The findings of a new study suggest that children born to mothers who consumed fluoride during pregnancy may face have lower intelligence levels.
Canadian researchers found that side effects of fluoridated water during pregnancy were associated to an overall decrease of more than three points in IQ among young children, though the impact was more pronounced in boys. The findings were published this week in the medical journal JAMA Pediatrics.
Researchers conducted a multi-center birth study using information from the Maternal-Infant Research on Environmental Chemicals cohort. They recruited women during the first 14 weeks of a healthy pregnancy who had children born between 2008 and 2012. This included 600 mother-child pairs from six major cities in Canada.
The mothers provided urine samples during each trimester to measure fluoride levels as well as provided information regarding consumption of fluoridated water and beverages. The children had IQ tests at baseline and again between the ages of three and four. More than 40% lived in communities supplied with fluoridated municipal water.
Women living in areas with fluoridated tap water had significantly higher average levels of maternal urinary fluoride concentrations than women who lived in areas with non-fluoridated water.
High intake of fluoridated water was linked to a lower IQ score in children. A 1-mg/L increase in maternal urinary fluoride levels was associated with a 4.49 lower IQ score in boys.
However, when researchers examined fluoride intake specifically, not urinary levels, high intake was linked to a 3.66 lower IQ score in both boys and girls. Intake compared to urinary levels focuses on consumption of tap water and beverages the mothers drank which is a more accurate measure of exposure.
The amount of fluoridated water women ingested resulting in the lowered IQ scores among the children was the equivalent of 1 liter of fluoridated water per day.
“The findings of the current study are also concordant with ecologic studies that have shown an association between higher levels of fluoride exposure and lower intellectual abilities in children,” the researchers determined. “Collectively, these findings support that fluoride exposure during pregnancy may be associated with neurocognitive deficits.”
The United States began adding fluoride to the public water supply in the 1940s to strengthen teeth and prevent tooth decay. However, since then research has shown conflicting evidence regarding its effect on human health. The World Health Organization concluded it can actually damage teeth in high doses and animal studies have linked it to bone cancer and cognitive impairment.
Roughly 66% of Americans are exposed to fluoridated water. In 2015, the U.S. lowered the recommended safety limit for fluoride in the water supply from 1.2 mg per liter to 0.7 mg per liter. This is the same safety limit Canada follows. This year, the FDA proposed lowering maximum levels of added fluoride to bottled water to match the 0.7 mg per liter national safety level.
More than 300 communities in the U.S. voted to end fluoridation programs over the past 20 years, in part because of studies pointing to health concerns.