these cases, genetic adaptation has allowed for the persistence of populations in environments that would otherwise be unsuitable. evolutionary novelty can also emerge in populations exposed to synthetic environments created by humans, and, in doing so, perform essential evosystem services (rudman et al., 2017) . for example, the artificial sweetener acesulfame (ace) is a persistent compound in aquatic environments because it is resistant to microbial-mediated biodegradation both in natural and wastewater treatment environments (kahl et al., 2018) . recent work suggests that the catabolism of this compound has evolved repeatedly in multiple wastewater treatment plants in germany (kahl et al., 2018) , possibly associated with a microbial consortium of proteobacterial species (fig. 1) . identifying the evolutionary processes governing such bioremediation dynamics could help address the persistence of chemicals in our natural environments for which engineering solutions are lacking. on the other hand, evolutionary processes can also create novel environmental problems, or worsen existing ones. for example, the emergence and amplification of antibiotic resistance genes is a global problem, caused by the widespread overuse of antibiotics (palmer and kishony, 2013) . in wastewater treatment plants, the concentration of antibiotic resistance genes may be amplified by evolution prior to water discharge into natural aquatic environments (ju et al., 2019) (fig. 1 ). understanding and monitoring the evolutionary process in wastewater treatment plants could improve our ability to limit the release of antibiotic resistance genes into natural environments (czekalski et al., 2015) . in this section, we illustrate how a broader application of evolutionary theory can enable environmental scientists to craft better solutions for environmental problems. to this end, we use four examples from aquatic systems: (i) emergence and epidemiology of disease, (ii) renewable production of biofuels, (iii) chemical pollution, and (iv) outbreaks of algal blooms. diseases are among the most severe environmental problems. they are a threat to biodiversity (fisher et al., 2018; lips et al., 2006) , to food production (strange and scott, 2005) and to human health (jones et al., 2008) . disease outbreaks are often caused by pathogens that have undergone a recent host shift or expansion of their geographic range (engering et al., 2013; longdon et al., 2014) . most disease-causing organisms have large populations and short generation times, which generally facilitates rapid evolution. consequently, disease emergence typically involves rapid co-evolutionary dynamics that stem from natural selection on both pathogen infectivity and host defense (penczykowski et al., 2016) . rapid evolutionary dynamics are expected to take place at the onset of disease emergence, governed by the pathogens' and the hosts' evolutionary history. disease emergence is often a consequence of human activities. transport between continents can bring pathogens into naïve host populations that are, at least initially, defenseless; they can lack sufficient genetic variation for resistance because they do not have coevolutionary history with these pathogens. the crayfish plague provides a good example. aphanomyces astaci, a pathogen of freshwater crayfish native to north america came to europe with introduced american crayfish (svoboda et al., 2017) . american crayfish species had evolved a high tolerance of the pathogen, due to their long evolutionary history, but the pathogen proved devastating to stocks of european freshwater crayfish species (holdich et al., 2009) . likewise, human activities that modify ecosystems for food production can promote the emergence of locally highly virulent pathogens (stukenbrock and mcdonald, 2008) . for example, large monocultures of genetically homogenous plants can facilitate the evolution of host specialization (mcdonald and stukenbrock, 2016) , leading to evolutionary dynamics that are not commonly observed in natural ecosystems. evolutionary theory can be instrumental in helping to understand the origin and spread of diseases through populations. increasingly, researchers can track disease dynamics over time by comparing genetic variation among isolates, and such data can help inform policy decision and management of viral diseases, such as covid-19 (andersen et al., 2020 , brüssow, 2020 and ebola (mbala-kingebeni et al., 2019) . drug treatment is often the default approach used to control emergent bacterial and fungal diseases, but in some cases a single new drug can cause strong natural selection, and, combined with the high evolutionary potential of pathogens, this means that the expected time until drug resistance evolves can be short (fisher et al., 2018; kennedy and read, 2018) . for such scenarios, we need to develop evolution-aware strategies to avoid and control emergent diseases. for example, in the case of chemical treatments, combination therapy or the sequential application of different drugs can delay resistance evolution (palmer and kishony, 2013; roemhild et al., 2018) , and the development of 'evolution-proof' drugs is a particularly attractive idea (bell and maclean, 2018) . alternative strategies include fighting the disease with agents that are able to evolve themselves, such as microbial symbionts that provide protection against the disease (kueneman et al., 2016) . the dwindling supply and the negative environmental impact of fossil fuels have spurred substantial research and investment into using biofuels as a renewable and sustainable source of energy (sheehan et al., 1998) . among the many potential sources of biomass for biofuels, phytoplankton or "algal" biofuels are among the most efficient in terms of land-use and energy production per unit biomass (y. chisti, 2008; yusuf chisti, 2007) . until now, algal biomass production for biofuel has heavily focused on the production of single species with desirable properties, namely high lipid content, fast growth rates, and resistance to disease and grazers. however, farming monocultures is notoriously difficult because individual species or strains, be they algae or crops, can never possess all of the desirable traits for long-term stable crop production at high yields (smith et al., 2010) . the ideal species for maximum production would be unconstrained by the trade-offs inherent to all living systems. yet such omnipotent organisms, known in evolutionary biology as darwinian demons (krakauer, 2011; law, 1979) , do not exist and cannot be engineered. nevertheless, sustainable yield of biofuels could be optimized by understanding the biochemical and biophysical basis of the fundamental trade-offs between growth rate, lipid production and traits that make better competitors, confer resistance to parasites, and are resistant to grazers (shurin et al., 2013 (shurin et al., , 2016 ; t. yoshida et al., 2004) . understanding the evolution of ecologically relevant traits, under different biotic and abiotic contexts, may improve the stability and efficiency of biofuel production. the application of evolutionary theory to algal biofuel production is in its infancy, but holds immense potential. algal populations are large and have short generation times. usually the populations maintain high phenotypic and genetic diversity (brandenburg et al., 2018; chen and rynearson, 2016; lebret et al., 2012; masseret et al., 2009; rynearson and armbrust, 2000) . evolution in such populations can be fast if selection is strong (thibodeau et al., 2015; takehito yoshida et al., 2003) . harnessing the adaptive evolutionary potential of algal populations could help us explore the range of feasible trait space to obtain desirable trait combinations. for example, researchers are currently trying to simultaneously improve the yield of triacylglycerols in culture (used to produce fatty acid methyl esters needed used in biodiesel production), while concurrently maximizing population growth rates. such trait combinations are normally mutually exclusive. approaches include genetic engineering (zeng et al., 2011) , directed evolution via successive rounds of mutagenesis and selection (johnson et al., 2016; lewin et al., 2016) , and selection on the existing levels of genetic variation in a population (mooij et al., 2013; shurin et al., 2016) . while evolution might help us improve biofuel production (kazamia et al., 2014) , it might also culminate in undesirable outcomes. for example, engineering solutions based on evolutionary trade-offs might be eroded over time due to mutation, horizontal gene transfer, and recombination. custom designed biofuel production systems should also consider the evolutionary consequences of rapid harvesting. for example, rare beneficial mutations arising during population expansion, might be periodically lost before they sweep to dominance in the populations (bull and collins, 2012; shurin et al., 2016) . in short, evolution offers both promises and pitfalls for biofuel production. chemical pollution is a global problem with a local character (grimm et al., 2008; halpern et al., 2008; vörösmarty et al., 2010) . chemical pollution often stems from chemical pest control applied in agricultural production, as well as from the unwanted waste produced by human population growth and industrial activities. wastewater treatment plants can only remove and target compounds that pass through the sewage system; many other compounds still enter the natural environment in a diffuse manner, especially from agriculture. these chemical compounds can have toxic effects on individual organisms and these effects can be enhanced when they occur in mixtures (abdelghani et al., 1997; connon et al., 2012) . for instance, pest control requires highly biologically active substances to target unwanted algae, fungi and arthropods. when pesticides then leak into ecosystems that are not the target of the application, this can change food web structure and influence ecosystem function (stamm et al., 2016) . because pollution and the ecological context in which pollution occurs is often highly local, we can expect pollution to have many different evolutionary consequences in natural ecosystems. however, the biological effects of pollutants are typically studied using a limited number of model species and strains, usually in oversimplified ecological contexts that might underestimate their effects in nature (relyea and hoverman, 2006) . furthermore, many of the approaches used in environmental science and ecotoxicology to assess the environmental effects of pollutants only test a few selected genetic lineages of organisms (e.g., single strains of daphnia), and often ignore both within-population variation in sensitivity to pollutants and the effects of mixtures of pollutants on organisms. for example, morphologically similar but genetically distinct lineages of amphipods, within the gammarus fossarum cryptic species complex, vary in their sensitivity to the fungicide tebuconazole and the insecticide thiacloprid (feckler et al., 2012) . such lineage diversity within species is rarely accounted for in typical assessments of pollutants on organisms (relyea and hoverman, 2006) . synthetic chemicals present a particular challenge because the exposed organisms may lack the exposure history necessary for the emergence of an evolutionary adaptation. synthetic chemicals can also act as mutagens that disrupt the homeostasis of organisms (bickham et al., 2000) . chemical toxicity can rapidly drive populations to such small sizes that their persistence over time becomes threatened (williams and oleksiak, 2008) . interestingly many classic studies about rapid evolution involve chemical pollution, such as the evolution of resistance to pesticides, resistance to antibiotics or mining-related metal pollution (hoffmann and parsons, 1997; palumbi, 2009 ) and, more recently, pollutant induced elevated mutation rates and rapid adaptation (brady et al., 2017; coutellec and barata, 2013; kimberly and salice, 2012; loria et al., 2019; palumbi, 2009) . evolutionary adaptation to chemical pollution can also rescue populations from extinction caused by demographic decline. for example, experimental daphnia populations that were initially highly sensitive to metal contamination recovered rapidly via genetic adaptation (hochmuth et al., 2015) . in another example, natural killifish populations inhabiting urban estuaries adapted to lethal levels of pollutants with genetic adaptations (oziolor et al., 2017; reid et al., 2016) . unsurprisingly, adaptation of a population can also be an unwanted outcome of management, such as when the evolution of resistance reduces the sensitivity of a species used in ecological risk assessment (morgan et al., 2007) . evolution's ability to alter the direction of responses to environmental change, such as that brought by chemical pollution, is one of the main arguments for including evolutionary concepts in environmental research. finally, potential for evolutionarily based solutions to pollution comes from implementing bioremediation, such as designing microbial communities that have evolved the ability of biodegradation of chemicals (liu and suflita, 1993) . harmful algal blooms are often associated with eutrophication, pollution and climate change (huisman et al., 2018; monchamp et al., 2018) . harmful algal blooms, which can persist for weeks or months, may foul drinking water, turn lakes anoxic and kill fish, and render lakes unacceptable for recreational use (lewitus et al., 2012; paerl et al., 2011) . ecological theory suggests that blooms develop when nutrient input releases phytoplankton from control by grazers (abrams and walters, 1996; gragnani et al., 1999; pančić and kiørboe, 2018) . additionally, evolutionary processes are also relevant to the emergence, volume and toxicity of blooms. indeed, we postulate that trying to manage harmful blooms without darwin, is like trying to fly to the moon without newton (modifying andrew read's concluding remark on his tedmed talk on importance of evolutionary medicine: https://www. tedmed.com/talks/show?id=7286). the trade-off between resource uptake and grazing resistance is at the root of the ecological and evolutionary causes of bloom biomass (cloern, 2018) . selective grazing by zooplankton will deplete edible algae and, subsequently, increase the abundance of well-defended algae (hairston et al., 2005; takehito yoshida et al., 2003) . harmful algal blooms are characterised by an array of defense traits that are favored by natural selection. some algae produce compounds that are toxic to grazers, such as the neurotoxins, saxitoxins and domoic acid produced by dinoflagellates, cyanobacteria, and diatoms, respectively (pančić and kiørboe, 2018; xu and kiørboe, 2018) . remarkably, toxin production varies widely both within and among populations. for example, some lineages entirely lack the genes for toxin production (brandenburg et al., 2018; briand et al., 2009 ). the evolutionary dynamics of different toxic/non-toxic genotypes during algal blooms is likely driven by physiological trade-offs between costs of toxin production and resource uptake for growth (brandenburg et al., 2018; cadier et al., 2019; chakraborty et al., 2019; kiørboe and andersen, 2019) . such defense-growth trade-offs are likely important for the emergence of harmful algal blooms (burford et al., 2019; jankowiak et al., 2019; kim et al., 2010; li et al., 2012) , but the selective factors that favor toxic variants in bloom forming algae are not fully understood. identifying the evolutionary processes involved in algal blooms would likely help us predict which algal blooms might turn toxic. in a first step, reliable prediction would enable the avoidance of risks associated with toxic algal blooms (e.g. by timely establishment of exclusion zones), and