The Environmental Protection Agency (EPA) Administrator signed a proposal to strengthen the National Ambient Air Quality Standard (NAAQS) for particulate matter (PM) on June 14, 2012, intended to address potential health effects (including chronic respiratory disease and premature mortality) associated with short- and long-term exposure to particulate matter. The date of the proposal was per a June 6, 2012, order issued by the U.S. Court of Appeals for the District of Columbia Circuit in response to petitions filed by advocacy groups and 11 states. EPA's most recent statutorily required review and proposal has generated controversy and national debate among stakeholders, health and environmental advocacy groups, and states, as well as oversight in Congress, as did the previous changes leading up to the existing PM NAAQS promulgated October 2006, and those established in 1997. The proposed rule subsequently published in the Federal Register June 29, 2012, started a nine-week public comment period through August 31, 2012. EPA also held two public hearings for the proposal on July 17, 2012, in Philadelphia, PA, and July 19, 2012, in Sacramento, CA. Per the D.C. Circuit decision and as agreed to in a September 4, 2012, consent decree, EPA is to finalize its decision regarding the PM NAAQS by December 14, 2012. The June 2012 PM NAAQS proposal is the culmination of EPA's statutorily required review of the NAAQS under the Clean Air Act (CAA) based on studies available through mid-2009 and recommendations of EPA staff and a scientific advisory panel (Clean Air Scientific Advisory Committee, or CASAC ) established by the CAA. The agency initiated the review not long after the 2006 promulgation of the PM NAAQS. EPA staff reassessed scientific studies considered in setting the 2006 PM NAAQS revisions, reviewed and analyzed extensive subsequent research, and considered public comments and recommendations of the CASAC. Based on the scientific evidence considered, EPA Administrator Lisa P. Jackson signed the proposal that would tighten the current standard primarily by lowering the annual health-based ("primary") standard for fine particles smaller than 2.5 microns (PM 2.5 ). The proposal includes options for new secondary standards to address visibility impacts in urban areas associated with PM 2.5 , but would not modify the standards for inhalable coarse particles smaller than 10 microns or PM 10 . Because some farming and livestock practices contribute to particulate matter emissions, the agricultural community and some Members have maintained a particular interest in EPA's consideration of PM 10 and the potential impacts on agricultural operations. As per statutory scheduling requirements under the CAA, the final designation of areas (primarily counties) as nonattainment for any revised PM standards would not be determined until the end of 2014, and states would have until at least 2020 to achieve compliance. In its Regulatory Impact Analysis (RIA) accompanying the proposed rule assessing the costs and benefits of proposed revisions to the PM NAAQS, EPA estimated that strengthening the PM 2. 5 annual standard would add further similar health benefits anticipated with the promulgation of the 2006 PM NAAQS. Others have suggested that potential health benefits of tightening the PM NAAQS might be higher than EPA's estimates. On the other hand, tighter standards could impose additional compliance requirements on communities, states, industry, and others, at what some stakeholders and Members contend will be a substantial economic cost. EPA expects that requirements and emission reductions associated with existing and recently promulgated federal regulations under the CAA will significantly allay impacts of complying with the proposed revised PM standards, and anticipates that virtually all counties will meet the standards as proposed in 2020. Several recent and pending EPA regulations implementing the various pollution control statutes enacted by Congress have garnered vigorous oversight during the 112 th Congress. Members have expressed concerns, in hearings, through bipartisan letters commenting on proposed regulations, and through introduced legislation that would delay, limit, or prevent certain EPA actions. Particular attention is being paid to the CAA, under which EPA has moved forward with the first federal controls on emissions of greenhouse gases and also addressed emissions of conventional pollutants from a number of industries. Because of health and cost implications, NAAQS decisions historically have been the source of significant concern to some in Congress. The evolution and development of the PM NAAQS, in particular, have been the subject of extensive oversight. During the 112 th Congress, some Members expressed concerns in hearings, letters to the administrator, and proposed legislation in anticipation of potential changes to the PM NAAQS, and the June 2012 proposal is expected to generate further oversight. This CRS report summarizes EPA's June 2012 proposed changes to the PM NAAQS and includes comparisons with previous (1997) and current (2006) promulgated and proposed standards. Key actions leading up to the June 2012 proposal, and potential issues and concerns associated with the proposal to strengthen the PM 2.5 annual standard, are also highlighted. For more information regarding issues and implementation of the current PM 2.5 NAAQS promulgated in 2006, see CRS Report RL34762, The National Ambient Air Quality Standards (NAAQS) for Particulate Matter (PM): EPA's 2006 Revisions and Associated Issues , by [author name scrubbed], and CRS Report R40096, 2006 National Ambient Air Quality Standards (NAAQS) for Fine Particulate Matter (PM2.5): Designating Nonattainment Areas , by [author name scrubbed]. Particulate matter is one of six principal pollutants, commonly referred to as "criteria pollutants," for which EPA has promulgated NAAQS under the CAA. The others are ozone (O 3 , a key measure of smog), nitrogen dioxide (NO 2 , or, inclusively, nitrogen oxides, NOx), sulfur oxides (SOx, or, specifically, SO 2 ), carbon monoxide (CO), and lead (Pb). PM 2.5 can be emitted directly from vehicles, smokestacks, and fires but can also form in reactions in the atmosphere from gaseous precursors, including sulfur oxides, nitrogen oxides, and volatile organics occurring naturally or as emissions typically associated with