A federal appeals court
ruled Jan. 4, 2012 that U.S. EPA must re-do two final rules that
specify how states implement EPA’s National Ambient Air Quality
Standards (NAAQS) for fine particulate matter (PM 2.5).
The three-judge panel of the U.S. Court of Appeals for the District
of Columbia Circuit rejected EPA's argument that it is required
under the Clean Air Act to use a less stringent implementation regime
for fine particulates than it is for more coarse particulate matter
The ruling means EPA must look again at the implementation of the
existing standards. Separately, the EPA announced Dec. 14, 2012
that it was finalizing an revision to its National Ambient Air Quality
Standard (NAAQS) for fine particulate matter (PM2.5), setting the
annual primary standard at 12 micrograms per cubic meter. EPA also
announced that it was retaining the existing secondary standard
The Natural Resources Defense Council, Sierra Club, American Lung
Association and Medical Advocates for Healthy Air challenged two
final rules, promulgated pursuant to the Clean Air Act (CAA, Act),
which govern implementation of the national ambient air quality
standard (NAAQS) for "fine" particulate matter -- particulate
matter (PM) having a diameter equal to or less than 2.5 micrometers
(PM2.5). The rules at issue are the PM2.5 Implemention Rule (72
Fed. Reg. 20,586, 2007) and the PM2.5 NSR Implementation Rule (73
Fed. Reg. 28,321, 2008).
The Natural Resources Defense Council and Sierra Club had said
states have too much flexibility, which means that in some cases
standards are not being met. They challenged two George W. Bush-era
rules, one from 2007 and one from 2008, that laid out how fine particle
standards last set in 1997 should be implemented.
The environmental groups argued that the rules gave states too
much flexibility in determining how to meet the standards and that
EPA ignored language in the Clean Air Act as amended in 1990, which
addressed implementation of particulate matter standards in a more
stringent manner then implementation for other pollutants.
In its ruling, the court held that the Clean Air Act required EPA
to handle implementation of the PM 2.5 standards under the more
stringent provision of the CAA. The court then sent the rules back
to EPA with instructions to re-promulgate the rules pursuant to
the particulate-matter-specific provisions of Subpart 4 of Part
D of Title I rather than pursuant to general implementation provisions
of Subpart 1 of Part D of Title I.
The complete opinion is online at: http://www.cadc.uscourts.gov/internet/opinions.nsf/5E67334CF6182C5E85257AE90054C0C1/$file/08-1250-1413399.pdf.