UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
March 1, 2002
OFFICE OF THE ADMINISTRATOR
SCIENCE ADVISORY BOARD
EPA-SAB-CASAC-LTR-02-001
Honorable Christine Todd Whitman
Administrator
U.S. Environmental Protection Agency
1200 Pennsylvania Avenue, NW
Washington, DC 20460
Subj ect : Revi e w of the Agency ' s draft Continuous Monitoring Implementation
Plan; a Review by the Clean Air Scientific Advisory Committee
Dear Governor Whitman:
The Subcommittee on Particle Monitoring (hereafter, the "Subcommittee") of the Clean
Air Scientific Advisory Committee (CASAC) met at EPA's Environmental Research Center in
Research Triangle Park, NC on Monday, January 28, 2002. The purpose of this meeting was to
review the draft document Continuous Monitoring Implementation Plan prepared by EPA's
Office of Air Quality Planning and Standards (OAQPS) and provide advice on implementation
of EPA's continuous PM monitoring program. The CASAC was asked to respond to the
following charge: a) program strengths; b) areas of concern; and c) any recommendations that
might optimize implementation of the PM continuous mass program.
This meeting of the CASAC Subcommittee on Parti culate Monitoring represents the next
in a series of steps that began in April 2000 when the question of the use of continuous mass
monitors in National Ambient Air Quality Standards (NAAQS) compliance measurements was
first raised. On January 22, 2001, a workshop was held by the Subcommittee. The purpose of
that workshop was to explore opportunities for accommodating emerging technologies into
routine air monitoring networks. The workshop was advertised and convened to provide states
and associations of states, vendors and manufacturers of monitoring equipment, and EPA staff
with an opportunity to share information and discuss emerging technologies and the implications
of considering continuous monitoring in EPA's regulatory monitoring program. The
Subcommittee made a series of recommendations in their subsequent letter to you on May 28,
2001 (EPA-SAB-CASAC-COM-0 1-003). We had requested OAQPS to provide a written
response to our report in which they would set forth an approach to move toward a substantial
use of continuous monitoring techniques in the compliance monitoring network as a replacement
and/or supplement for the current Federal Reference Method (FRM) samplers.
The problems with the FRM samplers are that they require considerable effort to operate
even on an every third-day basis and on that every third-day basis, they are not providing
sufficiently detailed data on airborne particle concentrations. The availability of continuous
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hourly data would be extremely valuable in evaluating health effects of airborne particles as well
as testing and applying the air quality models needed for air quality management strategy
development. At the same time, the use of continuous monitors would reduce the cost and
manpower needs to operate the current FRM network. We anticipate that such a shift to
continuous monitors could be achieved without a loss of integrity of the compliance monitoring
data that is needed to test attainment or non-attainment of the NAAQS for PM2 5.
In response to our discussions of last year, OAQPS produced a draft "Continuous
Monitoring Implementation Plan" for the Subcommittee's review and comments. Thus, the
focus of the current meeting was the discussion of this document and issues related to a process
for incorporating continuous mass monitors into the monitoring program. The Subcommittee
would like to compliment the OAQPS staff for their efforts in developing the present document.
It is clear that we are all working at finding approaches that will permit the use of continuous
monitors that will provide more detailed data while ensuring that we are continuing to provide
rigorous tests of air quality with respect to attainment of the PM25 NAAQS.
The EPA draft document outlines two approaches for using continuous monitors,
Regional Equivalency Method (REM), and Enhanced Correlated Acceptable Continuous
Methods (CAC). The REM process would result in the use of the continuous monitoring data for
compliance determinations, whereas the CAC process would be useable for all purposes except
compliance testing. An important innovation is the Agency's use of data quality objectives
(DQO) to design the equivalency rules. The Subcommittee strongly endorses the DQO approach
to determine how flexible the requirements can be and yet meet the needs of the Agency for
compliance determinations.
After discussion between the Subcommittee, the OAQPS staff, and others present at the
meeting, we agreed that the document presented a reasonable framework for the use of
continuous monitors. However, the Subcommittee is concerned that the process as currently
outlined puts a heavy burden on the state or local air quality agencies to demonstrate REM. This
effort may be more than can be mounted by many such organizations. Normally the burden for
equivalency demonstration is the responsibility of the vendors of the equipment, and the REM
approach shifts that effort to the agency wishing to qualify the sampler for their region. There
are other key issues regarding the regional approach that are difficult to resolve, such as the
definition on appropriate regional domains, and the potential for changes of such domains over
time. In addition, the REM process only permits a simple model to convert the continuous
monitor data into values that would be treated as equivalent to the FRM values. The model must
be of the form
FRM = a • CM + b
where FRM is the estimated FRM 24 hour mass concentration in |ig/m , CM is the measured 24
hour mass concentration (|ig/m ) estimated from the 24 one-hour values, and a and b are
empirical coefficients developed from measurements within a "region." Preliminary results
presented in the document show that such an approach could work in some areas of the country
such as the southeastern and northwestern US. However, such a model would not adequately
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reproduce the FRM values in much of the United States including the midwestern to the
northeastern portions of the country. A prior study in Switzerland (J. Heldstab and M. Stampfli
(2001) PM10 - Umrechnungsmodelle fur Teom - und Betameter -Messreihen, INFRAS,
Gerechtigkeitsgasse 20, Postfach, CH-8039 Zurich, Switzerland) found simple empirical
relationships that provide good correlations for both beta gauges and TEOMs for PM10. These
relationships account for the effects of temperature or day of year on mass concentration
measurements. Similarly, Bortnick, Coutant, and Eberly, (Journal of the Air & Waste
Management Association (2002), 52, 104-112) provides two examples of model development for
TEOMs with PM2 5 FRMs. One of the models uses temperature to get a better fit. The
Subcommittee expressed the hope that it may be possible to develop a similar semi-empirical
model, based on physical/chemical principles, that would provide adequate fits to the FRM data.
