Fluoride in drinking water at twice recommended limit linked to lower IQ in children: US government report

NEW YORK – A US government report expected to fuel debate concluded that fluoride in drinking water at twice the recommended limit is linked to lower IQ 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 health effects of fluoride in drinking water alone, it is a striking acknowledgment of a potential neurological risk from high levels of fluoride.

Fluoride strengthens teeth and reduces cavities by replacing minerals lost during normal consumption, according to the US Centers for Disease Control and Prevention. Adding 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 fundamental in our understanding” of this risk, said Ashley Malin, a University of Florida researcher who has studied the effect of higher 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 studies, conducted in Canada, China, India, Iran, Pakistan and Mexico, which conclude that drinking water containing more than 1.5 milligrams of fluoride per liter is consistently associated with lower IQ in children.

The report did not attempt to determine exactly how many IQ points could be lost at different levels of fluoride exposure. But some of the studies reviewed in the report suggested that IQ was 2 to 5 points lower in children who had higher exposures.

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

The report said about 0.6% of the US population — about 1.9 million people — are in water systems with naturally occurring fluoride levels of 1.5 milligrams or higher.

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

The 324-page report did not reach a conclusion about the risks of lower fluoride levels, saying more study is needed. It also did not answer what high levels of fluoride can do to adults.

The American Dental Association, which supports water fluoridation, had been critical of earlier versions of the new analysis and Malin’s research. Asked for comment, a spokeswoman late Wednesday afternoon emailed that the organization’s experts were still reviewing the report.

Fluoride is a mineral that exists naturally in water and soil. About 80 years ago, scientists discovered that people whose supplies had more fluoride also had fewer cavities, sparking a push to get more Americans to use fluoride for better dental health.

In 1945, Grand Rapids, Michigan became the first American city to begin adding fluoride to its tap water. In 1950, federal officials approved water fluoridation to prevent tooth decay and continued to promote it even after brands of fluoride toothpaste hit the market a few 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 for drinking water fluoride levels in 2015 to treat a dental condition called fluorosis, which can cause staining of teeth and was becoming more common among American children.

Separately, the Environmental Protection Agency has long maintained a requirement that water systems can have no more than 4 milligrams of fluoride per liter. This standard is designed to prevent skeletal fluorosis, a potentially crippling disorder that causes weaker bones, stiffness and pain.

But more and more studies have increasingly pointed to another problem, suggesting a link between higher fluoride levels and brain development. Researchers wondered about the impact on developing fetuses and very young children who may drink water with infant formula. Animal studies have shown that fluoride can affect the function of neurochemical cells in brain regions responsible for learning, memory, executive function and behavior.

In 2006, the National Research Council, a private nonprofit organization in Washington, DC, said that limited evidence from China showed neurological effects in people exposed to high levels of fluoride. He called for more research into the effect of fluoride on intelligence.

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

There were earlier drafts, but the final document was kept iteratively. At one point, an expert committee said available research did not support the conclusions of an earlier draft.

“Because fluoride is such an important topic to the public and to public health officials, it was imperative that we make every effort 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 lower their fluoride intake, not only from water, but also from certain types of tea. It might also make sense to have policy discussions about whether to require fluoride content on beverage labels, she said.