gasoline and diesel engine exhaust, and from utility and other industrial processes. PM 10 (or coarse PM) is an indicator used in the NAAQS to provide protection from slightly larger (in the range of 2.5 to 10 microns or thoracic coarse particles), but still inhalable particles that penetrate into the trachea, bronchi, and deep lungs. These particles are generally associated with dust from paved and unpaved roads, certain industrial processes and agriculture, construction and demolition operations (including mining), and biomass burning. Establishing NAAQS does not directly limit emissions; rather, it represents the EPA Administrator's formal judgment regarding the level of ambient pollution that will protect public health with an " adequate margin of safety ." Under Sections 108-109 of the CAA, Congress mandated that EPA set national ambient (outdoor) air quality standards for pollutants whose emissions "may reasonably be anticipated to endanger public health (primary standards) or welfare (secondary standards)" and "the presence of which in the ambient air results from numerous or diverse mobile or stationary sources." The process for setting and revising NAAQS consists of the statutory steps incorporated in the CAA over a series of amendments. Several other steps have also been added by the EPA, by executive orders, and by subsequent regulatory reform enactments by the Congress. Section 109(d)(1)) of the CAA requires EPA to review the criteria that serve as the basis for the NAAQS for each covered pollutant every five years, to either reaffirm or modify previously established NAAQS. EPA has revised the PM NAAQS three times, in 1987, 1997, and most recently, October 2006, to ensure that the standards continue to provide adequate protection for public health and welfare. A February 24, 2009, decision by the U.S. Court of Appeals for the District of Columbia Circuit had remanded elements of EPA's decisions as promulgated in October 2006, in particular the decision not to tighten the primary annual NAAQS for PM 2.5 , to the agency for further consideration but did not vacate the revised standard nor set a specific timeline. The decision was in response to petitions filed in the D.C. Circuit by 13 states, industry, agriculture, business, and environmental and public health advocacy groups, challenging certain aspects of EPA's revisions for both PM 2.5 and PM 10 . The D.C. Circuit granted the petitions in part with regard to the PM 2.5 annual standard and the secondary standards for PM 2.5 and PM 10 (including visibility impairment), denying other challenges. Concerned with delays in EPA's schedule for proposing revisions to the 2006 PM NAAQS, the American Lung Association and the National Parks Conservation Association, and nine states separately filed petitions with the D.C. Circuit in November 2011 urging the court to order EPA's immediate compliance with the February 2009 remand. Subsequently, in February 2012 the two organizations sued EPA in the D.C. Circuit for failing to fulfill their statutory duty to review the October 2006 PM NAAQS within five years, and a coalition of 11 states filed a similar suit with the U.S. District Court Southern District of New York. In response, the D.C. Circuit initially directed EPA to complete its review of the PM NAAQS by June 7, 2012, and following a motion filed by the agency, amended the deadline to June 14, 2012. Promulgation of revised PM NAAQS will initiate a series of statutorily required actions, starting with EPA/States coordinated effort to designate areas (counties or portions of counties) with respect to attainment or nonattainment of any new primary standards three years following the effective date of published final revisions. Within three years of EPA's final designations of areas, states are required to submit plans (state implementations plans or SIPs) outlining how they will achieve or maintain compliance with the revised primary PM NAAQS. The CAA is not specific with respect to dates regarding when states must meet secondary PM standards. Relevant milestones are determined by EPA and states through the implementation planning process. EPA's 1997 revisions to the PM NAAQS revised the standards focused on particles smaller than 10 microns (PM 10 or coarse particles) established in 1987, and introduced standards for "fine" particles smaller than 2.5 microns (PM 2.5 ) for the first time. The current primary (health protection) PM NAAQS as revised in 2006 include an annual and a daily (24-hour) limit for PM 2.5 , but only a daily limit for PM 10 . To attain the PM 2.5 annual standard, the three-year average of the weighted annual arithmetic mean PM 2.5 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 percent of the time that a monitoring station can exceed the standard. For instance, a 98 th percentile 24-hour standard indicates that a monitoring station can exceed the standard 2% of the time during the year. For PM 2.5 and PM 10 , the secondary NAAQS, which are set at a level "requisite to protect the public welfare," are the same as the primary standards. As proposed June 2012, the PM 2.5 and PM 10 standards and other implementation changes would be as follows: Primary (Public Health) PM Standards PM 2.5 : strengthen the annual standard, which currently is 15 micrograms per cubic meter (µg/m 3 ), by setting a new limit of 12 µg/m 3 or 13 µg/m 3 ; retain the daily (24-hour) standard at 35 µg/m 3 based on the current three-year average of the 98 th percentile of 24-hour PM 2.5 concentrations as established in 2006. PM 10 : retain the current daily standard of no more than one exceedance of concentrations of 150 µg/m 3 per year on average over three years; there is no current annual standard for PM 10 (the previous annual maximum concentration standard of 50 µg/m 3 was eliminated by EPA in 2006). Secondary (Welfare) PM Standards PM 2.5 and PM 10 : secondary (welfare) NAAQS would be the same as the primary standards, the same correlations as the 2006 PM NAAQS, with the exception of visibility impairment associated with PM 2.5 . PM 2.5 Visibility Impairment : add a distinct secondary standard defined in terms of a PM 2.5 visibility index based on speciated PM 2.5 mass concentrations and relative humidity data to calculate light extinction on a deciview (dv) scale similar the current Regional Haze Program. Specifically, set a 24-hour averaging time of 30 