A new report from the US government, expected to spark significant discussion, has found that fluoride levels in drinking water that exceed the recommended amount may be linked to lower IQs in children.
This report, the first from a federal agency to “moderately confidently” establish this connection, reviews existing research and highlights potential risks associated with high fluoride exposure. The report does not specifically assess the health impacts of fluoride in drinking water alone, but it does acknowledge the potential neurological risks of excessive fluoride.
Fluoride is known to strengthen teeth and reduce cavities by replacing lost minerals, according to the US Centers for Disease Control and Prevention (CDC). Adding low levels of fluoride to drinking water has long been recognized as a major public health achievement.
Ashley Malin, a researcher at the University of Florida, emphasized the importance of this report. She described it as the most rigorously conducted study on the topic, providing crucial insights into the risks associated with high fluoride levels.
Released on Wednesday, the report from the National Toxicology Program, part of the Department of Health and Human Services, reviews studies from countries including Canada, China, India, Iran, Pakistan, and Mexico. It concludes that drinking water with fluoride levels above 1.5 milligrams per liter is consistently linked to lower IQs in children.
While the report does not specify the exact IQ point loss associated with different fluoride levels, some studies reviewed suggested a reduction of 2 to 5 IQ points in children with higher fluoride exposure.
Since 2015, US health officials have recommended a fluoride level of 0.7 milligrams per liter in drinking water, down from a previous upper limit of 1.2 milligrams per liter. The World Health Organization sets a safe limit of 1.5 milligrams per liter.
The report notes that about 0.6% of the US population—approximately 1.9 million people—receive water with naturally occurring fluoride levels of 1.5 milligrams or more.
Malin highlighted the need to explore protective measures for these individuals and to consider the implications of these findings.
The 324-page report does not address the risks associated with lower fluoride levels or the effects of high fluoride levels on adults. The American Dental Association, which supports water fluoridation, has been critical of earlier analyses and Malin’s research. A spokeswoman indicated that the organization’s experts are still reviewing the new report.
Fluoride, a naturally occurring mineral in water and soil, was found to reduce cavities when added to drinking water. The practice began in Grand Rapids, Michigan, in 1945 and was endorsed by federal officials in 1950. Although fluoride can come from various sources, drinking water is the primary source for Americans.
In 2015, recommendations for fluoride levels in drinking water were reduced to address fluorosis, a condition that causes tooth discoloration and was becoming more common in US children.
The Environmental Protection Agency (EPA) continues to enforce a maximum fluoride level of 4 milligrams per liter in water to prevent skeletal fluorosis, which causes bone issues and stiffness.
Recent studies have increasingly raised concerns about the impact of high fluoride levels on brain development. Animal studies suggest fluoride might affect brain areas related to learning, memory, and behavior. In 2006, the National Research Council called for more research on fluoride’s impact on intelligence. The National Toxicology Program has since worked on reviewing studies to determine if new fluoride regulations are necessary.
The final report faced delays and revisions. Rick Woychik, director of the National Toxicology Program, emphasized the importance of accurate science due to the public and health officials’ interest in fluoride.
Malin suggested that pregnant women might consider reducing their fluoride intake from water and certain teas. She also proposed discussions on whether beverage labels should include fluoride content.
