Clean Air Act is working, but multipollutant, multistate approach and stronger focus on results are needed to meet future challenges

WASHINGTON, Jan. 30, 2004 — Despite the progress that has been made toward cleaner air in this country, more needs to be done to improve the nation’s ability to confront future air pollution challenges, says a new report from the National Academies’ National Research Council.

The committee that wrote the report recommended that the U.S. Environmental Protection Agency use an approach that targets groups of pollutants instead of individual ones. Revised or new regulations also should consider how air pollution travels from state to state and across international borders.

Market-based approaches, such as emissions cap-and-trade programs – which set limits on the overall amount of emissions from industry but allow individual companies to buy and sell pollution “allowances” — should be used whenever practical and effective. And improved tracking of emissions is needed to accurately assess what populations are at the highest risk of health problems from pollution and to better measure the progress of pollution-control strategies.

The implementation of air quality regulations should be less bureaucratic — with more emphasis on results than process — and should be designed to protect ecosystems as well as people, the report says. Minority and low-income communities in dense urban settings may bear a disproportionate pollution burden, but these communities are not specifically targeted in the current Clean Air Act; they should be considered when regulations are revised, as should other environmental equity issues. Air quality standards also need to take into account climate change and the potential role of air pollutants in that change.

The committee grouped its proposals in five overarching and integrated recommendations that could be implemented in stages. EPA should form a task force to prepare a plan of action for implementing the report’s recommendations and determining what legislative action is required to do so. In the meantime, EPA should maintain current programs to reduce pollution in the United States so that the progress toward cleaner air continues.

At the request of Congress, the committee reviewed the effectiveness of the Clean Air Act and identified ways to improve its implementation. Overall, the committee found that the country’s air quality management system has made substantial progress since the act was passed in 1970 and the creation of EPA that same year. The act and its subsequent amendments target six major, or “criteria,” pollutants – carbon monoxide, nitrogen dioxide, sulfur dioxide, ozone, particulate matter, and lead – as well as some other hazardous pollutants known as air toxics. Other goals of the act include improving visibility in wilderness areas and national parks, preventing acid rain, and curbing the use of chemicals that deplete the ozone layer.

Air quality standards established under the Clean Air Act and state implementation plans to meet those standards helped drive the development of new technologies that led to substantial decreases in pollution, the committee said. Networks that monitor air quality have documented decreases in concentrations of the criteria pollutants, and most parts of the country have achieved the standards for sulfur dioxide, nitrogen dioxide, and carbon monoxide. Eastern states have experienced a decline in the amount of sulfate deposited by acid rain. And several analyses show that the Clean Air Act has had, and will continue to have, a net economic benefit.

The committee found several areas for improvement, however. It noted that standards tended to focus on single pollutants instead of using potentially more protective and cost-effective multipollutant strategies.

Groups of pollutants that are emitted from similar sources, that can be controlled with related technologies, or that have a similar impact on public health, ecosystems, visibility, or global climate change should be regulated in a single approach, the committee said.

For example, ozone, particulate matter, and a number of air toxics emitted by smokestacks and diesel engines could be targeted in the same regulation. Likewise, a single program could cover sulfur dioxide, mercury, and other pollutants that can be controlled at coal-fired power plants.

Future regulations also should be developed with greater consideration for how air pollution is transported from state to state and across international borders. Studies continue to indicate that air quality in a specific area can be influenced by pollutants that drift in from a different region, nation, or continent. The report says EPA should be given greater statutory responsibility and authority to deal with air quality problems in a regional, multistate context, especially since states obviously cannot control pollution that blows in from elsewhere.

Regulations for new cars and light trucks have greatly reduced vehicle emissions, but less progress has been made in reducing emissions from older heavy-duty diesel trucks, “nonroad” vehicles such as cranes and bulldozers, and malfunctioning automobiles. Also, while regulations governing new power plants and large factories have led to substantial reductions in emissions, many older plants remain a significant source of pollution, the report notes.

The committee said that the government’s current risk assessments and standard-setting programs do not address all of the hazardous air pollutants that may pose a significant risk to people or the environment. There is increasing evidence that some criteria pollutants may cause adverse health effects even at very low levels of exposure; in fact, for some pollutants it may be impossible to set a minimum threshold below which there is no public health risk. And EPA’s secondary standards, which aim to protect the environment, do not appear to be sufficient for protecting certain sensitive crops and ecosystems, the committee added.

Although concentrations of pollutants have decreased, many areas are not in compliance with newer, tougher standards for ozone and particulate matter, the committee noted. It added that the process states must follow to develop plans to meet standards has grown cumbersome and is too reliant on computer models whose ability to predict the effect of pollution-control strategies is uncertain. Rather than having to come up with multiple state implementation plans – each focused on a specific pollution standard — states should instead be asked to prepare an Air Quality Management Plan that encompasses all air quality activities in a single document, the report says.

Implementing the report’s recommendations would require additional resources that would be significant but not overwhelming, the committee said. Even a doubling of the approximately $200 million EPA spends each year on air quality monitoring and research would be less than 1 percent of the annual expenditures nationwide for complying with the Clean Air Act, the committee noted. Much interdisciplinary research will be needed to bolster the scientific understanding necessary to implement the report’s recommendations, which are intended to be adopted gradually so ongoing pollution prevention activities are not disrupted.

The study was sponsored by the U.S. Environmental Protection Agency. The National Research Council is the principal operating arm of the National Academy of Sciences and the National Academy of Engineering. It is a private, nonprofit institution that provides science and technology advice under a congressional charter. A committee roster follows.

Copies of Air Quality Management in the United States will be available later this winter from the National Academies Press; tel. 202-334-3313 or 1-800-624-6242 or on the Internet at

Division on Earth and Life Studies
Board on Environmental Studies and Toxicology
Committee on Air Quality Management in the United States

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