UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

 WASHINGTON D.C. 20460 

OFFICE OF THE ADMINISTRATOR 

SCIENCE ADVISORY BOARD 

April 7, 2008 

EPA-CASAC-08-009

Honorable Stephen L. Johnson 

Administrator 

U.S. Environmental Protection Agency 

1200 Pennsylvania Avenue, NW

Washington, DC 20460 

Subject: Clean Air Scientific Advisory Committee Recommendations Concerning the 

Final Rule for the National Ambient Air Quality Standards for Ozone 

Dear Administrator Johnson: 

 

The Clean Air Scientific Advisory Committee (CASAC or Committee), augmented by 

subject-matter-expert Panelists — collectively referred to as the CASAC Ozone Review Panel — 

met via a public advisory teleconference on March 28, 2008. The purpose of this conference call 

was to hold follow-on discussions concerning the Final Rule for the National Ambient Air Quality Standards (NAAQS) for ozone, which the Agency published on March 12, 2008. The Ozone 

Panel roster is attached as Appendix A. 

In our most-recent letters to you on this subject — EPA-CASAC-07-001, dated October 

24, 2006, and EPA-CASAC-07-002, dated March 26, 2007 — the CASAC unanimously recommended selection of an 8-hour average Ozone NAAQS within the range of 0.060 to 0.070 parts 

per million for the primary (human health-based) Ozone NAAQS. Moreover, with regard to the 

secondary (welfare-related) ozone standard, the Committee recommended an alternative secondary standard of cumulative form that is substantially different from the primary Ozone NAAQS 

in averaging time, level and form — specifically, the W126 index within the range of 7 to 15 

ppm-hours, accumulated over at least the 12 “daylight” hours and the three maximum ozone 

months of the summer growing season. 

The CASAC now wishes to convey, by means of this letter, its additional, unsolicited advice with regard to the primary and secondary Ozone NAAQS. In doing so, the participating 

members of the CASAC Ozone Review Panel are unanimous in strongly urging you or your successor as EPA Administrator to ensure that these recommendations be considered during the 

next review cycle for the Ozone NAAQS that will begin next year. 
March 12, 2008 was the first time since 1997 that the primary standard for ozone was updated, and the CASAC commends you for taking a step in the right direction by lowering the primary eight-hour ozone standard from 0.08 parts per million to 0.075 ppm. The Committee is 

also pleased that the Agency has abandoned the artificial use of only two decimal places for the 

standard, as reported in ppm. As noted in the CASAC’s previous letters to you on this subject, 

this practice has allowed the rounding-down of ozone concentrations as high as 0.084 ppm to 

meet the previous standard of 0.08 ppm.

Nevertheless, the members of the CASAC Ozone Review Panel do not endorse the new 

primary ozone standard as being sufficiently protective of public health. The CASAC — as the 

Agency’s statutorily-established science advisory committee for advising you on the national 

ambient air quality standards — unanimously recommended decreasing the primary standard to 

within the range of 0.060–0.070 ppm. It is the Committee’s consensus scientific opinion that 

your decision to set the primary ozone standard above this range fails to satisfy the explicit stipulations of the Clean Air Act that you ensure an adequate margin of safety for all individuals, including sensitive populations. 

As you are well aware, numerous medical organizations and public health groups have 

also expressed their support of these CASAC recommendations. We sincerely hope that, in light 

of these scientific judgments and the supporting scientific evidence, you or your successor will 

select a more health-protective primary ozone standard during the upcoming review cycle. 

The CASAC was also greatly disappointed that you failed to change the form of the secondary standard to make it different from the primary standard. As stated in the preamble to the 

Final Rule, even in the previous 1996 ozone review, “there was general agreement between the 

EPA staff, CASAC, and the Administrator, ... that a cumulative, seasonal form was more biologically relevant than the previous 1-hour and new 8-hour average forms (61 FR 65716)” for the 

secondary standard. Therefore, in both the previous review and in this review, the Agency staff 

and its advisors agreed that a change in the form of the secondary standard was scientifically 

well-justified. 

