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Dr. Barbara Zielinska Comments on the Ozone Final Staff Paper, Chapter 6: Staff Conclusions and Recommendations on the Primary 03 NAAQS Barbara Zielinska In my opinion, Chapter 6 of the Final Staff Paper, although very long, is well written, and adequately summazizes the pertinent scientific information. I have only a few comments regarding this chapter: 1. I think that the Staff recommendation for the new NAAQ ozone standard "within the range of somewhat below 0.080 ppm to 0.060 ppm" is rather vague as far as the upper limit of the standard is concerned and includes the possibility of changing the standard very little (0.079 ppm is also "somewhat" below 0.080). The first level below 0.080 ppm that has been shown in the Staff Paper as bringing substantial health benefits (Figures 6-1 to 6-6) was 0.074/4. However, the 0.070/4 option was even better and the trend continued to the 0;064/41eve1(the last shown). For this reason, taking into account the data shown in the Staff Paper, I would consider the 0.074/4 option as an upper limit. 2. However, as stated in Section 6.3.2 (Indicator), ozone is only a surrogate for the larger group of photochemical oxidants, which health effect is largely unknown. Thus, it is possible, that acute exposure chamber studies that investigate the effect of ozone alone may underestimate the responses to ozone in ambient air mixtures. Taking into consideration that "measures leading to reductions in population exposures to 03 aze generally expected to lead to reductions in population exposures to other photochemical oxidants" (page 6-53), I support 0.070 ppm as the upper limit for the primary ozone standard. 3. I agree with comments of other panel members that the Chapter 6 does not adequately address the "mazgjn of safety" issue in recommending the upper limit of the ozone standard as "somewhat" below 0.080 ppm. I also agree that the limiting the analysis of 03 exposure to 12 major cities may underestimate its impact; as it has been shown that 03 concentrations downwind of an urban area are often higher than within a city. 4. The Staff Paper method for estimating the Policy Relevant Background (PRB) is still not adequately justified and somewhat controversial. PRB may be relevant to a question if the considered NAAQS for ozone is attainable. Although it is possible that the proposed range of 0.070 to 0.060 ppm may overlap with extreme local values of PRB, it is rather unlikely thaf such!overlap would occur frequeritly, especially for 8-hr average concentrations. Ag shown by Lefohn (2007), the diurnal 03 concentrations that were measured in Trinidad Head, CA (background site), in April (the highest 03 month) ranged from 0.030 to 0.050 ppm and the maximum hourly value reported was 0.066 ppm. In addition, the statistical form of the proposed ozone standard (annual third- to fifth- highest daily maximum 8-hr average concentration, averaged over three years) largely removes the influence of extreme events. Reference: Lefohn, A. S. (2007) Major issues inadequately addressed in the final version of the EPA's Ozone Staff Paper. Comments on the EPA Staff Paper, submitted to EPA. _.' ~` C-35