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Your Environment. Your Health.

Fluoride Exposure in the Womb May Lower IQ in Children

Christine Till, Ph.D.
York University

A new NIEHS-funded study suggests that fluoride consumption during pregnancy may be linked to lower IQ scores in children. According to the authors, it is the first study to estimate fluoride exposure in a large birth cohort, including communities that receive fluorinated water in line with recommendations to prevent tooth decay.

Examining a large existing prospective cohort of 600 mother-child pairs from six Canadian cities, the team measured fluoride in the urine of women throughout their pregnancies and estimated the fluoride in their water by matching their residence with their city water source. They also used a survey to estimate fluoride consumption from tap water and beverages made with tap water, like coffee and tea.

Women living in areas with fluorinated tap water had significantly higher urine fluoride concentrations compared with women who drank nonfluorinated water. When examining estimated overall fluoride intake during pregnancy, they found that a 1 milligram higher daily estimated intake of fluoride among pregnant women was associated with a 3.66-point lower IQ score in children ages 3 to 4. Based only on urine measurements, a 1 milligram per liter increase in maternal urinary fluoride was associated with a 4.49-point lower IQ score only in boys. There was no significant association between maternal urine measurements and IQ in girls, which indicated potential differences between effects from exposure on boys and girls.

Because lowered IQ was observed at fluoride levels typically found in North American cities, the authors suggested that the study might raise concerns about exposures to fluoride during pregnancy, even among pregnant women exposed to optimally fluorinated water.

Citation: Green R, Lanphear B, Hornung R, Flora D, Martinez-Mier EA, Neufeld R, Ayotte P, Muckle G, Till C. 2019. Association between maternal fluoride exposure during pregnancy and IQ scores in offspring in Canada. JAMA Pediatr 173(10):940–948.

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