At the suggestion of the power industry, the Ehrlich administration is proposing to exempt about half of Maryland's coal-fired power plants from some of the governor's new rules on air-pollution control, according to a draft of the regulations released yesterday.

Gov. Robert L. Ehrlich Jr. held a news conference in November to announce that he would soon be issuing the Maryland Clean Power Rule, which he said would be "the most sweeping, far-reaching clean air rule ever promulgated in Maryland."

But in releasing the proposed regulations yesterday, officials with the Maryland Department of the Environment said they might exempt generators at three of the state's six major coal-fired electricity plants from the proposal's sulfur dioxide limits, in part to save power companies money.

The three smaller plants might not have enough land to allow affordable construction of large pollution-control devices called scrubbers, MDE officials said.

John Quinn, a lobbyist for Constellation Energy who heads a state panel advising the administration on the rules, said he suggested to the MDE that it would be impractical and overly expensive to demand scrubbers on every power plant.

"We said that it's hard to imagine the same level of control on every [plant] because there are cost and design considerations," Quinn said yesterday after chairing a meeting of the MDE's Air Quality Advisory Council. Constellation is the largest owner of power plants in Maryland.

Quinn was in the news last month when The Sun reported that he had worked behind the scenes with former Constellation employees who are now at the MDE to lobby against a bill to control air pollution.

Quinn sent a draft letter arguing against the legislation to state Environment Secretary Kendl P. Philbrick, who adopted the language verbatim, signed it as the official position of his agency and faxed it to a key state senator.

Environmentalists said yesterday that after last year's efforts against the bill, they are pleased that the administration is promoting air-pollution controls through regulations. But they complained about the "gaping loophole" created by the exemption, saying the three smaller power plants produce about a third of the sulfur dioxide air pollution pouring from the state's coal generators. The chemical forms tiny particles linked to hundreds of asthma and heart attacks annually in Maryland.

"It looks like the governor's rule got hit by an iceberg before it left the dock," said Edward Osann, an environmental consultant with Washington-based Potomac Resources Inc. "Sulfur emissions are a direct and present threat to public health, and we should be using the best control technology to reduce them."

Ehrlich's clean-air rules, which could be adopted this spring, propose to reduce sulfur dioxide pollution by 85 percent, nitrogen oxide pollution by 69 percent and mercury pollution by 70 percent, all by 2010.

Those reductions are similar to what the federal government said Maryland would achieve through regional clean-air rules released by the Bush administration in March, although Ehrlich's goal is to achieve the reduction in mercury sooner.

Tad Aburn, manager of regulation development at the MDE, said the possible exemption for smaller plants from the requirement to cut their sulfur emissions by 85 percent by adding scrubbers doesn't mean those plants will do nothing.

The MDE will examine those plants case by case and decide what kind of alternative pollution-control systems would be practical, given the cost and the amount of land around the plants, Aburn said.

"This is not going to be a free pass by any stretch of the imagination," said Thomas Snyder, director of air programs at the MDE. "The issue is the size of the scrubbers and whether you can fit them into these spaces."

Scrubbers are large, box-shaped pollution-control devices, invented more than a quarter century ago, that spray lime in a water solution into the gases emitted by boilers to remove sulfur dioxide. They are sometimes eight stories tall, spread over more than an acre and cost up to $100 million each.

Instead of scrubbers, the MDE might decide to require the smaller plants to install alternative equipment or to make other changes that would substantially reduce sulfur pollution, Snyder said.

None of the six major coal-fired power plants in Maryland has scrubbers, but the three largest might have to install them to meet the sulfur limits in the Ehrlich air-pollution rules, MDE officials said.

"Every coal-fired power plant should be equipped with a scrubber or be on a schedule to install scrubbers or similar equipment," said Bill Becker, executive director of the State and Territorial Air Pollution Program Administrators, a Washington-based nonprofit group that represents environmental regulators from around the country.

"It's incredibly important to reduce sulfates, because sulfates kill people," he said.

Brad Heavner, executive director of the Maryland Public Interest Research Group, said it was wrong for the administration to exclude environmental groups from the 10-member advisory committee, which has been discussing the air-pollution regulations while picking Constellation's lobbyist as its chairman.

"It's not a surprise that they would have an industry guy on the panel, but having him chair the committee? In what world is that ethical?" Heavner said.

Quinn said that he has been discussing the proposed regulations with the MDE since at least September but that he would recuse himself from any vote on the advisory panel, which also includes a physician and a public health expert.