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The Environmental Protection Agency (EPA) published its final revisions to the National
Ambient Air Quality Standards (NAAQS) for particulate matter (particulates, or PM) on October
17, 2006. EPA’s actions leading up to and following promulgation of the 2006 standard has been
the subject of considerable Congressional oversight. EPA’s implementation of the standard,
beginning with the designation of those geographical areas not in compliance, will likewise be an
area of concern and debate among many Members of Congress, states, and other stakeholders for
some time.
Promulgation of NAAQS sets in motion a process under which the states and the EPA identify
areas that exceed the standard (“nonattainment areas”) using multi-year air quality monitoring
data and other criteria, requiring states to take steps to reduce pollutant concentrations in order to
achieve it. As an initial phase of this process, in its August 2008 letters responding to
recommendations received from States, EPA proposed area boundaries (typically defined by
counties or portions of counties) for consideration as nonattainment for the 2006 NAAQS. EPA
expects to finalize these nonattainment designations by the end of 2008, with an effective date of
April 2009. Following formal designation, the states have three years to submit State
Implementation Plans (SIPs), which identify specific regulations and emission control
requirements that would bring an area into compliance.
The 2006 NAAQS strengthened the pre-existing (1997) standard for “fine” particulate matter 2.5
micrometers or less in diameter (PM2.5) by lowering the allowable daily concentration of PM2.5 in
the air. The daily standard averaged over 24-hour periods is reduced from 65 micrograms per
cubic meter (µg/m3) to 35 µg/m3. However, the annual PM2.5 standard, which addresses human
health effects from chronic exposures to the pollutants, is unchanged from the 1997 standard of
15 µg/m3. The 2006 NAAQS did not substantially modify the daily standard for slightly larger,
but still inhalable, particles less than or equal to 10 micrometers (PM10), retaining the 24-hour
standard, but revoked the annual standard for PM10.
The EPA is not requiring new nonattainment designations for PM10. The 2006 tightening of the
PM2.5 standards is expected to affect areas currently designated nonattainment for the 1997 PM2.5
NAAQS; a number of areas would be designated nonattainment for the PM2.5 NAAQS for the
first time. In its August 2008 letter to states, EPA identified 215 counties and portions of counties
in 25 states for designation as nonattainment only for the revised 2006 24-hour PM2.5 standard.
EPA’s final designations for nonattainment of the 1997 PM2.5 NAAQS included all or part of 205
counties in 20 states and the District of Columbia, the majority of which did not meet the annual
PM2.5 standard. Overall, the total number of counties or portions of counties throughout the
United States that will be designated “nonattainment,” will increase as a result of the 2006
NAAQS.

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Introduction ..................................................................................................................................... 1
EPA’s 2006 Changes to the Particulates NAAQS............................................................................ 2
Designation of Geographical Nonattainment Areas ........................................................................ 3
NAAQS Designation Process.................................................................................................... 3
PM2.5 NAAQS Designations ..................................................................................................... 4
Comparing the 2006 and 1997 PM2.5 NAAQS Designations.................................................... 7
Demonstrating Attainment with the 2006 PM2.5 NAAQS ............................................................ 10
State Implementation Plans (SIPs) .......................................................................................... 10
EPA NAAQS Implementation Rules .................................................................................11
National Regulations..........................................................................................................11
New Source Review.......................................................................................................... 12
Transportation Conformity ............................................................................................... 12
Conclusions ................................................................................................................................... 13

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Figure 1. Counties in Nonattainment for the 2006 PM2.5 NAAQS—EPA’s August 2008
Response to States’ Recommendations ........................................................................................ 6
Figure 2. Currently Designated Nonattainment Areas 1997 PM2.5 Standards ................................. 7
Figure 3. Counties Projected to be Designated Nonattainment for the 2006 PM2.5 NAAQS.......... 9

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Table 1. Counties Designated Nonattainment for the 1997 PM2.5 NAAQS and Projected
to be Nonattainment for the 2006 PM2.5 NAAQS ........................................................................ 8
Table A-1. Schedule for Implementation of the 1997 and the 2006 PM2.5 NAAQS ..................... 15
Table B-1. Recommended Nonattainment Areas for the 2006 PM2.5 NAAQS and Final
Nonattainment Designations for the 1997 PM2.5 NAAQS ......................................................... 16

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Appendix A. Comparative Timeline for Implementing the 1997 and 2006 PM2.5 NAAQS.......... 15
Appendix B. Comparison of Recommended Nonattainment Areas for the 2006 PM2.5
NAAQS and the Final Nonattainment Designations for the 1997 PM2.5 NAAQS .................... 16

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Author Contact Information .......................................................................................................... 27

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Under Sections 108-109 of the Clean Air Act (CAA), Congress mandated that the Environmental
Protection Agency (EPA) set national ambient (outdoor) air quality standards (or NAAQS) for
pollutants whose emissions: (1) “may reasonably be anticipated to endanger public health or
welfare;” and (2) “the presence of which in the ambient air results from numerous or diverse
mobile or stationary sources.” The statute further requires that EPA review the latest scientific
studies and either reaffirm or modify previously established NAAQS every five years. The EPA
has identified and promulgated NAAQS 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,1 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 particulate matter (PM)
to provide protection against potential health effects associated with short- and long-term
exposure to particulates (including chronic respiratory disease and premature mortality).2 The
2006 particulates NAAQS primarily tightened the pre-existing (1997) standard for “fine”
particulate matter 2.5 micrometers or less in diameter (PM2.5).3 The standard for slightly larger,
but still inhalable, particles less than or equal to 10 micrometers (PM10) established in 19874 was
not similarly strengthened.
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. Promulgation of NAAQS sets in motion a process
under which the states and the EPA first identify geographic nonattainment areas, those areas
failing to meet the NAAQS based on monitoring and analysis of relevant air quality data. States
have three years from the date of EPA’s final designations to submit State Implementation Plans
(SIPs), which identify specific regulations and emission control requirements that will bring an
area into compliance. EPA expects to finalize the nonattainment designations for the 2006 PM
NAAQs by the end of 2008 with an effective date of April 2009.5
This report focuses primarily on the NAAQS implementation process for designating
geographical nonattainment areas with respect to the tightening of the PM2.5 standards under the
2006 particulates NAAQS, including comparisons with the final designations under the 1997
PM2.5 NAAQS. The EPA is not requiring new nonattainment designations for PM10. Also included
is a brief overview of states’ subsequent obligations for developing and submitting
implementation plans (SIPs) for attaining or maintaining compliance with the NAAQS.
Appendix A includes a table displaying a state and county breakdown of designated nonttainment