or 28 deciviews (dv) based on a 90 th percentile form over three years. EPA is also seeking comment on alternative levels (down to 25 dv) and averaging times (e.g., 4 hours). Implementation Changes Monitoring : update several aspects of monitoring regulations including requiring relocating a small number of PM 2.5 monitors to be collocated with measurements of other criteria pollutants (e.g., nitrogen dioxide (NO 2 ) and carbon monoxide (CO)) near-roadway monitoring so to ensure these monitors are at one location in each urban area with a population of 1 million or more, and operational by January 1, 2015. Use data from existing Chemical Speciation Network or the EPA/National Park Service IMPROVE monitoring network to determine whether an area meets the proposed secondary visibility index standard PM 2.5 . No changes to PM 10 monitoring. Air Quality Index (AQI) : update the AQI (EPA's color-coded tool for informing the public how clean or polluted the air is and associated measures for reducing risks of exposure) for PM 2.5 by changing the upper end range for "Good" category (an index value of 50) on the overall scale (0 to 500 based on conversion of PM 2.5 concentrations) to the level of the proposed revised annual PM 2.5 standard. EPA would also set the 100 value of the index scale ("Moderate") at the level of the current 24-hour PM 2.5 standard, which is 35 µg/m, 3 and the AQI of 150 ("Unhealthy Sensitive Groups") would be set at 55 µg/m. 3 The current upper end for the "Hazardous" (500), "Unhealthy" (200) and "Very Unhealthy" (300) AQIs would be retained. Prevention of Significant Deterioration (PSD) : revise the PSD permitting program (rules) with respect to the proposed revised PM NAAQS so as not to "unreasonably delay" pending permits and establish a "grandfather" provision for permit applications if a draft permit or preliminary determination has been issued for public comment no later than the effective date of final revised PM NAAQS. This provision would not apply to NAAQS for other criteria pollutants and permits not meeting these criteria would have to demonstrate compliance with the revised standards once they are finalized. The final PM 2.5 daily standard established in 2006 was among the less stringent within the range of alternative levels recommended by EPA staff, and the annual standard is not as stringent as the standard recommended by the CASAC. The decision to retain the annual PM 2.5 standard was also less than recommended. Table 1 below shows the June 2012 proposed changes to the PM 2.5 annual standard in comparison to the annual and daily standards for 1997 and 2006 promulgated standards, and alternative levels recommended prior to the 2006 final revisions. The CAA as enacted, includes specific requirements for a multistage process to ensure the scientific integrity under which NAAQS are set, laying the groundwork for the Administrator's determination of the standard, and the procedural process for promulgating the standard. Primary NAAQS, as described in Section 109(b)(1), were to be "ambient air quality standards the attainment and maintenance of which in the judgment of the Administrator, based on such criteria and allowing an adequate margin of safety, are requisite to protect the public health." Based on this premise, the CAA specifies the criterion to be used by the Administrator in deciding on the final standard, including preparation of a "criteria document" that summarizes scientific information assessed. The act also requires the establishment and role of an independent advisory committee (CASAC ) to review EPA's supporting scientific documents, and the timeline for completing specific actions. EPA administratively added the preparation of a "staff paper" that summarizes the criteria document and lays out policy options. In addition, Executive Order 12866 requires a Regulatory Impact Analysis (RIA), although the economic impact analysis is essentially only for informational purposes and cannot be directly considered as part of the decision in determining the NAAQS. Beginning June 2007 with its general call for information, EPA initiated the current PM NAAQS review, which culminated in assessments of the scientific research and risk analyses, and ultimately the April 2011 publication of the staff's final Policy Assessment for the Review of the Particulate Matter National Ambient Air Quality Standards (or PM Policy Assessment) . The staff paper presented the staff conclusions and recommendations on the elements of the PM standard based on evaluation of the policy implications of the scientific evidence contained in the criteria document and the results of quantitative analyses (e.g., air quality analyses, human health risk assessments, and visibility analyses) of that evidence. Table B -1 in Appendix B provides a chronological listing of EPA's supporting documents leading up to the June 2012 proposed PM NAAQS. Supplemental to public comments solicited in the Federal Register , the CASAC reviewed EPA's drafts and final documents supporting the science and policy behind the Administrator's decisions in the June 2012 PM NAAQS proposal. The CASAC conducted meetings and consultations, and submitted written overviews, providing their views of the validity and completeness of the agency's assessments and findings, and recommending improvements. CASAC's final product, its review of EPA's second external review draft of the "PM Policy Assessment," was completed June 2010. Table B -2 in Appendix B provides a chronological summary of CASAC consultations and reviews of the supporting documents for the June 2012 proposal. Until discontinued by the CASAC Chairman in 2005, CASAC historically had signed off in the form of a "closure letter" only when the panel of members was convinced that each document accurately reflected the status of the science. The CASAC closure letter was an indication that the majority of the CASAC panel members had generally reached consensus that the criteria documents and the staff paper provided an adequate scientific basis for regulatory decision-making. The discontinuance of the closure letter was the subject of considerable debate, particularly within the science community. EPA revised certain aspects (not including reinstating the closure letter) of the CASAC review process most recently in May 2009. The April 2011 EPA staff paper concluded, and the CASAC panel