By Agence France-Presse
A study published Monday linked consumption of fluoridated tap water during pregnancy to lower IQ scores in infants, a finding at odds with decades of public health messaging extolling the mineral’s benefits in reducing cavities.
Several outside experts expressed concern over the research’s methodology and questioned its conclusions, though some found the results compelling enough to merit further investigation.
The US Centers for Disease Control and Prevention (CDC) named community water fluoridation one of ten great public health achievements of the 20th century because of its contribution to the steep decline in tooth cavities in the United States over several decades.
But although high levels of fluoride have been found to be toxic to rat brains, the concentrations seen in fluoridated tap water are deemed safe.
“We realized that there were major questions about the safety of fluoride, especially for pregnant women and young children,” Christine Till, an associate professor at Canada’s York University and the paper’s senior author told AFP, adding it was important to base decisions on evidence.
The study, published in the influential JAMA Pediatrics journal, analyzed data from 512 mother-child pairs across six Canadian cities, with about 40 percent living in communities supplied with fluoridated municipal water.
After controlling for other toxins in their analysis, they found that an increase in the concentration of fluoride in pregnant mother’s urine of one milligram per liter was associated with a 4.5-point lower IQ score in boys — but not girls — at age three or four.
When estimating the daily maternal fluoride intake instead of fluoride in urine, they found a one milligram increase in intake was associated with a deficit of 3.7 IQ points for both boys and girls.
US and Canadian health authorities recommend capping fluoride concentration at 0.7 milligrams per liter (parts per million) to prevent fluorosis, overexposure to fluoride that leads to mild tooth discoloration.
But the actual levels that will be ingested will vary according to how much a person drinks.
According to the CDC, fluoridated water is supplied to nearly three in four Americans (more than 211 million people), while Health Canada estimates 39 percent of its population receives water from fluoridated supplies.