Utah could become the first state to ban fluoride in its drinking water, alarming public health experts and dentists who note the mineral’s role in reducing tooth decay across the nation.

The Republican-controlled statehouse sent the legislation to Gov. Spencer Cox (R) last week after both chambers passed it largely along party lines. If signed into law, the bill would prohibit adding fluoride to public water systems and would bar cities and counties from requiring the mineral in their water.

Opponents of the measure argue that it infringes on communities’ right to decide whether to use the cavity-fighting mineral and that it departs from decades of science demonstrating fluoride’s enamel-strengthening, tooth-decay-combating benefits – particularly for children. The bill’s supporters contend that it would prevent the government from medicating the public without its consent.

The governor has not publicly indicated whether he supports the bill, and his office did not immediately respond to request for comment on Tuesday. The Republican governor, who occasionally breaks from party lines, has until the end of March to sign or veto the bill; if he takes no action, it will lapse into law.

Utah’s potentially unprecedented move comes at a time of renewed attention to the practice of adding fluoride to drinking water: Robert F. Kennedy Jr., the newly appointed Health and Human Services secretary, has assailed the practice, alleging that it can harm brain development and bones.

While this isn’t the first time communities have fought over fluoride, which was first used in 1945 in Grand Rapids, Michigan, the issue has historically been hyperlocal, rather than partisan. Democrat-majority states, such as Oregon and New Jersey, have some of the lowest fluoridation rates, while states where Republicans predominate, including Kentucky and South Carolina, boast some of the highest.

Most Americans drink fluoridated water, including about half of Utah residents. The process of adjusting fluoride quantities to recommended levels – known as community water fluoridation – reduces oral health disparities, according to the Centers for Disease Control and Prevention. Most communities that add the mineral do so voluntarily, but about a dozen states require fluoridation. Some of those mandates have been in place for more than 50 years.

In Utah, residents who receive fluoridated water – in Salt Lake County, Davis County and Brigham City – experience tooth decay at rates 25 to 50 percent lower than other residents, according to the Utah Dental Association. The group blasted the bill, urging residents to call Cox’s office to demand a veto.

“House Bill 81 would adopt public policy that is in complete opposition to effectively decreasing dental decay and strengthening teeth enamel,” the group said.

The group’s national counterpart, the American Dental Association, sent a letter to Cox on Tuesday to similarly urge a veto.

“Utah would be the only state to end this preventive health practice that has been in place for over three quarters of a century,” the group wrote. “The Utah measure proposes to take the unprecedented step of ending one of the most trusted and tested public health strategies in the arsenal of preventive medicine.”

Utah Rep. Stephanie Gricius (R), the bill’s sponsor, said the legislation is about choice.

“Community water fluoridation does not allow for informed consent which is a crucial component of good, health-care policy,” she wrote in an email to The Washington Post, adding that she is “hopeful” that Cox will sign the bill, “given the broad support from both legislative bodies.”

Days before the presidential election, Kennedy signalled that a future Trump administration would advise water districts to remove fluoride, which he referred to as “an industrial waste associated with arthritis, bone fractures, bone cancer, IQ loss, neurodevelopmental disorders, and thyroid disease.” Medical organizations said Kennedy’s assertions are unfounded; Trump supported the idea.

The federal government does not mandate fluoridation or directly control local water systems, but experts have said the Trump administration could influence communities across the country to reconsider decades-old fluoridation programs.