UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

 WASHINGTON D.C. 20460 

 

OFFICE OF THE ADMINISTRATOR 

SCIENCE ADVISORY BOARD 

September 15, 2010 

EPA-COUNCIL-10-005 

The Honorable Lisa P. Jackson 

Administrator 

U.S. Environmental Protection Agency 

1200 Pennsylvania Avenue, N.W. 

Washington, D.C. 20460 

Subject: Review of Revised PM2.5 Emissions and Modeling Estimates for the 

Second Prospective Study of Benefits and Costs of the Clean Air Act 

Dear Administrator Jackson: 

The Air Quality Modeling Subcommittee (AQMS) of the Advisory Council on Clean Air 

Compliance Analysis (Council) held a public teleconference on August 11, 2010 to further evaluate 

the Agency’s estimates of atmospheric fine particulate matter (PM2.5) concentrations corresponding 

to scenarios prepared for the Second Section 812 Prospective Study of costs and benefits of the Clean 

Air Act. During meetings in February and March, the AQMS learned of potential biases in the 

estimates of primary PM2.5 and was briefed on the Agency’s plans to correct processing errors in the 

PM2.5 emissions inventories and to adjust modeled PM2.5 concentrations. In a June 2010 report 

(EPA-COUNCIL-10-002), the AQMS recommended that the use and application of the Modeled 

Attainment Test Software (MATS) for the PM2.5 adjustments be more transparent and 

comprehensively described. In response to the Council’s request, the Agency prepared additional 

documentation on the adjustment procedures and results. The purpose of the August teleconference 

was to evaluate this additional information and offer advice on its clarity and appropriateness for the 

Second Prospective Study. 

The AQMS was provided a memorandum (dated June 14, 2010) that described the 

process used to adjust the primary PM2.5 estimates and the outputs from the Community Scale 

Air Quality Model (CMAQ), as well as application of MATS to adjust CMAQ outputs using 

monitoring data. In addition, the memorandum included 3 attachments showing adjustments to 

underlying data (from the 1990 National Emissions Inventory), and stacked bar graphs showing 

total and speciated PM2.5 concentrations estimated by CMAQ and after application of MATS. 

The AQMS found the set of four memoranda to be a clear and concise description of the 

PM2.5 adjustments, and provided the desired information. We compliment the Agency on the 

approaches taken to deal with the data processing issues identified previously, and their 

responsiveness to our concerns. Given the significant contribution of PM2.5 to the overall 

estimates of benefits from the Clean Air Act, it is especially important to clearly document the 
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steps leading up to the estimates of PM2.5 concentrations in the various scenarios. These 

memoranda are a valuable contribution to the record, and will provide the Council with a more 

complete foundation for their review of the Second Prospective Study. 

Two issues were identified during the August 11 teleconference. First, AQMS members 

identified some results from the MATS-processed CMAQ particulate matter concentration 

simulations (e.g., crustal material concentrations for Tucson, Miami, and Philadelphia) that were 

not readily explained, and could use further discussion. Second, the air quality modeling-MATS 

system is very complex, and its application introduces a number of uncertainties. The Section 

812 report should provide a comprehensive explanation of such uncertainties, with particular 

attention to the air quality modeling results for PM2.5. In particular, the stacked bar charts should 

provide a sense of which PM2.5 components are more/less certain, and this sense of uncertainty 

should be carried over to the discussion of benefits. For example, the crustal material has a 

relatively large uncertainty compared to sulfate, but if the health impacts are more associated 

with non-crustal components, this should be noted in the 812 report. 

The AQMS appreciates the information contained in the set of four memoranda from 

Agency contractors, but recommends that a single cover memorandum be prepared by the 

Agency to summarize the content of the four memoranda, explain why they were prepared, and 

discuss the related uncertainties in the process and results. This Agency cover memorandum 

(and the four contractor memoranda reviewed here) should be referenced in the integrated 812 

report, as well as linked to the CMAQ air quality modeling report that was reviewed previously 

by the AQMS. These steps would ensure that future readers of the 812 technical reports have a 

more comprehensive understanding of the air quality modeling process and the results. Further, 

it would document the emissions processing error and how it was corrected. 

