July 25, 2000
EPA-SAB-CASAC-ADV-00-006
Honorable Carol M. Browner
Administrator
U.S. Environmental Protection Agency
1200 Pennsylvania Avenue, NW
Washington, DC 20460
Subject: Clean Air Scientific Advisory Committee (CASAC) Advisory on the PM2.5
Monitoring Network
Dear Ms. Browner:
The Clean Air Scientific Advisory Committee (CASAC) of EPA's Science Advisory Board
reconstituted its Technical Subcommittee on Fine Particle Monitoring (the "Subcommittee"), at the
Agency's request, to provide advice and commentary on the Agency's fine particulate matter (PM2 5)
monitoring program. The Subcommittee, chaired by Dr. Phil Hopke of CASAC, met with Agency staff
on April 18-19, 2000 for another in a continuing series of discussions as the monitoring program is
designed and implemented. The attached Subcommittee report has been reviewed and approved by
the full CASAC.
This Subcommittee report conveys CASAC's view that the most appropriate role for the
Subcommittee is to respond to questions posed by the Agency and provide additional advice and
commentary in a continuing, participatory, and pro-active manner. The working relationship between
CASAC and the NAS/NRC Committee on Research Priorities for Airborne Particulate Matter was
described in the previous report of the Subcommittee that the CASAC endorsed to you in January
1999 (CASAC Advisory on the PM2S Monitoring Program, EPA-SAB-CAS AC-ADV-99-002,
January 28, 1999).
The attached report summarizes the Subcommittee's technical advice regarding issues posed by
the Agency, and provides additional comments on related issues. Two separate Notifications of a
Consultation concerning the Subcommittee's discussions with the Agency on thermal carbon analysis
and the sampler intercomparison study have been produced and forwarded to you under separate
cover to acknowledge CAS AC's ongoing participation in these issues (EPA-SAB-CASAC-CON-00-
006 and EPA-SAB-CASAC-CON-00-007, respectively).
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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.
We look forward to your response.
Sincerely,
/s/
Dr. Joe L. Mauderly, Chair
Clean Air Scientific Advisory Committee
Enclosure
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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 of Chemistry, Clarkson University, Potsdam, NY
Dr. Eva J. Pell,, Steimer Professor of Agricultural Sciences, Pennsylvania State University, University
Park, PA
Dr. Arthur C. Upton, M.D., Director, Independent Peer Review, CRESP, Environmental and
Occupational Health Sciences Institute, Piscataway, NJ
Dr. Sverre Vedal, M.D., Professor of Medicine, University of British Columbia, 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 Officer (DFO) and Team Leader, Committee Operations
Staff, US Environmental Protection Agency, Science Advisory Board, Washington, DC
Ms. Diana Pozun, Management Assistant, US Environmental Protection Agency, Science Advisory
Board, Washington, DC
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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.
Distribution and Availability: This Science Advisory Board report is provided to the EPA
Administrator, senior Agency management, appropriate program staff, interested members of the
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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
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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May 8, 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
Subject: Advisory on the PM2 5 Monitoring Network
Dear Dr. Mauderly:
The Technical Subcommittee on Fine Particle Monitoring of the Clean Air Scientific Advisory
Committee (CASAC), met on April 18 and 19, 2000 to conduct an Advisory on the PM 2.5 Monitoring
Network, in a public meeting in Research Triangle Park, NC.
There were three issues that were brought to the Subcommittee's attention for our advice and
recommendations: a) the deployment and future plans for the PM2 5 monitoring network; b) the approach
to be used for the analysis of carbon species in samples collected in the chemical speciation monitoring
network; and c) the sampling strategy for coarse particles should a coarse particle NAAQS be developed
in the 2002 standard setting process.
The PM monitoring network includes the compliance mass monitoring network, the chemical
speciation network, and the supersites. Each network is currently in a different stage of deployment.
Most of the mass monitors are in place. Initial data capture rates are reasonable for such a rapid
implementation process, and it appears that the data completeness is improving as experience is gained in
sampler operation. The data quality indicators provided suggest that the precision of the samplers and
related mass determinations are very good. This high precision is likely to result from the stringent
protocols developed for the Federal Reference Method (FRM) measurements. The use of co-located
samplers and the Performance Evaluation Program (PEP) audits appear to contribute to this precision.
However, with increased experience, it is clear that the current procedures put a substantial burden on the
state and local agency personnel who are responsible for servicing the samplers. Thus, the Subcommittee
recommends that the FRM procedures be assessed to determine if some of the rigidity in the sample
handling, and accompanying difficulties in implementation, could be reduced with a negligible loss of
precision. For example, could the 96 hour waiting period be extended? Is shipment in coolers with "blue
ice" necessary? Limited relaxation of the requirements could result in significant cost savings in the
labor required to perform the sampling while maintaining adequate precision in the measurements to meet
the data quality objectives.
