The National Ambient Air Quality Standard for Particulate Matter (PM): EPA's 2006 Revisions and Associated Issues

The National Ambient Air Quality Standard for
Particulate Matter (PM): EPA’s 2006 Revisions
and Associated Issues
November 26, 2008
Robert Esworthy
Specialist in Environmental Policy
Resources, Science, and Industry Division
James E. McCarthy
Specialist in Environmental Policy
Resources, Science, and Industry Division



The National Ambient Air Quality Standard for
Particulate Matter (PM): EPA’s 2006 Revisions and
Associated Issues
Summary
Following its review of more than 2,000 scientific studies, on October 17, 2006,
the EPA published its final revisions to the National Ambient Air Quality Standards
(NAAQS) for particulate matter (particulates, or PM). The U.S. Court of Appeals
for the District of Columbia Circuit’s pending decision regarding challenges to the
2006 PM NAAQS by several states and industry, agriculture, business, and public
advocacy groups, may prompt renewed interest in Congress. All briefs from
petitioners, EPA, and supporters were filed with the court by March 7, 2008, and oral
argument occurred September 15, 2008.
Although a tightening of the standards, the 2006 particulates NAAQS are not
as stringent as recommended by EPA staff or the independent scientific advisory
committee mandated under the Clean Air Act (Clean Air Scientific Advisory
Committee, or CASAC). The divergence from the CASAC’s recommendations
proved controversial, as did several other elements of the 2006 particulates NAAQS,
including the decision not to exclude rural sources from the coarse particle standard.
Some have also questioned the EPA’s strengthening of the standard for all fine
particles, without distinguishing their source or chemical composition.
The EPA found that the evidence continued to support associations between
exposure to particulates in ambient air and numerous significant health problems,
including aggravated asthma, chronic bronchitis, heart attacks, and premature death.
Based on several analytical approaches, the EPA estimated that compliance with the
revised NAAQS will prevent 1,200 to 13,000 premature deaths annually, as well as
substantial numbers of hospital admissions and missed work or school days due to
illness. Based on these findings, EPA revised the PM NAAQS by strengthening the
pre-existing (1997) standard for “fine” particulate matter 2.5 micrometers or less in
diameter (PM2.5) by lowering the allowable daily concentration averaged over 24-
hour periods of PM2.5 in the air. The annual PM2.5 standard, which is set in addition
to the daily standard to address human health effects from chronic exposures to the
pollutants, is unchanged from the 1997 standard.
The 2006 particulates NAAQS also retained the 24-hour standard and revoked
the annual standard for slightly larger, but still inhalable, particles less than or equal
to 10 micrometers (PM10). The EPA abandoned its proposal to replace the particle
size indicator of PM10 with a range of 10 to 2.5 micrometers (PM10-2.5).
The forthcoming implementation of the 2006 NAAQS, which includes
designating areas (typically defined by counties or portions of counties) as not
attaining the standard and adopting measures to achieve compliance, may generate
interest in Congress. Although EPA is not requiring new nonattainment designations
for PM10, the tightening of the PM2.5 standard will increase the number of areas in
nonattainment. In its preliminary recommendations submitted to states and tribes in
August 2008, EPA identified 215 counties as nonattainment for the 2006 NAAQS.



Contents
In troduction ......................................................1
EPA’s 2006 Changes to the Particulates NAAQS.........................2
The 2006 Particulates NAAQS...................................3
Implementing the 2006 PM NAAQS...............................5
Potential Impacts of the 2006 Particulates NAAQS.......................5
EPA’s Monetized Benefits and Cost Estimates.......................7
Potential Health Impacts........................................9
Potential Concerns and Issues .......................................11
Fine Particulate (PM2.5) Primary (Health) Standards..................12
Potential Health Benefits of a More Stringent PM2.5 Standard......15
Coarse Particulate (PM10) Primary Standards.......................17
Particle Size Indicator.....................................17
Rural PM10 Sources.......................................18
Secondary PM2.5 and PM10 Standards.............................20
Exclusion of More Recent Research..............................20
Synopses of Stakeholder Reaction to the 2006 Particulates NAAQS.....21
Conclusions .....................................................23
Appendix. PM10 NAAQS Geographic Nonattainment Areas...............24
List of Figures
Figure 1. Status of Current PM10 Nonattainment Areas,
Based on 2004-2006 Air Quality.................................25
List of Tables
Table 1. Primary (Health) NAAQS for PM2.5 and PM10: Final Revisions
(2006), and Previously Promulgated...............................4
Table 2. EPA’s Estimated Total Annual Monetized Benefits and Costs
of Attaining Alternative PM2.5 NAAQS in 2020......................8
Table 3. EPA’s Predicted Reductions in Adverse Health Effects
Annually in 2020 Associated with Meeting
the 2006 PM2.5 NAAQS........................................10
Table 5. PM2.5 Primary (Health) NAAQS: Final (2006),
Proposed and Alternatives, and as Promulgated
in 1997.....................................................13
Table 6. EPA’s Predicted Reductions in Adverse Health Effects
Annually in 2020 Associated with Meeting
the 2006 PM2.5 NAAQS and a
More Stringent Alternative.....................................16



The National Ambient Air Quality Standard for
Particulate Matter (PM): EPA’s 2006
Revisions and Associated Issues
Introduction
The EPA has identified and promulgated National Ambient Air Quality
Standards (NAAQS) under the Clean Air Act (CAA)1 for six principal pollutants
commonly referred to as “criteria pollutants”: particulate matter (PM), ozone (O3, a
key measure of smog), nitrogen dioxide (NO2, or, inclusively, nitrogen oxides,2
NOx), sulfur oxides (SOx, or, specifically, SO2), carbon monoxide (CO), and lead
(Pb). On October 17, 2006, the EPA published its revisions to the NAAQS for
particulates to provide protection against potential health effects associated with
short- and long-term exposure to particulate matter (including chronic respiratory
disease and premature mortality).3
The EPA’s revised particulates NAAQS modified the standards established in

19874 that focused on particles smaller than 10 microns (PM10, or coarse particles),


and standards for “fine” particles smaller than 2.5 microns (PM2.5) introduced for the
first time with the promulgation of the 1997 PM2.5 NAAQS.5 The 2006 revisions to
the particulates NAAQS were the culmination of the EPA’s statutorily required
periodic review,6 based on its evaluation and analysis of more than 2,000 scientific
studies available between 1997 and 2002, and on determinations made by the
Administrator. The EPA’s review of the particulates NAAQS and of the scientific
criteria for setting the standards completed in 2006 was initiated not long after the

1997 promulgation.


1 Sections 108-109 of the Clean Air Act.
2 The NAAQS is for NO2; nitrogen gases that are ozone precursors are referred to as NOx.
3 71 Federal Register 61143-61233, October 17, 2006. See also EPA’s PM Regulatory
Actions website at [http://epa.gov/pm/actions.html].
4 52 Federal Register 24634-24715, July 1, 1987.
5 62 Federal Register 38652-38896, July 18, 1997. See CRS Report RL32431, Particulate
Matter (PM2.5): Implementation of the 1997 National Ambient Air Quality Standards
(NAAQS), by Robert Esworthy.
6 Section 109(d)(1) of the CAA. According to the statute, the EPA is required to review the
latest scientific studies and either reaffirm or modify the NAAQS every five years, however
EPA has rarely met this requirement and in some cases has been forced to comply through
litigation.

