On May 9, 2014, the United States Court of Appeals for the District of Columbia Circuit upheld the Environmental Protection Agency’s (EPA) 2012 final rule strengthening the primary national ambient air quality standard (NAAQS) for fine particulate matter (PM2.5) from 15 micrograms per cubic meter (ug/m3) to 12 ug/m3. Challengers argued that the new NAAQS is overly strict. The court disagreed, however, reasoning that the Clean Air Act “gives EPA substantial deference” in setting the NAAQS, and that EPA had reasonably explained how it weighed the evidence and how the evidence supported the new NAAQS.
Challengers can still petition the D.C. Circuit for rehearing, or appeal to the U.S. Supreme Court. For additional information, contact Andrew Holway.