Maataloustieteellinen Aikakauskirja Vol. 59: 379—385, 1987 The fluoride content of Finnish honey SEPPO LAUREMA and ANNA-LIISA VARIS Department of Agricultural and Forest Zoology, University of Helsinki, SF-00710 Helsinki, Finland Abstract. The content of fluoride was determined with an ion-specific electrode on 59 samples of honey from 47 localities in Finland. The concentrations ranged from 25 to 550 /tg/kg and the mean for all the localities was 85.7 jrg F“/kg fresh weight honey. The concentrations were lowest in eastern and northern Finland, where the amount of fluoride in the soil is small, and higher on the coast and areas where more fluoride occurs in the groundwater and bed- rock. However, the highest levels of fluoride in honey were detected in the vicinity of Helsinki and some other places where the amount in the groundwater is not especially high. The higher levels in some honey may be due to fluorides introduced into the environment by the activity of man. The effects of fluoride on human health are discussed. Index words: honey, fluoride, groundwater Introduction Fluorine is an element which occurs in com- pounds everywhere in the lithosphere, but only small amounts are generally found in the biosphere. Fluorine is an important constit- uent of teeth and bones, and has been consid- ered essential to animal life (Who 1984). The best known of its biological functions are con- nected with the use of fluoride in the preven- tion of dental caries (Murray 1986). Es- pecially at higher concentrations, compounds of fluorine are harmful to living organisms and can occur as environmental pollutants (Lillie 1970, Weinstein 1977, Who 1984). The total daily fluoride intake of adult man ranges from about 0.5 to 5.0 mg, mainly de- pending on its amount in drinking water (Who 1984). In Finland the daily intake of fluoride in food, excluding drinking water, was estimated to be 0.56 mg (Koivistoinen 1980). As regards the caries-inhibiting effect, the optimal concentration of fluoride in drink- ing water in a temperate climate is approxi- mately 1 mg/litre, and in many areas water is artificially fluoridated to attain the optimal level (Who 1984, Murray 1986). In Finland the fluoride content in groundwater varies between 0.01 and 6.0 mg, and the average is 0.1 mg/litre (Vuorinen et ai. 1986). 379 JOURNAL OF AGRICULTURAL SCIENCE IN FINLAND https://www.c-info.fi/en/info/?token=Dt0xQpDZMh9lEGy_.domIPDdjDkJGQSFFi7bcTw.jKkxtopLXMazEA-FIMbjyCkd5WkiK6yiJjvjocf1zpATgKXW1ynyGBHuHIII6_1W338aWDV-QU0-OGBN6M0SRxVkScSx29Z5Pv-kLni_ZJAiYWKi7Tk-Z4c-q6YGXdd-MVVNqAI1XDdEeUQPAjJX1-RiJ_GpIhl8BMqPPdxOHosIio_1HfIGMeYhWYFB35aA 380 Recently it has been established that the caries-preventive effect of fluoride is greatest when it is consumed together with cariogenic sugar products (Luoma 1985). As honey is a sugary product, its fluoride content can affect its cariogenic potential. Hardly anything is known, however, about the normal levels of fluoride in honey. For example, the compre- hensive handbook of honey (Crane 1975) does not mention fluoride among the over 180 substances so far detected in honey. The aim of the present study was to determine fluoride in honey samples collected from different areas of Finland, and to compare the results with thefluoride content of the groundwater. This study is a part of the investigation of Finnish honey commenced by Varis et ai. (1982, 1983). Materials and methods Honey samples The bulk of the honey originated from the years 1977 and 1978 and has been described in more detail in connection with the analysis of other constituents (Varis et ai. 1982, 1983). The honey samples were stored in a deep freeze until analysed. The samples for the determinationof fluoride were selected to be representative with respect to geographical distributionand the occurrence of fluorine in Finnish soils. In several cases samples from the same locality were pooled before the analysis. The Espoo and Helsinki honey in- cluded samples from the years 1985 and 1986. The water content of the samples averaged 17.6 % (Varis et ai. 1983). Analysis for fluoride The determinations