concurred, that the scientific evidence supported modifying the PM 2.5 primary standard and considering options for revising the secondary standard for reducing visibility impairment associated with PM. Recognizing certain limitations of the data, a range of alternatives were presented for consideration by the Administrator for modifying the current PM NAAQS. These recommendations were the basis for the Administrator's decision, taking into account other factors including public comments received, for proposing to strengthen the annual PM 2.5 primary standard. The staff paper included possible modifications to strengthen certain aspects of the PM 10 standard. However, staff and CASAC placed considerable emphasis on continuing uncertainties and lack of sufficient data to initiate relevant quantitative risk assessment to support such modifications to the standard. As presented in the June 2012 Federal Register , the Administrator provisionally concluded that the growing evidence continues to support the appropriateness of the existing primary 24-hour PM 10 standard's protection of short-term health effects, and proposed to retain the existing PM 10 standard. A perennial issue in conducting NAAQS reviews is whether the agency is basing its decisions on those studies that reflect the latest science. In reviewing thousands of studies, the agency staff ultimately need to establish a cut-off date, or be faced with the need for a continuous review. The current review is based on studies completed by mid-2009, but in the June 29, 2012, Federal Register notice the EPA indicated that it is aware that a number of new scientific studies on the health effects of PM have been published since the mid-2009 cutoff date for inclusion in the Integrated Science Assessment. As in the last PM NAAQS review, the EPA intends to conduct a provisional review and assessment of any significant new studies published since the close of the Integrated Science Assessment, including studies that may be submitted during the public comment period on this proposed rule in order to ensure that, before making a final decision, the Administrator is fully aware of the new science that has developed since 2009. In this provisional assessment, the EPA will examine these new studies in light of the literature evaluated in the Integrated Science Assessment. This provisional assessment and a summary of the key conclusions will be placed in the rulemaking docket. Promulgation of NAAQS sets in motion a process under which the states and EPA first identify geographic nonattainment areas, those areas failing to comply with the NAAQS based on monitoring and analysis of relevant air quality data. The CAA is specific with regard to the timelines for determining areas in noncompliance, submission of plans for achieving (or maintaining) compliance, and when noncompliant areas must achieve the established or revised NAAQS. Within three years of issuance of a NAAQS, states are required to submit "infrastructure" plans demonstrating that they have the basic air quality management components necessary to implement the NAAQS. Following EPA's final designations of attainment and nonattainment areas, states (and tribes if they choose to do so) must submit their plans (State Implementation Plans, or SIPs) for how they will achieve and/or maintain attainment of the standards. These may include new or amended state regulations and new or modified permitting requirements. If new, or revised, SIPs for attainment establish or revise a transportation-related emissions allowance ("budget"), or add or delete transportation control measures (TCMs), they will trigger "conformity" determinations. Transportation conformity is required by the CAA, Section 176(c) (42 U.S.C. 7506(c)), 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. Areas designated nonattainment for the NAAQS 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. As discussed earlier (see " EPA's June 2012 Proposed Changes to the PM NAAQS "), the June 2012 PM NAAQS proposal would revise the PSD permitting program (rules) with respect to the proposed revised PM NAAQS so as not to "unreasonably delay" pending permits and establish a "grandfather" provision for permit applications if a draft permit or preliminary determination has been issued for public comment by the date the revised PM NAAQS go into effect. In addition to requiring states to submit implementation plans, EPA acts to control NAAQS pollutants through national regulatory programs. These may be in the form of regulations of products and activities that might emit the pollutants (particularly fuels and combustion engines, such as automobiles and trucks) and in the form of emission standards for new stationary sources (e.g., utilities, refineries). EPA anticipates that recent CAA rules, including rules to reduce pollution from power plants, clean diesel rules for vehicles, and rules to reduce pollution from stationary diesel engines, would help states meet the proposed revised PM NAAQS. The NAAQS designation process is intended as a cooperative federal-state-tribal 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" when they meet the standard or when the data are insufficient for determining compliance with the NAAQS. Following state and tribal recommended 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. EPA began developing methods for monitoring fine particles at the time the PM 2.5 NAAQS were being finalized in 1997, and operation of the network of monitors for PM 2.5 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. The amended monitoring requirements were intended to help federal, state, and local air quality agencies by adopting improvements in monitoring technology. EPA is proposing additional modifications to the PM NAAQS monitoring network as discussed earlier in this report. In addition to air emission and air quality data, EPA considers a number of other relevant factors in designating nonattainment area, 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. The June 2012 proposal to tighten the PM 2.5 annual standard is expected to result in an increase in the number of areas (typically defined by counties or portions of counties) designated nonattainment. Similar to the strengthening of the PM 2.5 daily (24-hour) standard in 2006, the June 2012 proposed range of concentrations for the PM 2.5 annual standard is expected to affect