Client Alert: PM2.5 Air Quality Standard Remains at 9 µg/m³
/Background
The Biden Administration promulgated a rule in March 2024 reducing the annual National Ambient Air Quality Standard for PM2.5 from 12 µg/m³ to 9 µg/m³. Several states and other groups filed legal challenges to the new rule. The Biden EPA directed all state and local agencies to review all permit applications in progress met the new lower standard. This resulted in more onerous control and operational requirements on the permit applicants.
Court Ruling
After the second Trump Administration took office in 2025, the Trump EPA petitioned the Court of Appeals to vacate the new 9 µg/m³ standard and revert to the old 12 µg/m³ standard. On June 26, 2026, the Court of Appeals denied the Trump EPA's petition to vacate the 9 µg/m³ standard. This means that the new 9 µg/m³ standard remains in force.
What This Means for Your Organization
The immediate impact will be that companies applying for construction of major new facilities or expansion of existing facilities subject to New Source Review will continue to face the more onerous control and operational requirements. In the longer term, EPA and the states will be required to classify areas of the country exceeding the 9 µg/m³ standard as non-attainment areas where major new and expanded operations subject to New Source Review will be more costly or sometimes not feasible to permit.
KERAMIDA is monitoring this ruling and its implications closely.
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Questions about your air permitting obligations? KERAMIDA's environmental permitting team is here to help.
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