Bill Wehrum, head of the Environmental Protection Agency’s air-quality office, announced Wednesday he was stepping down amid accusations that he helped members of the energy industry who were once his clients. Before joining the Trump administration, Wehrum worked as an attorney representing power companies seeking to scale back air-pollution rules. At the EPA, Wehrum sought to loosen coal plant regulations and helped to write some of the administration’s most significant rules weakening climate-change protections. His actions led lawmakers to open a probe in April examining whether he improperly aided his former clients, a potential violation of federal ethics rules.

Wehrum’s decision to leave follows the resignation of EPA Chief Scott Pruitt last July, making him the second high-profile resignation from the agency in the past year. Pruitt resigned after a deluge of reports on his alleged abuse of agency resources, sparking an ethics investigation. Anne Idsal, principal deputy assistant administrator of the air office, will take on Wehrum’s air chief role in an acting capacity, according to the EPA.