primarily areas currently in nonattainment for the existing (2006) standards, but would also likely include a few counties that have not been previously designated as nonattainment. EPA would not require new nonattainment designations for PM 10 primary NAAQS since the June 2012 proposal would retain the existing (2006) standards. Assuming EPA promulgates final PM NAAQS revisions by December 14, 2012, as indicated earlier in this report, state and tribal area designation recommendations would be required under the CAA to be submitted to EPA by December 2013 (within one year of the final rule). The CAA requires EPA to make its final area designations within one year of the state and tribal recommendations, projected to be December 2014. EPA is required to notify states and tribes of its intended modifications to their recommendations 120 days (projected to be August 2014) prior to promulgating final designations which are expected to become effective sometime in early 2015. The actual area designations of nonattainment are more than two years away and will be based on more current monitoring data (likely 2011-2013) and other factors. However, EPA identified counties with monitors that show concentrations of PM 2.5 that would exceed the proposed revised range of the primary annual standard of 12 µg/m 3 to 13 µg/m 3 based on 2008-2010 monitoring data. The map in Figure 1 below depicts these areas for the two proposed revised PM 2.5 annual standards. The areas are depicted in the map for illustration purposes as a rough approximation of the potential areas that may be designated nonattainment for the June 2012 proposed standards. The specific counties based on the 2008-2010 data are shown in Appendix C . The map below shows the overlap of those nonattainment areas for the existing (2006) PM 2.5 annual and/or daily (24-hour), as well as additional areas not previously designated nonattainment. Although a direct comparison of areas expected to be designated nonattainment for the June 2012 proposed PM 2.5 standards with those areas designated nonattainment for the existing (2006) PM NAAQS is not available, overlaying those counties with monitors based on 2008-2010 monitoring provides some indication of potential areas. The 2006 revised PM NAAQS, which are currently being implemented, primarily affect urban areas. EPA published its final 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 PM 2.5 standard, on November 13, 2009. The designations, based on 2006 through 2008 air quality monitoring data, included a few counties that were designated nonattainment for PM 2.5 for the first time, but the majority of the counties identified overlapped with EPA's final nonattainment designations for the 1997 PM 2.5 NAAQS. It is important to note that most of the 1997 PM 2.5 nonattainment areas were only exceeding the annual standard; thus, tightening 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 standard. The majority of the roughly 3,000 counties throughout the United States (including tribal lands) were designated attainment/unclassifiable, and are not required to impose additional emission control measures to reduce PM 2.5 . Based on anticipated reductions associated with several other existing national air pollution control regulations and programs (see discussion in " National Regulations " section), EPA predicted that only a few counties would not be in compliance with the proposed primary standards by 2020: two counties in California are projected to not meet the proposed annual standard of 13 µg/m; 3 an additional four counties in Alabama, Arizona, Michigan, and Montana would not meet the proposed option of 12 µg/m 3 for the annual standard. Under the CAA, within three years of issuance of a NAAQS, all states are required to submit "infrastructure" plans demonstrating that they have the basic air quality management components necessary to implement the NAAQS. 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 ultimately designated nonattainment, state, local, and tribal governments must outline detailed control requirements in plans demonstrating how they will meet the revised primary annual PM 2.5 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 the agency's final designations. EPA projects final area designations will be effective early 2015 for the June 2012 proposed revisions, thus SIPs and TIPs would be required by early 2018. If states fail to develop an adequate implementation plan, EPA can impose one. Under the CAA, states are required to meet any established or revised PM 2.5 standard "as expeditiously as practicable," but no later than five years from the effective date of designation—December 2020 according to EPA's timeline—unless an extension (up to five additional years) allowed under the CAA is granted. EPA anticipates that in many cases, stationary and mobile source controls and additional reductions currently being adopted to attain existing (2006) PM 2.5 standards in conjunction with expected emission reductions from implementing national regulations and strategies will help states meet the proposed standards. These national actions include the Cross-State Air Pollution Rule (CSAPR); Mercury and Air Toxics Standards (MATS); Light-Duty Vehicle Tier 2 Rule; Heavy Duty Diesel Rule; Clean Air Nonroad Diesel Rule; Regional Haze Regulations and Guidelines for Best Available Retrofit Technology Determinations; NOx Emission Standard for New Commercial Aircraft Engines; Emissions Standards for Locomotives and Marine Compression-Ignition Engines; Emission Standards Ignition Engines, Control of Emissions for Nonroad Spark Ignition Engines and Equipment; Category 3 Oceangoing Vessels; Reciprocating Internal Combustion Engines (RICE) National Emissions Standards for Hazardous Air Pollutants (NESHAPS); and New Source Performance Standards and Emissions Guidelines for Hospital/Medical/Infectious Waste Incinerators Final Rule Amendments. Stakeholders and some Members of Congress are skeptical about EPA's expectations with respect to the corollary benefits associated with some of these regulations, and raise concerns about pending efforts to delay some of the more recent programs and historical delays of others. Of particular concern are the Cross-State Air Pollution Rule ("Cross-State Rule" or CSAPR), which was to have gone into effect in 2012 but was stayed in December 2011, then vacated on August 21, 