Children’s exposure to high levels of fluoride is “consistently associated” with lower IQ and possibly other neurodevelopmental problems, according to a report from the National Toxicology Program (NTP).
In 2016, the NTP began a systematic review of the scientific literature to investigate the relationship between fluoride and cognition. On August 21, a report detailing its findings was published. They reviewed 72 studies, of which 64 found an “inverse association between estimated fluoride exposure and children’s IQ,” indicating that the higher the fluoride exposure, the lower the IQ.
The report concludes with moderate confidence that high fluoride exposure is consistently linked to lower IQ in children. The NTP, which is part of the U.S. Department of Health and Human Services, defined high exposure as the presence of fluoride in water at concentrations greater than 1.5 mg/L, the World Health Organization limit.
In the US, the limits are different. The FDA (Food and Drug Administration) sets a limit of 0.7 mg/L of fluoride in drinking water, while the Environmental Protection Agency (EPA) sets the maximum at 2 mg/L.
As of April 2020, approximately 0.59% of the U.S. population, or 1.9 million people, received water with 1.5 mg/L or more naturally occurring fluoride. Approximately 1 million people consumed water with 2 mg/L or more.
The report also mentions that there is evidence of other effects of fluoride on cognitive and neurological development in children, but due to the variation in results, confidence in these data is limited.
The reviewed studies on childhood IQ were conducted in 10 countries, including Canada and Mexico, but no U.S. studies were included.
Fluoride is a mineral that helps prevent and repair tooth damage caused by bacteria. In 1945, the United States introduced water fluoridation as an effective public health measure. However, the NTP expressed concern that children and pregnant women may be ingesting too much fluoride from a variety of sources, including water, beverages, toothpastes, and teas. This concern prompted the current study.
Fluoride debate
The NTP report comes after a May study of mothers and children in Los Angeles found a link between prenatal fluoride exposure and neurobehavioral problems in children.
Ashley Malin, lead researcher, said fluoride can negatively impact fetal brain development and stressed there is “no known benefit” to consuming fluoride during pregnancy.
“Every 0.68 mg/L increase in fluoride levels in pregnant women’s urine was associated with nearly doubling the odds of their children having neurobehavioral problems at age 3,” Malin said.
The American Dental Association (ADA), in a May 22 statement, said the study was not “nationally representative” and did not assess “actual consumption of fluoridated water.”
According to the ADA, “the study should be considered exploratory.” So far, the association has found no peer-reviewed evidence that changes its recommendation to brush twice a day with fluoride toothpaste and drink adequately fluoridated water.
The ADA noted that tooth decay is one of the most common chronic diseases among children, and decades of research indicate that water fluoridation reduces cavities by 25 percent in both children and adults. The organization continues to support water fluoridation as a safe, beneficial and cost-effective measure for dental health.
Another study, published in January, found that many parents expose their children to excessive levels of fluoride. When they used toothpaste on children under 24 months, the dose of fluoride administered was 5.9 to 7.2 times higher than the recommended dose.
