Pennsylvania will implement the federal Clean Air Interstate Rule aimed at controlling regional power plant emissions through a "cap and trade" program, a decision that was supported by environmental groups and electric utilities.

The announcement by the state Department of Environmental Protection yesterday clears the way for the 2005 rule that federal estimates say will prevent 17,000 deaths and 700,000 cases of asthma, bronchitis and other respiratory ailments annually across the Midwest and Mid-Atlantic regions by 2015.

The DEP decided to implement the rule after the U.S. Court of Appeals for the D.C. Circuit issued an order last week that leaves the CAIR in effect while the U.S. Environmental Protection Agency develops new program rules and controls. In July, the same federal court had vacated the rule, leading to concerns from Pennsylvania, other states and environmental groups about deteriorating air quality that caused the court to reconsider.

"The court's decision is a positive outcome for Pennsylvania's air quality, as it will allow residents of the commonwealth to benefit from regionwide CAIR emission reductions while EPA addresses the flaws the court identified," said John Hanger, DEP acting secretary.

Timing of the latest court decision was crucial. The rule's first deadline is Jan. 1, when power plants must begin complying with established pollution limits or "caps" for nitrogen oxides by either reducing emissions or paying to trade for emissions reduction credits achieved by other power plants. Similar emissions limits for sulfur dioxides will take effect in 2010.

"This is good news and Pennsylvanians will see improvements in air quality even if power plants decide to enter the pollution credit market and we don't see emissions improvements at individual plants," said Charles McPhedran, lead attorney for Citizens for Pennsylvania's Future, a statewide environmental group. "That's because southwestern Pennsylvania gets lots of pollution transported from upwind states."

The cap-and-trade approach, in which no individual power plant must make reductions but the industry must meet overall limits, is favored by the electric utilities industry and pro-business development organizations because of its flexibility and cost-effectiveness.

Neither the state nor the EPA has an estimate of how many of the state's power plants will have to install controls to limit emissions. Larger plants are more likely to install controls that will keep them operating but older plants are less likely.

"We're pleased with the federal court's reinstatement of the CAIR rule and in a good spot to meet its requirements," Mark Durbin, a FirstEnergy spokesman, said of the company's 2,460-megawatt Bruce Mansfield coal-fired power plant in Shippingport, Beaver County, where selective catalytic reduction equipment to reduce nitrogen oxides emissions and scrubbers to reduce soot have been installed. The plant's three power generating units went online in 1976, 1977 and 1980.

Doug Colafella, a spokesman for Allegheny Energy, said the company was moving ahead with installation of sulfur dioxide controls and scrubbers at its Hatfield Ferry power plant in Greene County and the Fort Martin plant along the Monongahela River in West Virginia near the Pennsylvania line before the rule was reinstated last week.

He said nitrogen oxide emissions at those power plants have already been reduced by 57 percent from 1990 levels and should go down another 40 percent by 2010. Sulfur dioxide levels are down 48 percent and will eventually be reduced by 85 percent.

According to the EPA, in 2010 CAIR will reduce nitrogen oxide emissions across the region by 44.6 percent or 1.2 million tons, and sulfur dioxide emissions by 71 percent or 3.6 million tons. Cutting those pollutants will cost utilities about $4 billion a year and eventually cost electric consumers about $1 more a month on their electric bills but save $85 billion annually in health care costs.