“It is extremely difficult for me to cease serving you in this role first because I count it a blessing to be serving you in any capacity, but also, because of the transformative work that is occurring,” Pruitt wrote. “However, the unrelenting attacks on me personally, my family, are unprecedented and have taken a sizable toll on all of us.”
Pruitt has faced an array of ethical questions since he took office in February 2017, with critics questioning his travel spending, security costs, dealings with industry lobbyists and misuse of government resources.
He has denied wrongdoing in the face of multiple congressional and oversight inquiries.
Before assuming the Cabinet position with the Trump administration, Pruitt was the attorney general for Oklahoma, a state with a booming oil and gas production sector.
Pruitt sued the EPA 14 times, according to The New York Times, including suits over the Obama administration's Clean Power Plan and over the EPA's efforts at reducing methane emissions from oil and gas drilling. The Times also reported 13 of the lawsuits included co-parties that had donated money to Pruitt or his campaigns.
The Associated Press contributed to this report.