2012, by the D.C. Circuit Court of Appeals, and the Mercury and Air Toxics Standards (MATS), which EPA itself has stayed pending reconsideration. On October 5, 2012, the U.S. Department of Justice filed a petition seeking en banc rehearing of the D.C. Circuit's August 21, 2012, decision regarding the CSAPR. Other remanded rules include the hazardous air pollutant ("MACT") standards for boilers and cement kilns. EPA has delayed implementation of the boiler MACT rules for more than a year and a half while considering changes to the requirements. The agency has also extended the compliance deadline for the cement kiln MACT by two years. Estimates of health and welfare risk reductions and control strategies for areas potentially not in compliance provide some insights into potential impacts of the June 2012 proposed PM NAAQS. The Clean Air Act requires that NAAQS be set solely on the basis of public health and welfare protection, while costs and feasibility are generally taken into account in implementation of the NAAQS (a process that is primarily a state responsibility). As discussed previously, in setting and revising the NAAQS, the CAA directs the EPA Administrator to protect public health with an adequate margin of safety . This language has been interpreted, both by the agency and by the courts, as requiring standards be based on a review of the health impacts, without consideration of the costs, technological feasibility, or other non-health criteria. Nevertheless, coinciding with the PM NAAQS proposed rule in the June 29, 2012, Federal Register , EPA released a regulatory impact analysis (RIA) assessing the costs and benefits of setting the standard at the proposed and other alternative levels, to meet its obligations under Executive Order 12866 and in compliance with guidance from the White House Office of Management and Budget. EPA emphasized that the RIA is for informational purposes and that the proposed decisions regarding revisions to the PM NAAQS presented in the June 2012 proposed rulemaking are not based on consideration of the analyses in the RIA in any way. Table 2 below presents a range of EPA's estimated economic costs, monetized benefits, and net benefits (subtracting total costs from the monetized benefits) associated with achieving the June 2012 proposal, and other alternatives considered. As shown in the table, estimated benefits are expected to be at least 30 times greater than the costs of $69 million for the most stringent option included in the June 2012 proposal. EPA also notes that a full accounting of benefits would include additional environmental and societal benefits that were not quantified in the analysis. The basis for the benefits calculations are health and welfare impacts attributable to reductions in ambient concentration emissions of PM 2.5 resulting from a reasonable, but "speculative," array of known state implementation emission control strategies selected by EPA for purposes of analysis. The analysis does not model the specific actions that each state will undertake or emerging technologies in implementing the alternative PM 2.5 NAAQS. EPA notes that mortality co-benefits represent a substantial proportion of total monetized benefits (over 98%). The EPA estimated total costs under partial and full attainment of several alternative PM standards. The engineering costs generally include the costs of purchasing, installing, and operating the referenced control technologies. The technologies and control strategies selected for analysis are illustrative of one way in which nonattainment areas could meet a revised standard. EPA anticipates that in actual SIPS, state and local governments will consider programs that are best suited for local conditions as there are various options for potential control programs that would bring areas into attainment with alternative standards. EPA includes a detailed discussion of the limitations and uncertainties associated with the benefits assumptions and analyses. While recognizing the need to adequately protect against potential health concerns associated with PM, some Members and stakeholders are also apprehensive that EPA has underestimated potential costs and are concerned with the potential monetary consequences associated given the current economic environment. In particular, some stakeholders question the validity of EPA's reliance on the associated impacts of other national regulations in reducing the potential burdens. Critics are concerned that this results in underestimating the number of areas (counties) likely to be affected in terms of their ability to attain the proposed alternative PM NAAQS and the expected associated costs of necessary measures that will be required to in the form of SIPs. Prior to the EPA's June 2012 proposed rule to revise the PM NAAQS, stakeholders were providing evidence and arguments in letters, press releases, at public hearings and other forums for their preferred recommendations, and EPA received numerous comments during various stages of development of the criteria and policy documents. In general, business and industry opposed more stringent standards particularly in light of the current national and global economic environment; and public health and environmental advocacy groups advocated support for more stringent standards based on the continuing evidence of health effects from ongoing scientific research. As mentioned earlier, several states petitioned EPA, and subsequently filed suit in the D.C. Circuit Court urging timely completion of its review of the PM NAAQS in response to the February 2009 remand. Other state air quality regulators recognized the need to ensure adequate health protection from PM, but expressed concerns about the impacts of more stringent PM NAAQS on already strained state budgets. Proponents of more stringent standards generally assert— the PM 2.5 standards should be at least as stringent as the more stringent combined daily and annual levels recommended in the 2006 EPA staff paper, and those recommended by the CASAC; scientific evidence of adverse health effects is more compelling than when the standards were revised in 2006; more stringent standards ensure continued progress toward protection of public health with an adequate margin of safety as required by the CAA; welfare effects, particularly visibility, should be enhanced. Critics of more stringent PM NAAQS