Upsala J Med Sci 100: 137-142, 1995 

The Significance of an Across-Shift Decrease in Vital 
Capacity-A Re-Analysis of a Study on 

Subjects Exposed to Diesel Exhaust 
Monica Dahlqvrst 

Departmen/ oJEniironinenta1 Terhnologi and Work Scienre, Royal In.mtute of lechnolog\, Sioc kholnz SKeden 

ABSTRACT 
Occupational exposure to diesel exhaust may develop acute as well as chronic lung function impairment. 

In this study, data from an earlier study on a group of subjects working at tunnel construction site were 
analyzed. The aini of h e  analysis was lo exanline the significance of an across-shift decrease in vital 
capacity with concern to other lung physiological measuremcnts. 

There were no statistically significant differences, either in the average agc, time of employment, vital 
capacity before a working shift after two days of no exposure, or the distributions of smoking habits and 
respiratory symptoms, bctween thc eight workers who had an across-shift decrease in vital capacity and 
the five workers who had not. 

Subjects with an across-shift decrease in vital capacity had a significantly greater across-shift decrease in 
residual volume and total lung capacity than subjects without an across-shift dccreasc in vital capacity. Thc 
pathophysiological mechanisms for this across-shift decrease in rcsidual volume is not fully understood. 
However, an altcrcd defence mechanism in the lung may play a role for a prolonged relenlion time for the 
particlcs in the inhaled diesel exhaust, resulting in the across-shift decrease in residual volume. The results 
thus suggest that measurements of across-shift vital capacity is of importance in identifying susceptible 
subjects with occupational exposure to diesel exhaust. 

NIRODUCTION 
Measurements of lung volumes are powerful measures to examine some features of lung function 

aKeclion. In a number of studies we have observcd acute, temporary effects on lung function in workers 
exposed to imtating air contaminants (3,6, 14. 15). These temporary effects were correlated with the 
conccntration of the air contaminants. The measurement of acute elrects from irritants on the lung function 
is of value as a complement to exposure measurement% I t  is also of great irileresl to study the medical 
importance of acute temporary effects with concern to other physiological lung function measuremcnts. 
This is not the least important matter since some of the lung function variables are highly intcrrclatcd (2, 
11) and thal am acute temporary decrease in lung function has been reported to predict a more accelerated 
decline in lung function over time (4,5). If an acute temporary effect on lung function cannot be 
associated with the exposure, i t  is possible that subjects who display a decrease are susceptible. By 
measuring lung function during a working shift or week, such subjecb may be identified and measures 
can be taken to decrease or stop the exposure. 

Diesel exhaust contains a number of substances that will efrecl the health of exposed human beings if 
the substances are present in concentrations high enough. The respiratory effects of exposurc to diesel 
exhaust include irritative effects on mucous membranes and chronic deterioration in lung function (16). 
Although the exhaust has usually been diluted with a factor about 50 timcs or more, acute, temporary lung 

137 



function effects havc been shown (13). The particles in the diesel exhaust have been reported to induce 
this acute, temporary decrease in lung function (12, 14). 

In order to evaluate possible relationships between an across-shift decrease in vital capacity and other 
lung physiological variables, data from an earlier published study were rc-analyzed (14). 

MATERIAL AND ?VETHODS 
Fifteen workers subjects, working at a tunnel construction site, took part in the initial examination with 

the aim to study hazardous effects on lung f i c t i o n  caused by exposure to particles in diesel exhaust (14). 
They were examined before B working shift, after two days of no exposure, and after two working shifts 
of exposure to diesel exhaust, with and without exposure to particles, respectively. The particles in the 
diesel exhaust were removed from the inhaled air by using a particulate respirator or a half mask during 
one of the working shifts. Official leakage value was lower than 0.1%. None of the filters retains gaseous 
substances to any appreciable extent. The examinations after exposure after a day working shift were 
carried out at the same time of the day. 

