The Supreme Court ruled Monday against the Obama administration's attempt to limit power plant emissions of mercury and other hazardous air pollutants, but it may only be a temporary setback for regulators.
The justices split 5-4 along ideological lines to rule that the Environmental Protection Agency did not properly take costs into account when it first decided to regulate the toxic emissions from coal- and oil-fired plants.
The EPA did factor in costs at a later stage, when it wrote standards that are expected to reduce the toxic emissions by 90 percent. But the court said that was too late.
Maryland power plants already have slashed their mercury emissions to comply with a state law, but the ruling could delay relief from lingering mercury contamination in the state, two-thirds of which officials say is imported by prevailing winds from polluting facilities beyond the state's borders.
Lakes statewide remain tainted with mercury, and residents are cautioned to limit how much fish they eat from those waters. Children and women of child-bearing age are considered particularly vulnerable, because mercury can damage the brain and nervous system, impairing speech, memory, thought and coordination.
Maryland's Healthy Air Act, adopted in 2006, required eight of the state's coal-burning plants to reduce emissions of mercury by 90 percent and other key air pollutants by 80 percent to 85 percent. The facilities' owners spent nearly $3 billion on pollution controls, according to state regulators.
Environmental advocates say Maryland's example undercuts complaints that the EPA's regulations would be too costly and destroy jobs.
The EPA rules, which took effect in April, will remain in place while the case goes back to a lower court for the EPA to decide how to account for costs, environmental advocates say.
The rules were supposed to be fully in place next year. At issue was whether health risks are the only consideration under the Clean Air Act.
The challenge was brought by industry groups and 21 Republican-led states, which argued that the regulations were too costly for coal miners, businesses and consumers.
Writing for the court, Justice Antonin Scalia said the EPA was unreasonable in refusing to consider costs at the outset.
"The agency must consider cost — including, most importantly, cost of compliance — before deciding whether regulation is appropriate and necessary," Scalia said.
In dissent, Justice Elena Kagan said it was enough for the EPA to consider costs later in the process.
"Over more than a decade, EPA took costs into account at multiple stages and through multiple means as it set emissions limits for power plants," said Kagan, who was joined by the court's liberal members.
Industry groups and their advocates praised the ruling.
"We are pleased the Supreme Court clearly believes agencies are responsible for determining how a rule would impact the economy before determining that the rule is worthwhile," said Catrina Rorke of the R Street Institute, a Washington think tank focused on free markets and limited government. "In a situation like this, markets matter, too."
The EPA said it is reviewing the court's decision and will determine any appropriate next steps once a review is completed.
"EPA is disappointed that the Supreme Court did not uphold the rule, but this rule was issued more than three years ago, investments have been made and most plants are already well on their way to compliance," EPA spokeswoman Melissa Harrison said.
Indeed, more than 70 percent of power plants have installed controls to comply with the rules, said Vicki Patton, an attorney at the advocacy group Environmental Defense Fund.
"EPA already has an economic analysis that it can rely on to demonstrate that the public health benefits of the standards far outweigh the costs," Patton said.
Robert Percival, a professor and director of the environmental law program at University of Maryland law school, called it a "narrow, technical decision" that will delay but shouldn't ultimately prevent EPA from cracking down on toxic power plant pollution.
"That's what so unfortunate about this," Percival said. "Most responsible utilities are already complying with this stuff or have plans to do so. It just rewards the laggards who said let's take a flier and challenge these regulations."
In the case of the mercury rules, the costs of installing and operating equipment to remove the pollutants before they are dispersed into the air are hefty — $9.6 billion a year, the EPA found.
But the benefits are much greater — $37 billion to $90 billion annually, the agency said. The savings stem from the prevention of up to 11,000 deaths, 4,700 nonfatal heart attacks and 540,000 lost days of work, the EPA said.
The upgrades can have economic benefits too. In Maryland, the work supported 3,000 construction jobs, officials say, and resulted in a net increase of 90 permanent jobs at the plants.
A disproportionate share of the 600 affected power plants, most of which burn coal, are in the South and upper Midwest.
The case is the latest in a string of attacks against the administration's actions to use the Clean Air Act to rein in pollution from coal-burning power plants.
House Speaker John Boehner, R-Ohio, suggested that the high court ruling gives opponents an opening "to protect the jobs and energy that are still at risk under this administration."
Senate Majority Leader Mitch McConnell, R-Ky., called the ruling "a cutting rebuke to the administration's callous attitude." He said it "serves as a critical reminder" to state governors, who are awaiting more EPA rules this summer aimed at curbing pollution from coal-fired power plants that is linked to global warming.
States have challenged those rules even before they are final, and Congress is working on a bill that would allow states to opt out of any rules clamping down on heat-trapping carbon dioxide.
White House spokesman Josh Earnest called out McConnell for reprising his suggestion that governors should flout EPA regulations. He said McConnell was not advocating in the best interests of the American public.
Democratic Maryland lawmakers joined environmentalists in criticizing the ruling. Sen. Ben Cardin called it "a major setback in what should be a bipartisan, nationwide fight to protect the most vulnerable among us – particularly pregnant and nursing mothers and their children." And Rep. Chris Van Hollen accused the court majority of "putting companies profit margins before the health of the American people."
Baltimore Sun reporter Timothy B. Wheeler and the Associated Press contributed to this article.