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EPA Proposes Revised PM2.5 NAAQS

Under a court-ordered deadline, on 06/14/2012, EPA proposed revised particulate matter National Ambient Air Quality Standards (NAAQS):

  • Lower the annual PM2.5 standard to within the range of 12 micrograms per cubic meter (μg/m3) to 13 μg/m3. The current annual standard (from 1997) is 15 μg/m3.
  • Retain the existing 24‐hour PM2.5 standard (from 2006) at 35 μg/m3.
  • Set a separate 24-hr PM2.5 standard to improve visibility, primarily in urban areas: 30 deciviews or 28 deciviews. (A deciview is a measure of visibility.)
  • Retain the existing secondary standards for PM2.5 and PM10.
  • Retain the existing 24‐hr PM10 standard (from 2006)

Almost all counties in the U.S. are projected to meet the proposed NAAQS by 2020.

EPA is also proposing to grandfather pre-construction air permitting activities that have made substantial progress through the review process at the time the final standards are issued.  EPA is also proposing changes to the PM2.5 monitoring network and Air Quality Index (AQI).

EPA is expected to issue the final standards by December 14, 2012.

EPA will accept comments for nine weeks after the proposal is published in the Federal Register.  Public hearings are expected to be scheduled for July 2012.

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