July 31,2000
EPA-SAB-CASAC-LTR-00-006
Honorable Carol M. Browner
Administrator
U.S. Environmental Protection Agency
1200 Pennsylvania Avenue, NW
Washington, DC 20460
Subj ect: Review of the US EPA Response to Section 6102(e) of the
Transportation Equity Act for the 21st Century
Dear Ms. Browner:
The Clean Air Scientific Advisory Committee (CASAC), as mandated under section 109 of the
Clean Air Act Amendments of 1977 (42 U.S.C. 7409), provides advice to you on the scientific and
technical issues associated with the national ambient air quality standards (NAAQS). To provide you
and your staff with the most relevant and up to date advice on the scientific basis for the paniculate
matter NAAQS, we have established the CASAC Technical Subcommittee on Fine Particle
Monitoring (the "Subcommittee"). This Subcommittee has been active over the past several years
working closely with staff of the Office of Air and Radiation and the Office of Research and
Development.
Most recently, the Subcommittee was asked to conduct a very rapid review of the Agency's
report to Congress on its response to Section 6102(e) of the Transportation Equity Act for the 21st
Century. That review was conducted via a public teleconference on June 21, 2000. Following that
Subcommittee meeting, and after careful review, the full CASAC met on July 28, 2000 via public
teleconference, during which it reviewed and approved the attached Subcommittee report.
The CASAC is pleased to establish an interactive advisory relationship with the Agency
through this Subcommittee, and looks forward to assisting the Agency in optimizing the design and
implementation of its fine particle monitoring system and the utility of the information that system will
provide.
Sincerely,
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Dr. Joe L. Mauderly, Chair
Clean Air Scientific Advisory Committee
U.S. Environmental Protection Agency
Science Advisory Board
Clean Air Scientific Advisory Committee (CASAC)
Chair
Dr. Joe Mauderly, Vice President and Senior Scientist, Lovelace Respiratory Research Institute,
Albuquerque, NM
Members
Mr. John Elston, Administrator, Office of Air Quality Management, State of New Jersey, Department
of Environmental Protection and Energy, Trenton, NJ
Dr. Philip K. Hopke, R.A. Plane Professor, Clarkson University, Department of Chemical
Engineering, Potsdam, NY
Dr. Eva J. Pell, Steimer Professor of Agricultural Sciences, The Pennsylvania State University,
University Park, PA
Dr. Arthur C. Upton, M.D., Director, Independent Peer Review, CRESP, Environmental and
Occupational Health Sciences Institute, New Brunswick, NJ
Dr. Sverre Vedal, M.D., Professor of Medicine, Respiratory Division, Vancouver General Hospital,
Vancouver, BC, Canada
Dr. Warren White, Senior Research Associate, Washington University, Chemistry Department, St.
Louis, MO
Science Advisory Board Staff
Mr. Robert Flaak, Designated Federal Official (DFO), US Environmental Protection Agency,
Science Advisory Board (1400A), 1200 Pennsylvania Avenue, NW, Washington, DC 20460
Ms. Diana Pozun, Management Assistant, US Environmental Protection Agency, Science Advisory
Board (1400A), 1200 Pennsylvania Avenue, NW, Washington, DC 20460
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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.
Distribution and Availability: This Science Advisory Board report is provided to the EPA
Administrator, senior Agency management, appropriate program staff, interested members of the
public, and is posted on the SAB website (www.epa.gov/sab). Information on its availability is also
provided in the SAB's monthly newsletter (Happenings at the Science Advisory Board). Additional
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copies and further information are available from the SAB Staff.
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Report of the
Clean Air Scientific Advisory Committee (CASAC)
Technical Subcommittee on Fine Particle Monitoring
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June 28, 2000
Dr. Joe L. Mauderly, Chair
Clean Air Scientific Advisory Committee (CASAC)
USEPA Science Advisory Board
U.S. Environmental Protection Agency
1200 Pennsylvania Avenue, NW
Washington, DC 20460
Subj ect: Review of the US EPA Response to Section 6102(e) of the
Transportation Equity Act for the 21st Century
Dear Dr. Mauderly:
The Technical Subcommittee on Fine Particle Monitoring of the Clean Air Scientific Advisory
Committee (CASAC) of EPA's Science Advisory Board, met via public teleconference on
Wednesday, June 21, 2000 to review the US EPA response to Section 6102(e) of the Transportation
Equity Act for the 21st Century. This response to Congress was prepared by EPA's Office of
Research and Development (ORD).
