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Summer 2006 Vol. 6 No. 2



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©Frank Maresca/Images.com Too Much of a Good Thing


A National Research Council committee recently considered the issue of fluoride in drinking water. Not whether fluoride should be added to water for the dental health benefits it provides -- an issue that has caused much controversy in many communities. Rather, the committee looked at what happens when there is too much naturally occurring fluoride in drinking water.

The committee concluded in a new report that children who are exposed to drinking water containing 4 milligrams of fluoride per liter of water -- the maximum allowed by the U.S. Environmental Protection Agency -- risk developing severe tooth enamel fluorosis, a condition characterized by ugly discoloration, enamel loss, and pitting of the teeth. In the past, this condition was considered aesthetically displeasing, but not an adverse health effect. But because enamel protects teeth and underlying tissue from decay and infection, a majority of the committee said that the damage caused by severe enamel fluorosis should be deemed a toxic effect. Although two of the 12 committee members maintained that the condition should still be considered a cosmetic problem, the entire committee agreed that EPA should lower its "maximum contaminant level goal" for fluoride in order to prevent it.

About 10 percent of children in communities with water fluoride concentrations at or near 4 mg/L develop severe enamel fluorosis. In areas with 2 mg/L, up to 15 percent of children have moderate enamel fluorosis, which causes discoloration but no enamel loss or pitting. The committee said that discoloration by itself does not constitute an adverse health effect. Moderate enamel fluorosis is rare in populations exposed to water containing less than 2 mg/L of fluoride.

Children are not the only ones at risk of adverse health effects. Most of the committee concluded that a population with lifetime exposure to water with 4 mg/L or higher of fluoride is at increased risk for bone fractures. Three committee members said that more evidence was needed before drawing such a conclusion. The data on fluoride's potential to cause bone cancer is tentative and mixed, and more research is needed, the committee added.

The good news is that not many people have public drinking water supplies or wells with high levels of naturally occurring fluoride. About 200,000 Americans have water sources containing fluoride at 4 mg/L or higher, while another 1.4 million have water with 2 mg/L of fluoride. Artificially fluoridated water contains between 0.7 and 1.2 mg/L of total fluoride.   -- Bill Kearney


Fluoride in Drinking Water: A Scientific Review of EPA's Standards. Committee on Fluoride in Drinking Water, Board on Environmental Studies and Toxicology, Division on Earth and Life Studies (2006, approx. 576 pp.; ISBN 0-309-10128-X; available from the National Academies Press, tel. 1-800-624-6242; $56.00 plus $4.50 shipping for single copies).

The committee was chaired by John Doull, professor emeritus of pharmacology and toxicology, University of Kansas Medical Center, Kansas City. The study was funded by the U.S. Environmental Protection Agency.



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Copyright 2006 by the National Academy of Sciences