Higher fluoride content in drinking water leads to lower IQ in children, study shows
By Mike Stobbe
Higher fluoride content in drinking water leads to lower IQ in children, study shows
new York – A US government report expected for debate concluded that fluoride levels in drinking water twice the recommended limit are associated with lower IQ in children.
The report, based on an analysis of previously published research, is the first time a federal agency has found — “with moderate certainty” — that there is a link between higher fluoride exposure and lower IQ in children. Although the report was not designed to exclusively evaluate the health effects of fluoride in drinking water, it is a notable acknowledgment of a potential neurological risk from high fluoride levels.
Fluoride strengthens teeth and reduces tooth decay by replacing minerals lost through normal wear and tear, according to the U.S. Centers for Disease Control and Prevention. Adding small amounts of fluoride to drinking water has long been considered one of the greatest public health achievements of the last century.
“I think this (report) is critical to our understanding” of that risk, said Ashley Malin, a researcher at the University of Florida who has studied the effects of higher fluoride levels in pregnant women on their children. She called it the most thoroughly conducted report of its kind.
The highly anticipated report, released Wednesday, comes from the National Toxicology Program under the Department of Health and Human Services. It summarizes a review of studies conducted in Canada, China, India, Iran, Pakistan and Mexico. They conclude that drinking water with fluoride levels greater than 1.5 milligrams 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 examined in the report suggested that IQ was 2 to 5 points lower in children exposed to higher levels of fluoride.
Since 2015, federal health authorities have recommended a fluoridation level of 0.7 milligrams per liter of water. Five decades earlier, the recommended maximum level was 1.2. The World Health Organization has set a safe limit for fluoride in drinking water at 1.5.
According to the report, about 0.6 percent of the U.S. population — about 1.9 million people — are connected to water systems that have natural fluoride levels of 1.5 milligrams or more.
“The findings of this report raise the question of how these people can be protected and what makes the most sense,” said Malin.
The 324-page report did not reach a conclusion about the risks of low fluoride levels, saying that more studies were needed. It also did not answer what consequences high fluoride levels might have for adults.
The American Dental Association, which advocates water fluoridation, had criticized earlier versions of the new analysis and Malin’s research. Reached for comment late Wednesday afternoon, a spokeswoman wrote by email that 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 whose teeth naturally contained more fluoride also had fewer cavities. This sparked a movement to get more Americans to use fluoride for better dental health.
(In 1945, Grand Rapids, Michigan, became the first city in the United States to add fluoride to tap water. In 1950, federal authorities recommended water fluoridation to prevent tooth decay and continued to do so even after fluoridated toothpaste came onto the market a few years later. Although fluoride can come from a variety of sources, researchers say drinking water is the main source for Americans
In 2015, regulators lowered their recommendation for fluoride levels in drinking water to combat a dental disease called fluorosis, which can cause stains on teeth and is becoming increasingly common among children in the United States.
Separately, the Environmental Protection Agency has long maintained a requirement that water systems contain no more than 4 milligrams of fluoride per liter. This limit is intended to prevent skeletal fluorosis, a potentially debilitating disease that causes weaker bones, stiffness and pain.
But a growing number of studies pointed to another problem: a link between higher fluoride levels and brain development. Researchers wondered what effect fluoride might have on developing fetuses and infants who drink water with baby formula. Animal studies showed that fluoride can affect neurochemical cell function in brain regions responsible for learning, memory, executive functions and behavior.
In 2006, the National Research Council, a private nonprofit organization in Washington, DC, stated that there was limited evidence in China to indicate neurological effects in people exposed to high levels of fluoride. It called for further research into the effects of fluoride on intelligence.
After further research continued to raise questions, in 2016 the National Toxicology Program began evaluating available studies that could provide clues as to whether new measures to limit fluoride levels are needed.
There were earlier drafts, but the final document was repeatedly held up. At one point, a panel of experts said that the available research did not support the conclusions of an earlier draft.
“Because fluoride is such an important issue for the public and health authorities, it was imperative that we make every effort to accurately present the science,” 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 from water but also from certain types of tea. It may also make sense to have policy discussions about whether to mandate fluoride content on beverage labels, she said.