1 The NAAQS is for NO2; nitrogen gases that are ozone precursors are referred to as NOx.
2 Federal Register 61143-61233, October 17, 2006. See also EPA’s PM Regulatory Actions website at http://epa.gov/
pm/actions.html.
3 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.
4 Federal Register 24634-24715, July 1, 1987.
5 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.
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areas proposed by the states and by EPA for the 2006 PM2.5 NAAQS, as well as the final EPA
designations table for the 1997 PM2.5 NAAQS.
For background of the process used to establish the 2006 particulates NAAQS and analysis of
associated issues see CRS Report RL34762, The National Ambient Air Quality Standard for
Particulate Matter (PM): EPA’s 2006 Revisions and Associated Issues, by Robert Esworthy and
James E. McCarthy.
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The Clean Air Act provides for two types of NAAQS: primary standards, “the attainment and
maintenance of which in the judgment of the [EPA] Administrator ... are requisite to protect the
public health,” with “an adequate margin of safety”; and secondary standards, necessary to
protect public welfare, a broad term that includes damage to crops, vegetation, property, building
materials, etc.6
The primary NAAQS include a daily (24-hour) limit for both PM2.5 and PM10, and an annual
limit for PM2.5 (the previous annual limit for PM10 was revoked). 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 are 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. For PM2.5 and PM10,
the secondary (welfare) NAAQS are the same as the primary standards.
As modified and published in the October 17, 2006 Federal Register Notice, the primary PM2.5
and PM10 standards are as follows:
• PM2.5: strengthens the daily (24-hour) standard, which currently allows no more
than 65 micrograms per cubic meter (µg/m3) under the 1997 PM2.5 NAAQS, by
setting a new limit of 35 µg/m3, based on the three-year average of the 98th
percentile of 24-hour PM2.5 concentrations; retains the annual standard at 15
µg/m3.
• PM10: retains the daily (24-hour) standard at 150 µg/m3 set in 1987 but changes
from the 99th percentile to no more than one exceedance per year on average over
three years; eliminates the annual maximum concentration (50 µg/m3) standard
for PM10.7
• As will be shown in more detail in the following section, strengthening the daily
standard for PM2.5 will have implications for those counties and partial counties

6 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)).
7 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.
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designated nonattainment for the 1997 PM2.5 NAAQS. With only a few
exceptions, most of the designated nonattainment areas for the 1997 PM2.5
NAAQS were not meeting the annual standard, but were meeting the daily (24-
hour) standard. Since the PM10 standard was not strengthened, no new 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.8
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Designating geographical areas not achieving the established NAAQS based on monitoring and
analysis of relevant air quality data, is a critical step in NAAQS implementation. Section 107(d)
of the CAA (42 U.S.C. 7407) establishes the process for designating attainment and
nonattainment areas and setting their boundaries, but allows the EPA Administrator some
discretion in determining what the final boundaries of the areas will be. Areas are identified as
“nonattainment” when they violate or contribute to the violation of NAAQS.
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The NAAQS designation process is intended as a cooperative federal-state-tribal9 process in
which states and tribes provide initial designation recommendations to EPA for consideration. In
Section 107(d)(1)(A) (42 U.S.C. 7407), the statute states that the governor of each state shall
submit a list to EPA of all areas in the state, “designating as ... nonattainment, any area that does
not meet (or that contributes to ambient air quality in a nearby area that does not meet) an air
quality standard” (emphasis added). Areas are identified as “attainment/unclassified”10 when they
meet the standard or when the data are insufficient for determining compliance with the NAAQS.
Following state and tribal designation submissions, the EPA Administrator has discretion to make
modifications, including to the area boundaries. As required by statute (Section 107(d)1(B)(ii)),
the agency must notify the states and tribes regarding any modifications, allowing them sufficient
opportunity to demonstrate why a proposed modification is inappropriate, but the final
determination rests with EPA.
Measuring and analyzing air quality to determine where NAAQS are not being met is a key step
in determining an area’s designation. Attainment or nonattainment designations are made
primarily on the basis of three-years of federally referenced monitoring data.11 EPA began

8 See discussion, and map in Appendix A depicting PM10 nonattainment areas, in CRS Report RL34762, The National
Ambient Air Quality Standard for Particulate Matter (PM): EPA’s 2006 Revisions and Associated Issues, by Robert
Esworthy and James E. McCarthy.
9 Though not required to do so, tribes have been encouraged to submit recommendations. The area designation
requirements under the CAA (Section 107) are specific with respect to states, but not to tribes. The EPA follows the
same designation process for tribes per Sections 110(o) and 301(d) of the CAA and pursuant to the 1988 Tribal
Authority Rule, which specifies that tribes shall be treated as states in selected cases (40 CFR Part 49). For information
regarding tribes that have participated in the PM2.5 designation recommendation process, see http://www.epa.gov/
pmdesignations.
10 Section 107(d)(1)(A)(iii) of the CAA provides that any area that EPA cannot designate on the basis of available
information as meeting or not meeting the standards should be designated unclassifiable.
11 A federally referenced monitor is one that has been accepted for use by EPA for comparison of the NAAQS by
(continued...)
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developing methods for monitoring fine particles at the time the PM2.5 NAAQS were being
finalized in 1997, and operation of the network of monitors for PM2.5 was phased in from 1999
through 2000.
The network of monitors and their locations have been modified over time. Most recently, in a
separate action in conjunction with the October 2006 publication of the revised particulates
NAAQS, EPA amended its national air quality monitoring requirements, including those for
monitoring particle pollution.12 The amended monitoring requirements were intended to help
federal, state, and local air quality agencies by adopting improvements in monitoring technology.
EPA’s final designations for the 2006 particulates NAAQS are to be based on 2003-2007
monitoring data.
In addition to air emission and air quality data, EPA considers a number of other relevant
factors,13 and recommends that states apply these factors in their determinations in conjunction
with other technical guidance. Examples of these factors include population density and degree of
urbanization (including commercial development), growth rates, traffic and commuting patterns,
weather and transport patterns, and geography/topography. States and Tribes may submit
additional information on factors they believe are relevant for EPA to consider.
Nonattainment areas include those counties where pollutant concentrations exceed the standard as
well as those that contribute to exceedance of the standard in adjoining counties. Entire
metropolitan areas tend to be designated nonattainment, even if only one county in the area has
readings worse than the standard. In addition to identifying whether monitored violations are
occurring, States’ or Tribes’ boundary recommendations for an area are to also show that
violations are not occurring in those portions of the recommended area that have been excluded,
and that they do not contain emission sources that contribute to the observed violations.
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In December 2007, 20 states provided EPA with recommended nonattainment boundaries for the
2006 revised particulates NAAQS based on 2004 to 2006 monitoring data. The states identified
46 areas comprising 116 counties, including 31 partial counties (see Table A-1 for state by state
county/area nonattainment designations). The recommended designations are primarily based on
2004-2006 monitoring data, criteria and technical guidance from EPA and assistance from its
regional offices, and states’ own relevant information and criteria.
The CAA does not specifically require combining neighboring counties within the same
nonattainment area, but it does require the use of metropolitan statistical area boundaries in the
more severely polluted areas (Section 107(d)(4)(A)(iv)). However, unlike the 1997 PM2.5