Background
Section 6102(e) of the Transportation Equity Act for the 21st Century requires the U.S.
Environmental Protection Agency to verify the performance of the sampler that was designated by 40
CFR Part 50, Appendix L (July 1997) to be the Federal Reference Method (FRM) sampler for PM2.5.
In the Act, Congress specified that:
The Administrator shall conduct a field study of the ability of the PM2.5 Federal
Reference Method to differentiate those particles that are larger than 2.5 micrograms in
diameter. This study shall be completed and provided to the Committee on Commerce of
the House of Representatives and the Committee on Environment and Public Works of
the United States Senate no later than 2 years from the date of enactment of this Act.
In response to this requirement, ORD prepared the report Response to Section 6101(e) of the
Transportation Equity Act for the 21st Century (EPA Report Number 600/R-00/033 dated May
10, 2000), which presents results from several field studies conducted by both EPA and non-EPA
researchers. The report encompasses work done both before and after promulgation of the PM2.5
standard.
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Review Process and Charge to the Subcommittee
Prior to submitting the report to the Subcommittee for a full independent peer review, ORD had
the draft report reviewed by two external expert reviewers. Changes responsive to the comments of
these two reviewers were incorporated into the draft report prior to the Subcommittee review. For the
peer review, the Agency has asked that the Subcommittee respond to the following three questions:
a) Has the proper methodology been used to address the requirement in the
Transportation Equity Act?
b) Was the methodology applied correctly? and
c) Is the Report's interpretation correct?
The Subcommittee also decided to address the following question:
d) Has the submitted Report responded to the Congressional mandate/request as stated in
the Act?
The Agency sent the Subcommittee copies of the draft report along with additional background
materials several weeks prior to the public teleconference. The teleconference was announced in the
Federal Register and hosted from a conference room at EPA Headquarters. Although opportunity was
afforded for oral public commentary, there were no oral or written comments from the public prior to
or during the teleconference.
Subcommittee Responses to the Charge
a) Has the proper methodology been used to address the requirement in the
Transportation Equity Act?
The Subcommittee commends the authors for writing a generally thoughtful and useful
report. It is a difficult problem to make direct measurements of the size penetration
performance of a sampler in the field where it is hard to use generated monodisperse
particles as is possible in the laboratory. They have made use of a number of field
studies to examine the performance of the FRM in comparison with a number of other
sampling devices. Of particular note is the hybrid approach in which the Well Impactor
Ninety-Six (WINS) impactor was operated in the field to produce typical particle
loadings. It was then returned to the laboratory where particle penetration studies for
specific sized particles could be made. This is a useful and effective approach to
determine the effects of field operation on the system performance.
Neither the program of testing the FRM nor the Report directly outlines a set of
sampling questions to be answered and a related strategy. For example, there did not
seem to be a strategy to examine the range of meteorological conditions and particle
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compositions that might affect the FRM performance. Thus, there has been a
reasonable program of field sampling and analysis, but it has not yet been fully placed in
a context of a strategy to fully test the capabilities of the sampling system.
b) Was the methodology applied correctly?
These studies suggest that the WINS is performing as might be expected from the
earlier laboratory studies that examined its particle penetration properties. Thus, the
report provides evidence from laboratory and field studies regarding the effectiveness of
the FRM sampler at making a relatively sharp separation of particles smaller than 2.5
|im aerodynamic diameter from particles larger than 2.5 jim.
The Subcommittee therefore concludes that, in general, the work presented in the
Report did use a proper methodology and applied the methodology correctly. One
significant question is whether the methodology has been applied across a wide enough
range of conditions to fully explore the limits of acceptable system performance. There
were studies in Philadelphia, Rubidoux, Phoenix, Research Triangle Park, and Atlanta.
