4 The record articles

October NAAQS Happenings

Posted: October 7th, 2011

Author: All4 Staff 

ALL4’s September 4 The Record included an article that provided an update on the status of the new 1-hour sulfur dioxide (SO2) and nitrogen dioxide (NO2) National Ambient Air Quality Standards (NAAQS). The article discussed both the implementation of the new standards and information on the updated air dispersion modeling approaches used to demonstrate compliance with the NAAQS levels. Just prior to publication of the article, U.S. EPA released draft guidance outlining the process by which states should perform dispersion modeling to make attainment and nonattainment decisions related to the 1-hour SO2 NAAQS. Since the release of the U.S. EPA guidance over the past few weeks, several states have begun requesting source-specific information from large facilities for state agency use in performing SO2 air dispersion modeling. After a long period of uncertainty and legal challenges to the SO2 NAAQS implementation approach (the legal challenges are ongoing), SO2 modeling to support attainment or nonattainment designation has arrived and will have wide-reaching, near-term impacts across industry. In fact, we recently published a 4 The Record Extra! that was dedicated exclusively to addressing the details of U.S. EPA’s NAAQS modeling guidance for SO2 and how you can plan ahead.

With the current focus on the SO2 NAAQS and dispersion modeling, all is (relatively) quiet on the NAAQS front for other criteria pollutants. The 1-hour NO2 NAAQS implementation process continues and does not (yet) involve specific facility modeling. U.S. EPA continues to investigate potentially tightening the current annual and 24-hour NAAQS levels for PM2.5. The ozone and CO NAAQS levels will not change in the immediate term after recent U.S. EPA actions left them unchanged. 

In light of these many developments, don’t miss ALL4’s FREE November 17, 2011 “What YOU Need to Know About the 1-Hour SO2 NAAQS Implementation Process” Webinar.


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