(...continued)
meeting the design specifications and certain precision and bias (performance) specifications (40 CFR Part 58).
12 Revisions to Ambient Air Monitoring Regulations, final rule, 71 Federal Register 61235-61328, October 17, 2006.
http://www.epa.gov/air/particlepollution/actions.html.
13 See Chapter 5 of the EPA Technical Support Document for December 17, 2004 final designations for the 1997 PM2.5
NAAQS and April 2005 modifications, for explanations of these factors; available at http://www.epa.gov/
pmdesignations/1997standards/tech.htm.
14 For detailed PM2.5 state/county geographical designation recommendations by EPA and those from individual states
and tribes, for the 1997 and for the 2006 PM2.5 NAAQS, see http://www.epa.gov/pmdesignations.
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standards, Metropolitan Statistical Areas or Consolidated Metropolitan Statistical Areas15 did not
generally serve as the “presumptive boundary” for nonattainment areas under the 2006 PM2.5
standards. Rather than establish a presumption for the minimum size of an area, in its June 2007
guidance16 EPA instructed states and tribes to evaluate each area on a case-by-case basis. EPA
expected that nonattainment areas for the 2006 24-hour PM2.5 would include counties with
monitors violating the 24-hour standard and nearby counties that contribute to that violation. EPA
also recommended that states and tribes consider using common boundaries for areas to be
designated as nonattainment for both the annual and 24-hour PM2.5 standards. This information in
conjunction with air emission and air quality data, as well other relevant factors as recommended
in EPA’s guidance, such as population density, growth rates, traffic and commuting patterns,
weather and transport patterns, and geography/topography, were used by states in determining the
boundaries for the designated areas.
As required by statute, EPA responded to the states with its modifications to the area designation
recommendations for the 2006 PM2.5 NAAQS for the 24-hour standard in letters dated August 19,
2008. The EPA solicited the states’ comments and additional information for consideration in
determining the final designations.17 As it did in implementing the 1997 PM2.5 NAAQS and has
done with other NAAQS, EPA used its discretion to expand the size of nonattainment areas
(added more counties or portions of counties) or to combine areas that a state listed as separate
areas into a single larger unit, EPA also combined nonattainment counties across state lines into
the same nonattainment area, if the counties are part of the same metropolitan area.
The counties that EPA has identified as nonattainment for the 2006 PM2.5 NAAQS are indicated
in the map in Figure 1 on the next page. While the identified areas can seem small compared with
the approximately 3,000 counties in the United States, nonattainment counties tend to have larger
populations than those in attainment: for example, nearly 90 million people (about 30% of the
U.S. population) live in the 205 counties designated nonattainment for the current 1997 PM2.5
NAAQS. The map distinguishes those counties not previously designated nonattainment for the
PM2.5 NAAQS and those areas that are being designated for the 2006 PM2.5 24-hour standard, that
were previously designated nonattainment for the 1997 PM2.5 NAAQS.
The agency identified 57 areas in 26 states, comprising 215 counties (169 counties and portions
of 46 additional counties) for designation as nonattainment for the revised 2006 24-hour PM2.5
standard (see table in Appendix A for state by state county/area nonattainment designations). The
EPA’s designations do not identify counties violating the annual standard, as the level is
unchanged from the 1997 PM2.5 NAAQS. Areas include whole and partial counties and, as with
the designations for the 1997 PM2.5 and other criteria pollutant NAAQS standards, several areas
include counties from multiple states.

15 As defined by the Office of Management Budget. For more information on metropolitan areas, see
http://www.census.gov/population/www/estimates/aboutmetro.html.
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 For information regarding EPA’s August 19, 2008 designations, see http://www.epa.gov/pmdesignations/
2006standards/regs.htm#2.
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Figure 1. Counties in Nonattainment for the 2006 PM2.5 NAAQS—EPA’s August
2008 Response to States’ Recommendations
(violating the 24-hour standard (35 μg/m3) only)

Source: Prepared by the Congressional Research Service based on EPA’s Responses to State Nonattainment
Recommendations, August 19, 2008, with data compiled from EPA’s website for PM designations. Partial counties
are shown on the map as whole counties. http://www.epa.gov/pmdesignations/.
States (and tribal groups) had 120 days to respond to EPA’s recommendations, and the agency
also issued a notice18 for a 30-day public comment period. EPA expects to finalize these
nonattainment designations (based on 2005-2007 monitoring data19) by December 18, 2008, with
an effective date of April 2009. The date of final designations may be extended up to one year,
but no later than December 18, 2009, if the Administrator determines that the agency has
insufficient information to promulgate the designations.
In responding to EPA’s proposal for Nonattainment designations for the 1997 PM2.5 NAAQS, a
number of states challenged the agency and maintained support for their original
recommendations. The final EPA designations for the 1997 PM2.5 NAAQS reflected minor
modifications to its proposal; primarily, 19 counties were removed from the list of nonattainment
areas, and other counties were redefined by designating only specified locations (“partial”) within
the county as nonattainment. EPA also subsequently denied six petitions submitted to the agency
requesting reconsideration of the previous designations of one or more full or partial counties as
nonattainment for the 1997 PM2.5 NAAQS.20

