A look at the risks and benefits of water fluoridation

Utah has now banned fluoride from the water supply and will no longer add it. Hawaii has never added it to its public water, while other states mandate its addition. In most of the country, adding fluoride to water to prevent cavities has been a patchwork decided by cities and municipalities, where sometimes cities or states sitting side by side made different decisions.

About three-fourths of the U.S. population have been getting water with extra fluoridation.

Meanwhile, many Western European countries no longer fluoridate public water after years of doing so.

Adding fluoride to water has long been controversial and is hot again, fueled in part by appointment of Robert F. Kennedy Jr., a fluoridation opponent, as U.S. secretary of Health and Human Services.

And the science, it seems, is not as settled as either critics or supporters would like folks to believe.

Last November, Deseret News took a deep dive into the science of fluoridation. Today, we’re looking again to see what’s known and what questions remain about fluoride and its potential risks and benefits when added to municipal water supplies.

What is fluoride?

Fluoride is a mineral that occurs naturally in water, soil and certain foods. It’s the 13th most common element in the Earth’s crust, so there’s no shortage of it.

It was first added to drinking water in 1945 in Grand Rapids, Michigan, where the rate of cavities among children dropped. In 1950, other communities began adding fluoride to public drinking water supplies. By the mid-60s, many toothpaste and mouthwash manufacturers were also adding fluoride to products. One now must peruse the drug store shelf’s ingredients carefully to avoid the addition.

The benefit of fluoride to oral health derives from the fact it resists cavity-causing acids produced by mouth bacteria. Fluoride strengthens tooth enamel by forming a mineral called fluorapatite. It also has the ability to remineralize teeth that have been damaged by the acids, reducing risk of cavities.

The Centers for Disease Control and Prevention doesn’t mandate community water fluoridation, nor does it set safe levels. That’s done by the U.S. Public Health Service. And the level is not a mandate either. Nor is it enforceable.

The CDC lists fluoridation of drinking water among the 10 great public health interventions of the 20th century.

How much is too much?

No one questions that the mineral in the mouth hardens enamel and reduces the effect of acid in saliva. That’s been shown by numerous studies. “In a systematic review of 20 studies published in 2007, scientists reported that water fluoridation was associated with a 27% decline in cavities among adults, and a 2018 study found that it led to a 30% reduction among children,” per The New York Times.

But even in the mouth, fluoride can cause problems. Too much can cause dental fluorosis, which leaves white spots on the teeth. That’s why children are told not to use more than a pea-sized amount of toothpaste to which fluoride has been added and parents are told to make sure smaller children know to spit it out. Children under 6 are more likely to swallow toothpaste, instead, so parents are told to be vigilant if using fluoridated toothpaste.

About 40% of adolescents are estimated to have some spottiness on their teeth, according to the Associated Press. It’s considered a cosmetic issue that doesn’t affect tooth strength or function.

The Cleveland Clinic notes that “while fluoride can be harmful in large quantities, it’s difficult to reach toxic levels due to the low amount of fluoride in over-the-counter products like toothpaste and mouth rinses.”

Besides toothpaste and mouthwash, a dentist can apply fluoride in the form of foam, varnish or a gel. In Utah, which just banned adding fluoride to the water supply, fluoride is also available without prescription from pharmacies.

The fact that so many products for teeth and oral health contain fluoride, however, is one reason that opponents of adding the mineral to municipal water argue it’s not needed. The benefits can be gained in other ways, without incurring any of the risks.

And as Washington Post columnist and contributor Dr. Leana S. Wen recently wrote, with so many products available, it’s not clear how much benefit fluoridated water provides now. Wen also noted that while she disagrees with many of Kennedy’s ideas on health, she thinks questioning fluoride isn’t such a bad idea. She said she was a proponent of fluoridation who is no longer so sure.

Per the earlier Deseret News article, “KFF Health News quoted David Bellinger, a Harvard Medical School neurology professor and professor in the Harvard School of Public Health’s Environmental Health Department, said the calculation of benefit and risk would be different depending on the amount of fluoride and whether typical exposure levels lead to the concerning conditions or if that only happens when exposure levels are higher.

“In toxicology, ‘the dose makes the poison’ is a long-standing principle,” he said. “So a general statement that fluoride is associated with diseases X, Y and Z is not very helpful unless the dose that might be responsible is specified.”

The National Institutes of Health says getting too much fluoride, outside of a rare accident, is unlikely. As AP reported, NIH calls it “virtually impossible” to get a toxic dose from fluoride added to water at appropriate levels.

Appropriate levels is key. In 2019, a power surge in Sandy, Utah, led to a high level of fluoride in drinking water. As Deseret News reported, “fluoride was detected at 40 times the federal limit after the release, and two weeks of free blood testing for lead showed one person with elevated levels, according to Salt Lake County health officials.”

