By Joel Burgess, Asheville Citizen-Times

A federal appeals court on Monday reversed a judge's ruling requiring prompt installation of upgraded emission controls at three coal-fired power plants in Tennessee and one in Alabama.

A three-judge panel of the 4th U.S. Circuit Court of Appeals unanimously overturned a decision by U.S. District Judge Lacy H. Thornburg, of Asheville, who had declared the plants a "public nuisance" because of their effect on air quality in Western North Carolina.

Air-quality activists and North Carolina Attorney General Roy Cooper said the reversal was a setback for healthy air. Cooper sued TVA in 2006 after North Carolina passed its own emissions control mandating pollution reductions in state plants.

Avram Friedman, executive director of the Canary Coalition in Sylva, North Carolina, said the idea behind the state's 2002 Clean Smokestacks Act and the TVA lawsuit was to protect the health of residents.

"It was important at that time to do this because these power plants had been polluting our air for decades and people were dying and suffering asthma and heart disease and pulmonary disease from these pollutants," Friedman said.

After ruling against TVA, Thornburg ordered the Tennessee Valley Authority to accelerate its planned emission control improvements at the four plants - a demand that TVA said would cost an additional $1 billion. But it was the ruling's impact on utility regulation, not the cost that prompted the appeals court to reverse the decision.

"If allowed to stand, the injunction would encourage courts to use vague public nuisance standards to scuttle the nation's carefully created system for accommodating the need for energy production and the need for clean air," appeals court Judge J. Harvie Wilkinson III wrote. "The result would be a balkanization of clean air regulations and a confused patchwork of standards, to the detriment of industry and the environment alike."

Wilkinson also noted that while North Carolina attempted to frame the case in terms of protecting public health and the environment, those are issues that have been extensively addressed nationwide by the Clean Air Act for four decades.

"This decision recognizes TVA's history of reducing emissions and the importance of the Clean Air Act in proper regulation of our plants," TVA spokeswoman Barbara Martocci said. "It also states that under the Clean Air Act, it is up to EPA and the states, not the courts, to decide what TVA's power plant emissions should be."

During the original suit which began in 2008 in Asheville, a health expert testified that if the emissions caps sought in the lawsuit were imposed, each year in North Carolina there would be 99 fewer premature deaths from cardiovascular and respiratory diseases, 19,000 fewer asthma attacks, 60 fewer hospital admissions, 55 fewer emergency room visits related to asthma and 2,300 fewer lost school days.

A TVA health expert testified the impact of its emissions in North Carolina "is almost imperceptible," while the utility's lawyers argued it was making significant reductions in pollution.

After the most recent ruling, North Carolina can either seek a rehearing before the full appeals court or appeal to the U.S. Supreme Court. Cooper did not say Monday what the next step would be for the state.

"This ruling is disappointing but the fight for clean air is far from over," the attorney general said. "I'm pleased that the TVA is cleaning up the four plants cited in the order and I trust this will continue during the appeals process."

The TVA, the nation's largest public utility, has about 9 million consumers in Tennessee, Alabama, Mississippi, Kentucky, Georgia, North Carolina and Virginia.

The Associated Press contributed to this report.