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ADA scrutinizes proposed fluoride hazard rating

Expert panel concludes no compelling evidence to ‘presume’ a neurocognitive risk

November 21, 2019

By David Burger

 image of fluoridation icon

Washington — The ADA affirmed its support of the safety of community water fluoridation by sending comments Nov. 19 to National Toxicology Program officials about the draft monograph from the federal agency that postulates that fluoride is “presumed to be a cognitive neurodevelopmental hazard to humans.”

The Association's letter, signed by Dr. Chad P. Gehani, ADA president, and Dr. Kathleen T. O’Loughlin, ADA executive director, was sent the same week as similar letters from the American Academy of Pediatric Dentistry and the Association of State and Territorial Dental Directors. All questioned the validity and methodology of many of the studies included in the review.

The ADA letter questions the preliminary conclusions of the draft monograph, titled Draft Monograph on the Systematic Review of Fluoride Exposure and Neurodevelopmental and Cognitive Health Effects. The ADA National Fluoridation Advisory Committee, a multidisciplinary team composed of experts from dentistry, academia and research, helped to draft the comments.

“Our panel of experts concluded that the available literature is insufficient to establish causation between fluoride exposure as experienced in the United States and neurocognitive development,” wrote Drs. Gehani and O’Loughlin. “It found that the literature generally is either lacking, unreliable, inconclusive, conflicting or subject to widespread interpretation. Given the state of the literature, we ask that you revisit the monograph’s draft hazard rating that fluoride is ‘presumed to be a cognitive neurodevelopmental hazard to humans.’”

The letter also called into question the monograph’s inclusion of studies that used higher-level exposures (above 1.5 parts per million). “It is also critical to the public’s health that you include some type of modifier to distinguish the health benefits of optimally fluoridated drinking water, currently recommended at 0.7 parts per million (ppm), from the higher level exposures the monograph addresses,” wrote Drs. Gehani and O’Loughlin.

The National Toxicology Program, run by the National Institutes of Health, conducted a systematic review to evaluate the evidence that exposure to fluoride could be associated with neurodevelopmental or cognitive effects. The National Academies of Sciences, Engineering, and Medicine assembled a committee to review the monograph before a final draft is published in 2020. The committee will provide a critique of the draft monograph if the scientific evidence in the monograph supports the National Toxicology Program’s hazard category conclusions for fluoride in children and adults. Additional information on the review process can be found on the NASEM project information website.

The ADA letter was accompanied by “Fluoridation Facts,” an Association-published reference on the latest evidence-based information on water fluoridation, as well as comments from the National Fluoridation Advisory Committee, which provided a specific analysis of the monograph.

The committee summarized its technical concerns in the document that accompanied the letter:

• The literature review failed to account for the lack of support for a neurobehavioral effect of fluoride in the U.S.
• Lack of meta-analysis to determine a summary effect size. (Effect size quantifies the difference between two groups.) It appears that the determination that the IQ effect size was large is based on subjective assessment and did not account for measurement error.
• The characterization that effect sizes observed were of relatively large magnitude was inconsistent with the data demonstrating small effect sizes, leading to the mischaracterization of fluoride as a “presumed” neurotoxin.
• The monograph’s assertion that “there is a low expectation that new studies would change the hazard conclusion” is not adequately justified considering that there are no prospective epidemiological studies that were designed to assess the neurobehavioral effects of fluoride.

The committee concluded, “The ADA is truly gratified when, in the interest of the public’s health and welfare, communities provide optimally fluoridated water to their residents. The current classification is misleading to the public, could scare them unnecessarily and could ultimately decrease the oral health status of individuals and communities."

“Fluoridation Facts” is among a number of free ADA resources on community water fluoridation, which the ADA has supported since 1950, according to the publication. Other resources are located online at ADA.org/fluoride.