The 2006 particulates NAAQS generated national interest and debate, and
oversight in Congress, as did the previous changes to the particulates standards
promulgated in 1997. While the 2006 particulates NAAQS generally tightened the
air quality standards for fine particulate matter, the action caused considerable
controversy, including concerns that the standards were outside the range
recommended by both EPA staff and by the scientific advisory panel (Clean Air
Scientific Advisory Committee, or CASAC7) established by the Clean Air Act
(CAA).8 Conversely, some contended that available data did not support the need for
stricter standards or, in some cases, the standards as promulgated in 1997.
In December 2006, 13 states and the District of Columbia petitioned the U.S.
Court of Appeals for the D.C. Circuit to review the 2006 particulates NAAQS. In
addition, several groups representing various industry and agriculture interests
(including coal, iron, steel, and corn refiners, oilseed processors, farmers, and cattle
and pork producers), as well as environmental and public health organizations, also
filed petitions to the D.C. Circuit challenging the 2006 NAAQS.9 Briefs from
petitioners, EPA, and supporters were filed with the court by March 7, 2008, and oral
argument occurred September 15, 2008.10 Relatedly, the D.C. Circuit Court’s July
2008 decision to vacate EPA’s 2005 Clean Air Interstate Rule (CAIR) has
implications for implementing the 1997 and the 2006 NAAQS, and has garnered
attention in Congress.11
This report provides an analysis of the agency’s final 2006 revisions to the
particulates NAAQS, and the estimated costs and benefits of the revised standards
and of more stringent alternatives analyzed. The report highlights concerns and
issues raised regarding the revisions to the particulates standards, including those of
the science advisory committee (CASAC), and actions in Congress.
EPA’s 2006 Changes to the Particulates NAAQS
Establishing NAAQS does not directly limit emissions; rather, it represents the
EPA Administrator’s formal judgment regarding the level of ambient pollution that
will protect public health with an adequate margin of safety. Under Sections 108-

109 of the CAA, Congress mandated that the EPA set national ambient (outdoor) air


7 For information regarding the CASAC PM review panel and its activities and reports, see
[http://yosemite.epa.gov/sab/sabpeople.nsf/WebCommittees/CASAC].
8 Section 109(d)(2)of the Clean Air Act.
9 Cases have been consolidated with American Farm Bureau Federation v. U.S. EPA, No.

06-1410 (D.C. Cir. 2006).


10 American Farm Bureau Federation v. U.S. EPA, No. 06-1410 (D.C. Cir. , oral argument
September 15, 2008).
11 For a more detailed discussion of the court’s decision and its implications, see CRS
Report RL34589, Clean Air After the CAIR Decision: Back to Square One?, by James E.
McCarthy, Larry Parker and Robert Meltz; also see related discussion in CRS Report
RL32431, Particulate Matter (PM2.5): Implementation of the 1997 National Ambient Air
Quality Standards (NAAQS), by Robert Esworthy.

quality standards for pollutants whose emissions “may reasonably be anticipated to
endanger public health (primary standards) or welfare12 (secondary standards)” and
“the presence of which in the ambient air results from numerous or diverse mobile
or stationary sources.” The statute also requires that every five years EPA review the
latest scientific studies and either reaffirm or modify previously established NAAQS.
The 2006 Particulates NAAQS
The EPA’s review of PM found that the scientific evidence since 1997
reinforced the associations between exposure to particulates and numerous
cardiovascular and respiratory health problems, including aggravated asthma, chronic
bronchitis, reduced lung function, irregular heartbeat, nonfatal heart attacks, and
premature death. The CASAC found that the numerous epidemiological studies
EPA reviewed “...have shown statistically significant associations between the
concentrations of ambient air PM2.5 and PM10 (including levels that are lower than the
1997 particulates NAAQS) and excess mortality and morbidity.”13 Further, the EPA
concluded, and most of the CASAC panel concurred, that the scientific evidence
supported modifying the particulates standards.
The 1997 primary NAAQS for both PM2.5 and PM10 included an annual and a
daily (24-hour) limit. To attain the annual standard, the three-year average of the
weighted annual arithmetic mean PM concentration at each monitor within an area
must not exceed the maximum limit set by the agency. The 24-hour standards were
a concentration-based percentile form, indicating the percentage of the time that a
monitoring station can exceed the standard. For example, a 98th percentile 24-hour
standard indicates that a monitoring station can exceed the standard 2% of the days
during the year.
As modified and published in the October 17, 2006, Federal Register Notice,
the primary PM2.5 and PM10 standards are as follows:
!PM2.5: strengthened the daily (24-hour) standard, which had allowed
no more than 65 micrograms per cubic meter (µg/m3), by setting a3th
new limit of 35 µg/m, based on the three-year average of the 98
percentile of 24-hour PM2.5 concentrations; retained the annual3
standard at 15 µg/m.


12 The use of public welfare in the CAA “includes, but is not limited to, effects on soils,
water, crops, vegetation, manmade materials, animals, wildlife, weather, visibility, and
climate, damage to and deterioration of property, and hazards to transportation, as well as
effects on economic values and on personal comfort and well-being, whether caused by
transformation, conversion, or combination with other air pollutants” (42 U.S.C. 7602(h)).
13 CASAC Particulate Matter (PM) review of EPA’s Review of the National Ambient Air
Quality Standards for Particulate Matter: Policy Assessment of Scientific and Technical
Information (Second Draft PM Staff Paper, January 2005, EPA-SAB-CASAC-05-007, June
6, 2005), available on the EPA CASAC website, see “Final Reports by Fiscal Year” at
[http://yosemite.epa.gov/sab/sabproduct.nsf/WebReportsbyYearCASAC] .

!PM10: retained the daily (24-hour) standard at 150 µg/m3 but
changes from the 99th percentile to no more than one exceedance per
year on average over three years; eliminated the annual maximum
concentration (50 µg/m3) standard for PM10.14
For PM2.5 and PM10, the secondary (welfare) NAAQS are the same as the primary
standards. Table 1 below provides a comparison of the revised primary NAAQS
with those previously promulgated for both PM2.5 and PM10.
Table 1. Primary (Health) NAAQS for PM2.5 and PM10: Final
Revisions (2006), and Previously Promulgated
Previous NAAQSEPA Final Rule (2006)
PM2.5 (Fine)

24-Hour Primary Standard65 µg/m335 µg/m3


Annual Primary Standard15 µg/m315 µg/m3
PM10 (Coarse)

24-Hour Primary Standard150 µg/m3150 µg/m3


Annual Primary Standard50 µg/m3Revoked
Source: Prepared by the Congressional Research Service (CRS), with information from the EPAs
final particulates NAAQS (71 Federal Register 61143-61233, Oct. 17, 2006), and related technical15
documents, available at [http://www.epa.gov/air/particles/actions.html].
EPA’s final revisions to the standards for fine particulates (PM2.5) were the same
as the agency had proposed in January 2006. However, the 2006 EPA revisions to
the PM2.5 NAAQS, while tightening the standards, were not as stringent as those
recommended by the CASAC and by the EPA staff.
With regard to coarse particulates, the EPA had proposed replacing the current
particle size indicator of PM10 with a range of 10 to 2.5 micrometers (PM10-2.5),
referred to as inhalable (or thoracic) coarse particles, and setting a PM10-2.5 daily3 3
standard of 70 µg/mrather than the current PM10 daily standard of 150 µg/m. The
proposal also included narrowing the focus of the PM10-2.5 standard to “urban and
industrial” sources and excluding particles typical to rural areas, including
“windblown dust and soils and particulates generated by agricultural and mining
sources.” The range of alternative standards considered and proposed and issues
associated with the EPA’s final decisions are discussed later in this report.


14 Based on the findings in the EPA PM criteria document and staff paper, and the CASAC’s
concurrence, that the studies reviewed do not provide sufficient evidence regarding long-
term exposure to warrant continuation of an annual standard, see 71 Federal Register 2653,
Section III. Rationale for Proposed Decision on Primary PM10 Standards, January 17, 2006.
15 EPA’s final PM staff paper and the CASAC review of the EPA staff paper
[http://www.epa.go v/ttn/naaqs/standards/pm/s_pm_index.html ].

Implementing the 2006 PM NAAQS
Promulgation of NAAQS sets in motion a process under which the states and
the EPA first identify geographic nonattainment areas, those areas failing to comply
with the NAAQS based on monitoring and analysis of relevant air quality data. The
EPA is not requiring new nonattainment designations for PM10 (see Figure 1 in
Appendix depicting PM10 nonattainment areas). However, the 2006 tightening of the
PM2.5 standards is expected to increase the number of areas (typically defined by
counties or portions of counties) in nonattainment.
In response to recommendations submitted by states, in August 2008, EPA
identified 169 counties and portions of 46 additional counties for designation as
nonattainment only for the revised 2006 24-hour PM2.5 standard. While many of these
counties identified for consideration overlap with the final nonattainment
designations for the 1997 PM2.5 NAAQS, most designations for the 1997 NAAQS
were based on nonattainment only for the annual standard. EPA expects to finalize
the nonattainment designations (based on 2005-2007 monitoring data) for the 200616
PM NAAQs by the end of 2008 with an effective date of April 2009.
Following formal designation, the states have three years (until April 2012
based on the current schedule) to submit State Implementation Plans (SIPs), which
identify specific regulations and emission control requirements that will bring an area
into compliance. In addition to requiring states to submit implementation plans,
EPA acts to control NAAQS pollutants through national standards. These may be
in the form of regulations of products that might emit the pollutants (particularly
fuels) and in the form of emission standards for new stationary sources (e.g., utilities,
refineries). States would be required to meet the 2006 PM2.5 standard no later than
five years from the effective date of designations (or no later than 10 years if
qualified for an extension).
Potential Impacts of the 2006 Particulates NAAQS
As discussed above, in setting and revising the NAAQS, the CAA directs the
EPA Administrator to protect public health with an adequate margin of safety. This
language has been interpreted, both by the agency and by the courts, as requiring
standards based on a review of the health impacts, without consideration of the costs,17
technological feasibility, or other non-health criteria. Costs and feasibility are
generally taken into account in NAAQS implementation (a process that is primarily
a state responsibility).


