National Toxicology Program releases fluoride exposure monograph

ADA reaffirms support for community water fluoridation

The ADA continues to endorse community water fluoridation as safe and beneficial to oral health, following a new report from the National Toxicology Program. 

The National Toxicology Program, part of the Department of Health and Human Services, released its “Monograph on the State of Science Concerning Fluoride Exposure and Neurodevelopment and Cognition,” which found that fluoride in drinking water at more than twice the recommended limit is associated with lower IQ in children. The ADA has reviewed the monograph and continues to stand behind community water fluoridation. 

The long-awaited report, which follows two previous drafts in 2019 and 2020,  summarizes the available literature about a possible relationship between fluoride exposure, neurodevelopmental and cognitive health and IQ. The report’s authors acknowledge the findings are limited to fluoride exposures that are more than double (≥1.5 mg/L) what the 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 benefits of the use of fluorides in oral health or provide a risk/benefit analysis.

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 any 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. 

The report does not provide any evidence to inform the practice of community water fluoridation, according to Scott Tomar, D.M.D., professor and associate dean at the University of Illinois at Chicago College of Dentistry. 

“The bottom line is that the National Toxicology Program report and other recent systematic reviews indicate that the level of fluoride used in community water fluoridation is effective for preventing tooth decay and is not associated with any change in people’s IQ or neurological development,” said Dr. Tomar, who is a member of the National Fluoridation Advisory Committee, the ADA’s standing panel of experts that provide ongoing advice about the safety and effectiveness of fluoride. 

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. 

Last year, National Toxicology Program Director Rick Woychik, Ph.D., convened a scientific review panel to determine whether the organization had resolved the methodological concerns expressed by the report’s original peer reviewer, the National Academies of Sciences, Engineering and Medicine, several federal agencies, the ADA and others. 

Howard Pollick, B.D.S., ADA spokesperson on fluoridation, said the National Toxicology Program did not adequately address concerns from the National Academies of Sciences, Engineering and Medicine in its initial drafts. 

“After the [National Academies of Sciences, Engineering and Medicine] committee reported the first two drafts would not survive scientific scrutiny without major revision, [the National Toxicology Program] abandoned that course of peer review and, instead, hand-picked its own panel to review the draft before you,” Dr. Pollick testified during a May 4, 2023, panel hearing. “[The National Toxicology Program] also has not resolved what [the National Academies of Sciences, Engineering and Medicine] identified as ‘worrisome inconsistencies’ in its risk-of-bias determinations.” 

“That is not consistent with the spirit of a truly independent peer review,” Dr. Pollick added. 

The Board of Scientific Counselors reported nearly 13% of the National Toxicology Program’s responses to comments on the third draft state of the science report, and more than one third, or 35.5%, of the organization’s responses to comments on the meta-analysis, to be inadequate. The panel recommended or suggested revisions to the meta-analysis, based on 57.4% of reviewer comments. 

Meta-analyses are used to reveal the biases, strengths and weaknesses of existing studies. 

“Significant limitations and biases within the report must be considered before accepting its conclusions,” said Jayanth Kumar, D.D.S., MPH former California state dental director and NFAC member. “A major failing is the omission of the meta-analysis, which undermines the report’s robustness.” 

Dr. Kumar added that the National Academies of Sciences, Engineering and Medicine panel previously raised concerns such as inconsistent application of risk of bias criteria, inadequate statistical rigor and selective reporting of non-significant study results, all of which persist in the latest report. 

“The report heavily relies on studies that use spot urinary fluoride to assess exposure despite a scientific consensus that this is not a valid biomarker for long-term fluoride exposure,” he said. 

Two earlier drafts contained a hazard assessment stating fluoride is “presumed to be a cognitive neurodevelopmental hazard to humans,” regardless of exposure level. The hazard assessment was later removed after [the National Academies of Sciences, Engineering and Medicine, the original peer reviewer, reported in its second review, “[T]he monograph falls short of providing a clear and convincing argument that supports its assessment.” 

“As public health professionals, we are committed to the overall health and wellbeing of the public and not just its oral health,” Dr. Tomar said. “We consider overall risks and benefits in making our assessments and recommendations.” 

The Centers for Disease Control and Prevention has hailed community water fluoridation as one of 10 great public health achievements of the 20th century and noted it is an inexpensive way to reduce tooth decay by at least 25% in the population, the ADA notes. 

"It would be a shame to distract from over 75 years of public health success over a simple matter of communicating the science, which is often more nuanced than a sound bite can convey," the ADA said in a statement. 

Follow all the ADA’s advocacy efforts at ADA.org/Advocacy. 

For more information on community water fluoridation and ADA advocacy, visit ADA.org/fluoride.