Study details

For the study, researchers from the Keck School of Medicine at the University of Southern California (USC) analyzed the urine samples of 229 women during their third trimester of pregnancy. The majority of the women were Hispanic, living in Los Angeles, and were part of other research from USC's MADRES Center for Environmental Health Disparities.

The researchers then asked the moms to fill out a checklist three years later to assess their children's emotional and behavioral health.

They found that children whose mothers had higher levels of fluoride in their urine were 83% more likely to exhibit a variety of neurobehavioral issues, including anxiety, emotional reactivity, and physical complaints like unexplained headaches and stomachaches.

Specifically, the researchers found that a 0.68 milligram per liter increase in fluoride exposure was linked to almost double the risk of a child showing neurobehavioral problems in a range considered close to or at a level to meet the criteria for clinical diagnosis.

Discussion

Almost 75% of Americans consume drinking water containing fluoride, which has been added to public drinking water since 1945 in an effort to help prevent tooth decay. This research marks the first U.S.-based study analyzing the link between prenatal fluoride and childhood behavioral problems.

"I think this is important evidence, given that it's the first U.S.-based study and findings are quite consistent with the other studies published in North America with comparable fluoride exposure levels," said Ashley Malin, an assistant professor in the department of epidemiology at the University of Florida's College of Public Health and Health Professions and lead investigator on the study. "Conducting a nationwide U.S. study on this topic would be important, but I think the findings of the current study and recent studies from Canada and Mexico suggest that there is a real concern here."

Tracy Bastain, an associate professor of clinical population and public health sciences at the Keck School and an author on the study, noted that this isn't the first time fluoride exposure has been linked to problems in brain development.

"In experimental studies, fluoride has shown to cause biochemical changes in brain cells and increased inflammatory reactions even at low doses," she said. "Effects have also been seen on learning and memory in studies in rats."

"This is all critically important for pregnant persons, because studies have shown that fluoride can cross the placenta and the blood-brain barrier, which can harm the developing brain of the fetus," Bastain added.

However, while the children whose mothers had higher levels of prenatal fluoride exposure had greater odds of showing behavioral problems, Bastain cautioned against interpreting the findings as anything other than a potential association.

"I don't think we're at the point where we are saying that water should not be fluoridated. It's generally considered one of the biggest public health wins, certainly for the dental community," she said. "But our results do give me pause. Pregnant individuals should probably be drinking filtered water."

Mark Moss, division director of public health dentistry at the East Carolina University School of Dental Medicine, said he expects the findings to "cause a stir," but also urged caution.

"This is something that deserves a further look," he said. "But in terms of public health practice, no, this doesn't rise to the level of hitting the pause button" on fluoridation.

Nathaniel DeNicola, an OB-GYN in a private practice in Yorba Linda, California, also noted that the neurobehavioral symptoms identified by the mothers in the study didn't necessarily meet the level of clinical diagnosis.

"To say that there was an increase in odds for something that is borderline subclinical, it's hard to say that this now warrants a reconsideration of public health," he said.

However, DeNicola said he does recommend that his pregnant patients use water filters to remove other potentially harmful chemicals from drinking water, like pesticides.

Other experts noted that the study's use of a single urine sample taken during one pregnancy isn't a very reliable indication of true fluoride exposure.

"If researchers truly want to study fluoride intakes and health effects, a robust study must be undertaken in areas of naturally fluoridated water from low concentrations and higher concentrations," said Johnny Johnson, a pediatric dentist and president of the American Fluoridation Society. "Areas like this exist in the U.S. and can easily be done to investigate any health effects whatsoever." (Sharp, CBS News, 5/20; Edwards, NBC News, 5/20; Hamilton, Neuroscience News, 5/20; Dewan, Newsweek, 5/21)

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