EPA seeks comment on plans for 2024 fine particle standard designations

WASHINGTON, Oct 6 — The U.S. Environmental Protection Agency (EPA) on Tuesday asked for public comment on its intended approach for designating areas of the country under the 2024 annual fine particle (PM2.5) air quality standard, according to a notice in the Federal Register.

EPA set the primary annual PM2.5 standard at 9.0 micrograms per cubic meter on Feb 7, 2024. Under the Clean Air Act, the agency must designate each area as attainment, nonattainment or unclassifiable after it sets a new or revised standard.

On July 17, 2026, the Northern District Court of California ordered EPA to publish final designations for all areas of the country no later than Feb 6, 2027, the notice said. EPA said it is appealing the order but is also moving forward to complete the designations.

EPA said it sent letters to states, the District of Columbia, territories and certain Tribes on or about Oct 2, 2026, telling them whether it intends to modify their initial designations. The letters asked states to provide additional information within 30 days of receipt.

Governors had to submit initial designations by Feb 7, 2025, and those submissions generally relied on 2021-2023 monitoring data, according to the notice. EPA said it intends to rely on design values from 2023-2025 for the final designations.

Where a state recommended "attainment" and EPA agrees, the agency intends to designate the area "attainment/unclassifiable." EPA said the statutory and regulatory burdens of the two labels are the same.

Comments must be received by Nov 5, 2026, under Docket ID No. EPA-HQ-OAR-2024-0078.