The CASAC was pleased to see that the EPA Deputy Administrator clearly articulated a 

robust scientific defense of this position when he responded to Ms. Susan Dudley of the Office 

of Management and Budget (OMB) in a memorandum dated March 7, 2008 that, “In light of the 

available information, EPA believes that ozone-related effects on vegetation are clearly linked to 

cumulative, seasonal exposures and are not appropriately characterized by the use of a short-term

(8-hour) daily measure of ozone exposure.” However, the Committee was disappointed and surprised that written correspondence from OMB to the Agency apparently thwarted the opportunity 

to take a major step forward in setting a separate secondary ozone standard that is different in 

form from the primary standard. The CASAC is particularly dismayed at the suggestion that setting a secondary NAAQS that is different from the primary NAAQS is somehow against the law 

— which is not only at odds with a plain-language reading of the Clean Air Act but is also contrary to the Agency’s previous actions in setting a separate secondary standard for the initial 

NAAQS for both particulate matter and sulfur oxides, the latter of which (i.e., for SO2) remains 

in effect.

2
Unfortunately, this scientifically-sound approach of using a cumulative exposure index 

for welfare effects was not adopted, and the default position of using the primary standard for the 

secondary standard was once again instituted. Keeping the same form for the secondary Ozone 

NAAQS as for the primary standard is not supported by current scientific knowledge indicating 

that different indicator variables are needed to protect vegetation compared to public health. The 

CASAC was further disappointed that a secondary standard of the W126 form was not considered from within the Committee’s previously-recommended range of 7 to 15 ppm-hours. The 

CASAC sincerely hopes that, in the next round of Ozone NAAQS review, the Agency will be able 

to support and establish a reasonable and scientifically-defensible cumulative form for the secondary standard. 

We recognize that it will be difficult to bring the country into compliance with lower 

primary and secondary ozone standards. However, the fact that it is difficult does not mean that 

it is not achievable. The substantial progress made to date in lowering ambient ozone levels testifies to this. The CASAC believes that, in the future, we as a nation can devise effective and 

efficient ways to decrease ambient ozone concentrations to a sufficiently health- and welfareprotective level. However, in order to support this vital objective, EPA’s recent record of not 

adequately funding ozone research must end. The CASAC strongly supports the provision of 

additional funds to address the research needs that Agency staff have identified as being necessary for informing the process of setting both the primary and secondary ozone standards. 

As always, the members of the CASAC wish the Agency well in our crucial — and mutual — efforts to protect both human health and the environment. 

 

 Sincerely,

 /Signed/ 

Dr. Rogene F. Henderson, Chair 

 Clean Air Scientific Advisory Committee 

Attachment: Appendix A

3
NOTICE 

This report has been written as part of the activities of the U.S. Environmental 

Protection Agency’s (EPA) Clean Air Scientific Advisory Committee (CASAC), a Federal advisory committee administratively-located under the EPA Science Advisory Board 

(SAB) Staff Office that is chartered to provide extramural scientific information and advice to the Administrator and other officials of the EPA. The CASAC is structured to 

provide balanced, expert assessment of scientific matters related to issue and problems 

facing the Agency. This report has not been reviewed for approval by the Agency and, 

hence, the contents of this report do not necessarily represent the views and policies of

the EPA, nor of other agencies in the Executive Branch of the Federal government, nor 

does mention of trade names or commercial products constitute a recommendation for 

use. CASAC reports are posted on the SAB Web site at: http://www.epa.gov/casac. 

4
Appendix A – Roster of the CASAC Ozone Review Panel 

U.S. Environmental Protection Agency 

Science Advisory Board (SAB) Staff Office 

Clean Air Scientific Advisory Committee (CASAC) 

CASAC Ozone Review Panel

CASAC MEMBERS 

Dr. Rogene Henderson (Chair), Scientist Emeritus, Lovelace Respiratory Research Institute, Albuquerque, NM 

Dr. Ellis Cowling, University Distinguished Professor At-Large, Emeritus, Colleges of Natural Resources and Agriculture and Life Sciences, North Carolina State University, Raleigh, NC 

Dr. James D. Crapo [M.D.], Professor, Department of Medicine, National Jewish Medical and Research 

