Higher fluoride levels in pregnant women tied to children's neurobehavioral problems

Higher fluoride levels in pregnant women are linked to increased odds of their children exhibiting neurobehavioral problems at age 3, according to a new study led by a University of Florida College of Public Health and Health Professions researcher.

The findings, based on an analysis involving 229 mother-child pairs living in a U.S. community with typical fluoride exposure levels for pregnant women in fluoridated regions in North America, appear May 20 in the journal JAMA Network Open. It is believed to be the first U.S.-based study to examine associations of prenatal fluoride exposure with parent-reported child neurobehavioral issues, which include symptoms of anxiety, difficulty regulating emotions and other complaints, such as stomachaches and headaches.

Fluoride, a mineral, has been added to community water supplies since the 1940s as a way to reduce dental cavities in children and adults. Nearly three-quarters of the U.S. population receives fluoridated tap water. The impacts of fluoride on human health, both positive and negative, have been the subject of much recent debate and ongoing scientific scrutiny.

The study's lead investigator Ashley Malin, Ph.D., an assistant professor in the department of epidemiology in the UF College of Public Health and Health Professions and UF College of Medicine, said that taken with other recent studies conducted in Canada and Mexico on the effects of fluoride on young children's IQ, the findings suggest fluoride may negatively affect fetal brain development.

There is no known benefit of fluoride consumption to the developing fetus, but we do know that there is possibly a risk to their developing brain. We found that each 0.68 milligram per liter increase in fluoride levels in the pregnant women's urine was associated with nearly double the odds of children scoring in the clinical or borderline clinical range for neurobehavioral problems at age 3, based on their mother's reporting."

Ashley Malin, Ph.D., assistant professor in the department of epidemiology, UF College of Public Health and Health Professions and UF College of Medicine

The fluoride levels found in the study participants' samples are typical for people living in communities with fluoridated water, the researchers say. However, according to the paper, authors do not know whether findings observed in this study are generalizable to other U.S. populations or are nationally representative and therefore more research is required to address that question.

Individual differences in a person's fluoride exposure can be attributed to variances in dietary consumption, such as drinking and cooking with tap water versus filtered water, or consuming food and drinks naturally high in fluoride, including green and black tea, certain seafoods and foods sprayed with fluoride-containing pesticides.

For the new study, investigators used data from the Maternal and Developmental Risks from Environmental and Social Stressors, or MADRES, study conducted at the Keck School of Medicine of USC. MADRES is led by Tracy Bastain, Ph.D., the senior author of the current fluoride study and an associate professor of clinical population and public health sciences, and Carrie Breton, Sc.D., a professor of population and public health sciences. The MADRES study follows a group of predominantly Hispanic women with low-income and their children living in Los Angeles County from pregnancy through childhood.

Researchers collected urine samples from MADRES participants during their third trimester of pregnancy. Urinary fluoride is the most widely used measure of individual fluoride exposure in epidemiological studies, including those assessing effects on fetal brain development. Because fluoride, when combined with disinfecting agents, may cause lead to leach from lead-bearing water pipes, the scientists conducted various analyses to be sure any neurobehavioral effects could not be attributed to lead.

When their children reached age 3, study mothers completed the Preschool Child Behavior Checklist, which assesses children's behavior and emotions. The investigators found that women with higher fluoride exposure during pregnancy tended to rate their children higher for overall neurobehavioral problems.

The study team hopes their findings spur policymakers to create specific recommendations for fluoride consumption during pregnancy.

"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," Malin said. "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."

Malin's research is supported by the National Institute of Environmental Health Sciences of the National Institutes of Health. The MADRES study is funded by the Environmental Protection Agency.