.

2006 National Ambient Air Quality Standards
(NAAQS) for Fine Particulate Matter (PM2.5):
Designating Nonattainment Areas
Robert Esworthy
Specialist in Environmental Policy
December 17, 2009
Congressional Research Service
7-5700
www.crs.gov
R40096
CRS Report for Congress
P
repared for Members and Committees of Congress
c11173008

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2006 Fine Particulate Matter (PM2.5) NAAQS Nonattainment Designations

Summary
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 have been
the subject of considerable congressional oversight. EPA’s ongoing 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. On November 13, 2009, EPA published its final designations for the 2006 PM NAAQS
that include 120 counties and portions of counties in 18 states as nonattainment areas based on
2006 through 2008 air quality monitoring data. The final designations, which include tribal land
of 22 tribes, were effective as of December 14, 2009. States have three years from the effective
date to submit State Implementation Plans (SIPs), which identify specific regulations and
emission control requirements that would bring an area into compliance.
In December of 2008 EPA had identified 211 counties and portions of counties (58 areas) in 25
states for designation as nonattainment for the 2006 PM NAAQS based on 2005 through 2007
data. The publication of these designations—and thus the effective date of the final
designations—was delayed pending review by the current Administration. The review was
initiated, in part, in response to a White House January 20, 2009, memorandum regarding
regulatory review. This review and the availability of more current air quality monitoring data
resulted in the final designations published in November 2009.
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 revoking the annual standard for PM10.
EPA’s final nonattainment designations are only for the revised 2006 24-hour PM2.5 standard. The
EPA did not require new nonattainment designations for PM10. The final designations for the 2006
PM2.5 NAAQS include a few areas designated nonattainment for PM2.5 for the first time, but, as
expected, the majority of the counties identified overlap with EPA’s final nonattainment
designations for the 1997 PM2.5 NAAQS. EPA’s designations for the 1997 PM2.5 NAAQS
included all or part of 204 counties in 20 states and the District of Columbia. Most of them were
only exceeding the annual standard; only 12 counties were exceeding both the 24-hour and the
annual standards. Thus, the 2006 tightening of the 24-hour standard resulted in an increased
number of areas being designated nonattainment based on exceedances of both the 24-hour and
the annual standards.

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2006 Fine Particulate Matter (PM2.5) NAAQS Nonattainment Designations

Contents
Introduction ................................................................................................................................ 1
EPA’s 2006 Changes to the Particulates NAAQS ......................................................................... 2
Designation of Geographical Nonattainment Areas...................................................................... 3
NAAQS Designation Process ................................................................................................ 4
PM2.5 NAAQS Designations.................................................................................................. 5
Comparing the 2006 and 1997 PM2.5 NAAQS Designations .................................................. 9
Demonstrating Attainment with the 2006 PM2.5 NAAQS ........................................................... 13
State Implementation Plans (SIPs)....................................................................................... 13
EPA NAAQS Implementation Rules.............................................................................. 14
National Regulations..................................................................................................... 15
New Source Review...................................................................................................... 16
Transportation Conformity ............................................................................................ 16
Conclusions .............................................................................................................................. 17

Figures
Figure 1. Counties in Nonattainment for the 2006 PM2.5 NAAQS—EPA’s December 22,
2008, Final Designations .......................................................................................................... 7
Figure 2. Currently Designated Nonattainment Areas 1997 PM2.5 Standards .............................. 10
Figure 3. Counties Designated Nonattainment for the 2006 PM2.5 NAAQS................................ 12
Figure D-1. Counties in Nonattainment for the 2006 PM2.5 NAAQS—EPA’s Designations
as of December 22, 2008,....................................................................................................... 32

Tables
Table 1. Counties Designated Nonattainment for the 1997 PM2.5 NAAQS and
Nonattainment for the 2006 PM2.5 NAAQS ............................................................................ 11
Table A-1. Schedule for Implementation of the 1997 and the 2006 PM2.5 NAAQS ..................... 19
Table B-1. Nonattainment Areas for the 2006 PM2.5 NAAQS as Identified by EPA in the
October 8, 2009, Final Designations and in the December 28, 2008, Status Table, and
Final Nonattainment Designations for the 1997 PM2.5 NAAQS .............................................. 20
Table C-1. EPA’s October 8, 2009 Geographic Designations for 2006 PM NAAQS:
Tribes in 24-Hour PM2.5 Nonattainment Areas ........................................................................ 31

Appendixes
Appendix A. Comparative Timeline for Implementing the 1997 and 2006 PM2.5 NAAQS.......... 19
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Appendix B. Comparison of Final and Interim Nonattainment Designation Areas for the
2006 PM2.5 NAAQS and the Final Nonattainment Designation Areas for the 1997 PM2.5
NAAQS ................................................................................................................................. 20
Appendix C. Tribal Lands—Designations for the 2006 PM2.5 NAAQS 24-Hour Standard.......... 31
Appendix D. Map Depicting Counties in Nonattainment for the 2006 PM2.5 NAAQS—
EPA’s Designation as of December 22, 2008 .......................................................................... 32

Contacts
Author Contact Information ...................................................................................................... 33

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Introduction
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 set 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 then 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.5 EPA published the final designations for the 2006 PM2.5 NAAQS on November 13,
2009.6 The final designations rule is effective December 14, 2009 (30 days from the date of
publication). The EPA final designations reflect a change from those announced by the agency in
December 22, 2008.7 The publication of final designations—and thus the effective date of the
final designations—had been delayed since January 2009 pending review by the incoming
Administration. EPA initiated review of several previous agency decisions, including those

