Exposing children to high levels of fluoride is “consistently associated” with lower IQ, and potentially other neurodevelopmental issues, according to a report by the National Toxicology Program (NTP).
In 2016, NTP started a systematic review of scientific literature to ascertain links between fluoride and cognition. On Aug. 21, it published a report detailing its findings. A total of 72 studies reviewed in the report examined how fluoride exposure affected children’s IQ. Sixty-four of these studies found an “inverse association between estimated fluoride exposure and IQ in children,” meaning higher exposure was linked to lower IQ and vice versa.
“This review finds, with moderate confidence, that higher estimated fluoride exposures ... are consistently associated with lower IQ in children,” the report stated. NTP is a unit of the U.S. Department of Health and Human Services.
NTP defined high exposure as drinking water with fluoride concentrations that exceed the 1.5 mg/L limit set by the World Health Organization.
The allowable limits in the United States are different. While the U.S. Food and Drug Administration (FDA) has set a threshold of 0.7 mg/L for fluoride presence in drinking water (including naturally occurring and added fluoride, or fluoridation), 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 0.59 percent of the country’s population, which comes to approximately 1.9 million people, NTP stated. Around 1 million people were supplied water with 2 mg/L or more of naturally occurring fluoride.
“There is also some evidence that fluoride exposure is associated with other neurodevelopmental and cognitive effects in children; although, because of the heterogeneity of the outcomes, there is low confidence in the literature for these other effects,” the report stated.
The studies on children’s IQ reviewed in the report were conducted in 10 countries, including Canada and Mexico. No studies from the United States were included in the review.
Fluoride is a mineral that prevents and repairs damage to the teeth caused by bacteria. In 1945, the United States introduced a community water fluoridation program, which has been considered a successful public health measure.
However, there were concerns that children and pregnant women may ingest fluoride in excess amounts due to exposure to the mineral from a variety of sources, including water, beverages, toothpaste, and teas, the NTP said. This led the program to conduct the current study.
Fluoride Debate
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.
Lead investigator of the study Ashley Malin said the results suggest fluoride may negatively affect fetal brain development. She pointed out that there is “no known benefit” of fluoride consumption for fetuses.
“We found that each 0.68 milligram per liter increase in fluoride levels in the pregnant women’s urine was associated with nearly double the odds of children scoring in the clinical or borderline clinical range for neurobehavioral problems at age 3, based on their mother’s reporting,” she said.
In a May 22 statement, the American Dental Association (ADA) said the study was not “nationally representative” and that it did not measure the “actual consumption of fluoridated water.”
“The JAMA study should be considered exploratory. To date, the ADA has seen no peer-reviewed research that would change its long-standing recommendation to the public to brush twice a day with fluoride toothpaste and drink optimally fluoridated water,” the group said.
“Tooth decay is one of the most common chronic diseases among children. There are decades of research and practical experience indicating community water fluoridation is safe and effective in reducing cavities by 25 percent in both children and adults.”
It endorsed community water fluoridation as a “safe, beneficial, and cost-effective” way to prevent dental cavities.
Another study from January found that many parents were exposing children to high amounts of fluoride. When parents used toothpaste for their children aged under 24 months, the fluoride dose was 5.9 to 7.2 times higher than what was recommended, the study found.