of fluoride were per- formed by means of a fluoride ion-specific electrode, Orion 94-09, connected with a 901 ionalyzer and 90-01-00 reference electrode (Orion Research Incorporated, Cambridge, Massachusetts 02139). The measurements were made on 20 % (w/v) solutions of honey in the presence of 0.2 M sodium citrate/HCI buffer pH 5.6 at room temperature (20 ± I°C) under continuous magnetic stirring (Kauranen 1977). The electrode response was recorded until the change was no more than 0.1 mV/min, which generally took from 10to 30 min. Standards containing 0.005—0.5 ppm F - as sodium fluoride were measured in the same conditions and the fluoride concentra- tions in the samples were evaluated from a standard curve on semilogarithmic paper. All the samples were measured at least twice. The reliability of the method was also checked by addition of a known amount of sodium fluo- ride to a measured sample. The concentrations of fluoride in melted snow were determined similarly. The reagents were pro analysi grade (E. Merck, Darmstadt) and the solutions were made with double distilled water. The solu- tions were prepared and stored in polyethylene containers. Results and discussion The concentrations of fluoride in 59 samples of honey from 47 localities in Finland varied from 25 to 550 ng/kg and the mean for all lo- calities was 85.7 jtg/kg fresh weight honey (Table 1, Fig. 1). The concentrations were lowest in eastern and northern Finland, where the amount of fluoride in the bedrock is low, and higher in localities where more fluoride occurs in the soil. However, the highest con- centrations of fluoride in honey were detected in the vicinity of Helsinki and some other places where its amount in the groundwater is not particularly high (Table 1, Figs. 2 and 3). The reasons for these higher values are not completely clear, but evidently fluoride from other sources than the local bedrock has af- fected its amount in the honey samples. In some cases the great local variation in the fluoride content of the soil can also have affected the results. On average the fluoride content of the honey was about 20 % of that of the groundwater. No correlation was found between the fluoride content and the pollen spectrum of the honey. So far only a few investigations have been made of the amount of fluorine in honey, and these were mainly made on honey subject to environmental pollution. Tong et al. (1975), who used spark source mass spectrometry to study the effects of pollution on mineral ele- ments in honey in the USA, reported, without closer specification, that the concentrations of fluorineranged from < 1 to 8900 /rg/kg fresh weight. Mayer et al. (1986) have found up to 1200 /ig F" in honey from a fluoride pollu- tion area in Puyallup Valley northwestern USA, and 300 /tg/kg in honey from control colonies outside the area. At these levels fluo- ride did not affect the colony vigor or honey production. A mixed sample of Finnish honey was analysed in connection with the investigation of the mineral element composition ofFinnish foods (Koivistoinen 1980). The fluoride con- tent in this sample, as determined with an ion- specific electrode after ashing, was found to be 800 /ig/kg, or about 10 times as high as the average concentration in the present study. The higher level of fluoride in the ashed sample may indicate that only a part of the fluorine in honey is directly detectable with the electrode. As the result is based on only one determination, however, the possibility of an experimental error cannot be excluded. Ashing was also tried in the present study, but proved to be laborious and apt to cause contamina- tion by extraneous fluoride. The principal source of the mineral elements of honey is the nectar of flowers, and the mineral content of honey is thus dependent on Fig. I. The content of fluoride in Finnish honey. The numbers refer to the localities in Table I. Fig. 2. The content of fluoride in Finnish groundwater according to the investigation of the Geological Survey of Finland (Vuorinen et al. 1986). 