What the science actually says about fluoride in drinking water
Public health officials are sparring over conflicting studies weighing the benefits and risks of fluoride, especially for young children. Most everyone agrees it is important for our dental health. The question is how much fluoride we need to protect our teeth without risking possible cognitive harm.
Recent analyses suggest some evidence that high levels of fluoride might harm the brains of children and developing fetuses. Other studies have found no such evidence. And there is no indication that fluoride hurts adult cognition.
The fluoride mineral is part of the Earth’s crust. It exists in all water and in many foods. In much of the country, extra fluoride gets added to public drinking water. It is also in toothpaste and other dental products.
The decision to add fluoride to drinking water is made by local municipalities. Nearly 20 communities across the country have halted the practice, with more discussing it. Many European countries including France and Germany don’t fluoridate drinking water.
You can find the level of fluoride for some communities on the Centers for Disease Control and Prevention website.
Fluoride’s benefitsMost U.S. public health experts and doctors staunchly support adding fluoride to public drinking water to mitigate tooth decay.
Cavities are typically caused by acid that breaks down the enamel of the teeth. Fluoride helps remineralize those areas, making them more resistant to decay.
In Canada, the city of Calgary stopped adding fluoride to its public water in 2011. An April study in the Canadian Journal of Public Health compared Calgary with Edmonton, which continued fluoridation, and found that the rate of general anesthesia for cavity-related treatments was higher in Calgary among more than 2,600 children under age 12 between 2010 and 2019. Children 5 and younger had higher rates than the older children.
“We found that 65% of the children who had general anesthesia lived in nonflouridated areas,” said Maryam Amin, a professor and associate chair of research at the University of Alberta and senior author on the study. Calgary is resuming fluoridation in its public water.
Fluoride applied directly to teeth via toothpaste strengthens tooth enamel and promotes remineralization. Fluoride ingested through water and food gets incorporated into the developing enamel of teeth that haven’t emerged yet, which is why it is especially important for children during their tooth-forming years, Amin says.
Other studies have found more cavities and dental decay in both Calgary and Juneau, Alaska, which ended its community water fluoridation program in 2007.
Fluoride’s possible risksA study last year in the journal Environmental Health linked higher prenatal fluoride exposure to increased neurobehavioral problems, such as anxiety or emotional problems, when children reached age 3.
The study measured urine fluoride levels in pregnant women in Los Angeles County. It found that women whose levels were at the 75th percentile during pregnancy had children nearly twice as likely to exhibit neurobehavioral problems by age 3 than those at the 25th percentile.
The National Toxicology Program assesses potentially toxic chemicals for the government. In August, it released a study concluding with “moderate confidence” that higher levels of fluoride exposure are associated with lower IQ in children—though that wasn’t necessarily the cause. High levels were defined as 1.5 milligrams of fluoride a liter. That equals more than two times the U.S. recommended level of 0.7 milligrams per liter.
The conclusion was based largely on research conducted in other locations—outside of the U.S.—where some pregnant women, infants and children are exposed to higher levels of fluoride.
“There very likely is a level of fluoride much, much higher than what we have in the United States that may cause neurocognitive issues during fetal and early childhood development,” says Dr. Charlotte Lewis, a professor of pediatrics at the University of Washington School of Medicine in Seattle. But there is no strong evidence that is happening with the levels of fluoride in public drinking water in the U.S., she says.
What to doParents worried about potential risks to children can take a few steps.
Pregnant women who want to limit their fluoride exposure can look for bottled water labeled as deionized, purified, demineralized or distilled, without any fluoride added after purification treatment, says Kyla Taylor, a health scientist at the National Institute of Environmental Health Sciences and co-author of the National Toxicology Program study.
Water filters in refrigerators typically don’t filter out fluoride. A filter needs a reverse-osmosis step to remove most fluoride. You can buy reverse-osmosis filtration systems at such places as Home Depot.
The CDC recommends children use fluoride toothpaste starting at age 2. To avoid accidental ingestion, children younger than 6 should use no more than a pea-size amount of toothpaste. For pregnant women, using toothpaste with fluoride should be safe for the fetus, says Ashley J. Malin, an assistant professor in the department of epidemiology at the University of Florida and author of the study linking fluoride to neurobehavioral problems.
Other scientists say concern about fluoridated water in the U.S. is misguided.
Lewis, the University of Washington pediatrics professor, says infants’ teeth are mineralizing in the jaw even when they aren’t yet visible. So exposure to fluoride affects how the teeth eventually develop, making them stronger and more resistant to cavities.
“Everyone benefits from fluoride at the level that we have in U.S. community water fluoridation,” she says. That includes pregnant women and infants.
