Both the E.P.A. and the lobbying firm dispute that there was any connection between the agency’s action and the condo rental, for which Mr. Pruitt was paying $50 a night…

Nevertheless, government ethics experts said that the correlation between the E.P.A.’s action and Mr. Pruitt’s lease arrangement — he was renting from the wife of the head of the lobbying firm Williams & Jensen — illustrates why such ties to industry players can generate questions for public officials: Even if no specific favors were asked for or granted, it can create an appearance of a conflict.

“Entering into this arrangement causes a reasonable person to question the integrity of the E.P.A. decision,” said Don Fox, who served as general counsel of the Office of Government Ethics during parts of the Obama and George W. Bush administrations.