Robert Esworthy Specialist in Environmental Policy
October 17, 2006, the Environmental Protection Agency (EPA) published its final
revisions to the National Ambient Air Quality Standards (NAAQS) for
particulate matter (particulates, or PM). Several states and industry,
agriculture, business, and environmental and public health advocacy groups
petitioned the U.S. Court of Appeals for the District of Columbia Circuit, challenging
certain aspects of EPA’s revisions. A February 24, 2009, decision by the D.C.
Circuit granted the petitions in part, denying other challenges, and
remanded the standards to EPA for further consideration but did not
specifically vacate the 2006 PM standards. EPA initiated its next round of
the periodic review of the PM NAAQS, in part, in response to the court’s
decision and on June 29, 2012, published a proposal to strengthen the
standards. These actions, and the ongoing implementation of the 2006 PM
NAAQS, have prompted renewed interest among Members of Congress.
Experiences and issues leading up to and following the promulgation of the 2006
PM2.5 NAAQS could provide relevant
insights as EPA proceeds with its current review. Although a tightening of the
standards, the particulates NAAQS established in 2006 were not as stringent as
recommended by EPA staff or the independent scientific advisory committee
mandated under the Clean Air Act (Clean Air Scientific Advisory Committee,
or CASAC). The divergence from the CASAC’s recommendations proved
controversial, as did several other elements of the 2006 particulates NAAQS,
including the decision not to exclude rural sources from the coarse particle
EPA found that the evidence continued to support associations between exposure
to particulates in ambient air and numerous health problems. Based on
several analytical approaches, EPA estimated that compliance with the
revised NAAQS would prevent 1,200 to 13,000 premature deaths annually, as
well as substantial numbers of hospital admissions and missed work days due to
illness. EPA revised the PM NAAQS by strengthening the 1997 standard for “fine”
particulate matter 2.5 micrometers or less in diameter (PM2.5). Specifically, the agency lowered the allowable daily concentration
averaged over 24-hour periods of PM2.5 in
the air from 65 micrograms per cubic meter (μg/m3) to 35 μg/m3.
The annual PM2.5 standard, which is set in addition
to the daily standard to address human health effects from chronic
exposures to the pollutants, was unchanged from the 1997 standard. The
decision not to tighten the annual standard was overturned by the D.C.
Circuit and remanded to EPA for consideration.
The 2006 particulates NAAQS also retained the 24-hour standard and revoked the
annual standard for slightly larger, but still inhalable, particles less
than or equal to 10 micrometers (PM10).
EPA abandoned its proposal to replace the particle size indicator of PM10 with a range of 10 to 2.5 micrometers (PM10-2.5). The D.C. Circuit’s February 24, 2009,
decision upheld EPA’s decisions with regard to PM10 NAAQS.
EPA’s ongoing implementation of the 2006 NAAQS, including EPA’s November 13,
2009, final designation of those geographical areas not in compliance
(typically defined by counties or portions of counties), has been an area
of debate among some Members of Congress, states, and other stakeholders.
Although EPA did not require new nonattainment designations for PM10, the tightening of the PM2.5 standard
resulted in an increased number of areas in nonattainment compared to the
designations for the 1997 PM NAAQS. EPA’s November 2009 final designations for
the 2006 PM NAAQS included 120 counties and portions of counties in 18 states
as nonattainment areas based on 2006 through 2008 air quality monitoring
Date of Report: March 14, 2013
Number of Pages: 31 Order Number: RL34762 Price: $29.95
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