PNAS
Fluoridated water not linked to lower IQ, cognition
Clinical takeaway: Community water fluoridation wasn't associated with lower IQ at age 16 or cognitive performance into older adulthood.
Concerns about fluoride and IQ have influenced recent policy decisions in parts of the U.S. This study examined whether those concerns hold up to scientific examination.
In more than 10,000 individuals followed from adolescence into older adulthood, cognitive performance was similar between those exposed to fluoridated water and those who weren't. No meaningful differences were observed at any age tested, from adolescence through age 80.
Community water fluoridation reduces tooth decay and the need for dental treatment at the population level. Most studies linking fluoride to lower IQ involve exposures far above typical U.S. water fluoridation levels, often from regions with naturally high fluoride concentrations (≥1.5–4 mg/L or higher). In contrast, community water fluoridation in the U.S. is maintained at about 0.7 mg/L, a level not shown to be associated with cognitive harm in population-based studies.
“We find no evidence that community water fluoridation is negatively associated with adolescent IQ or adult cognitive functioning,” the authors conclude.
Source: Warren JR. Proc Natl Acad Sci U.S.A. 2026 Apr 13. Municipal water fluoridation, adolescent IQ, and cognition across the life course