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.
6 74 Federal Register 58688-58781, November 13, 2009; see also EPA’s website, “Area Designations for 2006 24-
Hour Fine Particulate (PM2.5) Standards—Regulatory Actions,” http://www.epa.gov/pmdesignations/2006standards/
regs.htm#4.
7 See EPA’s website “Area Designations for 2006 24-Hour Fine Particulate (PM2.5) Standards—December 2008 Area
Status (Not Final Designations),” http://www.epa.gov/pmdesignations/2006standards/documents/2008-12-22/12-
08table.htm.
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covered by the White House January 20, 2009, memorandum,8 and the Office of Management
and Budget’s subsequent January 21, 2009, memorandum,9 on regulatory review.
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 contains a comparative timeline for implementing the 2006 and 1997 PM2.5
NAAQS. Appendix B provides a state and county breakdown of EPA’s November 13, 2009, final
designated nonattainment areas and areas indentified by EPA on December 22, 2008, proposed by
the states for the 2006 PM2.5 NAAQS, as well as the final EPA nonattainment designations for the
1997 PM2.5 NAAQS. Appendix C identifies tribes included in EPA’s final nonattainment
designations 2006 PM2.5 NAAQS.
The 2006 particulates NAAQS generated national interest and debate, and oversight in Congress.
Additionally, several states and industry, agriculture, business, and public advocacy groups
petitioned the U.S. Court of Appeals for the District of Columbia Circuit, challenging certain
aspects of EPA’s revisions.10 A February 24, 2009, decision11 by the court granted the petitions in
part, denying other challenges, and remanded the standards to EPA for further consideration.
While the court did not specifically vacate the 2006 PM standards, and their implementation will
proceed, the decision and EPA’s eventual actions may prompt renewed interest in PM NAAQS
among members of Congress. For background on the process used to establish the 2006
particulates NAAQS and analysis of associated issues, including the D.C. Circuit’s February 2009
decision, see CRS Report RL34762, The National Ambient Air Quality Standards (NAAQS) for
Particulate Matter (PM): EPA’s 2006 Revisions and Associated Issues, by Robert Esworthy and
James E. McCarthy.
EPA’s 2006 Changes to the Particulates NAAQS
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 visibility impairment as well as damage to
crops, vegetation, property, building materials, etc.12

8 Memorandum to Heads and Acting Heads of Executive Departments and Agencies from Rahm Emanuel, Assistant to
the President and Chief of Staff, regarding Regulatory Review, January 20, 2009, 74 Federal Register 4435 January 26,
2009; the memorandum is also available at http://www.whitehouse.gov/omb/assets/
information_and_regulatory_affairs/regulatory_review_012009.pdf.
9 Memorandum to Heads and Acting Heads of Executive Departments and Agencies from Peter R. Orszag, Director,
Office of Management and Budget, regarding Implementation of Memorandum Concerning Regulatory Review,
January 21, 2009, http://www.whitehouse.gov/omb/assets/agencyinformation_memoranda_2009_pdf/m09-08.pdf.
10 Cases were consolidated with American Farm Bureau Federation v. U.S. EPA, 2009 Westlaw 437050, No. 06-1410
(D.C. Cir. 2006).
11 American Farm Bureau Federation v. U.S. EPA, No. 06-1410 (D.C. Cir., February 24, 2009).
12 The use of public welfare in the CAA “includes, but is not limited to, effects on soils, water, crops, vegetation,
(continued...)
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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: strengthened the daily (24-hour) standard, which had allowed 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: retained the daily standard at 150 µg/m3 set in 1987 but changed 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
PM10.13
As will be shown in more detail in the following section, strengthening the daily standard for
PM2.5 has implications for those counties and partial counties 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. The EPA is not requiring new nonattainment designations for PM10 since the
standards were not strengthened. To the contrary, a few counties previously designated
nonattainment for PM10 have been determined by EPA to be in attainment since the 2006 revisions
to the particulates NAAQS were promulgated.14
Designation of Geographical Nonattainment Areas
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

(...continued)
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 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.
14 See discussion and map in Appendix A depicting PM10 nonattainment areas, in CRS Report RL34762, The National
Ambient Air Quality Standards (NAAQS) for Particulate Matter (PM): EPA’s 2006 Revisions and Associated Issues, by
Robert Esworthy and James E. McCarthy.
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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.
NAAQS Designation Process
The NAAQS designation process is intended as a cooperative federal-state-tribal15 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”16 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.17 EPA began
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.18 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 PM2.5 NAAQS published November 13, 2009, are based on
air quality monitoring data for calendar years 2006 through 2008.

15 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.
16 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.
17 A federally referenced monitor is one that has been accepted for use by EPA for comparison of the NAAQS by
meeting the design specifications and certain precision and bias (performance) specifications (40 CFR Part 58).
18 Revisions to Ambient Air Monitoring Regulations, final rule, 71 Federal Register 61235-61328, October 17, 2006.
http://www.epa.gov/air/particlepollution/actions.html.
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In addition to air emission and air quality data, EPA considers a number of other relevant
factors,19 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.
PM2.5 NAAQS Designations20
On November 13, 2009, EPA published its designations of 31 areas in 18 states, comprising 120
counties (89 counties and portions of 31 additional counties) for nonattainment of the revised
2006 24-hour PM2.5 standard.21 (see Table B-1 in Appendix B for state-by-state county/area
nonattainment designations). The counties (and partial counties) that EPA designated as
nonattainment for the 2006 PM2.5 NAAQS are indicated in the map in Figure 1. 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 EPA’s November 2009 final designations, which are based on air quality monitoring data for
calendar years 2006 through 2008, do not include counties violating the annual standard, as the
level is unchanged from the 1997 PM2.5 NAAQS. As with the designations for the 1997 PM2.5 and
other criteria pollutant NAAQS standards, several areas include counties from multiple states.
EPA also included portions of tribal lands of 22 tribes in areas designated nonattainment (see
Appendix C for list of Tribes included in the final 2006 24-hour PM2.5 NAAQS nonattainment
areas).
The EPA’s final designations differ from those identified by the agency on December 22, 2008,
based on air quality monitoring data for calendar years 2005 through 2007. At that time, EPA had
identified 58 areas in 25 states, comprising 211 counties (154 counties and portions of 57
additional counties) for designation as nonattainment of the revised 2006 24-hour PM2.5
standard22 (see Table B-1 in Appendix B for a comparison of the state-by-state county/area

