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.