Utah has become the first U.S. state to outlaw the addition of fluoride to public drinking water.
The law, which was signed by Gov. Spencer Cox on March 27 and will go into effect on May 7, comes amid renewed scrutiny of fluoride, a mineral that has been widely added to U.S. drinking water since 1945 to prevent cavities. Although controversy over the safety of water fluoridation first arose in the 1940s, concerns have intensified in recent years, driven in part by new research on fluoridation and by growing resistance to public health interventions since the pandemic.
In November, Robert F. Kennedy Jr., now the federal health secretary, said that the Trump administration would “advise all U.S. water systems to remove fluoride from public water” because of potential health risks. Anti-fluoridation bills have also been introduced in North Dakota, Tennessee and Montana.
Much of the concern centers on the possible cognitive effects in children. In one recent review of studies, researchers concluded that high levels of prenatal or childhood fluoride exposure were linked with lower I.Q. s in childhood. But the fluoride levels associated with cognitive problems were more than twice as high as the levels people are generally exposed to through community water fluoridation, said Dr. Scott Tomar, a public health dentist and oral epidemiologist at the University of Illinois Chicago.
Some Americans are exposed to high levels of fluoride in their water through natural contamination from rocks and soil, he said, but not from manual fluoridation. The risks of manual fluoridation “have been dramatically overstated,” Dr. Tomar said.
Gov. Cox has not publicly alluded to health concerns relating to fluoridation, and the bill does not mention any either. He instead has previously said that the oral health benefits of water fluoridation have been insubstantial in Utah, where about 44 percent of residents who were provided with public drinking water consumed fluoridated water in 2022.
Nearly half of the state has been drinking fluoridated water, while the other half has not. Between those two groups, Gov. Cox said, “you think you would see drastically different outcomes. We haven’t.”
However, that claim runs counter to published research, which suggests that fluoridation does improve oral health. The mineral hardens the outer surface of teeth and may also reduce the amount of enamel-eroding acid that bacteria on the teeth produce. In a systematic review of 20 studies published in 2007, scientists reported that water fluoridation was associated with a 27 percent decline in cavities among adults, and a 2018 study found that it led to a 30 percent reduction among children.
“We have strong evidence that it works,” said Dr. F. Perry Wilson, a physician and chronic disease epidemiologist at the Yale School of Medicine.
Dr. Tomar said he was concerned that the Utah law and other potential bans could lead to more oral health problems throughout the country, especially in poorer areas.
“The benefits of community water fluoridation are most pronounced in low income communities — communities that often have the least access to dental care and to other sources of fluoride,” Dr. Tomar said. Fluoride bans, he added, are “misguided on a number of levels.”