18 73 Federal Register 51257, September 2, 2008.
19 Revisions to Ambient Air Monitoring Regulations, final rule, 71 Federal Register 61235-61328, October 17, 2006
http://www.epa.gov/air/particlepollution/actions.html.
20 The petitions were for counties in Georgia, Illinois, Michigan, Missouri, Ohio, and West Virginia; see
http://www.epa.gov/pmdesignations/1997standards/regs.htm.
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As of August 2008, EPA’s final designations for nonattainment of the 1997 PM2.5 NAAQS (those
areas with or contributing to air quality levels exceeding the annual and 24-hour standards)
included all or part of 205 counties in 20 states and the District of Columbia.21 As indicated in the
map in Figure 2 the designated nonattainment areas for the 1997 PM2.5 NAAQS are primarily
concentrated in the central, mid-Atlantic, and southeastern states east of the Mississippi River, as
well as in California. More than 2,900 counties in 30 states have been designated
attainment/unclassifiable for the 1997 PM2.5 NAAQS.
Figure 2. Currently Designated Nonattainment Areas 1997 PM2.5 Standards
(violating the annual (15 μg/m3) and/or 24-hour (65 μg/m3) standard)

Sources: U.S. EPA, PM Standards Revision - 2006 Graphs and Maps, Oct. 25, 2006 http://www.epa.gov/oar/
particlepollution/naaqsrev2006.html#maps. The map includes the 3-county nonattainment area in Pennsylvania
determined by EPA to be in attainment in August 2008; there are no PM2.5 nonattainment areas in Hawaii or
Alaska, which were not included on the EPA map.

21 See EPA’s PM2.5 Designations website at http://www.epa.gov/pmdesignations. See also CRS Report RL32431,
Particulate Matter (PM2.5): Implementation of the 1997 National Ambient Air Quality Standards (NAAQS), by Robert
Esworthy.
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Based on EPA’s recommendations for the 2006 PM2.5 NAAQS, a few counties would be
designated nonattainment for PM2.5 for the first time but the majority of the counties identified
overlap with EPA’s final nonattainment designations for the 1997 PM2.5 NAAQS. Most of the
1997 PM2.5 nonattainment areas were only exceeding the annual standard; only 12 counties were
exceeding both the 24-hour and the annual standards. Thus, tightening the 24-hour standard will
result in an increased number of areas being designated nonttainment based on exceedances of
both the 24-hour and the annual standard.
Table 1 below illustrates the comparative geographic distribution of counties projected to be in
nonattainment with the 2006 PM2.5 NAAQS (based on EPA’s August 2008 letters to states and
tribes), and those counties in EPA’s final area designations for the 1997 PM2.5 NAAQS. The map
in Figure 3 below, overlaps the final nonattainment designations for the annual and 24-hour
standard under the 1997 PM2.5 NAAQS, with the nonattainment areas for the 24-hour standard as
modified under the 2006 PM2.5 NAAQS, identified by EPA in its August 2008 letters to states.
Table 1. Counties Designated Nonat ainment for the 1997 PM2.5 NAAQS and
Projected to be Nonattainment for the 2006 PM2.5 NAAQS
PM2.5 NAAQS (annual/24-hour μg/m3)

1997 Standard
2006 Standard
15/65 μg/m3
15/35 μg/m3
National
West East National
West East

Number of counties (including partial counties and D.C.)
Total exceeding the standard
205
13
192
265
45
220
Exceeding the 24-hour and annual
12 12 0 156 13 143
standards
Exceeding the 24-hour standard only
0
0
0
58
32
26
Exceeding the annual standard only
193
1
192
51
0
51
Source: Prepared by the Congressional Research Service with data compiled from EPA’s website for PM
designations http://www.epa.gov/pmdesignations/. Nonattainment counties for the 24-hour standard are based
on those recommended by EPA in their August 2008 letters to states; Nonattainment counties for the annual
standard are based on the October 2006 final area designations for the 1997 PM2.5 NAAQS.
Note: The counties in the table for the 2006 standards reflect those designated for the 24-hour only by EPA
August 2008 in response to States’ recommendations for nonattainment area boundaries for the 2006 PM2.5
NAAQS based on 2004-2006 monitoring data, combined with the final annual standards for the 1997 PM2.5
NAAQS.
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Figure 3. Counties Projected to be Designated Nonattainment for the 2006 PM2.5 NAAQS
(violating the annual (15 μg/m3) and/or 24-hour (65 μg/m3) standard)

Source: Prepared by the Congressional Research Service with data compiled from EPA’s website for PM designations http://www.epa.gov/pmdesignations/. Nonattainment
counties for the 24-hour standard are based on those recommended by EPA in their August 2008 letters to states; nonattainment counties for the annual standard are
based on the October 2006 final area designations for the 1997 PM2.5 NAAQS. Partial counties are shown on the map as whole counties.
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It is difficult to anticipate what effect this may have on current control measures in these areas. In
some areas, current measures focused on achieving attainment for the annual standard may be
sufficient to attain the 24-hour standard as well. Other areas may require supplementing current
measures or significant modifications to ensure compliance over a shorter averaging period. The
impacts could vary substantially from area to area within a state and from state to state depending
on many factors, including the type and locations of primary emission sources, current control
measures, the extent to which the area is exceeding the standard, topography, weather, etc.
Once designations take effect, they become an important component of state, local and tribal
governments’ efforts to reduce fine particle pollution. The designations govern what subsequent
regulatory actions states, tribes, and EPA must take in order to improve or preserve air quality in
each area.
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Under the CAA, EPA sets the nationwide standard for criteria pollutants, and EPA and states are
responsible for placing limits on emissions that contribute to criteria pollution and for regulating
entities emitting criteria pollutants. Areas designated attainment/unclassifiable will not have to
take steps to improve air quality but under the statute they must take steps to prevent air quality
from deteriorating to unhealthy levels. For those areas designated nonattainment, state, local and
tribal governments must outline detailed control requirements in plans demonstrating how they
will meet the 2006 PM2.5 NAAQS. These plans, defined as state implementation plans and
referred to as SIPs (TIPs for tribal implementation plans), must be submitted to EPA three years
after the effective date of Agency’s final designations. If states fail to develop an adequate
implementation plan, EPA can impose one.
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SIPs include pollution control measures that will be implemented by federal, state, and local
governments, and rely on models of the impact on air quality of projected emission reductions to
demonstrate attainment. SIPs must identify, among other items, specific regulations, emissions
limitations, and monitoring provisions that will bring an area into compliance. Under the CAA,
states are required to meet the 2006 PM2.5 standard “as expeditiously as practicable,” but no later
than five years from the date of designation—April 2014—unless an extension allowed under the
CAA is granted.22
States and local governments are required to develop and implement new or revised plans (SIPs)
for addressing emissions in those areas that do not meet the 2006 revised PM2.5 NAAQS. Several
counties identified by EPA in its August 2008 letters to states would be designated as
nonattainment for the PM2.5 NAAQS for the first time. As noted earlier, a large portion of the

