Water Fluoridation Controversy - Safety

Safety

At the dosage recommended for water fluoridation, the only clear adverse effect is dental fluorosis, which can alter the appearance of children's teeth during tooth development. This effect is mildly cosmetic and is unlikely to represent any real effect on public health. Fluoridation has little effect on risk of bone fracture (broken bones); it may result in slightly lower fracture risk than either excessively high levels of fluoridation or no fluoridation. A major Australian study found no clear association between fluoridation and cancer or deaths due to cancer, both for cancer in general and also specifically for bone cancer and osteosarcoma, and other adverse effects lack sufficient evidence to reach a confident conclusion.

The WHO set a general guideline of 1.5 mg/L concentration of fluoride in drinking water to avoid adverse effects of higher concentrations including severe dental fluorosis and skeletal fluorosis, as these effects were minimal at this concentration or lower. In 2006, a 12-person U.S. National Research Council (NRC) committee reviewed the health risks associated with fluoride in the water and unanimously concluded that the maximum contaminant level of 4 mg/L should be lowered. Although it did not comment on water fluoridation's safety, three of the panel members, namely Robert Isaacson, Kathleen Thiessen and Hardy Limeback, expressed their opposition to water fluoridation after the study and the chair, John Doull, suggested that the issue should be reexamined.

Because water fluoridation provided is not individually controlled, opponents express concern for vulnerable populations such as children, nutritionally deficient individuals, and renally impaired individuals. The National Research Council states that children have a higher daily average intake than adults per kg of bodyweight. Those who perspire heavily or have kidney problems consume more water and thus also have a greater intake. A 2006 study found an association between fluoride exposure in drinking water during childhood and the incidence of osteosarcoma among males but not among females. A 2009 analysis by the United States Centers for Disease Control (CDC) stated that upon reviewing this and other similar studies, the weight of the evidence does not support a relationship. However, the CDC also calls for further research into this potential association to help support or refute the observation. A study performed as a doctoral thesis, which is described as the most rigorous yet by the Washington Post, found a relationship among young boys, but then the Harvard professor who advised the doctoral students determined that the results were not highly correlative enough to have evidentiary value; the professor then was investigated but exonerated by the federal government's Office of Research Integrity (ORI).

An epidemiological connection between silicofluorides, an industrial byproduct which is used to fluoridate much of the U.S. water, and lead uptake in children was observed in a 2000 study. A 2006 U.S. CDC-funded study was unable to replicate the results, which the original researchers responded to in a 2007 rebuttal. Aside from the lead connection, concerns are raised as to whether silicofluorides might have different effects on the body than sodium fluorides, and silicofluorides have not been rigorously tested for safety.