However, there were no specific studies under severe cold weather conditions. Most
of the studies (Four Cities Study) were done during the winter and thus these systems
were also not tested under extreme high temperatures. There were high humidity
conditions in Atlanta, but high temperature and low humidity conditions in high dust
areas such as Phoenix were not tested.
We would suggest that in the future, it would be useful to extend these studies to a more
complete range of conditions. It would also be helpful to make more direct
measurements of the penetration characteristics of the system. With care, we believe
that an Aerodynamic Particle Sizer (APS) could be used to make the necessary direct
measurements to confirm the results presented in the Report. It may also be possible to
generate a distinctive aerosol with known size distributions so that the penetration
properties of the system could be directly measured. For example, an aerosol
consisting of known relative concentrations of several sizes of polystyrene latex (PSL)
particles covering the range of 1 to 5 jam could be produced in which each size has a
distinctive fluorescent label. The material collected on the filter could then be easily
analyzed for its particle size distribution and the inlet penetration characteristics could
thus be ascertained.
There is also a question of the long-term performance of these systems. It is not
possible within the two year period to test the possibility of changes in system
performance over extended use. Thus, there needs to be a strategy and a commitment
for ongoing testing and evaluation of the FRM performance as additional experience in
its operation is obtained. In addition, a summary of the initial year of operational
experience by the state and local air quality agencies who are using the FRM would be
useful in evaluating the system's performance.
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c) Is the Report's interpretation correct?
In general, the Subcommittee concluded that the results of the reported studies were
appropriately interpreted within the range of conditions under which testing was
performed. One aspect of the discussion was the comparison of results with earlier
work by Tsai and Cheng [1995]. Because these studies did not correspond with the
conditions in the FRM, the Tsai and Cheng results were "adapted" in order to make the
presentation provided in the Report. The Subcommittee feels that it would be better to
eliminate the quantitative aspects of this comparison because of the required changes in
the published results. Qualitative comparisons with this work are appropriate to be
included.
In the Report, there is confusion between the ability of the FRM to accurately separate
particles based on aerodynamic diameter and the ability to accurately measure the mass
ofPM25. These are quite different questions. On page 24, the Report states: "Most
importantly to this presentation, this study demonstrated again that the WINS is capable
of preventing coarse particle intrusion that can lead to an overestimate of PM2.5 mass
concentration." We agree with this conclusion. However, on page 19, it says: "The
three studies highlighted in this chapter demonstrate clearly that the FRM effectively
measures PM2.5 mass concentration as well as - or in some cases better than the other
methods." We do not agree that this conclusion is warranted given that there is no
absolute standard for the airborne paniculate mass that can serve to test this assertion.
Given the existence of a number of problems with semivolatile particulate components
and the retention/elimination of particle bound water, these studies cannot address the
question of accurate mass concentration measurements and it is not appropriate to
make such a conclusion.
We would suggest that the discussion of the performance of the WINS relative to other
technologies, particularly the sharp-cut impactor be more balanced. The Report
appears to be more focused on justifying the choice of the WINS technology rather
than presenting its characteristics and performance. Given some of the operational
problems of the WINS involving the oil (crystallization, staff time commitment, etc.), it is
useful to examine if other devices can provide similar aerodynamic performance without
these difficulties. The a priori exclusion of other technologies does not appear
warranted at this time.
d) Has the submitted Report responded to the Congressional mandate/request as
stated in the Act?
The Subcommittee feels the Congressional inquiry focused on whether the FRM was
accurately measuring the indicator chosen for the PM2 5 NAAQS. This measurement
includes the ability of the FRM to accurately separate particles larger than 2.5 jim from
those which are smaller. However, the inquiry also includes the question as to whether
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the measurements are compromised by problems under specific operating conditions.
For example, it has been found that under certain circumstances, the oil in the WINS
can crystallize. There is then a possibility of particle bounce from the solid oil surface
leading to larger particles reaching the PM2.5. The crystallized oil clearly does not
represent the surface that was tested for its capability to separate particles at 2.5 jum.
