Study: Adding fluoride to water would affect children’s IQ

Fluoride, added to tap water in several countries, including the United States, could affect the intelligence quotient of children, says a scientific analysis published Monday and already criticized, reviving a heated scientific and political debate in North America.

The work carried out by researchers from NIEHS, an American government institute, consists of a meta-analysis of 74 studies carried out in ten countries, including China and Canada, but not the United States. It concludes that, in 54 of them, a reduction in the IQ of children exposed to certain levels of fluoride in running water was observed.

This observation, published in the journal “JAMA Pediatrics”, is questioned by experts, who point out in particular methodological pitfalls and significant flaws in the underlying studies. Others assure, on the contrary, that it is the “most rigorous meta-analysis ever carried out” and call for “reassessing the potential risks of fluoride during early brain development”.

But as the inauguration of Donald Trump approaches, who wants to see Robert Kennedy Jr., a fierce opponent of water fluoridation, at the Department of Health, some scientists fear that this publication will erode public confidence in health institutions.

In the United States, only a few areas have naturally fluoridated water. Since the 1950s, health authorities in the rest of the country have, with a few exceptions, added fluoride, which helps prevent dental caries.

If there is consensus on the dangerousness of fluoride at high concentrations, it is the question of the “toxicity threshold” that divides the scientific community. In the publication, the researchers suggest, based on a small number of studies, that even a concentration below 1.5 mg/L – the maximum threshold recommended by the WHO – could affect children’s IQ.

However, “almost all studies have been carried out in contexts where there are other contaminants,” notes Steven Levy, professor at the Iowa Institute of Oral Health, citing coal pollution as an example. China. And other studies analyzed in the publication present contrary results. There remains “uncertainty” about the effects of such concentration, its authors also recognize.

“There is simply not enough data” to determine today with certainty a toxicity threshold, summarizes David Eaton, professor emeritus at the University of Washington and former president of the American Society of Toxicology.

Since other sources of fluoride exist, notably in toothpastes, we must reassess the benefits of such a practice by studying the effects observed after “the cessation of fluoridation in several localities”, argues Fernando Hugo, public health researcher. dental.

Proponents of fluoridation argue that it helps reduce socioeconomic disparities, with vulnerable populations often lacking access to adequate dental care. But its critics argue that these same communities may be most at risk of potential adverse effects like a decline in children’s IQs.