The 324-page report is based on analysis of already published research and evaluated 72 studies that investigated the relationship between fluoride exposure and IQ in children. Researchers within the National Toxicology Program (NTP) conducted a comprehensive examination of the potential impact of fluoride exposure on neurodevelopment and cognitive function. The NTP, an interagency program within the National Institutes of Health (NIH), investigates substances that may be harmful to public health. The evidence consistently suggested that higher levels of fluoride exposure, particularly from drinking water that exceeds the World Health Organization's guideline of 1.5 milligrams per liter, are associated with reduced IQ in children. Officials at the U.S. Department of Health and Human Services (HHS) and the Centers for Disease Control and Prevention (CDC) initially blocked the NTP from releasing a draft version of the report, according to emails obtained through a Freedom of Information Act (FOIA) request. These emails were obtained following a lawsuit in which plaintiffs argued that water fluoridation violates the Environmental Protection Agency’s Toxic Substances Control Act. Since 2015, federal health officials have recommended a fluoridation level of 0.7 mg/L in water. According to the report, approximately 1.9 million people in the U.S. are served by water systems containing fluoride levels of 1.5 mg or higher, while around 2 million people use water with fluoride levels at or exceeding 2 mg/L. Fluoride exposure is common and occurs through various sources, including natural ones. The naturally occurring mineral can be found in soil and tea leaves — one cup of black tea can contain fluoride at a concentration of 2.5 mg/L. Similarly, one liter of ocean water contains about 1.2 mg of fluoride. The American Dental Association (ADA) maintains that fluoride prevents tooth decay, which is why U.S. officials began adding fluoride to the water supply. Approximately 63 percent of Americans receive fluoridated water through community water systems. Data was available for both adults and children, with each group evaluated separately. In adults, only two high-quality studies examining cognitive effects were available, while the literature for children was more extensive. Seventy-two studies assessed the association between fluoride exposure and IQ in children, with 19 considered high-quality. Of these, 18 — conducted in five different countries — reported an inverse association between estimated fluoride exposure and IQ in children. Additionally, 46 of the 53 low-quality studies found evidence linking higher fluoride exposure to lower IQ in children. The report marks the first time a federal agency has concluded with "moderate confidence" that higher fluoride exposure is associated with lower IQ in children. The review also identified studies assessing other cognitive or neurodevelopmental outcomes beyond IQ. Although the findings in these areas were less robust compared to the IQ studies, eight of nine high-quality studies showed associations between fluoride exposure and adverse neurodevelopmental effects. While the evidence linking fluoride to other neurodevelopmental outcomes or adult cognitive effects is less conclusive, the findings on children's IQ are significant enough to warrant attention from public health agencies and policymakers.A new government report has found that higher levels of fluoride are associated with lower IQ levels in children.