16 See EPA’s guidance on its website “Area Designations for 2006 24-Hour PM2.5 NAAQS
- Technical Information,” [http://www.epa.gov/ttn/naaqs/pm/pm25_2006_techinfo.html].
17 With regard to the non-relevance of cost considerations, see generally Whitman v.
American Trucking Associations, 531 U.S. 457, 465-472, 475-76 (2001).

Nevertheless, the EPA released a regulatory impact analysis (RIA) on October
6, 2006,18 to meet its obligations under Executive Order 12866 and in compliance
with guidance from the White House Office of Management and Budget.19 The RIA
only analyzed the benefits and costs of implementing the PM2.5 NAAQS. Citing
time, data, and modeling limitations, the EPA did not analyze the benefits and costs
of retaining the PM10 standard.
The EPA emphasized that the October 2006 RIA differed from typical RIAs in
that it did not analyze the regulatory impact of an action, and that it is primarily for
illustrative purposes. The basis for the benefits calculations are reductions in ambient
concentrations of PM2.5 resulting from a reasonable, but speculative, array of
cost-effective state implementation strategies selected by the EPA for purposes of
analysis. The analysis does not model the specific actions that each state will
undertake in implementing the 2006 PM2.5 NAAQS. The EPA includes a detailed
discussion of the limitations and uncertainties associated with the analysis.
In its impact analysis, EPA’s estimated baseline case incorporated expected
impacts of other national regulations that contribute to lowering PM2.5 concentrations
in future years. These other regulations included those addressing emissions from the
power generation sector, namely the 2005 Clean Air Interstate Rule (CAIR).20
However, in a July 11, 2008 decision (North Carolina v. EPA), the U.S. Court of
Appeals for the D.C. Circuit vacated CAIR in its entirety.21 CAIR was expected to
serve as the primary tool to assist downwind states in meeting the PM2.5 (and 8-hour
ozone) NAAQS by mitigating interstate transport of sulfur dioxide (SO2) and
nitrogen oxide (NOx) emissions from electric generating units that contribute to the
formation of PM2.5.22


18 EPA’s Regulatory Impact Analysis (RIA) of the 2006 National Ambient Air Quality
Standards for Fine Particle Pollution (PM2.5), available on EPA’s website at
[http://www.epa.go v/ttn/ecas/ria.html ].
19 58 Federal Register 51735, October 4, 1993. See the White House OMB website,
Regulatory Matters at [http://www.whitehouse.gov/omb/inforeg/regpol.html#rr].
20 CAA, 42 U.S.C. 7401 et seq., 70 Federal Register 25162, May 12, 2005.
21 No. 05-1244, 2008 WL 2698180 (D.C. Cir. July 11, 2008). See CRS Report RL34589,
Clean Air After the CAIR Decision: Back to Square One?, by James E. McCarthy, Larry
Parker, and Robert Meltz.
22 Sulfur dioxide (SO2) is a precursor contributing to the formation of PM2.5 concentrations,
and NOx is a precursor (a pollutant that is transformed in air to form another air pollutant)
contributing to the formation of both ozone and PM2.5 concentrations. EPA has concluded
that SO2 and NOx emissions, through the phenomenon of air pollution transport, contribute
significantly to downwind nonattainment, or interfere with maintenance, of the PM2.5 and

8-hour ozone NAAQS (70 Federal Register 25162, May 12, 2005).



EPA’s Monetized Benefits and Cost Estimates23
The EPA estimated incremental costs of attaining the revised PM2.5 standard
based on a set of assumptions and extrapolations regarding currently designated
nonattainment areas, likely control strategies and technologies and their associated
engineering costs, emissions inventories and sources, and regional variability. The
EPA emphasized that the technologies and control strategies selected for analysis
only illustrate one way for nonattainment areas to reach attainment, and that states
will compile and evaluate a variety of programs and adopt those attainment strategies
best suited for their specific local conditions. For purposes of comparing costs with
monetized benefits, the EPA estimated that the total annual mean social cost of
attainment of the revised PM2.5 NAAQS incremental to attainment of the 1997
standards would be $5.4 billion in 2020.
EPA’s estimates of the monetized benefits of complying with the revised PM2.5
standard reflect the valuation associated with predicted reductions in the incidence
of certain health and social welfare effects. In the RIA, the EPA presented a variety
of benefits estimates based on several published epidemiological studies, including
an American Cancer Society (ACS) Study24 used in previous RIAs, and the Harvard
Six Cities Study,25 as well as an expert elicitation study conducted by the EPA in
2006.26 The EPA estimated the total annual monetized benefits of attaining the
revised PM2.5 NAAQS would range from $15 billion to $17 billion based on the
mortality function from the ACS study and morbidity function from the published
studies. Using the mortality function developed from the expert elicitation in
conjunction with the morbidity function from the published studies, the EPA’s total
annual benefits are estimated to range from $8 billion to $76 billion in 2020. The
EPA’s estimated monetized benefits for 2020, like the cost estimates, were based on
the EPA’s projected compliance schedule and are incremental to compliance with the

1997 PM2.5 NAAQS by 2015.


According to the October 6, 2006, RIA, the estimated total annual health and
welfare net benefits (subtracting social costs from the monetized benefits) in 2020
of attaining the 2006 PM2.5 NAAQS ranged from $9 billion to $12 billion, based on
modeling of morbidity and mortality using published epidemiology studies, and from


23 EPA’s RIA of the 2006 NAAQS for Fine Particle Pollution (PM2.5), available on EPA’s
website at [http://www.epa.gov/ttn/ecas/ria.html].
24 Pope, C. Arden, III, et al. “Particulate Air Pollution as a Predictor of Mortality in a
Prospective Study of U.S. Adults.” American Journal of Respiratory and Critical Care
Medicine 151 (1995): 669-674.
25 Dockery, Douglas W., et al. “An Association Between Air Pollution and Mortality in Six
U.S. Cities.” New England Journal of Medicine 329 (1993): 1753-1759. See also the Health
Effects Institute, “Statement: Synopsis of the Particle Epidemiology Reanalysis Project.”
Reanalysis of the Harvard Six Cities Study and the American Cancer Society Study of
Particulate Air Pollution and Mortality, July 2000 (includes November 1, 2001 errata
sheet), p. I. ([http://pubs.healtheffects.org/getfile.php?u=271]).
26 See Chapter 5 of the EPA’s October 6, 2006, RIA [http://www.epa.gov/ttn/ecas/ria.html].

