ENVIRONMENTAL
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY V PROTECTION
WASHINGTON, D.C. 20460 f AGENCY
DALLAS, TEXAS
Januarys, 1996 LIBRARY
EPA-SAB-CASAC-LTR-96-003
OFFICE OF THE ADMWISTRATOR
SCIENCE ADVISORY BOARD
Honorable Carol M. Browner
Administrator
U.S. Environmental Protection Agency
401 M. Street SW
Washington, DC 20460
Re: Clean Air Scientific Advisory Committee (CASAC) Comments on the
November, 1995 Drafts of the Air Quality Criteria for Particulate Matter
and the Review of the National Ambient Air Quality Standards for
Particulate Matter: Policy Assessment of Scientific and Technical
Information (OAQPS Staff Paper)
Dear Ms. Browner:
A Panel of the Clean Air Scientific Advisory Committee (CASAC) of EPA's Science
Advisory Board (SAB) reviewed a draft of the document entitled Air Quality Criteria for
Particulate Matter (PM) at a meeting in Research Triangle Park, NC on August 3 and 4, 1995.
At that meeting and in subsequent written comments that were provided to EPA staff, the Panel
made numerous recommendations for improving the document. On December 14 and 15, 1995,
the Panel met in Chapel Hill, NC to review a revised draft of the Air Quality Criteria for
Particulate Matter and a first draft of the Review of the National Ambient Air Quality Standards
for Particulate Matter: Policy Assessment of Scientific and Technical Information (Office of Air
Quality Planning and Standards - OAQPS - Staff Paper).
The Panel was impressed with the breadth and scope of the Criteria Document, especially
given the extremely tight schedule imposed upon the Agency by the Court. The Panel believes
that it is an extensive review of the PM literature. Although the Panel members' comments
reflect their satisfaction with the improvements made in the scientific quality and scope of the
Criteria Document since our first review in August, the Panel Members provided additional
extensive comments to your staff at the December meeting and subsequently in writing. The
most serious concerns were directed towards Chapter 13, the integrative health assessment
chapter. Unfortunately, the chapter reviewed in December still only summarizes the information
from the earlier chapters and does not integrate it into a cohesive assessment. The net result of
these deficiencies in Chapter 13 is that Chapter 1, the Executive Summary, is also flawed.
Because of these and a number of other problems that the Panel had with the Criteria Document
during the second review (these will be described below), it was the consensus of the Panel that
the document does not provide an adequate review of the available scientific data and relevant
studies of PM Further, many members of the Panel felt strongly that scientific quality, as
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intended by Congress in creating CASAC and mandating its role as a review and advisory body,
not a court-imposed timetable, should be the determining factor for reaching closure on the
Criteria Document. Consequently, the Panel did not come to complete closure on the Criteria
Document, and recommends that the Agency brings a redrafted version of the Criteria Document
to CASAC for consideration as soon as is practical.
The Panel was also impressed with the first draft of the Staff Paper. Some felt it was the
best first draft of any Staff Paper that CASAC has reviewed. However, the Panel could not come
to closure on the Staff Paper for reasons that will be articulated below. Some members raised
issue with the process of the preparation of the Staff Paper. Because the Criteria Document had
not been revised to meet the scientific standards of CASAC, the Staff Paper could not draw upon
the consensus advice of CASAC as intended by Congress in the Clean Air Act. Although the
Agency made an admirable effort in producing the Staff Paper under a tight timetable, the
current draft does not provide an adequately articulated scientific basis for making regulatory
decisions concerning a PM National Ambient Air Quality Standard (NAAQS).
Many of the Panel's comments apply to both the Criteria Document and the Staff Paper.
The objectives of Chapter 13 of the Criteria Document should be to integrate the health effects
and exposure information from the earlier chapters and synthesize the material that wil^form the
scientific basis for the recommendations made in the Staff Paper. The objectives of the Staff
Paper should be to build on the information presented in the Criteria Document integrating the
scientific information on PM and drawing out the policy implications for setting a PM National
Ambient Air Quality Standard. The majority of the Panel members who were assigned to
address the health effects aspects of the two documents felt the Agency fell short of achieving
these objectives. Besides this insufficient integration. Panel members raised a number of serious
concerns which are discussed below.
