HARRISBURG - The Corbett administration has for the second time in two weeks rescinded a Rendell-era environmental rule that imposed tougher restrictions on natural-gas drilling.

The administration's latest action applies to air pollution from machinery at Marcellus Shale drilling sites.

Under the criteria Gov. Ed Rendell set out in December, smaller sources of air pollution, such as exhaust from compressor engines, were to be considered as "one large source of air pollution." As such, drillers would be required to install pollution controls for that equipment.

Environmentalists say allowing smaller sources of pollution to be considered individually would likely exempt them from regulation.

"By rescinding the policy, DEP gives up a valuable tool for evaluating and reducing air pollution," said Jan Jarrett, president of PennFuture, a statewide environmental advocacy group.

Last week, the Corbett administration rescinded a policy enacted in October that required the state Department of Conservation and Natural Resources to perform an environmental-impact analysis before any drilling in state forests and parkland where the state does not own the mineral rights under the land.

Jarrett accused the Corbett administration of "bending over backward" to accommodate the gas-drilling industry's "wish list."

Gov. Corbett's spokesman, Kevin Harley, did not return a phone call or e-mail seeking comment.

In a notice published in the Pennsylvania Bulletin, the state publication where rules and regulations must appear before they become effective, the Department of Environmental Protection wrote that it wanted to open the policy to a "comprehensive public-comment period . . . to guide the department on what, if any, guidance or action might be taken" on this policy on air pollution.

Jarrett said that there had been a public-comment period and that the agency did not need to rescind the interim policy in order to seek additional comments.

A DEP spokeswoman said the publication of the notice did not change any regulations and simply opened the process up to more public comment.

"This doesn't change the way we do business," spokeswoman Katy Gresh said. "We look at every case specifically and apply the necessary factors and legal criteria. We haven't lifted anything."