Center, Denver, CO 

Dr. Douglas Crawford-Brown,

§

 Director, Carolina Environmental Program; Professor, Environmental 

Sciences and Engineering; and Professor, Public Policy, Department of Environmental Sciences and Engineering, University of North Carolina at Chapel Hill, Chapel Hill, NC 

Dr. Donna Kenski,

†

 Director of Data Analysis, Lake Michigan Air Directors Consortium (LADCO), 

Rosemont, IL 

Dr. Armistead (Ted) Russell,

§

 Georgia Power Distinguished Professor of Environmental Engineering, 

Environmental Engineering Group, School of Civil and Environmental Engineering, Georgia Institute of 

Technology, Atlanta, GA 

Dr. Jonathan Samet [M.D.],

†

 Professor and Chairman, Department of Epidemiology, Bloomberg School 

of Public Health, Johns Hopkins University, Baltimore, MD 

PANEL MEMBERS 

Dr. John Balmes, Professor, Department of Medicine, University of California San Francisco, University

of California – San Francisco, San Francisco, California 

Dr. William (Jim) Gauderman, Professor, Department of Preventive Medicine, School of Medicine, 

University of Southern California, Los Angeles, CA 

Dr. Paul J. Hanson, Senior Research and Development Scientist, Environmental Sciences Division, Oak 

Ridge National Laboratory (ORNL), Oak Ridge, TN 

Dr. Jack Harkema,* Professor, Department of Pathobiology, College of Veterinary Medicine, Michigan 

State University, East Lansing, MI 

Dr. Philip Hopke, Bayard D. Clarkson Distinguished Professor, Department of Chemical Engineering, 

Clarkson University, Potsdam, NY 

A-1
Dr. Michael T. Kleinman, Professor, Department of Community & Environmental Medicine, University 

of California – Irvine, Irvine, CA 

Dr. Allan Legge, President, Biosphere Solutions, Calgary, Alberta, Canada 

Dr. Morton Lippmann, Professor, Nelson Institute of Environmental Medicine, New York University 

School of Medicine, Tuxedo, NY 

Dr. Frederick J. Miller, Consultant, Cary, NC 

Dr. Maria Morandi, Assistant Professor of Environmental Science & Occupational Health, Department 

of Environmental Sciences, School of Public Health, University of Texas – Houston Health Science Center, Houston, TX 

Dr. Charles Plopper, Professor, Department of Anatomy, Physiology and Cell Biology, School of Veterinary Medicine, University of California – Davis, Davis, California 

Mr. Richard L. Poirot, Environmental Analyst, Air Pollution Control Division, Department of Environmental Conservation, Vermont Agency of Natural Resources, Waterbury, VT 

Dr. Elizabeth A. (Lianne) Sheppard, Research Professor, Biostatistics and Environmental & Occupational Health Sciences, Public Health and Community Medicine, University of Washington, Seattle, WA 

Dr. Frank Speizer, Edward Kass Professor of Medicine, Channing Laboratory, Harvard Medical School, 

Boston, MA 

Dr. James Ultman, Professor, Chemical Engineering, Bioengineering Program, Pennsylvania State University, University Park, PA

Dr. Sverre Vedal, Professor of Medicine, Department of Environmental and Occupational Health Sciences, School of Public Health and Community Medicine, University of Washington, Seattle, WA 

Dr. James (Jim) Zidek, Professor, Statistics, Science, University of British Columbia, Vancouver, BC, 

Canada 

Dr. Barbara Zielinska, Research Professor, Division of Atmospheric Science, Desert Research Institute, 

Reno, NV 

SCIENCE ADVISORY BOARD STAFF 

Mr. Fred Butterfield, CASAC Designated Federal Officer, 1200 Pennsylvania Avenue, N.W., Washington, DC, 20460, Phone: 202-343-9994, Fax: 202-233-0643 (butterfield.fred@epa.gov) 

§

Dr. Crawford-Brown was appointed to the Clean Air Scientific Advisory Committee in October 2006; Dr. Russell 

was a member of the CASAC Ozone Review Panel and was appointed to the Clean Air Scientific Advisory Committee in October 2006. 

†

Dr. Kenski and Dr. Samet were appointed to the Clean Air Scientific Advisory Committee in October 2007. 

*Dr. Harkema did not participate in this current CASAC Ozone Review Panel activity.

A-2