Robert F. Kennedy Jr., a prominent proponent of debunked public health claims that Donald Trump has promised to put in charge of health initiatives, said Saturday that Trump will push to remove fluoride from drinking water in his first mandate day.

Fluoride strengthens teeth and reduces cavities by replacing minerals lost during normal wear and tear, according to the US Centers for Disease Control and Prevention. The addition of low levels of fluoride to drinking water has long been considered one of the greatest public health achievements of the past century.

Kennedy made the statement on social media platform X alongside a variety of claims about the health effects of fluoride.

“On January 20, the Trump White House will advise all US water systems to remove fluoride from public water,” Kennedy wrote. Trump and his wife, Melania Trump, “want to make America healthy again,” he added, repeating a phrase Trump often uses and refers to Kennedy.

It was unclear whether Kennedy discussed Saturday’s post with Trump or his aides. The Trump campaign did not respond directly, and a spokesman for Kennedy did not respond when asked.

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“While President Trump has received a variety of policy ideas, he is focused on Tuesday’s election,” said Danielle Alvarez, a senior adviser to the Trump campaign.

But the sudden and unexpected social media post over the weekend evoked the chaotic policymaking process that has defined Trump’s tenure in the White House, when he will issue policy statements on Twitter at almost any hour. It also underscored the concerns many experts have about Kennedy, who has long promoted debunked theories about vaccine safety that have implications for US public health.

In 1950, federal officials approved water fluoridation to prevent tooth decay and continued to promote it even after fluoride toothpaste brands hit the market a few years later. Although fluoride can come from many sources, drinking water is the main source for Americans, researchers say.

Officials lowered their recommendation for fluoride levels in drinking water in 2015 to address a dental condition called fluorosis, which can stain teeth and had become more common in U.S. children.

In August, a federal agency determined “with moderate confidence” that there is a link between higher levels of fluoride exposure and lower IQ in children. The National Toxicology Program based its conclusion on studies involving fluoride levels at about twice the recommended limit for drinking water.

A federal judge later cited that study to order the US Environmental Protection Agency to continue regulating fluoride in drinking water. U.S. District Judge Edward Chen cautioned that he was not certain that the amount of fluoride commonly added to water was causing lower IQs in children, but concluded that growing research indicated an unreasonable risk that it might be. He ordered the EPA to take steps to reduce that risk, but did not say what those steps should be.

In his X message on Saturday, Kennedy tagged Michael Connett, the lead attorney representing the plaintiff in that lawsuit, the environmental advocacy group Food & Water Watch.

Kennedy’s anti-vaccine organization has a lawsuit pending against news organizations, including The Associated Press, accusing them of violating antitrust laws by taking steps to identify misinformation, including about COVID-19 and COVID-19 vaccines . Kennedy is on leave from the group but is listed as one of its attorneys in the lawsuit.

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What role Kennedy might have if Trump wins Tuesday remains unclear. Kennedy recently told NewsNation that Trump asked him to “reorganize” agencies, including the Centers for Disease Control and Prevention, the National Institutes of Health, the Food and Drug Administration and some agencies within the Department of Agriculture.

But for now, the former independent presidential candidate has become one of Trump’s best surrogates. Trump frequently mentions having the support of Kennedy, a scion of a Democratic dynasty and the son of former Attorney General Robert Kennedy and grandson of President John F. Kennedy.

Kennedy traveled with Trump on Friday and spoke at his rallies in Michigan and Wisconsin.

Trump said Saturday that he told Kennedy, “You can work on food, you can work on anything you want,” except oil policy.

“He wants health, he wants women’s health, he wants men’s health, he wants children, he wants everything,” Trump added.