According to Sheehan, total SO2 emissions nationwide have decreased dramatically. In the last 20 years, nearly 20 million tons of sulfur dioxide were emitted by power plants in the U.S.
"That number has decreased to about 5.5 million tons per year - a huge drop," he said. "That is, essentially, because of the acid rain program that the federal government has been running and the cap-and-trade pollution allowance reduction program that was put in place. It's been a huge success, it's cleaned up pollution much cheaper and faster than anybody anticipated, and it did it in a way that was least expensive for the power companies."
Sheehan says it's imperative for states to take action against high-polluting power plants, noting that the federal government alone doesn't have the available resources.
"New York and other states have been very aggressive in trying to get these power plants to clean up and have been extremely successful in getting the courts to order that clean-up."
The attorney general's lawsuit seeks to force Homer City to fully comply with the Clean Air Act. At the same time, the power plant must answer to a separate lawsuit, filed by the U.S. Environmental Protection Agency.
Schneiderman's suit names both the current owners of Homer City Station - which includes eight limited liability companies - and the plant's operator, EME Homer City Generation LP.
The suit also names two companies that previously owned the plant - the Pennsylvania Electric Company and the New York State Electric & Gas Corporation.