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EPA Revises NAAQS for Fine Particulate Matter


On December 14, 2012 EPA signed a final rule that increases the stringency of the National Ambient Air Quality Standard (NAAQS) for fine particulate matter (PM2.5). It was published in the Federal Register on January 15, 2013. The revised PM2.5 standard will become effective on March 18, 2013.  In particular, the final rule strengthens the primary annual PM2.5 standard from 15 micrograms per cubic meter (ug/m3) to 12 ug/m3.  The existing annual standard was set in 1997.

In finalizing the rule, EPA determined to retain the existing 24-hour primary standard for PM2.5 at 35 ug/m3.  The 24-hour standard was last revised in 2006.  EPA has also retained the existing secondary standards for PM2.5, which are essentially set at the same level as the existing primary PM2.5 standards.  The existing secondary 24-hour PM standards are intended to protect against visibility impairment.  Finally, EPA has retained the existing coarse particulate matter (PM10) 24-hour primary and secondary standards, which are 150 ug/m3.

Information available from EPA indicates that 66 counties on a nationwide basis have ambient air monitors that currently do not show compliance with the 12 ug/m3 annual PM2.5 standard based upon ambient air monitoring data from 2009 through 2011.  Based upon particulate matter emission reductions required by current rules, EPA predicts that only seven counties located in California will not meet the new PM2.5 annual standard of 12 ug/m3 by 2020.  In Kentucky and Indiana, EPA projects 11 counties would be designated as nonattainment based upon data from existing monitors in those counties.  In Indiana, this includes the counties of Clark, DuBois, Floyd, Lake, Marion, Spencer, Vanderburgh, and Vigo.  In Kentucky, the potential nonattainment counties include Bullitt, Daviess, and Jefferson.  It should be noted, however, that the three-year annual design value of PM2.5 in ambient air in many counties in both states is above 11.0 ug/m3, and thus, are close to the new standard.  States will have a year to make recommendations for areas to be designated as attainment and nonattainment for the new annual PM2.5 standard.

Because the new annual PM2.5 standard, when effective, would apply for purposes of prevention of significant deterioration (PSD) permitting, EPA has included a grandfathering provision in the final rule to ensure that changes to the PM2.5 standard do not delay issuance of pending PSD permits and to reduce potential permitting burdens.  In particular, the grandfathering provision provides that PSD review based upon the existing annual PM2.5 standard will be available for any draft PSD permit or preliminary determination that has been published for public notice prior to the March 18, 2013 effective date of the revised PM2.5 standard (i.e., 60 days after publication of the final rule in the Federal Register) and for PSD permit applications that have been deemed complete by the permitting agency as of the time of signing of the final rule (December 14, 2012).  For permit applications that do not meet one of these two criteria, the permit application will be reviewed to ensure compliance with the revised annual PM2.5 standard.  The grandfathering provision does not apply to any other pollutants.

EPA explained in the preamble to the final rule that it is not proposing and is not finalizing any changes to the existing PM2.5 significant emission rates (SERs), significant impact levels (SILs), and significant monitoring concentrations (SMCs).  Accordingly, these screening tools, which establish de minimis thresholds for PSD permitting purposes, would have remained the same as promulgated in EPA’s May 16, 2008 and October 20, 2010 final rules.  However, as discussed elsewhere in this issue of the Air Quality Letter, the October 20, 2010 final rule establishing these screening tools was vacated by the U.S. Court of Appeals on January 22, 2013.  Also, the May 16, 2008 implementation rule for the PM2.5 standard was remanded to EPA on January 4, 2013 by the U.S. Court of Appeals for the D.C. Circuit, but that court ruling is not expected to affect the 10-ton per year SER established for PM2.5 in attainment areas.

Finally, the preamble to the final rule also discusses modeling tools and guidance applicable to modeling impacts of PM2.5 emissions.  EPA references its March 23, 2010 guidance memorandum from Stephen Page as containing interim procedures to address the fact that compliance with the 24-hour PM2.5 standard is based upon a particular statistical form and to address the complications associated with the impacts of secondarily formed PM2.5 due to precursors.  To provide more detail and guidance on those issues, EPA stated in the December 14, 2012 rule that it intended to issue final guidance on modeling of PM2.5 impacts from stationary sources for permitting purposes by the end of calendar year 2012.  As of the date of this publication, that guidance has not been issued and may be delayed due to complications from the above referenced Court of Appeals rulings.  EPA states it expects the revised guidance will address most, if not all, of the remaining issues relating to PM2.5 air quality impact demonstrations under the PSD program at least until EPA takes additional steps to improve existing regulatory models and procedures.

To view a complete PDF of the Fourth Quarter 2012 issue of the Air Quality Letter, click HERE.

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