Proposed Revisions of the Nonattainment Designation for the 2008 and 2015 Ozone Standards and Clean Data Determinations for the 2008 and 2015 Ozone Standards: Cecil County, MD and New Castle County, DE

ENVIRONMENTAL PROTECTION AGENCY <CFR>40 CFR Parts 52 and Part 81</CFR> <DEPDOC>[EPA-R03-OAR-2025-1872; FRL-12994-01-R3]</DEPDOC> <SUBJECT>Proposed Revisions of the Nonattainment Designation for the 2008 and 2015 Ozone Standards and Clean Data Determinations for the 2008 and 2015 Ozone Standards: Cecil County, MD and New Castle County, DE</SUBJECT> <HD SOURCE="HED">AGENCY:</HD> Environmental Protection Agency (EPA). <HD SOURCE="HED">ACTION:</HD> Proposed rule. <SUM> <HD SOURCE="HED">SUMMARY:</HD> The Environmental Protection Agency (EPA) is proposing to approve two separate requests from Maryland and Delaware to revise the designation for the Philadelphia-Wilmington-Atlantic City, PA-NJ-MD-DE nonattainment area (hereafter referred to as the Philadelphia nonattainment area) for the 2008 primary and secondary ozone national ambient air quality standards (NAAQS) and the 2015 primary and secondary ozone NAAQS. Due to the concurrent requests from Maryland and Delaware, the EPA is proposing to revise the existing Philadelphia nonattainment area boundary into three distinct nonattainment areas that together cover the identical geographic area of the existing area. The EPA is also proposing to issue clean data determinations (CDDs) for the revised Maryland and Delaware nonattainment areas for both the 2008 and 2015 ozone NAAQS. The EPA is taking this action pursuant to Clean Air Act (CAA) sections 107, 110, 172, and 182. </SUM> <EFFDATE> <HD SOURCE="HED">DATES:</HD> Written comments must be received on or before February 2, 2026. </EFFDATE> <HD SOURCE="HED">ADDRESSES:</HD> Submit your comments, identified by Docket ID No. EPA-R03-OAR-2025-1872 at <E T="03">www.regulations.gov,</E> or via email to <E T="03">gordon.mike@epa.gov.</E> For comments submitted at <E T="03">Regulations.gov,</E> follow the online instructions for submitting comments. Once submitted, comments cannot be edited or removed from <E T="03">Regulations.gov.</E> For either manner of submission, the EPA may publish any comment received to its public docket. Do not submit electronically any information you consider to be confidential business information (CBI) or other information whose disclosure is restricted by statute. Multimedia submissions (audio, video, etc.) must be accompanied by a written comment. The written comment is considered the official comment and should include discussion of all points you wish to make. The EPA will generally not consider comments or comment contents located outside of the primary submission ( <E T="03">i.e.,</E> on the web, cloud, or other file sharing system). For additional submission methods, please contact the person identified in the <E T="02">FOR FURTHER INFORMATION CONTACT</E> section. For the full EPA public comment policy, information about CBI or multimedia submissions, and general guidance on making effective comments, please visit <E T="03">www.epa.gov/dockets/commenting-epa-dockets.</E> <FURINF> <HD SOURCE="HED">FOR FURTHER INFORMATION CONTACT:</HD> Sarah McCabe, Planning & Implementation Branch (3AD30), Air & Radiation Division, U.S. Environmental Protection Agency, Region III, 1600 John F. Kennedy Boulevard, Philadelphia, Pennsylvania 19103. The telephone number is (215) 814-5786. Ms. McCabe can also be reached via electronic mail at <E T="03">mccabe.sarah@epa.gov.</E> </FURINF> <SUPLINF> <HD SOURCE="HED">SUPPLEMENTARY INFORMATION:</HD> On February 13, 2025, Maryland submitted a request to revise the Philadelphia nonattainment area into two separate nonattainment areas, covering the identical geographic area of the existing Philadelphia nonattainment area, and creating a smaller stand-alone nonattainment area for Cecil County, MD and a larger nonattainment area consisting of the remainder of the counties in the existing Philadelphia nonattainment area. On August 15, 2025, Delaware also submitted a request to revise the boundaries for the existing Philadelphia nonattainment area and create a stand-alone nonattainment area for New Castle County, DE. However, considering both requests, the EPA is proposing to act on these separate requests in the same notice to streamline the changes to the Philadelphia nonattainment area boundaries. Thus, the EPA is proposing to split the identical geographic area of the existing Philadelphia nonattainment area into three nonattainment areas: the Cecil County, MD nonattainment area, the New Castle County, DE nonattainment area, and the revised Philadelphia-Atlantic City, PA-NJ nonattainment area. These proposed revised designations are supported by an analysis of air quality data, emissions and emissions-related data, meteorology, geography/topography, and jurisdictional boundaries. If finalized, all areas would retain their current designation statuses and classifications for each respective ozone NAAQS. Additionally, if the revised designations and CDDs are finalized, the proposed CDDs would suspend