$2.4 billion to $70 billion, based on derivation from expert elicitation. Table 2
below presents a range of the EPA’s cost and monetized benefits estimates.
Table 2. EPA’s Estimated Total Annual Monetized Benefits and
Costs of Attaining Alternative PM2.5 NAAQS in 2020
(1999 $ in billions)

2006 PM2.5 NAAQS (15/35 µg/m3)


Discount RateBenefitsCostNet Benefits
Benefits based on American Cancer Society Study Mortality Function and Published
Scientific Literature Morbidity Functions
3%$17$5.4$12
7%$15$5.4$9
Benefits Range based on Expert Elicitation Derived Mortality Function and Published
Scientific Literature Morbidity Functions
Low MeanHigh MeanLow MeanHigh Mean
3% $9 $76 $5.4 $3.5 $70
7% $8 $54 $5.4 $2.4 $59
Note: Estimates (costs and benefits) reflect attainment in 2020, which includes implementation of
several national programs and are incremental to compliance with the 1997 PM2.5 NAAQS. The
discount rates are as recommended in the EPAs Guidelines for Preparing Economic Analyses (2000)
and OMB Circular A-4 (2003).
Source: Prepared by the Congressional Research Service using data from the Environmental
Protection Agencys Regulatory Impact Analysis (RIA) of the 2006 National Ambient Air Quality
Standards for Fine Particle Pollution (PM2.5), Table ES-1, p. ES-7, available on the EPAs website
at [http://www.epa.gov/ttn/ecas/ria.html]. Estimates and results have been rounded.
The EPA’s benefits and cost estimates were in terms of 1999 dollars and were
incremental to the agency’s modeled attainment strategy for the 1997 PM2.5 NAAQS
by 2015. The baseline case incorporated expected impacts associated with
implementation of recent national regulations addressing emissions from the power
generation sector, including the CAIR,27 as well as various mobile sources, that
contribute to lowering PM2.5 concentrations in future years.
In addition to the monetized health benefits estimates, the EPA estimated the
monetary benefits associated with improvements in visibility in selected Class I28
national parks and wilderness areas. The EPA primarily used a stated preference
approach which estimates values based on sampling surveys asking people what
amount of compensation would be equivalent to a defined improvement in
environmental quality. Extrapolating the results of a study based on a 1988 survey


27 70 Federal Register 25162, May 12, 2005.
28 Defined as areas of the country such as national parks, national wilderness areas, and
national monuments that have been set aside under Section 162(a) of the Clean Air Act to
receive the most stringent degree of air quality protection.

on recreational visibility value, the EPA estimated visibility “willingness to pay”
benefits to be $530 million in 2020 with attainment of the 2006 PM2.5 NAAQS.29
EPA estimated the cost and benefits of a more stringent alternative PM2.5 for
purposes of comparative analysis. The comparative results are discussed in the
“Potential Concerns and Issues” section of this report.
Potential Health Impacts
According to the January 2008 EPA report entitled Latest Findings on National
Air Quality Status and Trends Through 2006,30 nationally, annual PM2.5
concentrations declined by 14% between 2000 and 2006. For PM2.5 the areas that
showed the greatest improvement were the ones that had the highest concentrations
in the earlier years. Decreasing concentrations in southern California were largely
the result of decreasing levels of nitrate particles; organic carbon levels remained
relatively unchanged and have been the largest component of PM2.5 in southern
California. The Southeast had little change in PM2.5. The industrial Midwest and the
Northeast showed decreasing concentrations, mostly due to reductions in nitrates and
sulfates. Despite this progress, in 2006 nearly 67 million people lived in counties
with measured concentrations exceeding the annual PM2.5 national air quality
standard (based on one-year metric, not the three-year average).31
For purposes of illustration, Table 3 summarizes the EPA’s predicted
reductions in the incidence of a range of adverse health effects annually in 2020 for
the 2006 PM2.5 NAAQS (15/35 µg/m3), as reported in its RIA. The range of the
estimated mean number of reductions in premature deaths is based on the EPA’s
derivations using the ACS and the Harvard Six-City studies. EPA’s mean estimates
for the remaining adverse health effects were based on various epidemiology studies.
The EPA health effects estimates were a primary component of its derivations of the
monetized benefits discussed above.


29 See Appendix I in Visibility Benefits Methodology of the EPA’s October 6, 2006, RIA
[http://www.epa.go v/ttn/ecas/ria.html ].
30 EPA-454/R-07-007, January 2008 [http://www.epa.gov/air/airtrends/2007/].
31 Refers to trends in the measured PM2.5 concentrations relative to their air quality standards
in those areas where monitors are located across the country, and does reflect all designated
nonattainment areas. The combined population residing in EPA’s final PM2.5 nonattainment
designation areas, consisting of 208 counties in 20 states and the District of Columbia, is
almost 90 million.

Table 3. EPA’s Predicted Reductions in Adverse Health Effects
Annually in 2020 Associated with Meeting the 2006 PM2.5 NAAQS
Predicted Reductionsa
Adverse Health Effect(estimated mean)
Premature deaths in individuals with preexisting2,500 to 5,700b
cardiovascular and respiratory disease
Cases of chronic bronchitis (age >25)2,600
Cases of acute bronchitis (age 8-12)7,300
Nonfatal heart attacks (age >71)5,000
Hospital admissions for cardiovascular or respiratory1,630
symptoms (age >17)
Emergency room visits for asthma (age <19)1,200
Cases of aggravated asthma (asthmatics age 6-18)51,000
Cases of upper and lower respiratory symptoms (asthmatics97,000
age 6-18)
Days when individuals miss work (age 18-75)350,000
Days when individuals must restrict their activities because2,000,000
of symptoms related to particle pollution (age 18-65)
a.For consistency with the emissions and benefits modeling, the EPA used national population
estimates based on the U.S. Census Bureau projections. U.S. Bureau of Census. 2000.
Population Projections of the United States by Age, Sex, Race, Hispanic Origin and Nativity:
1999 to 2100. Population Projections Program, Population Division, U.S. Census Bureau,
Available at [http://www.census.gov/population/projections/nation/summary/np-t.txt].
b.The range of estimates reflects the mean estimates derived from the American Cancer Society
study and the Harvard Six-City Study, respectively.
Source: Prepared by the Congressional Research Service with data based on epidemiology studies
presented in Chapter 5 of the Environmental Protection Agency Regulatory Impact Analysis of the
2006 National Ambient Air Quality Standards for Fine Particle Pollution (PM2.5) Oct. 6, 2006, and
available on the EPAs website at [http://www.epa.gov/ttn/ecas/ria.html]. Estimates are rounded by
EPA to two significant digits.
In addition to the expected improved health benefits based on the epidemiology
studies, the EPA estimated reductions in premature mortality based on the expert
elicitation approach discussed above. The estimates were variable from expert to
expert, ranging from a mean of 1,200 to 13,000 avoided premature deaths annually3
in 2020 resulting from attainment of the 2006 standards (15/35 µg/m) incremental
to the EPA’s baseline strategy for the 1997 PM2.5 NAAQS (15/65 µg/m3).
When promulgating the 1997 PM2.5 NAAQS, the EPA estimated that
compliance would result in the annual prevention of 15,000 premature deaths, 75,000
cases of chronic bronchitis, and 10,000 hospital admissions for respiratory and
cardiovascular disease, as well as other benefits. These estimates have been the
subject of significant debate and re-analysis. Since 1998, with dedicated funding



from Congress, the EPA accelerated its research and re-analysis on PM2.5 to better
understand the potential associated health effects and to develop ways to reduce
risks.32 The funding supported EPA intramural and extramural PM research projects
and the establishment of five university-based PM research centers around the
country. The EPA’s most recent review has increased its confidence in earlier
findings associating exposure to PM2.5 with increases in respiratory health problems,
hospitalizations for heart and lung disease, and premature death, particularly for
children, the elderly, and those with preexisting heart and lung disease.33
Potential Concerns and Issues
Congress and a wide variety of stakeholders closely followed the development
of the 2006 particulates NAAQS since EPA’s review began nearly 10 years ago.
Congressional hearings have been held regarding implementation and review of the34
particulates NAAQS. Well before the EPA formally proposed revising the
particulates NAAQS, stakeholders were providing evidence and arguments at public
hearings and other forums for their preferred recommendations. In general, business
and industry opposed more stringent standards, and public health and environmental
interest groups advocated tighter standards. The EPA received thousands of
comments during various stages of development of the particulates criteria document
and in response to drafts of the EPA particulates staff paper. The agency reported
receiving more than 120,000 comments in response to the January 2006 particulates
NAAQS proposal.
The Administrator’s proposed and final decisions represented the first time in
the nearly 30-year history of the Clean Air Scientific Advisory Committee (CASAC)
that the promulgated standards fell outside of the range of the scientific panel’s
recommendations.35 In letters dated March 21, 2006, and September 29, 2006, the
CASAC raised its concerns and objections regarding both PM10 and PM2.5 proposed


