The senior Environmental Protection Agency (EPA) official in charge of revising vehicle emissions standards has resigned, according to reports.

Bill Wehrum, Assistant Administrator for Air and Radiation, will resign his position effective June 30. He had been working with officials from the National Highway Traffic Safety Administration (NHTSA) on rewriting vehicle admissions standards through 2026. He was also in charge of standards regarding biofuels. Wehrum testified before congress last week that it would be several weeks before the plan was complete.

Wehrum announced his resignation to his staff and associates via e-mail. Principal Deputy Administrator Anne Idsal will replace him in the interim.