Environmental Protection Agency Administrator Lisa Jackson on Thursday announced she would step down after President Obama’s state of the union address later this January.

During her tenure, the 50-year-old chemical engineer issued several rules that aim to cut emissions of mercury, sulfur dioxide, and other pollutants. The rules have been hailed by health and environmental groups, but criticized as too costly by industry and Congressional Republicans.

According to Bloomberg, possible candidates that could replace Jackson include her deputy, the EPA’s Bob Perciasepe; Heather Zichal, the top White House aide for energy and environment; Gina McCarthy, the assistant administrator of EPA for air pollution; or Dan Esty, a former Yale professor that is an environmental regulator in Connecticut.

Jackson’s departure has had mixed reactions on Capitol Hill. One of the agency’s most vocal opponents, Sen. Jim Inhofe (R-Okla.)—who also serves as ranking member of the Senate Committee on Environment and Public Works (EPW)—said in a statement that he had always "appreciated her receptivity to my concerns, her accessibility and her honesty.  She was one of the few at the EPA that was honest with me," Inhofe said. "While so many others Obama Administration appointees don’t tell the truth, she did, and I hope that is not the reason for her departure."

 Jackson did not announce future plans, but said she is "“ready in my own life for new challenges, time with my family and new opportunities to make a difference.”

I will leave the EPA confident the ship is sailing in the right direction, and ready in my own life for new challenges, time with my family and new opportunities to make a difference," Jackson said in a statement last week.

Sources: POWERnews, Bloomberg, EPA
—Sonal Patel, Senior Writer (@POWERmagazine)