32 Congress increased EPA’s appropriations for particulate matter research from $18.8
million in FY1997 (H.Rept. 104-812) to $49.6 million in FY1998 (H.Rept. 105-297). PM
research appropriations averaged more than $60 million per year from FY1999 through
FY2004, and Congress provided $60.5 million for FY2005. Congress has not identified PM
research funding since FY2005.
33 EPA criteria and technical documents in support of the October 17, 2006, final
particulates NAAQS, the December 20, 2005, proposal, and the 1997 NAAQS, are available
at [http://www.epa.gov/ttn/naaqs/standards/pm/s_pm_index.html].
34 U.S. Senate Committee on Environment and Public Works, full Committee, The Science
and Risk Assessment Behind the EPA’s Proposed Revisions to the Particulate Matter Air
Quality Standards, July 19, 2006; Subcommittee on Clean Air, Climate Change, and
Nuclear Safety, EPA’s Proposed Revisions to the Particulate Matter Air Quality Standards,
July 13, 2006, and Implementation of the Existing Particulate Matter and Ozone Air Quality
Standards, November 10, 2005.
35 For a discussion of recent issues regarding the CASAC, see CRS Report RL33807, Air
Quality Standards and Sound Science: What Role for CASAC? by James E. McCarthy.

standards.36 The Administrator is not required by statute to follow CASAC’s
recommendations; the act (in Section 307(d)(3)) requires only that the Administrator
set forth any pertinent findings, recommendations, and comments by CASAC and the
National Academy of Sciences, and, if his proposal differs in an important respect
from any of their recommendations, provide an explanation of the reasons for such
differences. Courts, in reviewing EPA regulations, also generally defer to the
Administrator’s judgment on scientific matters, focusing more on issues of
procedure, jurisdiction, and standing. Nevertheless, CASAC’s detailed objections to
the Administrator’s decisions and its description of the process as having failed to
meet statutory and procedural requirements could play a role in litigation challenging
the standards.
At the time of its January 2006 proposal, the agency solicited comment
regarding its supporting analysis and a variety of alternative particulates NAAQS.
In some cases the EPA revised elements of its proposal based on certain comments;
in other cases the EPA laid out its reasoning for disagreeing. EPA’s final
modifications to the existing particulates NAAQS sparked interest and conflicting
concerns among a diverse array of stakeholders and in Congress. The following
sections highlight several areas of interest.
Fine Particulate (PM2.5) Primary (Health) Standards
The final 2006 revised PM2.5 NAAQS, were not as stringent as the levels
recommended by the independent CASAC and those recommended by EPA
professional staff, as noted above. EPA staff and CASAC recommendations for
PM2.5 included a range of levels more stringent than those proposed in January and
finalized in September of 2006. In particular, the majority of the CASAC panel “did
not endorse the option of keeping the annual standard at its present value.”
According to the CASAC:
Of the options presented by EPA staff for lowering the level of the PM standard,
based on the above considerations and the predicted reductions in health impacts
derived from the risk analyses, most Panel members favored the option of setting3
a 24-hour PM2.5 NAAQS at concentrations in the range of 35 to 30 µg/m with
the 98th percentile form, in concert with an annual NAAQS in the range of 14337
to 13 µg/m.


36 Letter of Dr. Rogene Henderson, Chair, Clean Air Scientific Advisory Committee, to the
Hon. Stephen Johnson, Administrator, U.S. EPA, March 21, 2006, EPA-CASAC-
LTR-06-002, available at [http://yosemite.epa.gov/sab/sabproduct.nsf/CD706C976DAC

62B3852571390081CC21/$File/casac-ltr-06-002.pdf]; and letter of Dr. Rogene Henderson,


Chair of the Clean Air Scientific Advisory Committee, et al. to Hon. Stephen L. Johnson,
EPA Administrator, September 29, 2006, EPA-CASAC-LTR-06-003, available at
[http://yosemite.epa.gov/sab/sabproduct.nsf/1C69E987731CB775852571FC00499A10/
$File/casac-ltr-06-003.pdf].
37 CASAC PM Review Panel report, p. 7, June 2005 [http://www.epa.gov/ttn/naaqs/
standards/pm/s_pm_index.html ].

Table 5 below compares the CASAC and EPA staff recommendations for PM2.5
primary standards, the 1997 standards, and 2006 standards as proposed and
promulgated.
Table 5. PM2.5 Primary (Health) NAAQS: Final (2006), Proposed
and Alternatives, and as Promulgated in 1997
PM2.5 NAAQS Options24-hour Primary (98th percentile)Annual Primary (arithmetic mean)

1997 NAAQS65 µg/m315 µg/m3


EPA staff paper (December 2005)mid to lower range of35-25 µg/m315 µg/m3
or
mid to lower range of314-12 µg/m3
40-30 µg/m
CASAC (December 2005)35-30 µg/m314-13 µg/m3
EPA Proposed Rule (January 2006)35 µg/m315 µg/m3
EPA Final Rule (October 2006)35 µg/m315 µg/m3
Source: Prepared by the Congressional Research Service (CRS), with information from the EPAs
final 2006 particulates NAAQS (71 Federal Register 61143-61233, Oct. 17, 2006), the EPAs
proposed particulates NAAQS (71 Federal Register 2620, Dec. 20, 2005), and related technical38
documents, available at [http://www.epa.gov/air/particles/actions.html].
In response to the discrepancies between the proposal and the CASAC
recommendations, EPA Administrator Stephen Johnson indicated that his decision
required consideration of a number of factors and “judgment based upon an
interpretation of the evidence.” The Administrator relied on the evidence of long-39
term exposure studies as the principal basis for retaining the annual PM2.5 standard.
CASAC strongly disagreed with the Administrator’s decision regarding the PM2.5
annual standard and took the unprecedented step of urging reconsideration of the
proposal.40


38 EPA’s final PM staff paper and the CASAC review of the EPA staff paper (see references
earlier in this report).
39 For the EPA Administrator’s rationale for proposing to retain the current level for the
annual PM2.5 standard and recognition of the CASAC’s recommendation not endorsing this
approach, see 71 Federal Register 2650-2653, January 17, 2006.
40 Letter of Dr. Rogene Henderson, Chair, Clean Air Scientific Advisory Committee, to the
Hon. Stephen Johnson, Administrator, U.S. EPA, March 21, 2006, EPA-CASAC-LTR-
06-002, available at [http://yosemite.epa.gov/sab/sabproduct.nsf/CD706C976DAC62B
3852571390081CC21/$File/casac-ltr-06-002.pdf]; or from the federal docket for the
proposed rule Docket ID No. EPA-HQ-OAR-2001-0017, on the Federal Docket website
[ h t t p : / / www.r e gu l a t i ons .gov] .

Many public comments received on the EPA’s proposed revisions to the PM2.5
standards, most frequently from environmental and public health organizations,
medical doctors and researchers, and the association representing state air quality
regulators,41 argued for standards as stringent or more stringent than those
recommended by CASAC. In contrast, another group of commenters, generally
representing industry associations and businesses, opposed revising the 1997 PM2.5
standards, in some cases highlighting different aspects of the same research cited by
the CASAC and others supporting tighter standards.42 Some who opposed more
stringent particulates NAAQS called attention to more recent studies of health effects
attributable to particulates that demonstrate risk estimates are lower and less
statistically significant than they were in 1997, when the last standard was set.43
In Section II of the preamble of the final October 2006 revisions, “Rationale for
Final Decisions on Primary PM2.5 Standards,” the EPA discussed its final decision
with respect to the CASAC recommendations regarding the PM2.5 annual standard.
The Administrator differed with the CASAC with regard to the level of uncertainty
associated with the agency’s quantitative risk assessment and whether the results
appropriately served as a primary basis for a decision on the level of the annual PM2.5
standard. The Administrator further stressed the emphasis placed on the long-term
means of the levels associated with mortality effects in the two key long-term
studies44 in determining the level of the annual standard. CASAC considered the
evidence from specific short-term exposure studies as part of the basis for its
recommendation for a lower annual standard level. As noted above, the CASAC
expressed its objections to the EPA’s final 2006 particulates NAAQS in its
September 29, 2006, letter to Administrator Johnson.45
With regard to PM2.5, the letter stated: “CASAC is concerned that the EPA did
not accept our finding that the annual PM2.5 standard was not protective of human
health and did not follow our recommendation for a change in that standard.”46 The
letter noted that “there is clear and convincing scientific evidence that significant
adverse human-health effects occur in response to short-term and chronic particulate
matter exposures at and below 15 µg/m3,” and noted that 20 of the 22 Particulate
Matter Review Panel members, including all seven members of the statutory


41 CRS communication with Mr. William Becker, Executive Director, State and Territorial
Air Pollution Program Administrators/Association of Local Air Pollution Control Officials
(STAPPA/ALAPCO), January 5, 2006.
42 For EPA’s discussion and response to several of these comments, see 71 Federal Register

