Since 1970, the EPA concluded, cleaner air has saved the nation between $6 trillion and $50 trillion in health costs and lost productivity, at a cost of $523 billion. The ability to estimate these costs and benefits has greatly improved in recent years, as medical researchers have become better at measuring air pollution's impact.
"The Clean Air Act has been our nation's most successful, and controversial, environmental law," said Frank O'Donnell, president of the advocacy group Clean Air Watch. "Because of the Clean Air Act, Americans are healthier and living longer."
An analysis commissioned by the environmental group Clean the Air compares current deaths from power plant pollution with projected deaths under three proposals.
During the first two decades of this air quality push, a series of bipartisan compromises resulted in unleaded gasoline, cleaner cars and sulfur dioxide reductions through the acid rain program. While legislative efforts stalled after 1990, under President Bill Clinton officials administratively cut diesel emissions from trucks and tightened national smog and soot standards, while suing some of the dirtiest power companies for not cleaning up aging plants.
This flurry of activity inspired some utility executives to reach legal settlements with the Clinton administration and start "peace talks" with environmental groups about curbing several pollutants. But those efforts fell apart once Bush took office in 2001 and announced he opposed mandatory restrictions on carbon dioxide, wanted to relax requirements for upgrading old power plants and would take a different approach to regulating such pollutants as sulfur dioxide and nitrogen oxide.
Striving to make emissions cuts while keeping energy costs low, the administration proposed a cap-and-trade system that would over time reduce pollution from power plants, which account for 67 percent of the nation's sulfur dioxide emissions, 41 percent of its mercury pollution, 39 percent of its carbon dioxide emissions and 22 percent of its nitrogen oxide pollution.
Much of that pollution comes from a small number of aging plants: Fewer than half of the country's coal-fired utilities account for more than 90 percent of the industry's sulfur dioxide, nitrogen oxide and mercury pollution, said Emily Figdor, a spokeswoman for the advocacy group Clear the Air, adding half of the dirtiest plants increased their pollution levels since 1995.
Industry supports the Bush plan, and administration officials say it would be more effective than suing companies to enforce existing law or enacting rules that utilities would fight in court. About one-third of all Americans breathe air that does not meet federal standards today; under the White House proposal, 20 million of them would be breathing air that meets the guidelines within 15 years. Administration officials also note that new rules it imposed, which will virtually eliminate sulfur dioxide from the emissions of off-road diesel engines, will avert 12,000 premature deaths a year when fully phased in.
Thomas L. Sansonetti, assistant attorney general for the Justice Department's Environment and Natural Resources Division, calls the lawsuit-oriented approach his office has long pursued to enforce clean-air laws "the slow boat to China."
"Clear Skies is a simple, cost-effective way of reducing air pollution over a broad multi-state area," he said.
Under the cap-and-trade system, said utilities lobbyist Scott Segal, the dirtiest power plants are also the most likely to clean up quickly since they can reduce emissions significantly at a low cost.
But environmentalists and some state and local officials say other provisions in the Bush plan -- such as suspending the legal stick the government uses to force cleanups of aging utilities and the right of states to sue neighboring states over pollution -- will make it impossible for localities to meet new federal air quality standards for years.
"The provisions in Clear Skies are too little and too late," said John Paul, a Republican and the head of a regional air pollution agency in Dayton, Ohio, who testified before the Senate yesterday.
Two senators have competing proposals, both of which include provisions to curb carbon dioxide and push for steeper pollution cuts. Sen. James M. Jeffords (I-Vt.) would reduce nitrogen oxide, sulfur dioxide and mercury between 72 and 90 percent by 2009 while limiting carbon dioxide emissions to 1990 levels, while Sen. Thomas R. Carper (D-Del.) calls for slightly more modest cuts of all four pollutants by four to six years later.
The debate often comes down to "lives vs. jobs." Proponents of the Jeffords plan say that by 2020 it would save 100,000 more lives than the administration's bill; the White House counters the Jeffords measure would cost 272,000 jobs and drive electricity costs up 26 percent by 2025.
At the moment the Senate appears deadlocked; Carper, the White House's most likely potential Democratic ally, says that if the administration continues its "my way or the highway" approach, "you end up in a big traffic jam." But Connaughton said the president will lobby hard for his bill.
If it stalls, the White House will seek its 70 percent sulfur dioxide and nitrogen oxide cuts through the Clean Air Interstate Rule, which applies to 28 eastern and midwestern states. EPA plans to issue that rule, along with a separate one curbing mercury by 70 percent, in mid-March.
But regulations can be blocked more easily in court, and both sides say the nation should use this moment to clean up the skies as much as possible.
"Everybody has to think about some sort of compromise so we can get to an endgame and move on," said Robert M. Sussman, an EPA deputy administrator under Clinton who heads the environmental practice at Latham & Watkins law firm in Washington.