June 13, 1996
EPA-SAB-CASAC-LTR-96-008
Honorable Carol M. Browner
Administrator
U.S. Environmental Protection Agency
401 M. Street SW
Washington, DC 20460
Subject: Closure by the Clean Air Scientific Advisory Committee (CASAC) on the
Staff Paper for Particulate Matter
Dear Ms. Browner:
The Clean Air Scientific Advisory Committee (CASAC) of EPA's Science
Advisory Board (SAB) has held a series of public meetings during its peer review of the
Agency's draft documents which will form part of the basis for your decision regarding
the National Ambient Air Quality Standards (NAAQS) for Particulate Matter (PM). The
Committee has held public meetings on December 12-13, 1994 (planning and
introductory issues); August 3-4, 1995 (review of the initial draft Criteria Document);
December 14-15, 1995 (review of the revised draft Criteria Document and the first draft
of the Staff Paper); February 29, 1996 (review of the revised draft Criteria Document -
specified chapters only, and the Office of Air Quality Planning and Standards (OAQPS)
Risk Assessment Plan); and May 16-17, 1996 (review of the revised draft Staff Paper).
The primary Agency draft documents that we have reviewed are the: a) Air Quality
Criteria for Particulate Matter (the "Criteria Document" prepared by the National Center
for Environmental Assessment - Research Triangle Park, NC - ORD), b) Review of the
National Ambient Air Quality Standards for Particulate Matter: Policy Assessment of
Scientific and Technical Information (the "Staff Paper" prepared by the Office of Air
Quality Planning and Standards - Research Triangle Park, NC - OAR), and c) A
Particulate Matter Risk Analysis for Philadelphia and Los Angeles (draft), 1996,
Prepared by Abt Associates for US EPA.
As part of our review process, we have kept you informed of our findings through
three letter reports: a) Clean Air Scientific Advisory Committee (CASAC) Comments on
the April 1995 draft Air Quality Criteria for Particulate Matter (EPA-SAB-CASAC-LTR-
95-005; August 30, 1995); b) Clean Air Scientific Advisory Committee (CASAC)
Comments on the November, 1995 Drafts of the Air Quality Criteria for Particulate
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Matter and the Review of the National Ambient Air Quality Standards for F'articulate
Matter: Policy Assessment of Scientific and Technical Information (OAQPS Staff
Paper), (EPA-SAB-CASAC-LTR-96-003, January 5, 1996), and c) Closure by the Clean
Air Scientific Advisory Committee (CASAC) on the draft Air Quality Criteria for
Particulate Matter (EPA-SAB-CASAC-LTR-96-005, March 15, 1996).
The Clean Air Scientific Advisory Committee, supplemented by a number of
expert Consultants (hereinafter referred to as the "Panel"), reviewed a first draft of the
Staff Paper for Particulate Matter at the December 14 and 15, 1995 meeting in Chapel
Hill, NC. At that meeting and in subsequent written comments by individual members
which were provided to EPA Staff, the Panel made numerous recommendations for
improving the draft document. The Panel met again on May 16, 1996 in Chapel Hill,
NC and on May 17, 1996 in Research Triangle Park, NC to review a revised draft of the
Staff Paper and the recommendations contained within the Staff Paper for the level and
form of the proposed PM NAAQS. This letter is a summary of our findings and
conclusions from that meeting.
It was the consensus of the Panel that although our understanding of the health
effects of PM is far from complete, the Staff Paper, when revised, will provide an
adequate summary of our present understanding of the scientific basis for making
regulatory decisions concerning PM standards. Seventeen of the twenty-one Panel
members voted for closure. There were two no votes, one abstention, and one
absence. However, most of the members who voted for closure did so under the
assumption that the Agency would make significant changes to the next version of the
Staff Paper which is due by July 15, 1996 (a court ordered mandate). The desired
changes have been articulated to your staff at the meeting and subsequently in writing.
The Panel endorses the EPA Staffs recommendation not to establish a separate
secondary PM NAAQS for regulating regional haze and agrees that there is an
inadequate basis for establishing a secondary NAAQS to reduce soiling and material
damage effects.