381 Table 1. The content of fluoride in honey and groundwater in Finland. The concentrations in honey are in most cases based on one pooled sample. If more than one sample was analysed from the same locality, the results are means of the determinations: No. 11 25.0 (1977), 57.0 (1978); No. 30 47.5,80.5,71.0(1977), 165.0, 100.0 (1978); No. 34 95.0 (1978), and another apiary 109.5 (1985), 120.0(1986); No. 35 128.5 (1977), 91.5 (1978); No. 43 145.0(1977), 180.0 (1978); No. 46 230.0 (1977), 210.0 (1978); No. 47 550.0 (1977), 218.5 (1985), 305.0 (1986). The concentrations in groundwater are based on the investigations of the Geological Survey and are means ± SE of the content of fluoride in wells or springs located not more than 10km from the apiary. In ground- water the lower limit of determination was 0.1 mg F —/litre. The number of samples is given in parentheses. No. Locality Honey Year Groundwater "g F~/kg 1977 1978 mg F ~/Mtre 1 Ruokolahti 25.0 x 0.11+0.010(8) 2 Polvijärvi 26.2 x 0.24 (1) 3 Rovaniemi mlk 28.0 x 0.12 (1) 4 Kitee 30.3 x 0.12±0.014 (5) 5 Vuolijoki 32.0 x 0.15 ±0.052 (4) 6 Parikkala 32.5 x 0.61 ±0.169 (21) 7 Asikkala 37.0 x 0.17 ±0.066 (5) 8 Ylöjärvi/Kuru 38.0 x 0.31 ±0.086 (16) 9 Heinola mlk 39.5 x o.lo±o (3) 10 Ypäjä 39.5 x x 0.50±0.218 (9) 11 Imatra 41.0 (2) x x 0.41 ±0.186 (10) 12 Lieksa 42.5 x o.lo±o (8) 13 Längelmäki 43.0 x x 0.90±0.800 (2) 14 Pietarsaari mlk 43.5 x 0.70 ±0.070 (3) 15 Liperi 44.0 x 0.20 ±0.090 (4) 16 Kangasala 45.0 x x 0.22±0.055 (15) 17 Kalajoki 47.5 x o.lo± (2) 18 Kälviä 49.0 x 0.26 ±0.165 (2) 19 Mustasaari 49.0 x 0.47 (1) 20 Mikkeli mlk 54.5 x 0.13 ±0.025 (5) 21 Huittinen 59.5 x o.lo±o (2) 22 Hattula 60.5 x x 0.17 ±0.057 (10) 23 Mäntyharju 61.5 x x 0.24±0.118 (6) 24 Eurajoki 64.2 x 0.85 ±0.257 (8) 25 Merikarvia 68.5 x 0.12±0.015 (2) 26 Siilinjärvi 75.5 x x 0.14±0.037 (3) 27 Ähtäri 82.5 x 0.10 + 0 (7) 28 Porvoo mlk 85.5 x x 0.15 ±0.055 (2) 29 Keminmaa 89.4 x 0.14 ±0.040 (2) 30 Jyväskylä 92.8 (5) x x 0.10 (1) 31 Lohja 93.0 x 0.12 ±0.022 (4) 32 Elimäki 95.5 x 1.40±0.184 (13) 33 Kokemäki 100.5 x x 0.13±0.019 (8) 34 Espoo 108.2 (3) x 0.43 ±0.178 (6) 35 Pyhtää 110.0 (2) x x 2.67±0.592 (3) 36 Hausjärvi 117.5 x x 0.51 ±0.140 (13) 37 Valkeala 119.0 x 1.54±0.178 (14) 38 Loviisa 120.0 x x 1.28 ±0.361 (4) 39 Geta 121.0 x 1.72 + 0.313 (6) 40 Ilmajoki 125.0 x x o.lo±o (3) 41 Vehkalahti 134.0 x 2.45 ±0.355 (17) 42 Nakkila 154.0 x 0.24±0.058 (12) 43 Anjalankoski 162.5 (2) x x 1.74±0.198 (10) 44 Loppi 167.0 x 0.19±0.092 (4) 45 Siuntio 195.0 x 0.13 ±0.021 (4) 46 Vantaa (Tikkurila) 220.0 (2) x x 0.17 ±0.044 (3) 47 Helsinki (Viikki) 357.8 (3) x 0.39 ±0.145 (3) Mean±SE 85.68 + 9.08 0.495 ±0.091 382 the plants from which the nectar originates. According to Weinstein (1977), the major site of fluoride accumulation in plants is the leaf, in which the concentration of fluoride gen- erally ranges from 0.5 to 25 mg/kg dry weight. In vegetables in Finland, the fluoride content has been found to vary from 0.02 to about 1 mg/kg fresh weight (Koivistoinen 1980). The amount of fluoride in the vegetation depends on several factors, and often no close rela- tionship has been found between the concen- tration of fluoride in the soil and that in the plant (Weinstein 1977). Phosphate fertilizers, which generally contain fluoride as an im- purity, can increase the amount of fluoride in soil and plants, and there is some evidence that fertilization can also otherwise increase the amount of fluoride in plants (Gabovich and Ovrutskiy 1969). Therefore, fertilization could also increase the amount of fluoride in honey produced in intensively cultivated areas. Although small amounts of fluoride are beneficial to the health and normal develop- ment of man and higher animals, larger amounts are toxic to animals and plants, and harmful effects of fluorides have often been observed in the environment. Insects are susceptible to fluoride, and poisoning can oc- cur through fluoride-containing pesticides or industrial emissions (Lillie 1970, Alstad et al. 1982). The toxicity of fluoride to bees depends on several factors, but generally the LD 50 varies between 5 and 8 g per bee (Maurizio 1960). Fluoride is not a