"MATS is really what's driving the decision," for companies to shut some of their coal plants, he said.
The EPA estimated that MATS will save $90 billion in healthcare costs by 2016 as technology to cut mercury emissions also reduces emissions of fine particulates, which can damage hearts and lungs. When combined with other EPA rules, thousands of lives will also be saved, it said.
Environmentalists praised the administration for pushing through tough rules. "EPA will take a significant step toward cleaner air, and we hope to see more progress to protect public health from air pollutants, including greenhouse gases, in the New Year," said Kevin Kennedy, U.S. climate director at the World Resources Institute, said in an email.
Republican lawmakers quickly pounced on the new mercury rules, vowing to stop the regulations.
James Inhofe, the senior Republican senator on the Environment Committee, said he would try to overturn the rule using a "joint resolution of disapproval," a tool that faces an uphill battle in the Democratic-controlled Senate. Inhofe called the rule "a thinly veiled electricity tax" that will hurt jobs.
Jackson, who spoke during her announcement about her two sons' struggles with asthma, said she was not surprised that lawmakers were threatening to derail the regulations, but ultimately these rules were long overdue.
"These standards are 22 years in making. They are what the American people deserve after waiting so long," Jackson said. "My belief is that if we started hiring engineers instead of lobbyists and...scientists instead of lawyers, we would be able to do our job for the American people."