19 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.
20 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.
21 See footnote 6.
22 See EPA’s website, “Area Designations for 2006 24-Hour Fine Particulate (PM2.5) Standards—December 2008 Area
Status (Not Final Designations),” http://www.epa.gov/pmdesignations/2006standards/documents/2008-12-22/12-
08table.htm.
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nonattainment designations; counties (and partial counties) designated as nonattainment for the
2006 PM2.5 NAAQS as of December 22, 2008 are indicated on the map in Figure D-1 of
Appendix D).
Publication of a final designation rule for the 2006 PM2.5 NAAQS was delayed pending review by
the agency under the current Administration. The review of the final designation rule, along with
several other agency proposed and final actions introduced toward the end of the previous
Administration, was initiated, in part, in response to a White House January 20, 2009,
memorandum,23 and the Office of Management and Budget’s subsequent January 21, 2009,
memorandum,24 regarding regulatory review. During this review, EPA revised its designations
based on more current monitoring data (calendar years 2006-2008).
Delaying publication of the final designation rule resulted in the delay of the expected effective
date, which had been scheduled for April 2009.25 The effective date of the final designations rule
is December 14, 2009 (30 days from the date of publication).

23 See footnote 8.
24 See footnote 9.
25 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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Figure 1. Counties in Nonattainment for the 2006 PM2.5 NAAQS—EPA’s December 22, 2008, Final Designations
(violating the 24-hour standard (35 μg/m3) only)

Source: Prepared by the Congressional Research Service based on EPA’s final designations for the 2006 PM2.5 NAAQS announced November 13,
2009, with data obtained from EPA.
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The majority of U.S. counties (including partial counties and tribal lands) were designated
attainment/unclassifiable. While the final number of nonattainment areas and associated counties
can seem small compared with the approximately 3,000 counties throughout 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 1997 PM2.5 NAAQS.
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
standards, Metropolitan Statistical Areas or Consolidated Metropolitan Statistical Areas26 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
guidance27 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.
By 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.28 The state-recommended
designations were primarily based on air quality monitoring data for calendar years 2004 through
2006, criteria and technical guidance from EPA and assistance from its regional offices, and
states’ own relevant information and criteria.
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 agency identified 57 areas in 26 states, comprising 213 counties (167 counties and
portions of 46 additional counties) for designation as nonattainment for the revised 2006 24-hour
PM2.5 standard. The EPA solicited the states’ comments and additional information for
consideration in determining the final designations.29 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.

26 As defined by the Office of Management Budget. For more information on metropolitan areas, see
http://www.census.gov/population/www/estimates/aboutmetro.html.
27 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.
28 For detailed information regarding state recommendations for the 2006 PM2.5 NAAQS, see EPA’s PM Designation
website at http://www.epa.gov/pmdesignations/2006standards/state.htm.
29 For information regarding EPA’s August 19, 2008, proposed designations, see http://www.epa.gov/pmdesignations/
2006standards/regs.htm#2.
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States (and tribal groups) had 120 days to respond to EPA’s recommendations, and the agency
also issued a notice30 for a 30-day public comment period. As occurred with EPA’s proposed
nonattainment designations for the 1997 PM2.5 NAAQS, 31 several states challenged the agency
and maintained support for their original recommendations in response to the agency’s proposed
nonattainment areas for the 2006 PM2.5 NAAQS. EPA designations for the 2006 PM2.5 NAAQS as
of December 22, 2008, based on 2005 through 2007 air monitoring data reflected minor
modifications to those proposed; primarily, two 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.32
As discussed previously in this report, the final designations for the 2006 PM2.5 NAAQS based on
2006 through 2008 monitoring data resulted in fewer nonattainment areas/counties than EPA had
proposed in August 2008 and identified as of December 2008 (Table B-1 in Appendix B includes
a state-by-state comparison of EPA’s final county/area nonattainment designations with the
agency’s designations as of December 22, 2008). EPA’s final designations for the 2006 PM2.5
NAAQS published in November 2009 included 27 fewer nonattainment counties than identified
as of December 2008, 26 fewer areas than proposed in August 2008, and 17 fewer areas than
recommended by the states. EPA’s final nonattainment designation areas included 7 fewer states
and 91 fewer counties than identified as of December 2008, 7 fewer states and 95 fewer counties
than proposed, and 3 fewer states and 27 fewer counties than recommended by the states.33
Comparing the 2006 and 1997 PM2.5 NAAQS Designations
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 204 counties in 20 states and the District of Columbia.34 As indicated in the map in Figure 2,
below, 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 were designated attainment/unclassifiable for
the 1997 PM2.5 NAAQS.

30 73 Federal Register 51259-51260, September 2, 2008.
31 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. The petitions were for counties in Georgia, Illinois, Michigan, Missouri, Ohio, and West
Virginia; see http://www.epa.gov/pmdesignations/1997standards/regs.htm.
32 See EPA’s website at http://www.epa.gov/pmdesignations/2006standards/documents/2008-12-22/12-08table.htm,
which provides a table with state-by-state comparisons of designations for the 2006 PM2.5 NAAQS as recommend by
the states, proposed by EPA August 19, 2008, and as identified by EPA December 22, 2008.
33 See footnote 32.
34 See EPA’s PM2.5 Designations websites at http://www.epa.gov/pmdesignations and http://www.epa.gov/oar/oaqps/
greenbk/qnca.html. 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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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: Prepared by the Congressional Research Service based on EPA’s final designations for the 1997 PM2.5 NAAQS, with data obtained from EPA.

