March 12, 1997
EPA-SAB-CASAC-LTR-97-004
Honorable Carol M. Browner
Administrator
U.S. Environmental Protection Agency
401 M Street SW
Washington, DC 20460
Subject: Evaluation of Research Needs for the Particulate Matter National
Ambient Air Quality Standards (NAAQS)
Dear Ms. Browner:
The Clean Air Scientific Advisory Committee (CASAC) of EPA's Science
Advisory Board (SAB), supplemented by a number of expert consultants (together
referred to as the "Panel"), reviewed the two draft documents, Particulate Matter
Research Needs for Human Health Risk Assessment (EPA, 1996a) and Particulate
Matter Research Program Strategy (EPA, 1996b) at a public meeting in Chapel Hill, NC
on November 18 and 19, 1996. At that meeting and in subsequent written comments
that were provided to EPA staff (hereafter referred to as the "Staff"), the Panel made
numerous recommendations for improving the documents. This letter is a summary of
the Panel's key comments and conclusions. Staff is referred to the transcript of the
meeting and to individual members' comments for details and issues beyond this
summary.
The Panel commends the Staff for developing these important documents, and
notes that the review drafts represent significant steps toward setting the stage for the
research that is critical to resolving present uncertainties about the health impacts of
particulate matter (PM). In its past reviews of the Particulate Matter Criteria Document
and Staff Paper, the Panel repeatedly asserted its strong recommendation that critical
PM research be identified and a strategy for its accomplishment be developed. With
revision, these documents will set forth a framework from which more detailed plans
can be developed by EPA and other stakeholder organizations.
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1. Participate Matter Research Needs for Human Health Risk Assessment
The document is of sufficient length and complexity that it would benefit from
addition of an Executive Summary and a final section in which Staff presents its
summary and conclusions, as well as reorganization to give greater recognition to
phased needs and goals.
The comprehensiveness of this document is both a strength and weakness. In
its present form, it is an encyclopedic compilation of PM research topics, but it lacks
sufficient focus to present a clear view of the most important research needs. The
document's utility suffers from its failure to clearly place PM research needs in the
context of the present large uncertainties in assessing the health risks from inhaled PM,
and thus in setting the form and level of PM NAAQS. Beginning with a risk assessment
framework would resolve many of the specific criticisms raised in individual Panel
members' comments. A useful approach would be to begin with a framework
consisting of the key steps in health risk assessment and standard setting. The key
uncertainties presently limiting accomplishment of each step could then be listed in
summary form and then summary statements of the information needed to reduce the
key uncertainties could be listed. With this structure as a prologue, the most important
research and the research approaches likely to be most productive could be described.
This risk-based framework should look forward to the next review of the PM NAAQS;
however, a commitment to research over a longer period (e.g., 10-15 years) is also
needed. The likelihood of having a significant impact on the regulatory decision in
2001 is a useful criterion for prioritizing much of the proposed research. The document
would be much improved by summarizing the above information in tabular or figure
form.
Critical to the above process is an accurate portrayal of the nature and
magnitude of present uncertainties. Several Panel members expressed concern that
the present draft does not reflect present uncertainties accurately. The Panel noted
that the present draft conveys the notion that the direct causality of PM, and especially
PM25, in the health effects observed by epidemiology is established. While the Panel
agrees that present evidence warrants concern and most members support
implementation of a fine particle standard, the Panel urges that it be explicitly stated
that the causality of PM25 has not been clearly established. In this and previous
meetings, the Panel has noted a range of important uncertainties. For example, in its
March 15, 1996 letter of closure on the draft PM Criteria Document (SAB, 1996a),
CASAC noted uncertainties concerning the relationship between area monitoring data
and personal exposure, and concerning the suitability of PM25 as the best surrogate for
the causative agent(s). CASAC also noted that some reviews of the epidemiological
database indicated that the health effects could not be unambiguously associated with
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PM. In its June 13, 1996 letter addressing the PM Staff Paper (SAB, 1996b), CASAC
offered a range of views about the justification for, and most appropriate level of, a
PM25 standard, and listed numerous specific uncertainties that need to be resolved.
This review of research needs requires greater consideration of the magnitude
of funding required to fill the most critical information gaps. Much of the proposed
research is feasible, but cannot be conducted within the level of funding directed
toward PM research in the present or recent fiscal years. The continued failure to fund
PM research at a level commensurate with its importance is a critical gap in EPA's
research strategy. The document does not portray the cost of research required to
address even the most key uncertainties. Describing the approximate costs and time
lines would place PM research needs in a budget context and could facilitate
discussion of sharing of costs among agencies and other sponsors.