the obligations of Maryland and Delaware to submit certain attainment planning requirements for their respective nonattainment areas for as long as each area continues to attain the 2008 and 2015 ozone NAAQS. Nonetheless, the EPA views each state's request as separable redesignation requests and may take separate final action on each request and adjust the area boundaries accordingly. <HD SOURCE="HD1">I. Background</HD> Under section 109 of the CAA, the EPA has established primary and secondary NAAQS for certain air pollutants (referred to as “criteria pollutants”) and conducts periodic reviews of the NAAQS to determine whether they should be revised or whether new NAAQS should be established. The primary NAAQS represent ambient air quality standards which the EPA has determined are necessary to protect the public health with an adequate margin of safety. The secondary NAAQS represent ambient air quality standards which the EPA has determined are requisite to protect the public welfare from any known or anticipated adverse effects associated with the presence of such air pollutant in the ambient air. Ground-level ozone is one such NAAQS. Ozone forms from complex chemical reactions in ambient air between nitrogen oxides (NO <E T="52">X</E> ) and volatile organic compounds (VOCs). Cars, trucks, buses, engines, industries, power plants and products such as solvents and paints are among the major manmade sources of ozone-forming emissions. Exposure to ozone can harm the respiratory system, aggravate asthma and other lung diseases, and is linked to premature death from respiratory causes. Following promulgation of a new or revised NAAQS, the EPA is required by section 107(d)(1) of the CAA to designate areas throughout the United States as attainment, nonattainment, or unclassifiable for the NAAQS. On March 27, 2008 (73 FR 16436), the EPA revised the 8-hour ozone NAAQS by lowering the level of the primary and secondary standards from 0.08 parts per million (ppm) to 0.075 ppm (75 parts per billion (ppb)) (40 CFR 50.15). The standards are based on the annual 4th highest daily maximum 8-hour average ozone concentration, averaged over three consecutive years. <SU>1</SU> <FTREF/> This average is referred to as the design value for each 3-year period. <SU>2</SU> <FTREF/> Only ozone measurement data collected in accordance with the quality assurance (QA) requirements using approved Federal Reference Method (FRM) or Federal Equivalent Method (FEM) monitors are used for NAAQS compliance determinations. <SU>3</SU> <FTREF/> The EPA uses FRM/FEM measurement data residing in the EPA's Air Quality System (AQS) database to calculate the ozone design values. On May 21, 2012 (77 FR 30088), the EPA designated the Philadelphia nonattainment area as nonattainment for the 2008 ozone NAAQS, based on air quality data from the 2008-2010 monitoring period that showed a design value of 83 ppb. <SU>4</SU> <FTREF/> Cecil County, MD and New Castle County, DE were included in the Philadelphia nonattainment area based on air quality data from the 2008-2010 monitoring period that showed design values of 80 ppb and 76 ppb for each county, respectively. <FTNT> <SU>1</SU>  See 40 CFR 50.15(b) and 50.19(b). </FTNT> <FTNT> <SU>2</SU>  The specific methodology for calculating the ozone design values, including computational formulas and data completeness requirements, is described in 40 CFR part 50, appendix U. </FTNT> <FTNT> <SU>3</SU>  The QA requirements for ozone monitoring data are specified in 40 CFR part 58, appendix A. The performance test requirements for candidate FEMs are provided in 40 CFR part 53, subpart B. </FTNT> <FTNT> <SU>4</SU>  The Philadelphia nonattainment area consists of the following counties: New Castle County in Delaware; Cecil County in Maryland; Atlantic County, Burlington County, Camden County, Cape May County, Cumberland County, Gloucester County, Mercer County, Ocean County, and Salem County in New Jersey; and Bucks County, Chester County, Delaware County, Montgomery County, and Philadelphia County in Pennsylvania. <E T="03">See</E> 40 CFR 81.308, 81.321, 81.331, and 81.339. </FTNT> At the time of designation, the Philadelphia nonattainment area was initially classified as Marginal with an attainment date of July 20, 2015, for the 2008 ozone NAAQS. On May 4, 2016, the EPA determined that the area qualified for a one-year attainment date extension to July 20, 2016 (81 FR 26697). On November 2, 2017, the EPA determined that the Philadelphia nonattainment area had attained the standard by its extended attainment date of July 20, 2016, effective December 4, 2017 (82 FR 50814). This determination was based on complete, certified, and quality assured ambient air quality monitoring data for the Philadelphia nonattainment area for the 2013-2015 monitoring period. The determination of attainment of the 2008 ozone NAAQS is not equivalent to a redesign ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Preview showing 10k of 42k characters. Full document text is stored and available for version comparison. ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━