During President Donald Trump’s televised Cabinet meeting on April 10, Department of Health and Human Services (HHS) Secretary Robert F. Kennedy said that scientific research indicates that exposure to fluoride, a common mineral that helps prevent tooth decay, is associated with IQ loss in children.
“We are working at HHS to advance your agenda to make America healthy again,” Kennedy told Trump at the meeting. “I’m working with [Environmental Protection Agency Administrator] Lee Zeldin on—to reassess the fluoride rules based upon the August release by the National Toxicity Program of new science that shows a direct inverse correlation between exposure to fluoride and IQ loss, particularly in children.”
Two days earlier, Kennedy made similar comments while speaking in Utah, which earlier this month became the first U.S. state to ban supplemental fluoride from water supplies. “Fluoride should not be in our water,” Kennedy said, adding that fluoride levels added to toothpaste and mouthwash are sufficient. “The evidence against fluoride is overwhelming. In animals, in animal models, and in human models we know that it causes IQ loss, profound IQ loss. And it’s dose-related,” he added. “So, the more fluoride you get, the higher levels in your drinking water, your urine, the more likely it is you’ll lose IQ.”
Fluoride is not a substitute for brushing one’s teeth—the minerals help defend the enamel from acids, but do not neutralize them—but has been found to prevent cavities and other dental-related woes. According to 2020 data from the Centers for Disease Control and Prevention (CDC), 62.9 percent of Americans receive fluoridated water from their primary water source, either naturally present in the water or added into local water systems. Researchers in the early 20th century discovered that the level of naturally occurring fluoride in water sources affected the tooth development of nearby populations. While high exposure to fluoride could cause teeth discoloration, exposure to fluoride at lower levels of concentration were found to be effective at limiting tooth decay. Grand Rapids, Michigan—which has very low levels of natural fluoride in its water sources—in 1945 became the first city to add fluoride to its water system, and the practice quickly spread nationwide.
Contrary to Kennedy’s claim, there is no conclusive research showing that fluoride exposure causes IQ loss, and the fluoride concentration levels present in local U.S. water supplies—which both the CDC and Environmental Protection Agency (EPA) monitor—are not considered dangerous or harmful. Kennedy premises his claim on an August 2024 report from the HHS’ National Toxicology Program (NTP)—not “toxicity,” as Kennedy mistakenly said in the Cabinet meeting—which found with “moderate confidence” that fluoride concentration in water above 1.5 milligrams per liter is associated with lower IQ in children. For reference, the CDC recommends a fluoride concentration of 0.7 mg/L, which the agency said is “equal to 3 drops of water in a 55-gallon barrel.” As of April 2020, the report states, only 0.59 percent of Americans live in areas where the fluoride concentration in the local water supply exceeds 1.5 mg/L. The report states outright that it does “not address whether the sole exposure to fluoride added to drinking water in some countries (i.e., fluoridation, at 0.7 mg/L in the United States and Canada) is associated with a measurable effect on IQ.”
The NTP report, which took eight years to complete, reviewed previously published studies that examined fluoride’s relation to IQ. None of those studies examined American subjects or U.S. water sources, but instead collected data from Canada, China, India, Iran, Pakistan, and Mexico. NTP researchers found that 18 of the 19 research studies they examined showed a negative correlation between fluoride exposure and IQ levels in children. In areas where the fluoride concentration in water was at or exceeded 1.5 mg/L, children tended to have a lower average IQ than in regions where the concentration fell below 1.5 mg/L. But that’s not necessarily evidence that the higher fluoride amounts are causing IQ loss.
“There’s no proof that the water systems in the United States lead to an IQ problem,” said Dr. Margherita Fontana, a professor at the University of Michigan’s School of Dentistry, adding that the NTP report’s conclusion can be misleading in a few ways. Perhaps most glaring is that many of the water sources sampled in studies that the NTP report examined are “not considered even safe for drinking because of many other contaminants,” Fontana told The Dispatch Fact Check. While IQ loss is associated with higher fluoride-concentration water, it’s not evident that fluoride exposure is the driving factor—it very well could be water contamination. Indeed, Fontana explains that the data studied is sourced from “places where, if you would travel, you would never drink the water.” The sources “would have many, many other things in the water that would be of concern,” she added.
Another issue is that most of the studies cited in the NTP report estimated fluoride exposure through urine samples of pregnant mothers and children. “Urinary fluoride is thought to reflect recent exposure but can be influenced by the timing of exposure,” the report states. However, the report’s authors said that because the studies it examined had adjusted for the timing of exposure and so the data is “generally considered” to have a low-risk of being substantially inaccurate. Fontana, on the other hand, is more skeptical of urinary fluoride’s accuracy. “There’s no consensus that that is a good measurement of [fluoride] exposure,” she said. For example, a study published in March 2024 determined that research on fluoride’s association with IQ loss, and use of urinary fluoride to measure exposure, “should be considered unacceptable for legal and policy purposes.” It added that “other water fluoridation studies and systematic reviews show no effect of fluoridation on cognition.
Moreover, while Kennedy claimed that evidence of fluoride’s harmful effects are well-documented in animal model studies, the same NTP report reached the opposite conclusion. “In early drafts, it was apparent that the animal data were of poor quality and that the human data were most informative and would be the basis of the confidence conclusions,” the report states. “Therefore, findings from the animal evidence stream were determined to be inadequate and were removed from further drafts.”
It’s true that significantly high fluoride concentration can have negative effects on human health, but not to the degree that Kennedy describes. The maximum concentration of fluoridated water that the EPA allows is 4 mg/L and, in areas where it is above 2 mg/L, water suppliers are required to notify local residents. If a local water system measures fluoride concentration at above 4.0 mg/L, and does not act to lower the concentration under the legal limit, the EPA could bring litigation on those grounds. But even those higher levels don’t correlate to IQ loss. “No one has been able to prove that drinking too much fluoride does anything to your neurological development,” Fontana explained. “The only concern [of fluoride exposure] that I have, that is biologically proven, of drinking too much fluoride is dental fluorosis, which is a cosmetic tooth problem. It is nothing more.”
Fluorosis can cause teeth to become discolored in spots. In fact, although you may not know it, “you probably have fluorosis,” Fontana said. “Most people in the U.S.—most people around the world—have some level of fluorosis, because most water is fluoridated naturally at some level.” Fontana added that fluorosis is generally not a concern outside of the discoloration. In extreme cases, it can cause holes to appear in one’s teeth, but that is not a big problem in the U.S. “We have very, very few water sources that are naturally fluoridated at that level,” Fontana explained. “But they do happen occasionally, which is why the EPA put that upper limit, saying, ‘Listen, if you have more than 4 mg/L, you probably want to remove fluoride from this water source because of fluorosis being a problem.’”
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