A rigorous nine-year research review looking at the relationship between fluoride and intelligence in children concludes that as fluoride levels rise, IQ drops.

The results of a new federal analysis were drawn from studies conducted in other countries, where drinking water contains more fluoride than in the United States.

A review of 74 medical studies links higher fluoride exposure to lower IQ in kids — but mostly draws on research that took place outside of the U.S. and had a high risk of biased results. Why it matters: The federally funded analysis could further stoke the debate over adding fluoride to drinking water as Robert F.

The U.S. Toxicology Program just published a study reviewing past research on the safety of fluoride for children. Reporting in JAMA Pediatrics, they found a slight decrease in IQ scores as fluoride blood levels increased.