The study, published Monday in the journal JAMA Pediatrics, found that increased levels of fluoride exposure during pregnancy was associated with lower IQ in children. Previous research has yielded similar results, but this is the first study of its kind to evaluate the effects of fluoride on populations receiving what the US Public Health Service considers optimal: 0.7 mg of fluoride per liter of drinking water, as in the United States and elsewhere. Canada.
The authors of the new study rated 601 Canadian mothers / children couples and followed the exposure of 512 mothers to fluoride by examining the average fluoride concentration in urine samples taken throughout their pregnancy as indirect indicator of prenatal exposure to fluoride. The authors also estimated mothers' daily fluoride intake by examining their drink intake, including tap water.
Between the ages of 3 and 4, all children born to the mothers studied were tested for IQ.
The authors found that for every extra milligram per liter of fluoride concentration in the urine of a mother, IQ had dropped by 4.5 points in men. The study did not highlight such a significant association among girls and also did not examine why boys were affected in a more meaningful way.
The researchers say that it is necessary to continue research to find out if boys are more vulnerable to fluoride neurotoxicity, especially since boys have a higher prevalence of neurodevelopmental disorders such as breast cancer. autism and deficit disorder of attention.
The researchers also measured the fluoride intake of 400 mothers compared to their children's IQ score. According to them, this measure could reflect the postnatal exposure to fluoride because a child ingest probably the same type of water that the mother during pregnancy.
The authors believe that the concentration in the urine better reflects prenatal exposure. They found that for every 1 mg / L average increase in fluoride intake in the mother, there was a 3.7 point decrease in IQ of the child, regardless of sex.
"At the population level, it's a big change .This translates into millions of lost IQ levels," said study author Christine Till, an associate professor in the department. of psychology from York University in Toronto.
Till and his colleagues have monitored their findings for income and education, as well as for other elementary exposures such as lead, mercury, manganese, PFOA and arsenic, but have recognized that there may be unknown exposures that could have affected their conclusions. "There will always be things we do not measure because we did not know it existed," Till said.
Fluoridation remains a controversial issue
Critics pointed out that the difference between boys and girls was a problem in the study.
"The difference between the sexes in the results makes interpretation difficult, at this stage the gender difference is problematic," said Dr. Aparna Bole, Chair of the American Academy of Pediatrics Council on environmental health. Bole said that this research alone will not change any of the organization's recommendations regarding the use of fluoride to prevent cavities, but "I think the study was well done and the commentary was thoughtful.
Grainne McAlonan, a professor of translational neuroscience at the Sackler Institute for Translational Neurological Development at King's College London, said that while the findings were statistically significant, there was little that needed to be done in the practice. "In fact, the average difference in fluoride levels between the majority of people living in low and high fluoride areas is close to 1 mg / L. The average fluoride concentration in non-fluoridated areas is 0 , 4 mg / L, while it is greater than 0.7 mg / L, a difference of only 0.3 mg / L, "McAlonan said.
About 66% of all US residents receive fluoridated water, but water fluoridation has been controversial since it was implemented by local municipalities in the 1950s, due to conspiracy and conspiracy theories. health problems.
Issues related to water fluoridation have sometimes been considered a "marginal science" and the JAMA Pediatrics Editorial Board has acknowledged that publication of the article may be controversial.
In a note from the editor, Dimitri Christakis, director of the Seattle Children's Research Institute, director of the Center for Health, Behavior and Child Development, said the Review "s was committed to disseminating the best scientific data based entirely on the rigor of the methods and the validity of the verified hypotheses, regardless of the controversy of the results."
More research needed
In another editorial, David Bellinger, professor of neurology at Harvard Medical School, wrote that the results were yet to be replicated and that no study could determine the safety and effectiveness of fluoride. But, he added, "despite these considerations, the assumption that fluorine is a toxic substance for neurodevelopment must now be seriously considered."
In an email to CNN, Dr. Pamela Den Besten, a professor in the faculty of dentistry at the University of California at San Francisco, said, "Fluoride remains a safe and effective tool for caries prevention. . " Den Besten has studied the role of fluoride in fluorosis, a condition resulting from excessive exposure to fluoride.
However, she also noted that fluoride was the most effective in topical applications and added that "my bias, given the findings of this study and others, is to focus on the administration. fluoride through strategies that do not require fluoride ingestion ". She added that it would not be unreasonable for pregnant women to use low-fluoride water bottles during pregnancy instead of the tap.
In a statement, the American Dental Association said: "We welcome this thorough scientific study to see if the results can be replicated with methods demonstrating more conclusive evidence."