The review of research needs would also benefit from more consideration of the
technical practicality and time requirements of conducting the proposed research. As
noted in individual members' comments, some of the research suggested is not
presently feasible for technological reasons. The time required to fill critical information
gaps is not portrayed. The document would benefit from the placement of research in a
time context with the next review of the PM NAAQS as a focal point. Although work on
many issues must continue beyond that point, this benchmark would engender a
realistic expectation of the work that could be accomplished by then, and as noted
earlier, would help with prioritization.
There should be greater emphasis on resolving uncertainties about the
long-term effects of PM. Additional attention should be focused on long-term effects,
such as life shortening or progressive disease. Accompanying data are needed on
long-term PM levels, trends, and characteristics, as well as levels of other pollutants.
The Panel felt that there was little need for documenting additional examples of
associations between short-term increases in PM and health effects using the same
approaches as in the past. There is a need for new data sets providing improved
understandings of the individuals incurring short-term effects and the physical-chemical
nature of the PM to which they were exposed, and for alternate data analysis
techniques.
The Panel noted a lack of emphasis on retrospective research to determine the
effectiveness with which reductions in PM and other pollutants reduce adverse health
effects. Many of the data cited as demonstrating the health effects of current concern
were collected 10-15 years ago. The downward trend in ambient PM should provide
opportunities to demonstrate an associated health benefit, and it might also be possible
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to follow implementation of specific source controls in some locations with studies to
detect improvements in health indices thought to be associated with PM. The Panel
appreciates the difficulty, pointed out by Staff, of detecting reductions in risks
associated with reductions of PM in view of their probable small magnitude and
numerous confounding factors. The Panel, however, would also remind the Agency
that it is precisely these health risks in the presence of confounding influences and
other uncertainties that give rise to the proposed change in the PM standard.
Demonstration of an association between reductions of PM and adverse health
outcomes would support causality.
The need for cross-disciplinary and international interactions is not adequately
emphasized. The efforts of atmospheric scientists, laboratory researchers, clinical
researchers, and epidemiologists will be required to resolve several of the
uncertainties, and consideration should be given to providing a framework for
integrating these efforts. There should be mention of the need for research training
with a focus on cross-disciplinary perspectives and collaborations. Collaboration of
EPA and its supported researchers in international efforts, for example with the "Air
Pollution and Health: European Project", should also be emphasized.
In his October 28, 1996 letter (EPA, 1996c), Dr. Lester Grant charged the Panel
with providing feedback on three issues (identified as a), b), and c) below). In
aggregate, the above comments and the comments of individual Panel members,
submitted to Staff, address those issues. We provide the additional following
comments.
a) Are the key questions/issues identified as needing to be addressed on the
mark? Has too much or too little emphasis been placed on one or
another of the key questions? Do other key questions/issues need to be
added?
(1) Several Panel members noted that the section containing key
questions could be improved by stating the key questions in
summary form and eliminating, or summarizing more succinctly, the
"subquestions".
(2) Less emphasis should be given to short-term epidemiology and
greater emphasis should be given to long-term epidemiology and
associated exposure characterization.
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(3) In question 4.C and elsewhere, eliminate the "live" and "dead"
particle terminology.1
(4) Question 8 is framed more as an operational issue than a research
need. It is probably best stated as a subquestion under questions
7 or 9.
b) Are the research needs identified subsequently in the document
appropriate and adequately characterized? Are there others that need to
be added?
There was no consensus that major research needs were overlooked.
Some members noted the need for an improved understanding of PM
concentrations that might be considered "background", or representative
of broader rural and semirural areas than present monitoring sites allow.
The individual comments contain numerous additional suggestions for
improving the scope and description of the needs. Although few of the
comments of individuals were mutually exclusive, their diverse nature
makes it impractical to summarize them in this letter.
c) Can the Committee assist EPA in terms of helping to prioritize the stated
research needs? Within given categories (e.g., exposure, health, etc.)
and/or across categories?
An exhaustive prioritization of the needs listed in this document was not
undertaken by the Panel; priorities were addressed in greater detail in
review of the Research Strategy document. While Staff is encouraged to
consider comments of individual Panel members on priorities within
different research topics, the following topics were generally considered
to be of high priority:
(1) Effects of long-term exposures and relative contributions of
short-term spikes and cumulative exposures to long-term health
outcomes.
