A plume of exhaust extends from the Mitchell Power Station, a coal-fired power plant along the Monongahela River, 20 miles southwest of Pittsburgh, in 2013. (Jeff Swensen/Getty Images)

The Trump administration has hit the pause button on an Obama-era regulation aimed at limiting the dumping of toxic metals such as arsenic and mercury by the nation’s power plants into public waterways.

“I have decided that it is appropriate and in the public interest to reconsider the rule,” Scott Pruitt, head of the Environmental Protection Agency, wrote this week in a letter to groups that had petitioned the agency to revisit the rule, which was finalized in 2015.

Beginning in 2018, power plants would have had to begin showing that they were using the most up-to-date technology to remove heavy metals — including lead, arsenic, mercury and other pollutants — from their wastewater. Pruitt wrote that the EPA plans to postpone compliance deadlines for the regulation, which is also being challenged in a federal court. On Thursday, the EPA said the rule would cost the industry hundreds of millions of dollars a year to comply with.

“This action is another example of EPA implementing President Trump’s vision of being good stewards of our natural resources, while not developing regulations that hurt our economy and kill jobs,” Pruitt said in a statement. “Some of our nation’s largest job producers have objected to this rule, saying the requirements set by the Obama administration are not economically or technologically feasible within the prescribed time frame.”

The move drew immediate condemnation from environmental groups, which called it a gift to the energy industry. They insisted that the Trump administration focused only on potential costs of the rule while ignoring its benefits, and that delays in compliance will endanger wildlife and pose health threats to families that live near coal plants, as exposure to heavy metals can cause problems with cognitive development in children, among other problems.

“Trump’s attempt to halt these clean water protections for mercury, lead and arsenic from coal power plants is dangerous and irresponsible,” the Sierra Club’s Mary Anne Hitt said in a statement.

That group and others noted that power plants represent the largest industrial source of toxic wastewater pollution in the country and that more than a third of coal plants discharge wastewater within five miles of a downstream community’s drinking water intake. They also argued that the Obama administration’s rule was based on years of peer-reviewed studies, input from health experts and a mountain of public comments.

“Despite all this, Trump’s EPA administrator is trying to throw it all away to placate polluters,” Hitt said. “Trump’s decision to attack our right to clean water on behalf of coal executives is just another indication of who this administration works for — and it isn’t American families.”

In its push to finalize the rule in 2015, the Obama administration noted that federal standards to curb toxic dumping by coal-fired power plants had not been updated in several decades and that states had left the problem largely unregulated. But in the past month, industry representatives have urged the new administration to revisit the rule.

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A coalition of energy companies known as the Utility Water Act Group argued in a petition that stretched more than 100 pages that the regulation, if left in place, “will cause negative impacts on jobs dues to the excessive costs of compliance — which were grossly underestimated by the EPA — and regulatory burdens forcing plant closures. Those impacts are being, and will be, felt in communities around the country.” That group, as well as the U.S. Small Business Administration, also argued that the rule represents precisely the type of regulation that Trump targeted in a recent executive order instructing the government to revise regulations whose costs outweigh their benefits.

Pruitt appears to agree. In a Federal Register notice filed this week, the EPA said “justice requires” it to stay the regulation’s current deadlines “in light of the capital expenditures that facilities incurring costs under the Rule will need to undertake in order to meet the compliance deadlines for the new, more stringent limitations and standards in the rule.”

On Thursday, Pruitt visited a coal mine in southwestern Pennsylvania to launch what the EPA called a “back-to-basics” agenda. That agenda includes rolling back a broad range of Obama-era regulations, most notably the Clean Power Plan, which sought to regulate carbon dioxide emissions from the nation’s power plants.

“The coal industry was nearly devastated by years of regulatory overreach,” Pruitt said in a statement touting his visit. “But with new direction from President Trump, we are helping to turn things around for these miners and for many other hard working Americans.”