EPA air chief Bill Wehrum is stepping down within the next few days, agency Administrator Andrew Wheeler announced this morning.

In an email to staff, Wehrum said he would resign on June 30.

He will be replaced for now by Anne Idsal, the principal deputy assistant administrator for the Office of Air and Radiation.

Wehrum has led the office since winning Senate confirmation for the post in November 2017. A former industry lawyer who also worked at EPA during George W. Bush's administration, he has been a magnet for controversy, with top congressional Democrats repeatedly pressing the agency's inspector general to investigate alleged ethics violations.

In today's release, however, Wheeler suggested Wehrum's departure was voluntary.

"While I have known of Bill's desire to leave at the end of this month for quite some time, the date has still come too soon," Wheeler said. "I applaud Bill and his team for finalizing the Affordable Clean Energy regulation last week and for the tremendous progress he has made in so many other regulatory initiatives."

Wehrum did not immediately reply to an email requesting comment on the reasons for his departure.