in a second step, it could inform mitigation measures to reduce the occurrence of algal blooms (e.g. by influencing relevant selective forces such as nutrient input). evolutionary processes are often an inescapable and critical component of both understanding and solving environmental problems. the evolution of resistance genes will continually challenge our efforts to halt diseases through the development of new drugs, highlighting the need to complement efforts in drug discovery with the development of evolution-aware application strategies. a better appreciation of evolution's limits and, in particular, the impossibility of darwinian demons, is critical to meeting our energy demands by matching algal genotypes with optimal environmental conditions for biofuel production. in a similar vein, choosing strains that have evolved tolerance to pollutants might help sustain populations in deteriorating environments, while strains naive to pollution might be a more conservative option when assessing ecological risk to chemical pollutants. engineering solutions in waste-water treatment plants might be improved if we could harness evolution's power to help biodegrade persistent compounds (brenner et al., 2008) . other environmental problems with limited engineering-oriented solutions could be tackled with evolutionary perspectives. for example, biocides may be applied to combat algal blooms, but it is notoriously difficult to predict the timing, duration and toxicity of algal blooms. a better understanding of the evolutionary dynamics of such systems, gained, for example, by tracking environmental change in real-time and linking those changes with environmental sources of natural selection, could help us predict the outbreaks of toxic algae. indeed, there is a growing need in many areas of environmental science to efficiently forecast ecosystem change across natural and human-induced gradients (petchey et al., 2015) and to understand the consequences of such changes for ecosystem (and evosystem) services (costanza et al., 1997; rudman et al., 2017) . this is particularly relevant for ecosystems that provide vital services to society, but are also sensitive to anthropogenic impacts. predictions about complex ecological systems are challenging and require solid understanding of ecological and evolutionary mechanisms behind population growth, genetic and trait diversity, trait-environmental relationships, trade-offs, and community dynamics. such principles are present in the environmental science literature, but are only sporadically applied to solve environmental issues. it is possible that prevailing misconceptions about the pace and prevalence of evolution may be blocking the integration of evolution into the environmental sciences. first, the pace of evolutionary adaptation is not only set by the rate of mutations and the subsequent rate of increase of novel alleles in the population. instead, the rate of adaptation, i.e. the increase in mean population fitness over time, is directly proportional to the genetic variance in a population that can respond to natural selection (fisher, 1930) . evolution from existing levels of heritable trait variation in a population can be much quicker and more predictable than expected based on evolution driven via new variants in the population that arise solely by mutation. second, evolution is neither rare nor a special case. the challenge for environmental science is to determine the relative importance of evolution, either for causing or for ameliorating a particular environmental problem. overall, we argue that evolutionary principles are a useful resource for coming up with solutions to environmental problems. on the one hand, seemingly rational solutions might require some 'evolution proofing' to effectively anticipate and limit any potential negative impacts of evolution on the expected outcomes of our interventions. on the other hand, evolution itself can be a powerful design strategy for solving environmental problems. design by directed evolution, for example, has made considerable progress developing novel enzymes (arnold, 1998) , and configuring communities to perform specific functions that improve environmental conditions (ghoul and mitri, 2016) . natural selection is a powerful force that can efficiently explore the the four forces of evolution. mutations are random, heritable changes in the sequence or structure of a gene. they include substitutions of individual bases in the dna sequence, insertions and deletions of dna fragments, and structural rearrangements of chromosomes. new variants of the same gene generated by mutation are referred to as alleles. mutations can be neutral, meaning they do not affect the phenotype of their carrier, advantageous in specific environments, meaning they affect the phenotype such that it increases survival and/or reproduction, i.e. fitness, or deleterious in specific environments. for example, a mutation that confers resistance to a pesticide may be beneficial in an environment where the pesticide is present but detrimental in an environment where the pesticide is absent. mutations are the ultimate source of genetic variation and provide the original resource for adaptive evolution and biological innovation. natural selection is the process of unequal survival and reproduction among individuals due to differences in phenotype. some individuals of the population are more likely to survive and reproduce because they have trait combinations that make them better at coping with the current environment than other individuals. assuming that the phenotypic traits under selection are heritable, i.e. trait values are transmitted across generations, the favorable traits, which represent 'good genes', will be passed to the offspring. in this way, the frequency of the 'good' gene variants will increase in the population, leading to evolutionary adaptation. gene flow gene flow is the exchange of genetic material between populations. it occurs when individuals or their gametes migrate into a new population and reproduce. gene flow can bring new alleles (i.e. genetic variants) into the receiving population and thereby influence the potential for this population to evolve. gene flow can be maladaptive, and reduce the fitness of the local population, or adaptive. if migration is sufficiently high and migrant genes are not selected against, gene flow will homogenize allele frequencies and reduce genetic differences in the genetic composition of populations. genetic drift is the stochastic change in allele frequencies over generations. it occurs because allele frequencies in populations can deviate by chance from those of the parental generation, due to the random sampling of gametes. it affects particularly small populations. it can lead to the loss of genetic variation and the accumulation of deleterious mutations and, as a result, constrain a population's adaptation to changing environmental conditions. combinatorial trait space that organisms could theoretically occupy. the trait space of living systems is replete with opportunities to solve environmental problems, and natural selection might often outpace our own ability to find these solutions. perhaps a way forward is to relinquish our engineering hubris in favor of a problem solving strategy that is either informed by, or directed by, evolution. environmental science has a rich history of interdisciplinarity. a 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biodiesel from algae industrial-strength ecology: trade-offs and opportunities in algal biofuel production recent progress and future challenges in algal biofuel production the ecology of algal biodiesel production chapter four -unravelling the impacts of micropollutants in aquatic ecosystems: interdisciplinary studies at the interface of large-scale ecology contemporary evolution meets conservation biology plant disease: a threat to global food security the origins of plant pathogens in agroecosystems hosts and transmission of the crayfish plague pathogen aphanomyces astaci: a review rapid eco-evolutionary responses in perturbed phytoplankton communities global threats to human water security and river biodiversity evolution in a community context: on integrating ecological interactions and macroevolution when evolution is the solution to pollution: key principles, and lessons from rapid repeated adaptation of killifish (fundulus heteroclitus) populations signatures of selection in natural populations adapted to chronic pollution toxic dinoflagellates produce true grazer deterrents rapid evolution drives ecological dynamics in a predator-prey system evolutionary trade-off between defence against grazing and competitive ability in a simple unicellular alga, chlorella vulgaris microalgae bioengineering: from co 2 fixation to biofuel production this manuscript was supported by internal eawag funds and an swiss national science foundation [grant number 31003a_175614] to bm. we thank arianne maniglia, and gioia matheson for help in organising the workshop that supported this project, and paula ramsay for editing. key: cord-312619-7jpf81yz authors: ilyas, sadia; srivastava, rajiv ranjan; kim, hyunjung title: disinfection technology and strategies for covid-19 hospital and bio-medical waste management date: 2020-08-12 journal: sci total environ doi: 10.1016/j.scitotenv.2020.141652 sha: doc_id: 312619 cord_uid: 7jpf81yz abstract the isolation wards, institutional quarantine centers, and home quarantine are generating a huge amount of bio-medical waste (bmw) worldwide since the outbreak of novel coronavirus disease-2019 (covid-19). the personal protective equipment, testing kits, surgical facemasks, and nitrile gloves are the major contributors to waste volume. discharge of a new category of bmw (covid-waste) is of great global concern to public health and environmental sustainability if handled inappropriately. it may cause exponential spreading of this fatal disease as waste acts as a vector for sars-cov-2, which survives up to 7 days on covid-waste (like facemasks). proper disposal of covid-waste is therefore immediately requires to lower the threat of pandemic spread and for sustainable management of the environmental hazards. henceforth, in the present article, disinfection technologies for handling covid-waste from its separate collection to various physical and chemical treatment steps have been reviewed. furthermore, policy briefs on the global initiatives for covid-waste management including the applications of different disinfection techniques have also been discussed with some potential examples effectively applied to reduce both health and environmental risks. this article can be of great significance to the strategy development for preventing/controlling the pandemic of similar episodes in the future. treated properly. since the pandemic outbreak, south korea has generated about 2,000 tons of covid-waste until the starting of may 2020 (escap, 2020) . moreover, an increase in ppe supplies by 40% per month from the current compounded annual growth rate (cagr) of 6.5% is projected (market reports, 2019) . the demand for ppe including the facemasks and surgical gloves are not expected to decline during the post-pandemic period and estimated a 20% cagr up to 2025 (who, 2020 . the drastic increasing number of regions/countries/people infected with sars-cov-2 has indicated that the world will overrun by covid-waste and the outcome of this glut will have a deep impact on sustainable waste management practices in the coming years (cutler, 2020) . the resilience of our society and waste management practices are under tests with the stability reports of sars-cov-2 (kampf et al., 2020) . the traces of this virus has been observed on plastics for 6.8 hours, stainless steel for 5.6 hours (van doremalen et al., 2020) , and the outer layer of surgical mask up to 7 days albeit a lower cell density of about 0.1% of the original inoculum (chin et al., 2020) . it clearly indicates that covid-waste (like needles and syringes used for blood samples, surgical facemasks, and ppe) can have a longer persistence of sars-cov-2. virus transmissions from the contaminated dry surfaces have been postulated including selfinoculation of mucous membranes of the eyes, nose, and mouth (otter et al., 2016) . the exposure to covid-waste may potentially increase the virus spread by increasing the reproductive number (r 0 ) from its determined range between 2.2 to 3.58 thus, effective management of covid-waste including the appropriate disinfect and disposal techniques are necessary to control the pandemic spread, which has not been focused yet albeit posing a similar threat as sars-cov-2 itself can have to the public health. the present article reviews the disinfection technologies to control/prevent the novel coronavirus spread and the proper management of covid-waste including the effective strategies and reprocessing possibilities of the used items. to outline this review paper on the topic presented herein, the first step was to extract articles using the initial keyword "disinfection technology, strategies, and management of covid-19 hospital waste and bio-medical waste". with the initial keyword searched in the scopus database, a total 61,442 results appeared (that included 2,705 journals; 46,875 books; and 11,862 webpages) albeit mostly belong to the common bmw and not the covid-waste. a further change in keywords like "covid-waste management" (611 journals and 5,024 webpages); "disinfection of covid-waste" (2,652 journals and 11,311 webpages); and "management strategies for covid-waste" (2,361 journals and 10,967 webpages) were also searched. notably, no books were found to exist until the search date (may 6, 2020) on covid-19 waste; whereas, the reports and data published in webpages were found informative to shape this review article. therefore, the search engine like google was also used to fetch the recent information and developments on the handling of covid-waste worldwide with different keywords as stated above. to ensure relevance to the topic of this review article, 142 items were manually screened out by keywords, title, abstract, and when unsure, by assessing the full text. finally, excluding studies did not focus on covid-19 waste, 51 items were found relevant and referred along with personal communication with bgl private ltd. the materials like acr plus (2020), barcelo (2020) , datta et al. (2018) , j o u r n a l p r e -p r o o f journal pre-proof escap (2020), shereen et al. (2020) , wang et al (2020) and time-to-time guidelines given by who and cpcb (2020a , 2020b , 2020c were particularly helpful in this context. the personal information gathered from the bio genetic laboratories (bgl) private ltd. (india) and ministry of environment (south korea) were much useful to understand the entire scenario and real-time system on disinfection techniques for covid-waste and their management practices. classification of hospital waste is the first step for the management of covid-waste (refer fig. 2 ). it is the best practice that the waste is classified at its origin. this strategy is not only time-efficient but also avoids the chances of infection spread to other handlers of the waste. the collection of covid-waste in separate bags/bins is directed to have a clear marking over the dedicated bins. at the time of waste classification, the waste containing bags must be disinfected and sealed in double-layered plastic bags (usually yellow color) prior to transportation from the originated place/ward. commonly, the bmw contains about 85% of general non-infectious waste, 10% of infectious hazardous waste, and 5% of radioactive and/or, chemical waste (datta et al., 2018; who, 2014; who health-care waste, 2018) . all covid-waste comes under the hazardous bmw. once identified, the segregation becomes an easy task for