The top air pollution regulator at the Environmental Protection Agency told employees on Tuesday that he is leaving the Trump administration, according to a recording of his remarks obtained by The New York Times.
Aaron Szabo, a former registered lobbyist for the oil and chemical industries, said he would resign as the head of the E.P.A.’s Office of Air and Radiation on July 17. He did not provide a reason for his departure after nearly a year in the Senate-confirmed position.
Since taking the helm of the air office in July 2025, Mr. Szabo has played a central role in President Trump’s sweeping efforts to dismantle climate and environmental protections. Under his direction, the E.P.A. repealed a bedrock scientific finding that climate change endangers human health and the environment. That finding had given the E.P.A. the legal authority to regulate the greenhouse gases that are warming the planet to dangerous levels.
In January, the agency also stopped estimating the monetary value of lives saved when it examines the costs and benefits of possible limits on deadly air pollution.
Mr. Szabo has also been working on a plan by the E.P.A. to erase limits on planet-warming pollution that power plants release into the air. The agency is expected to announce that plan in the coming months, completing the Trump administration’s reversal of the most consequential climate policies of Presidents Joseph R. Biden Jr. and Barack Obama.
Brigit Hirsch, the E.P.A. press secretary, said in a statement that Mr. Szabo and his team were “responsible for saving Americans trillions of dollars by cutting unnecessary red tape, showing it is possible to protect clean air while growing the economy. We wish him all the best in his future endeavors.”
Ms. Hirsch did not immediately respond to questions about why Mr. Szabo is leaving or who would replace him.
Environmentalists welcomed the news of his departure.
“Mr. Szabo and the Trump E.P.A. have the deplorable distinction of presiding over an air pollution agenda with no positive features — it has been all rollbacks, all the time, resulting in worsening air quality and abandoned and weakened safeguards,” said John Walke, a senior lawyer with the Natural Resources Defense Council, an environmental group.
During a hastily scheduled meeting with employees on Tuesday, Mr. Szabo said he planned to take a “well-needed vacation” with his “patient wife” before starting a new job, according to the recording of his remarks. He did not disclose his new employer.
Mr. Szabo also acknowledged that the E.P.A.’s air office had shed many staff members since Mr. Trump returned to office. “We’ve seen our numbers decrease substantially while we have asked you all to do more,” he said.
The E.P.A. lost more than 4,000 employees in the first year of Mr. Trump’s second term, federal data shows. That represented a roughly 24 percent reduction and dropped the agency’s staffing to levels not seen since the Reagan administration.
At his Senate confirmation hearing in March 2025, Mr. Szabo testified that he had a personal stake in clean-air rules because he suffers from cystic fibrosis. “Because of my lung disease, I have always been acutely aware of air quality,” he said.
Before joining the E.P.A., Mr. Szabo worked at the firm CGCN Group, where he lobbied on behalf of the American Chemistry Council, the largest trade group for the U.S. chemical industry. The group has pushed the E.P.A. to weaken Biden-era limits on emissions of a cancer-causing gas called ethylene oxide, which the agency proposed to do in March.
His clients at CGCN Group also included the American Fuel & Petrochemical Manufacturers, a trade association for oil refiners, and the American Petroleum Institute, the top lobbying arm of the U.S. oil industry.
Earlier in his career, Mr. Szabo worked at the White House Office of Information and Regulatory Affairs, which reviews regulations before they are publicly released.
