In the early 1900s, public health officials concluded discolored teeth among residents of Colorado Springs were caused by high levels of naturally occurring fluoride in the spring water. However, the residents also had lower rates of tooth decay. Health experts determined that adding low levels of fluoride to drinking water could prevent cavities with little side effects.

Towns and cities across the U.S. began fluoridating their water, following Grand Rapids, Mich., in 1945. In a few years, health officials documented a 60% reduction in tooth decay.

Since then, numerous studies have shown fluoride can reduce cavities because it strengthens enamel during the formation of teeth, and it can remineralize adult teeth.

Conspiracy theories about fluoride have been around since the beginning. However, the anti-fluoride movement was amplified in recent months as President Donald Trump’s Health and Human Services secretary nominee, Robert F. Kennedy Jr. called for removing fluoride from public drinking water. Kennedy has alleged the chemical can cause health problems such as bone cancer and neurodevelopmental disorders.

During his confirmation hearing this week, he referenced a recent study that found an association between fluoride and lowered I.Q. Researchers have cautioned none of the study’s analyses were conducted in the United States, where recommended fluoridation levels in drinking water are very low.

Exposure to high levels of the chemical could impact a person’s health, said Dr. Mary Beth Giacona, a professor of pediatric dentistry at Rutgers School of Dental Medicine. However, she said there are no health effects associated with the very low levels of fluoride found in drinking water in the U.S.

“I think the evidence is there to say that at the levels that we are fluoridating our water supplies, it does not cause harm,” Giacona said.

Last year, another study linked fluoridated water during pregnancy and increased neurobehavioral problems in children. One of the study’s authors, Howard Hu, has since advocated for some policy changes, such as limiting fluoride exposure during pregnancy and the first year of a child’s life.

“As a precaution, I think women during pregnancy should try to limit their known exposures to sources of fluoride,” said Hu, a professor of preventive medicine at the University of Southern California,

Some opponents of fluoridated water believe toothpaste, mouth rinses and professional treatments are a safer alternative. However, dentists argue fluoridated water ensures everyone has access.

“There are large segments of our population that cannot afford to and don’t have access to other interventions,” Giacona said. “Whereas, if you fluoridate a community’s water supply, everybody, no matter what the household income is, no matter what race or religion or ethnicity they are, has access to this effective preventive measure.”

Velazquez expressed concern that warnings about fluoride in drinking water might also reduce the use of fluoridated dental products in New Jersey.

“They hear … someone’s telling [them] fluoride is not good, then they stop everything,” she said.

Velazquez encourages people to discuss best dental practices with their providers.

“There’s so many factors, and that’s not something that should just be Googled,” she said. “That should be something that each parent talks to their dentist about for that individual child.”