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.

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.

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

Fluoride is missing from 43% of Californian faucets, including Bay Area towns of Los Altos, Santa Cruz, Novato and parts of Santa Clara, San Jose and Livermore.

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

Donald Trump has nominated RFK Jr., who wants to remove fluoride from U.S. water systems, to head the Health Department.

President-elect Donald Trump’s pick to lead the Health and Human Services Department is raising concerns in the dental community over his push to rid the country’s public water supply of fluoride.