Despite three decades of progress, the existing air-quality laws are inadequate to prevent pollution that threatens the environment and human health, the nation's top scientific advisory group concluded Thursday.
The panel, the National Research Council of the National Academies, said it was particularly concerned about ozone, an ingredient of smog that has proved difficult to curtail, and fine soot, which has been shown to be especially harmful.
State and local authorities in many polluted regions are increasingly finding that even if they control local emissions, they can end up violating federal standards because of pollution drifting from sources outside their jurisdiction.
And even though individual smokestacks and tailpipes are generally getting cleaner as a result of clean-air laws, their numbers are growing rapidly because of economic and population growth.
"Even if you say, "Let's not get any better than today,' you're still going to have to do a lot more because the economy is going to grow and we'll have more emissions," said Dr. William L. Chameides, the chairman of the 25-member panel of experts in environmental science, law, engineering and public policy.
In some cases existing rules can be modified, the report went on, but Congress also will have to pass new legislation, including revisions to the 1970 Clean Air Act.
It noted that the federal Environmental Protection Agency has only limited authority under the act to deal with pollution in one state that blows into another, putting the downwind region in violation of federal laws.
John D. Graham, an administrator at the White House Office of Management and Budget, said the report would have "a big long-term impact on how ecology and public health shape clean-air policy."
Other administration officials and lawmakers said it was a helpful technical guide, but added that political fights were still likely to impede adoption of its recommendations.
The report avoided direct endorsements or criticisms of policies of the Bush administration or its critics, instead promoting general approaches that the experts said were necessary to make progress in the long run.
For example, the panel strongly supported expanding "cap and trade" strategies for cutting pollution, in which a national or regional limit is set and companies that do better than the standard can sell credits to those that cannot.
The report said this might be the best way to reduce emissions from sources not covered by existing rules, like old power plants that were largely exempted from Clean Air Act revisions in 1990.
Also, to ensure that the benefits of environmental laws continue to outweigh the costs, the panel said, wherever possible a single set of rules should control various kinds of emissions from particular sources, like power plants. In the past, most pollutants have been controlled in isolation.
These recommendations essentially constituted an endorsement of the mechanism at the heart of a variety of proposed laws for power plant cleanups. These include President Bush's plan to limit three kinds of emissions and those of several bipartisan groups of lawmakers seeking quicker cuts and limits on a fourth emission, carbon dioxide. Carbon dioxide is the main heat-trapping greenhouse gas linked by most scientists to global warming.
On the question of climate change, the panel came closest to choosing sides. "Multipollutant approaches that include reducing emissions contributing to climate warming as well as air pollution may prove to be desirable," it said. Bush has opposed mandatory restrictions in greenhouse gases.