Critical considerations in evaluating scientific evidence of health effects of ambient ozone: a conference report

Abstract

The U.S. Environmental Protection Agency (EPA), under the authority of the Clean Air Act (CAA), is required to promulgate National Ambient Air Quality Standards (NAAQSs) for criteria air pollutants, including ozone. Each NAAQS includes a primary health-based standard and a secondary or welfare-based standard. This paper considers only the science used for revision of the primary standard for ozone in 2008. This paper summarizes deliberations of a small group of scientists who met in June 2007 to review the scientific information informing the EPA Administrator’s proposed revision of the 1997 standard. The Panel recognized that there is no scientific methodology that, in the absence of judgment, can define the precise numerical level, related averaging time, and statistical form of the NAAQS. The selection of these elements of the NAAQS involves policy judgments that should be informed by scientific information and analyses. Thus, the Panel members did not feel it appropriate to offer either their individual or collective judgment on the specific numerical level of the NAAQS for ozone. The Panel deliberations focused on the scientific data available on the health effects of exposure to ambient concentrations of ozone, controlled ozone exposure studies with human volunteers, long-term epidemiological studies, time- series epidemiological studies, human panel studies, and toxicological investigations. The deliberations also dealt with the issue of background levels of ozone of nonanthropogenic origin and issues involved with conducting formal risk assessments of the health impacts of current and prospective levels of ambient ozone. The scientific issues that were central to the EPA Administrator’s 2008 revision of the NAAQS for ozone will undoubtedly also be critical to the next review of the ozone standard. That review should begin very soon if it is to be completed within the 5-year cycle specified in the CAA. It is hoped that this Report will stimulate discussion of these scientific issues, conduct of additional research, and conduct of new analyses that will provide an improved scientific basis for the policy judgment that will have to be made by a future EPA Administrator in considering potential revision of the ozone standard.

Keywords::

• Ozone
• air quality
• national ambient air quality standards
• air pollution
• respiratory effects
• clean air act
• risk assessment

Acknowledgments

The Working Conference held in Rochester, New York, was organized by Professor Mark J. Utell at the University of Rochester. The organization and conduct of the conference were greatly facilitated by capable support from Michael Terry, Patricia Noonan, and Eric Rushton, University of Rochester. Dr. Michael Brauer, University of British Columbia, participated in several sessions of the Conference and his valuable contributions to the discussion and the manuscript are acknowledged. Tom Rickey, University of Rochester, and Dr. Ricki Lewis, CareNet Medical Group, provided valuable editorial assistance. Mildred Morgan, who works with Dr. Roger McClellan, provided valuable assistance in preparing the final report.

Declaration of interest: The Working Conference and preparation of this report were funded by the American Petroleum Institute in the form of a grant to Professor Utell. Each of the participants was reimbursed for their travel expenses and received an honorarium for participation in the Conference. The employment affiliate on each of the participants is shown at the beginning of the report. However, it should be emphasized that each individual’s participation was on a professional basis and, thus, the input to the Conference discussions and to this report are solely the responsibility of the individual participants.