their separate storage from where the waste can be collected on a priority basis and within the deadlines. while doing so, proper disinfection of the storage area and the transporting vehicles carrying covid-waste to common bio-medical waste treatment and disposal facility (cbmwtf) becomes necessary. for the disinfection of covid-waste, various factors like the quantity and type of waste, costs, and maintenance are considered for selecting the appropriate disinfection technology (as shown in fig. 3 ). it suggests that j o u r n a l p r e -p r o o f journal pre-proof incineration at higher/lower temperature can be adopted on the basis of waste volume to be treated and the investment capacity. else if, the operational scale of a hospital is smaller with limited investment that cannot afford the installation and maintenance costs of incinerator, the chemical disinfectant (as front disinfection technique) in combination with microwave and steam disinfection technique at the latter stage and relatively a lower temperatures (between 93-540 °c) over incineration (usually at 800-1200 °c) can be preferred. a comprehensive discussion on each disinfection and disposal technology has been presented below. incineration is based on high-temperature combustion range between 800 °c to 1200 °c that completely kills the pathogen and potentially burns up to 90% organic matters (datta et al., 2018; wang et al., 2020) . as per the bgl private ltd. (a common bio-medical waste treatment facility approved by the jharkhand pollution control board, india), the most of the covid-waste are sent to incinerate at a temperature > 1100 °c. sometimes, the residual mass is re-incinerated with fresh charge depending upon the volume reduction of covidwaste. as shared by bgl, a number of toxins are produced in-situ like furan and dioxins have a high tendency to accumulate in fatty tissues and cause damage to the immune and endocrine system. therefore, the flue-gas treatment facility is also required with the incineration facility that costs additional burden to the operator. consequently, running the facility with small quantity is somehow not viable and alternative technologies are applied. j o u r n a l p r e -p r o o f there are mainly two types of alternative thermal technology available and in-practice to deal with covid-waste, which are: (i) high-temperature pyrolysis technique, and (ii) medium-temperature microwave technique. pyrolysis is technologically sound technique than incineration. it usually operates in the temperature range of 540-830 °c that includes pyrolysis-oxidation, plasma pyrolysis, induction-based pyrolysis, and laser-based pyrolysis (datta et al., 2018) . in a pyrolysisoxidation, the air measured below the theoretical chemical reaction is supplied to a fixed level of the primary combustion chamber. wherein, the organic solid and liquid waste is vaporized at a temperature of ~600 °c under the air turbulence that leaves the residual ash, glass, and metallic fragments. in the second step of combustion, the flammable gaseous vapor is combusted in a chamber at a higher temperature ranges between 982 °c to 1093 °c to the complete destruction of toxic substances like dioxins, releasing the clean exhaust steam. looking at the rapid spread potential of sars-cov-2, using plasma-energy for a quick decomposition of covid-waste is recommended than usual laser/gaseous combustion . low emission rate, inert residual, volume reduction up to 95%, and mass reduction up to 90% have been observed with this technique. this technique operates under the temperature range from 177 °c to 540 °c and includes reverse polymerization by applying the high-energy microwaves under an inert atmosphere for breaking down the organic matters. the absorption of electromagnetic waves (with a wavelength of 1 mm to 1 m in the frequency of hundreds of megahertz to 3,000 mhz) increases the internal energy as the resultant vibration and rubbing of molecules. however, an j o u r n a l p r e -p r o o f journal pre-proof inert environment created by nitrogen prohibits the combustion with oxygen to exhibit the high-temperature disinfection. relatively lower energy and action temperature, limited heat loss, and less environmental burden with no toxic residue after the disinfection process are the main advantages of microwave technique. the specially designed microwave devices under strictly controlled process can prominently inactivate sars-cov-2. according to the report of chinese ministry of ecology and environment, this disinfection technique can achieve the logarithmic values of killing the hydrophilic viruses ) and identified to be much helpful for an on-site disinfection of covid-waste. the on-site disinfection avoids the risks posed by covid-waste transportation that also saves time (resilient environmental solutions, 2020) . in the case of disinfection to covid-waste, the microwave technique is also used in combination with autoclaving where steam is used for sterilization (in temperature range from 93-177 °c). the chemical disinfection technique is widely applied to pre-treat covid-waste in combination with a prior mechanical shredding. the exhausted air is passed through high efficiency particulate absolute filter to safeguard against aerosol formation during the shredding. the crushed waste volume are further mixed with chemical disinfectants and kept in a closed system and/or, under the negative pressure for a given time. in this process, the organic substances are decomposed and the infectious microorganisms are inactivated or killed. the application of low effective concentration, stable performance, rapid action, and broad sterilization spectrum along with no residual hazards are the major advantages to use the chemical disinfectants as they not only effectively kill the microorganisms but also inactivate the bacterial spores . the chemical treatment of covid-waste can be sub-divided into chlorine-and nonchlorine-based systems. in a chlorine-based j o u r n a l p r e -p r o o f treatment system, naocl or clo 2 is used as the disinfectant media, where the electronegativity of chlorine helps in oxidizing peptide links and denaturing proteins that follows penetration of cell layers even at neutral ph. in fact, naocl is one of the first chemical disinfectants which releases the halo acetic acid, dioxins, and chlorinated aromatic compounds. later, the use of clo 2 increased which is a strong biocide, however, due to its unstable nature, it is used on-site. moreover, it decomposes to form salt and less-toxic products which are non-reactive to alcohol/ammonia. on the other hand, h 2 o 2 is commonly used as the disinfectant media in a nonchlorine-based treatment system. it acts to oxidize and denature proteins and lipids, consequently causing disorganization of the membrane via swelling of the saturated h + -ions. high reactiveness and no toxicity associated with the chlorinated system is advantageous to use this system. chemical solutions like povidoneiodine (> 0.23%), formaldehyde (> 0.7%), isopropanol (> 70%), and ethyl alcohol (> 75%) can also inactivate sars-cov-2 (duarte and santana, 2020). notably, the potential use of disinfection technology cannot be limited to only a safety measure but its importance is much greater due to the global shortcomings in supply chain of personal protectives after the outbreak of covid-19 (barcelo, 2020) . consequently, impromptu techniques for recycling of used personal protectives are underway in some countries, albeit the high health-risk is associated due to improper decontamination (mallapur, 2020; singh et al., 2020) . hence, the effective disinfection technique is also required in terms of reprocessing of personal protectives. due to heat-sensitive properties, the aforementioned high-temperature disinfection techniques are not suitable that leads to reprocessing; whereas, the most prominent chemical disinfectant spray is found to degrade the inherent properties of personal protectives (rowan and laffey, 2020) . instead of using the aqueous disinfectant j o u r n a l p r e -p r o o f solution, the use of vaporized hydrogen peroxide (vh 2 o 2 ) has shown some encouraging results at sterilizing bacteria, prions, and viruses (barcelo, 2020) . a key proposition of lowtemperature vh 2 o 2 is polymeric material compatibility, while the reduced processing time (from 10-15 hours using ethylene oxide to less than 6 hours in a typical vh 2 o 2 process) is an additional benefit which can be performed at atmospheric and in vacuum condition. however, compatibility with cellulose-based materials and ability to penetrate targeted surfaces are the limitations that have inhibited the application of vh 2 o 2 in large scale due to the reduction of h 2 o 2 strength in the presence of cellulose (mcevoy and rowan, 2019) . in a recent effort to disinfect n95 masks, price et al. (2020) have investigated (i) dry heat (using hot air at 75 °c for 30 minutes) and (ii) ultraviolet germicidal irradiation (uvgi, at 254 nm and 8 w for 30 minutes). the study revealed that hot air treated n95 masks applied over 5 cycles do not degrade the fit of masks (change in fit factor, 1.5%; p-value, 0.67), while uvgi treated n95 masks applied over 10 cycles significantly degrade in fit and do not pass quantitative fit testing using osha testing protocols on a human model (change in fit factor, -77.4%; pvalue, 0.0002). nevertheless, whether the decontamination works through all the layers of trapped virus in the particles is unanswered and imperative to know before ensuring the reprocessing of covid-waste. in order to draw a realistic impact of disinfection technologies, a summative strength, weakness, opportunity, and threat (swot) analysis are presented in table 1 . as can be seen, pyrolysis is advantageous because of no known threat to the complete destruction of waste volume. on the other hand, vh 2 o 2 and dry heat techniques have the opportunity for reprocessing of personal protectives (ppe and n95 masks) and their re-use. j o u r n a l p r e -p r o o f mask, gloves should be done sequentially in a semi-contaminated room. then only, the healthcare person can be allowed to enter the clean area after hand sanitization and wearing of a clean surgical mask. all the used items collected in this process must be collected as covid-waste (even after disinfectant spray) and processed for the next stage of treatment like incineration/microwave (as defined in section 4). soon after the first outbreak of covid-19 in south korea, the ministry of environment tightened the existing "wastes control act" by introducing "the extraordinary measures for safe waste management against covid-19" on january 28, 2020 (moe-rok, 2020a, 2020b). as per the new guidelines, covid-waste cannot be stored more than 24 hours and must be incinerated on the same day of collection; whereas, the earlier act was giving 7 days of storage time that can be incinerated within 2 days of delivery. under the extraordinary measures for covid-waste, the household waste generated by self-quarantined persons would also be treated as covid-waste (escap, 2020). the guidelines re-visited after raising the health alert to level 4 (on february 23, 2020) state that the waste generated by the home-quarantine patients would be stored in dedicated bags and containers after the disinfectant spray. if the patient has been found covid-19 positive, the stored waste must be kept close in the resin box (as the schematic is depicted in fig. 4a) . to treat the collected waste on a priority basis (within 24 hours), the local waste disposal facilities have been directed to first treat the medical waste generated by home-quarantine patients over other municipal waste. in this work, helps from the private waste collection parties has been asked by distributing over 84,000 sets of ppe and masks to the workers involved in this task (escap, 2020). until the mid of july, more than 2600 tons of medical waste were collected from 91 designated covid-hospitals, 8 residential centers, 24 temporary facilities, and selfquarantine households that was disposed of by incineration on a priority basis. not only the covid-waste generated by the hospitals, health centers, and self-quarantines, but the waste generated during the disinfection of public area or, where an infected person visited have been directed to treat as medical waste and collection of those waste in double-packed designated bags are mandatory before sending to burning at the high-temperature incinerator facility. the waste generated by the health workers and medical waste inspectors of covid-19 also designated as the same for a separate treatment. the prompt, flexible, and pointed actions to handle the covid-waste by the south korean government could avoid critical situations without any severe safety issues and viruses spread by medical waste. close monitoring of the quantity of covid-waste generation from home-quarantine, designated hospitals and healthcare centers have been found helpful to track their disposal and treatment within a fixed time period of 24 hours. intensive inspections by the local environmental agencies could ensure the strict following of disposal guidelines in designated bags and containers. moreover, a cooperation system developed for covid-waste management as depicted in fig. 4b could potentially contribute to drawing a simple decision-making process (moe-rok, 2020a, 2020b). the systematic and prioritized cooperation between the concerned agencies under the command of central headquarter of disaster and control of the ministry of environment and local governments are found to be helpful for tackling the challenges effectively. in the country of the first outbreak of covid-19, the generated healthcare and biomedical waste has overloaded the waste treatment facilities of china. the dreadful situation j o u r n a l p r e -p r o o f that arose due to covid-waste can be understood by the fact that the inadequate capacity to treat bmw has been a long-standing issue in china. as per the record in 2018, china produced more than 200 million tons of bmw, however, 76 cities were unable to a timely waste treatment (zuo, 2020) . the exact volume of covid-waste in the country is yet to be known; however, a known number of people infected (~0.1 million) and the generation of bmw (240 tons/day, a six-folds higher than earlier of covid-19 outbreak) at wuhan (cutler, 2020) and ~200 kg of discarded facemasks collected alone from the bins of wuhan's economic development zone clearly narrates the situation (jiangtao and zheng, 2020). to minimize the risk of infection, therefore, bigger space in outer area of hospitals (usually in the parking space) has been temporarily allotted for the storage, disinfectant spraying, and their smooth transportation to the treatment facility (cgtn, 2020). according to the ministry of ecology and environment's emergency office, china has planned that every prefecture-level city should have a centralized medical waste treatment facility by the end of 2020 (jing, 2020). it is noteworthy to mention that china has announced a "10-day battle" plan to test all 11 million residents of wuhan for the novel covid-19 (wee and wang, 2020) . such an ambitious drive will obviously generate a large amount of bmw. it is also reported that in lacking adequate waste treatment facilities, the covidwaste of wuhan was also carried to nearby cities facility like the treatment plants in spain is one of such majorly affected countries who has gone through the terrifying experience caused by the infections of sars-cov-2. as on 14 july 2020, spain has to facilitate the rapid and optimal treatment of the huge amount of infectious waste, the agency has implemented to reinforce the ordinary management by the three authorized plants. the incineration of part of the medical waste (the one considered as low risk) has been authorized in some