Jackson, who many have said has been at the vanguard of President Barack Obama’s seeming war on coal, said she would leave the EPA after the State of the Union address.

The timing is interesting because it was in this year’s State of the Union address that Obama seemed to make his intentions towards the coal sector clear. When he spoke about the nation’s energy needs he made no mention of coal.

Jackson has been head of the EPA for the past four years.

She presided over the introduction of rules that limit the amount of mercury, sulfur dioxide and soot that power stations can emit.

It is these rules that have made it much more costly for electricity utilities to use coal to fire their generators.

“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.’,” she said.

“So, I will leave the EPA confident the ship is sailing in the right director and ready in my own life for new challenges, time with my family and new opportunities to make a difference.”

Sierra Club executive director Michael Brune thanked Jackson for her work in the EPA.

“In her four years as EPA administrator Lisa has been a steadfast advocate for clean air, clean water, a stable climate and public health – often in the face of very vocal and forceful detractors,” he said.

“With her leadership our country has made a big down payment on its goals to reduce carbon pollution.”