contend— more stringent (and in some cases the existing) standards are not justified by the scientific evidence; the proposal does not take into account studies completed since the 2009 cut-off; requiring the same level of stringency for all fine particles without distinguishing sources is unfounded; costs and adverse impacts on regions and sectors of the economy are excessive; revising the standards could impede implementation of the existing (2006) PM NAAQS and the process of bringing areas into compliance, given the current status of this process; the benefits (and costs) associated with implementation of the 2006 PM NAAQS, as well as compliance with other relatively recent EPA air quality regulations, have not yet been realized, pointing out that based on EPA's trends data that annual and 24-hour measured PM national concentrations have declined 24% and 28% respectively from 2001 to 2010. EPA has responded to both sides by emphasizing that the agency's conclusions and Administrator's decisions are provisional in nature, and the agency is soliciting comment (60-day comment period from the date of publication in the Federal Register ) regarding its supporting analysis and a variety of alternative PM NAAQS. In addition to written comments, EPA will also compile information presented at the July 2012 public hearings held in Philadelphia and Sacramento. EPA also declared its intention to review and evaluate significant new studies developed and published since the close of the criteria document. Not long after EPA's release of its PM NAAQS proposal, the House Committee on Energy and Commerce Subcommittee on Energy and Power held a hearing on June 28, 2012, on the potential impacts of tightening the PM 2.5 NAAQS. The focus of the debate was the regulatory costs and burdens associated with the implementation of the revised standards, and potential impacts on economic growth, employment and consumers. Just prior to EPA's release of the proposal, several Members urged the Administrator to include retaining the PM 2.5 standard as an option for consideration in the agency's proposal. During the second session of the 111 th and during the first session of the 112 th Congress, some Members raised concerns in letters to the EPA Administrator and during oversight hearings, about EPA's staff draft reports, and CASAC recommendations leading up to the June 2012 proposal, and the potential impacts that tightening the PM 10 NAAQS standards could have on the agricultural industry. Many Members encouraged EPA to retain the current PM 10 NAAQS standards. A general provision was also included in FY2012 House-reported EPA appropriations language ( H.R. 2584 , Title IV, Section 454) that would have restricted the use of FY2012 appropriations "to modify the national primary ambient air quality standard or the national secondary ambient air quality standard applicable to coarse particulate matter (generally referred to as "PM 10 ")." No comparable provision was retained in the Consolidated Appropriations Act, 2012 ( P.L. 112-74 ), enacted December 23, 2011, which ultimately included EPA's FY2012 appropriation. Although EPA proposed to retain the PM 10 , some stakeholders and Members remain skeptical that the final revised NAAQS could be changed from the proposal. Congress continues to consider legislation that would delay EPA regulatory action with respect to revising the PM 10 NAAQS, including the House-passed Farm Dust Regulation Prevention Act of 2011 ( H.R. 1633 ), which awaits action in the Senate. NAAQS decisions have often been a source of significant concern to many in Congress. The evolution and development of the PM (and ozone) NAAQS, in particular, have been the subject of extensive oversight. For example, following promulgations of the 1997 NAAQS Congress held 28 days of hearings on the EPA rule. Congress enacted legislation specifying deadlines for implementation of the 1997 standard, funding for monitoring and research of potential health effects, and the coordination of the PM (and ozone) standard with other air quality regulations. During the 109 th Congress, hearings were held regarding implementation and review of the PM NAAQS leading up to promulgations of the 2006 PM NAAQS. Because of the potential impacts PM NAAQS could have on both public health and the economy, EPA's current reassessment and June 2012 proposed modifications of these standards will likely be of continued interest to Congress. EPA's proposal to modify the existing PM NAAQS published June 29, 2012, following completion of its statutorily required review, has sparked interest and conflicting concerns among a diverse array of stakeholders, and in Congress. As evidenced by the history of the PM NAAQS, the level of scrutiny and oversight will likely increase as the agency proceeds toward its final decision regarding the PM NAAQS by December 2012. Because both the health and economic consequences of particulate matter standards are so potentially significant, the PM NAAQS are likely to remain a prominent issue of interest during the remainder of the 112 th Congress. While analyses indicate more stringent PM NAAQS could result in fewer adverse health effects for the general population and particularly sensitive populations such as children, asthmatics, and the elderly, as well as improved welfare effects, concerns remain with regard to the associated costs. In its assessment of the impacts of tightening the PM NAAQS as proposed, EPA expects few additional areas will be in nonattainment and require more stringent pollution controls to achieve compliance. Industry, some Members and some state representatives anticipate that the proposed tighter PM NAAQS will likely result in more areas classified as nonattainment and needing to implement new controls on particulate matter. Further, they are concerned that stricter standards may mean more costs for the transportation and industrial sectors, including utilities, refineries, and the trucking industry, impacted by particulate matter controls. The EPA's review and establishment of the 1997 PM NAAQS was the subject of litigation and challenges, including a Supreme Court decision in 2001. EPA's 1997 promulgation of standards for both coarse and fine particulate matter prompted critics to charge EPA with over-regulation and spurred environmental groups to claim that EPA had not gone far enough. Not only was the science