recovery plants which are receiving waste from health centers and it can be seen that the collection of covid-waste is directed along with the msw, however, the instruction is very clear to double-seal the waste-containing bags and to keep it separate by the home-quarantine persons themselves and do not mix with common household waste (acrplus, 2020). the main drawback of this system has been found in the longwaiting time for sending it to the final disposal to incineration. a prolong waiting up to 72 hours can be dangerous due to the long persistence of sars-cov-2 on different surfaces (chin et al., 2020; van doremalen et al., 2020) ; hence, there is every chance of crosscontamination within the gap period of covid-waste generation and sending it to the automated incinerator facility. although no specific guideline was issued for handling covid-waste up to mid of march 2020, as covid-19 spread in india, a proper covid-waste management system was introduced. it was imperative due to the fact that before this pandemic outbreak only 265 tons/day were undergoing to the treatment facilities out of the generated volume of 463 tons/day bmw (dna, 2020). the first big step was to enact the epidemic disease act, 1897; (cpcb, 2020a). the "guidelines for handling, treatment, and disposal of waste generated during treatment/ diagnosis/ quarantine of covid-19 patients" was issued to deal covidwaste disposal at healthcare facilities including the quarantine camps, home-care, sample collection centers, testing labs, state pollution control boards, and bio-waste treatment facilities (cpcb, 2020b (cpcb, , 2020c . despite having the biomedical waste management rule 2016, the guidelines kept specific to ensure covid-waste disposal in a scientific manner (aggarwal, 2020) . the guidelines released by cpcb are summarized in table 2 . the guidelines suggest that the commonly used facemasks and gloves by general people for preventive measures should be enveloped for a minimum of 72 hours before disposal as the msw. it is emphasized that covid-waste generated by the isolation wards must be kept in a double-layered dedicated yellow bags to collect and store separately by marking "covid-19 waste" for a priority handling by the common bio-medical waste treatment facility, cbwtf (the print, 2020). cpcb has also given adequate directions and advisories even to the state pollution control boards (spcb) who are responsible to implement cpcb's guidelines on the floor. spcb is authorized to maintain all the records related to covid-waste generation, treatment, and disposal. this is also valid to tackle the bmw other than covid-waste. spcb can allow the treatment facility to run for extra hours, as and when required. in the revised guidelines of cpcb (issued on april 18, 2020), the operation of cbwtf and its associated staff are included as an essential service part of health infrastructure (the hindu, 2020; scci, 2020). it is clear that the threat of covid-waste is higher than usual bmw. a serious and timely collection, treatment, and disposal of covid-waste by following the full safety measures are the key to handle this infectious waste of high risk. separate collection in double-seal designated bags/bins must be practiced by the isolation wards/ hospitals/ quarantine centers/ home-quarantines. for a timely collection and disposal, the role of urban local bodies is quite important albeit in the lockdown period many waste treatment facilities are facing the manpower crisis. therefore, the workers involved in this job must be taken as a part of an essential service. the proper healthcare and safety measures must be the responsibility of local bodies and the cbwtf operators. it is recommended that no covidwaste should be disposed of by mixing with household solid waste and kept inside the closed container/bins. not only the human-to-human contact but exposures with other potential carriers like mobile phones, keyboards, etc. should also be avoided. moreover, the vehicles involved in covid-waste collections must be disinfected by spraying a 1% sodium hypochlorite solution after every round of waste collection. soon after the removal of ppe and facemasks, the workers should avoid touching their face, nose, mouth, and eyes; only after using a 70% alcohol sanitizer. the awareness among the people can be a panacea for safer handling of covid-waste, hence, the government, local bodies, waste treatment facilities must drive the awareness program using different media to directly reach out to the people. the common use of surgical facemask and hand gloves is being largely consumed and due to their size and lightweight, there is every chance that these waste may be disposed of with solid waste. it is recommended to carefully deal with such waste as they can be highly infectious for a prolonged duration of 7 days. hence, the guidelines to keep paper folding of the waste masks for a minimum of 72 hours much be followed as the "prevention is better than cure". in order to lower down the threat of sars-cov-2 by using covid-waste fomites, their release to environment by the host, and persist on carrier surfaces highlights the j o u r n a l p r e -p r o o f multitude of the applied researcher that requires to address the effective control of pandemic outbreak due to the enveloped novel coronavirus (wigginton and boehm, 2020) . henceforth, an integral approach by environmental engineers, medical doctors, healthcare workers, and scientists can apply their unique skills and experiences with interdisciplinary research to address the need of the hour. for example, the disinfectant spray (h 2 o 2 /naocl) is commonly suggested to inactivate the enveloped virus from the waste surface (gallandat et al., 2017) , but this cannot work in each of the cases. the presence of blood on fomites would require a much higher dosage of disinfectant (wood et al., 2020) that can be better understood for several other circumstances by interdisciplinary researches. due to the global shortcomings in supply chain of personal protectives, reprocessing can significantly mitigate their shortage by other than impromptu recycling techniques. as reprocessing technology will not only help to lower the virus spread and environmental benignness but also increase the availability of personal protectives by their possible re-use. vh 2 o 2 and hot air disinfection process has potential to apply for the reprocessing of covidwaste, however, timely overcome from existing limitations like reduction in oxidant concentration in the presence of specific materials and degree of decontamination in all layers of the trapped viruses are desirable. on that basis, the imperative need for an integrated approach involving environmental engineers, healthcare workers, and researchers are being recommended overcoming the challenges of covid-waste management. the potential spread of sars-cov-2 through fomites of covid-waste is not ruled out. in fact, the novel coronavirus can survive for long periods outside of its host organism like 72 hours on the surface of a surgical mask. hence, covid-waste may cause to the community spread if handled inappropriately. the chemical disinfection using a 1% naocl solution is j o u r n a l p r e -p r o o f one of the best in-situ practices which is also easy to spray and not limited to covid-waste but it is also effective to sanitize the larger space, shopping malls, hospital premises/wards, and isolation centers. microwave disinfection technique is useful to sanitize ppe and cloths that can be recycled and reused; whereas, incineration is useful to tackle a larger volume of covid-waste which is an energy-intensive process but reliable process due to a high operating temperature (800−1200 °c). the strategy like "identify, isolate, disinfect, and safe treatment practices" has been found to be effective for safer management of covid-waste. table 1 : the summative swot analysis of each disinfection technology. table 2 .  use of separate color bins/bags in wards and maintain proper segregation of waste as per the bmwm rules 2016.  use of double-layer yellow color waste in the case of covid-waste  storage of the collected covid-waste in a dedicated collection bin labelled as "covid-19" after the disinfectant spray (1% naocl solution) on inner and outer surface of bags.  in addition, the covid-waste must be labelled as "covid-19 waste" to ensure the priority disposal at the treatment sites.  general waste other than covid-waste should not be mixed and their disposal should be done as common solid waste.  separate record for covid-waste generation from the isolation wards  deputation of separate collection staffs for covid-waste and other solid waste to ensure the timely collection disposal of waste  waste generation, collection, and treatment records tracking by spcbs sample collection centers and testing labs  report opening of the collection centers and testing labs by the state pollution control boards to monitor the covid-waste records  all the guidelines for isolation wards should be applied to the sample collection centers and testing labs quarantine camps and home-care of covid-19 patients  treatment of common collected waste (non-medical) as solid waste  separate collection of bmw if any in the yellow color bags/bins  as and when the bmw is generated, the quarantine camps must inform to the operator of cbwtf for the timely collection of covid-waste  the waste generated by self/home-quarantine suspects/patient should be separately collected in yellow bags and handed over to the authorized collectors engaged by the local bodies common biomedical waste treatment facility  reporting to the respective spcbs about receiving of covid-waste from isolation wards, quarantine centers and homes, and testing centers  regular sanitization of waste collectors  providing the ppe, nitrile gloves, three-layer masks, splash proof aprons, safety boots and goggles  use dedicated vehicle for covid-waste collection with marking and essential sanitization of vehicles with 1% sodium hypochlorite  immediate disposal of covid-waste soon after the receiving  operator of the facility must maintain separate record for collection, treatment, and disposal of covid-waste association of cities and regions for sustainable resource management pollution watchdog releases guidelines to handle covid-19 biomedical waste an environmental and health perspective for covid-19 outbreak: meteorology and air quality influence, sewage epidemiology indicator, hospitals disinfection, drug therapies and recommendations china chooses the sterilwave solution for on-site treatment of waste contaminated by the coronavirus genomic characterization of the 2019 novel human-pathogenic coronavirus isolated from a patient with atypical pneumonia after visiting wuhan safe management of wastes from health-care activities stability of sars-cov-2 in different environmental conditions guidelines for handling, treatment and disposal of waste generated during treatment/diagnosis/ quarantine of covid-19 patients guidelines for handling, treatment and disposal of waste generated during treatment/diagnosis/ quarantine of covid-19 patients: revision 1 guidelines for handling, treatment and disposal of waste generated during treatment/diagnosis/ quarantine of covid-19 patients: revision 2 mounting medical waste from covid-19 emphasizes the need for a sustainable waste management strategy biomedical waste management in india: critical appraisal early transmission dynamics in wuhan, china, of novel coronavirus-infected pneumonia genomic characterisation and epidemiology of 2019 novel coronavirus: implications for virus origins and receptor binding sanitation workers at risk from discarded medical waste related to covid-19 personal protective equipment market by type (hands & arm protection, protective clothing, foot & leg protection, respiratory protection, head protection), end-use industry (manufacturing, construction, oil & gas, healthcare) -global forecast to 2022 reports/personal-protective-equipment-market-132681971.html terminal sterilization of medical devices using vaporized hydrogen peroxide: a review of current methods and emerging opportunities the extraordinary measures for safe waste management against covid-19 (the 3rd version) xpages=10&searchkey=createname&searchvalue=%ea%b9%80%ec%9c%a0%ea %b2%bd&menuid=286&orgcd=&boardid=1338400&boardmasterid=1&boardcateg oryid=&decorator= transmission of sars and mers coronaviruses and influenza virus in healthcare settings: the possible role of dry surface contamination is the fit of n95 facial masks effected by disinfection? a study of heat and uv disinfection methods using the osha protocol fit test environmental assessment for the proposed establishment of sterilwave apparatus for treatment of medical waste at rhino park private hospital challenges and solutions for addressing critical shortage of supply chain for personal and protective equipment (ppe) arising from coronavirus disease (covid19) pandemic -case study from the republic of ireland new guidelines for handling of waste generated during covid-19 patients' treatment covid-19 infection: origin, transmission, and characteristics of human coronaviruses environmentally sustainable management of used personal protective equipment guidelines issued for handling of waste generated during covid-19 patient's treatment double layered bags & colour coded bins: waste management guidelines for covid-19 patients aerosol and surface stability of sars-cov-2 as compared with sars-cov-1 receptor recognition by the novel coronavirus from wuhan: an analysis based on decade-long structural studies of sars coronavirus disinfection technology of hospital wastes and wastewater: suggestions for disinfection strategy during coronavirus disease here's how wuhan plans to test all 11 million of its people for coronavirus safe management of wastes from health-care activities shortage of personal protective equipment endangering health workers worldwide environmental engineers and scientists have important roles to play in stemming outbreaks and pandemics caused by enveloped viruses evaluating the environmental persistence and inactivation of ms2 bacteriophage and the presumed ebola virus surrogate phi6 using low concentration hydrogen peroxide vapor evolution of the novel coronavirus from the ongoing wuhan outbreak and modeling of its spike protein for risk of human transmission shelter hospital mode: how do we prevent covid-19 hospital-acquired infection preliminary estimation of the basic reproduction number of novel coronavirus (2019-ncov) in china, from 2019 to 2020: a data-driven analysis in the early phase of the outbreak coronavirus leaves china with mountains of medical waste writing -original draft, writing -review & editing. h. kim: supervision, funding acquisition this work was supported by brain pool program through the national research foundation of korea (nrf) funded by the ministry of science and ict (grant number: although covid-waste management is in its early stage, the past experiences learned key: cord-304571-1riprk86 authors: ahmed, warish; hamilton, kerry; toze, simon; cook, stephen; page, declan title: a review on microbial contaminants in stormwater runoff and outfalls: potential health risks and mitigation strategies date: 2019-11-20 journal: sci total environ doi: 10.1016/j.scitotenv.2019.07.055 sha: doc_id: 304571 cord_uid: 1riprk86 demands on global water supplies are increasing in response to the need to provide more food, water, and energy for a rapidly growing population. these water stressors are exacerbated by climate change, as well as the growth and urbanisation of industry and commerce. consequently, urban water authorities around the globe are exploring alternative water sources to meet ever-increasing demands. these alternative sources are primarily treated sewage, stormwater, and