"The CASAC Sulfur Oxides Primary National Ambient Air Quality Standards (NAAQS) Review Panel (see Enclosure A for Panel Roster) is providing review comments on the Environmental Protection Agency's (EPA) second draft EPA's Risk and Exposure Assessment (REA) to Support the Review of the SO 2 Primary National Ambient Air Quality Standards: Second Draft. This letter provides CASAC's overall comments, highlighting the most important issues to be addressed in revising the second draft REA. Responses to the specific charge questions (Enclosure B) and comments from individual Panel members (Enclosure C) follow."--Page 1

"The Clean Air Scientific Advisory Committee (CASAC) NOX & SOX Secondary NAAQS Review Panel met on July 22-23, 2009 to review EPA's Risk and Exposure Assessment (REA) to Support the Review of the Secondary National Ambient Air Quality Standard for Oxides of Nitrogen and Sulfur: Second Draft. This letter has been reviewed and approved by the chartered CASAC at a public conference call on August 20, 2009. In this letter, CASAC offers general comments and recommendations for finalizing the REA. We also address the Agency's framework for developing the forthcoming Policy Assessment. During the meeting, EPA's Office of Air Quality Planning and Standards (OAQPS) informed the Panel of the final schedule for the current primary and secondary NOX and SOX NAAQS reviews and rule making. CASAC is very concerned about the schedule's implications on the policy options under consideration by the Agency for the secondary standards."--Page 1