At least 15 companies with financial ties to Oklahoma Attorney General Scott Pruitt, Donald Trump’s nominee to run the Environmental Protection Agency, have faced hundreds of EPA enforcement actions, which are the basic tool the agency uses to enforce environmental rules and laws.

Among the Pruitt donors with enforcement cases against them in recent years are Continental Resources, an oil company that contributed to Liberty 2.0, a pro-Pruitt Super PAC; Murray Energy, which was a co-party in eight of 14 lawsuits Pruitt filed against the EPA and contributed to his political campaigns; and Devon Energy, which raised money for the Republican Attorneys General Association when Pruitt led it and whose lawyers penned a letter that Pruitt sent to the EPA. Peabody Energy, whose executive Fred Palmer contributed to Pruitt’s 2014 re-election campaign for Oklahoma attorney general, is the parent company of 12 separate coal companies that have faced EPA enforcement actions. In addition to the energy companies, the agricultural company Monsanto, which contributed to Pruitt’s 2010 and 2014 election campaign, has been named in 96 formal administrative cases, according to EPA records. It’s impossible to tally a complete list of the enforcement cases filed against Pruitt donors because some donations, such as those to the most recent pro-Pruitt PAC, Protecting America Now, can be made secretly.

Some of the enforcement actions were small, such as the investigation and citation that led the EPA to fine Chesapeake Energy $500 for discharging oil into a waterway flowing into Kentucky’s Cumberland River — that was one of four cases brought by the EPA against Chesapeake. And sometimes the agency’s efforts to enforce the rules fail, as they did when the EPA lost its 2013 suit against Oklahoma Gas & Electric over emissions from two of its plants that, according to the complaint, violated the Clean Air Act. Oklahoma Gas & Electric contributed to Pruitt’s 2002, 2010, and 2014 re-election campaigns.

But other enforcement efforts were much larger, such as the one that resulted in a settlement with Southern Coal and 26 affiliated mining companies in 2016. Southern Coal is a division of Southern Power, which has been co-party in four of Pruitt’s 14 suits against the EPA. (A Southern executive, L. Ray Harry, contributed to Pruitt’s 2014 re-election fund.) An EPA investigation of Southern Coal found numerous violations of the Clean Water Act at its mines in Appalachia, which according to EPA records impacted waterways, killing fish and endangering the health of local communities. The EPA’s response, which included instituting preventive measures, data tracking, and training of mine workers, cost some $5 million and eliminated an estimated 5 million pounds of pollution from being released into local waterways.

Whatever their size, enforcement actions are “the backbone of our environmental program,” said Cynthia Giles, who stepped down from her position as assistant administrator of the Office of Enforcement and Compliance Assurance, or OECA, on January 20. “Enforcement is how we make the protections of environmental laws real on the ground. It’s everything from taking on the big multinational corporations who are cutting corners at the expense of public health to the very local small matters that are hugely important to local communities.”

Yet these actions, which are necessary to keep pollutants out of our air and water, will likely be severely scaled back if and when Pruitt takes over the EPA. Pruitt, whose confirmation may be up for a vote in the Senate this week, dismantled the environmental protection unit in Oklahoma in 2011 and as attorney general largely abandoned environmental regulation in that state. The Trump administration’s plan for the EPA involves not just installing a proven opponent of environmental enforcement as head of the EPA, but possibly shuttering its enforcement arm, according to a recent report from Inside EPA.

While the vote on Pruitt’s nomination has been delayed as a result of a Democratic boycott, the ACLU and the Center for Media and Democracy sued the Oklahoma Attorney General’s Office in an effort to obtain more than 3,000 of Pruitt’s emails with energy industry groups and corporations, including Koch, Exxon, and Murray. On Friday, the Oklahoma Attorney General’s Office released 411 of the emails, which document frequent communications and regular meetings between Pruitt and energy companies and industry groups. Today, the Center for Media and Democracy amended its lawsuit in an effort to obtain the thousands of remaining emails. An Oklahoma judge is scheduled to hear the case on Thursday, according to the center’s Nick Surgey.

Eliminating OECA, which was established in the early 1990s, would be in keeping with how Pruitt handled environmental enforcement as Oklahoma attorney general. According to Giles, it would also be a “colossally bad idea.”