Fluoride Exposure During Pregnancy Linked to Autism-like Behaviors in Children

New research found that prenatal exposure to fluoride levels typically found in community drinking water increased the risk of several neurobehavioral issues in young children, including autism-like symptoms.

The U.S. Public Health Service (PHS) recommends that community drinking water sources should contain 0.7 milligrams of fluoride per liter of water to help prevent dental cavities while minimizing the risk of adverse health effects.

Currently, around 73% of people in the United States drink water from fluoridated community water supplies.

However, the safety of fluoride is the topic of heated debate in an ongoing fluoride court case in California. The case — Food and Water Watch v. United States Environmental Protection Agency — unearthed a National Toxicology Program (NTP) report that found with "moderate confidence" that high fluoride exposure is associated with lower IQ in children.

Still, the NTP report suggests that studies examining fluoride exposure at levels typically found in drinking water in the U.S. are inconclusive, and more research is needed before determining safety.

On May 20, new research published in JAMA Network Open added more evidence that, yes, fluoride may be harmful, especially in children exposed to the mineral during pregnancy.

Fluoride's impact on children

The study, led by researchers at the Keck School of Medicine of USC, analyzed fluoride levels in the urine of 229 mothers from the Maternal and Developmental Risks from Environmental and Social Stressors (MADRES) cohort during the third trimester of pregnancy. MADRES participants are primarily lower-income Hispanic women living in Los Angeles, California.

Then, the team assessed the neurobehavior of their children at age three.

The study's co-author, Tracy Bastain, Ph.D., an associate professor of clinical population and public health sciences at Keck School of Medicine of USC, tells Healthnews that children whose mothers had higher concentrations of fluoride in pregnancy had more neurobehavioral problems in all areas.

Specifically, a 1-IQR increase in maternal urinary fluoride levels was associated with a 13.54% increase in raw scores for the emotionally reactive symptoms and a 19.60% increase in somatic complaint symptoms.

In addition, a 1-IQR increase in maternal urinary fluoride levels was associated with an 11.29% increase in anxiety and an 18.53% increase in autism spectrum disorder-like symptoms.

Furthermore, the participants lived in an area with fluoride exposures typical of those living in fluoridated communities across the United States.

"We measured fluoride levels in urine which represents both recent intake as well as releases from longer-term accumulation in the body," Bastain says. "The levels measured from the 25th percentile to the 75th percentile of our participants was approximately equal to the allowable concentrations in drinking water."

Bastain says the team conducted statistical analyses using this range to contextualize their findings, which allowed them to interpret the results as a comparison from an optimally fluoridated community to a community without fluoridation.

The most important impact of these findings is that this study is contributing to the evidence base that fluoride exposure during pregnancy may be harmful to the developing brain.

Tracy Bastain, Ph.D.

The MADRES cohort focuses on understanding the roles of environmental, individual, and community-level stressors during pregnancy on a variety of health outcomes that disproportionately impact these communities.

"It is critically important that we are able to mitigate and reduce exposures that may contribute to the burden of disease in our most marginalized communities," Bastain explains.

Based on these findings, the team plans to conduct additional research on the impact of fluoride exposure during pregnancy on infant neurodevelopmental outcomes. They also hope to follow the participants in this study beyond the early childhood period to see if these neurobehavioral effects persist.

Bastain tells Healthnews, "We are also working to develop a new consortium of U.S. cohorts of pregnant individuals with fluoride measurements and neurodevelopmental outcomes in children, so future larger scale studies are forthcoming."

Is fluoride a neurotoxin?

While the study's result showed that fluoride may impact the brain development of an unborn child, it did have limitations. For example, it used a relatively small number of primarily Hispanic participants from one region in the U.S., which could limit the generalizability to other groups.

Moreover, the scientists measured fluoride in spot samples rather than 24-hour urine samples, which can be influenced by daily behaviors such as using fluoridated dental products or consuming food or beverages that contain fluoride. However, the study's authors say the participants were fasting when the team obtained the urine samples, which reduced the impact food, drinks, or oral health products may have had on the results.

In addition, the team did not have data on the participants' tap water consumption. Still, they note that the rate of home cooking was high, which could be a source of fluoridated tap water exposure.

Nonetheless, the findings are consistent with other research. For example, a recent Canadian study of over 500 mother-child pairs found that exposure to fluoridated drinking water during pregnancy was associated with lower IQs in children. Additionally, a 2017 study conducted in Mexico found that higher fluoride exposure during pregnancy was associated with lower cognitive function in children.