Children born to women exposed during pregnancy to fluoridated drinking water were more likely to have neurobehavioural problems, according to a study published in JAMA Network Open.
Dr. Howard Hu, co-author of a study published today in JAMA Network Open, said the study’s findings are concerning because the women were not exposed to particularly high levels of fluoride.
In the first U.S.-based cohort study to examine this link, researchers from the Keck School of Medicine at the University of Southern California (USC), the University of Florida and Indiana University followed 229 mother-child pairs from pregnancy until the children were 3 years old.
They found that a 0.68 milligram per liter (mg/L) increase in fluoride exposure during pregnancy was associated with nearly double the chance of a child, by age 3, exhibiting neurobehavioral problems at or near a level that meets the criteria for a clinical diagnosis.
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Dr. Howard Hu, Flora L. Thornton Chair and Professor of Population and Public Health Sciences at USC and co-author of the study, told The Defender the study’s findings are concerning because the women were not exposed to particularly high fluoride levels.
Their fluoride exposure came primarily from fluoridated tap water in Los Angeles, which has water fluoridation at 0.7 mg/L — typical for fluoridation levels in most U.S. cities and towns and approximately the same level found to have effects in the study.
“When you add this to all the other studies that have been done on this subject in the last few years,” Hu said, “it creates a body of evidence, which — in conjunction with the basic science looking at how fluoride may be toxicologically active on the brain — suggests that the impact of fluoride on neurobehavioral development problems is causal. It’s not just an epidemiological association.”
The authors concluded that it may be necessary to “establish recommendations for limiting exposure to fluoride from all sources during the prenatal period, a time when the developing brain is known to be especially vulnerable to injury from environmental insults.”
Following the advice of public health agencies, most U.S. towns and cities have been adding fluoride to their water systems since 1945. Today’s recommended target rate is 0.7 mg/L.
Community water fluoridation practices have long been celebrated as one of the “great public health achievements” of the 20th century. The Centers for Disease Control and Prevention (CDC) defends the practices as key to public health.
However, a growing body of research establishing that fluoride negatively affects neurodevelopment has led scientists and the public to question water fluoridation over the last several years.
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In 2006, after concluding in a multiyear study that fluoride could interfere with brain function, the National Research Council (NRC) called for more research.
Since then major cohort studies in Mexico and Canada have linked fluoride exposure to lower IQ scores and other neurodevelopmental issues in children.
Cohort studies, in which researchers collect epidemiological data during pregnancy and then from children over their lifetimes to study a variety of health outcomes tied to environmental exposures, are the gold standard of epidemiological studies.
In an ongoing landmark trial, several environmental and consumer watchdog groups are suing the U.S. Environmental Protection Agency (EPA), arguing that water fluoridation at existing levels threatens human health and that water fluoridation ought to be ended or much more strictly regulated.
Despite the recent studies and the NTP’s findings, the EPA maintained in court that there is insufficient evidence that fluoride poses a neurodevelopmental risk to children to warrant changing or ending current water fluoridation policy recommendations.
The fluoride lobby and many officials in public health agencies defend the EPA’s opinion. However, the surgeon general’s office notably stopped issuing public statements supporting water fluoridation after the NTP published its report.
The JAMA study analyzed data from the Maternal and Developmental Risks from Environmental and Social Stressors (MADRES) pregnancy cohort study, which consisted of predominantly low-income Latina women in Los Angeles.
Earlier work on fluoride published in JAMA in 2019 found that higher levels of fluoride exposure during pregnancy led to reduced IQ in children by ages 3 and 4. That paper received much more detailed scrutiny by reviewers than is usual for JAMA papers, plus an editorial explaining why the journal chose to publish the article, she said.
“Given the potentially controversial nature of the new paper, it is likely that it also received extra scrutiny. The fact that JAMA published the 2019 article and the recent article indicates that the editors and reviewers consider each of the articles to be of very high quality and importance.”