between 23 and 59 years, with an average age of 39 years. There were 1 nevcr-smoker, 4 ex-smokers and 
8 current smokers. The means (standard error of the mean) for pack-years, py, &ram tobacco consumed 
per day)*(snioking years)/20 were 8 (2), and 11 (4), for the ex- and the current smokers, respectively. 

standardized questionnaire, translated kom the MRCC questionnaire (8). 

technique (2) and provided values for vital capacity and closing volume. Total lung capacity was 
determined by planimetry, according to integration of the nitrogen wash-out curve as described by Buist 
and Ross (1). Residual volume was calculated by subtracting the vital capacity from the total lung 
capacity. The volumes were corrected to conditions of body temperature and pressure, saturated with 
water (BTPS). 

Standard statislical methods were employed, in conjunction with correlation analyses. The values 
obtained hefore a working shift were standardized with concern to age, height and smoking habits (7). 
The results of the previously published study showed an improvement in lung function when the particles 
from the diesel exhaust were removed from the inhaled air (14). These values were therefore used as 
tmexposed values in order to minimize the effects of the diurnal variation. The values obtained after a 
working shift when the workers were exposed to particles were used as exposed vuhes. Across-shift 
change in lung function in each individual was calculated according to the formula: 

Single breath nitrogen wash-out recordings were available in 13 subjects. All subjects were men 

Chronic respiratory symptoms (cough, exertion dyspnea, wheeze) were assessed by means of a 

Recordings on single breath nitrogen wash-out were carried out according to previously described 

(exposed - unexposed) 
0.5 *(exposed + unexposed) change = 100 * (%I. 

Since the aim of this study was to evaluate the significance of an across-shift decrease in vital capacity, 
the across-shift change in vital capacity was dichotomized. A change (calculated according to the 
aforementioned expression) of < 0%, signifying a decrease in vital capacity, were assigned 1, Le., 
indicating an effect. Ln the same manner, a calcuIated change corresponding to L 0% in vital capacity, i.e., 
no decrease, were assigned 0, i.e., indicating no effect. Stated p-values involved two-tailed analysis; 
differences were considered to be statistically significant at p 5 0.05. 

the workers, were comparable between the working shifts with and without exposure to particles (14). 
Daily average concentrations of carbon monoxide and nitric oxides, measured in the breathing zone of 

138 



Table 1. Daily average concentrations of gaseous and particulate air pollutants (mg/m3) in the 
breathing zone for workers exposed to diesel exhaust, with and without an across-shift change in vital 
capacity. 

I with, n=8 without, n=5 
carbon monoxide 10.7 (1.4)l 10.2 (1.4) 
nitrogen oxide 4.8 (0.5) 4.9 (0.2) 
nitrogen dioxide 1.9 (0.2) 1.9 (0.2) 
total dust 2.2 (0.3) 2.6 (0.5) 
respirable dust 1.3 (0.1) 1.3 (0.1) 

* mean (standard error of the mean) 
RESULTS 

Daily average values for the concenlrations of air pollutants were about the same magnitude for the eight 
subjects who had an across-shift decrease in vital capacity and the five subjects who had not, Table 1. 
Age, time of employment, standardized vital capacity before a working shift after two days of no exposure 
did not differ significantly between the workers who displayed an across-shift decrease in vital capacity 
and those who did not. The distributions of chronic respiratory symptoms and smoking habits were also 
similar in subjects with and without an across-shift decrease in vital capacity, Table 2. 

Table 2. Age, time of employment, vital capacity, percentages of current smokers and subjects with 
chronic respiratory symptoms for diesel exposed workers, with and without an across-shift decrease in 
vital capacily. 

time of employment (years) 

current smokers 

’ mean (standard deviation) 
vital capacity, before a working shift after two days of no exposure. standardized for age, height and smoking habils 
percentage (number of subjects) 

Subjects with an across-shift decrease in vital capacity had on the average a significantly greater across- 

The across-shift change in vital capacity was not significantly correlated with the daily average 
week decrease in residual volume and total lung capacity, Table 3. 

concentrations of the nieasurcd air pollutants (p0.6). 