It will be necessary to establish appropriate Data Quality Objectives that would need to be
satisfied in order to apply this model for compliance purposes. It is possible that the model
would need to be tailored to specific locales. It would be worth exploring such approaches in
order to provide the opportunity for a larger portion of the country to be able to utilize a REM
approach.
The Subcommittee expressed the opinion that the current requirements for the REM
designation are inadequate, in that they do not require a sufficient correlation between the FRM
and CM data. We recommend that in addition to the requirements set out in the draft document,
there be a requirement that the squared correlation coefficient (r2) should be relatively high with
the value to be set by an appropriate Data Quality Objectives (DQO) process. It also may be
necessary to consider the concept of a "region" in a rather different manner. If one considers the
Northeastern US, areas with high emissions of diesels such as New York City, Boston, or
Philadelphia may have a different model than smaller cities such as Rochester, Worcester, and
Harrisburg. Thus, there may be several REM models for geographical regions because of
significant differences in the composition of the ambient PM.
The current document is a good step forward to achieving the goal of a substantial use of
continuous monitors in the compliance monitoring network, however, there are a number of
problems yet to be resolved. In addition to those already outlined, the issue of monitoring for
attainment of the 24-hour standard has not yet been addressed. Although we understand that the
annual average standard will be the controlling standard, it is necessary to ascertain attainment or
non-attainment of the 24-hour standard. There will also need to be a reduction of the total
number of FRM sites. It seems clear from the spatial analyses that have been done, that it will
be possible to decrease the total number of sites without compromising the confidence in the
attainment decisions that need to be made. However, it will be necessary to develop careful
guidance to the state and local agency to ensure that the smaller network provides appropriate
data for NAAQS decisions.
Because of some of the difficulties we anticipate in the implementation of the REM
approach, the Subcommittee suggests the following interim approach in order to begin moving
continuous monitors into the network while the details of the REM process are being developed
and finalized.
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a) For sites that would be utilized for NAAQS determinations (as envisioned in the
REM approach), co-locate a continuous monitor with an FRM and allow a
l-day-in-6 sampling frequency for the FRM. This compliance site would be an
ongoing co-location. A best-fit function could be developed based on the
dependent data set to which it is applied, assuring the potential for the best
transformation function possible. Each year, the best-fit function would be
updated for that year, preserving the ability to adjust the continuous data to the
best FRM-like data. Assuming the transformed continuous data met the Data
Quality Objectives (DQO's), (establishing what we might call a "site-specific
equivalency"), the daily data could be used for both annual and 24-hr NAAQS
determinations. If for some locations, a best-fit function falls short of DQO
objectives, the available l-in-6 FRM data are available for the purpose of making
attainment/non-attainment decisions.
b) For sites that would not be utilized for NAAQS determinations (as envisioned in
the CAC approach), we suggest that continuous and FRM monitors, with the
FRMs on a l-day-in-6 schedule, be co-located for the first year to establish an
appropriate transformation function. Thereafter, co-location would occur every
third year to confirm or update the transformation function.
This approach could be implemented quickly and without the extensive regulatory review
that would be required for the full REM/CAC approach. It potentially could be done within the
context of the approval of non-designated PM2.5 methods at specific individual sites in 40 CFR
58, Appendix C, section 2.4. It would permit the accumulation of data and allow further testing
of the broader approaches outlined in the document. Thus, we suggest that OAQPS consider this
as an interim approach while the details of other broader scale approaches are being refined.
Given that we are looking at potential major revisions of the parti culate matter NAAQS
next year, we suggest that it is an appropriate time to reexamine the Federal Equivalent Method
(FEM) designation approach that is currently in the regulations. It is the Subcommittee's
understanding that the equivalency rules were not based on a data quality objectives (DQO)
approach to determine how stringent the requirements needed to be and yet meet the needs of the
Agency for compliance determinations. The Subcommittee recommends that EPA undertake a
thorough DQO process to determine the needs for monitors so that the FEM requirements can be
defined based on a clearly defined set of data quality needs. This process may result in
regulations that are not seen as onerous as the current regulations and may encourage vendors to
develop FEM monitors.
