Since the 1950s, American health authorities have added fluoride, which helps prevent dental caries.
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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 10 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.
“For each increase of 1 mg/L of fluoride in urine (…) there is a reduction of 1.63 IQ points in children,” summarize the authors in a press release sent to AFP.
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.
Toxicity threshold
Fluoride occurs naturally in groundwater in several regions of the world, particularly in Africa and Asia, at concentrations that can exceed the health limit of 1.5 mg/L established by the World Health Organization (WHO). Its presence in running water can also result from industrial contamination.
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.
According to a government website, 200 million Americans would receive artificially fluoridated water in 2022.
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 a concentration below 1.5 mg/L – the WHO threshold – 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.
They add that there is “not enough data” to determine whether the level of 0.7 mg/L, recommended by the American authorities for artificial fluoridation, affects IQ.
“There is simply not enough data” to determine today with certainty a toxicity threshold, summarizes to AFP David Eaton, professor emeritus at the University of Washington and former president of the American Society of Toxicology. .
“Huge mistake”
The authors and scientists interviewed by AFP, however, agree on one point: the need to carry out other studies to evaluate the effects of low concentrations of fluoride on cognitive development.
More broadly, the scientific community is questioning the need to continue adding fluoride to tap water, a practice nevertheless hailed as a great public health success.
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.
In September, a federal judge, based on a document produced by the authors of the study, had also called on the American authorities to look into the subject.
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.
“Stopping water fluoridation without a clear assessment of the current benefits would be a huge mistake because there is no doubt that it has had a significant positive impact on public health in the past,” says David Eaton. , who emphasizes that the study only focuses on the risks of fluoridation.
(afp)
