Children exposed to fluoride in the womb at levels meeting the federal safety threshold scored measurably lower on memory and problem-solving tests, according to a study of more than 2,500 U.S. children.
The study, published in the American Journal of Epidemiology and funded by the National Institutes of Health, identified that prenatal fluoride levels of 0.675 mg per liter (mg/L) were a change-point in the data.
When mothers’ neighborhood water supply reached about this level or higher, each additional increase of 0.5 mg/L was associated with a nearly 3.5-point drop in children’s problem-solving scores.
To give the numbers some context, 0.675 mg is lower than the U.S. Public Health Service’s current recommendation of 0.7 milligrams of fluoride per liter.
The study found the strongest effect in children younger than age 7.
Declines in Problem Solving
Researchers tracked children born between 2006 and 2019, testing their cognitive abilities between ages 3 and 17. To estimate each child’s fluoride exposure before birth, the team matched fluoride measurements from local water systems to the addresses where mothers lived during pregnancy.
The study found a link between fluoride exposure and fluid cognition: the ability to solve new problems, retain short-term information, and adapt. It did not find a link between fluoride and “crystallized cognition”—skills such as vocabulary and general knowledge that are typically built up through education and experience.
Fluoride is added to water to prevent tooth decay and protect enamel. Although fluoride is also added to toothpastes and mouthwash, these products are only meant to sit on the tooth surface and be spit out, while water fluoridation is ingested and absorbed, Dr. Kevin Khachatryan, cofounder and dentist at the Empower Dental Group in California, and not involved in the study, told The Epoch Times.
Animal and toxicological studies have linked fluoride to a neurotoxin. During pregnancy, ingested fluoride can cross the placental barrier, directly exposing the developing fetus and accumulating inside the brain.
At a cellular level, fluoride is a trigger for oxidative stress. It increases the production of free radicals, which can damage neurons and deplete the brain’s natural antioxidant defenses. Fluoride has been shown to impair the production of critical neurotransmitters in the brain, including serotonin, dopamine, and norepinephrine.
Regulation Battles
The study arrives in the middle of a fast-moving political and legal battle over fluoride’s future in U.S. drinking water.
In September 2024, Senior Judge Edward Chen of the U.S. District Court for the Northern District of California ruled that current fluoride levels of 700 mg/L already pose an unreasonable risk to children’s neurodevelopment and asked the Environmental Protection Agency (EPA) to review the evidence to see whether the current fluoride recommendations should be altered.
The level at which Chen ruled required further review was far lower than the EPA’s upper limit of 4 mg/L. The EPA has since appealed Chen’s decision.
However, in August, Health and Human Services (HHS) Secretary Robert F. Kennedy Jr. directed the EPA to work alongside HHS to conduct a baseline scientific evaluation of fluoride safety.
Although the EPA has successfully appealed the decision to conduct a fluoride safety evaluation in court, it will still have to do the review because of HHS administrative orders.
Dentists not involved in the study urged caution on both sides of the debate. Every public health decision will have its risks and benefits, and decisions in dentistry are no exception, Dr. Steve Mascarin, a dentist and CEO of Eleven Dental in Toronto, who was not involved in the study, told The Epoch Times.
“[For this reason,] we must be sure to recognize the cumulative research that supports this position,” he said.
“However, we must also remain open to further research on this topic to inform our practice as science is still capable of evolving our understanding of fluoride.”
Dr. Michael J. Wei, a cosmetic and restorative dentist in Manhattan, echoed that the new findings deserve attention without overstatement: “This study raises important questions about prenatal fluoride exposure and contributes valuable data to an ongoing area of research.”
For now, the study’s authors said the priority is more research. They are calling for further work to identify exactly when during pregnancy or childhood fluoride exposure matters most and how to weigh any developmental risks against fluoride’s well-documented benefits for preventing tooth decay.
