A new report from the National Toxicology Program (NTP) has found that children exposed to high levels of fluoride may experience lower IQ, adding to the growing controversy over fluoride’s role in public health. Published on August 21, the report is based on a review of 72 studies, 64 of which found a significant connection between high fluoride exposure and reduced cognitive abilities in children.

The report defines “high exposure” as fluoride concentrations exceeding 1.5 mg/L, which is the limit set by the World Health Organization (WHO). In the United States, the EPA permits up to 2 mg/L in drinking water, while the FDA recommends a lower threshold of 0.7 mg/L. The NTP report estimates that nearly 2 million Americans currently receive water with fluoride levels above 1.5 mg/L, putting children at risk for cognitive harm.

Fluoride has been widely used in public water systems since 1945 to reduce tooth decay, a practice credited with improving dental health nationwide. However, concerns have grown in recent years over potential side effects, particularly for children and pregnant women. The NTP report also hints at possible links between fluoride exposure and other neurodevelopmental issues, although the evidence is less robust.

Earlier this year, a study linked prenatal fluoride exposure to neurobehavioral problems in children, suggesting that fluoride may affect brain development in the womb. Despite these findings, the American Dental Association (ADA) maintains its support for water fluoridation, arguing that the benefits in preventing cavities are well-established.

The NTP report may prompt health authorities to revisit existing guidelines, especially in areas with high naturally occurring fluoride levels, as concerns over the potential cognitive risks continue to grow.