behind the PM NAAQS challenged, but EPA was also accused of unconstitutional behavior. More than 100 plaintiffs sued to overturn the standard. Although EPA's decision to issue the standards was upheld unanimously by the Supreme Court, for the most part, stakeholders on both sides of the issue continued to advocate their recommendations for more stringent and less stringent (in some cases no) PM standard. Several states and industry, agriculture, business, and environmental and public health advocacy groups petitioned the U.S. Court of Appeals for the District of Columbia Circuit, challenging certain aspects of EPA's revisions of the PM NAAQS as promulgated December 2006. A February 24, 2009, decision by the D.C. Circuit granted the petitions in part, denying other challenges, and remanded the standards to EPA for further consideration. The court did not specifically vacate the 2006 PM NAAQS and implementation is currently underway. The final form of the current efforts to revise PM NAAQS may not be known for some time. EPA will likely receive considerable comments in response to the June 2012 proposal. It would not be surprising if interested stakeholders return to the courts or initiate challenges after the agency completes its review and promulgates final standards in December 2012, thus potentially furthering delays in designating nonattainment areas, and states' development and implementation of SIPs. Appendix A. Chronological Summary of Key Milestones Subsequent to the June 2012 PM NAAQS Proposal As part of the D.C. Circuit's decision and a related Consent Agreement, EPA has agreed to issue final revised PM NAAQS by December 14, 2012. The timeline presented in Table A -1 below reflects the most recent projected milestone dates subsequent to the PM NAAQS proposed rule published June 29, 2012. These milestones are driven primarily by statutory requirements under the CAA, and are based on milestones identified in the June 29, 2012, Federal Register and accompanying EPA fact sheets. The CAA does not specify a timeframe with regard to when states must meet secondary PM standards; relevant milestones are determined by EPA and states through the implementation planning process. Appendix B. Supporting EPA Scientific and Policy Documents, and CASAC Review Appendix C. Comparison of Potential Nonattainment Areas for the June 2012 Proposed PM 2.5 Annual Standard with the Final Designations for the 2006 and 1997 PM 2.5 NAAQS

Summary: On June 29, 2012, the Environmental Protection Agency (EPA) published a proposal to revise the National Ambient Air Quality Standard (NAAQS) under the Clean Air Act (CAA) for particulate matter (PM), in response to a June 6, 2012, order issued by the U.S. Court of Appeals for the District of Columbia Circuit. Environmental and public health advocacy groups and 11 states had petitioned the agency, and subsequently filed suit in the D.C. Circuit alleging that EPA failed to perform its mandated duty to complete the review of the PM NAAQS within the statutory deadline. EPA has agreed to issue final revised PM NAAQS by December 14, 2012. EPA's review of the PM NAAQS has generated considerable debate and oversight in Congress. The June 2012 proposal would strengthen the existing (2006) annual health-based ("primary") standard for "fine" particulate matter 2.5 micrometers or less in diameter (or PM2.5), lowering the allowable average concentration of PM2.5 in the air from the current level of 15 micrograms per cubic meter (µg/m3), to a range of 12 to 13 µg/m.3 The annual PM2.5 NAAQS is set so as to address human health effects from chronic exposures to the pollutants. The existing 24-hour primary standard for PM2.5 that was reduced from 65 µg/m3 to 35 µg/m3 in 2006 would be retained, as would the existing standards for larger, but still inhalable "coarse" particles less than 10 micrometers in diameter or PM10. "Secondary" standards that provide protection against "welfare" (non-health) effects, such as ecological effects and material deterioration, would be identical to the primary standards the same as in 2006, but the June 2012 proposal included two options for a 24-hour PM2.5 standard to improve visibility. In developing the June 2012 proposal, EPA reviewed scientific studies available since the agency's previous review in 2006. EPA determined, and the independent scientific advisory committee mandated under the CAA (Clean Air Scientific Advisory Committee, or CASAC) concurred, that evidence continues to show associations between particulates in ambient air and numerous significant health problems, including aggravated asthma, chronic bronchitis, non-fatal heart attacks, and premature death. Populations shown to be most at risk include children, older adults, and those with heart and lung disease, and those of lower socioeconomic status. EPA expects that the potential benefits of the proposed revisions would range from an estimated low of $88.0 million to a high of $5.9 billion dependent on the concentration level and other factors, and estimated costs would range from $2.9 million to $69.0 million. Some stakeholders and some Members express concerns that the cost impacts will be more significant than EPA estimated in those areas unable to comply with the new standards. EPA's establishment of or revisions to the PM NAAQS do not directly regulate emissions from specific sources, or compel installation of any pollution control equipment or measures, but indirectly could affect operations at industrial facilities and other sources throughout the United States. Final revised PM NAAQS will start a process that includes a determination of areas in each state that exceed the standard and must, therefore, reduce pollutant concentrations to achieve it. Following the determination of "nonattainment" areas (primarily counties) based on multiple years of monitoring data and other factors submitted by the states, state and local governments must develop (or revise) State Implementation Plans (SIPs) outlining measures to attain the standard. These often involve promulgation of new regulations by states, leading to the issuance of revised air permits. The process typically takes several years. Based on statutory scheduling requirements, designation of areas as nonattainment for any revised PM NAAQS would not be determined until the end of 2014, and states would have until at least 2020 to achieve compliance.