Exposure to high levels of fluoride is consistently associated with lower IQ and other neurodevelopmental issues in children, according to a report by the National Toxicology Program (NTP. The NTP conducted a systematic review of scientific literature on the subject, finding that 64 out of 72 studies reviewed found an inverse association between estimated fluoride exposure and IQ in children. The report states that there is “moderate confidence” that higher estimated fluoride exposures are associated with lower IQ in children.
The NTP defined high exposure as drinking water with fluoride concentrations that exceed the 1.5 mg/L limit set by the World Health Organization (WHO. In the United States, the U.S. Food and Drug Administration has set a threshold of 0.7 mg/L for fluoride presence in drinking water, while the U.S. Environmental Protection Agency has a limit of 2 mg/L. As of April 2020, community water systems in the United States supplied water containing 1.5 mg/L or more of naturally occurring fluoride to approximately 1.9 million people, with around 1 million people being supplied water with 2 mg/L or more of naturally occurring fluoride.
The NTP report also found some evidence that fluoride exposure may be associated with other neurodevelopmental and cognitive effects in children, although there is low confidence in the literature for these other effects. The studies on children’s IQ reviewed in the report were conducted in 10 countries, including Canada and Mexico, but no studies from the United States were included in the review.
Fluoride is a mineral that prevents and repairs damage to teeth caused by bacteria, and in 1945, the United States introduced a community water fluoridation program, which has been considered a successful public health measure. However, there have been concerns that children and pregnant women may ingest fluoride in excess amounts due to exposure from various sources, including water, beverages, toothpaste, and teas. This led the NTP to conduct the current study.
The NTP report follows a study published in May that looked at mother-child pairs from Los Angeles and concluded that prenatal fluoride exposure was associated with “neurobehavioral problems” among children. The American Dental Association (ADA) has stated that the JAMA study should be considered exploratory, as it did not measure the “actual consumption of fluoridated water.” Despite concerns about high levels of fluoride exposure in children, the ADA continues to endorse community water fluoridation as a “safe, beneficial, and cost-effective” way to prevent dental cavities.