Finally as a way to continue to move the process along, we request that by the end of
June 2002, OAQPS provide a revised draft of the document that would include the 24-hour
standard analysis and consideration of the comments provided in this report. We look forward to
continuing to work with the OAQPS staff on this important aspect of the PM NAAQS
compliance monitoring.
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The above Subcommittee report was reviewed and approved by the statutory CASAC at a
public teleconference meeting on February 27, 2002.
Sincerely,
/ Signed /
Dr. Philip Hopke, Chair
Clean Air Scientific Advisory
Committee
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U.S. Environmental Protection Agency
EPA Science Advisory Board
Clean Air Scientific Advisory Committee
CHAIR
Dr. Philip Hopke, Bayard D. Clarkson Distinguished Professor, Department of Chemical
Engineering, Clarkson University, Potsdam, NY
Also Member: Research Strategies Advisory Committee
Executive Committee
MEMBERS
Dr. Frederick J. Miller, Director, Respiratory and Neurotoxicology Research Program,
Chemical Industry Institute of Toxicology, Research Triangle Park, NC
Mr. Richard Poirot, Environmental Analyst, Air Pollution Control Division, Department of
Environmental Conservation, Vermont Agency of Natural Resources, Waterbury, VT
Dr. Frank Speizer, Edward Kass Professor of Medicine, Channing Laboratory, Harvard
Medical School, Boston, MA
Dr. George E. Taylor, Professor, Honors Program, George Mason University, Fairfax, VA
Dr. Sverre Vedal, Professor of Medicine, University of British Columbia, Respiratory Division,
Vancouver, BC Canada
Dr. Barbara Zielinska, Research Professor, Desert Research Institute, Reno, NV
EPA SCIENCE ADVISORY BOARD STAFF
Mr. A. Robert Flaak, Designated Federal Officer, US EPA, EPA Science Advisory Board,
1200 Pennsylvania Avenue, NW, Washington, DC
Ms. Rhonda Fortson, Management Assistant, US EPA, EPA Science Advisory Board, 1200
Pennsylvania Avenue, NW, Washington, DC
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U.S. Environmental Protection Agency
EPA Science Advisory Board
Clean Air Scientific Advisory Committee
CASAC Subcommittee on Particle Monitoring
CHAIR
Dr. Philip Hopke, Bayard D. Clarkson Distinguished Professor, Department of Chemical Engineering,
Clarkson University, Potsdam, NY
Also Member: Research Strategies Advisory Committee
Executive Committee
CASAC MEMBERS
Mr. Richard Poirot, Environmental Analyst, Air Pollution Control Division, Department of
Environmental Conservation, Vermont Agency of Natural Resources, Waterbury, VT
CONSULTANTS
Dr. Petros Koutrakis, Professor, Department of Environmental Sciences, School of Public Health,
Harvard University, Boston, MA
Dr. Debra L. Laskin, Professor, Department of Pharmacology & Toxicology, Environmental &
Occupational Health Sciences Institute, Rutgers University, Piscataway, NJ*
Dr. JoAnn S. Lighty, Associate Dean, University of Utah, Salt Lake City, UT*
Dr. Morton Lippmann, Professor, Nelson Institute of Environmental Medicine, New York University
Medical Center, Tuxedo, NY
Dr. Peter McMurry, Professor and Head, Department of Mechanical Engineering, University of
Minnesota, Minneapolis, MN
Dr. Kimberly Prather, Professor, University of California, Department of Chemistry, University of
California, Riverside*
Dr. Warren H. White, Senior Research Associate, Chemistry Department, Washington University, St.
Louis, MO
Dr. George T. Wolff, Principal Scientist, General Motors Corporation, Detroit, MI* *
Mr. Melvin Zeldin, Environmental Consultant, Sparks NV [Retired: Assistant Deputy Executive Officer,
Science and Technology Advancement, South Coast Air Quality Management District
(SCAQMD), Diamond Bar, CA]
* Did not attend meeting * * Attended via Teleconference
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EPA SCIENCE ADVISORY BOARD STAFF
Mr. A. Robert Flaak, Designated Federal Officer, US EPA, EPA Science Advisory Board, 1200
Pennsylvania Avenue, NW, Washington, DC
Ms. Rhonda Fortson, Management Assistant, US EPA, EPA Science Advisory Board, 1200
Pennsylvania Avenue, NW, Washington, DC,
Members of this SAB Panel consist of
a. SAB Members: Experts appointed by the Administrator to serve on one of the SAB Standing
Committees.
b. SAB Consultants: Experts appointed by the SAB Staff Director to a one-year term to serve on ad hoc
Panels formed to address a particular issue.
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NOTICE
This report has been written as part of the activities of the EPA 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
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does mention of trade names or commercial products constitute a recommendation for use.
Distribution and Availability: This EPA Science Advisory Board report is provided to the EPA
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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 [US EPA Science
Advisory Board (1400A), 1200 Pennsylvania Avenue, NW, Washington, DC 20460-0001; 202-
564-4533].
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