Study links high fluoride exposure to lower IQ in children

Water fluoridation is widely seen as one of the greatest public health achievements of the 20th century, credited with broadly reducing tooth decay. However, there is growing controversy among scientists about whether fluoride may be linked to lower IQ scores in children.

A comprehensive federal analysis of previous study results, published this week in JAMA Pediatrics, added to these concerns. Found relevant inverse relationship between exposure levels and cognitive function in children.

Scientists working for the National Institute of Environmental Health Sciences have linked higher fluoride exposure to lower IQ.

None of the studies included in the analysis were conducted in the United States, where recommended levels of fluoridation in drinking water are very low. For these amounts, the evidence was too constrained to draw definitive conclusions.

Observational studies cannot demonstrate a cause-and-effect relationship. But in countries with much higher levels of fluoridation, the analysis also found evidence of what scientists call a dose-response relationship, with IQ scores falling as exposure to fluoride increases.

Children are exposed to fluoride from many sources other than drinking water: toothpaste, dental products and some mouthwashes, as well as black tea, coffee and certain foods such as shrimp and raisins. Some drugs and industrial emissions also contain fluorine.

The analysis found that for every part per million escalate in fluoride in urine samples, which reflects overall exposure to water and other sources, children’s IQ points drop by 1.63.

“There are concerns that pregnant women and children are getting fluoride from multiple sources,” said Kyla Taylor, an epidemiologist at the institute and lead author of the report, “and that their total exposure to fluoride is too high and could impact the fetus, infant and child neurodevelopment.”

Dr Taylor said the analysis was intended to contribute to understanding the unthreatening and effective employ of fluoride. But it said it did not address benefits and was not intended to assess “the broader public health consequences of water fluoridation in the United States.”

Several scientists, including many dentists, criticized the report, pointing out what they said were methodological flaws and emphasizing that the study had no impact on U.S. drinking water.

The topic is so divisive that JAMA Pediatrics commissioned two editorials with opposing viewpoints to be published alongside the report.

In one, Dr. Steven M. Levy, a public health dentist at the University of Iowa, found that many of the studies included in the analysis were of very low quality. He too warned against drawing conclusions about any changes should be included in US fluoridation policy.

“A layman or a decision-maker at a water board in a compact community might see the evidence and think that any way of analyzing it raises concerns,” Dr. Levy said in an interview. “It’s not as clear-cut as they’re trying to make it out to be.”

The report’s findings echo some of the statements made by Robert F. Kennedy Jr., President-elect Donald J. Trump’s choice to head the Department of Health and Human Services. He questioned the safety of fluoride and said one of the Trump administration’s first actions would be to recommend that water systems remove fluoride.

Since the practice was introduced in many U.S. communities in the 1950s, criticism of fluoridation has arisen frequently. Initially, however, opposition was rejected because it was strongest among those with extremist or fringe views and right-wing groups such as the John Birch Society, which called fluoridation a communist conspiracy.

This is changing. Last September, U.S. District Judge Edward Chen in San Francisco ordered the Environmental Protection Agency to tighten regulations on fluoride in drinking water because of research suggesting that high levels may pose a threat to children’s intellectual development.

In a second editorial published with the novel study: a public health expert Dr. Bruce P. Lanphearnoted that as early as 1944, the editor of The Journal of the American Dental Association expressed concern about the addition of fluoride to drinking water, which he called “a highly toxic substance.” He wrote that “the potential for harm far outweighs the potential for good.”

Some studies suggest that dental health has improved not by adding fluoride to water, but by fluoridated toothpastes and better oral hygiene practices. (In some countries, fluoride is added to salt.)

According to this argument, topical application of fluoride to the teeth is effective enough to prevent tooth decay and its consumption is not necessary.

But other studies report increase in cavities following the cessation of public water fluoridation initiatives in some countries.

The current recommended fluoride level in the United States is 0.7 parts per million, and the study found no statistically significant inverse relationship between fluoride levels and IQ scores below 1.5 parts per million based solely on water fluoride levels. However, nearly three million Americans still drink water with fluoride levels above 1.5 parts per million from wells and some local water systems.

Linda Birnbaum, former director of the National Institute of Environmental Health Sciences, called for more research into the potential impact of fluoride levels below 1.5 parts per million.

However, she emphasized that the study showed with certainty that a certain amount of fluoride could be harmful to the developing brain. “The answer is quite clear: yes,” Dr. Birnbaum said.

To protect particularly vulnerable fetuses and children, it recommends that parents avoid drinking fluoridated water during pregnancy and employ fluoride-free bottled water when preparing infant formula.

“My recommendation is that pregnant women and infants should not be exposed to excess fluoride,” said Dr. Birnbaum, who is not an author of the novel analysis.

She added that breastfeeding women should not worry because very little fluoride passes into breast milk.

“The more we test for many chemicals, especially those that affect IQ like lead, there really is no unthreatening level,” Dr. Birnbaum said.

About 74 studies were analyzed from 10 countries, including China, Mexico, Canada, India and Denmark. Dr. Lanphear noted that consistent associations between fluoride and IQ have been found in very different populations.

He urged the U.S. Public Health Service to establish a commission, perhaps not composed of researchers who have studied the topic in the past and who can look at it afresh, to seriously examine two questions: whether fluoride is neurotoxic and whether it is so beneficial to oral health as it is believed.

“If this doesn’t happen urgently, I fear the public’s distrust of public health agencies will escalate, and they deserve it,” he said.