Fluoride -- long heralded as one of the greatest public health achievements of the 20th century -- could be removed from public water systems under the influence of one of President-elect Donald Trump's advisers, Robert F. Kennedy Jr.
Kennedy -- who has no training in either medicine or dentistry -- called fluoride "an industrial waste associated with arthritis, bone fractures, bone cancer, IQ loss" and other problems on the social media platform X.
"I think fluoride is on the way out," Kennedy said Wednesday on MSNBC. "The faster that it goes out, the better."
Whether to add fluoride to water supplies is decided and funded by local jurisdictions, not the federal government. Still, Kennedy said that if tapped, he would advise communities on fluoridated water.
Dentists who care for kids' oral health say the end of fluoridated drinking water would be detrimental.
"It won't happen right away, but as children continue to grow and develop, they will have an increased cavity rate," said Dr. Meg Lochary, a pediatric dentist in Waxhaw, North Carolina, an area that recently opted out of adding fluoride to water systems. "We will eventually see an increase in tooth decay."
According to the Centers for Disease Control and Prevention, fluoride exposure through municipal water supplies is especially important for families who don't have dental care.
While an estimated 75% of Americans have fluoridated drinking water, hundreds of U.S. communities are increasingly opting out of water fluoridation.
Caught in the middle are parents trying to make sense of widely differing views on added fluoride. Is it good? Is it bad? Let's break it down.
Mouths teem with bacteria, which produce acid in saliva. Those acids weaken teeth and lead to decay. Fluoride counters that process with a one-two punch, by reducing acid and strengthening enamel, the tooth's protective outer layer.
The phenomenon was discovered in the early 1900s among residents of Colorado Springs, Colorado. Tooth decay was nearly nonexistent in the population. The only thing to explain it was their drinking water, which was naturally high in fluoride that leached from local rocks and soil.
Grand Rapids, Michigan, became the first community in the world to add fluoride to its water supply in 1945. Within a decade, cavities among young children in the town plummeted by 60%. Other public water systems followed.
Major public health groups, including the American Dental Association, the American Academy of Pediatrics and the CDC, soon supported the use of fluoridated water. All cite studies that show it reduces tooth decay by 25%.
Cavity prevention, experts say, is a major public health coup. Uncontrolled tooth decay can lead to infections, loss of teeth and painful abscesses.
Despite decades of study and real-world evidence of its benefits, fluoride continues to be scrutinized.
To date, there's no damning evidence proving that fluoridated water leads to any of the outcomes Kennedy mentioned, including loss of intellect.
"There's not any evidence that fluoride has lowered the IQ of kids," said Dr. David Margolius, Cleveland's director of public health.
There are some small studies, however, worth mentioning.
Research published in May suggested that fluoride exposure during pregnancy could be linked to neurobehavioral issues in kids. The study's authors, however, said that based on the findings, it's premature to stop adding the cavity-fighting mineral to drinking water.
A 2019 study, published in JAMA Pediatrics, found that IQ levels were slightly lower in 3- and 4-year-old children whose mothers had higher measures of fluoride in their urine when they were pregnant.
While the researchers said it may be time to "hit pause" on water fluoridation, they stopped short of saying the mineral should be pulled from water supplies.
In September, a federal judge in California ruled that even though he couldn't conclude with certainty that fluoridated water was a danger to public health, the U.S. Environmental Protection Agency should strengthen water fluoridation regulations.
Experts maintain that there's no credible evidence proving fluoride has lowered kids' IQ levels.
With science in mind, parents should be able to ask questions about what their kids are consuming, said Dr. Richard Besser, former acting CDC director and current president of the Robert Wood Johnson Foundation.
"Any parent should feel very comfortable asking their child's doctor, 'What should be my approach to fluoride to protect my child's teeth?'" Besser said. "Those are appropriate questions, but saying that fluoride doesn't have value flies in the face of the science and evidence."