A newly released US government report marks the first time a federal agency has confirmed, “with moderate confidence,” that fluoride levels above 1.5 milligrams per litre—twice the recommended limit—are consistently associated with lower IQ in children.
The 324-page National Toxicology Program’s analysis report reviewed studies from multiple countries. It concluded that while fluoride strengthens teeth, excessive exposure poses potential neurological risks.
Ashley Malin, a researcher at the University of Florida, described the report as “crucial in our understanding” of fluoride’s impact on brain development.
The report notes that nearly 2 million Americans are exposed to fluoride levels at or above the threshold linked to reduced IQ.
Despite this, the study did not determine how many IQ points might be lost at different exposure levels, calling for further research.
The American Dental Association, which has historically supported water fluoridation, is currently reviewing the findings.