When Robert F. Kennedy Jr. endorsed Donald J. Trump last week, he recounted speaking with the former president about “the issues that bind us together,” including “having safe food and ending the chronic disease epidemic.”

Mr. Kennedy, a onetime environmental lawyer and longtime vaccine critic, insisted that a second Trump administration would lead to the elimination of pesticides and other hazardous chemicals in America’s food and water supply.

“We will make Americans healthy again,” Mr. Kennedy said.

“Don’t you want healthy children?” he asked. “And don’t you want the chemicals out of our food? And don’t you want the regulatory agencies to be free from corporate corruption? And that’s what President Trump told me that he wanted.”

As president, though, Mr. Trump ended more than 100 environmental policies, including bans on toxic chemicals known to pose serious health threats. He installed industry lobbyists in top jobs, where they took actions that helped the companies they once represented and worked to gut most federal health and safety agencies.

“They basically did what industry asked them to do,” said Rena Steinzor, who teaches administrative and food safety law at the University of Maryland. She said it was “laughable” to think a second Trump administration would be different.

Asked for comment, Brian Hughes, a senior adviser to the Trump campaign, said in a statement that “we are proud” that Mr. Kennedy, who suspended his independent bid for president, had “been added to the Trump/Vance transition team.”