(Corrects paragraph 12 to remove the word "former".)
April 16 (Reuters) - The Trump administration on Thursday withdrew the legal justification for an Obama-era rule that forced coal-fired power plants to cut their mercury emissions, saying the cost of compliance far outweighed the public health benefits.
The move, which was slammed by environmentalists and utility companies, leaves the so-called Mercury and Air Toxic Standards in place for now, but could pave the way for lawsuits from companies opposed to it and prevent similar regulations from being implemented in the future.
"It's honest accounting," Environmental Protection Agency Administrator Andrew Wheeler said in a conference call with reporters announcing the move.
At issue is a 2016 conclusion by then-President Barack Obama's EPA that forcing coal-fired power plants to slash mercury output was justified because savings to consumers on healthcare costs would exceed compliance costs. Mercury can harm pregnant women and put infants and children at risk of developmental problems.
The calculations used at the time, however, accounted for how pollution-control equipment at coal plants would reduce emissions of particulate matter and other harmful substances that come out of smokestacks, in addition to mercury.
Republican President Donald Trump's EPA said in 2018 it had reviewed the justification for the rule and believed it was inappropriate to have included the benefits of reducing emissions other than mercury. It proposed withdrawing the justification. Thursday's announcement finalized that proposal.
The revised analysis of the rule estimated the cost to coal- and oil-fired power plants to be between $7.4 billion and $9.6 billion a year, compared with quantified health benefits of just $4 million to $6 million a year - accounting for mercury alone.
"The more transparent we are about the science behind our regulations, and the costs and the benefits behind our regulations, the more acceptance we will see across the board from the American public," Wheeler said.
He emphasized that the rule's requirements had not changed and said the EPA would defend it if challenged in court.
But he added that the changes "foreshadow" the agency's approach to an upcoming cost-benefit regulation.
Environmentalists decried the move, saying it undermined clean air protections vital to protecting public health.
"This is an absolute abomination," said Natural Resources Defense Council President Gina McCarthy, who served as EPA administrator under Obama. "The only ones to benefit from this are powerful polluters - at the expense of our health, and our children's health."
Electric utilities pushed back on the potential loosening of mercury requirements, saying they had invested billions to cut emissions of the dangerous pollutant, and had sought and secured rate increases from power consumers to cover the costs.
"The repeal of the underlying legal basis for MATS introduces new uncertainty and risk for companies that still are recovering the costs for installing those control technologies," Utility trade group Edison Electric Institute said in a statement.
But the U.S. coal industry has railed against the mercury rule, and blamed it for putting hundreds of coal-fired power plants out of business in recent years.
The National Mining Association, which represents coal-company interests, applauded the move.
"While the coal-fueled plants that were forced out of operation by this illegal rule can't be resurrected, it's an important lesson for the future," the trade group said in a statement.
Trump made it a central promise of his 2016 campaign to revive the U.S. coal industry, which he said had been unfairly targeted by Obama's climate and environmental policies.
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