The National Toxicology Program (NTP) on Wednesday published a controversial report linking fluoride exposure to neurotoxic effects in children, after public health officials tried for years to block its publication and water down its conclusions.
The report, which analyzed published studies on fluoride’s neurotoxicity, concluded with “moderate confidence” that higher levels of fluoride exposure in drinking water are consistently linked to lower IQs in kids.
It’s the first government publication to concede what fluoride researchers have long reported: that the chemical added to the drinking water of hundreds of millions of people in the U.S. and celebrated as one of the 10 greatest health achievements of the 20th century carries a serious risk of neurological damage, particularly for pregnant women and young children.
“The NTP monograph provides more than sufficient evidence against the deliberate exposure of humans to fluoride through intentional fluoridation of drinking water,” said risk analysis scientist Kathleen Thiessen, Ph.D., who was not involved with the study but co-authored the 2006 National Resource Council study on fluoride toxicity.
Thiessen told The Defender, “A conclusion of ‘moderate confidence’ of neurotoxic effects, especially on unborn and newborn children, ought to mean an immediate elimination of water fluoridation and minimization of fluoride exposure to the population.”
The report reviewed existing studies that assessed the relationship between fluoride exposure and neurodevelopmental effects in children and adults from across the world, including places where fluoride occurs naturally in groundwater and places like the U.S., Canada and Mexico, where it is intentionally added to drinking water or food.
The authors concluded that exposure to drinking water containing more than 1.5 milligrams per liter (mg/L) is consistently associated with lower IQ in children. That’s only twice the amount the Centers for Disease Control and Prevention (CDC) recommends be added to drinking water in the U.S. to prevent tooth decay.
Most environmental toxins regulated by the U.S. Environmental Protection Agency (EPA) are more strictly controlled. Typically, human exposure is banned at 30 times lower than the level of their known toxic effects. None of the chemicals regulated under the Toxic Substances Control Act are permitted at a margin of less than 10.
The researchers found that almost all of the high-quality studies identified — 18 out of 19 — found a link between fluoride exposure and lower IQ in children. And 8 of 9 high-quality studies that looked at neurodevelopmental links other than IQ also found a link.
They said they were less confident that there was a consistent link between low levels of fluoride exposure in water and neurodevelopmental issues, and that more research is needed in that area. However, they also noted that water is not the only source of fluoride exposure.
“Additional exposures to fluoride from other sources would increase total fluoride exposure,” the report stated. “The moderate confidence conclusions may also be relevant to people living in optimally fluoridated areas of the United States depending on the extent of their additional exposures to fluoride from sources other than drinking water.”
Thiessen said pregnant women are often exposed to higher levels of fluoride because they drink much more water than others. And formula-fed infants are also at particularly high risk.
“While fluoridation of drinking water is the main source of fluoride intake for millions of people in the U.S., and probably the easiest to eliminate, it is not the only source of fluoride exposure, with toothpaste and tea probably being next in importance,” she said.
Fluoride advocates like the American Dental Association (ADA), the American Academy of Pediatrics (AAP) and the CDC argue that adding fluoride to water is an important public health practice because it prevents tooth decay by exposing teeth to low levels of fluoride throughout the day and strengthening teeth.
Federal health officials have been recommending water fluoridation for more than five decades. However, in the last several years as the NTP report has moved closer to publication, support for the practice has appeared to wane among some public health officials.
The U.S. surgeon general in 2015 officially lowered the recommended dosage for water fluoridation from 0.7-1.2 mg/L to 0.7 mg/L after considering adverse health effects. And in 2020, out of concern for the forthcoming findings in the NTP report, the U.S. surgeon general’s office declined to make a public statement endorsing the practice.
A spokesperson for the CDC told The Defender in a statement that the agency continues to support water fluoridation at current recommended levels.
“These recommendations are based on current scientific evidence and prioritize the safety, security, and health of all individuals,” the agency said. “Continued research is needed to better understand the health risks and benefits associated with low fluoride exposures.”
The spokesperson also said, “While concerns have been raised about potential risks associated with high fluoride exposure, it is important to note that these concerns are primarily based on studies conducted in countries with higher fluoride exposure than in the United States.”
However, some of the highest quality studies to date have been done in Canada and Mexico, where exposure levels were the same as exposure levels in parts of the U.S. And a paper published in JAMA Network Open in May found that children born to women exposed during pregnancy to fluoridated drinking water in Los Angeles were more likely to have neurobehavioural problems.
The ADA, AAP and EPA did not respond to The Defender’s request for comment.
The long road to publication
For more than two decades, researchers have drawn a link between fluoride exposure and neurodevelopmental issues. In 2006, the National Research Council of the National Academies of Science released a report on fluoride toxicity that identified serious health issues associated with fluoride exposure and called for further research.