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2006 Fine Particulate Matter (PM2.5) NAAQS Nonattainment Designations

Table 1 below illustrates the comparative geographic distribution of counties designated
nonattainment for the 2006 PM2.5 NAAQS (based on EPA’s October 8, 2009, final designations),
and those counties in EPA’s final area designations for the 1997 PM2.5 NAAQS. Based on EPA’s
October 2009 final designations for the 2006 PM2.5 NAAQS, 38 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 resulted in an
increased number of areas (82 counties) being designated nonattainment based on exceedances of
both the 24-hour and the annual standard.
Table 1. Counties Designated Nonattainment for the 1997 PM2.5 NAAQS and
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
204
13
191
242
43
199
Exceeding the 24-hour and annual
12 12 0 81 11 70
standards
Exceeding the 24-hour standard only
0
0
0
39
31
8
Exceeding the annual standard only
192
1
191
122
1
121
Source: Prepared by the Congressional Research Service with data compiled from EPA’s websites for PM
designations at http://www.epa.gov/pmdesignations/ and http://www.epa.gov/oar/oaqps/greenbk/qnca.html.
Nonattainment counties are based on EPA’s final designations for the 2006 PM2.5 NAAQS for the 24-hour
standard published November 13, 2009, and the final area designations for the 1997 PM2.5 NAAQS for the 24-
hour and annual standards as of July 31, 2009.
Note: The counties in the table for the 2006 standards reflect EPA’s final designations for nonattainment area
boundaries for the 2006 24-hour only PM2.5 NAAQS based on 2006-2008 air quality monitoring data, overlaid
with the final designations for the annual standards (which were unchanged) for the 1997 PM2.5 NAAQS as of July
31, 2009.
The map in Figure 3, below, shows the overlap of the final nonattainment designations for the
annual and 24-hour standard under the 1997 PM2.5 NAAQS, with the final nonattainment areas
for the 24-hour standard as modified under the 2006 PM2.5 NAAQS.

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Figure 3. Counties 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 obtained from EPA. Nonattainment counties for the 24-hour standard are
based on EPA’s November 13, 2009, final designations for the 2006 PM2.5 NAAQS; nonattainment counties for the annual standard (which were
unchanged) are based on EPA’s final area designations for the 1997 PM2.5 NAAQS as of December 31, 2008. Partial counties are shown on the map
as whole counties.
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It is difficult to anticipate what effect the overlap of nonattainment designations 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.
Demonstrating Attainment with the 2006 PM2.5
NAAQS
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.
State Implementation Plans (SIPs)
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 effective date of designation unless an extension allowed under the CAA
is granted.35 As previously indicated, the effective date of the final designations rule is December
14, 2009 (30 days from the date of publication).
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. SIPS are

35 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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required to be submitted to EPA for review and approval, three years from the effective date of
the final designations. Several counties designated as nonattainment for the PM2.5 NAAQS are
designated for the first time. As noted earlier, a large portion of the nonattainment areas for the
2006 PM2.5 NAAQS designated by EPA November 2009, overlap with those areas designated
nonattainment for the 1997 PM2.5 NAAQS. However, as discussed in the previous section, these
areas are now unable to meet the 24-hour standard, whereas previously many of them 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)36 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.
EPA NAAQS Implementation Rules
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.37
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.38
The basic framework of the current implementation rule for the 1997 PM2.5 NAAQS provides
guidance for implementation of the 2006 standards. EPA plans to revise the regulatory text of the
implementation rule to change certain provisions that refer specifically to the 1997 PM2.5
standards to more generic language that would apply also to the 2006 standards, and to future
revisions of the PM2.5 NAAQS as well, but the agency has not released a specific schedule to
share for completing these revisions.39

36 71 Federal Register 6718, February 9, 2006.
37 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).
38 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.
39 Information provided to CRS by EPA’s Office of Air Quality and Planning, November 11, 2009.
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National Regulations
The EPA expects that in many cases implementing national strategies—including the 1999
visibility protection regulations (Regional Haze Rule);40 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),41 was vacated in a July 11, 2008, decision (North Carolina v.
EPA), by the U.S. Court of Appeals for the D.C. Circuit.42 On December 23, 2008, the court
reversed itself, allowing CAIR to remain in effect until a new rule is promulgated by EPA, noting
that vacating the old rule would defeat protection of the environmental values that the rule was
designed to preserve.43 The first phase of this rule is to take effect in 2009 and 2010, but only for
a temporary period. The court did not impose a specific deadline on EPA’s development of the
replacement rule, but emphasized that it was not granting an indefinite stay of its July 2008
decision. According to its Spring 2009 Semiannual Regulatory Agenda, published May 2009,
EPA announced its plans to propose a replacement rule for CAIR in early 2010 (March/April).44
EPA identified CAIR as a key component of states’ SIPs to attain the PM2.5 standard.
Implementation of CAIR would assist states in addressing the interstate transport (upwind state)
emission contributions in achieving attainment of the 1997 PM2.5 NAAQS.45 CAIR was a
principal means by which EPA projected that nonattainment areas in the eastern half of the
country would attain the ozone and fine particulate NAAQS, by mitigating interstate transport of
sulfur dioxide (SO2) and nitrogen oxide (NOx) emissions from electric generating units that
contribute to the formation of PM2.5.46 Without CAIR, most Eastern states would have a huge gap
in their emission control programs. What course EPA will take to develop an alternative to CAIR,
and the timeliness in which it will be achieved, likely raises more questions with respect to the
implementation of the 2006 revised PM2.5 NAAQS.
The D.C. Circuit, however, left the substantive requirements of its July 2008 decision fully intact.
That decision strongly suggests that there is no simple “fix” that would make CAIR acceptable to
the court. The court’s decision to vacate the rule was the subject of a July 29, 2008, congressional

