# 2025-24200: EPA Splits Philly Ozone Zone to Help Maryland and Delaware Breathe Easier 2025-24200, 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, is a Federal Register proposed rule from Environmental Protection Agency published 2026-01-02, effective 2026-02-02 (as of 2026-06-11). - Canonical: https://policyrisk.com/federal-register/2025-24200 - As of: 2026-06-11 - Plain-text twin of the page above; the HTML and this file carry the same facts. ## Facts - Document number: 2025-24200 - Title: 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 - Type: Proposed Rule - Agencies: Environmental Protection Agency - Citation: 91 FR 98 - Published: 2026-01-02 - Effective: 2026-02-02 - Comments close: not stated - Significant: no - Touches household money: no - Regulation identifier numbers: none - Last updated: 2026-06-11 ## In one line EPA Splits Philly Ozone Zone to Help Maryland and Delaware Breathe Easier ## Summary The EPA is proposing to split the big Philadelphia ozone pollution area into three smaller zones covering the same land, based on requests from Maryland and Delaware. This change affects Cecil County, MD, and New Castle County, DE, and includes new clean air data showing improvements. Comments on this plan are open until February 2, 2026, and the update helps local communities breathe easier without adding new costs right now. ## Abstract 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. ## Effects PRIA read - Philadelphia Ozone Area Split Into Three: benefit, medium. If you live in the Philadelphia-Wilmington-Atlantic City ozone area, the EPA proposes splitting that large area into three separate nonattainment areas: Cecil County, MD; New Castle County, DE; and a revised Philadelphia-Atlantic City PA-NJ area. The proposal keeps each area's current nonattainment… - Cecil County Clean Air Finding Suspends Plans: benefit, low. If you live in Cecil County, MD, the EPA proposes a clean data determination (CDD) showing the county's 2022-2024 ozone design value is 67 ppb and that the county is attaining the 2015 and 2008 ozone standards. If finalized, Maryland would be suspended from submitting certain attainment planning re… - New Castle County Clean Air Finding Suspends Plans: benefit, low. If you live in New Castle County, DE, the EPA proposes a clean data determination (CDD) showing the county's highest recent three-year ozone design value is 68 ppb and that the county is attaining the 2015 and 2008 ozone standards. If finalized, Delaware would be suspended from submitting certain a… - Requirement: Serious Area Plans Due Jan 1, 2026: cost, medium. For the 2015 ozone standard the Philadelphia nonattainment area is classified as Serious and each state in that area must provide a Serious nonattainment plan to EPA by January 1, 2026, showing how the area will come into attainment by the Serious-area attainment date of August 3, 2027. This applie… - Small Entities: No Significant Economic Impact: benefit, low. The EPA states this proposed action does not impose additional requirements and is certified as not having a significant economic impact on a substantial number of small entities under the Regulatory Flexibility Act. The agency also says the action does not impose an unfunded mandate or significant… ## Related documents - [2026-19071](https://policyrisk.com/federal-register/2026-19071): Partial Repeal of the Carbon Pollution Standards for Fossil Fuel-Fired Electric Generating Units, 2026-09-17 - [2026-19072](https://policyrisk.com/federal-register/2026-19072): Rescission of the Greenhouse Gas Findings for Fossil Fuel-Fired Power Plants and Repeal of Regulations for Power Plant Greenhouse Gas Emiss…, 2026-09-17 - [2026-18317](https://policyrisk.com/federal-register/2026-18317): Updated Definition of “Waters of the United States”, 2026-09-09 - [2026-14112](https://policyrisk.com/federal-register/2026-14112): Amendments and Nonconformance Penalties for Model Year 2027 and Later Heavy-Duty Highway Engines and Amendments to Inducement Provisions fo…, 2026-07-14 - [2026-13667](https://policyrisk.com/federal-register/2026-13667): Minor New Source Review Program Air Permitting Public Participation Requirements for State Implementation Plans, 2026-07-07 - [2026-13263](https://policyrisk.com/federal-register/2026-13263): Revisions To Establish the Sixth Unregulated Contaminant Monitoring Rule (UCMR 6) for Public Water Systems, 2026-07-01 ## Sources - [2025-24200 on federalregister.gov](https://www.federalregister.gov/documents/2026/01/02/2025-24200/proposed-revisions-of-the-nonattainment-designation-for-the-2008-and-2015-ozone-standards-and-clean) - [2025-24200 as published (PDF)](https://www.govinfo.gov/content/pkg/FR-2026-01-02/pdf/2025-24200.pdf) ## Related - [Previous: 2025-24154, Car Loan Interest Deduction](https://policyrisk.com/federal-register/2025-24154) - [Next: 2025-24210, Analog Telecommunications Relay Service Modernization](https://policyrisk.com/federal-register/2025-24210) - [All Federal Register documents](https://policyrisk.com/federal-register) Source: PRIA, https://policyrisk.com/federal-register/2025-24200 (as of 2026-06-11).