First, many Panel members felt that, as presented, the case for a PM2 5 standard was not
compelling. The arguments made in the Staff Paper implicating PM25 as the best available
surrogate measure for the causative agent are based principally on epidemiological studies, and
while the epidemiological evidence is reasonably consistent and convergent across mortality and
morbidity endpoints, it is not unambiguous. The risk factors being reported are not large and
they have relatively large uncertainties. In studies where multiple pollutants have been
considered, some implicate a measure of PM as the most important, while others implicate a
different pollutant. Different models using the same data implicate different pollutants, and
some do not implicate any pollutants. These results are not unexpected given the degree of
correlation among the various pollutants and the necessarily observational nature of the data.
Nevertheless, it is not possible to single out PM2 5 as the best surrogate.
More fundamentally, the Agency does not adequately justify the selection of PM25 as the
best surrogate measure for the causative agent. Most of the epidemiological studies did not use
PM25 as a measure. Most used PM10 or total suspended particulates (TSP), which are only
roughly correlated with PM2 5, and therefore, do not allow one to conclude that PM2 5 is the
causative agent or indeed that any specific component of the PM10 is the causative agent. Some
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studies used sulfate, which is usually a significant chemical constituent of the PM25. A number
of studies used British Smoke, coefficient of haze (COH), or other filter reflectance
measurements which are measures of the amount of black elemental carbon in the air and not a
measure of PM25. Still others used ambient visibility, an indicator of the accumulation mode
within PM2 5. It is sometimes unclear from the Staff Paper which of the studies in fact actually
measured PM25 and which of the studies estimated PM25 from other measures of paniculate air
pollution.
It should also be pointed out that the Staff Paper downplays the diversity of results, and
instead emphasizes those results where PM, and especially PM2 5, provide the strongest signal.
Unfortunately, the one acute epidemiological study (Schwartz, Dockery and Neas) to which the
Agency gives the most credibility is not in the peer-reviewed literature. A revised Staff Paper
should adequately discuss the recent reanalyses presented by the Health Effects Institute (HE!)
and others which conclude that a single causative agent cannot be identified in the limited
number of studies that have been reanalyzed. Based on the above, some Panel members are not
confident that a reduction in ambient PM2 5 will produce a decline in daily mortality or
morbidity. On the other hand, some other Panel members, looking at the cumulative
epidemiological evidence, believe that reducing ambient PM2 5 will decrease acute and chronic
mortality and morbidity.
In contrast to the Criteria Document, the Staff Paper fails to acknowledge the lack of
direct biological or clinical evidence supporting a causal relationship for the epidemiological
findings that implicate PM. Furthermore, focusing on PM2 5 ignores the extensive clinical
evidence that asthmatics can respond to particles larger than 2.5yum in diameter. The Staff Paper
needs to make a case that retention of an annual PM10 NAAQS can provide sufficient protection
from these larger particles within the thoracic fraction of ambient PM.
As a result of this major, and perhaps, premature focus on PM25, the Staff Paper failed to
critically review the available data as a basis for either reaffirming or revising the PM10
standards. EPA should correct this deficiency in a revised Staff Paper and not just direct primary
attention to a PM25 standard. Furthermore, some members felt that the selection of a 2.5 /^m
cutpoint was arbitrary, and that the Agency should consider other cutpoints (i.e., 1.0 /^m) as well.
The issue of premature mortality displacement of individuals who are already seriously
ill (harvesting) needs to be more fully discussed. This is a critical issue. It is of paramount
importance to know whether some, most, or all of the deaths are advanced by only one or several
days due to harvesting. Unfortunately, the discussions in the Staff Paper are inconclusive and
highly speculative. These discussions need to be revised and expanded.