groundwater. stormwater including roof-harvested rainwater has been considered as an alternative water source for both potable and non-potable uses. one of the most significant issues concerning alternative water reuse is the public health risk associated with chemical and microbial contaminants. several studies to date have quantified fecal indicators and pathogens in stormwater. microbial source tracking (mst) approaches have also been used to determine the sources of fecal contamination in stormwater and receiving waters. this review paper summarizes occurrence and concentrations of fecal indicators, pathogens, and mst marker genes in urban stormwater. a section of the review highlights the removal of fecal indicators and pathogens through water sensitive urban design (wsud) or best management practices (bmps). we also discuss approaches for assessing and mitigating health risks associated with stormwater, including a summary of existing quantitative microbial risk assessment (qmra) models for potable and non-potable reuse of stormwater. finally, the most critical research gaps are identified for formulating risk management strategies. • stormwater has been considered as an alternative water source. • microbial contamination hinders stormwater reuse. • wsud is effective in removing pathogens but requires more validation. • qmra analysis can facilitate decision making and risk management efforts. a b s t r a c t a r t i c l e i n f o water authorities worldwide are exploring alternative water sources to meet ever-increasing demands for potable and non-potable water due to the adverse impacts of climate change on water supplies. stormwater has been considered as an alternative water source for both potable (drinking) and non-potable uses (gardening, landscaping, and irrigation) (mcardle et al., 2011; page et al., 2014c; page et al., 2015) . there are several advantages to using stormwater, including (i) reducing demands on the urban potable water supply (ii) diversification of water supplies (iii) reducing discharge of untreated urban stormwater to urban streams and marine outfalls. despite these advantages, stormwater has not been widely adopted as an alternative water due to a perceived lack of information on the presence and risk from microbial and chemical contaminants. the chemical quality of stormwater has been reviewed and indicated the presence of numerous contaminants including heavy metals, polychlorinated biphenyls, polycyclic aromatic hydrocarbons, halogenated aliphatics, halogenated ethers, monocyclic aromatics, phenols and cresols, phthalate esters, nitrosamines, pesticides, and other organics, especially in urban and/or industrialized areas (makepeace et al., 1995; eriksson et al., 2005; baun et al., 2006; huber et al., 2016) . risk assessments of chemical contaminants in stormwater have suggested that in some cases, contaminants may exceed concentrations in the environment that are relevant for ecological endpoints, but may be lesser contributors to human health risks (eriksson et al., 2005; baun et al., 2006; eriksson et al., 2007) . non-carcinogenic risks due to ingestion of fish in stormwater-contaminated waterbodies have been identified as a potential concern (bickford et al., 1999) . iron levels exceeding australian guidelines and elevated (but below guideline) levels of arsenic have also been identified as potential risks for managed aquifer recharge with stormwater, with overall chemical risks from various compounds posited to be low (page et al., 2010a (page et al., , 2010b . heavy metals and pathogens are thought to be the drivers of human health risks for exposure to stormwater (page et al., 2010a (page et al., , 2010b (page et al., , 2010c (page et al., , 2010d chong et al., 2013; ma et al., 2016) . indeed, public perception of microbial risks, in particular, remains a crucial barrier to the expansion of water recycling and reuse (higgins et al., 2002) . therefore, the current review will focus on microbiological contaminants in stormwater and their associated risks. pathogenic bacteria, viruses and protozoa can be found in stormwater runoff and subsequently transported to environmental water bodies through sewer overflows, defective septic systems, agricultural runoff, defecation from wild animals and discharge of treated sewage (ahmed et al., 2005; noble et al., 2006; rajal et al., 2007) . the pathogens present in various animal fecal sources will differ from those in sewage soller et al., 2015; federigi et al., 2019) , and therefore stormwater is likely to contain a different pathogen profile than sewage. studies have reported a high prevalence of fecal indicator bacteria (fib) and enteric pathogens in stormwater (noble et al., 2006; rajal et al., 2007; awqc, 2008; sidhu et al., 2012a; cizek et al., 2008) . the microbial quality of water is assessed by fib such as escherichia coli (e. coli) and enterococcus spp. (usepa, 2000) . these indicators are abundant in the intestine of warm-blooded animals, and their presence in waters indicates fecal contamination and the likely presence of potential pathogens. one major limitation of fib is their poor correlation with the presence of pathogens, especially protozoans and enteric viruses (hörman et al., 2004; selvakumar and borst, 2006; mcquaig et al., 2009) . another limitation of fib is that they cannot provide information regarding the sources of fecal contamination (field and samadpour, 2007; stoeckel and harwood, 2007) . remediation strategies can be more effectively implemented if the potential sources of fecal contamination and pathogens are known in stormwater (sidhu et al., 2012b) . since the monitoring of fib in water does not provide information on origin, e.g., human or animal feces, researchers have developed a set of analytical tools collectively known as "microbial source tracking (mst) tools." these tools can be used to obtain information on whether the fecal contamination in water came from human or animal wastewater or both (harwood et al., 2014) . epidemiological studies indicated that the risks of gastrointestinal illness (gi) among swimmers can be high when the water is contaminated with untreated sewage, as presumably indicated by the presence of elevated levels of fib (cabelli et al., 1982; wade et al., 2006; marion et al., 2010) . however, mixed sources of fecal contamination (human and animal feces) are often expected to be found in stormwater. epidemiological data are lacking regarding the human health impacts from mixed source of fecal contamination, which may pose different human health risks. several studies in the research literature have provided quantitative data on potential pathogens in roof-harvested rainwater stored in tanks (ahmed et al., 2008a; ahmed et al., 2014a; dobrowsky et al., 2014) . however, pathogen abundance data in stormwater runoff and outfalls are still scarce. therefore, the objective of this review is to summarize the concentrations of traditional and alternative fecal indicators, mst marker genes and potential pathogens in stormwater runoff and outfalls. a section of this review has been dedicated to summarizing available quantitative microbial risk assessments (qmras) for potable and non-potable uses of stormwater. the focus for reviewing available qmra models is to summarize the types of assumptions used to model pathogen fate, transport, and exposure in order to identify data gaps and areas where further attention is warranted. additionally, a review of fecal indicators and pathogen log removal values (lrvs) through water sensitive urban design (wsud) or best management practices (bmps) of stormwater runoff has been compiled. finally, risk mitigation approaches and the most critical research gaps are identified concerning the public health aspects of stormwater reuse. peer-reviewed journal articles, reports, conference proceedings, and guidelines published from 2005 to 2018 were taken into consideration. electronic databases including pubmed, google scholar, and web of knowledge were used to obtain the information. the literature search was performed using the keywords "(stormwater or sensitive urban design or wsud or green infrastructure or low impact development or low impact urban design and development) and (pathogen or microb-or bacter-or protozoa or source tracking or mst or fecal indicator or fecal contamination or health risk or qmra) and included studies that are reported in english. routine monitoring of stormwater quality focuses on quantification of e. coli and enterococcus spp. high concentrations (n4 log 10 cfu/ 100 ml) of fib are generally found in stormwater runoff and receiving waters . most of the stormwater or outfall samples often exceed the sample threshold value of fib for the designated recreational use of waters by one or more orders of magnitude. for example, if we consider the 95th percentile value for enterococcus spp./100 ml water, many stormwater samples will exceed the threshold value classified as class d (i.e., n 501 cfu/100 ml) by the national health & medical research council (nhmrc) guidelines for recreational use of water (nhmrc, 2008) . the nhmrc used information from who (2003) and kay et al. (2004) to estimate that in class d there would be greater than a 10% chance of illness per single exposure. storm events have the potential to resuspend sediment-bound fib and pathogens back into water column resulting in elevated contamination levels cizek et al., 2008; krometis et al., 2010; sidhu et al., 2012a) . the elevated fib concentrations generally occur at or just before the peak inflow of the storm hydrograph. stumpf et al. (2010) determined the loading of fib over dry and wet weather conditions in tidal creeks in north carolina, usa. the authors reported 30 and 37 times greater loadings of e. coli and enterococcus spp. in storm flow compared to base flow. e. coli and enterococcus spp. were weakly correlated (r 2 = 0.13 to 0.32) with total suspended solids, while strong associations (r 2 = 0.40 to 0.78) were observed between fib and streamflow rate and various stages (base, rising, peak and falling) of the hydrograph. the authors also noted a large intra-storm variability in fib concentrations and recommended intensive sampling throughout a storm in order to accurately quantify fib rather than collecting a single grab sample. rural or high density residential areas are reported to contribute 30-50 times greater e. coli levels in stormwater compared to light or sparsely populated residential area (mccarthy et al., 2006) . paule-mercado et al. (2016) investigated the variability of fib concentrations in agricultural, mixed land use and urban catchments with variable catchment area, land use, and land cover. the urban site had the greatest level (e. coli 7.39 log 10 mpn/100 ml; fecal streptococci 7.21 log 10 cfu/ 100 ml) of fib concentrations compared to agricultural site (e. coli 2.51 log 10 mpn/100 ml; fecal streptococci 2.48 log 10 cfu/100 ml) because of runoff from commercial markets and impervious cover, sewer and septic overflows. the authors noted intra-event variability of fib across the monitoring sites. fib concentrations increased during the peak flow and then decreased as the storm progressed. levels of fib significantly (p b 0.05) varied between early and late summer seasons with higher fib concentrations observed in early summer. anthropogenic activities and impervious cover were found to influence positive correlations (r n 0.6) between fib numbers and environmental parameters such as temperature, turbidity, and total suspended solids. although, fib monitoring in stormwater is a common practice, there are uncertainties associated with stormwater flow and e. coli (mccarthy et al., 2008; harmel et al., 2006) . uncertainties of discrete e. coli samples and flow measurements were n30 and 97%, respectively. e. coli event mean concentration uncertainties varied between 10 and 52% and that uncertainties relating to site mean concentrations ranged from 35 to 55% (mccarthy et al., 2008) . sample collection procedures (5-30%), laboratory analysis, preservation/storage, and flow also contributed substantial (14-28%) uncertainties (harmel et al., 2006; harmel et al., 2010 harmel et al., , 2016 . another limitation of fib is that they do not often correlate well with the presence of pathogens in environmental waters. the appropriateness of using fib to indicate the presence of pathogens especially viruses and protozoa in stormwater has been questioned (jiang et al., 2001; schroeder et al., 2002; jiang, 2004; robertson and nicholson, 2005; signor et al., 2005; awqc, 2008) . this is somewhat expected as fib in stormwater are sourced from feces of both human and animals, while human pathogens especially enteric viruses in urban stormwater mainly derived from sewage. in addition, the decay rates of fib may be significantly different than those of viruses (ahmed et al., 2014b) . hence, monitoring of fib and interpreting their concentrations in terms of human health risks may not yield any meaningful outcomes. as a result of these limitations, fib are generally not used directly for risk estimation. however, some e. coli strains such as enteropathogenic e. coli (epec), enterohemorrhagic e. coli (e. coli o157:h7 or other ehec), enterotoxigenic e. coli (etec), and others are pathogenic to humans and can be used for risk estimation purposes. although these subsets are not routinely measured, general fib can be used as a preliminary screening tool prior to testing for other pathogens. additionally, ratios of fib to pathogens are used occasionally for risk assessment purposes (petterson et al., 2016) . fecal contamination in stormwater can originate from point and non-point sources. human health risk will be different depending on the sources. untreated sewage poses the greatest risks to humans and the environment due to high concentrations of enteric viruses (ec, 2000; fong et al., 2010; soller et al., 2010) . sewage may be introduced into stormwater through illicit connections, cross connection between sewer pipes, storm drains and leakages into sewers through broken lines or poor pipe joints (pitt, 2004) . the presence of sewage in stormwater can be problematic due to the likely co-presence of pathogens. identifying the presence of sewage in stormwater using is not straightforward due to dilution, infiltration, and lack of sensitive detection methods (panasiuk et al., 2015) . however, microbial source tracking (mst) marker genes are used to identify human feces and other sources of animal fecal contamination such as cattle, dogs, pigs, and birds in water (harwood et al., 2014; ahmed et al., 2016) . human feces-associated marker genes such as bacteroides hf183 (hf183), crassphage cpq_056 and cpq_064, pepper mild mottle viruses (pmmov), human polyomaviruses (hpyv), and lachno3 are currently being used to determine the presence of human fecal contamination in environmental waters by research laboratories and water quality managers. these marker genes are sensitive and accurate analytical approaches of human fecal contamination due to high hostspecificity and abundance in human and animal feces (boehm et al., 2013) . several studies have reported the presence of human fecesassociated marker genes in stormwater runoff and outfall samples (table 1) . sidhu et al. (2012a) reported the presence of the bacteroides hf183 (16 of 21 samples were positive for hf183 during both dry and wet weather samples) and enterococcus faecium enterococci surface protein (esp) marker gene (8 of 23 samples were positive for esp during both dry and wet weather samples) in stormwater run-off samples and suggested the ubiquitous presence of sewage in the urban environment. mst field studies have identified aging infrastructure as a contributor to sewage intrusion into stormwater system (marsalek and rochfort, 2004; sauer et al., 2011; guérineau et al., 