4 The record articles

Mind Your NAAQS: An Update

Posted: September 17th, 2012

Author: All4 Staff 

The pre-election regulatory lull is in full swing, so we thought it was a good time to get fully caught up on the latest National Ambient Air Quality Standards (NAAQS) news.  Here are the key points to be aware of related to criteria pollutant NAAQS levels:

  • 1-Hour Sulfur Dioxide (SO2): We have been keeping you up to date on the 1-hour SO2 NAAQS saga through various blog posts and 4 The Record articles.  Our last update pertained to the U.S. EPA stakeholder workgroup meetings that were held to solicit comments on the best way to implement the 1-hour SO2 NAAQS (dispersion modeling, monitoring, or a combination of both?).  U.S. EPA heard a range of comments at those meetings and is tasked to release a proposed rulemaking or proposed guidance on the NAAQS implementation process.  Given the information that U.S. EPA needs to consider and the logistical considerations around a possible increased ambient monitoring network, we would be surprised to see anything be released until mid-2013.  Keeping with that trend, U.S. EPA delayed the finalization of 1-hour SO2 designations for areas with ambient monitoring data until June 2013.
  • Annual Fine Particulate Matter (PM2.5): U.S. EPA is threatening in proposed rulemaking to tighten the annual PM2.5 NAAQS from 15 micrograms per cubic meter (µg/m3) to 11 to 13 µg/m3.  It is already very difficult to demonstrate modeled compliance with the annual NAAQS under the Prevention of Significant Deterioration (PSD) modeling process for major permitting projects.  A tightened standard would make it even more difficult and is very likely to rapidly expand the list of PM2.5 nonattainment areas since the proposed 11 to 13 microgram per cubic meter range is already being measured as a background concentration at many of the existing ambient monitors.  A possible secondary PM2.5 NAAQS that is visibility oriented is also lurking out there. Regardless of the outcome of this process, facilities will continue to need to find internal reductions to offset PM2.5 emissions increases so that major source and modification permitting requirements can be avoided for PM2.5.
  • 8-Hour Ozone: The reconsideration of the 8-hour ozone NAAQS (a range of 65 to 75 µg/m3 was considered) that was destined to increase the number of ozone nonattainment areas was dropped by presidential order.  However, don’t lose sight of the ozone NAAQS.  The next reconsideration is scheduled for 2013, so the process of evaluating more stringent ozone standards and the nonattainment area permitting implications of a tightened ozone standard will happen again.

On a bigger picture note, legal challenges to the 1-hour SO2 and NO2 NAAQS levels were recently rejected, so the NAAQS levels are here to stay for the foreseeable future.  These recent court cases show that health-based standards, once established, will be difficult or even impossible to scale back (although there is still hope that the implementation process for those standards can be adjusted). Given the permanence of the NAAQS levels, they will continue to be one of the primary areas that dictate a facility’s ability to operate and expand in the future.  We will continue to keep track of the latest developments around the NAAQS levels, so stay tuned for updates as they arise.


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