麻豆传媒

Skip to main content

Fluoride at twice the recommended limit is linked to lower IQ in kids, U.S. report says

Water flows from a water fountain in Concord, N.H., on Friday, Jan. 7, 2011. (AP Photo/Jim Cole, File) Water flows from a water fountain in Concord, N.H., on Friday, Jan. 7, 2011. (AP Photo/Jim Cole, File)
Share
NEW YORK -

A U.S. government report expected to stir debate concluded that fluoride in drinking water at twice the recommended limit is linked with lower IQ in children.

The report, based on an analysis of previously published research, marks the first time a federal agency has determined 鈥 鈥渨ith moderate confidence鈥 鈥 that there is a link between higher levels of fluoride exposure and lower IQ in kids. While the report was not designed to evaluate 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 wear and tear, according to the U.S. Centers for Disease Control and Prevention. The addition of low levels of fluoride to drinking water has long been considered one of the greatest public health achievements of the last century.

鈥淚 think this (report) is crucial in our understanding鈥 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 rigorously conducted 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, conducted in Canada, China, India, Iran, Pakistan, and Mexico, that concludes that drinking water containing more than 1.5 milligrams of fluoride per liter is consistently associated with lower IQs in kids.

The report did not try to quantify exactly how many IQ points might be lost at different levels of fluoride exposure. But some of the studies reviewed in the report suggested IQ was 2 to 5 points lower in children who'd had higher exposures.

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

The report said that about 0.6% of the U.S. population 鈥 about 1.9 million people 鈥 are on water systems with naturally occurring fluoride levels of 1.5 milligrams or higher.

鈥淭he findings from this report raise the questions about how these people can be protected and what makes the most sense,鈥 Malin said.

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

The American Dental Association, which champions water fluoridation, had been critical of earlier versions of the new analysis and Malin鈥檚 research. Asked for comment, a spokeswoman late Wednesday afternoon emailed that the organization鈥檚 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 naturally had more fluoride also had fewer cavities, triggering a push to get more Americans to use fluoride for better dental health.

In 1945, Grand Rapids, Michigan became the first U.S. city to start adding fluoride to tap water. In 1950, federal officials endorsed water fluoridation to prevent tooth decay, and continued to promote it even after fluoride toothpaste brands hit the market several years later. Though fluoride can come from a number of sources, drinking water is the main source for Americans, researchers say.

Officials lowered their recommendation for drinking water fluoride levels in 2015 to address a tooth condition called fluorosis, which can cause splotches on teeth and was becoming more common in U.S. kids.

Separately, the Environmental Protection Agency has maintained a longstanding requirement that water systems cannot have more than 4 milligrams of fluoride per litre. That standard is designed to prevent skeletal fluorosis, a potentially crippling disorder which causes weaker bones, stiffness and pain.

But more and more studies have increasingly pointed to a different problem, suggesting a link between higher levels of fluoride and brain development. Researchers wondered about the impact on developing fetuses and very young children who might ingest water with baby formula. Studies in animals showed fluoride could impact neurochemistry cell function in brain regions responsible for learning, memory, executive function and behaviour.

In 2006, the National Research Council, a private nonprofit organization 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 the effect of fluoride on intelligence.

After more research continued to raise questions, the National Toxicology Program in 2016 started working on a review of the available studies that could provide guidance on whether new fluoride-limiting measures were needed.

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

鈥淪ince fluoride is such an important topic to the public and to public health officials, it was imperative that we made every effort to get the science right,鈥 said Rick Woychik, director of the National Toxicology Program, 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.

___

The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute鈥檚 Science and Educational Media Group. The AP is solely responsible for all content.

CTVNews.ca Top Stories

The sentencing of the man who pleaded guilty in the deadly hit-and-run in Kitsilano two years ago began on Friday.

The two people who died in a major fire in Old Montreal on Friday were a mother and her seven-year-old daughter, sources told Noovo Info.

New data shows the automated speed enforcement camera on King Edward Avenue, between Bolton Street and St. Patrick Street, issued 6,337 speeding tickets in August, the highest number of tickets issued by Ottawa's 40 photo radar cameras.

Montreal police say a business in the city's Pointe-Saint-Charles neighbourhood was hit with Molotov cocktails two nights in a row.

Ontario Provincial Police have laid stunt charges against a driver caught speeding 75 km/h over the speed limit on Highway 417 in Ottawa's west end.

Local Spotlight

Chantal Kreviazuk is set to return to Winnipeg to mark a major milestone in her illustrious musical career.

From the beaches of Cannes to the bustling streets of New York City, a new film by a trio of Manitoba directors has toured the international film festival circuit to much pomp and circumstance.

A husband and wife have been on the road trip of a lifetime and have decided to stop in Saskatchewan for the winter.

The grave of a previously unknown Canadian soldier has been identified as a man from Hayfield, Man. who fought in the First World War.

A group of classic car enthusiasts donated hundreds of blankets to nursing homes in Nova Scotia.

Moving into the second week of October, the eastern half of Canada can expect some brisker fall air to break down from the north

What does New Westminster's t蓹m蓹sew虛tx史 Aquatic and Community Centre have in common with a historic 68,000-seat stadium in Beijing, an NFL stadium and the aquatics venue for the Paris Olympics? They've all been named among the world's most beautiful sports venues for 2024.

The last living member of the legendary Vancouver Asahi baseball team, Kaye Kaminishi, died on Saturday, Sept. 28, surrounded by family. He was 102 years old.

New data from Greater Vancouver and the Fraser Valley shows a surge in supply and drop in demand in the region's historically hot real estate market.