22 Under section 172(a)(2)(A) of the CAA, EPA may grant an area an extension of the initial attainment date for one to
five years (in no case later than 10 years after the designation date for the area). A state requesting an extension must
submit an implementation plan (SIP) by the required deadline that includes, among other things, sufficient information
demonstrating that attainment by the initial attainment date is “impracticable.”
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nonattainment areas for the 2006 PM2.5 NAAQS identified by EPA in August 2008 overlap with
those areas designated nonattainment for 1997 PM2.5 NAAQS. However, as discussed in the
previous section, these counties are unable to meet the 24-hour standard, whereas previously they
were designated nonattainment based on their inability to meet the annual standard. Exceeding
both an annual and 24-hour standard may have implications with respect to existing SIPs, the
extent of which could vary significantly from area to area based on many factors. In some cases
SIPs may require substantial modifications, while in other cases the current SIP may be sufficient
to achieve compliance with both standards.
In a February 2006 advance notice of proposed rulemaking (ANPR)23 outlining an
implementation plan for the transition to the 2006 particulates standards, EPA indicated that it
would be beneficial for states to consider control strategies that may be useful in attaining the
2006 revised PM2.5 NAAQS when developing their strategies for the 1997 PM2.5 standards.
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The EPA typically publishes an “implementation rule” which describes the requirements that
states and tribes must meet in their implementation plans to achieve and maintain attainment.24
The rule also provides guidance and procedures for establishing controls to achieve and maintain
attainment. In addition to detailing provisions necessary to demonstrate how the 2006 PM2.5
NAAQS will be attained, the implementation rule generally includes guidance for submitting a
SIP when reaching attainment within the five-year requirement is impractical. The
implementation rule takes into account existing (oft times pending) federal regulations that
contribute to controlling criteria pollutants and their precursors.25
ȱȱ
The EPA expects that in many cases implementing national strategies—including the 1999
visibility protection regulations (Regional Haze Rule);26 voluntary diesel engine retrofit
programs; and federal standards scheduled to be implemented between 2004 and 2010 on cars,
light trucks, heavy-duty, and nonroad diesel engines—would provide a framework for achieving
attainment with the PM2.5 NAAQS. However, one of the key federal regulations, EPA’s May 2005
Clean Air Interstate Rule (CAIR),27 was vacated in a July 11, 2008, decision (North Carolina v.
EPA), by the U.S. Court of Appeals for the D.C. Circuit.28 CAIR was expected to serve as the

23 71 Federal Register 6718, February 9, 2006.
24 EPA published its final implementation rule for the 1997 PM2.5 NAAQS On April 25, 2007. The rule addresses
attainment demonstration and modeling; local emission reduction measures, including reasonably available control
technology (RACT), reasonably available control measures (RACM), and reasonable further progress (RFP); regional
emission reduction strategies; innovative program guidance; emission inventory requirements; transportation
conformity; and stationary source test methods (72 Federal Register 20586-20667, April 25, 2007).
25 The term precursor refers to a directly emitted pollutant that, when released to the atmosphere, forms, or contributes
to the formation of a secondary pollutant for which an ambient air quality standard has been adopted.
26 64 Federal Register 35714-35774, July 1, 1999. See CRS Report RL32483, Visibility, Regional Haze, and the Clean
Air Act: Status of Implementation, by Larry Parker and John Blodgett, also CRS Report RL32927, Clean Air Interstate
Rule: Review and Analysis, by Larry Parker.
27 Promulgated under the CAA, 42 U.S.C. 7401 et seq., 70 Federal Register 25162, May 12, 2005.
28 531 F.3d 896 (D.C. Cir. 2008). 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.
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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 PM2.5.29
The D.C. Circuit Court’s decision to vacate CAIR puts the focus back on § 126 petitions as the
available means to address interstate transport of air pollutants in the immediate future. Under §
126 of the CAA, areas may petition EPA to impose controls on upwind sources that significantly
contribute to their nonattainment of the standard. EPA has never granted a § 126 petition in the
manner outlined by the statute. The D.C. Circuit’s decision regarding the CAIR could result in
significant delays, and has garnered attention in Congress.30
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Designated nonattainment areas also are subject to new source review (NSR) requirements.
Enacted as part of the 1977 CAA Amendments and modified in the 1990 CAA Amendments,
NSR is designed to ensure that newly constructed facilities, or substantially modified existing
facilities, do not result in violation of applicable air quality standards. NSR provisions outline
permitting requirements both for construction of new major pollution sources and for
modifications to existing major pollution sources. The specific NSR requirements for affected
sources depend on whether the sources are subject to Prevention of Significant Deterioration
(PSD) or nonattainment provisions.31
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If new or revised SIPs for attainment establish or revise a transportation-related emissions budget,
or add or delete transportation control measures (TCMs), they will trigger “conformity”
determinations. Transportation conformity is required by the CAA, Section 176(c),32 to prohibit
federal funding and approval for highway and transit projects unless they are consistent with
(“conform to”) the air quality goals established by a SIP, and will not cause new air quality
violations, worsen existing violations, or delay timely attainment of the national ambient air
quality standards.
EPA promulgated several transportation conformity rules and rule amendments since the statute
was strengthened as part of the 1990 CAA.33 The rules generally establish the criteria and