serious environmental problem in Finland, but fluoride emissions have been observed to affect the vegetation in the vicinity of fertilizer factories at Siilinjärvi and Oulu (Kärenlampi et al. 1982). Symptoms of fluoride intoxication were also noticed in the vicinity of a porcelain factory at Tammi- saari in the 1970’5. A mixed sample of honey from two apiaries at Siilinjärvi was analysed in the present study, but the amount of fluo- ride in this sample (No. 26) was not particu- larly high, evidently because the apiaries were located more than 3 km from the factory (cf. Kauranen 1978). The high level of fluoride in honey from Viikki (No. 47) was unexpected, because the bedrock in the area is not rich in fluoride. The apiary is located near the seashore in the neighbourhood of Helsinki, but no symptoms ofpollution are evident in the area. However, determinationof fluoride in the snow in spring 1987 indicated that the concentrations were elevated around the city and especially in the vicinity of a porcelain factory located 3 km from the apiary of Viikki (Table 2). At the end of the 1970’s the factory started to use kaolin containing less fluoride, which could explain the smaller amounts of fluoride in honey from Viikki in the 1980’s. Air pollution could also explain the higher levels of fluoride in some other honey samples in the present study, e.g. those from Tikkuri- la, Nakkila and Jyväskylä. The variation in the fluoride content of honey from the same apiary at Jyväskylä (No. 30) could be ex- plained by periodical pollution. Even the highest levels of fluoride now de- tected in honey were so low that no effect on Fig. 3. The correlation between the content of fluoride in honey and groundwater. The numbers refer to the localities in Table 1. 383 Table 2. The content of fluoride in snow in the vicinity of Helsinki and the apiaries at Viikki and Tik- kurila at the end of March 1987. Fluoride fig F~/kg snow Location The city of Helsinki (Eläintarhan- puisto) 16 The apiary of Viikki, 7 km NE of the city II A park near a porcelain factory, 3 km SW of the apiary of Viikki The apiary of Tikkurila, 14 km N of the city 26 9 6Archipelago, 16 km SW of the city human health can be expected. The concen- trations were on average around the level found in milk and vegetables in Finland (Koi- vistoinen 1980). This amount is only 10 % of the optimal concentrations of fluoride in drinking water and 1 % of the level found to afford significant protection against dental caries in sugar products (Luoma 1985). There is experimental evidence that the cariogenic effect of honey is approximately the same as that of sucrose (Birkhed et al. 1979; Shannon et al. 1979). Acknowledgements. We are indebted to Mr. Heikki Rainio, M.A. for advice on the fluoride analyses per- formed at the State Institute ofAgricultural Chemistry. This study was supported financially by the Juho Vainio foundation. References Alstad, D.N., Edmunds, G.F., Jr. & Weinstein, L.H. 1982. Effects of air pollutants on insect populations. Ann. Rev. Entomol. 27: 369—384. Birkhed, D., Edwardsson, S. & Forslund, B. 1979. Honung en kariogen biprodukt? Tandläkartidningen 71: 978—985. Crane, E. (Ed.) 1975. Honey a comprehensive survey. 3rd Impress. Heinemann, London, 608 p. Gabovich, R.D. & Ovrutskiy, G.D. 1969. Fluorine in stomatology and hygiene. Bethesda, Maryland, US De- partment of health, education, and welfare, 1028 p. (DHEW Publication No. (NIH) 78—785, 1977). Kärenlampi, L., Hyvärinen, A. & Kauranen, P. 1982. Fluoride accumulation in the leaves of deciduous trees around the Siilinjärvi fertilizer factory in central Fin- land. Savonia 5: 11—14. Kauranen, P. 1977. The use of buffers in the determi- nation of fluoride by an ion-selective electrode at low concentrations and in the presence of aluminium. Anal. Lett. 10: 451—465. 