On September 19, Environmental Health Perspectives, a highly-respected journal, published a study linking higher fluoride levels in pregnant women to lower IQ’s in their children.

The decrease was significant. Each 0.5 part per million (ppm) increase in a pregnant woman’s urine fluoride levels reduced her child’s IQ by 2.5 – 3 points. A child of a mother drinking 1 ppm of fluoridated water, close to the U.S standard of 0.7 ppm, would be expected to have a drop of 5 to 6 IQ points compared to a child of a mother drinking water with close to no fluoride in it.

This prospective study was funded by the U.S. National Institutes of Health and led by researchers at the University of Toronto School of Public Health.

It was very strong, following pregnant women in Mexico and their children for 12 years, and measuring individual urine levels, a more precise method to determine fluoride exposure than drinking water concentrations. The results were undiminished even after adjusting for a wide array of confounding factors, including lead, smoking, alcohol, socio-economic status and birth weight.

The pro-fluoridation lobby, led by the American Dental Association, quickly denied the significance of the study, arguing “the findings are not applicable to the U.S.”

Mexico, like most nations, doesn’t fluoridate its water. The ADA’s stance stems from the fact that the women were mainly getting their fluoride from consuming fluoridated salt or varying natural levels of fluoride in the water. (The ADA ignores the fact that fluoride’s effects are the same once it’s inside the body, no matter the source.)

Most others felt differently. Lead author Dr. Howard Hu asserted “This is a very rigorous epidemiology study. You just can’t deny it. It’s directly related to whether fluoride is a risk for the neurodevelopment of children. So, to say it has no relevance to the folks in the U.S. seems disingenuous.”

Dr. Leonardo Trasande, a pediatrician unaffiliated with the study at New York University, agreed, saying that “This is a very well-conducted study, and it raises serious concerns about fluoride supplementation in water.”