2014) . several studies have reported the greater concentrations of the hf183 marker gene in stormwater samples (sercu et al., 2011; van de werfhorst et al., 2014; paar 3rd et al., 2015) (table 1) . olds et al. (2018) observed high levels of human bacteroides (hb) and lachno2 in the milwaukee estuary and at the lower reaches of the three major rivers forming the estuary in milwaukee, wi, usa after storm events. concentrations of these marker genes were one to three orders of magnitude higher (4.04-5.59 log 10 gc/l of hb and 4.04-6.27 log 10 gc/100 ml of lachno2) in stormwater samples during storm events compared to low flow periods (3.53 log 10 gc/100 ml of hb and 3.71 log 10 gc/100 ml of lachno2). a further increase in the order of a magnitude of marker genes was observed during the combined sewer overflow (cso) event compared to storm events. the marker gene contamination level was high enough to exceed acceptable gi risk benchmark of 32 to 36 per 1000 primary contact recreators in rivers or swimming at nearby beaches (usepa, 2012a). staley et al. (2016) quantified bacteroides hf183 in storm water outfalls and several sites along the humber river in toronto, canada. hf183 was detected at all sites, with greater concentrations in outfall samples (mean outfall concentrations of 6.22 log 10 gc/l). their results indicated ubiquitous sewage contamination at storm water outfalls and throughout the humber river. steele et al. (2018) used digital pcr to quantify the hf183 marker gene in samples collected from multiple storm events from san diego river (n = 23) and tourmaline creek (n = 21) that discharge to popular surf beaches in san diego, ca, usa. the authors noted 6.45-6.95 log 10 gc hf183/l in stormwater discharges from tourmaline creek and 5.30-6.24 log 10 gc/100 ml in stormwater discharges from the san diego river. the hf183 marker was consistently detected with human pathogen nov (96% positive agreement in san diego river and 72% positive agreement in tourmaline creek). ahmed et al., 2018c examined the extent of sewage contamination in an urban recreational lake located in sydney, australia that receives wet weather overflows using two human feces-associated crassphage marker genes (cpq_056 and cpq_064). the concentrations of both markers were higher (cpq_056 ranging from 3.40 to 7.62 log 10 gc/l table 1 prevalence and concentrations (log 10 gc/l) of sewage and animal-associated marker genes in stormwater runoff and outfall samples. -: quantitative data were not provided; nm: not mentioned; *: where available; a = mean (overall mean concentrations were calculated by authors from the available data); b = median. and cpq_064 ranging from 2.90 to 6.95 log 10 gc/l) in 20 of 20 (for cpq_056) and 18 of 20 (for cpq_064) samples collected after storm events compared to a dry weather event (10 of 10 samples were qpcr negative for the cpq_056 and 8 of 10 were negative for the cpq_064 marker genes) suggesting that sewage contamination was transported by urban stormwater runoff to the studied lake. in addition to human-feces associated bacterial markers, viruses such as hadv species a-f and hpyv (urine indicator) have been used to detect human fecal contamination in stormwater runoff (brownell et al., 2007; ahmed et al., 2012; sidhu et al., 2013) . however, none of these studies provided the concentrations of these viruses in stormwater samples. quantifying viral markers in stormwater samples can be difficult due to factors such as their low numbers in sewage, dilution and loss due to recovery and dna extraction (horswell et al., 2010; wong et al., 2012) . compared to human feces-associated markers, less information is available on the prevalence and concentrations of animal fecesassociated marker genes. staley et al. (2016) determined the concentrations of seagull-associated gull4 marker gene in a river and stormwater outfall samples in ontario, canada. river sites were frequently (5 of 7 sites where gull fecal contamination was detected) impacted by gull fecal contamination. two of five storm outfalls were also positive for gull feces. bambic et al. (2015) reported the moderate occurrence of cattle and dog markers in stormwater samples ranging from 4.67 and 4.75 log 10 gc/l. storm events led to an increase (4.67 and 4.75 log 10 gc/l) in cattle and dog feces-associated bacteroides marker genes compared to dry events (3.23 and 3.20 log 10 gc/l). corsi et al. (2014) tested 63 samples over a 17-month period across the three sampling locations in milwaukee river, wi, usa for human and bovine viruses. twenty samples were collected during low-flow periods and 43 were collected during rainfall or snowmelt runoff periods. three of the seven bovine viruses analyzed were detected during the study period. bovine polyomavirus was present most often (32%) followed by bovine rotavirus group a (19%), and bovine viral diarrhea virus type 1 (5%). bovine viruses were present in 46% of runoff samples resulting from precipitation and snowmelt and 14% of low-flow samples. maximum concentrations for these three viruses ranged from 6.7 to 11 gc/l. bovine viral diarrhea virus type 2, coronavirus, enterovirus, and adenovirus were not detected. the results suggested the presence of bovine fecal contamination in stormwater runoff. this is particularly important because a recent study reported the high risks of gastrointestinal illness from cattle feces contaminated water due to protozoan pathogens cryptosporidium and giardia spp. (soller et al., 2010) . fecal contamination in stormwater originate from point and nonpoint sources, and this is supported by the fact that a number of stormwater outfall samples had high fib with low or no human bacteroides, suggesting that fib may have originated from non-human sources (sauer et al., 2011) . therefore, markers targeting different animal species of zoonotic pathogen potential need to be employed to obtain more information on the magnitude of animal fecal contamination in addition to sewage contamination. most of the stormwater studies provided mst results in the presence/absence form. the presence/absence results of any given marker in a sample should be interpreted with care. mere presence of a marker does not represent any risk as the marker concentrations are generally greater in sewage or animal feces compared to pathogens. in contrast, lack of detection of a marker does not necessarily indicate the sample is free from other contaminants and safe for human exposure. multiple lines of evidence (i.e., a toolbox approach) are required before implementing remediation or assessing human health risk (ahmed et al., 2012; mauffret et al., 2012) . increased urbanisation will increase the dissemination of waterborne pathogens in the environments (hofstra, 2011) . information on the concentrations of pathogens in stormwater is needed for risk assessment and management for beneficial reuse. however, the data on the occurrence and levels of pathogens in stormwater runoff is limited. this is because collecting stormwater samples during storm events can be challenging. grab samples are easy to collect, and the cost associated with sampling is low, but only represent a snapshot of the water quality at the time of collection (harmel et al., 2010) . automated samples are more accurate and appropriate for stormwater sampling as they collect representative samples. however, it has to be installed at a specific location, requiring construction of infrastructure and regular maintenance. other factors such as the presence of high concentrations of suspended solids, grease and pcr inhibitors make it difficult to detect pathogens with molecular based methods (usepa, 1999; stenstrom et al., 1984; rajal et al., 2007) . table 2 shows the occurrence and concentrations (where available) of bacterial, protozoa, and viral pathogens in stormwater. sidhu et al. (2012a) investigated the presence of human pathogens in the urban stormwater runoff in australia. hadv was frequently detected from all sampling sites during wet weather conditions suggesting their widespread presence. campylobacter jejuni, campylobacter coli, and salmonella enterica were also detected during wet weather conditions. based on the results, the authors suggested that some degree of treatment of captured stormwater would be required if it were to be used for non-potable purposes. however, the authors did not mention lrvs that would be required for the safe use of stormwater. corsi et al. (2014) studied the prevalence, as well as hydrological and seasonal variations of enteric viruses in an urban watershed, a rural sub watershed and the milwaukee river mouth, wi, usa. the authors processed large volumes of water samples (56-2800 l) over a 17 months duration to account for variability throughout changing hydrologic and extended (24-h) low-flow periods. human and bovine viruses were detected in 49 and 41% of samples (n = 63), respectively. all human viruses analyzed were detected at least once including hadv (40% of samples), norovirus (nov) gi (10%), enterovirus (ev) (8%), rotavirus (rov) (6%), nov gii (1.6%) and hepatitis a virus (hav) (1.6%). human viruses were present in 63% of runoff samples resulting from precipitation and snowmelt, and 20% of low-flow samples. maximum human virus concentrations were n2.47 log 10 gc/l. steele et al. (2018) used digital qpcr to quantify a number of bacterial and viral pathogens in stormwater samples from multiple storm events from two different watersheds that discharge to popular surf beaches in san diego, ca, usa. this is the most comprehensive study reviewed that determined the concentrations of several human health significant pathogens in stormwater discharges in the usa. among the enteric viruses tested, nov were highly prevalent in both the san diego river and tourmaline creek with concentration ranging from 1.39 to 2.69 log 10 gc/100 ml of water. the prevalence of hadv were much lower than nov; 9% of the samples in tourmaline creek and 22% of the samples in san diego river were positive for hadv with concentration ranging from 1.14 to 1.61 log 10 hadv gc/100 ml of water. enterovirus was not detected in any of the water samples tested. among the two bacterial pathogens (campylobacter spp., and salmonella spp.), campylobacter spp. was the most commonly detected pathogens (100 and 45% samples were positive at san diego river and tourmaline creek, respectively compared to 25 and 10% samples were positive for salmonella spp. at san diego river and tourmaline creek, respectively. c. coli (87%) and c. lari (78%) were the most frequently detected species in stormwater discharges from san diego river, while c. lari (48%) and c. jejuni (29%) were the most commonly detected in tourmaline creek. the authors stated that such data is an important step forward for assessing risk associated with stormwater. data generated using qpcr need to be interpreted carefully because qpcr assays quantify both viable and dead pathogens and do not provide information on the infectivity status of the pathogen tested. also, complex water matrix such as stormwater generally contain various organic substances, salts, acid and detergents which may inhibit pcr digital qpcr may also offer an advantage over qpcr when dealing with samples with inhibitory substances (dingle et al., 2013; cao et al., 2016) . this is because in digital qpcr sample is partitioned into many wells are droplets unlike qpcr which measures the target as it occurs with comparison with a standard curve. cizek et al. (2008) characterized the partitioning behaviour of cryptosporidium and giardia with traditional and alternative fecal indicators (e. coli, enterococcus spp., and clostridium perfringens) and a viral surrogate (coliphage) in stormwater runoff. both protozoa exhibited similar levels of particle association during dry weather (roughly 30%) with an increased level observed during wet weather events (giardia 60% and cryptosporidium 40%). during wet weather events, fib, coliphage and protozoa concentrations increased (~1-2 orders of magnitude) in tributaries examined in the kensico reservoir. fib did not exhibit a strong one-to-one relationship with cryptosporiduum or giardia in terms of total concentration or the settleable fraction in the kensico reservoir. the authors also found c. perfringens spores (spearman r = 0.13 and coliphage r = 0.11) were the best indicators for cryptosporidium. this is because the inactivation rates of c. perfringens and c. parvum were reported to be in the same order of magnitude (hijnen et al., 2000) . in general, concentrations of pathogens in stormwater are poorly reported and some data may not be useful to infer risk or for quantitative microbial risk assessment (qmra). for example, several studies have failed to detect or provided the percentage of samples positive for pathogens without giving quantitative numbers (surbeck et al., 2006; rajal et al., 2007; sidhu et al., 2012a; bambic et al., 2015) . most of the stormwater studies determined the concentrations of genus cryptosporidium and giardia. however, in urban stormwater there is evidence that most samples do not contain human infectious genotypes that are capable of causing illnesses in humans rather contain genotypes that infect animals. for instance, data from jiang (2004) studying three united states sewered urban stormwater catchments found that only about 5% of around 100 cryptosporidium oocyst types characterized were potentially human-infective. recent studies reported high risks due to campylobacter spp. through reuse of stormwater in the netherlands (sales-ortells and medema, 2015) and australia (murphy et al., 2017) . these studies, however, only measured members of the genus campylobacter to estimate risk. genus campylobacter is comprised of 25 species, two provisional species and eight sub-species, with only a few species of human health significance (man, 2011) . further research should focus on determining the levels of c. jejuni, c. coli or other pathogenic species such as c. lari and c. upsaliensis in stormwater for more accurate risk assessment. finally, the persistence of pathogens in stormwater compared to wastewater or other matrices has not been well characterized but can provide useful information for qmra. a systematic review by boehm et al. (2018) of pathogen persistence in surface waters indicated few decay constants available for protozoan and viral pathogens or viral surrogates, with viruses having the greatest degree of persistence. a comparison of the hf183 mst marker with nov indicated that the first order decay coefficient k was higher for hf183 than nov. to the author's knowledge, a similar meta-analysis has not been performed for pathogens in stormwater. sidhu et al. (2015) estimated a t 90 value of b3 days for bacterial pathogens, and b120 days and n200 days for cryptosporidium spp. oocysts and enteric viruses, respectively in recycled stormwater used for managed aquifer recharge. due to the persistence of viral pathogens, these microorganisms are likely to drive concerns for human health risk. various approaches for assessing the health risks of microbial contaminants have been applied in the stormwater context including epidemiological approaches and quantitative microbial risk assessment (qmra) models. epidemiological studies observe patterns of disease in conjunction with environmental exposure and provide inferences rooted in observed health outcomes, and for this reason are highly valuable for assessing health risks. the findings of several epidemiological studies have supported a relationship between stormwater exposure and waterborne illness for stormwater-impacted waterbodies (haile et al., 1999; colford jr et al., 2007; soller et al., 2017) . however, due to the study sizes and expense required to achieve predictive power in epidemiological studies and difficulty attributing risks to a particular exposure source