61143-61233, October 17, 2006, Part II Rationale for Final Decisions on Primary PM2.5


Standards, Sections B and F, on EPA’s website at [http://epa.gov/pm/actions.html].
43 Communication with Mr. Frank Maisano, Media Contact for the Electric Reliability
Coordinating Council, January 17, 2006.
44 71 Federal Register at 2651, January 17, 2006.
45 Letter of Dr. Rogene Henderson, Chair of the Clean Air Scientific Advisory Committee,
et al. to Hon. Stephen L. Johnson, EPA Administrator, September 29, 2006, available at
[ h t t p : / / yosemite.epa.gov/sab /sabproduct.nsf/1C69E987731CB775852571FC00499A10/$
File/casac-ltr-06-003.pdf].
46 Ibid.

committee were in “complete agreement” regarding the recommended reduction. “It
is the CASAC’s consensus scientific opinion that the decision to retain without
change the annual PM2.5 standard does not provide an adequate margin of safety ...
requisite to protect the public health’ (as required by the Clean Air Act)....”47
Potential Health Benefits of a More Stringent PM2.5 Standard. In its
RIA, the EPA estimated the nationwide monetized human health and welfare benefits
of attaining two suites of PM2.5 NAAQS: (1) the revised PM2.5 NAAQS, which33
include the 35 µg/m daily (24-hour) standard and the unchanged 15 µg/m annual
standard, and (2) an alternative standard similar to the least stringent of the CASAC3
recommendations that includes a tighter annual standard of 14 µg/m and the same
35 µg/m3 daily (24-hour) standard. As discussed previously, the EPA presented a
variety of benefits estimates based on several epidemiological studies, the American
Cancer Society (ACS) Study48 used in previous RIAs, the Harvard Six-Cities Study,4950
and an expert elicitation study conducted by the EPA in 2006.
The EPA estimated that attainment of the more stringent alternative PM2.5
NAAQS would result in $26 billion to $30 billion of total annual benefits in 2020,
based on the ACS mortality function. This compares to a range of $15 billion to $17
billion estimated for compliance with the 2006 PM2.5 NAAQS (see Table 2 and
discussion earlier in this report). EPA’s estimate of annual benefits derived using the
expert elicitation ranged from $15 billion to $140 billion for the more stringent
alternative, compared to the agency’s estimates of $8 billion to $76 billion for
compliance with the 2006 standard. EPA also estimated the monetary benefits
(“willingness to pay”) associated with improvements in visibility in selected Class
I national parks and wilderness areas would be $1.2 billion in 2020 with attainment
of the more stringent alternative PM2.5 standard analyzed, compared to $530 million
with attainment of the revised PM2.5 NAAQS.51 EPA estimated the total annual cost
associated with attainment of the alternative PM2.5 NAAQS analyzed would be $7.9
billion in 2020, compared to $5.4 billion.
For purposes of illustration, Table 6 below provides a comparison of EPA’s
predicted reductions annually for the 2006 PM2.5 NAAQS (15/35 µg/m3) with a more


47 Ibid.
48 Pope, C. Arden, III, et al. “Particulate Air Pollution as a Predictor of Mortality in a
Prospective Study of U.S. Adults.” American Journal of Respiratory and Critical Care
Medicine 151 (1995): 669-674.
49 Dockery, Douglas W., et al. “An Association Between Air Pollution and Mortality in Six
U.S. Cities.” New England Journal of Medicine 329 (1993): 1753-1759. See also the Health
Effects Institute, “Statement: Synopsis of the Particle Epidemiology Reanalysis Project.”
Reanalysis of the Harvard Six Cities Study and the American Cancer Society Study of
Particulate Air Pollution and Mortality, July 2000 (includes November 1, 2001 errata
sheet), p. I. ([http://pubs.healtheffects.org/getfile.php?u=271]).
50 See Chapter 5 of the EPA’s October 6, 2006, RIA for more detail [http://www.epa.gov/
ttn/ecas/ria.html ].
51 See Appendix in I Visibility Benefits Methodology of the EPA’s October 6, 2006, RIA
[http://www.epa.go v/ttn/ecas/ria.html ].

stringent alternative analyzed (14/35 µg/m3), based on data from the ACS and
Harvard Six-City studies, and epidemiology studies. As discussed previously, a key
component of the EPA’s monetized benefits estimates are the agency’s predicted
reductions in the incidence of premature deaths and a range of adverse health effects
annually in 2020 associated with compliance of the 2006 PM2.5 NAAQS. For
example, for the more stringent attainment strategy analyzed (14/35 µg/m3), the EPA
estimated 2,200 to 24,000 fewer premature deaths based on the expert elicitation.
Table 6. EPA’s Predicted Reductions in Adverse Health Effects
Annually in 2020 Associated with Meeting the 2006 PM2.5 NAAQS
and a More Stringent Alternative
Predicted Reductionsa
(estimated mean)
More Stringent
PM2.5 NAAQS 3Alternative 3
Adverse Health Effect(15/35 µg/m)(14/35 µg/m)
Premature deaths in individuals with preexisting2,500 to 5,700b4,000 to 9,000b
cardiovascular and respiratory disease
Cases of chronic bronchitis (age >25)2,6004,600
Cases of acute bronchitis (age 8-12)7,30013,000
Nonfatal heart attacks (age >71)5,0008,700
Hospital admissions for cardiovascular or1,6303,080
respiratory symptoms (age >17)
Emergency room visits for asthma (age <19)1,2003,200
Cases of aggravated asthma (asthmatics age 6-18)51,00079,000
Cases of upper and lower respiratory symptoms97,000153,000
(asthmatics age 6-18)
Days when individuals miss work (age 18-75)350,000550,000
Days when individuals must restrict their activities
because of symptoms related to particle pollution2,000,0003,300,000
(age 18-65)
Source: Prepared by the Congressional Research Service with data presented in Chapter 5 of EPAs
Agency Regulatory Impact Analysis of the 2006 National Ambient Air Quality Standards for Fine
Particle Pollution (PM2.5) Oct. 6, 2006, and available on the EPAs website at [http://www.epa.gov/
ttn/ecas/ria.html]. Estimates are rounded by EPA to two significant digits.
a. For consistency with the emissions and benefits modeling, the EPA used national population
estimates based on the U.S. Census Bureau projections. U.S. Bureau of Census. 2000.
Population Projections of the United States by Age, Sex, Race, Hispanic Origin and Nativity:
1999 to 2100. Population Projections Program, Population Division, U.S. Census Bureau,
Available at [http://www.census.gov/population/projections/nation/summary/np-t.txt].
b. The range of reductions in premature deaths estimates reflect the mean estimates derived from the
American Cancer Society study and the Harvard Six-City Study, respectively.



The estimates EPA derived from an expert elicitation approach were only for
mortality. The results were variable from expert to expert, ranging from a mean of
2,200 to 24,000 avoided premature deaths annually in 2020 resulting from attainment
of the more stringent alternative standard (14/35 µg/m3) incremental to the EPA’s
baseline strategy for the 1997 NAAQS (15/65 µg/m3). For attainment of the 2006
standards (15/35 µg/m3), EPA estimated 1,200 to 13,000 fewer premature deaths
based on the expert elicitation.
Coarse Particulate (PM10) Primary Standards
Particle Size Indicator. The EPA and most of the CASAC panel members
concluded that there was a lack of evidence (often a lack of studies) on long-term
adverse health effects of specific PM10 measurements to support the annual standard,
and that there was a specific need to address particles ranging in size from 2.5 to 10
microns.52 EPA’s January 17, 2006, proposal would have replaced the existing
particle size indicator of 10 micrometers (PM10) with an indicator range of 10 to 2.5
micrometers (PM10-2.5), referred to as inhalable (or thoracic) coarse particles, and3
setting a PM10-2.5 daily standard of 70 µg/mrather than the current PM10 daily
standard of 150 µg/m3. At the time of its proposal, the EPA concluded that the
scientific evidence supported the standard based on short-term exposure to certain
coarse particles, particularly in urban and industrial areas.
In the final 2006 particulates NAAQS, the EPA decided to maintain the PM10
indicator, citing the limited body of evidence on health effects associated with
thoracic coarse particles from studies that use PM10-2.5 measurements. The agency
also determined that the only studies of clear quantitative relevance to health effects
most likely associated with thoracic coarse particles used PM10 measurements. The

