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Date: March 16, 2006
Contacts: Bill Kearney, Director of Media Relations
Megan Petty, Media Relations Assistant
Office of News and Public Information
202-334-2138; e-mail <>


Scientific Basis for California's Tougher Emissions Standards Valid;
Options Proposed for Improving Other States' Adoption of California Regulations

WASHINGTON -- The basis for California's pioneering role in setting emissions standards for cars, trucks, and off-road equipment is scientifically valid, says a new congressionally mandated report from the National Academies' National Research Council. California's standards -- which are generally stricter than the federal government's -- are still needed because of persistent pollution in parts of the state, said the committee that wrote the report. 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 U.S. Environmental Protection Agency, 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 says. 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 said.

The report 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 State and Federal Standards for Mobile Source Emissions will be available from the National Academies Press; tel. 202-334-3313 or 1-800-624-6242 or on the Internet at Reporters may obtain a pre-publication copy from the Office of News and Public Information (contacts listed above).

[ This news release and report are available at ]

Division on Earth and Life Studies
Board on Environmental Studies and Toxicology

Committee on State Practices in Setting Mobile Source Emissions Standards

David T. Allen (chair)
Melvin Gertz Regents Professor in Chemical Engineering, and
Center for Energy and Environmental Resources
University of Texas

John C. Bailar III1
Professor Emeritus
Department of Health Studies
University of Chicago

Hugh Ellis
Department of Geography and Environmental Engineering and Department of Environmental Health Sciences
Johns Hopkins University

Alison Geyh
Assistant Professor
Bloomberg School of Public Health
Johns Hopkins University

David L. Greene
Corporate Fellow
Oak Ridge National Laboratory
Oak Ridge, Tenn.

James Lents
Environmental Policy and Corporate Affiliates Program
University of California

Gary Marchant
Professor of Law, and
Executive Director and Faculty Fellow
Center for the Study of Law, Science, and Technology
College of Law
Arizona State University

Virginia McConnell
Senior Fellow
Quality of the Environment Division
Resources for the Future
Washington, D.C.

Alison K. Pollack
Novato, Calif.

Harold Schock
Department of Mechanical Engineering
Michigan State University
East Lansing

Karl J. Springer2
Vice President for Automotive Products and Emissions Research
Southwest Research Institute (retired)
San Antonio


K. John Holmes
Study Director

1 Member, Institute of Medicine
2 Member, National Academy of Engineering