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Particulate Matter (PM) PM2.5 Status
Health-Based Ambient Air Quality Standards
Since the PM10 standards were established in 1987, a large number of studies have
been published on PM health effects, such as premature mortality, hospital admissions,
and respiratory illnesses. Based on health studies, PM2.5 is considered to be more
adverse to human health than any other pollutant. EPA adopted the first national
air quality standards for the fine fraction of particulates, PM2.5, in July 1997.
EPA set the annual PM2.5 standard at 15 µg/m3 and the 24-hour PM2.5 standard set at
65 µg/m3. EPA designated the Valley as nonattainment for PM2.5; the Valley’s current
air quality is within the 1997 24-hour standard, but not the annual standard.
The District must show how the Valley will attain the 1997 PM2.5 standards in
the 2008 PM2.5 Plan, which is due to EPA in April 2008.
On October 17, 2006, EPA issued its final rule to revise the national ambient air
quality standards for PM in the Federal Register. This rule revoked the annual PM10
standard and retained the existing 24-hour PM10 standard of 150 µg/m3. EPA also
retained the existing annual PM2.5 standard of 15 µg/m3, but lowered the 24-hour
PM2.5 standard to 35 µg/m3. EPA will designate areas under the new standard by
November 2009, effective April 2010, and state implementation plans for the 2006
standards will be due to EPA by April 2013. Areas must attain the 2006 standards
by April 2015, though extension to April 2020 is possible.
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