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The Environmental Protection Agency (“EPA”) is publishing their long-awaited “Reconsideration of the National Ambient Air Quality Standards for Particulate Matter” rule.   In this posting, the EPA will be accomplishing two things:

  • They will propose a concentration range for the annual (1-Year) particulate matter (“PM”) National Ambient Air Quality Standard (“NAAQS), and
  • They will be requesting comments regarding other possible annual (1-Year) and daily (24-Hour) PM NAAQS levels.

The EPA is proposing to tighten the primary annual PM2.5 NAAQS from the current value of 12 µg/m3 to a range of 9 to 10 µg/m3.

The EPA is also requesting comment on the following primary annual PM less than 2.5 microns (“PM2.5”) “alternative standard” concentrations:

  • A PM5 NAAQS level of 8 µg/m3
  • A PM5 NAAQS level of 11 µg/m3

In addition, although the EPA is not currently proposing a change to the primary and secondary daily (24-Hour) PM2.5 NAAQS level of 35 µg/m3, they are requesting comments related to the possibility of lowering the daily standard to 25 µg/m3.

Lowering the PM2.5 NAAQS will most likely mean that additional areas of the country will be designated as PM2.5 NAAQS nonattainment at some point in the future. In addition, even if a particular area is not designated as PM2.5 nonattainment, lowering the NAAQS will narrow the difference between background monitored concentrations and the newly revised NAAQS.  Lowering of the PM2.5 NAAQS could make an air quality analysis, showing protectiveness of a future standard, more difficult to demonstrate through the use of air dispersion modeling.

Are you tracking PM2.5 NAAQS issues?  Do you need help evaluating where your site currently is versus how a lower annual PM2.5 NAAQS may affect your site?   Are your PM2.5 emission rates up to date?   If you are unsure about any of these topics or have additional questions, feel free to reach out to the professionals at Spirit Environmental, and we’ll be glad to provide assistance and help you meet your air authorization goals.

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