The science behind fluoride in drinking water

IIf Donald Trump is elected for a second term, his presidency could threaten what is hailed as one of those the greatest public health triumphs of the 20th century: adding fluoride, a mineral that helps prevent cavities, to drinking water.

This is due to Robert F. Kennedy Jr.the notorious vaccine skeptic, like Trump have said will play a major role in health care in his administration if elected. “On January 20, the Trump White House will advise all US water systems to remove fluoride from public water,” Kennedy recently wrote X. (Trump, i an interview with NBC Newssaid Kennedy’s proposal “sounds OK.”)

Adding fluoride to drinking water reduces the number of cavities by about 25%, US Centers for Disease Control and Prevention (CDC) says. Some American communities began to do so in The 1940sand today about 72% of the US population receiving water from public supplies drinks fluoridated water, According to the CDC. Decisions about whether to use fluoride are typically made at the state or local level, and at least a dozen states require large municipalities to do so, Stateline reports.

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People in countries including Australia and Canada also consume fluoride in drinking water. A 2021 study demonstrated that children living in Calgary, a Canadian city that stopped fluoridating its water, developed significantly more cavities than children living in nearby Edmonton, which actually uses fluoride.

Despite fluoride’s long-standing, federally celebrated presence in American drinking water, Kennedy is not alone in opposing its use. Anti-fluoridation advocates have for decades called for the mineral to be removed from water supplies, and a number of communities, including Portland, Ore., Juneau, Alaska, and Wichita, Kans., have decided not to add fluoride to their water.

Why all the controversy about a naturally occurring mineral that has been shown to improve oral health?

Although fluoride has shown benefits, namely i reduces the risk of tooth decay and cavitiessome studies have also raised questions about its potential link to health problems ranging from cancer to osteoporosis. CDC maintains that there is no convincing evidence linking fluoride to “any potential adverse health effect or systemic disorder” and other major health groups including American Cancer Society and that American Dental Association (ADA), agrees that it is safe. But concerns remain — particularly about the links between fluoride and cognition.

In August, the US National Toxicology Program (NTP) published a report that found with “moderate confidence” that—at concentrations more than twice the recommended fluoride level in the United States—fluoridated water is associated with modestly lower IQ scores in children. US standards recommend fluoride levels of 0.7 milligrams per liter of water, and the NTP’s conclusion applies to water fluoridated at 1.5 milligrams per liter and above.

Preliminary draft of the report failed to clear independent review by the National Academies of Science, Engineering and Medicine, which found that the NTP’s authors had not adequately supported their conclusions with data. Some pro-fluoride organizations, including the ADA, argue that the final version still lacks conclusive evidence and should not lead to policy changes around water treatment.

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Tewodros Godebo, an assistant professor at Tulane University’s Celia Scott Weatherhead School of Public Health and Tropical Medicine who studies fluoridesays studies of very high levels of fluoride exposure don’t necessarily apply to the United States, where water typically contains much less of the mineral.

Still, it’s notable that even government researchers disagree about the safety of fluoridated water, says Christine Till, a professor at Canada’s York University whose research has shown a link between fluoride and lower IQ scores in children. “One authoritative group (CDC) says it’s safe for everyone, and another US government expert group (NTP) says there are concerns about negative effects of fluoride intake on children’s development,” Till says. “At the very least, it’s time to acknowledge the evolving science.”

A federal judge in California waded into that debate earlier this year when he ruled that the US Environmental Protection Agency must strengthen regulations on fluoride to address its potential risk to children’s cognitive development. This decision doesn’t necessarily mean removing fluoride from American drinking water — the EPA could choose to address the situation in a number of ways, including issuing a public notice about the mineral’s potential risks and benefits — but it does highlight growing scrutiny of the practice of fluoridating water , which some anti-fluoride activists argue is no longer necessary now that most people can choose to use fluoride in dental products such as toothpaste. (Till says it’s important to analyze total fluoride exposure, not just exposure through drinking water, when analyzing the mineral’s potential risks and benefits.)

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ONE 2024 Cochrane review article found that adding fluoride to drinking water may lead to slightly fewer cavities among children, but concluded that the effects of the practice are less dramatic today than they were before fluoride was commonly found in toothpaste. The authors also noted that adding fluoride to drinking water may increase the number of people with dental fluorosisa mainly cosmetic condition that can leave the teeth with white spots, stains or lines.

However, fluoridated water helps protect people who may not keep up with oral hygiene or have access to regular dental care, Godebo says — another factor that complicates any discussion about potentially adjusting levels of fluoride in U.S. water.

Despite Kennedy’s suggestion that removing fluoride would be a Day-1 priority in a potential Trump administration, Godebo says “the science isn’t there” to change U.S. recommendations at this point. “It would be a huge decision,” he says. “It should take several years to reach a conclusion.”