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WASHINGTON — The Environmental Protection Agency’s inspector general will investigate allegations that William L. Wehrum, the agency’s former air quality chief, violated ethics rules when he met with former clients from his days as a lawyer and lobbyist for the oil, gas and coal industries.

The inquiry will look into whether Mr. Wehrum’s efforts at the E.P.A. to weaken climate change and air pollution standards improperly benefited those former clients, a congressional aide said .

At issue are Mr. Wehrum’s ties to the Utility Air Regulatory Group, a coalition of utilities and trade groups that lobbies on behalf of coal-fired power plants, which he represented as a lawyer at his former firm, Hunton & Williams.

That relationship first drew scrutiny last year after Politico reported that the 25 power companies and six trade groups that make up the coalition paid the firm more than $8 million in 2017 just before President Trump appointed Mr. Wehrum. (The law firm is now known as Hunton Andrews Kurth. The Utility Air Regulatory Group announced in May that it would disband after winding down operations.)