A limited test of the operation of chemical speciation samplers by state and local air quality
agency personnel is currently underway following the initial tests in four cities and at the Atlanta
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supersite. The remainder of the National Trends Network will be deployed later this year, and the rest of
the samplers for the state and local agencies will be acquired and sited next year. The process has been
slowed from initial plans based on advice provided by this Subcommittee and other advisory bodies to
make more extensive tests of the sampler performance and field operation. These tests have clearly been
helpful in identifying and removing problems before extensive deployment occurs, and the start-up of the
speciation network appears to be proceeding well. The immediate issue in the network development is
the desire to coordinate of some of the state and local sites with the activities of the supersites and with
sites deployed by other jurisdictions. Efforts have been initiated to facilitate that coordination.
One of the difficulties in the implementation of the chemical analysis plans that have been made
for the samples from the Chemical Speciation Network is the determination of carbon species. These
species classifications are commonly designated as Organic Carbon (OC) and Elemental Carbon (EC) are
operationally defined, and there are currently two widely used methods. These methods are known as the
IMPROVE and National Institute of Occupational Safety and Health [NIOSH] protocols. Although these
protocols use different techniques to correct for pyrolysis of the organic carbon during the initial part of
the analysis cycle, the primary difference is in the temperature cycles applied to the samples. In
particular, in the NIOSH method, the sample is heated to 850°C in helium (He) while the IMPROVE
protocol does not include a high temperature step in the OC determination. Recent results suggest that
the reason that the IMPROVE procedure assigns more mass to elemental carbon relative to the NIOSH
method is that the material evolved under these 850°C/He conditions evolves only at the high
temperatures that are applied by IMPROVE protocol in the Elemental Carbon (EC) portion of the
procedure. Thus, the two methods, as commonly applied, produce significantly different values for the
OC and EC fractions. EPA has proposed to separately report the lower temperature He atmosphere
results as OC, the 850°C/He material as a separate entity, and the EC as the high temperature helium-
oxygen atmosphere material. Thus, in order to compare with earlier IMPROVE results, this 850°C/He
peak can added to the EC. The Subcommittee concurs with this proposal. However, further study on the
issue is highly recommended. Thus, there is the problem of potentially overestimating the OC because of
the high temperature step in the NIOSH method. It has been observed in some cases particularly for
rural samples that the reflectivity or transmissivity of the filter returns to the initial value before initiating
the step with oxygen in the support gas. Anecdotal evidence suggests a difference between rural and
urban samples. There can also be absorption of gaseous compounds onto the quartz filter. These effects
may result in an overestimation of the OC. This "positive artifact" problem of OC on quartz fiber filters
should be examined, with respect to differences, if any, that are observed between the two OC/EC
methodologies.
In addition, the Subcommittee recommends the study of the comparability of light absorption
methods with OC/EC measurements. As part of these studies, the comparability of continuous light
absorbing monitors with integrated measurements should be made, as well as the consistency of the total
carbon measurements made with continuous monitors. The aim of these studies would be the assessment
of the difference between total carbon and light-absorbing carbon as a measure of organic carbon. The
goal would be to move toward continuous monitors that provide more complete data with lower
operational costs if acceptable comparability can be demonstrated.
With respect to OC/EC determinations, the Subcommittee recommends that calibration standards
rather than reference materials be developed for the calibration of these methods. A reference material
would be samples of material comparable to ambient samples containing known concentrations of organic
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and elemental carbon. Because of the extreme difficulties in sampling and preserving ambient fine
particles that are truly representative of the materials that would be encountered in the atmosphere, the
effort to develop ambient aerosol reference materials is probably misguided. The development of
reproducible calibration standards would be more useful at this time. In addition, standards for calibration
of continuous total carbon analysis systems are also badly needed.
The cooperative agreements to establish and operate the seven Phase II supersites have been
awarded, and the investigators are in the process of organizing their individual operations. There are
concerns with respect to having a sufficient core of common measurements at all of the sites to provide a
strong data base for some uses such as air quality model evaluation. The Office of Air Quality Planning
and Standards (OAQPS) is making an effort to develop a more consistent set of core measurements. At
this point, a specific set of measurements has not been developed, and thus the Subcommittee cannot
comment on the appropriateness of the measurements included or excluded. Should the Agency develop
such a list, the Subcommittee could be asked to provide more specific advice with respect to its adequacy.
The Agency has made a good effort to develop voluntary collaborations among the supersites and, to the
extent possible, between supersites and other components of the PM monitoring and research programs,
such as the PM Health Effects Research Centers. Follow-up of these initial efforts will be needed to
develop and maintain the links that have been initiated, and the Subcommittee is heartened to see that
there seems to be a strong commitment to make this effort.
