On March 22, 2006, the National Academies’ National Research  Council (NRC) released a report that  evaluated the United States Environmental Protection Agency (EPA) standards  for maximum levels of naturally occurring fluoride in drinking  water. The EPA will review the report to determine if changes are necessary to the agency’s standards for the fluoride levels in public drinking water.

The report reviewed toxicologic,  epidemiologic, and exposure data relating to naturally occurring  fluoride in water. It also presented information on fluoride content in other sources as well, including food, beverages, and dental products. The NRC was asked to examine whether the  amount of naturally occurring fluoride currently allowed in drinking water poses a health risk. The report focused on the maximum contaminant level goal (MCLG), which is currently set at 4 parts per million (ppm)—equivalent to 4 milligrams of fluoride per liter of water—for naturally occurring fluoride in drinking water.
In the report, the NRC also evaluated the rate and severity of enamel fluorosis and noted that while 10% of children in communities with water fluoride levels at or near 4 ppm exhibited severe dental fluorosis, at 2 ppm severe dental fluorosis was effectively eliminated. Those concentrations are significantly higher than the optimal fluoride levels for caries prevention (0.7 to 1.2 ppm), as established by the United States Public Health Service more than 40 years ago. The NRC report also examined other possible adverse health effects associated with high levels of fluoride, including musculoskeletal and endocrine effects, genotoxicity, carcinogenicity, reproductive and developmental effects, neurotoxicity, and neurobehavioral effects.

Although the report states that more research is necessary, it did confirm that high concentrations of naturally occurring fluoride are a risk  factor for dental fluorosis and may place some individuals at increased risk for bone fractures and possibly skeletal fluorosis. On the basis of this review, the NRC recommended that the current MCLG for fluoride in drinking water be lowered.