“On the basis of information largely derived from histological, chemical, and molecular studies, it is apparent that fluorides have the ability to interfere with the functions of the brain and the body by direct and indirect means.”

Fluoride in Drinking Water: A Scientific Review of EPA’s Standards
US National Research Council, National Academy of Sciences, 2006

In 2006, the National Research Council (NRC) published an extensive review of the recent scientific literature on fluoride toxicology. The review had been conducted by a panel of twelve scientists and dentists over three years. The panel concluded unanimously that the upper limit of 4 ppm of fluoride in drinking water, established by the Environmental Protection Agency (EPA) in 1986, is not protective against adverse health effects, and likely to increase the risk of bone fracture. The panel did not determine a new upper limit, recommending that the EPA re-conduct a risk assessment for this purpose. To date, the EPA has not carried out this assessment. Therefore, the level of fluoride in water which would be safe for long-term human consumption is presently unknown.

The NRC review analysed evidence of a wide range of toxicological effects. Fluoride was found to interfere with neurological, endocrine and immune function, and synergise with other ions such as aluminium to exert disruptive effects in cells. Throughout the review, the authors expressed concern at how little is known about fluoride’s effects on the body, despite the clear evidence that fluoride interferes with basic biochemical processes and multiple body systems. Every chapter concluded with urgent recommendations for further research.

See comments from panel members regarding the relevance of this review to water fluoridation.


Fluoride’s effects on the thyroid gland

“Several lines of information indicate an effect of fluoride exposure on thyroid function.”

“Fluoride exposure in humans is associated with elevated TSH concentrations, increased goiter prevalence, and altered T4 and T3 concentrations; similar effects on T4 and T3 are reported in experimental animals…”

“…it is difficult to predict exactly what effects on thyroid function are likely at what concentration of fluoride exposure and under what circumstances.”

“In humans, effects on thyroid function were associated with fluoride exposures of 0.05-0.13 mg/kg/day when iodine intake was adequate and 0.01-0.03 mg/kg/day when iodine intake was inadequate.”

Implications: Applying the standard safety factor of 10 (to account for variation in sensitivity in the population), the maximum safe intake of fluoride would be 0.3 mg for a 60 kg adult. Most people already receive this amount from dietary sources before drinking fluoridated water. A10 kg iodine-deficient infant’s thyroid function could be detrimentally affected by a daily fluoride intake as low as 0.1 to 0.3 mg per day.

The “optimum” level of fluoride in artificially fluoridated municipal water is 1 mg/L; this could be adversely affecting the thyroid function of many individuals, including those who drink large amounts of water relative to their body weight (eg. infants, diabetics, athletes) and those with borderline iodine deficiency.

Fluoride’s effects on the brain

“On the basis of information largely derived from histological, chemical, and molecular studies, it is apparent that fluorides have the ability to interfere with the functions of the brain and the body by direct and indirect means.”

“A few epidemiologic studies of Chinese populations have reported IQ deficits in children exposed to fluoride at 2.5 to 4 mg/L in drinking water. Although the studies lacked sufficient detail for the committee to fully assess their quality and relevance to U.S. populations, the consistency of the results appears significant enough to warrant additional research on the effects of fluoride on intelligence.”

“Studies of populations exposed to different concentrations of fluoride should be undertaken to evaluate neurochemical changes that may be associated with dementia. Consideration should be given to assessing effects from chronic exposure, effects that might be delayed or occur late-in-life, and individual susceptibility.”

Fluoride’s effects on insulin secretion/diabetes

“The conclusion from the available studies is that sufficient fluoride exposure appears to bring about increases in blood glucose or impaired glucose tolerance in some individuals and to increase the severity of some types of diabetes. In general, impaired glucose metabolism appears to be associated with serum or plasma fluoride concentrations of about 0.1 mg/L or greater in both animals and humans. In addition, diabetic individuals will often have higher than normal water intake, and consequently, will have higher than normal fluoride intake for a given concentration of fluoride in drinking water. An estimated 16-20 million people in the U.S. have diabetes mellitus; therefore, any role of fluoride exposure in the development of impaired glucose metabolism or diabetes is potentially significant.” (emphasis added)

Fluoride and cancer

“Fluoride appears to have the potential to initiate or promote cancers, particularly of the bone, but the evidence to date is tentative and mixed (Tables 10-4 and 10-5). As noted above, osteosarcoma is of particular concern as a potential effect of fluoride because of (1) fluoride deposition in bone, (2) the mitogenic effect of fluoride on bone cells, (3) animal results described above, and (4) pre-1993 publication of some positive, as well as negative, epidemiologic reports on associations of fluoride exposure with osteosarcoma risk.”

“Because fluoride stimulates osteoblast proliferation, there is a theoretical risk that it might induce a malignant change in the expanding cell population. This has raised concerns that fluoride exposure might be an independent risk factor for new osteosarcomas.”

“Osteosarcoma presents the greatest a priori plausibility as a potential cancer target site because of fluoride’s deposition in bone, the NTP animal study findings of borderline increased osteosarcomas in male rats, and the known mitogenic effect of fluoride on bone cells in culture (see Chapter 5). Principles of cell biology indicate that stimuli for rapid cell division increase the risks for some of the dividing cells to become malignant, either by inducing random transforming events or by unmasking malignant cells that previously were in nondividing states.”