HHS report says twice the recommended limit of fluoride is linked to lower IQ in children

A U.S. government report expected to spark debate has found that fluoride in drinking water at amounts twice the recommended limit is linked to lower IQs in children.

The report, based on an analysis of previously published research, marks the first time a federal agency has determined — “with moderate confidence” — that there is a link between higher levels of fluoride exposure and lower IQ in children. While the report was not designed to assess the effects of fluoride in drinking water alone, it is a striking acknowledgement of a potential neurological risk from high levels of fluoride.

According to the U.S. Centers for Disease Control and Prevention, fluoride strengthens teeth and reduces cavities by replacing minerals lost during normal wear and tear. The addition of low levels of fluoride to drinking water has long been considered one of the greatest public health achievements of the past century.

“I think this (report) is crucial to understanding” this risk, said Ashley Malin, a researcher at the University of Florida who has studied the effect of elevated fluoride levels in pregnant women on their children. She called it the most rigorous report of its kind.

The long-awaited report released Wednesday comes from the National Toxicology Program, part of the Department of Health and Human Services. It summarizes a review of studies from Canada, China, India, Iran, Pakistan and Mexico, which concludes that drinking water with more than 1.5 milligrams of fluoride per liter is consistently associated with lower IQ in children.

The report did not attempt to quantify exactly how many IQ points might be lost with different levels of fluoride exposure, but some of the studies analyzed in the report suggested that IQ was 2 to 5 points lower in children who had higher exposures.

Since 2015, federal health officials have recommended a fluoridation level of 0.7 milligrams per liter of water, and for five decades before that, the upper recommended range was 1.2. The World Health Organization has set a safe limit for fluoride in drinking water at 1.5.

The report notes that approximately 0.6% of the U.S. population (about 1.9 million people) use water systems with natural fluoride levels of 1.5 milligrams or more.

“The findings of this report raise questions about how these individuals can be protected and what makes the most sense,” Malin said.

The 324-page report did not reach any conclusions about the risks of low levels of fluoride, saying more studies are needed. It also did not answer what effects high levels of fluoride might have on adults.

The American Dental Association, which advocates for water fluoridation, had criticized earlier versions of the new analysis and Malin’s research. Asked for comment, a spokeswoman on Wednesday afternoon sent an email saying the organization’s experts were still reviewing the report.

Fluoride is a mineral that occurs naturally in water and soil. About 80 years ago, scientists discovered that people who had more fluoride naturally also had fewer cavities, which sparked a campaign to get more Americans to use fluoride for better dental health.

In 1945, Grand Rapids, Michigan, became the first U.S. city to begin adding fluoride to tap water. In 1950, federal officials approved water fluoridation to prevent tooth decay and continued to promote it even after fluoridated toothpaste brands came on the market several years later. Although fluoride can come from a variety of sources, drinking water is the primary source for Americans, researchers say.

Officials lowered their recommendation on fluoride levels in drinking water in 2015 to address a dental condition called fluorosis, which can cause staining of teeth and was becoming more common among American children.

The Environmental Protection Agency, on the other hand, has long maintained a requirement that water systems cannot have more than 4 milligrams of fluoride per liter. That standard is designed to prevent skeletal fluorosis, a potentially disabling disorder that causes weaker bones, stiffness and pain.

But a growing body of research is pointing to a different problem, suggesting a link between elevated fluoride levels and brain development. Researchers wondered about the impact on developing fetuses and very young children who might ingest water laced with infant formula. Animal studies showed that fluoride could affect neurochemical cell function in brain regions responsible for learning, memory, executive function and behavior.

In 2006, the National Research Council, a private nonprofit organization based in Washington, D.C., said limited evidence from China pointed to neurological effects in people exposed to high levels of fluoride. It called for more research into fluoride’s effect on intelligence.

After further research continued to raise questions, in 2016 the National Toxicology Program began work on a review of available studies that could provide guidance on whether further measures were needed to limit fluoride.

There were earlier drafts, but the final document has been repeatedly delayed. At one point, a committee of experts said that available research did not support the conclusions of an earlier draft.

“Since fluoride is such an important issue for the public and public health officials, it was imperative that we do everything we could to get the science right,” Rick Woychik, director of the National Toxicology Program, said in a statement.

Malin said it makes sense for pregnant women to reduce their fluoride intake, not just in water but also in certain types of tea. It might also make sense to have policy discussions to determine whether beverage labels should be required to include fluoride content, she said.

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