1978. Fluoride deposition in snow in the surroundings of a mixed fertilizer factory. Chemosphere 6: 537— 547. Koivistoinen, P. (Ed.) 1980. Mineral element composi- tion of Finnish foods. Acta Agric. Scand., 22 (Suppl.). Lillie, R.J. 1970. Air pollutants affecting the perfor- mance of domestic animals, a literature review. Agri- culture Handbook No 380. U.S. Department of Agri- culture, Washington DC, 109 p. Luoma, H. 1985. Fluoride in sugar. Int. Dent. J. 35: 43—49. Maurizio, A. 1960. Bestimmung der letalen Dosis einiger Fluorverbindungen fiir Bienen. Zugleich ein Beitrag zur Methodik der Giftwertbestimmung in Bienenversuchen. Verhandl. IV Int. Pflanzenschutz-Kongr., Hamburg 1957 Bd 2: 1709—1713. Mayer, D.F., Lunden, J.D. & Weinstein, L.W. 1986. Evaluation of fluoride levels and effects on honey bees. Am. Bee J. 126: 832—833. Murray, J.J. (Ed.) 1986. Appropriate use of fluorides forhuman health. World Health Organization, Geneva, 131 p. Shannon, 1.L., Edmonds, E.J. & Madsen, K.O. 1979. Honey: sugar content and cariogenicity. J. Dent. Child. 46: 29—33. Tong, S.S.C., Morse, R.A., Bache, C.A. & Lisk, D.J. 1975. Elemental analysis of honey as an indicator of pollution. Arch. Environ. Health 30: 329—332. Varis, A.-L., Helenius, J. & Koivulehto, K. 1982. Pol- len spectrum of Finnish honey. J. Scient. Agric. Soc. Finland 54: 403—420. —, Helenius, J. & Koivulehto, K. 1983. Composition and properties ofFinnish honey and their dependence on the season, region, bee race and botanical origin. J. Scient. Agric. Soc. Finland 55: 451—463. Vuorinen, A., Lahermo, P. & Hatva, T. 1986. Fluoride in Finnish groundwater and its effect on the precipita- tion of iron oxyhydroxides in a pilot plant study. En- vironmental Contamination, 2nd Int. Conf., Amster- dam 1986, p. 44—46. 384 Health Criteria 36. World Health Organization, Ge- neva, 136 p. Weinstein, L.H. 1977. Fluoride and plant life. J. Occup. Med. 19: 49—78. Who 1984. Fluorine and fluorides. Environmental Ms received October 14, 1987. SELOSTUS Suomalaisen hunajan fluoridipitoisuus Seppo Laurema ja Anna-Liisa Varis Helsingin yliopisto. Maatalous- ja metsäeläintieteen laitos, 00710 Helsinki Fluori on alkuaine, joka luonnossa miltei aina esiin- tyy yhdisteinään, fluorideina. Fluoridin katsotaan olevan välttämätön luuston normaalikehitykselle ja sillä on myös merkittävä hammaskariesta ehkäisevä vaikutus. Äsket- täin on voitu todeta, että tämä vaikutus on suurin jos fluo- ridia saadaan yhdessäkariesta aiheuttavien sokerituottei- den kanssa. Suuremmissa määrissä fluorideilla on hait- tavaikutuksia ja monissa tapauksissa fluorin yhdisteet ovat esiintyneet ympäristömyrkkyinä. Eräiden havaintojen mukaan hunajassa voi esiintyä merkittäviä määriä fluoria. Tiedot hunajan sisältämän fluorin määrästä ovat kuitenkin erittäin puutteelliset. Sen vuoksi on Helsingin yliopiston maatalous- ja metsäeläin- tieteen laitoksella osana laajemmasta suomalaisen huna- jan koostumusta koskevasta tutkimuksesta selvitetty fluo- ridin määrä 59 hunajanäytteestä47 paikkakunnalta. Tut- kitut hunajat olivat pääosin peräisin vuosilta 1977 ja 1978. Mittaukset tehtiin Valtion maatalouskemian laitoksella fluoridispesifistä elektrodia käyttäen. Fluoridin määrä tutkituissa näytteissä vaihteli 25:stä 550:een fig/kg japakkakunnittain laskettu keskiarvo oli 85.7 gg F~/kg hunajaa. Pitoisuudet olivat pieniä itä- ja pohjois-Suomessa, missä fluorin määrä maaperässä on vähäinen ja suurempia rannikoilla ja rapakivialueilla, mis- sä fluoria esiintyy enemmän maaperässä japohjavedes- sä. Suurimmat hunajan fluoridipitoisuudet todettiin kui- tenkin Helsingin lähistöltä ja eräiltä muilta paikkakun- nilta, missä fluorin määrä maaperässä ei luonnostaan ole kovin korkea. Helsingin ympäristössä lumesta keväällä 1987 tehdyt mittaukset viittaavat siihen, että suuremmat fluoridin määrät hunajassa voivat osittain johtua ilman epäpuhtauksista.Fluorin määrää maaperässä voi myös lisätä sen esiintyminen epäpuhtautena fosforilannoitteissa. Kaikenkaikkiaan fluoridin määrä suomalaisessa huna- jassa näyttää olevan niin pieni, ettei sillä ihmisen ravit- semuksen kannalta ole merkitystä. Keskimäärin pitoisuu- det hunajassa ovat samansuuruisia kuin maidossa ja vi- hanneksissa ja suurimmatkin todetut määrät pienempiä kuin fluoridin suositeltu pitoisuus juomavedessä. Näin ollen hunajan sisältämällä fluoridilla ei voi myöskään olla merkittävää hammaskariesta estävää vaikutusta. 385