Ingestion of fluoride has little benefit, but many risks.

Whereas fluoride’s benefits come from topical contact with teeth, its risks to health (which involve many more tissues than the teeth) result from being swallowed.

Adverse effects from fluoride ingestion have been associated with doses attainable by people living in fluoridated areas. For example:

Risk to the brain. According to the National Research Council (NRC), fluoride can damage the brain. Animal studies conducted in the 1990s by EPA scientists found dementia-like effects at the same concentration (1 ppm) used to fluoridate water, while human studies have found adverse effects on IQ at levels as low as 0.9 ppm among children with nutrient deficiencies, and 1.8 ppm among children with adequate nutrient intake. (10-13)

Risk to the thyroid gland. According to the NRC, fluoride is an “endocrine disrupter.” Most notably, the NRC has warned that doses of fluoride (0.01-0.03 mg/kg/day) achievable by drinking fluoridated water, may reduce the function of the thyroid among individuals with low-iodine intake. Reduction of thyroid activity can lead to loss of mental acuity, depression and weight gain (14)

Risk to bones. According to the NRC, fluoride can diminish bone strength and increase the risk for bone fracture. While the NRC was unable to determine what level of fluoride is safe for bones, it noted that the best available information suggests that fracture risk may be increased at levels as low 1.5 ppm, which is only slightly higher than the concentration (0.7-1.2 ppm) added to water for fluoridation. (15)

Risk for bone cancer. Animal and human studies – including a recent study from a team of Harvard scientists – have found a connection between fluoride and a serious form of bone cancer (osteosarcoma) in males under the age of 20. The connection between fluoride and osteosarcoma has been described by the National Toxicology Program as “biologically plausible.” Up to half of adolescents who develop osteosarcoma die within a few years of diagnosis. (16-19)

Risk to kidney patients. People with kidney disease have a heightened susceptibility to fluoride toxicity. The heightened risk stems from an impaired ability to excrete fluoride from the body. As a result, toxic levels of fluoride can accumulate in the bones, intensify the toxicity of aluminum build-up, and cause or exacerbate a painful bone disease known as renal osteodystrophy. (20-23)

Water fluoridation’s benefits to teeth have been exaggerated.

Even proponents of water fluoridation admit that it is not as effective as it was once claimed to be. While proponents still believe in its effectiveness, a growing number of studies strongly question this assessment. (29-54) According to a systematic review published by the Ontario Ministry of Health and Long Term Care, “The magnitude of [fluoridation’s] effect is not large in absolute terms, is often not statistically significant and may not be of clinical significance.” (41) For example:

No difference exists in tooth decay between fluoridated & unfluoridated countries. While water fluoridation is often credited with causing the reduction in tooth decay that has occurred in the US over the past 50 years, the same reductions in tooth decay have occurred in all western countries, most of which have never added fluoride to their water. The vast majority of western Europe has rejected water fluoridation. Yet, according to comprehensive data from the World Health Organization, their tooth decay rates are just as low, and, in fact, often lower than the tooth decay rates in the US. (30, 40, 49)

Cavities do not increase when fluoridation stops. In contrast to earlier findings, five studies published since 2000 have reported no increase in tooth decay in communities which have ended fluoridation. (42-46)

Fluoridation does not prevent oral health crises in low-income areas. While some allege that fluoridation is especially effective for low-income communities, there is very little evidence to support this claim. According to a recent systematic review from the British government, “The evidence about [fluoridation] reducing inequalities in dental health was of poor quality, contradictory and unreliable.” (53) In the United States, severe dental crises are occurring in low-income areas irrespective of whether the community has fluoride added to its water supply. (54) In addition, several studies have confirmed that the incidence of severe tooth decay in children (“baby bottle tooth decay”) is not significantly different in fluoridated vs unfluoridated areas. (32, 37, 47) Thus, despite some emotionally-based claims to the contrary, water fluoridation does not prevent the oral health problems related to poverty and lack of dental-care access.