40 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.
41 Promulgated under the CAA, 42 U.S.C. 7401 et seq., 70 Federal Register 25162, May 12, 2005.
42 531 F.3d 896 (D.C. Cir. 2008), 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 EPA Clean Air Interstate Rule website at
http://www.epa.gov/CAIR/index.html.
43 550 F.3d 1176 (D.C. Cir. 2008).
44 Spring 2009: EPA Semiannual Regulatory Agenda, p. 71, May 2009, http://www.epa.gov/lawsregs/search/
regagenda.html; see also 74 Federal Register 21992, May 11, 2009.
45 See CRS Report RL32431, Particulate Matter (PM2.5): Implementation of the 1997 National Ambient Air Quality
Standards (NAAQS), by Robert Esworthy.
46 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).
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hearing,47 and the implications of this decision are expected to be the topic of further deliberation
by Congress.
New Source Review
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.48
Transportation Conformity
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),49 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.50 The rules generally establish the criteria and
procedures for determining whether transportation plans, transportation improvement programs
(TIPs), or projects conform to a state’s SIP. On May 15, 2009, EPA published proposed
amendments to the transportation conformity rule that primarily affect implementation
conformity in PM2.5 and PM10 nonattainment and maintenance areas to account for the October
17, 2006, strengthening of the 24-hour PM2.5 air quality standard, and revoked the annual PM10
standard.51 The proposed rulemaking also addresses a court remand concerning hot-spot analyses
as they apply to PM2.5 and PM10, as well as carbon monoxide, nonattainment and maintenance
areas. EPA held a public hearing on June 4, 2009, and public comments were to be submitted by
June 29, 2009.

47 Senate Committee on Environment and Public Works, Subcommittee on Clean Air and Nuclear Safety, hearing,
“EPA’s Clean Air Interstate Rule (CAIR): Recent Court Decision and its Implications,” July 29, 2008,
http://epw.senate.gov/public/.
48 See Clean Air Act, Part D—Plan Requirements for Nonattainment Areas, sections 171-178, codified at 40 CFR
52.24(f)(10).
49 42 U.S.C. 7506(c).
50 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-
001, January 2008, http://www.epa.gov/otaq/stateresources/transconf/regs/420b08001.pdf.
51 74 Federal Register 23024, May 15, 2009; see also EPA’s “Transportation Conformity: Regulations” website at
http://www.epa.gov/otaq/stateresources/transconf/conf-regs.htm. The website provides access to all transportation
conformity regulations, including rulemakings currently in progress.
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Conclusions
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 increased the number of areas (typically defined by counties or portions of
counties) in nonattainment, and subsequently will potentially result in an encumbrance on states
to achieve compliance.
On November 13, 2009, EPA published its final designations of areas as nonattainment and
unclassifiable/attainment for the 2006 PM2.5 NAAQS. These area designations differed from
those areas EPA had included in its December 22, 2008, notifications to governors and tribal
leaders and from EPA’s August 2008 proposed modifications to nonattainment designation
recommendations submitted by states. Historically, there have been disagreements between EPA
and states, and other stakeholders, with regard to final NAAQS nonattainment designations, and
there may be challenges to the final designations for the 2006 PM2.5 NAAQS.
As a next step, following the publication of the final designations in the Federal Register, 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 designated by EPA in
November 2009 overlap with those areas previously designated nonattainment for 1997 PM2.5
NAAQS, these new designations are based on the 24-hour standard, whereas the majority of 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 are not required to submit SIPs until December 2012, and would not have to meet the PM2.5
standard until December 2014 (or 2019, if qualified for an extension52). 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. 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.
With regard to the 1997 PM2.5 NAAQS, states with nonattainment were required to be in
compliance by April 5, 2010, unless they are granted an extension. Implementation of the 1997
PM2.5 NAAQS, already delayed considerably, was 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 have vacated the Clean Air Interstate Rule (CAIR).53 Although the court modified its
decision on December 23, 2008,54 allowing CAIR to remain in effect until a new rule is
promulgated by EPA, many questions as to how to best restore CAIR remain. EPA’s development
of an alternative to CAIR in response to the court’s December 2008 decision raises more
questions with respect to the implementation of the 2006 revised PM2.5 NAAQS.

52 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.”
53 42 U.S.C. 7401 et seq.
54 550 F.3d 1176 (D.C. Cir. 2008).
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Concerns regarding looming key implementation milestones and attainment deadlines for the
2006 PM2.5 NAAQS, and associated 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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Appendix A. Comparative Timeline for
Implementing the 1997 and 2006 PM2.5 NAAQS
The timeline presented in Table A-1 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,55 and
the agency’s previous and current projected timelines for the 2006 PM2.5 NAAQS.
Table A-1. Schedule for Implementation of the 1997 and the 2006 PM2.5 NAAQS

2006 PM2.5 NAAQS
Milestones
1997 PM2.5 NAAQS
Previous Schedule
Current Schedule
Revised standard promulgated

July 18, 1997
October 10, 2006
October 10, 2006
Revised standard effective date

September 1997
December 18, 2006
December 18, 2006
State-tribal area designation recommendations

February 2004 (based
December 18, 2007
December 18, 2007
on 2000-2002
(based on 2004-2006
(based on 2004-2006
monitoring data)
monitoring data)
monitoring data)
EPA notifies states and tribes regarding modifications
June-July 2004
August 2008
August 2008
to their recommendations
EPA promulgates final area designations (required

January 5, 2005
December 22, 2008
November 13, 2009
one year after states and tribes make
(based on 2005-2007
(based on 2006-2008
recommendations)
monitoring data; never
monitoring data)
published)
EPA proposes PM2.5 implementation rule

November 1, 2005
NA
NA
Final Area designations effective date (typically not

April 5, 2005
April 2009 (delayed)
December 14, 2009
later than 90 days after Federal Register publication)
States with new transportation projects submit