As with ozone, there appears to be no apparent threshold for biological responses to PM
exposures. In the ozone Staff Paper for which CAS AC recently sent you its closure letter on the
primary standard portion (EPA-SAB-CASAC-LTR-95-002, November 30, 1995), quantitative
risk assessments based on methodologies that had undergone extensive CASAC review showed
the relative public health benefits provided by the various alternative standards. The PM Criteria
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Document and Staff Paper contain no quantitative risk assessments which allow one to judge the
benefits of having an annual PM25 standard between 15 /vg/m3 and 30 ^g/m1 or a 24-hr standard
between 25 /^g/m3 and 85 /ug/m3. The Staff Paper should provide more detailed justification for
the quantitative ranges proposed for the PM2 5 standards, especially since there may be no
threshold for biological responses to PM exposures. There should also be tables showing the
expected reductions in mortality and morbidity that would occur if the present PM10 standards
were revised to include PM25 standards within the proposed ranges. It would be helpful if these
tables were broken down by geographic region or city since the effect of a PM2 5 NAAQS would
probably be different in different regions or cities. In addition, this information should be
compared to similar data that reflect mortality and morbidity statistics due to the relevant
diseases so that the magnitude of the PM public health issue can be put into perspective relative
to other public health issues. Furthermore, there was concern that the Staff Paper inadequately
justified and potentially inflated the susceptible population by including virtually all individuals
except young healthy adults into the sensitive subpopulations.
In closing, I would like to add two more general, but equally important comments. First,
past Criteria Documents and Staff Papers did not rely so heavily on nonpeer-reviewed reports.
Both the present PM Criteria Document and the present PM Staff Paper cite numerous
unpublished reports, many of which are recent EPA contractor reports. As a result, it is hard to
judge the scientific credibility of many key studies that the Agency uses as a basis for their
conclusions in the Staff Paper. The Panel recommends that if the Agency cannot fully support
their judgments without these references, they should be clearly identified in the text as
nonpeer-reviewed reports. Furthermore, the Panel recommends that the Agency make these
reports part of the Public Docket, so all reviewers have access to them. The Panel is concerned
that the excessive use of nonpeer-reviewed reports will set a precedent that will erode the
scientific credibility of the NAAQS review process. This illustrates the need for EPA to begin
work immediately on developing the information that is needed for the next PM review cycle so
this problem does not occur in the future.
Second, it should be emphasized that the Panel feels strongly that EPA should negotiate
with the plaintiffs for a meaningful extension of the court-imposed deadlines for review of the
Criteria Document and Staff Paper. Such an extension should allow the Agency time to respond
to the Panel's comments and to produce revised drafts of the documents, and should allow
sufficient time for CASAC to adequately review the documents. In the present review, the Panel
had less than a month to review a voluminous amount of material. Some of the material was not
adequately reviewed because of time constraints and because some of the Panel members never
received portions of the Criteria Document that they were assigned to review. Although both the
Agency and the Panel tried their best to complete this review on the mandated schedule, the
schedule was unrealistic. Again, it must be the scientific quality of the Criteria Document and
Staff Paper that drive the review process and not some arbitrary and unrealistic court-imposed
time-table. This is the only way to avoid seriously compromising the entire review process.
In summary, the Panel found both draft documents to be generally well done. A few
members were of the opinion that the documents were scientifically adequate, but most of the
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members expressed the view that the documents did not provide a scientifically adequate basis
for revising the NAAQS for PM. Consequently, CASAC cannot reach closure on either
document at this time.
CASAC would appreciate being kept informed of progress on extending the
court-imposed deadline for completion of this review. If EPA is successful, we look forward to
receiving and reviewing the revised documents. If a sufficient extension is not granted, CASAC
would appreciate being kept informed of progress on establishing revised or new PM standards.
We also wish to be informed of EPA support of research to fill the important gaps in knowledge
and data that limit our ability to set effective PM standards for the protection of public health and
welfare. The EPA Staff, the CASAC Panel, and the public commenters have pointed out many
of these gaps and noted major uncertainties concerning the health impacts of ambient PM during
this review process.
As more information accumulates between now and the promulgation date, CASAC may,
from time to time, provide you with further advice and comments. Please do not hesitate to
contact me if CASAC can be of further assistance in this matter.
Sincerely,
Dr. George T. Wolff, Chair
Clean Air Scientific Advisory Committee
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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. 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. Paulette Middleton
Science and Policy Associates
Boulder, CO
Dr. James H. Price, Jr.
Texas Natural Resource Conservation
Commission
Austin, TX
Consultants
Dr. Phil Hopke
Department of Chemistry
Clarkson University
Pottsdam, NY
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
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Dr. William R. Pierson
Energy & Environmental Engineering
Center
Desert Research Institute
Reno, NV
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
NSR Consulting & Engineering
Alameda, 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. Connie Valentine
Staff Secretary
U.S. EPA
Science Advisory Board
Washington, DC
G:\USER\SAB\ROSTERS\PM-RPT.ROS
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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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