Lowering the PM NAAQS

EM – May 2023: This month, EM discusses the scientific basis for EPA's proposal to tighten the fine particulate matter (PM2.5) National Ambient Air Quality Standard (NAAQS), and its potential implications.
by John Kinsman and Yiqiu Lin

To address human health concerns, the U.S. Environmental Protection Agency (EPA) has proposed Reconsideration of the National Ambient Air Quality Standards for Particulate Matter. EPA proposes to revise the annual National Ambient Air Quality Standard (NAAQS) for fine particulate matter (PM2.5) from its current level of 12 µg/m3 to within a range of 9–10 µg/m3. The agency also addresses the level of the daily PM2.5 NAAQS and implementation issues such as compliance monitoring, sensors, wildfire and exceptional events, interstate and international transport, and permitting. Articles in this issue of EM address PM2.5 issues in general and aspects of EPA's proposal.

The first article by Gregory Stella of Alpine Geophysics discusses the impact of lowing the annual PM2.5 NAAQS from 12 µg/m3 to 8–10 µg/m3, including the significant increase in nonattainment counties (that fail the standard) and challenges for permitting authorities in a newly designated nonattainment area.

The next article by Michael Abraczinskas, Jason Meyers, and Jason Sloan of the Association of Air Pollution Control Agencies (AAPCA) introduces the NAAQS program and the history of particulate matter standards, as well as the U.S. Clean Air Act (CAA) requirements for review and reconsideration of NAAQS. 

The third article by Mary Uhl, Rhonda Payne, and Jay Baker of the Western States Air Resources Council/Western Regional Air Partnership (WESTAR/WRAP) discusses the significant impact of wildfire smoke on PM2.5 ambient levels and NAAQS compliance, especially in the western United States, where wildfire smoke PM2.5 has increased greatly in recent years.

Continue reading the full May 2023 issue of EM.


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