(2) Mechanisms by which PM could contribute to life shortening, daily
mortality, and morbidity
"Dead" particles are either laboratory particles or collected, dried and resuspended ambient PM. "Live" particles are
ambient air or generated in smog chambers that are in equilibrium with water vapor, gaseous pollutants and dissolved components.
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(3) Linkages between PM data from area monitors and personal
exposures
(4) PM classes and physical-chemical characteristics associated with
different health effects, and
(5) extent to which PM causes health effects independently of other
pollutants.
2. Participate Matter Research Program Strategy
The Panel was charged by Staff in Dr. Grant's October 28, 1996 letter (EPA,
1996c) to provide feedback in the following two areas:
a) Review and comment on the research questions and issues EPA has
selected to focus on and the approaches EPA is planning to use to
address those questions/issues.
b) Comments and recommendations regarding relative priorities for the
various stated research areas/directions.
The following comments address these and other issues in areas for which
opinion could be generalized. Staff is encouraged to review the wide range of
additional comments contained in the written comments of individual Panel members,
which have been submitted to Staff.
This document is presented as a statement of EPA strategy for PM research, but
it falls short of defining and defending a strategic action plan. Like the Research
Needs document, this draft does not provide an adequate risk assessment framework
for identifying and prioritizing research and for allocating resources to the effort. The
strategy should flow from the Research Needs document by beginning with an
expression of key research needs arising from present uncertainties in setting the PM
NAAQS, and should be targeted toward improving the Agency's position at the next
review. This structure would help resolve the inadequate explanation in the present
draft of the basis for ranking. It is not clear which group, or by what process, the
present ranking and strategy were developed. The present draft does not place its
strategy in the context of research under way or proposed in other offices within the
Agency, in other Agencies and organizations, or in other countries. It is not clear, for
example, if this is an Agency-wide strategy or just a strategy for ORD.
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The critical issues of the allocation of resources to PM research and the
progress likely to result from those expenditures are missing from the discussion of
strategy. Oral presentations by Staff indicated that a total of $20 million annually was
projected for EPA PM research, and that represents approximately 0.3% of EPA's
budget. Moreover, it appears that only approximately 5% of EPA's research staff is
focused on PM issues. The Panel was unanimous in expressing its strong concern that
this level of funding and staffing falls far short of the resources needed to make
progress commensurate with the health and economic implications of estimated PM
effects and costs of controls. At this rate, support over even the five-year period
between PM NAAQS reviews would fall below annual expenditures by EPA and other
Agencies on issues having lesser estimated health and economic impacts. As a
related issue, EPA needs to highlight linkages to other programs within the Agency and
to efforts in other agencies that, in aggregate, constitute the nation's effort to
understand PM and its effects.
This document shares with the Research Needs document the characteristic of
overstating the certainty of the causality of PM in the health effects observed by
epidemiology, and especially the level of certainty concerning the causality of PM25 in
the adverse effects. Indeed, because the magnitude of this uncertainty underlies and
supports the priority of many of the strategic research goals, the uncertainty should be
emphasized rather than minimized.
Because the human health research priorities should flow from the information
needs described in the Research Needs document, health effects issues that are not
listed in that document should not be raised anew in this one. Examples of new issues,
such as the mention of altitude as a variable of concern, are contained in individual
Panel members' comments.
The key questions beginning on page 14 should be portrayed more clearly.
They should be organized around the framework of risk assessment, should be stated
more succinctly, and should be followed by a succinct statement of the basis for their
importance. If they are to be retained, the subheadings under each key question
should be prioritized.
Several Panel members commented that the structure of the ranking criteria
beginning on page 19 was not sufficiently focused. An example of a more focused
approach might be: a) likely impact on reducing uncertainties key to consideration of
the PM NAAQS; b) probability of success within technology and resources available;
and c) likelihood of creating knowledge also useful in other areas.
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The core issue of the document is the prioritization of research topics. As might
be expected from a Panel consisting largely of senior researchers from different
disciplines, a range of diverse and sometimes conflicting opinions was offered
regarding research priorities. This summary does not attempt to portray fully this range
of opinion; Staff is encouraged to examine the written comments of individual Panel
members.
There was consensus that epidemiological research on links between long-term
exposure to PM and life shortening and other long-term health effects was among the
highest priorities. Research on short-term effects should focus on refining our
understanding of exposure-dose-effects relationships. Priority should be given to
epidemiological studies of either type which provide the ability to examine linkages
between health effects and personal exposures to physical-chemical subclasses of PM.
When known, the nature and dose-response relationship of the effects of individual
compounds in pure form might provide a point of reference useful for judging the
plausibility of effects estimated for those compounds encountered as constituents of
PM.
