AG 2007 10 15 - Laserfiche WebLink

Home Browse Search

Dr. Sverre Vedal March 2007 Critique of the Ozone OAQPS Staff Paper Sverre Vedal Chapter 6 (Conclusions/Recommendations) The chapter now reasonably summarizes the state of the science, draws overall defensible conclusions, and generally provides a credible basis for a addressing changes to the ozone NAAQS in light of the science. Inmost instances, appropriate caution is expressed when the data are not as strong as they might be. There are still a few persistent inconsistencies, which I will attempt to detail below. Also, while the opinions of the CASAC are almost always faithfully presented, this is not universally so. A few points: 1. Level of the standard. The staff paper has now appropriately moved away from including the current standard (in essence, 0.084 ppm) in the range of recommended alternatives. The current recommendation, "within the range of somewhat below 0.080 ppm to 0.060 ppm," is more in keeping with the CASAC recommended range of 0.070 to 0.060 ppm. I commend the OAQPS staff in acknowledging the arguments made by the CASAC in this regard. I sense that "somewhat below 0.080 ppm" will leave open the possibility that the standard might be changed very little, which is not in line with CASAC recommendations. 2. CASAC opinions. While most attributions to CASAC. are correct, I don't believe it was a written opinion of CASAC that "more emphasis should be placed on numbers of subjects in controlled human exposure studies with FEV 1 decrements greater than 10%, which can be clinically significant, rather than on the relatively small average decrements" (p.6-43). While this may have merit in some (or even many) situations, for example when noting that 26% of individuals had > 10% FEV 1 decrements at 0.08ppm (p. 5 of the CASAC letter), in other cases, such as the specific case of 0.060 or 0.040ppm exposures (Adams 2006), this approach amounts to attempting to fmd effects in a very few individuals when the statistical tests are not significant, which is a dangerous precedent -especially in this case where we are looking at small effects in 3 of 30 vs. 1 of 30, a pitiful number on which to attempt to base policy (see comment #6 below on future research needs). 3. Choice of alternative standards for risk assessment. It may have been valuable to continue the risk assessment down to a 60/4 scenario instead of stopping at 64/4, but the trend seems clear. 4. Cardiovascular hospitalizations and mortality. Evidence-based considerations (section 6.3.1.1) should have included a discussion of cardiovascular hospitalizations. The evidence for the absence of effects of ozone on cardiovascular hospitalizations has bearing on the plausibility of the mortality findings, which are dominated by cardiovascular, not respiratory, deaths. My review of the most recent fmdings .., C-30