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Dr. James (Jim) Zidek <br />Comments on the Final Staff Report on NAAQS for Ozone <br />James V Zidek, REVISED Mar, 2007 <br />General: The final report is a substantial improvement over the original. Moreover, it <br />summazizes well in Section 6.3.1.3 CASAC's discussion of on the need to tighten the NAAQS or <br />ozone. <br />However, the proposed Staff upper limit of being somewhat below 0.080 is not only ambiguous <br />but will, de facto, be taken as an upper limit of 0.080. Thus to two decimal places, it includes the <br />current standard, something that runs against not only the letter of the CASAC recommendation <br />but against is spirit as well as the spirit of the Staff s own position. A more practical alternative <br />would have been 0.074, a level that has the well studied by Staff. <br />However, that still leaves the question of why Staff elected to go above the CASAC limit of <br />0.070 that I continue to support very strongly. Some rationale for that decision should have been <br />provided in the report for the Administrator's consideration. <br />CHAPTER 3 <br />Shephard et a1(2005) cited in Section 3.4.2.1 is not in the bibliography at the end of Chap <br />3. <br />CHAPTER 4 <br />The uncertainty analysis around Figures 4-4 to 4-6 is a valuable addition to the document <br />and shows that the predictive point estimates of the percentage of children at given <br />exposure levels are not susceptible to much uncertainty due to APEX output variability. <br />Page 4-22. The final report ignores the suggestion that LM=1 and LA =0 be used to avoid bias <br />in estimating the exposures of individuals who work outside the study azea. While that bias is <br />likely to be small, running the model with those parameters as well as with both set to zero <br />would have given some idea of its size. <br />Page 4-31 To repeat a point made about the Second Draft, tailoring APEX to fit the California <br />situation assesses whether the model is ideally capable of accurately forecasting <br />exposure. However, APEX as used to set National standards is a different model and it <br />too should be assessed. It's AERs could well be higher than those in Sacramento in which <br />case, it would not underestimate exposure like its tailored counterpart. The point is it <br />could have been run with both sets of parameters to see if this made a meaningful <br />difference. <br />tx-- ~f <br />C-32 <br />