The attached table (Table I) summarizes the Panel members' recommendations
concerning the form and levels of the primary standards. Although some Panel
members prefer to have a direct measurement of coarse mode PM (PM10_2 5) rather than
using PM10 as a surrogate for it, there is a consensus that retaining an annual PM10
NAAQS at the current level is reasonable at this time. A majority of the members
recommend keeping the present 24-hour PM10 NAAQS, at least as an option for the
Administrator to consider, although those commenting on the form of the standard
strongly recommended that the form be changed to one that is more robust than the
current standard. There was also a consensus that a new PM25 NAAQS be
established, with nineteen Panel members endorsing the concept of a 24-hour and/or
an annual PM25 NAAQS. The remaining two Panel members did not think any PM25
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NAAQS was justified. However, as indicated in Table I, there was no consensus on the
level, averaging time, or form of a PM25 NAAQS. At first examination of Table I, the
diversity of opinion is obvious and appears to defy further characterization. However,
the opinions expressed by those endorsing new PM25 NAAQS can be classified into
three broad categories. Four Panel members supported specific ranges or levels within
or toward the lower end of the staffs recommended ranges. Seven Panel members
supported specific ranges or levels near, at, or above the upper end of staffs
recommended ranges. Eight other Panel members declined to select a specific range
or level, but most had comments which appear as footnotes in Table I.
A number of Panel members based their support for a PM25 NAAQS on the
following reasoning: there is strong consistency and coherence of information
indicating that high concentrations of urban air pollution adversely affect human health,
there are already NAAQS that deal with all the major components of that pollution
except PM25, and there are strong reasons to believe that PM25 is at least as important
as PM10_25 in producing adverse health effects.
Part of this diversity of opinion can be attributed to the accelerated review
schedule. While your staff is to be highly commended for producing such quality
documents in such a short period of time, the deadlines did not allow adequate time to
analyze, integrate, interpret, and debate the available data on this very complex issue.
Nor does a court-ordered schedule recognize that achieving the goal of a scientifically
defensible NAAQS for PM may require iterative steps to be taken in which new data are
acquired to fill obvious and critical voids in our knowledge. The previous PM NAAQS
review took eight years to complete.
The diversity of opinion also reflects the many unanswered questions and
uncertainties associated with establishing causality of the association between PM25
and mortality. The Panel members who recommended the most stringent PM25
NAAQS, similar to the lower part of the ranges recommended by the Staff, did so
because they concluded that the consistency and coherence of the epidemiology
studies made a compelling case for causality of this association. However, the
remaining Panel members were influenced, to varying degrees by the many
unanswered questions and uncertainties regarding the issue of causality. The
concerns include: exposure misclassification, measurement error, the influence of
confounders, the shape of the dose-response function, the use of a national PM25/PM10
ratio to estimate local PM25 concentrations, the fraction of the daily mortality that is
advanced by a few days because of pollution, the lack of an understanding of
toxicological mechanisms, and the existence of possible alternative explanations.
In recommending that the staff carry out a risk assessment, it was the
expectation of CASAC that the risk assessments would narrow the diversity of opinion
by evaluating how all of the uncertainties propagate throughout the entire model.
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However, not all of the uncertainties could be included and the combined effect of all of
them could not be examined. The Panel recommended that additional analyses be
conducted to present combined uncertainties. However, currently the risk assessments
are of limited value in narrowing the diversity of opinion within the Panel.
The Panel is unanimous, however, in its desire to avoid being in a similar
situation when the next PM NAAQS review cycle is under way by a future CASAC
Panel. The Agency must immediately implement a targeted research program to
address these unanswered questions and uncertainties. It is also essential that we
obtain long-term PM2 5 measurements. CASAC is ready to assist the Agency in the
development of a comprehensive research plan that will address the questions which
need answers before the next PM review cycle is completed. We understand that your
staff is preparing a PM research plan for our review later this summer. We look forward
to providing our comments on this important matter.
CASAC recognizes that your statutory responsibility to set standards requires
public health policy judgments in addition to determinations of a strictly scientific
nature. While the Panel is willing to advise you further on the PM standard, we see no
need, in view of the already extensive comments provided, to review any proposed PM
standards prior to their publication in the Federal Register. In this instance, the public
comment period will provide sufficient opportunity for the Panel to provide any
additional comment or review that may be necessary.
Thank you for the opportunity to present the Panel's views on this important
public health issue. We look forward to your response to the advice contained in this
letter.
Sincerely,
Dr. George T. Wolff, Cha
Clean Air Scientific Advisory Committee
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TABLE I
Summary of CASAC Panel Members Recommendations
(all units ug/m3)
Current NAAQS
EPA Staff Recommendation
PM2.5
24-hr
N/A
18-65
PM2.5
Annual
N/A
12.5-20
PM10
24-hr
150
15013
PM10
Annual
50
40-50
Name
Ayres
Hopke
Jacobson
Koutrakis
Larntz
Legge
Lippmann
Mauderly
McClellan
Menzel
Middleton
Pierson
Price
Shy
Samet1
Seigneur
Speizer1
Stolwijk
Utell
White
Wolff
Discipline
M.D.
Atmos. Sci.
Plant Biologist
Atmos. Sci.
Statistician
Plant Biologist
Health Expert
Toxicologist
Toxicologist
Toxicologist
Atmos. Sci.
