A study published Monday links exposure to fluoridated tap water during pregnancy to lower IQ scores in infants, but several outside experts expressed concern over its methodology and questioned its findings.
Fluoride has been added to community water supplies in industrial countries to prevent tooth decay since the 1950s.
Very high levels of the mineral have been found to be toxic to the brain, though the concentrations seen in fluoridated tap water are generally deemed safe.
"We realised that there were major questions about the safety of fluoride, especially for pregnant women and young children," Christine Till at Canada's York University, senior author of the paper published in JAMA Pediatrics, told AFP.
"We know that decisions need to be based on evidence, and we had no evidence on whether fluoride in pregnancy was safe, and regardless of the outcome, that knowledge was really critical."
Anticipating controversy, JAMA Pediatrics took the unusual step of issuing an Editor's Note that said the decision to publish the article was "not easy."
"Given the nature of the findings and their potential implications, we subjected it to additional scrutiny for its methods and the presentation of its findings."
"The authors state that an increase of one milligram per liter (1 mg/L) increase in fluoride was associated with a 4.49 point lower IQ score but fluoride intake appears to have been below 1 mg/L for most people in the study, even for those with fluoridated water."
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