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A controversial new study published Monday in JAMA Pediatrics has reignited the debate over the safety of fluoride in drinking water, with researchers linking higher exposure levels to a reduction in children’s IQ scores. The findings, which suggest a potential connection between fluoride exposure and lower cognitive function, have already sparked intense pushback from some experts who defend the mineral’s dental benefits.
The study, conducted by scientists from the National Institute of Environmental Health Sciences (NIEHS), reviewed 74 studies on fluoride exposure and children’s IQ from 10 countries, including Canada, China, and India. The team, which helped form an official government recommendation in August suggesting “moderate confidence” in a link between higher fluoride levels and reduced IQ, reported that their latest analysis found a “statistically significant association” between fluoride exposure and lower IQ scores in children.
The study estimates that for every 1 milligram per liter increase in urinary fluoride—a marker of overall exposure—children’s IQ could drop by 1.63 points. While the neurotoxic effects of high fluoride exposure are well-established, the new findings raise concerns about levels below 1.5 milligrams per liter—the World Health Organization’s recommended safety limit.
However, the paper has drawn criticism from many in the scientific community. Steven Levy, a member of the American Dental Association’s national fluoride committee, raised doubts about the study’s methodology. He pointed out that 52 of the 74 studies reviewed were rated as “low quality” by the authors themselves but were still included in the analysis. Levy also criticized the study’s reliance on single-point urine samples instead of 24-hour collections, which provide more accurate results.
In an editorial published alongside the study, Levy emphasized that the findings should not impact current public health policies. “With so many uncertainties, the evidence base is insufficient to warrant changes in fluoride exposure guidelines,” he argued.
Despite these criticisms, the benefits of fluoride, especially in water fluoridation, remain widely recognized. Introduced in the U.S. in 1945, water fluoridation has been credited with significantly reducing cavities in children and preventing tooth loss in adults, earning the endorsement of the Centers for Disease Control and Prevention (CDC) as one of the 20th century’s greatest public health achievements.
Fluoride helps remineralize teeth, reducing cavity-causing bacteria and making it more difficult for bacteria to adhere to teeth. Since the 1960s, fluoride toothpaste has been widely available, raising questions about the continued necessity of fluoridating public water supplies. Supporters argue that fluoridation remains a vital tool for reducing dental health disparities, while critics warn it may pose a hidden risk to vulnerable populations, particularly children.
The debate is further fueled by the upcoming change in U.S. leadership. As President-elect Donald Trump prepares to take office, his nominee for Health Secretary, Robert F. Kennedy Jr., has been an outspoken critic of fluoridated water. In the U.S., more than 200 million Americans—about two-thirds of the population—drink fluoridated water.
Fernando Hugo, Chair of the NYU College of Dentistry, told AFP that more research is urgently needed to assess the risks and benefits of fluoride exposure, particularly within the context of U.S. public health policies.
The new study’s findings have placed the spotlight on fluoride’s potential neurological impact, prompting calls for further investigation and, for some, a reassessment of current practices. As this debate unfolds, experts continue to weigh the potential costs of fluoridation against its undeniable benefits in oral health.
For more information, see Fluoride Exposure and Children’s IQ Scores, Kyla W. Taylor et al., JAMA Pediatrics (2025), DOI: 10.1001/jamapediatrics.2024.5542.