There was also consensus that laboratory and clinical research exploring
potential mechanisms of response to PM was among the highest priorities. Greatest
value was placed on research exploring associations between physical-chemical PM
characteristics and response pathways and potency. High value was also placed on
studies exploring the existence and nature of responses at environmentally-relevant
doses of PM.
Research providing a better understanding of personal exposure, and especially
of individuals thought to be most susceptible, was given high priority.
Beyond the above priorities, opinion was mixed and defied straightforward
summary. There was mixed enthusiasm for atmospheric modeling and characterization
of source emissions. Studies of the dosimetry of inhaled particles in normal subjects
was not given strong support, although it was agreed that present dosimetry models
could benefit from a better understanding of particle deposition and clearance in
abnormal lungs. There were mixed views regarding the priority of developing tools for
market-based control approaches. Some members favored conducting research to
improve market-based approaches. Others warned that not all PM25 species are
equipotent and that such approaches must be informed by an understanding of the
relative contributions of different physical-chemical classes of PM within size ranges.
Staff is advised to weigh these issues in view of individual members' comments.
8
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3. Summary
The Panel commends Staff for initiating the strategic planning which resulted in
these draft documents, and encourages Staff to undertake the revisions necessary for
the documents to serve as a solid foundation for EPA's PM research program. These
documents can play a critical role in EPA's ability to fulfill its mission to protect the
public health from airborne pollutants. The Panel recognizes that some of the
recommended changes will require significant effort and additional resources, but
believes that the effort will be well-placed in improving EPA's PM research program and
the benefits attributable to the program's findings. In view of the importance the Panel
attaches to the PM research program and thus the proposed revisions, the Panel looks
forward to the opportunity to review the revised documents. The Panel appreciates the
opportunity to provide comments on these documents, and looks forward to completion
of this important effort. We look forward to your response to our advice.
Sincerely,
/signed/
Dr. Joseph L. Mauderly, Chair
Clean Air Scientific Advisory Committee
U.
I^ „ -- „„,
Dr. George T. Wolff, lmmediate^3fst Chair
Clean Air Scientific Advisory Committee
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References Cited
EPA. 1996a. Particulate Matter Research Needs for Human Health Risk Assessment.
External Review Draft. NCEA-R-0973. U.S. Environmental Protection Agency,
National Center for Environmental Assessment (NCEA), Office of Research and
Development, Research Triangle Park, NC. October 25, 1996.
EPA. 1996b. Particulate Matter Research Program Strategy, External Review Draft.
NHEERL MS-97-019. U.S. Environmental Protection Agency, Office of
Research and Development, Research Triangle Park, NC. October 1996.
EPA. 1996c. Letter transmitting review materials and the charge to CASAC from Dr.
Lester Grant, Director, NCEA, to Dr. George Wolff, Chair, CASAC. October 28,
1996.
SAB. 1996a. Closure by the Clean Air Scientific Advisory Committee (CASAC) on the
draft Air Quality Criteria for Particulate Matter. Clean Air Scientific Advisory
Committee, Science Advisory Board, U.S. Environmental Protection Agency,
Washington, DC. EPA-SAB-CASAC-LTR-96-005. March 15, 1996.
SAB. 1996b. Closure by the Clean Air Scientific Advisory Committee (CASAC) on the
Staff Paper for Particulate Matter. Clean Air Scientific Advisory Committee,
Science Advisory Board, U.S. Environmental Protection Agency, Washington,
DC. EPA-SAB-CASAC-LTR-96-008. June 13, 1996
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NOTICE
This report has been written as a 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 faced by 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 or other agencies in the
Federal government. Mention of trade names or commercial products does not
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
(Membership information current as of March 1997)
Chairman
Dr. Joe L. Mauderly
Inhalation Toxicology Research
Institute
Lovelace Biomedical & Environmental
Research Institute
Albuquerque, NM
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. James H. Price, Jr.
Texas Natural Resource Conservation
Commission
Austin, TX
Dr. Warren White
Washington University
St. Louis, MO
Dr. George T. Wolff
(Immediate Past CASAC Chair)
General Motors
Environmental & Energy Staff
Detroit, Ml
Consultants
Dr. Petros Koutrakis
Harvard School of Public Health
Boston, MA
Dr. Morton Lippmann
(Former CASAC Chair)
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
(Former CASAC Chair)
Chemical Industry Institute of
Toxicology
Research Triangle Park, NC
Dr. Daniel Menzel
Department of Community
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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
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
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
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
Dr. Frank Speizer
Harvard Medical School
IV
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