139 



% 

mean (standard error of the mean) 
p<O0.O5 in comparison with subjects without an across-shill decrease in vital capacity 
p<O.OOI 10 comparison with subjects without an across-shift decrease 10 vital capacity 

with, n=8 without, n=5 

DISCUSSION 
Subjects with an across-shift decrease in vital capacity had a significantly greater across-shift decrease in 

residual volume and total lung capacity, compared to subjects without an across-shift decrease in vital 
capacity, Table 3. The average age, time of employment, vital capacity before a working shift after two 
days of no exposure (standardized for age, height, and smoking habits) (7), and the distributions of 
chronic respiratory sympmms and smoking habits were similar between subjects with and without an 
across-shift dccrease in vital capacity, Table 2. Although the examined background variables may have a 
limited value, it is not likely that, for instance chronic respiratory diseases should result in an across-shift 
decrease in vital capacity. 

There is still no generally applicable indicator of diesel exhaust exposure available (16). The exposure 
judgement of diesel exhaust traditionally has been founded on the concentrations of gaseous components, 
i.e., carbon monoxide and nitrogen dioxide or by measurements of total and respirable dust. Particles in 
the diesel exhaust have bcen demonstrated to induce acute temporary lung function impairment (12, 14). 
The across-shift change in vital capacity could thus have k n  directly related to the concentration of 
particulate matter, measured as total or rcspirable dust. The associations were weak between the across- 
shift decrease in vital capacity and the daily time-average concentrations of total and respirable dust, 
however. Daily time-average concentrations of total and respirable dust were also almost identical between 
subjects with and without an across-shift decrease in vital capacity, Table 1. Despite the limitation of the 
measured air pollutants in order m describe the level of diesel exhaust exposure it seems not probable that 
diffcrcnces in exposure should have inlluenced the finding that subjects with an across-shift decrease in 
vital capacity also had a greater across-shift dccrcase in residual volume and total lung capacity. Therefore, 
it seems likely to assume that the across-shift decrease in vital capacity indicates a higher susceptibility, 
independently of the exposure level. 

The data available to us are not sufficient to explain the pathophysiological mechanisms behind the 
across-shift decrease in residual volume and total lung capacity in subjects with a dccrcasc in vital 
capacity. A decreased residual volume may, besides a decreased vital capacity and total lung capacity, be 
found in subjects with a restrictive lung function impairment. Occupational exposure to diesel exhaust 
results mainly in decreased lung volumes, suggesting a restrictive impairment. This sccms to be true for 
acute as well as chronic effccts on thc lungs (16). Short-term exposure to diesel exhaust may also result in 
a decreased number of alveolar macrophages and a rcduction in the phagocylic activity in humans (9). The 
altered defence mechanism in the lung may result in a slower clearance and thus a prolongcd tissue 
interaction with the particles. A prolonged time o f  retention of compounds in the lungs has been suggested 
to pose a health hazard for humans exposed to organic pollutants in the environment (10). The across-shift 

residual volume 
total lung capacity 
closing volume 

140 

-19.3 (6.5)1.2 7.9 (7.3) 
-4.9 (0.8)3 4.3 (1.3) 
-1.2 (8.2) 15.1 (11.0) 



shift decrease in residual volume and total lung capacity, in subjects with an across-shift dccredse in vital 
capacity may thus he the result of a prolonged particle deposition in the alveoli. 

capacity is of importance in identirying susceptible subjects with occupational exposure to diesel exhaust. 
Howcver, the result may be interpreted with caution since the number of studied subjects is pretty small. 

