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

Document 2026-11169 is a Final Rule published by the Environmental Protection Agency in the Federal Register on June 4, 2026, with an effective date of July 6, 2026. The Environmental Protection Agency (EPA) is approving two separate requests from Maryland and Delaware to revise the designation for the Philadelphia-Wilmington-Atlantic City, PA-NJ-MD-DE 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 revising the Philadelphia-Wilmington-Atlantic City, PA-NJ-MD-DE nonattainment area boundary into three distinct nonattainment areas that together cover the identical geographic area of the existing area. The EPA is also issuing 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. View the original at https://www.federalregister.gov/documents/2026/06/04/2026-11169/revisions-of-the-nonattainment-designation-for-the-2008-and-2015-ozone-standards-and-clean-data.

No. Document 2026-11169 is not classified as economically significant under Executive Order 12866. Economically significant rules require OIRA review and are estimated to have impacts of $100 million or more per year.