Fluoride is the monatomic anion of fluorine, a naturally occurring element usually found as calcium fluoride. It is the 13th-most abundant element on Earth, commonly found in the ocean, groundwater and plants. Because fluoride is a negatively charged ion, it reacts with calcium in the teeth and bones. This reaction is relevant in the current conversation around the use of fluoride.
Community water fluoridation is “the controlled addition of a fluoride compound, usually sodium hexafluorosilicate, to a public water supply to achieve a concentration
optimal for dental caries prevention.”1
Fluoride was shown to be beneficial for reducing dental caries as early as 1931. Grand Rapids, Michigan, became the first city in the world to fluoridate its drinking water on Jan.
25, 1945. Evidence shows that water fluoridation reduces caries by about 25% in children and adults.2, 3, 4 Earlier reports stated that dental caries were reduced by 65%. The
drop in efficacy is due to the fact that there are fewer caries lesions due to sealants, fluoride from dentifrices, greater access to dental care and better emphasis on oral hygiene and diet. Based on systematic reviews of scientific literature, the U.S. Community Preventive Services Task Force issued a strong recommendation in 2001 and again in 2013 for community water fluoridation for the prevention and control of tooth decay.5, 6 Currently, 73% of the U.S. population (240 million) drink fluoridated water.
Fluoride helps prevent dental caries in three ways. Fluoride makes the enamel more resistant to acid by substituting the hydroxyl ion in the enamel matrix with the more
electronegative fluoride ion.
This process can also reverse early carious lesions. Fluoride also works by reducing the ability of bacteria (S. mutans) to produce lactic acid by inhibiting an enolase enzyme.
Finally, fluoride inhibits bacterial growth by glycolysis inhibition.
There are adverse effects of fluoride. The three most cited are dental fluorosis, skeletal fluorosis and cognitive impairment in children. Fluorosis occurs at concentrations above 1.5 mg/l (1.5 ppm), over twice the amount in fluoridated water.7 Skeletal fluorosis typically occurs when fluoride concentrations in drinking water reach significantly elevated
levels, considered to be around 10–20 mg/l, with prolonged exposure over many years being necessary to develop the condition.8 Cognitive impairment has been studied in peer-reviewed scientific literature. Brain development begins in the third gestational week. The developing brain is more susceptible to injury from toxins than the mature brain.
High fluoride exposure might be associated with negative cognitive outcomes in children. However, more longitudinal studies of high methodological quality are needed
on this topic. Negative association between fluoride exposure and cognitive outcomes appears to be stronger at higher levels of fluoride exposure (≥2 mg/l) compared
to lower levels (<2 mg/l). The scientific basis for adverse nondental health outcomes is contradictory and inconclusive.9
There are also concerns with previous literature reviews. Child cognitive development is complex and could be influenced by several physiological and environmental
factors. Poverty, nutritional deficiencies and inadequate learning opportunities are confounding factors. There is also inconsistent reporting of the cognitive outcomes across different studies using various assessment tools and units. None of the included studies considered other factors in cognitive development, such as iodine deficiency, which
represents the greatest single cause of brain damage globally. Iodine deficiency has been associated with a global loss of 10–15 IQ points at a population level.
Investigators from the United States and other countries have reviewed the scientific literature and have not found evidence linking community water fluoridation with
any potential adverse health effect or systemic disorders such as cancer, Down syndrome, heart disease, osteoporosis and bone fracture, immune disorders, low
intelligence, renal disorders, Alzheimer's disease, or allergic reactions.10, 11 It is important to note that fluoride from all sources is cumulative and should be
considered. Along with fluoridated water, we ingest fluoride from toothpaste, plants and food.12
Proponents of water fluoridation see it as a question of public health policy and equate the issue to vaccination and food fortification, citing significant benefits to
dental health with minimal risks. Opponents of water fluoridation view it as an infringement of individual rights, if not an outright violation of medical ethics, on the
basis that individuals have no choice.
In August 2024, the National Toxicology Program released a report stating that drinking water with more than double the recommended limit of fluoride was associated with lower IQ levels in children.13 Following the report's release, several health care organizations spoke out in support of water fluoridation, citing evidence that the U.S. Public Health Service's current recommended level of 0.7 mg/l of fluoride concentration in drinking water is safe and effective at reducing the risk of tooth decay. A federal judge
later ruled in September 2024 that the U.S. Environmental Protection Agency (EPA) must address the impact fluoride has on drinking water. After the ruling, several
dental organizations, including the American Dental Association (ADA), reiterated their support for current fluoride recommendations. Opposition started in the 1940s.
Conspiracy theorists claimed that fluoridation was a communist plot to undermine American public health. Organized political opposition has come from Christian Scientists, environmentalists, libertarians, the John Birch Society, the Ku Klux Klan, and groups like the Green parties in the U.K. and New Zealand.
Robert Kennedy Jr., in October 2024, said President Donald Trump would aim to remove fluoride from public water sources when in office. In a post on X, Kennedy claimed
fluoride is associated with arthritis, bone fractures, bone cancer, IQ loss, neurodevelopmental disorders and thyroid disease, but did not cite any
evidence or studies.14
Despite the lack of credible scientific evidence, there have been recent changes in fluoridation policies. In California, U.S. District Judge Edward Chen ruled that fluoride poses an unreasonable risk to children at the current levels and ordered an EPA review of fluoride.
Florida Surgeon General Joseph Ladapo, MD, PhD, recommended against community water fluoridation due to the potential neuropsychiatric risk associated with fluoride exposure. He also noted the wide availability of existing alternative sources of fluoride, including toothpaste, mouthwash and fluoride applications.
Winter Haven, Florida, voted in October 2024 to remove fluoride from their water system by Jan. 1, 2025. The city of Naples, Florida, followed by voting to discontinue fluoridation in December 2024. Lawmakers in Arkansas filed legislation to repeal a state law requiring fluoride in drinking water.
The ADA has criticized the National Toxicology Program for using unorthodox research methods, flawed analyses, lack of clarity, failure to follow the norms of peer
review and lack of transparency. The report relied on studies that used urinary fluoride to assess exposure despite a scientific consensus that this is not a valid biomarker for long-term fluoride exposure.15 Also, the report’s authors acknowledge the findings were limited to fluoride exposures that are more than double (≥1.5 mg/l) what the Centers for
Disease Control and Prevention (CDC) recommends for community water fluoridation (0.7 mg/l).
The monograph emphasizes that it does not address whether the exposure to fluoride added to drinking water is associated with a measurable effect on IQ, nor does the monograph assess the benefits of the use of fluoride in oral health or provide a risk/benefit analysis. Causality cannot be determined by retrospective analysis of uncontrolled data.
According to the ADA’s expert committee that examined the report in great detail, the monograph does not provide any new or conclusive evidence that should necessitate changes in current community water fluoridation practices for public health policy consideration. None of the studies on IQ included in the organization’s review were conducted in the U.S. and were instead from areas with high levels of naturally occurring fluoride in water. A more detailed review of the National Toxicology Program’s paper by the ADA and American Association of People with Disabilities has been promised.
Even though fluoride has been studied since 1931, science mandates constant review of new evidence. However, science should be separated from science fiction. Meanwhile, one should rely on credible data supporting the assertion that community fluoride programs are safe, efficacious and cost-effective health care measures.
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