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

Dr. Donna KenskiComments on SOx ISA – 2nd DraftGeneral comments: The revisions to Chapter 2 have improved it substantially. Inparticular, Sections 2.5.3 and 2.5.4 on exposure measurement errors were improved andclarified. The added tables and discussion were helpful. The added information on 5-minute averages was a good start, but lacked enough detail to form adequate basis fordecision-making. The dismissal of these data because of the voluntary nature of thereporting and their variability over time and space is troubling. In light of the number ofhealth studies showing effects at 5- to 15-minute exposure times, the importance of theinformation for the Risk and Exposure Assessment, and given EPA’s request that thestates collect this data, it seems unreasonable to dismiss it in this document without evena rudimentary summary of the data. The REA goes on to glean important informationfrom the relationship of the 5-minute peaks to hourly means, so the very limiteddiscussion in this document is surprising. This particular shortcoming was not apparentin the previous version of the ISA, before the REA had been drafted. The removal of theNOx information from Annex B was a good decision; it makes it much easier to find therelevant data for SO2. Some specific comments follow:2-1 line 13 The initial phrase, “Industrial emissions…” is somewhatmischaracterized; perhaps the authors meant anthropogenic emissions? Utility emissionsare usually regarded separately from industrial emissions.2-2 1 st paragraph. This section still needs a simple sentence quantifying biogenic ornatural sources. It is unacceptable to spend 2 paragraphs describing naturalsources and still not quantify them except as ‘small’, which could be 10% or 1%or 0.01%. Even Table B-3 doesn’t do so; the reader is left to infer that suchemissions are less than 0.00 Tg/yr.2.2. Line 12 Refers to Table B-6, which does not exist. It doesn’t look like thisdata is available in the revised Annex.2.3 line 14 Reference to Annex B.5 should be B.62.8 Sec. 2.4.1 The addition of the monitor siting criteria was helpful. The openpathinformation is probably unnecessary, however. The sampling and analysisdiscussion didn’t describe any open path instruments for SO2 and since these are a tinyfraction of the reporting network, if there are any at all, it could be deleted without harmto the rest of the discussion.2.11 The new figures 2.1-2.6 are a useful addition. However, the rationale forchoosing these 6 areas for focus needs to be clearly stated. Was it because they have themost monitors, or the highest concentrations, or the most spatial heterogeneity orhomogeneity?18