 

 Sincerely, 

 

/Signed/ /Signed/ 

Dr. James K. Hammitt, Chair Dr. Armistead Russell, Chair 

Advisory Council on Clean Air Air Quality Modeling Subcommittee 

 Compliance Analysis 
NOTICE 

This report has been written as part of the activities of the EPA’s Advisory Council on Clean Air 

Compliance Analysis (Council), a federal advisory committee administratively located under the 

EPA Science Advisory Board (SAB) Staff Office. The Council is chartered to provide extramural 

scientific information and advice to the Administrator and other officials of the EPA. The Council is 

structured to provide balanced, expert assessment of scientific matters related to issues 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. Council reports are posted on the Council 

Web site at: http://www.epa.gov/advisorycouncilcaa. 

i 
U.S. Environmental Protection Agency 

Advisory Council on Clean Air Compliance Analysis 

Air Quality Modeling Subcommittee, Augmented 

with Members of the Council 

CHAIR 

Dr. Armistead (Ted) Russell, Professor, Department of Civil and Environmental Engineering, 

Georgia Institute of Technology, Atlanta, GA 

 

COUNCIL MEMBERS 

Dr. James K. Hammitt (COUNCIL Chair), Professor, Center for Risk Analysis, Harvard 

University, Boston, MA 

Mr. Richard L. Poirot, Environmental Analyst, Department of Environmental Conservation, 

Vermont Agency of Natural Resources, Waterbury, VT 

SUBCOMMITTEE MEMBERS 

Dr. David T. Allen (AQMS Past-Chair), Professor, Department of Chemical Engineering, 

University of Texas, Austin, TX 

Dr. David Chock, Independent Consultant, Bloomfield Hills, MI 

Dr. Paulette Middleton, President, Panorama Pathways, Boulder, CO 

Mr. Ralph Morris, Managing Principal, Air Sciences Group, Environ International Corporation, 

Novato, CA 

Dr. James Price, Senior Scientist, Air Quality Division, Texas Commission on Environmental 

Quality, Austin, TX 

Dr. Chris Walcek, Senior Research Scientist, Atmospheric Sciences Research Center, State 

University of New York, Albany, NY 

SCIENCE ADVISORY BOARD STAFF 

Ms. Stephanie Sanzone, Designated Federal Officer, 1200 Pennsylvania Avenue, NW, 

Washington, DC. Phone: 202-564-2067, Fax: 202-565-2098, (sanzone.stephanie@epa.gov) 

ii 
U.S. Environmental Protection Agency 

Advisory Council on Clean Air Compliance Analysis 

CHAIR 

Dr. James K. Hammitt, Professor, Center for Risk Analysis, Harvard University, Boston, MA 

MEMBERS 

Dr John Bailar, Scholar in Residence, The National Academies, Washington, DC 

Dr. Michelle Bell, Associate Professor, School of Forestry and Environmental Studies, Yale 

University, New Haven, CT 

Dr. Sylvia Brandt, Associate Professor, Department of Resource Economics, University of 

Massachusetts, Amherst, MA 

Dr. Linda Bui, Associate Professor, Department of Economics, Brandeis University, Waltham, 

MA 

Dr. Dallas Burtraw, Senior Fellow, Resources for the Future, Washington, DC 

Dr. Ivan J. Fernandez, Professor, Department of Plant, Soil and Environmental Sciences, 

University of Maine, Orono, ME 

Dr. Shelby Gerking, Professor, Department of Economics, University of Central Florida, 

Orlando, FL 

Dr. Wayne Gray, Professor, Department of Economics, Clark University, Worcester, MA 

Dr. D. Alan Hansen, Independent Consultant, Fremont, CA 

Dr. Nathaniel Keohane, Chief Economist, Environmental Defense Fund, New York, NY 

Dr. Jonathan Levy, Professor, Department of Environmental Health, Boston University School 

of Public Health, Boston, MA 

Mr. Richard L. Poirot, Environmental Analyst, Air Pollution Control Division, Department of 

Environmental Conservation, Vermont Agency of Natural Resources, Waterbury, VT 

Dr. Arden Pope, Professor, Department of Economics, Brigham Young University, Provo, UT 

Dr. Armistead (Ted) Russell, Professor, Department of Civil and Environmental Engineering, 

Georgia Institute of Technology, Atlanta, GA 

Mr. Michael Walsh, Independent Consultant, Arlington, VA 

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SCIENCE ADVISORY BOARD STAFF 

Ms. Stephanie Sanzone, Designated Federal Officer, 1200 Pennsylvania Avenue, NW, 

Washington, DC, Telephone: 202-343-9697, Fax: 202-233-0643, (sanzone.stephanie@epa.gov)