Fluoride exposure in utero linked to lower IQ in kids, study says

About 75% of Americans are exposed to fluoride through public water, but Mexico does not have a fluoridation program.

Story highlights

  • Study finds drop in scores on intelligence tests with increased in utero fluoride exposure
  • It is the largest and longest study to evaluate role of fluoride in developing brain, researcher says

(CNN)Increased levels of prenatal fluoride exposure may be associated with lower cognitive function in children, a new study says.

The study, published Tuesday in the journal Environmental Health Perspectives, evaluated nearly 300 sets of mothers and children in Mexico and tested the children twice for cognitive development over the course of 12 years. Fluoride is not added to public water supplies in Mexico, but people are exposed through naturally occurring fluoride in water and fluoridated salt and supplements.
    The study found a drop in scores on intelligence tests for every 0.5 milligram-per-liter increase in fluoride exposure beyond 0.8 milligrams per liter found in urine. However, although the researchers found a potential connection to a child's exposure to fluoride in utero, they found no significant influence from fluoride exposure on brain development once a child was born.
    "Childhood exposure to fluoride is safer than prenatal. There is pretty good science now to support the fact that the fetal system tends to be more sensitive to environmental toxicants than once the child is born," said the study's lead author, Howard Hu, founding dean of the Dalla Lana School of Public Health at the University of Toronto.
    The authors measured fluoride exposure for the Mexican mothers and their children by looking at the chemical content in their urine. "Since we're using an integrated biological marker, it will give you a fairly standardized measure," Hu explained. Previous studies measured fluoride exposure by analyzing it in the environment, such as in water.