and/or pathway, often qmra approaches are used to assess risks where effect sizes are projected to be small due to low environmental concentrations. qmra uses a process of hazard identification, exposure assessment, dose response analysis, and risk characterization to predict the risk of an infection or disease-related outcome based on an exposure to environmental media (haas et al., 2014) . to the author's knowledge, there has not been an epidemiological study for potable or non-potable uses of stormwater resources. however, studies by ashbolt and bruno (2003) and soller et al. (2017) have demonstrated the utility of combining both epidemiological and qmra information where feasible for stormwater-affected waterbodies. undertaking qmra for various exposures to stormwater can nevertheless be challenging due to difficulties in discerning the sources and concentrations of pathogen contamination in stormwater, and assumptions regarding pathogen sources, fate, and transport are needed depending on the availability of site-specific information. several (n = 16) qmra studies have relied upon concentrations of pathogens observed in stormwater-impacted coastal, recreational waters, or drinking source waters for assessment of health risks (donovan et al., 2008; soller et al., 2010; ten veldhuis et al., 2010; fewtrell et al., 2011; tseng and jiang, 2012; andersen et al., 2013; mcbride et al., 2013; de man et al., 2014; sales-ortells and medema, 2014; schoen et al., 2014; soller et al., 2014; adell et al., 2016; krkosek et al., 2016; lim et al., 2017; soller et al., 2015; soller et al., 2017) , and two have used other modelling approaches for microbial health risks such as bayesian network modelling (goulding et al., 2012) or disease transmission models (soller et al., 2006) . these recreational water qmras are reviewed in detail by federigi et al. (2019) . however, few studies have conducted a qmra for potable and non-potable reuse exposures to stormwater ( table 3 ). the focus on potable and non-potable uses here is due to the difficulty of comparing recreational exposures with multiple nonpoint as well as point sources of contamination with stormwater-only exposures. stormwater-impacted recreational waterbody exposures using fib as well as pathogens as index pathogens were very high in some cases, up to 1.0 for a homeless population ingesting giardia, for example (donovan et al., 2008) . the risks from potable and non-potable uses of stormwater in table 3 varied substantially depending on the target pathogen and exposure scenario. risks were considered highest for viral pathogens, in most cases exceeding risk benchmarks for potable and non-potable use with the exception of toilet flushing in some cases murphy et al., 2017) . the studies summarized in table 3 indicate that potable and non-potable exposures to stormwater are likely to exceed water quality targets [e.g. up to a geometric 240 cfu/ ml for recycled water (usepa, 2012b)] and risk benchmarks (10 −4 probability of infection or 10 −6 disability adjusted life years per person per year (pppy) in the absence of additional treatment and/or bmps depending on the area, end use, and source water. microbial risks from harvested rainwater are considered as captured stormwater but have been reviewed elsewhere (hamilton et al., 2019) . factors such as temporal, regional, and compositional complexity of stormwater can make the quantification of pathogens more difficult than for some other matrices. once concentration values are obtained, values can be corrected for recovery efficiency in a qmra, however, low or variable recovery efficiencies can also complicate qmra analysis. furthermore, concentrations observed at the point of exposure may not be indicative of realistic exposure scenarios over time as they typically are not observed after a rainfall event during presumably peak pathogen concentrations, or dilution occurs at the point of exposure that in some cases will render concentrations of pathogens below the analytical detection limit (mcbride et al., 2013) . these factors must be taken into account when constructing qmra models. previous studies of pathogens in stormwater discharges have relied upon small samples sizes (sidhu campylobacter spray ingestion 4.6 × 10 -7 /b1.0 × 10 -10 (95 th b1.0 × 10 -10 ) daly; routine ingestion 1.5 × 10 -6 /b1.0 × 10 -10 (95 th b1.0 × 10 -10 ) daly; accidental ingestion 1.2 × 10 -7 /b1.0 × 10 -10 (95 th b1.0 × 10 -10 ) daly cryptosporidium spray ingestion 6.2 × 10 -8 /1.6 × 10 -8 (95 th 2.5 × 10 -7 ) daly; routine ingestion 6.2 × 10 -7 /1.6 × 10 -7 (95 th 2.5 × 10 -6 ) daly; accidental ingestion 6.8 × 10 -7 /1.8 × 10 -7 (95 th 2.8 × 10 -6 ) rotavirus spray ingestion 4.3 × 10 -6 /4.9 × 10 -7 (95 th 7.0 × 10 -4 ); routine ingestion 2.8 × 10 -5 /4.0 × 10 -6 (95 th 1.4 × 10 -4 ); accidental ingestion 4.2 × 10 -5 /3.9 × 10 -6 (95 th 1.6 × 10 -4 ) ingestion not specified c. parvum: b1 × 10 -10 -1.5 × 10 -3 / b1 × 10 -10 -1.5 × 10 -3 daly (95 th b1 × 10 -10 -1.5 × 10 -3 ). campylobacter: : b1 × 10 -10 daly all parameters. rotavirus b1.0 × 10 -10 -8.4 × 10 -4 /b1.0 × 10 -10 -8.4 × 10 -4 (95 th b1.0 × 10 -10 -8.4 × 10 -4 ). campylobacter cryptosporidium rotavirus adenovirus: toilet flushing annual infection risk 1.1 × 10 -7 -8.9 × 10 -7 (95 th 2.7 × 10 -7 -1.2 × 10 -6 ); daly risk 3.0 ×10 -9 -2.4 × 10 -8 (95 th 7.2 × 10 -8 -3.1 × 10 -8 ). showering annual infection risk 3.6 × 10 -7 -5.3 × 10 -5 (95 th 1.3 × 10 -6 -3.5 × 10 -4 ); daly risk 1.1 × 10 -8 -1.6 × 10 -6 (95 th 3.5 × 10 -8 -9.3 × 10 -6 ). norovirus: toilet flushing annual infection risk 5.3 × 10 -7 -1.3 × 10 -4 (95 th 1.6 × 10 -6 -1.34 × 10 -4 ); daly risk 1.0 × 10 -20 -1.5 × 10 -16 (95 th 5.3 × 10 -19 -3.2 × 10 -15 ). showering annual infection risk 3.4 × 10 -4 -4.3 × 10 -2 (95 th 1.6 × 10 -3 -1.9 × 10 -1 ); daly risk 1.1 × 10 -14 -6.3 × 10 -11 (95 th 1.4 × 10 -10 -1.0 × 10 -7 ). food crop annual infection risk 8.0 × 10 -4 -9.8 × 10 -1 (95 th 2.6 × 10 -2 ); daly risk 8.0 × 10 -14 -1.1 × 10 -6 (95 th 3.3 × 10 -10 -1.8 × 10 -5 ) campylobacter aerosols 2.7 × 10 -9 -0.1 (95 th 1.5 × 10 -7 -7.0 × 10 -2 ); hand-to-mouth 2.7 × 10 -8 -0.15 (95 th 1.5 × 10 -6 -0.12); accidental ingestion 2.7 × 10 -6 -0.24 (95 th 1.5 × 10 -4 -0.21) salmonella spp. aerosols 1.3 × 10 -12 -5.0 × 10 -5 (95 th 4.1 × 10 -10 -7.0 × 10 -2 ); hand-to-mouth 1.3 × 10 -11 -0.15 (95 th 4.1 × 10 -9 -0.12) petterson et al., 2016 (continued on next page) garden irrigation aerosol ingestion: per infection 1.1 × 10 -9 -3.1 × 10 -3 , annual risk 1.0 × 10 -7 -1.4 × 10 -1 (95 th 1.4 × 10 -7 -7.0 × 10 -1 ), daly risk 1.3 × 10 -10 -2.2× 10 -1 (95 th 2.2 × 10 -10 -1.1 × 10 -3 ) garden irrigation routine ingestion hand-to-mouth: per infection 1.1 × 10 -6 -2.4 × 10 -1 , annual risk 1.0 × 10 -6 -2.4 × 10 -1 (95 th 1.6 × 10 -6 -4.9 × 10 -1 ), daly risk 1.4 × 10 -9 -3.9 × 10 -4 (95 th 2.5 × 10 -9 -9.5× 10 -4 ) garden irrigation accidental ingestion: per infection 1.1 × 10 -10 -3.7 × 10 -4 , annual risk 1.2 × 10 -7 -1.7× 10 -1 (95 th 1.7 × 10 -7 -7.8 × 10 -1 ), daly risk 1.6 × 10 -10 -2.7 × 10 -4 (95 th 2.7 × 10 -10 -1.2 × 10 -3 ) municipal irrigation: per infection 1.1 × 10 -8 -2.6 × 10 -3 , annual risk 1.0 × 10 -6 -1.4 × 10 -1 (95 th 1.4 × 10 -6 -6.1 × 10 -1 ), daly risk 1.3 × 10 -9 -2.3 × 10 -4 (95 th 2.2 × 10 -9 -2.3 × 10 -4 ) toilet flushing: per infection 1.1 × 10 -8 -2.4 × 10 -1 , annual risk 5.6 × 10 -7 -2.4 × 10 -1 (95 th 7.9 × 10 -7 -4.7 × 10 -1 ), daly risk 7.2 × 10 -10 -3.9 × 10 -4 (95 th 1.2 × 10 -9 -9.3 × 10 -4 ) indoor use (toilet flushing and clothes washing), accidental ingestion of treated non-potable water (cross-connection with potable water), unrestricted outdoor irrigation, drinking toilet flushing (3×10 -5 l/day, 365 d/y), clothes washing (1×10 -5 l/day, 365 d/y), irrigation and dust suppression (1×10 -3 l/day, 50 d/y), cross-connection of treated water with potable water (2 l/day, 1 day/year, 10% of population exposed), potable consumption (2 l/day, 365 days). multiple dose response models used. log removals to achieve target concentrations associated with a 10 -4 annual infection risk calculated: norovirus: toilet flushing 2.5-7.3, unrestricted irrigation 3.2-8.0, indoor use 5.0-7.9, drinking 9.3-12.4. mastadenovirus: toilet flushing 2.1-4.1, unrestricted irrigation 2.8-4.8, indoor use 3.9-5.9, drinking 6.9-8.9 cryptosporidium spp.: toilet flushing 0.8-3.8, unrestricted schoen et al., 2017 schoen et al., et al., 2012a schoen et al., , 2012b mcbride et al., 2013; sales-ortells and medema, 2015) , limiting the ability to capture the large variability in stormwater pathogen concentrations due to potentially diverse fecal contamination sources (human and multiple animal fecal wastes, affecting the types of index pathogens chosen for the qmra), rainfall patterns, decay rates, and other factors. monitoring efforts conducted to inform qmras by petterson et al. (2016) and mcbride et al. (2013) confirmed that variability in pathogen concentration is indeed high between rainfall and baseline events. there is therefore a need to look at a scenario-conditional risk estimate (sometimes referred to as "conditional risk"), rather than averaging or annualizing over time without regard to rainfall events. pathogens can survive on urban surfaces and building materials, for example, and could furthermore be introduced into stormwater during subsequent rain events without the presence of an ongoing fecal source. this further supports the need for comparison of stormwater wet-weather risks with dry event (baseline) risks (taylor et al., 2013) . some of the principal challenge in conducting a qmra for stormwater is determining the concentration of pathogens in stormwater discharges or harvesting systems, and addressing the complexities of their transport and inactivation prior to arrival at a human receptor. in lieu of a detailed hydrodynamic or fate and transport models for pathogens, simplified assumptions of decay and dilution between a pathogen source and human receptor are often made. dilution factors are sometimes applied to estimate pathogen loads between stormwater and receiving recreational bodies; for example, mcbride et al. (2013) used a 30-fold dilution factor applied to the concentrations of pathogens observed in stormwater discharges. other studies have applied an estimated microbial decay factor for particular pathogens or indicators as surrogates for pathogens in stormwater, sometimes also coupled with a dilution factor (petterson et al., 2016; lim et al., 2015) . the use of hydrodynamic mixing and inactivation models such as those applied by andersen et al. (2013) could be used to obtain more accurate site-specific dilution information, or a distribution of dilution factors could be incorporated into a monte carlo approach in qmra models as performed in soller et al., 2017. improved characterization of different removal values for bacteria, protozoans and viruses in stormwater treatment processes can also improve qmra estimates, as previous estimates have been based on fib rather than pathogens themselves due to limited data (davies et al., 2008; page et al., 2010a page et al., , 2010b page et al., , 2010c page et al., , 2010d petterson et al., 2016) . limited information is available for pathogen removal by stormwater treatment barriers and would be informative for conducting risk analyses. additionally, these values can be compared with theoretical lrvs necessary to meet health risk targets (nrmmc-ephc-ahmc, 2009; page et al., 2015; schoen and garland, 2015; schoen et al., 2017) . as stormwater concentrations of pathogens cannot always be directly measured, impacts to stormwater can also be estimated; petterson et al. (2016) modelled avian contamination of stored stormwater resources with birds colonized by campylobacter and salmonella as well as pathogen inputs from human sewage using an epidemiologic approach, making use of information about disease incidence, pathogen excretion and known sewage flow rates to approximate loading rates in a typical sewage. several recent studies used qmra analysis to determine hf183 concentrations that represent human health risks to swimmers based on the recreational water quality criteria (rwqc) risk benchmark of 36/1000 primary contact recreators (usepa, 2012a; boehm et al., 2015; ahmed et al., 2018d) . such approaches can also be undertaken to determine the health risks associated with different stormwater end use where the pathogen data is lacking or not available. qmra can be a useful tool for examining the potential human health risks related to rainfall events and can inform risk management practices (bichai and ashbolt, 2017) . these assessments show that there are non-trivial risks associated with the use of stormwater resources to supplement water portfolios and in some cases guidelines are not sufficient to mitigate risks (murphy et al., 2017) . this is needed as stormwater harvesting areas can create new opportunities for comingling of potential animal habitats or reservoirs for animal fecal material and human recreational environments, where transmission of fecal pathogens can occur (sales-ortells and medema, 2015; petterson et al., 2016) . while acknowledging the utility of qmra, caution must be exercised when comparing risk estimates from qmras employing different methodologies. for example, a direct comparison of annual infection risks and annual disability adjusted life years (dalys) (pppy) should be interpreted carefully as these methodologies can lead to different risk conclusions when compared to guideline values . furthermore, it has been suggested that drinking water benchmarks could be too stringent for comparison with alternative water uses in some cases and warrants consideration of the development of more applicable guideline values (mara, 2011; schoen and garland, 2015) . elevated levels of microbial contaminants in stormwater is of great concern for water safety. as a result, there is regulatory pressure to giardia spp.: toilet flushing 0.5-2.5, unrestricted irrigation 1.3-3.3, indoor use 2.5-4.5, drinking 5.4-7.4 campylobacter spp.: toilet flushing 1.4-3.4, unrestricted irrigation 2.1-4.1, indoor use 3.1-5.1, drinking 6.2-8.2 campylobacter spp.: toilet flushing 0-1.8, unrestricted irrigation 0.6-2.6, indoor use 1.8-3.8, drinking 4.6-6.6 a species not specified and based on surrogate data; dose response models for c. jejuni, s. enterica, cryptosporidium spp. were used; *only potable and non-potable exposure scenarios included remove contaminants so that risk benchmarks can be met. a variety of microbial contaminant mitigation measures can be used including the implementation of various types of stormwater infrastructure (thurston et al., 2001; struck et al., 2008) . fletcher et al. (2015) undertook a review of terminology associated with urban stormwater management in different countries. the terms reviewed included: wsud, bmps, integrated urban water management (iuwm), low impact urban design and development (liudd), low impact development (lid), green infrastructure, and sustainable urban drainage systems (suds). their review identified that whilst the concepts are all underpinned by the principles of reducing disturbance to natural hydrology and mitigating the water quality impacts of urbanisation, there are subtle differences in the scope and focus of terms (fletcher et al., 2015) . however, for the purposes of this review the terms can be considered broadly analogous and are hereafter referred to as "wsud". wsud takes an integrated approach to managing stormwater that protects public health, while also mitigating the environmental impacts of urban development and provides for improved community amenity. wsud has the objective of reducing the impact of urbanisation on the natural water cycle, and its principles can be applied at a range of scales (lloyd et al., 2002) . davies (1996) proposed that, fundamentally, wsud