A national panel of scientists reported Wednesday that high levels of naturally occurring fluoride in drinking water are leaving children in some communities at risk of tooth enamel damage and adults prone to weakened bones that could lead to fractures.
The scientists unanimously recommended that the federal limit on fluoride in drinking water be lowered to protect people in communities where high levels leach into the water from natural sources, such as rocks or soil.
Many cities, including Los Angeles and many California communities, that have low levels of naturally occurring fluoride add it to water to protect against tooth decay, but they are unaffected by the new findings because the concentrations of added fluoride are much lower than the federal standard.
At the request of the U.S. Environmental Protection Agency, a panel of the National Academy of Sciences examined the EPA's standard, which allows 4 parts per million of fluoride in drinking water supplies.
About 200,000 Americans have drinking water with fluoride concentrations at or above the EPA's limit, and 1.4 million have water with levels between 2 and 3.9 ppm, including parts of Colorado, West Texas, New Mexico, Indiana and Illinois. No Californians have tap water with fluoride that approaches the amount the scientific panel found unsafe, because state regulations limit the concentration to 2 ppm.
For several decades, many have debated the safety of fluoridating water, but dentists and public health officials support it, saying it strengthens teeth and prevents cavities.
About two-thirds of Americans, or 162 million people, drink from fluoridated water supplies, which contain a fluoride concentration of about 1 ppm, much less than the amount the panel found had adverse health effects.
The panel of the National Research Council reviewed all the scientific evidence about exposure to and effects of fluoride, particularly over the last 12 years. It determined that lowering the EPA's 4-ppm limit would "prevent children from developing severe enamel fluorosis and will reduce the lifetime accumulation of fluoride into bone," which "is likely to put individuals at increased risk of bone fracture."
Dr. John Doull, professor emeritus of pharmacology and toxicology at the University of Kansas Medical Center, who chaired the panel, said the panel was not recommending a specific amount, only that it should "clearly be less than 4."
But the scientists did report that, generally, 2 ppm, half the amount the EPA allows, seems to protect most people from the health problems.
EPA officials said in a statement that they would "give serious consideration to the NRC's recommendations," calling the new report "a significant addition" to the scientific data. The EPA's request for the report was part of a six-year review of existing drinking water standards required under the Safe Drinking Water Act.
The Environmental Working Group, a nonprofit organization that opposes fluoridation because of health concerns, urged the EPA to set a stricter standard. The group reported Wednesday that some babies up to 6 months old who are fed formula mixed with fluoridated tap water receive doses that are too high.
But Doull emphasized that the panel was not saying fluoridation did or did not have health risks. "An evaluation of the safety or efficacy of those lower concentrations was outside the charge to the committee," he said.
Instead, he said the panel researched only the effects of much higher levels of fluoride that can contaminate water, mostly due to natural causes but sometimes from industrial pollution.
The panel found insufficient evidence that fluoride increased the rate of bone cancer, a threat debated for decades. They said the evidence was "tentative at best," with some studies showing a link and others not.
Instead, their concerns focused mostly on the tooth enamel of children and the potential for bone weakening in adults.
About 10% of children in communities with drinking water at or near the EPA's fluoride limit develop severe tooth enamel fluorosis, a condition involving extreme staining of developing teeth, the scientists reported. Though the threat is mostly cosmetic, the majority of the scientists on the panel deemed the condition "an adverse health effect" because loss and pitting of enamel can compromise the ability to protect teeth from decay and infection.
In Lowell, Ind., which has drinking water with about 4 ppm of fluoride, 7% of the children had at least one tooth with the worst possible score for the amount of staining from fluorosis, the report says. Similar results were found in Bushnell, Ill., and Lordsburg, N.M., at fluoride levels of 3.5 to 3.8 ppm.