11 February 2013. When an article on fluoride neurotoxicity was published in the summer of 2012, it went virtually unnoticed beyond the research community, at first. The article summarized 27 studies, mainly from China, on IQ in relation to fluoride concentrations in drinking water.
But in the fall, fluoridation of drinking water was on the agenda in the two largest cities that are not fluoridated – Wichita, Kansas and Portland, Oregon.
With election day approaching, a Kansas newspaper reported on the controversy regarding alleged fluoride benefits and risks: “Harvard University scientists say that Wichita voters shouldn’t depend on a research study they compiled to decide whether to put fluoride in the city’s drinking water to fight tooth decay. While the studies the Harvard team reviewed did indicate that very high levels of fluoride could be linked to lower IQs among schoolchildren, the data is not particularly applicable here because it came from foreign sources where fluoride levels are multiple times higher than they are in America tap water.”
The article did not explain why studies from another country would not be relevant, and why effects observed at increased exposures could be disregarded.
Another Kansas newspaper stated: “But the study’s authors acknowledged that their report – actually a study of other studies – showed slightly lower IQ levels in kids who drank water with fluoride levels 10 times what is found in U.S. water supplies.”
However, neither newspaper checked their information with the authors, even though statements were attributed to them.
Here is what the study showed: On average, the children with higher fluoride exposure showed poorer intelligence test performance. The high exposures generally exceeded the concentrations normally occurring in fluoridated drinking water, but only 4 of 27 studies reached an excess of 10-fold, and clear differences were found also at much lower exposures.
Addition of fluoride to drinking water has been controversial since the very beginning in the 1940s. As noted in a National Research Council report, neither benefits nor risks have been thoroughly documented. Current dietary intakes of fluoride and dental hygiene practices differ from the circumstances first studied in the mid-20th century. By now, less than 6% of the world population receive what some dentists call “optimal” fluoride concentrations in drinking water, and safety concerns continue to linger.
At the same time, many millions of people receive drinking water with fluoride concentrations that are clearly toxic. Benefits and risks, and their dependence on dose and individual susceptibility, need to be carefully evaluated, also in regard to alternative interventions, when relevant.
Chemical brain drain should not be disregarded. The average IQ deficit in children exposed to increased levels of fluoride in drinking water was found to correspond to about 7 points – a sizable difference. To which extent this risk applies to fluoridation in Wichita or Portland or elsewhere is uncertain, but definitely deserves concern.