29 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).
30 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.
31 See Clean Air Act, Part D—Plan Requirements for Nonattainment Areas, sections 171-178, codified at 40 CFR
52.24(f)(10).
32 42 U.S.C. 7506(c).
33 EPA conformity rule promulgated on November 24, 1993 (58 Federal Register 62188), and subsequently amended;
see EPA’s “Chronological List of Transportation Conformity Rulemakings” at http://www.epa.gov/otaq/stateresources/
transconf/conf-regs-c.htm, and “Transportation Conformity Regulations Current as of January 2008,” EPA420-B-08-
(continued...)
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procedures for determining whether transportation plans, transportation improvement programs
(TIPs), or projects conform to a state’s SIP.
ȱ
The designation of geographical areas unable to meet the NAAQS is a critical step in NAAQS
implementation, and historically has been an issue of concern and debate among EPA, states and
tribes, various stakeholders, and many Members of Congress. The EPA’s 2006 tightening of the
PM2.5 standards will increase the number of areas (typically defined by counties or portions of
counties) in nonattainment, and subsequently potentially result in an encumbrance on states to
achieve compliance.
In August 2008 letters to states, EPA provided its proposed modifications to nonattainment
designation recommendations submitted by states for the 2006 PM2.5 NAAQS. EPA intends to
finalize the designations for the 2006 PM2.5 NAAQS by December 18, 2008, although this
determination could be delayed up to a year if the Administrator determines that the agency has
insufficient information. Historically, there have been disagreements between EPA and states, and
other stakeholders, with regard to final NAAQS nonattainment designations.
Following the final nonattainment determination, State, local and tribal governments are to
outline detailed control requirements in plans (or SIPs) demonstrating how areas designated
nonattainment will meet the 2006 PM2.5 NAAQS. Although a large portion of the nonattainment
areas for the 2006 PM2.5 NAAQS identified by EPA in August 2008 overlap with those areas
designated nonattainment for 1997 PM2.5 NAAQS, these new designations are based on the 24-
hour standard, whereas the previous designations were based on the annual standard. The
implications of this with regard to SIPs could vary significantly from area to area based on
numerous factors.
States would not be required to submit SIPs until 2012, and would not have to meet the PM2.5
standard until 2014 (or April 2019, if qualified for an extension34). The EPA is not requiring new
nonattainment designations for PM10, and it does not anticipate any significant incremental cost
impacts associated with the change in the PM10 standard. The associated impacts on specific
geographical nonattainment areas would be speculative at best, because compliance with the 2006
revised particulates NAAQS is several years off.
With regard to the 1997 PM2.5 NAAQS, states with nonattainment areas must be in compliance
with the 1997 PM2.5 NAAQS by April 5, 2010, unless they are granted an extension.
Implementation of the 1997 PM2.5 NAAQS, already delayed considerably, is threatened with
further delay as a result of the U.S. Court of Appeals for the D.C. Circuit’s July 11, 2008, decision
(North Carolina v. EPA) that would vacate the Clean Air Interstate Rule (CAIR).35 Further delays

(...continued)
001, January 2008, http://www.epa.gov/otaq/stateresources/transconf/regs/420b08001.pdf.
34 Under § 172(a)(2)(A) of the CAA, EPA may grant an area an extension of the initial attainment date for one to five
years (not later than 10 years after the designation date for the area). A state requesting an extension must submit an
implementation plan (SIP) by the required deadline that includes, among other things, sufficient information
demonstrating that attainment by the initial attainment date is “impracticable.”
35 42 U.S.C. 7401 et seq.
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in implementing 1997 PM2.5 NAAQS would have direct implications for implementing the 2006
PM2.5 NAAQS.
Concerns regarding looming key implementation milestones and attainment deadlines for the
2006 PM2.5 NAAQS, and associated delays effecting implementation of the current 1997 PM2.5
NAAQS, will remain an issue of considerable debate for many stakeholders and interest groups,
as well as Congress.
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Table A-1. Schedule for Implementation of the 1997 and the 2006 PM2.5 NAAQS
1997 PM2.5
Milestones
NAAQS 2006
PM2.5 NAAQS
Revised standard promulgated
July 18, 1997
October 10, 2006
Revised standard effective date
September 1997
December 18, 2006
State-tribal area designation recommendations
February 2004
December 18, 2007 (based
(based on 2000-
on 2004-2006 monitoring
2002 monitoring
data)
data)
EPA notifies states and tribes regarding modifications to their
June-July 2004
August 2008
recommendations
EPA promulgates final area designations (required one year after January 5, 2005
December 18, 2008
states and tribes make recommendations)
EPA proposes PM2.5 implementation rule
November 1, 2005 NA
Final Area designations effective date (typically not later than 90 April 5, 2005
April 2009
days after Federal Register publication)
States with new transportation projects submit conformity
April 5, 2006
December 18, 2009
determination (required within one year of the effective date of
(projected)
nonattainment designation)
EPA promulgates final PM2.5 implementation rule
April 25, 2007
NA
States and tribes submit revised implementation plans (SIPs)
April 2008
April 2012
(required three years after final area designations effective date (ongoing)
unless extension granted)
NAAQS statutory compliance deadline for attainment (required April 2010-2015
April 2014-2019
within five years after final area designations effective date; up to
ten years with extension)
Source: Prepared by the Congressional Research Service based on U.S. Environmental Protection Agency fact
sheets and guidance documents, and relevant Federal Register notices.
The timeline presented in Table A-1 above reflects the most recent key milestone dates for
implementing the 1997 and the 2006 PM2.5 NAAQS, including actual completions. These
milestones are driven primarily by statutory requirements. The table follows an EPA milestone
schedule outlined in an April 21, 2003, memorandum to EPA regional administrators that also
provided the nonbinding guidance for implementation of the 1997 PM2.5 area designations,36 and
the agency’s projected timeline for the 2006 PM2.5 NAAQS.37

36 EPA memorandum, April 21, 2003, from the Office of Air and Radiation Assistant Administrator Jeffrey R.
Holmstead to EPA Regional Administrators, available at [http://www.epa.gov/ttn/naaqs/pm/pm25_guide.html].
37 See [http://www.epa.gov/oar/particlepollution/naaqsrev2006.html].
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Table B-1. Recommended Nonat ainment Areas for the 2006 PM2.5 NAAQS and
Final Nonattainment Designations for the 1997 PM2.5 NAAQS
2006 PM2.5 NAAQS
1997 PM2.5 NAAQS
EPA
State
Final
Recommended
Recommended Final
Designations
Designations
24-Hour
24-Hour
24-Hour
Annual
Standard
Standard
Standard
Standard
State/Area Name
Counties and Partial Counties (p)
ALABAMA

Birmingham, AL
Jefferson Jefferson
Jefferson
Shelby
Shelby

Walker (p)

Walker (p)
Chattanooga, AL-TN-
Jackson
(p)
GA
ALASKA

Fairbanks, AK
Fairbanks N. Star (p)
Fairbanks N. Star (p)

Juneau, AK
Juneau (p)

ARIZONA

Nogales, AZ
Santa Cruz
Santa Cruz (p)

CALIFORNIA

Chico, CA
Butte Butte
(p)

Imperial County, CA
Imperial Imperial
(p)

Los Angeles, CA
Los Angeles (p)

Los Angeles (p)
Los Angeles (p)
Orange
Orange
Orange

Riverside (p)

Riverside (p)
Riverside (p)

San Bernardino (p)

