On September
21, 2006, EPA announced with regard to primary standards for
fine particles (generally referring to particles less than or
equal to 2.5 micrometers (µm) in diameter, PM-2.5) that
it was revising the level of the 24-hour PM-2.5 standard to 35
micrograms per cubic meter (µg/m3) and retaining the level
of the annual PM-2.5 standard at 15 µg/m3. With regard
to primary standards for particles generally less than or equal
to 10 µm in diameter (PM-10), EPA is retaining the 24-hour
PM-10 and revoking the annual PM-10 standard. With regard to
secondary PM standards, EPA is making them identical in all respects
to the primary PM standards, as revised. The issue of reliability
of the epidemiological time-series methodologies continues to
be of concern to the Administrator. The Administrator noted in
his decision that there were many sources of uncertainty and
variability inherent in the inputs to the assessment and that
there was a high degree of uncertainty in the resulting PM-2.5
risk estimates. Such uncertainties generally related to a lack
of clear understanding of a number of important factors, including,
for example, the shape of concentration-response functions, particularly
when, as here, effect thresholds can neither be discerned nor
determined not to exist; issues related to selection of appropriate
statistical models for the analysis of the epidemiologic data;
and the role of potentially confounding and modifying factors
in the concentration-response relationships. For those interested
in the possible violation areas for the revised 24-hour PM-2.5
standard based on 2004-2005 data, please click here. On December 15, 2006, public health and environmental
groups filed suit against the U.S. EPA for refusing to strengthen
the PM-2.5 annual standard.
The PM-2.5 compliance deadline is as follows:
10/17/06: PM NAAQS final rule published
in Federal Register.
12/18/06: Effective date of the final PM NAAQS rule.
12/18/07: Based on air monitoring data collected in 2004-2006,
States’ submit recommendations to EPA as to whether or not
local communities are complying with the PM NAAQS.
12/18/08: EPA makes final PM compliance designations after reviewing
most recent monitoring data and EPA may take one additional year
to decide, up to 12/18/09.
4/27/10: Effective date for EPA’s PM compliance designations.
4/27/13: Deadline for States to submit PM State Implementation
Plans (SIP) to ‘clean up’ the air in those communities
designated as ‘non-attainment’.