April 5, 2006
December 22, 2009
December 14, 2010
conformity determination (required within one year
(delayed)
(projected)
of the effective date of nonattainment designation)
EPA promulgates final PM2.5 implementation rule

April 25, 2007
NA
NA
States and tribes submit revised implementation

April 2008 (ongoing)
April 2012 (delayed)
December 2012
plans (SIPs) (required three years after final area
(projected)
designations effective date unless extension granted)
NAAQS statutory compliance deadline for

April 2010-2015
April 2014-2019
December 2014-2019
attainment (required within five years after final area
(delayed)
(projected)
designations effective date; up to 10 years with
extension)
Source: Prepared by CRS based on EPA fact sheets and guidance documents, and relevant Federal Register
notices. For EPA’s previous timeline as of January 2009, see http://www.epa.gov/oar/particlepollution/
naaqsrev2006.html; for EPA’s more current timeline as of October 2009, see http://www.epa.gov/
pmdesignations/2006standards/documents/2009-10-08/timeline.htm.

55 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.
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Appendix B. Comparison of Final and Interim
Nonattainment Designation Areas for the 2006 PM2.5
NAAQS and the Final Nonattainment Designation
Areas for the 1997 PM2.5 NAAQS
Table B-1. Nonattainment Areas for the 2006 PM2.5 NAAQS as Identified by EPA in
the October 8, 2009, Final Designations and in the December 28, 2008, Status Table,
and Final Nonattainment Designations for the 1997 PM2.5 NAAQS
2006 PM2.5 NAAQS
1997 PM2.5 NAAQS
EPA Final
EPA Dec. 2008
EPA Final
EPA Final
Designations
Interim Designations
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

Shelby

Walker (p)
Walker (p)

Walker (p)
Chattanooga, AL-TN-GA

Jackson
(p)
ALASKA

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

Juneau, AK
Juneau
(p)

ARIZONA

Nogales, AZ
Santa Cruz (p)
Santa Cruz

CALIFORNIA

Chico, CA
Butte (p)
Butte (p)

Imperial County, CA
Imperial (p)
Imperial (p)

Los Angeles, CA
Los Angeles (p)
Los Angeles (p)
Los Angeles (p)
Los Angeles (p)
Orange
Orange
Orange
Orange

Riverside (p)
Riverside (p)
Riverside (p)
Riverside (p)

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

Placer (p)
Placer (p)

Sacramento
Sacramento

Solano (p)
Solano (p)

Yolo (p)
Yolo (p)

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2006 PM2.5 NAAQS
1997 PM2.5 NAAQS
EPA Final
EPA Dec. 2008
EPA Final
EPA Final
Designations
Interim Designations
Designations
Designations
24-Hour
24-Hour
24-Hour
Annual
Standard
Standard
Standard
Standard
State/Area Name
Counties and Partial Counties (p)
San Francisco Bay Area, CA
Alameda Alameda

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, CA
Sutter
Sutter

Yuba (p)
Yuba (p)

CONNECTICUT

New York, NY-NJ-CT
Fairfield Fairfield

Fairfield

New Haven
New Haven

New Haven
DELAWARE

Philadelphia- Wilmington,
New Castle
New Castle

New Castle
PA-NJ-DE
DISTRICT OF COLUMBIA

Washington, DC-MD-VA

Entire
District
GEORGIA

Atlanta, GA

Barrow

Bartow

Carroll

Cherokee
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2006 Fine Particulate Matter (PM2.5) NAAQS Nonattainment Designations

2006 PM2.5 NAAQS
1997 PM2.5 NAAQS
EPA Final
EPA Dec. 2008
EPA Final
EPA Final
Designations
Interim Designations
Designations
Designations
24-Hour
24-Hour
24-Hour
Annual
Standard
Standard
Standard
Standard
State/Area Name
Counties and Partial Counties (p)

Kendall (p)

Kendall (p)

Lake

Lake

McHenry

McHenry

Will

Will
Davenport-Moline-Rock Island,
Rock
Island

IA-IL
Paducah-Mayfield, KY-IL
Massac
(p)

St. Louis, MO-IL
Madison
Madison

Monroe

Monroe

Randolph (p)

Randolph (p)

St. Clair

St. Clair
INDIANA

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

Porter

Porter
Cincinnati-Hamilton, OH-KY-IN

Dearborn (p)

Dearborn (p)
Evansville, IN

Dubois

Gibson (p)

Gibson (p)

Pike (p)

Pike (p)

Spencer (p)

Spencer (p)

Vanderburgh

Vanderburgh

Warrick

Warrick
Indianapolis, IN
Hamilton
Hamilton

Hendricks

Hendricks

Johnson

Johnson

Marion

Marion

Morgan

Morgan
Lafayette-Frankfort, IN
Tippecanoe

Louisville, KY-IN
Clark Clark

Floyd

Floyd

Jefferson (p)

Jefferson (p)
Vincennes, IN
Knox
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2006 Fine Particulate Matter (PM2.5) NAAQS Nonattainment Designations

2006 PM2.5 NAAQS
1997 PM2.5 NAAQS
EPA Final
EPA Dec. 2008
EPA Final
EPA Final
Designations
Interim Designations
Designations
Designations
24-Hour
24-Hour
24-Hour
Annual
Standard
Standard
Standard
Standard
State/Area Name
Counties and Partial Counties (p)
Martinsburg, WV- Hagerstown,

Washington
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

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

New York, NY-NJ-CT
Bergen Bergen

Bergen
Essex
Essex

Essex
Hudson
Hudson

Hudson
Mercer
Mercer

Mercer
Middlesex
Middlesex

Middlesex
Monmouth
Monmouth

Monmouth
Morris
Morris

Morris

Passaic
Passaic Passaic

Somerset Somerset

Somerset
Union
Union

Union
Congressional Research Service
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2006 Fine Particulate Matter (PM2.5) NAAQS Nonattainment Designations

