PM2.5/Clean Air Act: National Association of Manufacturers and other Industrial Groups File U.S. Supreme Court Petition for a Writ of Certiorari

The National Association of Manufacturers and 8 other industrial organizations filed a Petition for a Writ of Certiorari (“Petition”) before the United States Supreme Court (“Court”) challenging a 2024 United States Environmental Protection Agency (“EPA”) rule revisions the Clean Air Act National Ambient Air Quality Standards (“NAAQS”) for particulate matter. See Chamber of Commerce of the United States, et al., v. United States Environmental Protection Agency.

The other organizations joining the Petition include:

• Chamber of Commerce of the United States of America.
• American Cement Association.
• American Chemistry Council.
• American Forest & Paper Association.
• American Petroleum Institute.
• American Wood Council.
• National Mining Association.

(Collectively, “NAM”).

The Petition challenges the United States Court of Appeals for the District of Columbia Circuit (“D.C. Circuit”) June 26th Opinion in which it denied EPA and the industrial organizations argument that the agency’s revision of the PM2.5 NAAQS is based 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 D.C. Circuit denied EPA’s Motion for Vacatur and upheld the revised PM2.5 NAAQS.

Particulate matter is a generic term for a broad class of chemically and physically diverse substances that exist as discrete particles (liquid droplets or solids) over a wide range of sizes. It is composed of two major components.   

Larger particulates (PM10) are generally the result of mechanical, evaporative, and suspension processes. Particulates designated PM2.5 typically consist of sulfates, nitrates, elemental carbon, organic carbon, compounds or metals. Because of their small size, these particulates can remain in the air for a significant period of time. 

Sections 108 and 109 of the Clean Air Act require that EPA identify air pollutants utilizing certain criteria and set NAAQS for each. Particulates are one of the six air pollutants currently designated as criteria air pollutants and are therefore subject to NAAQS. Section 109 requires that EPA promulgate primary NAAQS for the pollutants identified under Section 108.

Section 109(d)(1) of the Clean Air Act mandates a periodic review of each NAAQS. Depending on the results of the review, EPA must determine whether the existing air quality criteria and NAAQS should be revised. EPA’s previous review and revision of the PM2.5 NAAQS is an example of this review process.

EPA had modified under the Biden Administration the PM2.5 to a more restrictive 9.0 µg/m3. The previous PM2.5 standard was 12.0 µg/m3.

EPA under the Trump Administration argues that the revised PM2.5 NAAQS is:

… 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.

A number of states also intervened supporting the EPA Motion and other states and environmental organizations opposed it.

The Petition filed by NAM states that two questions are presented which include:

1. Whether EPA may revise a NAAQS without the “thorough review” required by section 109(d)(1) simply because it acts “earlier or more frequently” than mandated.
2. Whether EPA must consider costs and attainability when exercising discretion to review and revise a NAAQS “earlier or more frequently” than mandated.

A copy of the Petition can be found here.