strives to maintain the water balance and water quality of an urbanized environment in much the same state as prior to urbanisation. the approaches taken to implement wsud will depend upon the development context and drivers for the adoption of wsud. wsud approaches often use a 'treatment train' where a series of treatment approaches are used to meet stormwater objectives. the approaches applied will depend upon the catchment characteristics, climate conditions and discharge requirements. often the initial stages of a wsud treatment train will focus on the removal of coarse sediments, which can help improve the treatment effectiveness of subsequent stages that use filtration and/or biological processes. in addition to the wsud treatment approaches summarized below, non-structural catchmentscale approaches can be used to improve quality of runoff discharged to receiving waters (wong, 2006) . this can include buffers around waterways that limit potentially polluting land uses, and the revegetation of riparian zones. for example, bryan et al. (2009) described the use of an adaptive management framework to reduce cryptosporidium risk in an agricultural catchment in south australia. although information regarding the degree of pathogen removal from various wsuds can help for water quality managers and urban planners to design and maintain systems that adequately protect public health, data available on specific lrvs of pathogens through wsud is limited (nrmmc-ephc-nhmrc, 2009 ). most studies have employed fib to derive the lrvs of microbial removal in specific wsud treatment processes and as such, and there is much less information on the removal of specific pathogens such as viruses and protozoa which have very different physico-chemical characteristics. a range of factors have an impact on the treatment capability of wsud systems. the removal of pathogens varies from system to system and therefore, it may be useful to assess individual systems in-situ to account for local variability resulting from factors such as sedimentation, sunlight exposure, water temperature, and adsorption/desorption with biofilms . peng et al., 2016 highlighted that most microbe focused studies of stormwater biofilters focus on fib, which are measured by culturebased methods, and less frequently by molecular based methods. these studies may be difficult to extrapolate to pathogens. there are few studies on the removal of pathogens, particularly viruses, in stormwater by biofiltration. peng et al. (2016) also noted the need for more studies that use field-based measurements, rather than laboratory settings, as it captures the more variable and complex features of the urban environment that influences how effective wsud approaches are likely to be in reducing pathogen loads. one key resource for lrv in wsud is the international stormwater bmp database. the database contains approximately 600 pairs of influent and effluent data for fecal coliforms and e. coli. among the 600 pairs, 100 pairs belong to e. coli from 12 sites in portland, oregon and the remaining 500 pairs are fecal coliform collected from 61 sites in california, florida, virginia, ontario, new york, texas, georgia, north carolina, and oregon. clary et al. (2008) analyzed the fecal coliform and e. coli datasets in the international stormwater bmp database and provided results on how bmps can effectively reduce fecal indicator concentrations in order to assist in meeting total maximum daily load (tmdl) goals. swales and detention basins did not appear to effectively reduce fib in effluent samples. datasets for wetlands and manufactured devices were not of adequate size to draw meaningful conclusions. the authors concluded that the ability of bmps to reduce fib varies widely within bmp categories. no single bmp appears to be able to consistently reduce fib in effluent to levels below instream primary contact recreation standard. among the bmps, retention pond and media filters appeared to have potential for bacteria removal in effluent. chandrasena et al. (2016) studied the removal of e. coli and campylobacter spp. from urban stormwater by field-scale biofilters. e. coli lrvs (average 1.23-1.39 lrvs) were greater than that of campylobacter spp. (average 0.88-0.99 lrvs) in both biofilters. the authors did not find any correlation between e. coli and campylobacter spp. log removal performance suggesting that single organisms should not be employed to understand pathogen removal in urban stormwater treatment systems. such variations may affect performance evaluation as well as the impact of other factors including the selection of plants, use of a submerged zone in biofilters, and operation under wet vs. dry conditions chandrasena et al., 2016) . generally, a one log 10 removal of fib and pathogens can be expected if biofilters are properly designed accordingly to local guidance (bichai and ashbolt, 2017) . however, the performance of such systems can be site specific, and therefore, undertaking in situ validation of specific devices has been recommended (payne et al., 2015) . while individual wsud technologies performances are available, there is an expectation that there would be an improved or increased performance for the removal of contaminants when water is passed through a series of wsud technologies prior to (re)use . this not only can increase the amount of contaminants removed, but can also enable a level of redundancy to be built in so that if treatment of an individual wsud technologies declines, the resulting reduction in treatment capacity is covered by the rest of the wsud treatment system. in addition, residence time is important for the removal of microorganisms, so the longer water is held within a wsud treatment system, the greater the pathogen removal rates. table 4 provides information on the studied removal capacity of a range of wsud treatment systems. while there is variability in the removal capacity of the different reported wsud systems, in general all of these systems achieved 0.5 to 1 lrv for fib and the bacterial pathogen campylobacter. the results also show that bacterial removal is faster (or higher) than viral and protozoan pathogens, which tend to be more resistant to treatment processes, and therefore more able to survive through the different wsud treatments. this is due to the differences in size surface characteristics, mode of reproduction and life cycle of viruses and protozoa which are different than those of bacteria (hoff and akin, 1986) . in general, sequential treatment systems with a series of ponds, wetlands or combinations tend to improve pathogen removal from source water. for example, reinoso et al. (2008) evaluated the removal of a variety of traditional and alternative fecal indicators such as coliphages, total coliform, e. coli, fecal streptococci and c. perfringens and pathogens such as cryptosporidium spp. and giardia spp. from domestic sewage in a treatment train including pond storage followed by surface and subsurface wetlands, with the overall cryptosporidium and giardia removal efficiency found to be as high as two log 10 . a new potential wsud treatment component currently being studied is the addition of heavy metal (e.g., copper) labelled zeolite to filtration bed media. laboratory research has demonstrated that copper coated zeolite can have lrv capability for bacteria such as e. coli greater than three log 10 (li et al., 2012) . stormwater can also be contaminated with viral and protozoan pathogens, both of which have higher treatment requirements than bacteria. however, the information on the effect of zeolites coated with heavy metals on these enteric non-bacterial pathogens is very limited. silver/copper coated zeolites could reduce coronavirus by 2-3 lrvs (bright et al., 2009 ) and silver-impregnated filtration pots reduced giardia and cryptosporidium by at least 96% (~1.5 lrv) (adeyemo et al., 2015) . more research would be needed to assess the treatment potential of copper-coated zeolite on a range of enteric viruses and protozoa under in-field conditions before its use could be justified as beneficial for the cost, particularly for the removal of pathogens. stormwater harvesting systems generally require some level of treatment to minimise operational risks. additional treatment may also be required for higher exposure uses to manage human health and environmental risks. the operational risks relating to stormwater quality are usually managed by the use of bmps/wsuds. for example gross pollutant traps and vegetated swales to remove sediment and leaves entering the stormwater harvesting scheme and potentially blocking pipes, irrigation nozzles or drip irrigation systems, or damaging pumps. use of wetlands and bio retentive systems can also assist in reducing high loads of organic matter (e.g. leaf fall) as well as removing nitrogen and phosphorus through phytoremediation. additional levels of treatment are often required to manage human health risks, where stormwater from a sewered residential catchment is used for public, open-space irrigation (e.g. in schools and sporting ovals). here, human health risks can be managed by the use of on-site access controls to minimise exposure to irrigation water. for example, the use of withholding periods on public recreation ovals has been recommended to reduce the risks from pathogens (page et al., 2014b) . additional treatments may be required for higher exposure usages, for example the australian guidelines for stormwater harvesting and reuse (nrmmc-ephc-nhmrc, 2009) describes the derivation of these criteria in terms of lrvs and also lists default lrv values for a range of engineered treatments. these accepted default lrv tables can be then used along with catchment specific knowledge where possible exposure controls are used to determine the required level of treatment for pathogens. for example, page et al. (2012) reported that risks from viruses have the highest required lrv targets and if they are met then protozoan and bacterial lrv targets will also be met. it was reported that for open space irrigation requires b2.0 lrv is sufficient for stormwater recycled via an aquifer and this can potentially be managed using chlorination and exposure controls. however, if in the same system where stormwater is recycled via an aquifer were to be used for drinking water, a lrv of 5.5 would be required to manage human health risks from viruses (page et al., 2014c) . generally these default lrvs apply where there has been no stormwater catchment-specific assessment of the health risks posed by the quality of the stormwater. where such a site specific risk assessment has been performed, alternative treatment could be adopted (e.g., lower lrv targets may be adopted where microbial source tracking has found negligible sewage contamination in a catchment). • monitoring of fib in stormwater may not be useful unless synergistically used with mst marker genes such as hf183, crassphage or lachno3 which are able to differentiate between sources of fecal contamination. this will provide additional information on the human health risks associated with stormwater from point and non-point sources of fecal contamination. identifying and quantifying sources of human sewage in stormwater is most important followed by cattle due to the presence of a wide array of enteric viruses and zoonotic pathogens in these sources. • the concentration of pathogens in stormwater, outfalls and receiving environmental waters can be high, especially in urban areas. monitoring of traditional fib takes 24-48 h and does not provide real-time information on the quality of recreational water. this is important from a human health perspective. swimming area closure causes economic losses. therefore, it is recommended that a rapid pathogen monitoring toolbox and standardized methods need to be developed that are able to quantify a number of reference pathogens in waterbodies with increased accuracy, reliability, and less technical training under various conditions. the toolbox can be used either in the laboratory or in the field to provide a rapid assessment whether the stormwater from a particular storm event presents a hazard to public health. • most of the stormwater quality monitoring studies focused on determining the concentrations of pathogens in urban stormwater. however, more data is required on the concentration of pathogens in stormwater sourced from a range of land uses. while sewage discharges are relatively well characterized, there remain gaps in our understanding of runoff from nonpoint sources. more studies are required to determine the concentrations of zoonotic pathogens in stormwater. • fecal contamination in stormwater is largely dependent on the land uses and mostly include sewage, septage and various animal feces. therefore it is imperative to determine the sources of contamination. this will in turn provide a basis for cost-effective remediation and information on the immediate human health risks in stormwater impacted waters. currently used fib monitoring approaches are inadequate due to their presence in both human and animal feces. an mst toolbox comprised of various human and animal fecesassociated marker genes needs to be employed which will allow managers to quickly identify the relative contribution of point and nonpoint sources of fecal contamination. • the quality of stormwater in terms of microbial contaminants is poorly understood. microbial risk will be the dominant acute health risks on stormwater reuse due to the risk of waterborne pathogens (hrudey and hrudey, 2014) . however, in some cases, chemical risks may be the driving health concern and relationships between multicontaminant exposures should be explored. few qmra studies addressing potable and non-potable exposures to stormwater were available. most of the qmra studies are based on conservative assumptions. more data are required on the concentrations of pathogens and recovery from water samples across sites and stormwater hydrographs. in addition, improved understanding of the influence of catchment characteristics and baseline levels of pathogens, meteorological factors, and decay of pathogens is required for accurate qmra estimates. • different types of wsud and bmps are able to reduce microbial contamination, however, reliable information is still lacking on the performance of these treatment barriers. standardized natural treatment validation protocol needs to be developed. most studies determined the efficacy of wsud or bmps on the removal of microorganisms using fib, while one or two studies investigated the lrvs of protozoa pathogens such as cryptosporidium spp. or giardia spp. given the differences in size and characteristics of different groups of pathogens, it is unlikely that fib lrvs will be representative for pathogens especially enteric viruses. therefore, studies should focus on determining the removal of enteric viruses and other pathogens (i.e., bacterial and protozoans) of interest to determine the removal rates through different types of wsud and bmps, simultaneously. these data will be important for evaluating the effectiveness of wsud/bmps for reducing microbial contaminants in the receiving environments and can support improved qmra models. the evaluation will focus not only on the performance of individual component of wsud/bmps but also on a series of different types of bmps. • little is known regarding the decay of pathogens in stormwater or outfalls, and the relative differences in persistence between fib, pathogens, and host-associated markers. as stormwater becomes aged, pathogens will start to decay and as result, the human health risks will also decrease. studies should focus on determining the decay of pathogens in stormwater and outfalls or recreational water contaminated with stormwater. in-situ 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