Fluoride helps prevent tooth decay. It occurs naturally in some foods—tea, potatoes and shrimp, for example—and in some water. In 1945 Grand Rapids, in Michigan, became the first American city to add it to its drinking water. Today more than two-thirds of Americans have water with added fluoride piped into their homes.

The debate over fluoride in drinking water has been elevated with Robert F. Kennedy Jr.'s push to remove the chemical, alleging it does more harm than good.

The CDC calls the practice of adding fluoride to tap water systems one of the 10 greatest public health achievements of the last century.

For years, local water authorities have considered the addition of low concentrations of fluoride to drinking water a public health achievement. The Centers for Disease Control and Prevention recommends it, citing evidence showing that fluoride prevents cavities in children — the No. 1 chronic disease in kids.

Reversing the decades-old public health intervention would be a Day 1 goal of a future Trump administration, Kennedy wrote on social media.