Background
On February 7, 2024, the U.S. EPA lowered the primary annual PM2.5 NAAQS from 12.0 to 9.0 µg/m³. The revised standard was subsequently upheld by the D.C. Circuit on June 26, 2026, which rejected challenges from states and industry, as well as the U.S. EPA’s November 2025 motion to vacate the rule.
State and industry petitioners have since asked the U.S. Supreme Court to review that decision, and in a brief on October 2, 2026, the United States joined in urging the Court to take the case. Separately, the U.S. District Court for the Northern District of California ordered the U.S. EPA, on July 17, 2026, to finalize designations for all areas by February 6, 2027. The U.S. EPA appealed that order to the Ninth Circuit on September 2, 2026, and obtained expedited review but stated they intend to meet the deadline using 2023–2025 monitoring data.
Status of PM2.5 Designations in Texas
Governor Abbott’s February 6, 2025, initial designation letter urged the U.S. EPA to defer all designations and, alternatively, recommended attainment or attainment/unclassifiable for every county in Texas. In an October 2, 2026, letter to the Governor, the U.S. EPA Region 6 identified 14 Texas counties with monitors whose 2023–2025 design values may not meet the standard, those counties include: Atascosa, Bexar, Bowie, Cameron, Dallas, El Paso, Harris, Hidalgo, Jefferson, Montgomery, Nueces, Tarrant, Travis, and Webb. The U.S. EPA stated that these areas, along with nearby counties that contribute to them, could be designated nonattainment unless additional information, such as exceptional event demonstrations for wildfire smoke or evidence of monitor bias, supports attainment/unclassifiable or unclassifiable designations instead. The U.S. EPA requested that information by November 1, 2026, and has opened a public comment period in Docket EPA-HQ-OAR-2024-0078 that closes November 5, 2026.
What Does This Mean for Texas Industry
A nonattainment designation would bring Nonattainment New Source Review, including emission offsets and lowest achievable emission rate (LAER) requirements, for new and modified major sources of PM2.5 and its precursors, along with state planning and transportation conformity obligations. Trinity Consultants is tracking the designation process closely and will keep clients informed of any significant updates as they become available. If you would like to discuss how these decisions could affect your facility’s permitting plans, please contact your local Trinity Texas office.
