William Wehrum, the fossil fuel industry attorney who came to the Trump administration and developed a highly tactical retreat from federal action on climate change, announced his resignation on Wednesday as an assistant administrator of the Environmental Protection Agency.

His abrupt departure comes as a congressional committee investigates his contacts with former clients.

Just last week, Wehrum helped unveil a signature achievement of that deregulatory drive—the repeal of the Obama administration’s Clean Power Plan and its replacement with a set of weak rules that will do little to curb carbon emissions.

As Wehrum steps down, the agency is bracing itself to defend that rollback in the courts. In addition, he leaves unfinished a slew of other initiatives to lift environmental protections, from the weakening of vehicle fuel economy standards to a recalculation of the health benefits of limiting air pollution.

The EPA said in a press release that Anne Idsal, a former general counsel for Texas’ mineral leasing and environmental agencies, would lead the air office on an acting basis. Idsal, who has expressed doubt on the extent of humanity’s role in climate change, served as the EPA’s regional administer for Texas and neighboring south-central states for 15 months before being named in March as Wehrum’s principal deputy assistant administrator.

Wehrum, who came to the agency from the law firm now known as Hunton Andrews Kurth, was nominated as assistant administrator  the Office of Air and Radiation, one of the agency’s most influential positions. The law firm has a history of challenging environmental rules.

He faced considerable opposition but was confirmed by the Senate in November 2017, during the tenure of EPA Administrator Scott Pruitt, who himself later resigned amid scandal.

This spring, the House Energy and Commerce Committee launched a probe of utility companies’ influence at EPA through their contacts with Wehrum, their former lawyer. Documents obtained by the environmental group Sierra Club early this year through Freedom of Information Act requests showed that as EPA’s top air pollution official, Wehrum met with his former law firm colleagues for lunches, coffees and other gatherings without disclosing the meetings on his official calendar. POLITICO reported that he was helping craft a deregulatory agenda for the firm’s client, the Utility Air Regulatory Group, a coalition of power companies, in the weeks leading up to his nomination in 2017. Wehrum claimed his work on general regulatory issues that were of interest to UARG did not run afoul of ethics rules. Still, UARG opted to disband in May as scrutiny of Wehrum’s close ties to the group increased.

Efforts to Dismantle Climate Policy

The policy changes that Wehrum helped to put into motion at EPA include several of the most consequential moves that the Trump administration undertook to abandon action on climate change, including on:

Auto standards: A freeze of fuel economy standards for passenger cars and light trucks, which the Trump administration aims to finalize later this summer. In Congressional testimony last week, Wehrum held firm to the administration’s contention that the regulatory rollback would improve highway safety, although outside experts and the EPA’s own science advisors found the rationale questionable. The proposal was crafted to have a broad and long-lasting impact, by revoking California’s long-standing authority to pioneer more stringent standards.

Methane rules: A rollback in the requirements that the oil and gas industry faces regarding leaks of the potent greenhouse gas, methane, from its operations. The proposal, which is designed to save the industry $75 million in costs per year, while leading to an increase in methane pollution, is to be finalized later this year.

Environmental reviews: Changes to the federal permitting program known as New Source Review, which has required big pollution emitters to modernize pollution controls when they make major modifications to their facilities. Power companies and other industry groups have long complained about New Source Review, and the Trump administration originally planned to loosen the process as part of its repeal and replacement of the Obama Clean Power Plan. Instead, Wehrum last week said that the EPA intended to address it separately.

Air pollution standards: A review of the National Ambient Air Quality Standards for two important air pollutants—particulate matter and ozone (soot and smog). Under law, the agency is to review those standards every few years to ensure that they are in line with the latest science on pollution health effects. The Trump EPA has stirred controversy with major changes it has made to the scientific review process, including an accelerated timetable and dismissal of a panel of experts who were to be part of the review. The science on the harmful health effects of particulate matter has been an important underpinning of the EPA’s cost-benefit analysis supporting control of fossil fuel emissions, including the rules meant to address climate change.

Cost-benefit analysis: A revision of the cost-benefit analysis used in its regulatory decision-making, to discount the ancillary benefits of reducing co-pollutants. Wehrum got the ball rolling with a proposal to revise the cost-benefit analysis used in the agency’s power plant mercury emissions rules to leave out the co-benefits of reducing particulate matter. The EPA has launched a plan to similarly revise the cost-benefit math throughout its decision-making, in the name of consistency.

Use of science in policymaking: The EPA is moving forward with a plan to limit the kinds of studies it can use in regulatory decision-making. In the name of transparency, the Trump EPA would only allow science where data is publicly available, but that would leave out some of the seminal studies on human health effects—especially on the impact of air pollution. The science was well known to Wehrum, as it was cited by courts that rejected his efforts to challenge the Obama administration’s air pollution standards when he was an industry lawyer.

Rep. Pallone: Investigations Will Continue

EPA Administrator Andrew Wheeler quickly sought to portray Wehrum’s departure as long-planned and unexceptional.

“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 in a statement. “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.”

But Wehrum’s critics said his exit should not disrupt scrutiny of undue influence by his industry clients, and they repeated calls for an inspector general’s investigation.

“Bill Wehrum leaves behind at EPA an air agenda that was forged at the behest of industry and at the great expense of public health,” said Sen. Tom Carper (D-Del.), the highest ranking Democrat on the Senate Environment and Public Works Committee. “Despite his sudden departure, it is incumbent upon the Office of Inspector General to complete the requested investigation into Mr. Wehrum’s actions…that appear to be questionable efforts to achieve the policy objectives of his former clients.”

House Energy and Commerce Committee Chairman Frank Pallone (D-N.J.) said investigations of Wehrum by his panel and others “should, and will, continue.”