Children exposed to fluoride in the womb at levels meeting the federal safety threshold scored measurably lower on tests of memory and problem-solving, according to a study of more than 2,500 U.S. children.
The study, published in the American Journal of Epidemiology and funded by the National Institutes of Health, identified that prenatal fluoride levels of 0.675 mg per liter (mg/L) were a change-point in the data.
When mothers’ neighborhood water supply reached around or above this level, each additional increase of 0.5 mg/L was associated with a nearly 3.5-point drop in children’s problem-solving scores.
To give the numbers some context, 0.675 mg is lower than the U.S. Public Health Service’s current recommendation of 0.7 milligrams of fluoride per liter.
The study found the strongest effect in children under age 7.
Declines in Problem Solving
Researchers tracked children born between 2006 and 2019, testing their cognitive abilities between ages 3 and 17. To estimate each child’s fluoride exposure before birth, the team matched fluoride measurements from local water systems to the addresses where mothers lived during pregnancy.
The study found a link between fluoride exposure and fluid cognition: the ability to solve new problems, retain short-term information, and adapt. It did not find a link between fluoride and “crystallized cognition”—skills such as vocabulary and general knowledge that are typically built up through education and experience.