2006 particulates NAAQS retained the PM10 indicator and the daily (24-hour)


standard of 150 µg/m3.
In its September 29, 2006, letter, the CASAC said it was “completely surprised”
at the decision to revert to the use of PM10 as the indicator for coarse particles, noting
that the option of retaining the existing daily PM10 standard was not discussed during
the advisory process and that CASAC views this decision as “highly-problematic
since PM10 includes both fine and coarse particulate matter.” The CASAC did agree
that having a standard for PM10 was better than no standard.
The EPA indicated that it is promulgating a new federal reference method
(FRM) for measurement of mass concentrations of PM10-2.5 in the atmosphere as the
standard of reference for measurements of PM10-2.5 concentrations in ambient air. The
EPA anticipates that the new FRM should provide a basis for gathering scientific


52 Clean Air Scientific Advisory Committee (CASAC) Review of the EPA Staff
Recommendations Concerning a Potential Thoracic Coarse PM Standard in the Review of
the National Ambient Air Quality Standards for Particulate Matter: Policy Assessment of
Scientific and Technical Information (Final PM OAQPS Staff Paper, EPA-452/R-05-005,
June 2005), September 15, 2005, EPA-SAB-CASAC-05-007, available on the EPA CASAC
website at [http://yosemite.epa.gov/sab/sabproduct.nsf/WebReportsbyYearCASAC].

data to support future reviews of the particulates NAAQS.53 According to the EPA,
these monitors will employ the latest in speciation technology to advance the science,
enabling future regulation to provide more targeted protection.
The EPA’s January 17, 2006, proposal to change the indicator of the standard
for coarse particles was in response to a 1999 U.S. Court of Appeals for the DC
Circuit decision54 directing the EPA to ensure that the standard did not duplicate the
regulation of fine particles. The agency contends that it addressed the concerns
raised by the court regarding PM10 as an indicator for inhalable coarse particulate
matter in its rationale in the final 2006 particulates NAAQS, announced September

21, 2006.55


Rural PM10 Sources. In addition to the changes to the coarse particulates
indicator, the EPA had proposed narrowing the focus of the PM10-2.5 standard on
“urban and industrial” sources. Particles typical to rural areas including “windblown
dust and soils and PM generated by agricultural and mining sources” would not
have been subject to this standard. Additionally, the EPA proposed revoking the
current 24-hour PM10 standards, except in areas that have 1) violating monitors, and
2) a population of 100,000 or more. The emphasis on urban and industrial areas in
the January 2006 proposal was based on the findings reported in the Criteria
Document, the PM staff paper, and the CASAC conclusion that “the evidence for the
toxicity of PM10-2.5 comes from studies conducted primarily in urban areas and is
related, in large part, to the re-entrainment of urban and suburban road dusts, as well
as primary combustion products.”56
The EPA’s proposal to exclude any ambient mix of PM10-2.5 that is dominated
by rural windblown dust and soils and particulates generated by agricultural and
mining sources, and how the EPA would distinguish the sources during its
implementation, raised a number of questions and resulted in numerous comments.
In response to the proposal, in its March 21, 2006, letter to the EPA Administrator,
the CASAC stated that while it had recognized the scarcity of information on the
toxicity of rural dust, it “neither foresaw nor endorsed a standard that specifically
exempts all agricultural and mining sources, and offers no protection against episodes
of urban-industrial PM10-2.5 in areas of populations less than 100,000.” The


53 71 Federal Register 61143-61233, October 17, 2006, Section VI. Reference Methods for
the Determination of Particulate Matter as PM10-2.5 and PM2.5 [http://epa.gov/pm/
actions.html].
54 The EPA’s standard for PM10, as modified by the 1997 changes to the particulates
NAAQS, was challenged shortly after promulgation. Concluding that PM10 was a “poorly
matched indicator” for thoracic coarse particles because it included the smaller PM2.5
category as well as the larger particles, the D.C. Circuit remanded the standard to the EPA
(American Trucking Associations v. EPA, 175 F.3d 1027, 1054-55 (D.C. Cir. 1999)).
55 71 Federal Register 61143-61233, October 17, 2006, Section III.C.3. Decision Not to
Revise PM10 Indicator, available at [http://epa.gov/pm/actions.html].
56 CASAC review. CASAC reviews, the PM criteria document, staff paper, and related
information, are available at [http://www.epa.gov/ttn/naaqs/standards/pm/s_pm_index.html].

committee strongly recommended “expansion of our knowledge of the toxicity of
PM10-2.5 dusts rather than exempting specific industries (e.g., mining, agriculture).”57
Several Members of the House Committee on Agriculture submitted a letter to
EPA Administrator Stephen Johnson in July 2006 conveying support for the agency
to maintain its provision to exclude agriculture and mining dust and similar sources
of coarse particulates in the particulates NAAQS, as had been proposed.58 The EPA
indicated that with the exception of representatives of those sources that would have
been excluded under the proposal (e.g., agriculture and mining), most commenters
opposed the exclusion. Those opposed included environmental and public health
groups, state and local agencies, and industries not excluded from the proposed
indicator (e.g., transportation and construction).
The EPA did not exclude any areas or types of particles in the final 2006
particulates NAAQS revisions, based on further consideration of the data and in
response to comments. In its rationale for the final PM10 standard, the EPA continued
to acknowledge that there is far more evidence concerning health effects associated
with thoracic coarse particles in urban areas than in non-urban areas. However, the
EPA also stated that “the existing evidence is inconclusive with regard to whether or
not community-level exposures to thoracic coarse particles are associated with
adverse health effects in non-urban areas.”59 The EPA indicated that it would be
expanding its research and monitoring programs to collect additional evidence on the
differences between coarse particles typically found in urban areas and those typically
found in rural areas. The EPA announced the release of a final rule amending its
national air quality monitoring requirements on September 27, 2006.60
In contrast to objections regarding other aspects of EPA’s final 2006 particulates
NAAQS revisions, the CASAC agreed with the EPA decision against including
exemptions in its September 29, 2006, letter to the EPA Administrator. However,
a number of those representing agriculture interests, including some Members of
Congress,61 remained concerned that EPA’s decision not to include the exclusions in


57 Letter of Dr. Rogene Henderson, Chair, Clean Air Scientific Advisory Committee, to the
Hon. Stephen Johnson, Administrator, U.S. EPA, March 21, 2006, EPA-CASAC-LTR
-06-002, available at [http://yosemite.epa.gov/sab/sabproduct.nsf/CD706C976DAC62B
3852571390081CC21/$File/casac-ltr-06-002.pdf], or from the federal docket for the
proposed rule Docket ID No. EPA-HQ-OAR-2001-0017, on the Federal Docket website
[ h t t p : / / www.r e gu l a t i ons .gov] .
58 Letter to EPA Administrator Stephen L. Johnson, from the Chairman, the Ranking
Member, and other Members of the House Committee on Agriculture, July 27, 2006.
59 71 Federal Register 61143-61233, October 17, 2006, Section III.C.3. Decision Not to
Revise PM10 Indicator, available at [http://epa.gov/pm/actions.html].
60 71 Federal Register 61236-61328, October 17, 2006, at [http://epa.gov/pm/actions.html].
61 Some Members of the House Committee on Agriculture expressed their concerns with the
EPA’s final actions with regard to the exemptions at a September 28, 2006, hearing
regarding the EPA’s pesticide programs. House Committee on Agriculture, Subcommittee
on Conservation, Credit, Rural Development, and Research, Review of the Environmental
(continued...)

the final 2006 particulates NAAQS will result in unnecessary burdens on the
agricultural community.
Since the PM10 standard was not strengthened (in fact the 2006 PM NAAQS
eliminated the annual maximum concentration (50 µg/m3) standard for PM10) no new
areas, including rural or non urban areas, will be designated as nonattainment for
PM10. To the contrary, a few counties previously designated nonattainment have
been determined by EPA to be in attainment since the 2006 revisions to the
particulates NAAQS (see Figure 1 in Appendix depicting PM10 nonattainment
areas). Additionally, states’ nonattainment recommendations for the 2006 PM2.5
NAAQS and EPA’s August 2008 proposed modifications to these recommendations,
do not include new rural or non-urban areas.
Secondary PM2.5 and PM10 Standards
The EPA proposal, and the final 2006 particulates NAAQS, set the secondary
standard for PM10 and for PM2.5 at the same level as their primary standard. The PM
staff paper and the CASAC both recommended secondary standards at levels
different from the primary in order to be more protective of visibility, and the
CASAC reiterated the recommendations in its March 21, 2006, and September 29,
2006, letters to the EPA Administrator. For PM2.5, the EPA PM staff paper and most
of the CASAC panel recommended consideration of a sub-daily standard with a level
in the range of 20 to 30 µg/m3 for a four- to eight-hour midday time period, with andth3

