On Jul. 25, 2012, in a meta-analysis, researchers from Harvard School of Public Health (HSPH) and China Medical University in Shenyang, for the first time combined 27 studies and found strong indications that fluoride may adversely affect cognitive development in children. Based on the findings, the authors say that this risk should not be ignored, and that more research on fluoride’s impact on the developing brain is warranted.

The researchers conducted a systematic review of studies, almost all of which are from China where risks from fluoride are well-established. Fluoride is a naturally occurring substance in groundwater, and exposures to the chemical are increased in some parts of China. Virtually no human studies in this field have been conducted in the U.S.

Some studies suggested that even slightly increased fluoride exposure could be toxic to the brain. The children in high-fluoride areas had significantly lower IQ scores than those who lived in low-fluoride areas. The children studied were up to 14 years of age, but the investigators speculate that any toxic effect on brain development may have happened earlier, and that the brain may not be fully capable of compensating for the toxicity.

“Fluoride seems to fit in with lead, mercury, and other poisons that cause chemical brain drain,” says senior author Philippe Grandjean, adjunct professor of environmental health at the Harvard School of Public Health (HSPH). “The effect of each toxicant may seem small, but the combined damage on a population scale can be serious, especially because the brain power of the next generation is crucial to all of us.” The study was published online in Environmental Health Perspectives.