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Dr. Allan Legge Final Review Comments: Allan H. Legge "Review of the National Ambient Air Quality Standards for Ozone: Policy Assessment of Scientific and Technical Information" OAQPS Staff Paper, January 2007, EPA-452/R-07-003. Chapter 7: Policy-Relevant Assessment of Welfaze Effects Evidence Chapter 8: Staff Conclusions and Recommendations on a Secondary 03 NAAQS Overall Comments: The same underlying scientific assumptions used by Staff in the previous version of the Staff Paper (July, 2006) with respect to the secondary 03 NAAQS aze still being used in this version and are still seen as highly uncertain and as a result are still very problematic. While Staff has made an admirable effort to more fully identify where uncertainties exist, the matter of the propagation of error/uncertainty and its potential accumulative impact on their analysis still has not been addressed. However, it is clear that Staff recognizes the importance of the need to quantify these uncertainties, as some of these uncertainties are identified in their research recommendations (pp. 8-27 to 8-29). It is important to note that Staff has been at a maj or disadvantage preparing this Staff Paper due to the fact that the state of the science regarding ambient ozone and vegetation/ecosystems has not changed very much since the last 03 AQCD. Since the Agency has provided little or no support for research in this area in the intervening years from 1996 to the present fo help remedy this problem by improving the state of the science and hence reducing the scientific uncertainties, the Agency must be strongly criticized for this lack of action. This is very unfortunate because it is clear that a scientifically defensible and protective secondary 03 standard is needed especially when there is evidence of foliaz injury from exposure to ambient ozone at the current primary standazd. Staff has attempted to get. around the `lack of adequate scientific information' .problem by selectively using the results of a series of `elegant and imaginative' mathematical analyses drawn from the revised technical document prepared for OAQPS by Abt Associates Inc. (2007)[ see "Technical Report on Ozone Exposure, Risk, and Impact Assessment for Vegetation" -January 24, 2007]. The starting point of the analyses is the definition of the set of ozone metrics which will be used and which aze all assumed to have a solid scientific foundation. The ambient ozone data which are modeled and/or monitored are the input data which are then used in the generation of the national potential 03 exposure surface (POES) after which these data aze subject to various `rollback methodologies'. These data are then used to estimate crop and tree ozone exposures which ultimately lead to an economic benefits assessment for agricultural crops using AGSIM and tree growth simulation using TREGRO. Essentially, the results of each set of analyses forms the basis for the next set of analyses and so on. It is the results of these `elegant and imaginative' mathematical analyses which provide much of the foundation for the conclusions drawn by Staff regazding the selected potential secondary 03 standards. That being G_. ~-! C-17