2006 PM2.5 NAAQS
1997 PM2.5 NAAQS
EPA Final
EPA Dec. 2008
EPA Final
EPA Final
Designations
Interim Designations
Designations
Designations
24-Hour
24-Hour
24-Hour
Annual
Standard
Standard
Standard
Standard
State/Area Name
Counties and Partial Counties (p)
Philadelphia- Wilmington,
Burlington Burlington

Burlington
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 Salem-

Davidson
High Point, NC

Guilford
OHIO

Canton-Massillon, OH
Stark Stark

Stark
Cincinnati-Hamilton, OH-KY-IN
Butler Butler

Clermont

Clermont

Hamilton

Hamilton

Warren

Warren
Cleveland-Akron- Lorain, OH

Ashtabula
(p)
Cuyahoga
Cuyahoga

Cuyahoga
Lake
Lake

Lake
Lorain
Lorain

Lorain
Medina
Medina

Medina
Portage
Portage

Portage
Summit
Summit

Summit
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2006 Fine Particulate Matter (PM2.5) NAAQS Nonattainment Designations

2006 PM2.5 NAAQS
1997 PM2.5 NAAQS
EPA Final
EPA Dec. 2008
EPA Final
EPA Final
Designations
Interim Designations
Designations
Designations
24-Hour
24-Hour
24-Hour
Annual
Standard
Standard
Standard
Standard
State/Area Name
Counties and Partial Counties (p)
Columbus, OH

Coshocton (p)

Coshocton (p)

Delaware

Delaware

Fairfield

Fairfield

Franklin

Franklin

Licking

Licking

Dayton-Springfield, OH
Clark Clark

Greene

Greene

Montgomery

Montgomery
Huntington-Ashland,WV-KY-OH

Adams (p)

Adams (p)

Gallia (p)

Gallia (p)

Lawrence

Lawrence

Scioto

Scioto
Parkersburg- Marietta, WV-OH
Washington
Washington
Steubenville- Weirton, OH-WV
Jefferson Jefferson

Jefferson
Wheeling, WV-OH

Belmont
Youngstown, OH
Mahoning

Trumbull

OREGON

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

Oakridge, OR
Lane (p)
Lane (p)

PENNSYLVANIA

Al entown, PA
Lehigh Lehigh

Northampton
Northampton

Harrisburg-Lebanon-Carlisle, PA
Cumberland Cumberland

a
Dauphin
Dauphin

Lebanon
Lebanon

York

Johnstown, PA
Cambria Cambria

Cambria

Indiana (p)
Indiana (p)

Indiana (p)
Lancaster, PA
Lancaster Lancaster

Lancaster
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2006 Fine Particulate Matter (PM2.5) NAAQS Nonattainment Designations

2006 PM2.5 NAAQS
1997 PM2.5 NAAQS
EPA Final
EPA Dec. 2008
EPA Final
EPA Final
Designations
Interim Designations
Designations
Designations
24-Hour
24-Hour
24-Hour
Annual
Standard
Standard
Standard
Standard
State/Area Name
Counties and Partial Counties (p)
Liberty-Clairton, PA
Allegheny (p)
Allegheny (p)

Allegheny (p)
Philadelphia-Wilmington,
Bucks Bucks

Bucks
PA-NJ-DE
Chester
Chester

Chester
Delaware
Delaware

Delaware
Montgomery
Montgomery

Montgomery
Philadelphia
Philadelphia

Philadelphia
Pittsburgh-Beaver Val ey, PA
Allegheny (p)
Allegheny (p)

Allegheny (p)

Armstrong (p)
Armstrong (p)

Armstrong (p)
Beaver
Beaver

Beaver
Butler
Butler

Butler

Greene (p)
Greene (p)

Greene (p)

Lawrence (p)
Lawrence (p)

Lawrence (p)
Washington
Washington

Washington
Westmoreland
Westmoreland

Westmoreland
Reading, PA
Berks Berks
York, PA
York York
TENNESSEE

Chattanooga, AL-TN-GA

Hamilton
Clarksville, TN-KY
Humphreys
(p)

Montgomery

Stewart
(p)

Knoxville-Sevierville- La Follette,
Anderson Anderson

Anderson
TN
Blount
Blount

Blount
Knox
Knox

Knox
Loudon
Loudon

Loudon

Roane (p)
Roane (p)

Roane (p)
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2006 Fine Particulate Matter (PM2.5) NAAQS Nonattainment Designations

2006 PM2.5 NAAQS
1997 PM2.5 NAAQS
EPA Final
EPA Dec. 2008
EPA Final
EPA Final
Designations
Interim Designations
Designations
Designations
24-Hour
24-Hour
24-Hour
Annual
Standard
Standard
Standard
Standard
State/Area Name
Counties and Partial Counties (p)
UTAH

Logan, UT-ID
Cache (p)
Cache (p)

Provo, UT
Utah (p)
Utah (p)

Salt Lake City, UT
Box Elder (p)
Box Elder (p)

Davis
Davis

Salt Lake
Salt Lake

Tooele (p)
Tooele (p)

Weber (p)
Weber (p)

VIRGINIA

Washington, DC-MD-VA

Alexandria
City

Arlington

Fairfax
City

Fairfax
Co

Fal s
Church
City

Loudoun

Manassas
City

Manassas Park City

Prince
William
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-Hagerstown,

Berkeley
MD
Morgantown, WV
Monongalia

Parkersburg- Marietta, WV-OH
Pleasants (p)

Pleasants (p)

Wood

Wood
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2006 Fine Particulate Matter (PM2.5) NAAQS Nonattainment Designations

