Whitman, the former New Jersey governor, who at times seemed to be battling environmentalists and business groups at the same time, expressed pride in what she had been able to accomplish at the agency.

“It has been a singular honor to be entrusted with the responsibility to lead the EPA in its effort to leave America's air cleaner, its water purer, and its land better protected than it was when this administration took office,” she said.

“Our work has been guided by the strong belief that environmental protection and economic prosperity can and must go hand-in-hand, that the true measure of the value of any environmental policy is in the environmental results it produces. I am pleased that the EPA has built an enviable record of success that will result in significant improvements to the state of our Nation's treasured environment.”

Although Whitman had been at odds with the White House, particularly on President Bush’s decision to back away from support of a global warming treaty, sources said the administration did not pressure her to leave.

Instead, observers expect other resignations as cabinet members decide whether they want to leave or remain with the administration through next year’s re-election campaign. White House Press Secretary Ari Fleischer announced his resignation Monday, citing reasons along those lines.

Despite recent criticism of the administration’s policy on clean air regulations, Whitman’s letter argued that America’s air would be cleaner as a result of her term in office.

“Our actions to reduce pollution from non-road diesel engines represent, in the words of one major environmental organization, the ‘biggest public health step’ in more than 20 years,” she said in her letter to the president. “Our landmark Clean School Bus USA initiative means that every public school student in America should be riding low emission school buses by 2010.

“Our aggressive and effective efforts to enforce the Nation's environmental laws have achieved some of the largest Clean Air Act settlements in history. This record will only be enhanced by the eventual passage of the administration's proposed Clear Skies Act of 2003, your far-reaching proposal to reduce pollution from the Nation's power plants.”

She also cited EPA's Watershed Initiative as expanding watershed-based water protection policy across the country. “The Agency's innovative Water Quality Trading program will help address the growing problem of non-point source pollution,” she noted. “EPA's plan for cleanup of the Hudson River has set a new standard for restoring waterways that have been threatened by decades of abuse.”

She said improvements to the rules governing Concentrated Animal Feeding Operations will protect surface water by requiring reductions of at least 25 percent in run-off of nitrogen and phosphorous from those large agricultural operations.

“America's land will be better protected. Our success in enacting long-overdue Brownfields legislation is already accelerating the reclamation of abandoned parcels of land in hundreds of communities across America. The enactment of this legislation, after nearly a decade of partisan wrangling, is a testament to your commitment to change the way things are done in Washington.”

e-mail: flaws@primediabusiness.com