Review of the Air Quality Criteria Document for Particulate Matter

Below are additional detailed comments on the visibility focus group materials.- Little confidence should be attributed to one focus group of 9 people in one location(Washington, D.C), and this group should not be seen as sufficient to launch a multi-cityassessment. I advise repeated groups in the first location to obtain more data and to addressissues before proceeding to other locations, or to conclusions. Among the issues that couldbe considered are (1) how do the types and kinds of locations presented in the vistas alter theconclusions, if at all? (2) how much are perceived health concerns affecting the judgements,and how can this be better addressed? (3) what does it means when people say theimpairment is acceptable or unacceptable? It is based on the view, the impact on their mood,are there behavioral changes? Does this mean the identified threshold level is acceptableevery day or several days a year? Does this mean respondents are no longer impacted, or justthat they think the likely perceived costs of further control may not be worth it (and on whatbasis do they make such a judgement), or that further improvements are not realistic. In thisrating, respondents are participating in a stated preference (SP) assessment, and moreattention should be given to the SP literature. (4) Which measure will be used? For example,in the simple rating, the cross over point for unacceptable is 20 :g/m 3 , but with the “howmany hours a day” rating, 32.5 :g/m 3 is acceptable for as many as 4 hours a day by twothirdsof the respondents (and thus presumably a level of higher than 32 :g/m 3 for 4 hours aday would be acceptably on a simple 50% rule), and based on the economics data, there isclear impairment below 20 :g/m 3 .- When moving to multiple locations, issues arise such as which vistas to present, what type ofimpairment (which varies in some locations), and how correlated will the ratings acrosslocations be to existing conditions across locations (valuation literature would suggest statusquo bias leading to anchoring and some adjustment to improved conditions).- While the approach follows similar work at the state and local level, it is not clear that theapproach is sufficiently resolved for a national standard when the “impairment” thresholdmay be highly variable across locations. How does EPA see using the results? How might theresults tie in to the PM NAAQS or other visibility rules?- The economic valuation questions are preliminary, yet highlight there may be meaningfullosses at visibility levels below the 50% rule for acceptable ratings. In the preliminary focusgroup the switch from 50% acceptable to 50% unacceptable occurs at 20 :g/m 3 . However,when provided a choice, 5 of 9 would choose 15:g/m 3 and pay $50/year, as opposed to 22.5:g/m 3 and paying $10/year (2 were indifferent between 15:g/m 3 and 22.5:g/m 3 , and 2 chose22.5:g/m 3 over the status quo of 32.5:g/m 3 ). This suggests a significant value for visibilityconditions below the 50% rule level for either the simple ratings or hours per day ratings. Isupport further investigation into the economic valuation approach, with much moreattention to survey design consistent with the stated preference valuation literature. Toaddress the joint product issue between visibility and health, one might revisit the Carson etal. Cincinnati work performed for EPRI some years ago, which by the way showed lossesdown to just a few days a year of visibility impairment (e.g., an indistinguishable changewhen presented on an annual average basis).- There are important concerns with the proposed “focus group” approach to this assessment.Generally a study consisting of a group of focus groups across different locations may not beviewed as sufficiently rigorous for the intended policy application. EPA should see the focusgroup approach only as a preliminary effort to a larger scale survey effort.Staff Paper Visibility SectionThis section is better than the corresponding section in the CD. The two sections shouldbe consistent. A few suggested editorial changes for the Staff paper (aside from continuing toinclude but reduce the discussion of this work). On page 5-16, I recommend active use andA - 71