Every five years, the EPA reviews its listing of six major air pollutants including ozone and particulate matter. For about 30 years, the Clean Air Act has required an independent committee of agency scientists and outside experts to review the listing.

The committee then submitted its recommendations to the agency for review.

The EPA will now replace the review with a more narrowly focused policy assessment. It says this process will connect the agency's scientific assessment and the judgments the agency's administrator must make in air pollutant regulation decisions.

"EPA is committed to a timely and transparent process that uses the most up-to-date science available," EPA Deputy Administrator Marcus Peacock said on a teleconference. "Everyone has found the current process is inefficient and current delays are unacceptable ."

The new process will "separate out those scientific judgments that scientists and staff scientists ... would make, from those judgments that policy makers would make," said Peacock. He said the new process would make scientific and policy assessments more transparent.

But environmentalists and health advocates said the new process will give more power to political appointees, who had previously weighed the science only at the end of the process.

"One of the (EPA's) purposes of changing this process has been to involve the political decisions far earlier than they ever have been before," Janice Nolen, director of national policy and advocacy at the American Lung Association, said in a telephone interview.

"Consequently it's really going to make it harder to know what the science is versus what the politics are."

Frank O'Donnell, president of Washington, D.C.-based advocacy group Clean Air Watch said it would also open up the process to more influence from industry lobbyist, such as the battery industry which asked the EPA last summer to take lead off the list of air pollutants.

This week, the EPA said it will weigh the removal of lead from the list of pollutants. The agency said its review on ozone, which is ongoing, will not be affected by the process change.