San Bernardino (p)
San Bernardino
(p)
Sacramento, CA
El Dorado (p)

Placer
(p)

Sacramento
Sacramento

Solano
(p)

Yolo

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2006 PM2.5 NAAQS
1997 PM2.5 NAAQS
EPA
State
Final
Recommended
Recommended Final
Designations
Designations
24-Hour
24-Hour
24-Hour
Annual
Standard
Standard
Standard
Standard
State/Area Name
Counties and Partial Counties (p)
San Francisco Bay
Alameda Alameda

Area, CA

Contra Costa
Contra Costa

Marin
Marin

Napa
Napa

San Francisco
San Francisco

San Mateo
San Mateo

Santa Clara
Santa Clara

Solano (p)
Solano (p)

Sonoma (p)
Sonoma (p)

San Joaquin Valley, CA Fresno Fresno
Fresno
Fresno

Kern (p)
Kern (p)
Kern (p)
Kern (p)
Kings
Kings
Kings
Kings
Madera
Madera
Madera
Madera
Merced
Merced
Merced
Merced

San Joaquin
San Joaquin
San Joaquin
San
Joaquin
Stanislaus
Stanislaus
Stanislaus
Stanislaus
Tulare
Tulare
Tulare
Tulare
Yuba City-Marysville,
Sutter Sutter
(p)

CA
Yuba
Yuba(p)

CONNECTICUT

New York, NY-NJ-CT
Fairfield Fairfield
Fairfield

New Haven
New Haven

New
Haven
DELAWARE

Philadelphia-
New Castle
New Castle

New
Wilmington, PA-NJ-DE
Castle
DISTRICT OF COLUMBIA

Washington, DC-MD-

Entire District
VA
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2006 PM2.5 NAAQS
1997 PM2.5 NAAQS
EPA
State
Final
Recommended
Recommended Final
Designations
Designations
24-Hour
24-Hour
24-Hour
Annual
Standard
Standard
Standard
Standard
State/Area Name
Counties and Partial Counties (p)
ILLINOIS

Chicago-Gary-Lake
Cook Cook Cook
County, IL-IN
DuPage
DuPage
DuPage

Grundy (p)
Grundy (p)

Grundy (p)
Kane
Kane
Kane

Kendall (p)
Kendall (p)

Kendall (p)
Lake
Lake
Lake
McHenry
McHenry
McHenry
Will
Will
Will
Davenport-Moline-
Rock Island

Rock Island, IA-IL
Paducah-Mayfield, KY-
Massac

IL
St. Louis, MO-IL
Madison Madison
Madison
Monroe
Monroe
Monroe

Randolph (p)
Randolph (p)

Randolph (p)

St. Clair
St. Clair

St. Clair
INDIANA

Chicago-Gary-Lake
Lake Lake
County, IL-IN
Porter

Cincinnati-Hamilton,
Dearborn (p)

Dearborn (p)
OH-KY-IN
Evansville, IN
Dubois

Dubois

Gibson (p)

Gibson (p)

Pike (p)

Pike (p)

Spencer (p)

Spencer (p)
Vanderburgh
Vanderburgh
Vanderburgh
Warrick
Warrick
Indianapolis, IN
Hamilton

Hamilton
Hendricks
Hendricks
Johnson
Johnson
Marion
Marion
Marion
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2006 PM2.5 NAAQS
1997 PM2.5 NAAQS
EPA
State
Final
Recommended
Recommended Final
Designations
Designations
24-Hour
24-Hour
24-Hour
Annual
Standard
Standard
Standard
Standard
State/Area Name
Counties and Partial Counties (p)

Morgan

Morgan
Lafayette-Frankfort, IN Tippecanoe Tippecanoe

Louisville, KY-IN
Clark
Clark
Floyd
Floyd

Jefferson (p)

Jefferson (p)
Vincennes, IN
Knox Knox
IOWA

Davenport-Moline-
Scott Scott
(p)

Rock Island, IA-IL
Muscatine, IA
Muscatine Muscatine
(p)

KENTUCKY

Cincinnati-Hamilton,
Boone Boone Boone
OH-KY-IN
Campbell
Campbell
Campbell
Kenton
Kenton
Kenton
Clarksville, TN-KY
Muhlenberg

Huntington-Ashland,
Boyd
Boyd
WV-KY-OH

Lawrence (p)

Lawrence (p)
Louisville, KY-IN
Bullitt
Bullitt
Jefferson
Jefferson
Paducah-Mayfield, KY- McCracken

IL
MARYLAND

Baltimore, MD
Anne Arundel
Anne Arundel

Anne Arundel

Baltimore City
Baltimore City

Baltimore City
Baltimore
Baltimore
Baltimore
Carroll
Carroll
Carroll
Harford
Harford
Harford
Howard
Howard
Howard
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2006 PM2.5 NAAQS
1997 PM2.5 NAAQS
EPA
State
Final
Recommended
Recommended Final
Designations
Designations
24-Hour
24-Hour
24-Hour
Annual
Standard
Standard
Standard
Standard
State/Area Name
Counties and Partial Counties (p)
Washington, DC-MD-

Charles
VA
Frederick

Montgomery

Prince George’s
Martinsburg, WV-

Washington
Hagerstown, MD
MICHIGAN

Detroit-Ann Arbor, MI
Livingston Livingston
Livingston
Macomb
Macomb
Macomb
Monroe
Monroe
Monroe
Oakland
Oakland
Oakland

St. Clair
St. Clair

St. Clair
Washtenaw
Washtenaw
Washtenaw
Wayne
Wayne
Wayne
Grand Rapids, MI
Kent Kent
Ottawa

MISSOURI

St. Louis, MO-IL
Franklin

Franklin
Jefferson
Jefferson

St. Charles

St. Charles

St. Louis

St. Louis

St. Louis City

St. Louis City
MONTANA

Libby, MT
Lincoln (p)

Lincoln (p)
NEW JERSEY

Allentown, PA

Warren (p)

New York, NY-NJ-CT
Bergen Bergen
Bergen
Essex
Essex
Essex
Hudson
Hudson
Hudson
Mercer
Mercer
Mercer
Middlesex
Middlesex
Middlesex
Monmouth
Monmouth
Monmouth
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2006 PM2.5 NAAQS
1997 PM2.5 NAAQS
EPA
State
Final
Recommended
Recommended Final
Designations
Designations
24-Hour
24-Hour
24-Hour
Annual
Standard
Standard
Standard
Standard
State/Area Name
Counties and Partial Counties (p)

