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

Dr. Steven KleebergerComments on SOx 2 nd Draft ISA3. In the revision, we reduced redundancy, added summary sections and reorganizedChapter 3. In addition, discussions on potential confounding by and interactions withcopollutants have been added. The 2nd draft ISA also includes additional analyses ofindividual-level data from human clinical studies (Sections 3.1.3. and 4.1.1) that buildsupon the analysis included in the 1994 Supplement to the Second Addendum. Thetoxicology sections were reorganized to focus on studies using more relevantconcentrations of SO2 and sections were added to better discuss mode of action andpotential particle-SO2 interactions. We are requesting CASAC review specifically onthese analyses as well as on the integration of the overall evidence from the humanclinical, animal toxicological, and epidemiological studies.Overall, the reorganized Chapter 3 is greatly improved over the previous version.In particular, the following aspects of the Chapter were useful:• Summary of findings from the previous review – these provide much needed anduseful reference points to enable evaluation of the more current investigations.• Redundancy was largely eliminated, though some repetition remains that could beedited or removed.• Additional individual-level data (i.e. specific numbers of individuals in responsegroups) enabled better evaluation of between-individual variation and the impacton interpretation of results.• Removal of animal studies that used SO2 concentrations that had questionableenvironmental relevance was appropriate, though some remain that likely couldalso be removed.• The end-section summaries were very useful and largely presented a reasonableevaluation of the literature with respect to weight of evidence for causaldetermination.• Incorporation of the effects of SOx intervention and subsequent change in healthoutcomes into evaluation of causality was appropriate and useful.Additional Comments:While it may be argued that SO2/particle interactions should be included in theISA document, the case was made in the REA that the current review of the SO2NAAQS would focus on gaseous species of sulfur oxides and not consider health effectsdirectly associated with particulate sulfur oxide species. These species and their healtheffects instead will be reviewed in the PM document. However, one of the sections in the24