A recent report from the National Toxicology Program, part of the Department of Health and Human Services, has identified a potential link between elevated fluoride exposure and decreased IQ in children. This finding, based on an analysis of existing research, marks the first time a federal agency has noted—“with moderate confidence”—such a connection.
While the report did not specifically assess the health impacts of fluoride in drinking water alone, it underscores a notable concern regarding the neurological effects of excessive fluoride. Fluoride, a mineral known for its role in strengthening teeth and reducing cavities, has been added to public water supplies for decades, with the Centers for Disease Control and Prevention (CDC) citing it as a major public health achievement.
Ashley Malin, a researcher at the University of Florida who has examined the effects of fluoride on children of pregnant women, described the report as a significant advancement in understanding fluoride’s potential risks. She praised it as the most rigorously conducted study on this subject to date.
The report, released on Wednesday, synthesizes data from studies conducted across several countries, including Canada, China, India, Iran, Pakistan, and Mexico. It highlights a correlation between fluoride concentrations exceeding 1.5 milligrams per liter in drinking water and lower IQ levels in children. Although the report did not provide a precise quantification of IQ loss, some studies suggested a reduction of 2 to 5 points in children with higher fluoride exposure.
Since 2015, U.S. health officials have recommended a fluoride concentration of 0.7 milligrams per liter in drinking water, reduced from a previous upper limit of 1.2 milligrams per liter. The World Health Organization (WHO) maintains a safe fluoride threshold of 1.5 milligrams per liter. According to the report, approximately 0.6% of the U.S. population—around 1.9 million people—receive drinking water with fluoride levels at or above this limit.
The report’s findings raise important questions about protecting those exposed to high fluoride levels and addressing potential health risks. However, it does not address the impact of lower fluoride concentrations or potential effects on adults.
The American Dental Association, a proponent of water fluoridation, had previously critiqued earlier analyses of fluoride’s effects, including Malin’s research. A spokesperson for the association indicated that experts are still reviewing the latest report.
Fluoride, present naturally in water and soil, was first introduced into U.S. public water systems in Grand Rapids, Michigan, in 1945. Federal endorsement of fluoridation to prevent tooth decay followed in 1950. Despite the introduction of fluoride toothpaste, drinking water remains a primary source of fluoride for Americans.
In 2015, the recommendation for fluoride levels was reduced to mitigate the risk of dental fluorosis—a condition causing enamel discoloration. Additionally, the Environmental Protection Agency (EPA) enforces a maximum fluoride concentration of 4 milligrams per liter to prevent skeletal fluorosis, a severe condition affecting bone strength and mobility.
Ongoing studies have increasingly suggested potential impacts of high fluoride levels on brain development. Research has raised concerns about fluoride’s effects on developing fetuses and young children who consume formula mixed with fluoridated water. Previous animal studies indicated that excessive fluoride could affect brain regions involved in learning and memory.
The National Research Council called for further research into fluoride’s neurological effects in 2006, based on evidence from China. The National Toxicology Program began its review in 2016 and has faced delays in finalizing its conclusions.
Rick Woychik, Director of the National Toxicology Program, emphasized the importance of accuracy in addressing fluoride’s public health implications. Malin suggests that pregnant women should consider reducing fluoride intake from various sources and proposes discussions on mandating fluoride content labels on beverages.
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