Toxic Exposures
Fluoride Proponents Claim New Study Bolsters Safety Claims — Critics Say the Study Doesn’t Hold Water
Media outlets, including Scientific American and CNN, on Wednesday published articles promoting a new study concluding that fluoride added to drinking water has no negative effects on cognition and “may actually provide benefit.” Critics called the study’s limitations “substantial.”
Several major media outlets — including Scientific American and CNN — on Wednesday published articles promoting a new study concluding that fluoride added to drinking water has no negative effects on cognition and “may actually provide benefit.”
In what Sayer Ji called a “fluoride disinformation blitz,” the articles framed the research as countering “claims” by U.S. Health Secretary Robert F. Kennedy Jr. that adding fluoride to drinking water is linked to IQ loss.
“The timing reveals a defensive counter-narrative,” Ji wrote, in response to major developments, beginning last year, in water fluoridation science and policy.
In September 2024, a landmark federal court decision that reviewed the science on water fluoridation ruled that current levels of fluoride added to drinking water — 0.7 milligrams/liter (mg/L) — pose an “unreasonable risk” to children’s health. The court ordered the U.S. Environmental Protection Agency (EPA) to take action to address the issue.
Since then, dozens of communities and two states have ended water fluoridation, Kennedy called for the Centers for Disease Control and Prevention to stop endorsing the practice, and the EPA agreed to review fluoride safety — even though the agency has not dropped its appeal of the ruling.
The public has shown growing concerns about water fluoridation, as more scientific evidence from top government research programs, including the National Toxicology Program, and scientists have published a series of gold-standard studies in top journals that reveal evidence linking fluoridation and reduced IQ and other neurotoxic effects.
While many of those studies go unreported in mainstream media, studies that counter those claims, including the study published Wednesday in Science Advances by sociologist John Robert Warren, Ph.D., and colleagues, continue to make headlines.
Part of the coordinated media attack may be linked to the Science Media Centre in London, which earlier this week circulated an email, shared with The Defender, urging coverage of the forthcoming study and offering to connect journalists with experts to comment on it.
The Science Media Centre is a nonprofit public relations agency partially funded by corporations and industry groups whose products the group often defends, according to U.S. Right to Know.
Current and past funders include BASF, Bayer, DuPont, Monsanto, Coca-Cola, Nestle, and food, chemical and nuclear industry trade organizations, as well as media groups, government agencies, foundations and universities.
Meanwhile, scientists concerned with fluoride’s potential neurotoxic effects continue to engage in substantive research and debate on the topic.
Dr. Bruce Lanphear, professor of Health Sciences at Simon Fraser University in British Columbia, and an expert adviser to the EPA on regulating environmental toxins who testified in the fluoride trial. He told The Defender it’s time for the data on fluoride’s risks to be assessed as a whole.
Lanphear said:
“Warren’s new study is an innovative use of an existing cohort, but its measure of fluoride exposure — based solely on the community’s fluoridation status when children were older — is weak. At this point, we need more than piecemeal reactions to individual studies.
“It is time to convene a National Academy committee to systematically evaluate the full body of evidence on fluoride’s benefits and potential neurotoxicity. The uncertainties raised by recent findings deserve a careful, comprehensive assessment — not selective interpretation or the assumption that each new study overturns everything that came before.”
Study’s limitations are ‘substantial’ and undermine the strength of its conclusions
The Science Advances study was designed to assess the association between fluoride exposure in drinking water and cognitive outcomes in adolescence and later adulthood, using data from the “High School and Beyond” cohort, which tracked over 26,000 Americans from adolescence in 1980 through mid-life in 2021.
The authors of the new study estimated fluoride exposure based on where people lived and correlated it to standardized test scores and cognitive tests at age 60. They found that people who grew up in areas with fluoridated water had slightly higher test scores in high school and that by age 60, there was no difference in cognitive performance.
They concluded that fluoridation has no effect on cognition and may help cognition by preventing dental issues.
Experts, including Dr. Hardy Limeback, Kathleen Thiessen, Ph.D., Christopher Neurath, Paul Connett, Ph.D., and others who spoke with The Defender, said the Science Advances study has “substantial limitations” that undermine the strength of its conclusions.
They all noted that it has no measures of individual exposure, so there is no way to tell how much fluoridated water people were exposed to.
Christine Till, Ph.D., a neuropsychologist at York University in Canada, whose groundbreaking research on the MIREC cohort in Canada, published in JAMA Pediatrics, linked maternal fluoride exposure to lowered IQ in children, told The Defender, “The most serious concern is the ecological design.”
She explained:
“Participants are classified simply by whether they were exposed to fluoridated drinking water throughout childhood, for part of childhood, or not at all. This is a crude categorization that fails to consider whether individuals actually consumed tap water versus bottled water, or the specific fluoride concentrations within each group.
“Water fluoride levels alone do not reflect an individual’s actual dose (i.e., intake from all sources) or the timing of exposure. Critically, the study provides no information on fluoride exposure in gestation and infancy.”
Neurath and Thiessen noted the study doesn’t account for population mobility — it assumes people grew up where their later intellectual data was collected. Thiessen said the study also didn’t account for the fact that many schools, even in non-fluoridated areas, had fluoridated water in the past.
