WASHINGTON – After four years of serving as administrator of the Environmental Protection Agency (EPA), oftentimes butting heads with industry groups over environmental regulations industry viewed as excessive and financially burdensome, Lisa Jackson, 50, announced Dec. 27 she plans to resign after President Barrack Obama delivers his State of the Union address in early 2013.

Her four-year tenure was marked by high-profile brawls over global warming pollution, the Keystone XL oil pipeline, new controls on coal-fired plants and several other hot-button issues that affect industry, such as regulating dust.

A chemical engineer by training, Jackson did not point to any particular reason for her departure, according to The Associated Press. Cabinet members looking to move on will usually leave at the start of a president's second term, AP added.

“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,” she said in a statement. “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.

“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,” she added. “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.

“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 concluded. One report states she may run for governor of New Jersey.

President Obama lauded her accomplishments in a statement. "Under her leadership, the EPA has taken sensible and important steps to protect the air we breathe and the water we drink, including implementing the first national standard for harmful mercury pollution, taking important action to combat climate change under the Clean Air Act and playing a key role in establishing historic fuel economy standards that will save the average American family thousands of dollars at the pump, while also slashing carbon pollution," he said.

EPA victories during her tenure include finalizing a new rule doubling fuel efficiency standards for cars and light trucks, AP relayed. The requirements will be phased in over 13 years and eventually require all new vehicles to average 54.5 mpg, up from 28.6 mpg at the end of last year. She also shepherded a rule forcing power plants to control mercury and other toxic pollutants for the first time. The nation's coal- and oil-fired power plants previously were allowed to run without addressing their full environmental and public health costs.

Earlier this month, EPA finalized an update to the agency’s air-quality standards for harmful fine particle pollution including soot. EPA set the annual health standard at 12 micrograms per cubic meter. Ninety-nine percent of US counties are projected to meet revised health standard without any additional actions by 2020, EPA said. A federal court ruled the EPA must update the standard based on best available science.

The existing daily standard for fine particles and the existing standard for coarse particles, which includes dust from farms and other sources, remain unchanged. The particulate matter (PM) health standard for dust from farms and other sources is PM10.