Continuous monitoring efforts are currently being deployed primarily for providing the data for
determining the Air Quality Index (Federal Register (FR), Air Quality Index Reporting; Final Rule, Vol.
64, No. 149, Wednesday, August 4, 1999, pp. 42530-42549). However, there is not currently a strong
effort to develop the Quality Assurance/Quality Control (QA/QC) and calibration methods to move them
toward an eventual replacement for the current FRM measurements. Substantial gains in data
completeness would be obtained by having an equivalent continuous mass monitoring method. Such data
would be highly useful both in assessing health effects and atmospheric processes. It would also lead to
lower costs of network operation, and more complete data for decision-making purposes. The
Subcommittee suggests that the current criteria for equivalency of continuous mass (particularly Class III
Equivalency) methods may be too rigid and difficult to attain relative to the significant gains in data
completeness and operational costs that would derive from the use of such samplers. Thus, the
Subcommittee strongly recommends that we discuss this matter at a meeting called for that purpose in the
near future.
The final issue was how to develop a coarse particle FRM sampler. Because of the U.S. Court
of Appeals for the District of Columbia Circuit's May 14, 1999 decision to vacate the revised coarse
particle (PM10) standard and EPA's subsequent decision not to contest the ruling, some measure of
coarse particles will have to be the indicator rather than PM10. There is, therefore, a need to have a
measurement method that will be used to ascertain compliance with any new coarse particle standard to
be promulgated in the future. In the presentation made to the Subcommittee, the Agency presented a
number of options. Most of these options were not practical to pursue given the target date of 2002 for
promulgation of revised PM NAAQS for fine and coarse particles. The options that could lead to a
coarse particle sampling system were based on modification of the existing PM2 5 FRM sampler. This
PM2 5 sampler configuration already incorporates many of the key features that are needed in a FRM
sampling system, such as volumetric flow control, and would not require as extensive laboratory and field
testing as would be required for any other new sampler. One option is to replace the WINS impactor
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with a straight tube so that the sampler collects PM10 instead of PM2 5. This option would require two
samplers (PM2 5 and PM10) to run side-by-side and the coarse particle fraction would be calculated by
difference. The Subcommittee agrees that the precision of the originally designated PM10 samplers is
insufficient to permit a difference measurement that would provide a meaningful indicator of coarse
particles. However, concern was raised with the problem of mixing coarse and fine in the PM10 sample.
There are cases where the acidic fine particles will chemically react with materials in the coarse particles,
resulting in the volatilization of some of the collected particulate matter.
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Another option was to utilize a polyurethane foam (PUF) plug in the WINS impactor as a
collection surface instead of oil. The weight gain in the PUF plug can provide the coarse particle mass
measurement. This approach also provides separate samples of the coarse and fine particles, eliminating
any chemical reaction problems. However, it might adsorb gaseous components of the atmosphere. Also
it is not clear that the PUF placement can be automated, and thus it might represent significantly more
effort in the field for the technicians servicing the instruments. It will also require more extensive testing
to determine the effect of the change in the coarse particle collection surface on the characteristics of the
PM2 5 samples. However, it appears to be an alternative worthy of careful exploration.
In any case, the Subcommittee wants to express its strong support for a change in the basic
approach to monitoring particles in both the coarse or fine size fractions in that the emphasis should be on
development of continuous monitoring methods over integrated filter methods. It is clear that there have
been substantial technological developments in continuous mass monitoring approaches, and the Agency
needs to move as rapidly as practical toward implementation of continuous monitoring methods of
particulate matter as is now used for most of the other criteria pollutants. Such continuous methods
provide a wealth of additional data that are not available with the current limited frequency integrated
mass measurements by FRM samplers. It also provides a significant cost savings in network operations
for the state and local agencies that are required to operate and maintain these networks. As an initial
step in this direction, the Subcommittee reiterates its desire to meet with the Agency soon to discuss the
problems associated with the current criteria for equivalency of continuous monitors for PM2 5 to the
FRM monitor.
Sincerely,
/s/
Dr. Philip 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
April 18-19, 2000 Meeting
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
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)
Dr. Morton Lippmann, Nelson Institute of Environmental Medicine, New York University, Tuxedo, NY
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
Dr. Carl M. Shy, Department of Epidemiology, University of North Carolina at Chapel Hill, School of
Public Health, Chapel Hill, NC
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
Dr. John R. Fowle, III, Designated Federal Officer, US EPA, Science Advisory Board (1400A), 1200
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Pennsylvania Ave, NW, Washington, DC 20460
Ms. Diana Pozun, Management Assistant, US EPA, Science Advisory Board (1400A), 1200
Pennsylvania Ave, NW, Washington, DC 20460
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