EPA To Reconsider Previous Administration's PM 2.5 NAAQS, Continuing Its Deregulatory Push

On March 12, 2025, EPA Administrator Zeldin announced that the agency, as one of its 31 historic deregulatory actions to advance President Trump's Day One executive orders and EPA's "Powering the Great American Comeback," will reconsider the previous administration's rule tightening the Particulate Matter National Ambient Air Quality Standards (PM2.5 NAAQS). The PM2.5 NAAQS rule has raised implementation concerns from various states across the country, including Louisiana, and has been the subject of litigation in the U.S. Court of Appeals for the District of Columbia Circuit (D.C. Circuit).

Final Rule Tightening PM2.5 NAAQS

On March 6, 2024, EPA issued a final rule tightening the PM2.5 NAAQS, which set the primary (health-based) annual NAAQS for PM2.5 at 9 micrograms per cubic meter (µg/m3), down from the prior limit of 12 µg/m3. See 89 Fed. Reg. 16202 (Mar. 6, 2024). EPA also laid out its timetable for states and the agency to implement the tightened standards,