In conclusion, the findings in the present analysis suggest that measurements of across-shift vital 

1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

1 1  

12 

13 

14 

15 

16 

REFERENCES 

Buist, A. S .  & Ross, B.: Predicted values for closing volumes using a modified single breath 
nitrogen test. Am Rev Respir Dis 107: 744-752, 1973. 
Dahlqvist, M., Alexandersson, R., Nielsen, J. & Hedenstiema, G.: Single and multiple breath 
nitrogen wash-out - closing volume and volume of trapped gas for detection of early airway 
obstruction. Clin Physiol9: 389-398, 1989. 
Dahlqvist, M., Johard, U., Alexandersson, R., nergstrom, B., Ekholm, U. Milosevich, B., 
Tornling, G. & Ulfvarson, U.: Lung function and precipitating antibodies in low exposed wood 
trimmers in Sweden. Am J Ind Med 21: 549-559, 1992. 
Dahlqvist, M. & Ulfvarson, U.: Acute effects on forced expiratory volume in one second and 
longitudinal change in pulmonary function among wood trimmers. Am J Ind Med 25: 551-558, 
1994. 
Dahlqvist, M., Tornling, G., Plato, N. & Ulfvarson, U.: Across-week effects on forced expiratory 
vital capacity is correlated to longitudinal change in pulmonary function. Reanalysis of studies on 
isocyanate-exposed car painters. Occup Environ Mcd (accepted for publication), 1994. 
Dahlqvist, M., Ulfvarson, U., Bergstrom, B. & Ekholm, U.: Temporary effects on lung function in 
welders engaged in cored wire welding. Occup Hyg 1 :  119-126, 1994. 
Hedenstrom, H., Malmberg, P. & Fridriksson, H. V.: Reference values for lung function tests in 
men: Regression equations with smoking variables. Upsala J Med Sci 91: 299-3 10, 1986. 
Medical Research Council's Committee on the aetiology of chronic bronchitis.: Definition and 
classification of chronic bronchitis for clinical and epidemiological purposes. Lancet i: 775-779, 
1965. 
Rudell, B., Sandstrom, T., Stjernberg, N. & Kolmodin-Hedman, B . :  Controllcd diesel exhaust 
exposure in an exposure chamber: Pulmonary effects investigated with bronchoalveolar lavage. J 
Aerosol Sci 21 (suppl 1): 411-414,1990. 
Sun, J. D., Wolff, R. K . ,  Kanapilly, G. M. & McClellan, R. 0.: Lung retention and metabolic fate 
of inhaled bennzo(a)pyrene associated with diesel exhaust particles. Toxicol Appl Pharmacol73: 48- 
59, 1984. 
Teculescu, D. B., Pham, Q. T. & Hannhart, B.: Tests of small airway dysfunction: their correlation 
with the "conventional" lung function tests. Eur J Respir Dis 69: 175-187, 1986. 
Ulfvarson, U. & Alexandersson, R.: Reduction in adverse effect on pulmonary function after 
exposure to filtered diesel exhaust gases. Am J Ind Med 17: 341-347, 1990. 
Ulfvarson, U., Alexandersson, R., Aringer, L., Svcnsson, E., Hedenstiema, G., Hogstedl, C., 
Holmberg, R ,  RosCn, G. & Sorsa, M.: Effects of exposure to vehicle exhdust on health. Scand J 
Work Environ Health 13: 505-512, 1987. 
Ulfvarson, U., Alexandcrsson, R., Dahlqvist, M., Ekholm, U. & Rergstrom, B . :  Pulmonary 
function in workers exmsed lo diesel cxhausls: The effect of control measures. Am J Ind Med. 19. 
283-289, 3991. 
Ulfvarson. U.. Alexandersson. R.. Dahlavist. M.. Ekholm. U.. Berestrbm. B. & Scullman. J.: 
Temporary health effects from'exposue lo water-borne paints. Scandv J Work Environ Health, 18, 
Ulfvarson, U. & Dahlqvist, M.: Pulmonary function in workers exposed to diesel cxhausl. In P. 
Cheremisinoff (ed) Encyclopedia of Environmental Conlrol Technology. Gulf Publishing, NJ, USA. 

376-387, 1992. 

pp 645-671, 1994. 

Address for reprints: 
Monica Dahlqvist 
Department of Environmental Technology arid Work Science 
Koyal Institule of Technology 
S-100 44 Stuckholm 

141