Charles McPhedran, a lawyer for Harrisburg-based Citizens for Pennsylvania's Future, said the group, known as Penn Future, took the action because it fears the U.S. Environmental Protection Agency will issue national mercury emission rules that are too weak to protect the public. He said EPA statistics show that power-plant emissions are responsible for 40 percent of all emissions of the highly toxic metal.

"One in six [Pennsylvania] women of childbearing age has so much mercury in her body that her nursing infant or fetus is in danger of brain damage," he said. "In addition, the state's streams and fish are so contaminated with mercury that Pennsylvanians have been warned to restrict their consumption of fish to avoid being poisoned."

Coal-burning power plants are the leading source of mercury pollution, according to scientists.

McPhedran said existing technology can bring mercury emissions to an acceptable level. He said the state Environmental Quality Board, part of DEP, has authority to issue state regulations if the federal EPA fails to act. His proposed regulations would affect 23 coal- fired power plants and 11 waste-coal plants in the state.

"Whatever the cost is, it's unavoidable," said John Hanger, president of Penn Future. "We have so much mercury within our borders. It's past time to get going."

Connie Walker, a spokeswoman for PPL Corp., claimed that 75 percent of mercury pollution in the United States comes from outside the nation's borders, although she could not cite specific sources. She said power plants are responsible for just 10 percent of U.S. mercury pollution and 1 percent worldwide.

"State regulations will have little impact on lakes, streams and fish in Pennsylvania," Walker said. "They will put us at a competitive disadvantage and increase the cost of electricity."

She said no current technology could reduce mercury emissions from power plants. McPhedran sharply disagreed, pointing to reports and studies that show the technology is available.

Reliant Energy spokeswoman Pat Hammond said there is "much debate" about how to reduce mercury pollution, and it would be difficult to implement controls while the debate continues. She said if more stringent regulations are adopted, Reliant, which purchased most of GPU's coal-burning power plants, would comply.

DEP spokesman Kurt Knaus said the state prefers a strong federal rule on mercury reduction because it would deal with cross-border pollution and ensure equitable regulation in each state.

Other groups supporting Penn Future's petition include the Pennsylvania Federation of Sportsmen's Clubs.