Fluoride has beneficial effects on teeth at low concentrations in drinking-water, but excessive exposure to fluoride in drinking-water, or in combination with exposure to fluoride from other sources, can give rise to a number of adverse effects. These range from mild dental fluorosis to crippling skeletal fluorosis as the level and period of exposure increases. Crippling skeletal fluorosis is a significant cause of morbidity in a number of regions of the world.

Both national and international groups (USNRC, 1993; IPCS, 2002) have comprehensively reviewed available data on the metabolism and health effects of fluoride in both laboratory animals and humans. The following is a summary of the conclusions that have been developed by these groups, particularly the IPCS working group on fluorides held in May 2001 (IPCS, 2002). The reader is directed to these documents for a more detailed assessment of the data.

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Guidelines and standards

In 1984, WHO conducted an extensive review and found that there were insufficient data to conclude that fluoride produces cancer or birth defects. In addition, WHO noted that mottling of teeth (i.e. dental fluorosis) is sometimes associated with fluoride levels in drinking-water above 1.5 mg l–1 and crippling skeletal fluorosis can ensue when fluoride levels exceed 10 mg l–1. A guideline value of 1.5 mg l–1 was therefore recommended by WHO as a level at which dental fluorosis should be minimal (WHO, 1984).

The 1.5 mg l–1 fluoride guideline value that was set in 1984 was subsequently re-evaluated by WHO and it was concluded that there was no evidence to suggest that it should be revized (WHO, 1996, 2004). The 1.5 mg l–1 guideline value of WHO is not a “fixed” value but is intended to be adapted to take account of local conditions (e.g. diet, water consumption, etc.).

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• Black, G.V. and McKay, F.S. 1916 Mottled teeth: an endemic developmental imperfection of the enamel of the teeth heretofore unknown in the literature of dentistry. Dent.

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• Bucher, J.R., Hejtmancik, M.R., Todd, J.D. 2nd, Persing, R.L., Eustis, S.L. and Haseman, J.K. 1991 Results and conclusions of the National Toxicology Program’s rodent carcinogenicity studies with sodium fluoride. International Journal of Cancer, 48(5), 733–737.

• Dean, H.T. 1942 The investigation of physiological effects by the epidemiological method. In: Moulton, R.F. [Ed] Fluorine and Dental Health. American Association for the Advancement of Science, Washington DC.

• Edmunds, W.M. and Smedley, P.L. 1996 Groundwater geochemistry and health: an overview. In: Appleton, Fuge and McCall [Eds] Environmental Geochemistry and Health. Geological Society Special Publication No 113, 91–105.

• IARC 1987 Overall evaluation of carcinogenicity: an updating of IARC monographs volumes 1–42. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, Suppl. 7. International Agency for Research on Cancer, Lyon, 208–210.

• IPCS 2002 Fluorides. Environmental Health Criteria 227.World Health Organization, Geneva. Leland, D.E., Powell, K.E. and Anderson, R.S. 1980 A fluoride overfeed incident at Harbour Springs, Mich., Journal of the American Water Works Association, 72(4), 238–243.

• Li, Y., Liang, C., Slemenda, C.W., Ji, R., Sun, S., Cao, J., Emsley, C,. Ma, F., Wu, Y., Ying, P., Zhang, Y., Gao, S., Zhang, W., Katz, B., Niu, S., Cao, S. and Johnston, C. 2001 Effect of long-term exposure to fluoride in drinking water on risks of bone fractures. Journal of Bone Mineralisation Research, 16(5), 932–939.

• Mangla, B. 1991 India’s dentists squeeze fluoride warnings off tubes. New Scientist, 131, 16.

• Maurer, J., Chen, M., Boyson, B. and Anderson, R. 1990 Two-year carcinogenicity study of sodium fluoride in rats. Journal of the National Cancer Institute, 82(13), 1118–1126.

• Maurer, J., Chen, M., Boyson, B., Squire, R., Strandberg, J., Weisbrode, J. and Anderson, R. 1993 Confounded carcinogenicity study of sodium fluoride in CD-1 mice. Regulatory Toxicology and Pharmacology, 18(2), 154–168.

• NTP 1990 Toxicology and carcinogenesis studies with sodium fluoride (CAS No. 7681-49-4) in F344/N rats and B6C3F1 mice (drinking water studies). US Department of Health and Human Services, Public Health Service, National Institutes of Health, National Toxicology Programme (NTP TR 393), Research Triangle Park, North Carolina.

• Peterson, L.R., Denis, D., Brown, H., Hadler, H. And Helgerston, S.D. 1988 Community health effects of a municipal water supply hyperfluoridation accident. American Journal of Public Health, 78(6), 711–713.

• Susheela, A.K. and Das, T.K. 1988 Fluoride toxicity and fluorosis: diagnostic test for early detection and preventive medicines adopted in India. [Abstract], International Symposium on Environmental Life Elements and Health, Beijing, 89.

• USNRC 1993 Health Effects of Ingested Fluoride. US National Research Council, National Academy Press, Washington, D.C.

• USPHS 1991 PHS Review of Fluoride: Benefits and Risks: Report of Ad Hoc Subcommittee on Fluoride. Committee to Co-ordinate Environmental Health and Related Programs. US Public Health Service.

• Whitford, G.M. 1997 Determinants and mechanisms of enamel fluorosis. Ciba Foundation Symposium, 205, 226–241.

• WHO 1996 Guidelines for Drinking-water Quality. Volume 2. Health Criteria and Other Supporting Information. 2nd edition, World Health Organization, Geneva.

• WRI (World Resources Institute) 1996 World Resources, a Guide to the Global Environment: the Urban Environment. WRI/UNEP/UNDP/WB, Oxford University Press.