Thus, it is not known how the penetration characteristics of the FRM change upon the
crystallization of the oil in the WINS impactor and large particles may bounce from the
surface and reach the PM2 5 filter. There have been reports of other problems with the
FRM samplers including observation of additional mass on the filters from passive
loading (particles blowing into the system while not in operation) in certain
manufacturer's designs and condensation of liquid water in the inlet leading to water in
the WINS impactor. The manufacturers have made some changes in response to these
reports and it would be useful to have a full compilation of problems reported, what has
been done to correct these problems, and what are the plans to address the remaining
issues.
Summary
In summary, the Subcommittee concludes that, in general, the Report meets the requirements
set by the Act. It could be further strengthened by additions and changes suggested in this review.
Because the particular section of the statute that required this report is not well known to the general air
pollution community, it is suggested that a different, more descriptive title be given to the report and the
reference to the statute be given in a subtitle.
In addition, the Report should not reprejfejt-spefmpfation of^stingyndreyabaj|oj^of monitoring
methods for airborne paniculate matter PAlwifigJfep5bdy oTthe performance of the FRM is needed
to assess the quality of the data coming from the rtfass monitoring network.
Sincerely,
Dr. Philip K. Hopke, Chair
Technical Subcommittee on Fine Particle Monitoring
Clean Air Scientific Advisory Committee
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U.S. Environmental Protection Agency
Science Advisory Board
Clean Air Scientific Advisory Committee
CASAC Technical Subcommittee for Fine Particle Monitoring
Chair
Dr. Phil Hopke, Clarkson University, Potsdam, NY (Member of CASAC)
Members of CASAC
Dr. John Elston, State of New Jersey, Dept. of Environmental Protection & Energy, Trenton, NJ (Did
not attend meeting)
Dr. Warren White, Washington University, St. Louis, MO
Members of Other SAB Committees
Dr. JoAnn Lighty, University of Utah, College of Engineering, Salt Lake City, UT (Member and
Liaison from SAB Environmental Engineering Committee) (Did not attend meeting)
Dr. Morton Lippmann, Nelson Institute of Environmental Medicine, New York University, Tuxedo,
NY (Interim Chair of the Science Advisory Board)
Consultants to CASAC
Dr. Petros Koutrakis, Harvard University, Boston, MA
Dr. Debra Laskin, Environmental & Occupational Health Sciences Institute, Rutgers University,
Piscataway, NJ (Did not attend meeting)
Dr. Peter H. McMurry, University of Minnesota, Department of Mechanical Engineering,
Minneapolis, MN
Dr. Kimberly A. Prather, Department of Chemistry, University of California-Riverside, Riverside,
CA (Did not attend meeting)
Dr. George T. Wolff, General Motors, Corporate Affairs, Detroit, MI (Did not attend meeting)
Mr. Mel Zeldin, Monitoring and Analysis Division, South Coast Air Quality Management District
(SCAQMD), Diamond Bar, CA
Science Advisory Board Staff
Mr. A. Robert Flaak, Designated Federal Officer, US EPA, Science Advisory Board (1400A),
1200 Pennsylvania Ave, NW, Washington, DC 20460
Ms. Diana Pozun, Management Assistant, US EPA, Science Advisory Board (1400A), 1200
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Pennsylvania Ave, NW, Washington, DC 20460
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Appendix A - Individual Comments
Peter McMurry
Abstract: I recommend that the text be modified to read "2.5 micrometers in aerodynamic diameter"
rather than "2.5 micrometers in diameter." The report eventually makes it very clear that separation is
on the basis of aerodynamic diameter, but this should be made clear up front as well.
p. 2, line 2: I don't know what is meant by "active" formation processes; I would delete "active"
p. 2, second paragraph: appears to be contradictory. I think it would be better if the paragraph were
to begin by mentioning the various major sources of coarse particles (soil dust, sea salt, pollens, plant
material, etc.) The paragraph could then continue with a discussion of formation mechanisms if it is felt
this is necessary (I don't). I don't think one would argue that sea salt and pollen are produced by a
mechanical process such as grinding, crushing and abrasion.