Morris Morris
Morris
Passaic
Passaic
Passaic
New York, NY-NJ-CT
Somerset Somerset
Somerset
(cont.)
Union
Union
Union
Philadelphia-
Burlington Burlington
Burlington
Wilmington, PA-NJ-DE
Camden
Camden
Camden
Gloucester
Gloucester
Gloucester
NEW YORK

New York, NY-NJ-CT
Bronx Bronx Bronx
Kings
Kings
Kings
Nassau
Nassau
Nassau

New York
New York

New York
Orange
Orange
Orange
Queens
Queens
Queens
Richmond
Richmond
Richmond
Rockland
Rockland
Rockland
Suffolk
Suffolk
Suffolk
Westchester
Westchester
Westchester
NORTH CAROLINA

Hickory, NC

Catawba
Greensboro- Winston

Davidson
Salem-High Point, NC
Guilford
OHIO

Canton-Massillon, OH Stark Stark Stark
Cincinnati-Hamilton,
Butler Butler
Butler
OH-KY-IN
Clermont
Clermont
Clermont
Hamilton
Hamilton
Hamilton
Warren
Warren
Warren
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2006 PM2.5 NAAQS
1997 PM2.5 NAAQS
EPA
State
Final
Recommended
Recommended Final
Designations
Designations
24-Hour
24-Hour
24-Hour
Annual
Standard
Standard
Standard
Standard
State/Area Name
Counties and Partial Counties (p)
Cleveland-Akron-
Ashtabula (p)

Ashtabula (p)
Lorain, OH
Cuyahoga
Cuyahoga
Cuyahoga
Lake
Lake
Lake
Lorain
Lorain
Lorain
Medina
Medina
Medina
Portage
Portage
Portage
Summit
Summit
Summit
Columbus, OH
Coshocton (p)

Coshocton (p)
Delaware
Delaware
Delaware
Fairfield
Fairfield
Fairfield
Franklin
Franklin
Franklin
Licking
Licking
Licking
Dayton-Springfield, OH Clark
Clark
Greene
Greene
Greene
Montgomery
Montgomery
Montgomery
Huntington-Ashland,
Adams (p)

Adams (p)
WV-KY-OH

Gallia (p)

Gallia (p)
Lawrence
Lawrence
Scioto
Scioto
Parkersburg- Marietta, Washington Washington
Washington
WV-OH
Steubenville- Weirton,
Jefferson Jefferson
Jefferson
OH-WV
Wheeling, WV-OH
Belmont
Youngstown, OH
Mahoning Mahoning

Trumbull
Trumbull

OREGON

Klamath Falls, OR
Klamath (p)
Klamath (p)

Oakridge, OR
Lane (p)
Lane (p)

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ŘŖŖŜȱȱȱȱ¢ȱȱȱȱȱȱǻŘǯśǼȱ
ȱ
2006 PM2.5 NAAQS
1997 PM2.5 NAAQS
EPA
State
Final
Recommended
Recommended Final
Designations
Designations
24-Hour
24-Hour
24-Hour
Annual
Standard
Standard
Standard
Standard
State/Area Name
Counties and Partial Counties (p)
PENNSYLVANIA

Allentown, PA
Lehigh Lehigh

Northampton
Northampton

Harrisburg-Lebanon-
Cumberland Cumberland
Cumberland
Carlisle, PA
Dauphin
Dauphin
Dauphin
Lebanon
Lebanon
Lebanon
Johnstown, PA
Cambria Cambria
Cambria

Indiana (p)
Indiana (p)

Indiana (p)
Lancaster, PA
Lancaster Lancaster
Lancaster
Liberty-Clairton, PA
Allegheny (p)
Allegheny (p)

Allegheny (p)
Philadelphia-
Bucks Bucks Bucks
Wilmington, PA-NJ-DE
Chester
Chester
Chester
Delaware
Delaware
Delaware
Montgomery
Montgomery
Montgomery
Philadelphia
Philadelphia
Philadelphia
Pittsburgh-Beaver
Allegheny (p)
Allegheny (p)

Allegheny (p)
Valley, PA

Armstrong (p)
Armstrong (p)

Armstrong (p)
Beaver
Beaver
Beaver
Butler
Butler
Butler

Greene (p)

Greene (p)

Lawrence (p)
Lawrence (p)

Lawrence (p)
Washington
Washington
Washington
Westmoreland
Westmoreland
Westmoreland
Reading, PA
Berks Berks Berks
York, PA
York York York
ȱȱȱ
ŘŚȱ

ŘŖŖŜȱȱȱȱ¢ȱȱȱȱȱȱǻŘǯśǼȱ
ȱ
2006 PM2.5 NAAQS
1997 PM2.5 NAAQS
EPA
State
Final
Recommended
Recommended Final
Designations
Designations
24-Hour
24-Hour
24-Hour
Annual
Standard
Standard
Standard
Standard
State/Area Name
Counties and Partial Counties (p)
WASHINGTON

Seattle-Tacoma, WA Pierce (p)
Pierce (p)

WEST VIRGINIA

Charleston, WV
Kanawha Kanawha
Kanawha
Putnam
Putnam
Putnam
Huntington-Ashland,
Cabell
Cabell
WV-KY-OH

Mason (p)

Mason (p)
Wayne
Wayne
Martinsburg, WV-

Berkeley
Hagerstown, MD
Morgantown, WV
Monongalia

Parkersburg- Marietta, Pleasants (p)

Pleasants (p)
WV-OH
Wood
Wood
Steubenville- Weirton,
Brooke Brooke
Brooke
OH-WV
Hancock
Hancock
Hancock
Wheeling, WV-OH

Marshall
Ohio
WISCONSIN

Green Bay, WI
Brown

Madison-Baraboo, WI
Columbia

Dane

Milwaukee-Racine, WI Milwaukee

Racine

Waukesha

TOTALS

25 states
20 states
1 state
20 states and D.C.

57 areas
46 areas
2 areas
39 areas

169 whole counties
116 whole counties
9 whole counties
176 whole counties

46 partial counties
31 partial counties
3 partial counties
32 partial counties
Source: Compiled by CRS using data from EPA PM designations websites.

ȱȱȱ
ŘŜȱ

ŘŖŖŜȱȱȱȱ¢ȱȱȱȱȱȱǻŘǯśǼȱ
ȱ
ȱȱȱ

Robert Esworthy

Specialist in Environmental Policy
resworthy@crs.loc.gov, 7-7236

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Řŝȱ