Environmental Protection Agency Administrator Scott Pruitt has used EPA-funded security for personal trips, Sen. Sheldon Whitehouse wrote in a letter to the agency’s inspector general.

Pruitt took his security detail with him to his home in Tulsa, Oklahoma; a family vacation at Disneyland in California; and the 2018 Rose Bowl game, Whitehouse wrote in the letter obtained by CNN.

The Rhode Island Democrat got the information from an unnamed source, he says in the letter. He said it calls into question why “significant agency resources are being devoted to administrator Pruitt’s ’round-the-clock security, even when he is traveling on non-official business.”

“While I consider matters of personal security to be extremely serious, personal security should never be used as a pretext to obtain special treatment,” he wrote.

For some, Whitehouse’s letter raises new concerns about the cost of Pruitt’s security detail and whether it is excessive.

In February, Pruitt was the subject of intense media scrutiny after it was reported he billed taxpayers roughly $200,000 for travel expenses, which included first-class tickets for him and his staff. Ten of those trips were to his hometown of Tulsa. On a weeklong trip to Italy last June, Pruitt’s security detail cost upwards of $30,000.

“Administrator Pruitt follows the same security protocol whether he’s in his personal or official capacity,” the EPA said in response to questions from CNN. The agency declined to elaborate on that protocol.

Pruitt has received threats — including threats on his life — at an unprecedented clip, which has forced the agency to take unprecedented security measures, the EPA has said.

The EPA’s Office of Inspector General did not comment on Whitehouse’s letter, CNN reported.

Pruitt is one of a long list of Trump officials who have been criticized for exorbitant spending habits on the taxpayer dime.

Housing and Urban Development Secretary Ben Carson caught heat after his department purchased a $31,000 dining room furniture set for his office. The department returned the furniture.

Health and Human Services Secretary Tom Price quit the administration after it was discovered he used taxpayer money on private jets. And an inspector general report found that David Shulkin, the recently ousted Veterans Affairs secretary, used agency funds on a trip for his wife.

And earlier this month House Oversight Chairman Trey Gowdy requested a briefing from Interior Department Secretary Ryan Zinke following news reports that the department spent $139,000 for replacement doors for Zinke’s office.

Zinke blamed the procurement process and said that following the reports of the cost, he was able to bring the price down to $75,000.

Watch: The Winding Tale of One Senate Desk’s Very Long History