Washington ? The Bush administration relaxed air pollution regulations and proposed other changes Friday to make it easier for older factories, refineries and power plants to modernize without having to install expensive new anti-pollution equipment.

The long-awaited regulatory changes by the Environmental Protection Agency touched off a firestorm of criticism from environmentalists, Democrats and state air quality regulators, and a courtroom challenge from nine Northeastern states affected by power plant pollution.

The agency also proposed a new definition for what constitutes “routine maintenance, repair and replacement” at aging coal-burning power plants. It will allow them to make major modifications without forfeiting their exemption from tougher standards imposed on plants built in the past 25 years.

EPA Administrator Christie Whitman said in a statement the changes would “encourage emission reductions” by providing manufacturers, utilities and refinery operators new flexibility when considering operational changes and expansion. The old New Source Review program has “deterred companies from implementing projects that would increase energy efficiency and decrease air pollution,” she said.

Potentially affected are hundreds of power plants, refineries, paper mills, chemical plants and factories built before 1977, when Congress amended the Clean Air Act requiring state-of-the-art controls on any new sources of pollution.

The older plants were exempted from being treated as new sources of pollution. But as companies started replacing outdated equipment to improve their efficiency, the Clinton administration began treating improvements as new pollution sources, requiring the expensive, state-of-the-art controls.

It pursued vigorous enforcement actions against companies reluctant to make the new anti-pollution investments, targeting in particular 43 power plants owned by nine utilities. Two of the utilities have settled, agreeing to install millions of dollars in new pollution controls at their plants.

Neither the new final rule or the proposed maintenance definition diminishes the agency’s willingness to pursue those cases, said John Peter Suarez, EPA’s assistant administrator for enforcement issues. “We are continuing to press ahead with the enforcement cases,” he said.

Whitman, however, suggested in testimony in March before a Senate committee that a prudent utility executive would await the results of a federal appeals court challenge to the existing regulations before settling with the government.

Jeff Holmstead, EPA’s assistant administrator in charge of air quality, insisted Friday that the new regulations would produce reductions in total pollution from the plants.

“There will be emissions reductions as a result of the rules we are adopting today,” he said.

Critics predicted just the opposite.

“More than 30,000 Americans die every year from power plant air pollution alone, and crippling the standards will only make things worse,” said John Walke, director of Natural Resources Defense Council’s clean air program.

A group of Northeastern states, led by New York and Connecticut, said they planned to file suit challenging the changes. In New York, Atty. Gen. Eliot Spitzer accused the administration of attacking the Clean Air Act with rules that would further degrade air quality in Northeastern and Mid-Atlantic states downwind from industrial plants.

“The Bush administration is again putting the financial interests of the oil, gas and coal companies above the public’s right to breathe clean air,” Spitzer said.

Sen. Joseph Lieberman, D-Conn., called on Whitman to resign in protest, saying her advice had been repeatedly overruled by a Bush White House intent on gutting environmental protections.

“Out of principle and protest, she should step down,” he said. “All this rule will do is extend the life of the dirtiest industrial plants and worsen the lives of citizens that breathe the pollution from their smokestacks every day.”

The rule changes, a priority of the White House, will:

l Establish a plantwide ceiling on pollution rather than a limit on what is allowed for each piece of equipment. A plant, for example, could install a boiler that produces more pollution as long as there is a corresponding reduction in pollution from another part of the operation.

l Allow refineries, paper mills, chemical plants and factories to use the two consecutive years of their greatest pollution over the past decade as a reference ceiling, meaning they won’t have to install new controls unless their emissions exceed that two-year high.

l Exempt plants from having to update pollution controls if the existing ones have been reviewed by the government during the past 10 years.

The agency also proposed allowing power plants, factories and refineries to treat as maintenance – exempt from new pollution controls – the replacement of equipment or other capital investment up to 20 percent of the plant’s total value.

The changes were sought by the utility, coal and oil industries, and were the subject of months of review at the White House. The electric utility and coal industries were both major donors to Republicans for the 2002 and 2000 elections.