Jackson, 50, announced her departure in a statement Thursday. She gave no particular reason for leaving but said she was ready for new challenges, time with her family and new opportunities to make a difference.
Jackson’s tenure was marked by high-profile brawls with industry and congressional Republicans over such issues as global warming pollution, the Keystone XL oil pipeline and new controls on coal-fired plants.
Under her leadership, the agency declared for the first time that carbon dioxide was a danger to human health and could be regulated under the Clean Air Act, leading the EPA to develop a new regulatory regime to limit carbon emissions.
"I want to thank President Obama for the honor he bestowed on me and the confidence he placed in me four years ago this month when he announced my nomination as Administrator of the Environmental Protection Agency," Jackson said.
"At the time I spoke about the need to address climate change, but also said: There is much more on the agenda: air pollution, toxic chemicals and children’s health issues, redevelopment and waste-site cleanup issues, and justice for the communities who bear disproportionate risk," she added.
Jackson is expected to leave after the State of the Union address in late January. Cabinet members looking to move on often leave at the beginning of a president’s second term.
"As the President said earlier this year when he addressed EPA’s employees, you help make sure the air we breathe, the water we drink, the food we eat are safe. You help protect the environment not just for our children but their children. And you keep us moving toward energy independence. We have made historic progress on all these fronts," Jackson said.
"So, 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," she added.
President Obama thanked Jackson for her service, praising her work on mercury pollution limits, fighting climate change and helping set new fuel economy standards for vehicles.