Neurath also noted that the outcome measures were not IQ, as they have been in many studies examining fluoride’s neurological effects.
Till said the analyses do not adjust for parental education, which is strongly linked to academic performance and could confound the results.
“The authors’ claim of ‘strong evidence’ for cognitive benefits from fluoride exposure at community water fluoridation levels is markedly overstated. The study evaluates academic outcomes, such as reading comprehension and math performance, which are not equivalent to measures of intelligence and cannot counter the extensive literature documenting associations between early-life fluoride exposure and lower IQ in children.”
Articles omit key studies from their literature review
Experts said both the study and the accompanying editorial inaccurately and selectively summarize the substantive body of rigorous research published in top journals linking fetal and child fluoride exposure to neurological harm.
They also left out major recent studies showing that ingesting fluoride has little to no effect on dental health.
“The introduction to this ‘scientific paper’ reads like a press release from the American Dental Association, littered with exaggerated statements about fluoridation’s benefits and misleading dismissals of the research indicating harm,” attorney Michael Connett, who represented the plaintiffs in the fluoride trial, said.
Both articles claim that data on fluoride’s harm have typically been gathered from outside of the U.S. and demonstrated neurotoxic effects only at levels higher than those at which water is fluoridated in the U.S.
According to Ashley Malin, Ph.D., this assessment is incorrect. All studies conducted in North America “show that prenatal fluoride exposure, even at relatively low levels, is associated with worse child cognitive development, including lower IQ, more symptoms of ADHD and worse executive functioning,” she said.
“Furthermore, there are clear neurophysiological pathways by which these potential adverse impacts can occur,” she added.
Malin, who recently led the first U.S.-based study to find that typical
fluoride exposure levels during prenatal development are associated with
more childhood neurobehavioral problems at age 3, said she was
surprised to see that her study, published in May 2024 in JAMA Network Open, wasn’t included in the literature review.
The authors also heavily relied on a recent review by California’s dental director, Dr. Jayanth V. Kumar, which was also found to have intentionally omitted data.
Obscuring a larger debate
David A. Savitz, Ph.D, a Brown University epidemiologist with no experience researching fluoride and who was paid $137,000 as a litigation expert for the EPA in the fluoride trial, wrote an editorial that accompanied the study.
Savitz attacked fluoride critics as conspiracy theorists. He also argued that the approach to water fluoridation policy should be “If it ain’t broke, don’t fix it,” claiming that the Science Advances paper added credence to the claim that water fluoridation policy, “ain’t broke.”
According to Savitz, there must be compelling evidence of harm at current levels of water fluoridation to change the policy. Savitz, Warren and others argue that compelling evidence of harm is only certain at 1.5 milligrams per liter — twice the current levels of U.S. water fluoridation.
Connett said that position is “his prerogative, but that’s certainly not the standard that EPA brings to bear. EPA does not require compelling evidence of harm at the level of human exposure as the standard for determining risk.”
He said the plaintiffs filed their lawsuit under the Toxic Substances Control Act precisely to demand that the government use — “not the Savitz standard” — but “the same standard that our government uses to protect us from other toxic chemicals.”
Savitz and the rest of the public health community want fluoride to “meet a higher standard of proof than the standards used for other chemicals.”
According to the EPA’s own materials, the agency must determine whether a chemical poses a hazard and at what level, and assess how people are exposed to that hazard. It also has to examine the margin between the hazard level and the exposure level.
That margin of uncertainty — the gap between the level at which a chemical can harm human health and the level at which people can be exposed to it — has to be large enough to account for any scientific unknowns, and to protect the most vulnerable populations who may have greater vulnerability than others.
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The EPA typically requires a margin of 30 times to determine whether a substance poses a risk. The 1.5 mg/L level suggested by Savitz as the known toxic level is only two times the amount of fluoride added to water — and doesn’t account for the many other ways people are exposed to fluoride.
Thiessen, a co-author of the 2006 National Resource Council study on fluoride’s risk, said most studies for toxic effects — including lead, for example — measure toxic effects at levels above typical population exposure levels — but that doesn’t mean there is no toxic effect at the minimum exposure level.
“It is broke, whether or not Savitz wishes to admit it,” Thiessen said. “There is little to no benefit on a population level or for the disadvantaged in the population, and there is increasing evidence of harms.”
Malin pointed out that substantial research in addition to her own links prenatal or infant fluoride exposures below 1.5 mg/L to worse child cognitive development. “If the hazard to child IQ exists at levels below 1.5 mg/L, then there really would be no safe level of fluoride exposure for the developing brain.”
Related articles in The Defender
- EPA Paid Expert Witness $137,000 to Testify in Landmark Fluoride Trial
- Children Whose Mothers Were Exposed During Pregnancy to Fluoridated Tap Water at Higher Risk of Neurobehavioral Problems
- Breaking: New Cochrane Review Finds Water Fluoridation Has Minimal Effect on Dental Health
- Breaking: Fluoride in Water Poses ‘Unreasonable Risk’ to Children, Federal Judge Rules
- EPA to Review Health Risks of Water Fluoridation as RFK Jr. Says He’ll Tell CDC to Stop Recommending It
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