Atmos. Sci.
Atmos. Sci./
State Official
Epidemiologist
Epidemiologist
Atmos. Sci.
Epidemiologist
Epidemiologist
M.D.
Atmos. Sci.
Atmos. Sci.
yes2
20 - 503
yes2
yes2'5'6
no
>75
20 - 503
50
no8
no
yes2'3'12
yes2'9
yes3'10
20-30
yes2'11
yes3'5
20-50
757
>65
no
>753'7
yes2
20-30
yes2
yes2'5'6
25-307
no
15-20
20
no8
no
yes2'5
yes2'9
yes10
15-20
no
no
no
25-307
no
20
no
150
no
150
no
no
150
no
150
150
150
1503,13
yes4
no3'4
no
150
15013
no
150
150
150
1503
50
40 -504
50
yes4
yes2
40-50
40-50
50
50
50
50
yes4
yes4
50
yes2
50
40-50
50
50
50
50
1
not present at meeting; recommendations based on written comments
2 declined to select a value or range
3 recommends a more robust 24-hr, form
4
perfers a PM10_2 5 standard rather than a PM10 standard
5 concerned upper range is too low based on national PM25/PM10 ratio
6 leans towards high end of Staff recommended range
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7 desires equivalent stringency as present PM10 standards
8 if EPA decides a PM25 NAAQS is required, the 24-hr, and annual standards
should be 75 and 25 ug/m3, respectively with a robust form
9 yes, but decision not based on epidemiological studies
10 low end of EPA's proposed range is inappropriate; desires levels selected to
include areas for which there is broad public and technical agreement that
they have PM25 pollution problems
11 only if EPA has confidence that reducing PM25 will indeed reduce the components
of particles responsible for their adverse effects
12 concerned lower end of range is oo close to background
13 the annual standard may be sufficient; 24-hr level recommended if 24-hour
standard retained
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NOTICE
This report has been written as part of the activities of the Science Advisory Board, a
public advisory group providing extramural scientific information and advice to the
Administrator and other officials of the Environmental Protection Agency. The Board is
structured to provide balanced, expert assessment of scientific matters related to 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 Environmental Protection Agency, 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.
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U.S. Environmental Protection Agency
Science Advisory Board
Clean Air Scientific Advisory Committee
Particulate Matter Review Panel
Chairman
Dr. George T. Wolff
General Motors
Environmental & Energy Staff
Detroit, Ml
Members
Dr. Stephen M. Ayres
Office of International Programs
Virginia Commonwealth University
/Medical College of Virginia
Richmond, VA
Dr. Phil Hopke
Department of Chemistry
Clarkson University
Pottsdam, NY
Dr. Jay S. Jacobson
Boyce Thompson Institute
Cornell University
Ithaca, NY
Dr. Joe L. Mauderly
Inhalation Toxicology Research
Institute
Lovelace Biomedical & Environmental
Research Institute
Albuquerque, NM
Dr. James H. Price, Jr.
Texas Natural Resource Conservation
Commission
Austin, TX
Consultants
Dr. Petros Koutrakis
Harvard School of Public Health
Boston, MA
Dr. Morton Lippmann
Institute of Environmental Medicine
New York University
Tuxedo, NY
Dr. Kinley Larntz
Department of Applied Statistics
University of Minnesota
St. Paul, MN
Dr. Allan Legge
Biosphere Solutions
Calgary, Alberta, Canada
Dr. Roger 0. McClellan
Chemical Industry Institute of
Toxicology
Research Triangle Park, NC
Dr. Daniel Menzel
Department of Community
and Environmental Medicine
University of California, Irvine
Irvine, CA
Dr. Paulette Middleton
Science and Policy Associates
Boulder, CO
Dr. William R. Pierson
Energy & Environmental Engineering
Center
Desert Research Institute
Reno, NV
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Dr. Carl M. Shy
Department of Epidemiology
School of Public Health
University of North Carolina
Chapel Hill, NC
Dr. John Samet
School of Hygiene & Public Health
Johns Hopkins University
Baltimore, MD
Dr. Christian Siegneur
AER, Inc
San Ramon, CA
Dr. Frank Speizer
Harvard Medical School
Channing Lab
Boston, MA
Dr. Jan Stolwijk
Yale University
New Haven, CT
Dr. Mark Utell
Pulmonary Disease Unit
University of Rochester Medical Center
Rochester, NY
Dr. Warren White
Washington University
St. Louis, MO
Science Advisory Board Staff
Mr. A. Robert Flaak
Designated Federal Official
U.S. EPA
Science Advisory Board
Washington, DC
Ms. Dorothy Clark
Staff Secretary
U.S. EPA
Science Advisory Board
Washington, DC
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