92 to 98 percentile form, as opposed to the primary daily standard at 35 µg/m,


based on the current three-year average of the 98th percentile of 24-hour PM2.5
concentrations. Although the CASAC agreed with setting a secondary standard at
the same level as the primary standard based on the coarse particulates indicator
PM10-2.5, the committee recommended that the standard not be limited to urban areas,
as the EPA had proposed.
Exclusion of More Recent Research
A number of stakeholders commented that EPA should have considered certain
studies that were published too recently to have been included in the 2004 criteria
document that, they argued, increased the uncertainty about possible health risks
associated with exposure to particulates. Others contended that there are new studies
(some of them the same) in support of their arguments for a lower (more stringent)
level to protect health. Some who opposed more stringent standards, commented that
the agency should have delayed its decision regarding the PM NAAQS to take into
consideration several of these studies.
At the time of the proposal the EPA declared its intention to review and evaluate
significant new studies developed since 2002, and those published since the close of


61 (...continued)
Protection Agency’s Pesticide Program, September 28, 2006.

the criteria document, during the comment period.62 With the release of its final 2006
particulates NAAQS, the EPA acknowledged that these studies provided expansion
of the science and some insights regarding particulates exposure and related health
effects, but determined that the new data “do not materially change any of the broad
scientific conclusions regarding the health effects of PM exposure made in the 2004
PM Air Quality Criteria Document.”63
Synopses of Stakeholder Reaction to
the 2006 Particulates NAAQS
Based on the EPA’s references to the comments in the preamble to the final
2006 particulates NAAQS revisions published October 17, 2006; a review of several
comments in the Federal Docket for the January 17, 2006, proposal; and several
media articles and available press releases, views of proponents and critics of stricter
standards are summarized below.
Proponents of more stringent particulates standards generally asserted that
!the standards should be at least as stringent as the more stringent
combined daily and annual levels recommended in the EPA PM staff
paper and those recommended by the CASAC, based on its review
of the criteria and the EPA staff analysis;
!scientific evidence of adverse health effects is more compelling than
when the standards were revised in 1997;
!exclusion of rural sources from the coarse particle (PM10) standard
would not be sufficiently protective of human health and would be
difficult to distinguish and implement;
!more stringent standards ensure continued progress toward
protection of public health with an adequate margin of safety as
required by the CAA, in addition to avoidance of other adverse
health effects; and
!welfare effects, such as visibility, crop yield, and forest health, will
be enhanced.
Critics of more stringent particulates standards contended that
!more stringent standards (and in some cases even the 1997
standards) are not justified by the scientific evidence; the proposal
did not take into account hundreds of studies completed since the

2002 cut-off;


62 71 Federal Register 2625, January 17, 2006 ([http://epa.gov/pm/actions.html]).
63 71 Federal Register 61143-61233, October 17, 2006 ([http://epa.gov/pm/actions.html]).

!requiring the same level of stringency for all fine particles without
distinguishing sources is unfounded;
!those representing “rural” sources contend exemption of rural
particles is warranted by the lack of evidence regarding adverse
effects associated with emission sources in these areas, and that not
excluding these areas and sources creates an unnecessary burden;
and
!the benefits (and costs) associated with implementation of the 1997
PM2.5 NAAQS, as well as compliance with recent EPA air quality
regulations, have not yet been realized.
In December 2006, thirteen states (New York, California, Connecticut,
Delaware, Illinois, Maine, New Hampshire, New Jersey, New Mexico, Oregon,
Pennsylvania, Rhode Island, Vermont), the District of Columbia, and the South Coast
Air Quality Management District petitioned the U.S. Court of Appeals for the D.C.
Circuit to review the 2006 particulates NAAQS.64 In addition, several groups
representing various industry and agriculture interests (including coal, iron, steel, and
corn refiners; oilseed processors; farmers; and cattle and pork producers), as well as
environmental and public health organizations also filed petitions to the D.C. Circuit
challenging the 2006 NAAQS. The court consolidated the cases and ordered
submission of briefs from petitioners, EPA, and supporters for October 2007 through
February 2008, with final briefs due by March 2008.65 Briefs from petitioners, EPA,
and supporters were filed with the court by March 7, 2008, and oral argument
occurred September 15, 2008.66
Further delays in implementing 1997 PM2.5 NAAQS will likely have direct
implications for implementing the 2006 PM2.5 NAAQS. A number of events, most
notably the D.C. Circuit Court’s July 2008 decision to vacate EPA’s 2005 Clean Air
Interstate Rule (CAIR), are directly affecting the timely implementation of the 1997
PM2.5 NAAQS. The D.C. Circuit’s decision regarding the CAIR could result in
significant delays, and has garnered attention in Congress.67


64 Pursuant to Rule 15 of the Federal Rules of Appellate Procedure and §307(b) of the Clean
Air Act, 42 U.S.C. §7607(b).
65 American Farm Bureau Federation v. U.S. EPA, No. 06-1410 (D.C. Cir. 2006).
66 American Farm Bureau Federation v. U.S. EPA, No. 06-1410 (D.C. Cir. , oral argument
September 15, 2008).
67 For a more detailed discussion of the court’s decision and its implications, see CRS
Report RL34589, Clean Air After the CAIR Decision: Back to Square One?, by James E.
McCarthy, Larry Parker and Robert Meltz; also see related discussion in CRS Report
RL32431, Particulate Matter (PM2.5): Implementation of the 1997 National Ambient Air
Quality Standards (NAAQS), by Robert Esworthy.

Conclusions
The EPA’s October 17, 2006, promulgation of the final modifications to the
existing particulates NAAQS following completion of its statutorily required review
sparked interest and conflicting concerns among a diverse array of stakeholders, and
in Congress.
As a result of EPA tightening the fine particulates (PM2.5) NAAQS, more areas
will be classified as nonattainment and needing to implement new controls on
particulate matter in order to comply. States and local governments will be required
to develop and implement new or modified plans for addressing emissions in those
areas that do not meet the 2006 standards. A stricter standard means increased costs
for the transportation and industrial sectors most likely to be affected by particulate
matter controls, including utilities, refineries, and the trucking industry. In terms of
public health, a stricter standard is estimated to result in fewer adverse health effects
for the general population and particularly sensitive populations, such as children,
asthmatics, and the elderly.
Because of health and cost implications, NAAQS decisions have been the
source of significant concern to some in Congress. The evolution and development
of the particulates NAAQS, in particular, have been the subject of extensive
oversight. As a result, the D.C. Circuit’s decision regarding challenges to the 2006
PM NAAQS may prompt renewed interest in the issues discussed throughout this
report.



Appendix. PM10 NAAQS
Geographic Nonattainment Areas
Since 1990, EPA designated 87 areas as nonattainment with the PM10
NAAQS.68 As of November 2008, 40 of the original 87 PM10 areas have been
redesignated to attainment. Of the remaining 47 nonattainment areas (46 counties
with a population of 28.5 million), 26 areas are currently not meeting the PM10
standard or have insufficient data to determine attainment based on 2005-2007 data.
The remaining counties have submitted the required SIPs for PM10 but have not yet
been formally redesignated to attainment.69 Figure 1 shows the status of
nonattainment of the PM10 NAAQS. As depicted on the map, the majority of the U.S.
is in attainment of the PM10 NAAQS (including Hawaii which is not shown on the
map as provided by EPA).


68 See EPA’s PM10 designations at [http://www.epa.gov/air/oaqps/greenbk/pindex.html].
69 Information provided directly to CRS by the EPA Office of Air Quality Planning and
Standards (OAQPS).

CRS-25
Figure 1. Status of Current PM10 Nonattainment Areas,
Based on 2004-2006 Air Quality


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Source: Updated map provided directly to CRS by the EPA Office of Air Quality Planning and Standards (OAQPS), March 19, 2008. There are no PM10
nonattainment areas in Hawaii which was not included on the EPA map.