Pennsylvania moved a step closer to reducing unhealthy mercury emissions from its coal-fired power plants yesterday when the Environmental Quality Board approved new state rules that are tougher than federal standards.

The new rules, pushed by the Rendell administration and opposed by the utility companies, coal industry and state Senate Republicans, will cut emissions of the neurotoxin mercury by 80 percent by 2010 and by 90 percent by 2015.

The Environmental Quality Board, dominated by Rendell administration appointees, voted 17-3 to approve the tougher mercury controls, which were supported by all but three dozen of the almost 11,000 responses collected during a recent public comment period.

"This is a tremendous victory for public health, the environment and our economy," Gov. Ed Rendell said. "Efforts to attract new investment and keep young people here are undermined as families and businesses understand that Pennsylvania is laden with more toxic mercury pollution than nearly anywhere else in the U.S. Our residents deserve better."

The federal mercury regulation requires a 70 percent reduction in mercury emissions by 2018, but allows smaller, older power plants to avoid installing any controls if they purchase "credits" from other power plants that have reduced emissions by more than required.

That so-called "cap and trade" program is absent from the Rendell administration's rule because power companies could avoid retrofitting some plants in Pennsylvania and still meet federal standards by purchasing credits from newer plants in other states. Such a system could also perpetuate mercury "hot spots" located downwind from plants operating without mercury controls.

Pennsylvania and 20 other states have sued the U.S. Environmental Protection Agency in federal court claiming that provision would hurt their efforts to reduce mercury emissions.

Before it can go into effect, the state rule must pass review by the five-member Independent Regulatory Review Commission within the next 30 days. Such an approval would allow the state to meet the Nov. 17 federal filing deadline for reporting its reduction plan.

A dozen states are in the process of adopting mercury emissions controls that are stronger than those contained in federal regulations passed in July 2005, but Pennsylvania would be the first major coal-producing state in that group, a major issue for many opponents of the rule, who also question the health benefits.

State Sen. Mary Jo White, one of the three quality board "no" votes on the mercury rule and the Republican chairwoman of the Senate Environmental Resources and Energy Committee, said it will provide no health or environmental benefits and could damage the state coal industry.

Ms. White has authored a bill that would reduce mercury emissions by 86 percent but, like the federal regulation, would permit power plants that can't meet reduced emission limits to buy credits from those that can.

The Electric Power Generation Association, a utility company lobbying group in Harrisburg, was also critical of the Rendell rule, saying it will threaten electricity reliability and increase consumer costs. It also proposed a mercury control plan that contains the same reductions and time frame as the Rendell rule, but includes a cap and trade provision.

Pennsylvania's utility plants and industries emit more than 5 tons of mercury a year, second only to Texas and just ahead of Ohio, which sends some of its emissions into Pennsylvania on prevailing winds.

Mercury is a neurotoxin that moves from the air into the soil and water, changes into methyl mercury, and is ingested by fish, which are eaten by people. Such exposure can be especially harmful to pregnant women, babies and children, and can cause attention and language deficits, memory loss, autism, mental retardation and impaired vision.

Because of elevated mercury levels, a one-meal-a-week consumption advisory for all fish caught in Pennsylvania waters has been in effect since April 2001.

It will cost the state's 36 coal-fired power plants an estimated $223 million to install the necessary mercury controls, and cost each residential customer about $13 extra a year.

Another cost could be a reduced demand for Pennsylvania coal, which contains twice as much mercury as coal mined in West Virginia and Kentucky, and five times as much as Western states' coal.

A study done for the coal industry found it could reduce the sale of Pennsylvania coal by 85 million tons over nine years, said George Ellis, president of the Pennsylvania Coal Association.

"DEP says the federal rule is discriminatory to Pennsylvania coal, but we think this state rule will discourage use of Pennsylvania coal because of our high mercury content," Mr. Ellis said. "And some of the older, smaller coal-fired power plants in the state could shut down rather than install expensive emission reduction equipment."