(CASAC) Peer Review of EPA's Integrated Science Assessment

SO2 document (3.1.5) includes effects of SO2 layered on particles and sulfite aerosols. Idid not find the section fit particularly well with the rest of the document and raisedadditional questions that could not be answered, or may have been answered in the PMdocument. My recommendation would be to eliminate this section.The REA clearly differentiates between long-term exposure (months to years),short-term exposures (hours to days), and short-term peak exposures (5-10 minutes)throughout the document, especially beginning with the Health Effects chapter (part 4).The ISA differentiates primarily between long-term exposure and short-term exposures,with the short-term peak exposures embedded in the latter (e.g. section 3.1.3). Anintroductory statement or small paragraph placed at the beginning of the major sectionsof Chapter 3 (e.g. 3.1) which define the distinction may help the reader to place thestudies in the intended perspective.MinorP 3-4, line 5: delete “a” from “presenting a more details”?P 3-13, lines 26 and 28: is it correct to suggest that SO2 may elicit an allergicinflammatory response? SO2 is not an allergen.P 3-17, lines 9-21. I am not sure that this section really provides “biological plausibilityfor the effects of SO2 on respiratory symptoms in humans”. The relevance of MUC5ACexpression induced by SO2 using in vitro models and in rats exposed repeatedly to 2 ppmSO2 to respiratory symptoms in humans is questionable, and presenting these preliminarystudies is not necessary.P 3-103, line 10. “is” should be “are”?25