And per AP, “Florida’s surgeon general last year recommended against community water fluoridation because of what he called its ‘neuropsychiatric risk.’ That guidance came after a federal judge ordered the U.S. Environmental Protection Agency to regulate fluoride in drinking water because high levels could pose a risk to the intellectual development of children.”

Dueling studies, positions

Kennedy has called fluoride “an industrial waste associated with arthritis, bone fractures, bone cancer, IQ loss, neurodevelopmental disorders and thyroid disease,” as well as a neurotoxin. Critics of his assertion say the amount of fluoride added to water doesn’t approach the level that would be needed to create the assorted risks mentioned.

Besides tooth discoloration, higher levels of fluoride have been tied to bone and thyroid problems. Consequently, as Deseret News earlier reported, the U.S. Public Health Service lowered the levels of fluoride that could be added to drinking water back in 2015.

The National Toxicology Program did a systematic review of published studies on a link between fluoride exposure and brain development and cognition and published a program monograph on the topic.

The program monograph concluded “with moderate confidence that higher levels of fluoride exposure, such as drinking water containing more than 1.5 milligrams of fluoride per liter, are associated with lower IQ in children.” It said the review was designed to look at total fluoride exposure from all sources “and was not designed to evaluate the health effects of fluoridated drinking water alone.”

In bolded text, the study emphasized that “it is important to note that there were insufficient data to determine if the low fluoride level of 0.7 mg/L currently recommended for U.S. community water supplies has a negative effect on children’s IQ.”

Study critics note that the level studied that led to the finding is twice that of the recommended amount to be added to water.

A number of professional organizations, including the American Dental Association and the American Academy of Pediatrics responded by reaffirming their support for added fluoridation of water. And one of the academy’s Section on Oral Health, Dr. Charlotte W. Lewis, said the review ignored large population-based studies that did not link fluoride to children’s brain development.

A study published in JAMA Network Open considered 229 mother-child pairs in Los Angeles and looked at maternal urinary fluoride in the third trimester, an accepted marker of fluoridation intake, then compared it with the child’s behavior at 3 years old, finding prenatal fluoride exposure was linked to increased neurobehavioral problems. The study authors wrote that findings “suggest that there may be a need to establish recommendations for limiting fluoride exposure during the prenatal period.”

As the Post reported, “This study, which was funded in part by the National Institutes of Health and the Environmental Protection Agency, generated significant controversy. Anti-fluoridation groups seized upon it to justify their crusade, while organizations such as the American Dental Association issued statements doubling down on the benefits of water fluoridation.”

Many agree, however, that fluoride might be risky for women who are pregnant, as it may impact the brain development of the babies they are carrying. And some have expressed concern about the impact on babies whose formula is made with fluoridated water.

A study on children’s IQ conducted alongside the work by the authors of the monograph was published in JAMA Pediatrics study in January.

The pediatric study of Canadian women concluded that those who drank fluoridated water while pregnant had children who at age 3 to 4 years old had kids with lower IQ, though the effect on girls was not statistically significant. For boys, the IQ scores for those whose mothers had higher fluoride consumption was 4.5 points lower on average.

The dental association said Utah’s new law banning fluoridation shows “wanton disregard for the oral health and well-being of their constituents,” according to the Associated Press.

Others remain staunch in support of adding fluoride for the sake of teeth.

Joe Schwarcz, professor and director of the McGill Office for Science and Society at McGill University in Quebec, dismisses most of the claims about bone cancer and weakened bones, but acknowledges that fluorosis is a real concern. He said some people are getting more fluoride than needed because it’s also added to toothpastes, mouth washes and can show up in foods because it is added to water.

“The other claims against fluoridation are much more nebulous. While laboratory studies and some animal experiments suggest that fluoride can trigger cancer, extensive epidemiological investigations in fluoridated and non-fluoridated communities have shown no difference in cancer rates,” he wrote.

Schwarcz said that while fluoride can incorporate into the bones, not just teeth, the claim is that it weakens bones. “Again, epidemiological studies have shown that if there is a risk of increased fractures, it is a very small one. Fluoride does interfere with enzyme systems; after all that is the way it controls bacteria in the mouth. In theory then, it can have a negative effect on various body functions. But theory is not the same as evidence.”

He, too, notes that fluoride can be toxic and has even been used to poison rats. But he counters that dose determines toxicity and context matters, adding that chlorine, which is used to clean water, at high dose becomes a chemical weapon, for example.

What are states and cities doing?

AP reported last week on Utah’s ban, noting that of Utah’s 484 water systems reporting data in 2024, only 66 added fluoride to their water. The biggest one that did is Salt Lake City. The article said that Florida, Ohio and South Carolina are considering banning adding fluoride to drinking water, while New Hampshire, North Dakota and Tennessee rejected similar proposals. A Kentucky bill that would have made fluoridation optional stalled in that state Senate.

Portland, Oregon, is among cities that have never added fluoride, while Sheridan, Wyoming, recently started adding it.

It’s still a national patchwork of responses that seems to be in flux.