Health Secretary Robert F. Kennedy Jr. kicked off a tour through southwestern states Monday by calling on states to ban fluoride in drinking water supplies, a move that would reverse what some medical experts consider one of the most important public health practices in the country’s history.

The announcement came at a news conference in Utah, the first state to enact such a ban into law. The state’s new law is set to take effect in early May, despite concerns from public health experts who consider fluoridation of water core to preventing tooth decay.

“It makes no sense to have it in our water supply,” Kennedy said, echoing a position he took during the 2024 presidential campaign. “I’m very, very proud of this state for being the first state to ban it, and I hope many more will come.”

The Centers for Disease Control and Prevention, which Kennedy oversees as health secretary, has listed fluoridation as one of the 10 great public health achievements of the 20th century. After the news conference, Stefanie Spear, Kennedy’s principal deputy chief of staff, said Kennedy would direct the CDC’s community preventive services task force to study fluoride and make a new recommendation.

Kennedy appeared at the news conference alongside the administrator of the Environmental Protection Agency, Lee Zeldin, who announced that the EPA would reexamine research on potential health risks of fluoride in water. The current standard “was most recently reviewed July of 2024, but a lot has happened since July of 2024,” Zeldin said. The review of safety data “wouldn’t be happening, if not for Secretary Kennedy,” he added.

The fluoridation debate stretches back to the 1950s, when conspiracy theories swirled around whether the practice was a communist plot to cause brain damage. Some studies suggest that excess exposure to fluoride — at levels twice the amount recommended by the federal government — could harm infants.

The American Dental Association has said that water fluoridation reduces dental decay by at least 25% in children and adults.

The Make America Healthy Again tour, which will take Kennedy through parts of Utah, Arizona and New Mexico, was intended to draw attention to some of the secretary’s common-ground interests, spotlighting initiatives that emphasize nutrition and lifestyle choices as tools for combating disease. At the news conference, Kennedy also lauded Utah’s recent legislation to ban ultra-processed foods in school meals and to restrict people from using federal food assistance benefits to purchase candy and soda. He announced late last month that the Trump administration would begin allowing states to bar participants of the Supplemental Nutrition Assistance Program, or SNAP, from using the money to pay for soda.

Kennedy’s first stop on the tour was the Osher Center for Integrative Health at the University of Utah, which prides itself in taking a “whole-person” approach to patient care, including an emphasis on sleep, exercise and even community connection.

Between Kennedy’s events on the campus, about two dozen protesters appeared along the driveway to the center, chanting and waving posters with messages such as “Child Killer” and, in a nod to the Trump administration’s termination of numerous medical research grants, “Research Saves Lives.”

Kennedy has faced harsh criticism for his handling of the federal government’s response to a measles outbreak in West Texas, which has infected nearly 500 people there and has spread to other states.

On Sunday, Kennedy attended the funeral of an unvaccinated 8-year-old girl — the second confirmed fatality from measles in a decade in the United States — and met with her family before continuing to Utah.

Public health experts say the outbreak is driven by low vaccination rates. Kennedy, who is famously skeptical of vaccine safety, shifted his rhetoric after the little girl’s funeral, posting on the social platform X: “The most effective way to prevent the spread of measles is the MMR vaccine.”

It was the most definitive statement he has made endorsing vaccines as a preventive tool, but some public health experts were dismayed that he did not explicitly recommend that parents vaccinate their children and did not say the vaccines were safe. And several hours later he posted on X again, praising two doctors who are using unproven treatments to care for hundreds of children with measles.