Bill Wehrum, the Environmental Protection Agency’s top air-policy official, in Washington earlier this month. (Bill O’Leary/The Washington Post)

Less than a month into his tenure as the top air-policy official at the Environmental Protection Agency, Bill Wehrum hopped into the EPA’s electric Chevy Volt and rode to the Pennsylvania Avenue offices of his former law firm.

There, he met with representatives of the nation’s largest power companies — including two groups that, shortly before, had been his paying clients — to brief them on the Trump administration’s plans to weaken federal environmental regulations.

The Dec. 7, 2017, meeting is just one example of interactions between Wehrum, a skilled lawyer and regulator, and former clients that ethics experts say comes dangerously close to violating federal ethics rules. Wehrum acknowledges that since joining the EPA in November 2017, he has met with two former clients at his old firm — without consulting in advance with ethics officials, even though they had cautioned him about such interactions. He also weighed in on a policy shift that could have influenced litigation involving DTE Energy, a Detroit-based utility represented by his former firm.

Late last week, three Democrats — Rep. Frank Pallone Jr. (N.J.), chairman of the House Energy and Commerce Committee, and Sens. Sheldon Whitehouse (R.I.) and Thomas R. Carper (Del.) — asked the EPA’s Office of Inspector General to investigate Wehrum’s conduct, saying it runs afoul of rules requiring federal appointees to recuse themselves from most matters involving former clients and employers for two years.

“There’s a plain and flagrant violation of the ethics rules,” Whitehouse said in an interview. “It’s hard to overlook in an agency that’s absolutely riddled with industry operatives that appear to be putting a thumb, wrist, forearm and elbow on the scale for the industry patrons they service.”

In an interview, Wehrum defended his conduct, saying he has followed the letter of the law on ethical matters.

“I have, from day one, tried to be absolutely strict and assiduous as to what I do about complying with my ethical obligations,” Wehrum said, “because it doesn’t do me any good, and it doesn’t do the agency any good, to be doing things that people see as unethical.”

President Trump has tapped dozens of former industry lobbyists to fill senior roles in various agencies whose work affects their former clients, federal records show. That list includes more than a dozen EPA appointees, including the president’s nominee to head the agency, acting EPA administrator Andrew Wheeler, a former coal lobbyist.

Under Wheeler and his predecessor, Scott Pruitt, the EPA has moved aggressively to roll back Obama-era environmental regulations criticized as onerous by industry leaders — a mission in which Wehrum has played a crucial role.

To avoid conflicts of interest, Trump asks appointees to sign an ethics pledge that requires them to recuse themselves from specific matters involving their former employers and clients for two years. If an appointee does meet with a former client, the pledge, part of a 2017 executive order, says the session should be open to all interested parties — a dictum that has been interpreted to mean four other participants who were not clients.

Wehrum said he is still unclear about exactly what sort of meetings are permissible under the Trump pledge. However, he said he has concluded that his meetings comply as long as five entities participate. And, he said, it does not matter how many of those entities are former clients.

“It’s enormously important to me to understand — as it relates to how folks in industry are potentially affected by what we’re doing — who I can talk to, who I can be dealing with and who I can’t,” he said.

Wehrum’s former law firm, Hunton Andrews Kurth, is one of the nation’s premier challengers of federal air and water pollution standards. Its website notes that its clients “include most major industrial groups that are affected by air quality regulations” and says it raises “frequent” court challenges to EPA regulations. The firm declined requests for comment.

A trained chemical engineer who earned his law degree at night while working for a company in Delaware, Wehrum, 55, led the EPA’s air and radiation office on an acting basis under President George W. Bush until Democrats blocked his nomination.

He joined Hunton as a partner in 2007 and spent the next decade representing utilities, petrochemical manufacturers and trade groups. In his last year at the firm, he reported income of $2.15 million. At the EPA, his salary is $164,200.

Among Wehrum’s clients was the Utility Air Regulatory Group, a coalition of power companies that use coal. The organization lacks corporate forms and does not have a physical office separate from the law firm.

Just months before joining the EPA, in May 2017, Wehrum invited then-EPA official Mandy Gunasekara to brief the group “on any Clean Air Act regulatory issue that you are willing and able to address,” according to emails released under a Freedom of Information Act lawsuit by the Sierra Club, an environmental advocacy group. The email was first reported by Politico. And in June, according to a document first obtained by Politico, Wehrum convened the Utility Air Regulatory Group for a meeting at which he and his colleagues requested $8.2 million for work related to the EPA.

Soon after joining the EPA, Wehrum spoke at an event on Dec. 7, 2017, organized by his former law partner, Makram Jaber, on behalf of the group; the event was first reported by E&E News, which covers energy and the environment. In an interview,Wehrum said he asked Jaber to include Duke Energy, another former client, and three other utilities — all among the Utility Air Regulatory Group’s most generous backers — so the event would comply with his interpretation of Trump’s ethics pledge.

Wehrum said the reason he did not run the meeting by ethics officials was that he thought he knew what the rules were and did not see it as a potential business development opportunity for Hunton.

That same week, Wehrum participated in an agency decision that appeared to benefit his former law firm.

On Dec. 7, 2017, Pruitt, then the EPA chief, signed a memo saying the agency would not be “second guessing” companies’ projections about how much their expanded operations might increase pollution.

The memo’s timing was fortuitous for Hunton — it came on the eve of a critical Supreme Court hearing in a case against DTE Energy. In 2010, President Barack Obama’s EPA had accused DTE of excluding pollution that would result from its expansion of a Michigan coal plant when it calculated whether it needed to apply for a federal permit.

The timing was no coincidence. In a Dec. 4, 2017, email to other top EPA officials, Gunasekara said the memo had to be finalized before the court met on Dec. 8.

“The cert hearing is planned for Wednesday,” she wrote in reference to the court’s review of the DTE case. “The memo needs to go out before.”

Hours before the justices conferred on the case, Hunton hand-delivered Pruitt’s memo to the Supreme Court. After the high court declined to take up the case, the matter entered settlement talks, and DTE’s hand has been strengthened.

Though Wehrum was prohibited by ethics rules from engaging in any matter regarding the DTE lawsuit, he acknowledged reviewing the Pruitt memo in advance and discussing it with EPA colleagues in a meeting on Dec. 5, 2017.

He said a lawyer in the EPA’s Office of General Counsel cleared him to hold the meeting to explain the intent of 2002 air rules he helped write during the Bush administration — rules that were key to the DTE dispute. Two political appointees redacted the memo before the meeting to black out references to DTE’s lawsuit, while preserving the rest for Wehrum to read.

“I looked at that [redacted] document, and then I sat in one meeting where we talked about the meaning of the 2002 rules,” Wehrum said. “That was it. That was my involvement.”

However, two people familiar with the meeting, speaking on the condition of anonymity to discuss internal deliberations, said the discussion ranged beyond the 2002 rules, covering topics such as the memo’s potential impact on future EPA enforcement activities and the need to issue it before the Supreme Court conference on the DTE case.

John Walke, who directs the clean-air project at the Natural Resources Defense Council, blasted Wehrum’s involvement in drafting the memo.

“EPA was winning against DTE Energy, which is what makes these revelations so damning,” Walke said. “It was an abuse for him to facilitate amnesty for his former law firm’s client in a pending enforcement case.”

Don Fox, who served as general counsel and later acting director of the Office of Government Ethics during the Obama administration, said Wehrum’s conduct raises “significant” ethical issues.

His meetings with former clients and his involvement with the Pruitt memo are “highly problematic,” Fox said. “It would seem to me to be a misuse of position.”

Magda Jean-Louis contributed to this report.