The NTP, part of the U.S. Department of Health and Human Services (HHS) responsible for producing scientific research meant to inform policymaking, in 2016 began working on its review of fluoride’s neurotoxicity in humans.
After six years and multiple rounds of peer review, the NTP finalized its report in May 2022 — but public health officials within multiple agencies across HHS blocked its publication, according to emails obtained via a Freedom of Information Act request.
The NTP was compelled to send the report out for another round of peer review. Each round of peer review compelled the NTP to walk back some of its conclusions in what critics called an attempt to “delay it, to water it down.”
Former NTP director Dr. Brian Berridge told The Defender the report received unprecedented scrutiny because of challenges to the report by biased stakeholders. He said he believed it was an outcome of public health agencies’ desires to protect the practices they already have in place.
A draft version of the report was made public in March of 2023 under court order.
The order came as part of a lawsuit filed in 2017 by Food & Water Watch, Fluoride Action Network, Moms Against Fluoridation and other advocacy groups and individuals suing the EPA in a bid to force the agency to prohibit water fluoridation in the U.S. due to fluoride’s toxic effects on children’s developing brains.
After initial hearings in June 2020, presiding Judge Edward Chen placed the trial on hold pending the release of the report. After plaintiffs introduced evidence of agency attempts to suppress the report, Judge Chen ordered its release in draft form and the trial continued in January and February of this year.
The report, along with four major fluoride studies using birth cohorts — where researchers collect epidemiological data during pregnancy and then from children over their lifetimes to study a variety of health outcomes tied to environmental exposures — was key evidence in the trial.
The trial concluded on Feb. 13, and Judge Chen has not yet issued a decision.
The report finalized yesterday consists of one part of the NTP’s research. The other part, a meta-analysis, is forthcoming in a peer-reviewed journal.
NTP Director Rick Woychik said in a statement to The Defender that the delay in the report’s publication was due to an attempt to “get the science right” because “fluoride is such an important topic to the public and to public health officials.”
Woychik emphasized that water fluoridation “has been a successful public health initiative.”
Michael Connett, attorney for the plaintiffs in the case against the EPA, said the final version of the report, “confirms and actually further strengthens the NTP’s prior conclusions,” because the finalized version includes a supplemental review of more recent literature published between 2020 and 2023, which also finds a consistent link between fluoride exposure and adverse neurodevelopmental effects.
Connett added:
“Here you have an expert body of the US government confirming that fluoride is a neurotoxicant. That by itself is a very significant conclusion and should really prompt the question among policymakers and the public as to whether we really want to be adding a neurotoxicant to our water supply while questions remain about the precise doses that caused this effect.”
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‘We didn’t sign up to add a neurotoxicant to our water’
The number of scientists and health professionals opposed to fluoridation has increased over the last several decades. Thiessen said the final publication of the monograph — and the forthcoming meta-analysis — provides important evidence for their position and might signal a change in the status quo public health position on fluoride.
“One hopes that it will help convince many more professionals that one of the 20th century’s top 10 public health achievements has in fact been terribly misguided from the beginning.”
The lawsuit brought public attention to the debate over water fluoridation ongoing among scientists working in public health for years, with many mainstream outlets addressing an issue that had often been disregarded as a conspiracy theory.
Connett said the government report ought to raise public concern and get more people asking questions about fluoridation. He said:
“This isn’t what people signed up for when we started adding fluoride to the water. We didn’t sign up to add a neurotoxicant to our water. We signed up for something that could help our teeth. Now that we know that it can affect our brain, we really need to go back to square one on this.”
Fluoride Action Network board member Rick North told The Defender that awareness about issues with water fluoridation has been growing for years.
“Fluoridation is a house of cards and it’s going to fall. It’s only a matter of when. The NTP report just made it sooner.” He said he hopes the final release of the report means a decision in the case against the EPA will come soon.
“For more than four years, Judge Edward Chen has waited for the final NTP report. Now he’s got it — even more scientific backing that fluoridation is an unreasonable risk to human health,” he said.
Stuart Cooper, Fluoride Action Network executive director, said the publication of the report was historic. “This report, along with the large body of published science, makes it abundantly clear that the question isn’t whether fluoridation is safe, but instead how many children have been needlessly harmed,” he said.
The report sometimes makes contradictory statements, Kim Blokker, a board member of Moms Against Fluoridation, told The Defender, showing the influence of the public health agencies on the reporting. “Do not be fooled by this attempt to muddy the waters of this otherwise definitive report, which contains more than enough evidence to prove the shockingly detrimental effects of fluoride exposure in young children.”
Kristie Lavelle, another board member of Moms Against Fluoridation, told The Defender they were happy to see the report finally published. “The time has come for fluoride to lose its status as a protected pollutant and to be treated the same as other recognized toxins such as lead and arsenic.”
With the publication of the report, she said, “We are one step closer to creating a world where clean water, air and food, and consequently vibrant health are the norm for our children and grandchildren.”