p. 2, third paragraph 3: I recommend that this be modified to read: "Typical ambient aerosol mass
distributions exhibit a minimum..."
p. 8, paragraph beginning "The number concentration..." Although the context makes clear what is
meant, I would not use the word "primary" to discuss the aerosols used to measure the impactor's size
cut.
p. 8, ammonium fluorescein: are these solid particles known to be spherical? If not, what is the
calibration error caused by the nonsphericity?
p. 12, reference to Tsai and Cheng (1995) article. The authors found it necessary to shift the data in
this paper to a larger size to make their point. I feel this weakens the report. I'd be inclined to eliminate
discussion of the Tsai and Cheng paper.
p. 13: "Use of the WINS in the field will not result in overestimation of mass concentrations, nor
overcollection of large particles." The report focuses on size cuts, not on measurement of mass
concentrations. I believe this sentence should be rewritten to indicate that the WINS will not lead to a
significant overestimate of PM2.5 mass concentrations due to sampling of coarse particles.
p. 14, first complete paragraph: Did Kenny's measurements involve sampling for a total of 96 to 132
hours over a 5 week period?
p. 14, last paragraph: Please mention how PM10 was measured.
p. 19, first paragraph "The three studies highlighted in this chapter demonstrate clearly that the FRM
effectively measures PM2.5 mass concentration as well as - or in some cases better than - the other
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methods." Again, the report should focus on the WINS size cut and not on the accuracy of mass
concentration measurements. See p. 24: "Most importantly to this presentation, this study
demonstrated again that the WINS is capable of preventing coarse particle intrusion that can lead to an
overestimate of PM2.5 mass concentration." YES.
p. 23. tables: Why is the increase in apparent PM2.5 crustal mass so much smaller than the increase in
PM2.5 mass concentration? Is there a problem with estimation of crustal mass from elements? Or, is it
something else (pollens, plant matter, etc.)?
p. 27, first bullet: "...may be described as "sharp."" I think it should be made clear that this is relative to
other inertial separators that could be used as an inlet.
George Wolff
1. Generally good job in answering/addressing the questions
2. They need to clarify how they calculated the soil component.
3. It would be better if they showed a comparison with a few other PM2.5 species, in particular,
elemental carbon, organic carbon, and nitrate. There are artifact issues involving these species, and it
would be good to see a comparison between the various methods to show better confidence (if the
data were collected).
Melvin Zeldin
Comments on the four specific charges questions are:
l)Yes
2) Yes
3) Yes
4) Not quite. While the report directly addresses the charge to conduct a field study, I believe
Congress intended to assure that such monitors were accurately measuring PM fine. Under special
studies, tests worked out to show the validity of the FRM. However, field experiences by state and
local agencies using the FRM under more rigorous situations than occurred in the field tests, showed
some problems with the FRMs, specifically, passive sampling, cold weather, oil crystallization, and
other conditions. I think it would be best if the report contained a chapter on actual field experiences,
the problems encountered, and how the problems have been overcome. (Some have not been
corrected yet.)
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Warren White
1. Why should the title be absolutely meaningless to 99.9999% of the nation's college graduates? This
is like a 6th-grader handing in a paper titled Two paragraphs my teacher made me write'! Why not
admit this is a report on The effectiveness of the FRM PM2.5 sample inlet for rejection of coarse
particles'? Reference to section 6102(e) could be a subtitle for the Congresso-philes. If the report
merits an agency number so that it can be retrieved from storage some day in the future, it also merits a
title that can still be deciphered then.
2. It would be very helpful to add an index of inlets and samplers (and their manufacturers), indicating
the combinations that were tested and the pages that discuss them. Anderson-RAAS, URG-MASS,
Met One-SASS, AN 3.68, SCC 2.141, and MST - these long alphanumeric strings all look like they
should contain a lot of information, but they sure aren't obvious mnemonics. SCC is the only one that
gets translated as an acronym/abbreviation.
3. The first of the bulleted conclusions (page 27) should be given substance, '...that the penetration
curve may be described as "sharp"' is not a falsefiable statement. Surely the cut provided by the old
dichot the WINS displaces was once described as "sharp"?
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