Review of the Secondary National Ambient Air Quality Standards for Oxides of Nitrogen and Oxides of Sulfur

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The Office of Air Quality Planning and Standards (OAQPS) of EPA recently made available a draft report, Policy Assessment for the Review of the Secondary National Ambient Air Quality Standards for Oxides of Nitrogen and Oxides of Sulfur: Second External Review Draft (75 FR 57463, September 21, 2010). The EPA released this preliminary draft document to seek early consultation with the Clean Air Scientific Advisory Committee (CASAC) and to solicit public comment on the overall structure, framing of key issues and conclusions regarding options for key elements of the standards. Four supplementary materials were released at a later date (75 FR 61486, October 5, 2010). The supplementary materials were: an errata sheet for Chapter 5; an addendum for Chapter 5; an additional Table 7-1 (summary of key uncertainties); and an additional table for Chapter 9 (summary of options for elements of the nitrogen oxides (NO X ) and sulfur oxides (SO X ) standard). Comments were originally scheduled to be submitted on or before November 12, 2010. A request for an extension to the comment period has been received. The EPA is granting this extension to allow stakeholders and the public with adequate tim