Government Study Finds California's Emissions Standards Scientifically Sound

The basis for California's pioneering role in setting emissions standards for cars, trucks, and off-road equipment is scientifically valid, according to a new congressionally mandated report released on March 16 by the National Academies' National Research Council.

In a setback for automakers, the committee that wrote the report found that California's standards -- which are generally stricter than the federal government's -- are still needed because of persistent pollution in parts of the state. California's standards also tend to spur the development of better emission-control technologies that benefit the rest of the nation, the committee noted.

It did not comment on the state's recent standards for greenhouse-gas emissions because they were adopted while the report was in progress, and because there are no federal standards to which they can be compared.

The committee examined emissions standards governing so-called mobile sources, which include cars and light- and heavy-duty trucks; diesel-powered cranes, bulldozers, and tractors; and equipment such as lawnmowers that run on small gasoline engines. The committee concluded that despite the substantial progress in reducing emissions from mobile sources nationwide, more needs to be done to attain federal air-quality standards in many parts of the country.

In 1967 Congress exempted California from a provision in the newly passed Clean Air Act requiring federal emissions standards to pre-empt state standards. It did so because California had been at the forefront of regulating vehicle emissions and because the state had heavy smog linked to the vast number of cars on its roads. According to the committee, California has used its authority as Congress intended, by implementing more aggressive measures than the rest of the country and serving as a laboratory for technological innovation. The state's technical procedures for setting emissions standards are similar to those of the EPA, the report notes.

Congress later allowed other states to copy California's emissions standards. The process by which states adopt California rules should be improved, with EPA playing a role, the report states. Like California, other states adopt tougher mobile-source emissions regulations to help meet EPA's air-quality standards. However, because colder weather or variations in fuel composition can make cars or their emissions-control equipment operate differently, automakers often claim difficulty complying with California rules when they are adopted elsewhere, and legal disputes ensue.

The committee said EPA could alleviate such disputes either by providing formal but nonbinding guidance or by being given the power to grant or, in limited circumstances, deny a waiver allowing states to adopt California standards. The committee could not agree on which of these approaches would be more effective. It noted that defining EPA's role in the state adoption process is a policy decision that goes beyond scientific concerns.

Currently, California is required to obtain an EPA waiver for each new mobile-source emissions standard. To speed up the waiver process, which can take several years, the committee recommended that EPA expedite waiver requests it considers noncontroversial and place a time limit on decisions for more controversial requests. Since new regulations cannot be implemented for two years after their adoption by the state, a time limit of that length would be appropriate for the waiver process, the committee stated.The report, State and Federal Standards for Mobile Source Emissions, can be accessed at

This article originally appeared in the 03/01/2006 issue of Environmental Protection.

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