A new Columbia University–led study found that pregnant women who lived in areas with fluoride levels near or above the current levels recommended by the US CDC were more likely to have children who scored lower on problem-solving tests.
Columbia University researchers have published a study detailing how the children of mothers exposed to fluoridated tap water during pregnancy were more likely to score lower on problem-solving tests. Those tap-water levels were within the range currently allowed by the US government.
“These findings suggest that at concentrations below both the current World Health Organization guideline (1.5 mg/L) and the current US Environmental Protection Agency Maximum Contaminant Level (4.0 mg/L), prenatal public water fluoride exposure is inversely associated with child fluid cognition in the US,” the researchers wrote.
They also note that when this new data is considered together with the conclusions of the US National Toxicology Program report from 2024, a “downward revision” of the EPA’s legal limit “may be warranted.”
“These results highlight the need to re-evaluate the current USEPA MCL for fluoride in public water systems (4.0 mg/L), which may not adequately protect neurodevelopment.”
“Because our study used fluoride measurements from public water systems that are collected as part of routine drinking water monitoring, the findings may help inform future evaluations of public drinking water guidelines,” said co-senior author Anne Nigra, PhD, also of Columbia Mailman School.
The study was published in the American Journal of Epidemiology. The researchers used data from the National Institutes of Health’s Environmental influences on Child Health Outcomes (ECHO) Program.
Lower Cognition Scores at Currently Recommended Levels of Fluoride
The study examined 2,514 children born between 2006 and 2019 who completed cognitive testing between ages 3 and 17. The researchers compared publicly available drinking water fluoride measurements to residents’ addresses collected during pregnancy from participants in the ECHO program. While the study focused on fluoride levels in public drinking water, it did not account for total fluoride exposure from all sources. Fluoride is commonly found in toothpastes, tea, supplements, canned foods, bottled water, and private wells.
The researchers then compared the estimated fluoride intake with the children’s performance on NIH Toolbox cognition tests. The study did account for variables such as parental education, parental age, prenatal tobacco exposure, child sex, season of conception, and neighborhood characteristics.
The children whose mothers experienced higher fluoride exposure from public water during pregnancy tended to score lower on tests involving problem-solving, memory, attention, and the ability to adapt to new information.
The study found that lower fluid cognition scores were linked to water fluoride levels near and above 675 micrograms per liter. The US Public Health Service currently recommends a level of 700 micrograms, or 0.7 milligrams, per liter for fluoridated water. The research shows that above 675 micrograms per liter, every 500-microgram-per-liter increase was associated with an average 3.36-point lower score on cognition tests.
“This study adds to a large body of work that looks at how early exposure to environmental contaminants may be associated with the development of the thinking and learning processes that are important for children’s developmental outcomes,” said co-senior author Amy Margolis, PhD, of The Ohio State University Wexner Medical Center and College of Medicine. “Continuing to study fluoride and other exposures will be integral in best supporting children’s environmental health and well-being.”
The Latest Study Pointing to Harm from Water Fluoridation
In addition to the 2024 NTP monograph and this latest study from the Columbia University researchers, there have been numerous studies in the last few years alone that have highlighted the association between prenatal fluoride exposure and lower IQ and neurobehavioral problems in children.
In May 2024, The Last American Vagabond reported on a study published in the JAMA Network Open medical journal titled, Maternal Urinary Fluoride and Child Neurobehavior at Age 36 Months. The researchers studied the maternal urinary fluoride (MUF) levels of 229 Hispanic pregnant women living in Los Angeles, California. They looked for associations between third-trimester MUF and the children’s neurobehavior at 3 years of age. They found that “prenatal fluoride exposure may increase risk of neurobehavioral problems among children.”
“These findings suggest that there may be a need to establish recommendations for limiting exposure to fluoride from all sources during the prenatal period, a time when the developing brain is known to be especially vulnerable to injury from environmental insults,” the study states (emphasis added).
There is also the May 2023 review of the evidence on the potential human health effects of fluoride conducted by Risk Sciences International under a contract with Health Canada, the federal public health agency for Canada.
The RSI report concluded, “the evidence supports a conclusion that fluoride exposure reduces IQ levels in children at concentrations close to those seen in North American drinking water.” The report did acknowledge there is uncertainty about the exact concentration at which harm begins.
Finally, we have the mountains of evidence that were presented during the first and second phases of the historic fluoride lawsuit.
As part of that lawsuit, a federal judge ruled in September 2024 that water fluoridation “poses an unreasonable risk of reduced IQ in children.” However, in May 2026, a federal appeals court overturned that ruling, sending the case back to Judge Edward Chen. The appeals court ruled in favor of arguments put forth by the US EPA, namely that the district court had “abused its discretion when it refused to rule on the first trial record” from summer 2020.
The new ruling came nearly a decade after plaintiffs first filed a citizen petition under the Toxic Substances Control Act (TSCA) in November 2016. The EPA denied the petition, and the groups sued, leading to a decade-long legal saga between the EPA, parents of children impacted by water fluoridation, the Fluoride Action Network (FAN), and Food & Water Watch (FWW).
In his last days in office, former President Joe Biden’s EPA appealed the federal ruling. Upon returning to the White House, President Donald Trump continued the appeal of the historic ruling on water fluoridation.