2006 PM2.5 NAAQS
1997 PM2.5 NAAQS
EPA Final
EPA Dec. 2008
EPA Final
EPA Final
Designations
Interim Designations
Designations
Designations
24-Hour
24-Hour
24-Hour
Annual
Standard
Standard
Standard
Standard
State/Area Name
Counties and Partial Counties (p)
Steubenville- Weirton, OH-WV
Brooke Brooke

Brooke
Hancock
Hancock

Hancock
Wheeling, WV-OH

Marshall

Ohio
WISCONSIN

Green Bay, WI
Brown
Madison-Baraboo, WI
Columbia
(p)

Dane

Milwaukee-Racine, WI
Milwaukee Milwaukee

Racine
Racine

Waukesha
Waukesha

TOTALS

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

31 areas
58 areas
2 areas
38 areas

120 counties
211 counties
12 counties
204 counties

90 whole counties
154 whole counties
9 whole counties
173 whole counties

30 partial counties
57 partial counties
3 partial counties
31 partial counties
Source: Compiled by CRS using data from EPA PM designations websites. In some designated areas, EPA
included cities in the total count of whole and partial counties, with the exception of the District of Columbia.
a. In the August 25, 2008, Federal Register, EPA announced its determination that a three-county (Harrisburg,
Lebanon, Carlisle) Pennsylvania nonattainment area for the 1997 PM2.5 NAAQS was in attainment (73
Federal Register 49949, August 25, 2008). The determination was based on certified ambient air monitoring
data showing that the area monitored as in attainment for the 1997 PM2.5 NAAQS since the 2004-2006
monitoring period.
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2006 Fine Particulate Matter (PM2.5) NAAQS Nonattainment Designations

Appendix C. Tribal Lands—Designations for the
2006 PM2.5 NAAQS 24-Hour Standard
Table C-1. EPA’s October 8, 2009 Geographic Designations for 2006 PM NAAQS:
Tribes in 24-Hour PM2.5 Nonattainment Areas
State/Area Name
Tribes
CALIFORNIA

Chico, CA
Enterprise Rancheria of Maidu Indians of California

Mechoopda Indian Tribe of Chico Rancheria

Mooretown Rancheria of Maidu Indians of California
Los Angeles, CA
Cahuilla Band of Mission Indians of the Cahuilla Reservation

Morongo Band of Cahuilla Mission Indians of the Morongo Reservation

Pechanga Band of Luiseno Mission Indians of the Pechanga Reservation

Ramona Band or Village of Cahuilla Mission Indians of California

San Manuel Band of Serrano Mission Indians of the San Manuel Reservation

Soboba Band of Luiseno Mission Indians of the Soboba Reservation
Sacramento, CA
Shingle Springs Band of Miwok Indians, Shingle Springs Rancheria (Verona Tract)

United Auburn Indian Community of the Auburn Rancheria of California
San Francisco Bay Area, CA
Federated Indians of Graton Rancheria

Lytton Rancheria of California
San Joaquin Val ey, CA
Big Sandy Rancheria of Mono Indians of California

Santa Rosa Indian Community of the Santa Rosa Rancheria, California

Cold Springs Rancheria of Mono Indians of California

North Fork Rancheria of Mono Indians of California

Picayune Rancheria of Chukchansi Indians of California

Table Mountain Rancheria of California

Tule River Indian Tribe of the Tule River Reservation
WASHINGTON

Seattle-Tacoma, WA
Puyallup Tribe of the Puyallup Reservation, Washington
WISCONSINa

Milwaukee-Racine, WI
Forest County Potawatomi Tribe
Source: U.S. EPA, final designations as of October 8, 2009. Compiled by CRS using Tribal recommendations and
EPA responses, http://www.epa.gov/pmdesignations/2006standards/tribal.htm.
Note: The list of tribes is unofficial; official boundaries are specified in 40 CFR Part 81.
a. The Forest County Potawatomi Tribe was not included in EPA’s December 22, 2008 designations,
http://www.epa.gov/pmdesignations/2006standards/Dec08/tribal.htm. The December 22, 2008
designations included the Oneida Tribe of Wisconsin and the Ho-Chunk Nation of Wisconsin in the Green
Bay and Madison-Baraboo nonattainment areas respectively. These two areas were not designated
nonattainment in EPA’s November 13, 2009 final designations.
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2006 Fine Particulate Matter (PM2.5) NAAQS Nonattainment Designations

Appendix D. Map Depicting Counties in
Nonattainment for the 2006 PM2.5 NAAQS—
EPA’s Designation as of December 22, 2008
On December 22, 2008, EPA had identified 58 areas in 25 states, comprising 211 counties (154
counties and portions of 57 additional counties) for designation as nonattainment for the revised
2006 24-hour PM2.5 standard.56 These designations, based on air quality monitoring data for
calendar years 2005 through 2007, are indicated in the map below.
Figure D-1. Counties in Nonattainment for the 2006 PM2.5 NAAQS—
EPA’s Designations as of December 22, 2008,
(violating the 24-hour standard (35 μg/m3) only)

Source: Prepared by the Congressional Research Service based on EPA’s designations for the 2006 PM2.5
NAAQS as of December 22, 2008, with data obtained from EPA. See EPA’s website, “Area Designations for
2006 24-Hour Fine Particulate (PM2.5) Standards—December 2008 Area Status (Not Final Designations),”
http://www.epa.gov/pmdesignations/2006standards/documents/2008-12-22/12-08table.htm.

56 See EPA’s website, “Area Designations for 2006 24-Hour Fine Particulate (PM2.5) Standards—December 2008 Area
Status (Not Final Designations),” http://www.epa.gov/pmdesignations/2006standards/documents/2008-12-22/12-
08table.htm.
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2006 Fine Particulate Matter (PM2.5) NAAQS Nonattainment Designations

Author Contact Information

Robert Esworthy

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

Congressional Research Service
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