PM2.5/Clean Air Act: 105 Environmental Organizations Letter to EPA Proposing Motion for Vacatur of Revised NAAQS

105 groups and organizations (“EOs”) sent a December 16th letter to the United States Environmental Protection Agency (“EPA”) Administrator opposing the agency’s Motion for Vacatur (“Motion”) in the United States Court of Appeals for the D.C. Circuit in regard to pending challenges to the PM2.5 Clean Air Act National Ambient Air Quality Standard (“NAAQS”).

The EOs state in the December 16th letter that they are:

… gravely concerned by the Environmental Protection Agency’s (EPA) recent action abandoning its defense of national health-protection pollution standards for fine particulate matter (PM2.5 or soot).

EPA strengthened the PM2.5 NAAQS in 2024. The EOs argue that such strengthening was:

… in line with scientific, health-based evidence; consensus among experts that the existing standards were insufficiently protective; and the EPA’s statutory requirement to promulgate NAAQS that protect human health with a margin of safety.

They further argue that EPA has not disputed what they describe as the “overwhelming scientific evidence” supporting the NAAQS.

EPA in a November 24th Motion argued that in previously revising the PM2.5 NAAQS that it based its action on an erroneous interpretation of the Clean Air Act and exceeded its authority by revising the standard without initiating and completing a thorough review. The agency further argued that the result was:

… an unlawful tightening of the annual standard for fine particulate matter (PM2.5) from 12.0 µg/m³ to 9.0 µg/m³, without the rigorous, stepwise process that Congress required. EPA now confesses error and urges this Court to vacate the Rule before the area designation deadline of February 7, 2026.

The EOs ask that EPA “realign itself to its core mission and recommit itself to taking action that would truly protect human health and the environment.”

A copy of the letter can be found here.