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cautioned that the relationships among various ozone indices are likely to change as progress is made toward reducing concentrations. It's not required that a secondary standard be effectively more stringent than a primary standard, but as a practical matter, a secondary standard at a level equal to or less stringent than the primary standard has no function, since the primary is to be attained within 5 years, while the secondary has no time limit. However, a secondary standard that is more stringent than the primary extends the spatial extent and/or the relative degree ofnon-attainment, and so as a matter of policy, the Agency has tended to avoid setting separate secondary standards in the past. Indeed, when setting secondary standards (equal to primary standards) in the 1997 review for ozone; and more recently for fine particles in 2006, the Agency had first concurred with staff & CASAC that secondary standards with levels, forms and/or averaging times different from primary standards were clearly warranted, but then rationalized that the incremental benefits of achieving those alternative secondary standards -once the new primary standards had been attained -appeared to be small, and so the secondary standards were simply set equal to the primary. For this reason alone, seeing a proposed secondary standard which is less stringent than the upper range of the primary standard is a reason for concern. It looks like aset-up for a conclusion that a separate secondary standard is not needed. In fact the SUM06 equivalent (25 ppm-hrs) to a W 126 at 21 ppm-hrs was considered in 1997 and discarded as not being a substantial improvement over the 8-hour maximum of 0.084 ppm. If staff proposes lowering the primary standard to (well) below 0.080 ppm, as is clearly warranted by the current health assessment, then to also recommend a secondary standard at a level that was discarded in 1997, for adding insufficient benefits to the 0.084 ppm primary standard, seems like a predetermination that a separate secondary standard will not be seriously considered once again. Unquestionably a lowering (and attaining) of the primary daily 8-hour standard to the range of 0.060 to 0.070 ppm would have substantial beneficial reductions in the environmental effects of ozone. But if the Agency is also considering a secondary standard towards the upper end of the proposed range, 1 would strongly discourage the use of the "nearly covered by the primary standard" logic to avoid setting a separate secondary standard. The different averaging time is clearly warranted, there may well be changes in the relationship between daily maxima and seasonal. indices (and growing seasons) in the future, there would be clear educational benefits in formalizing a separate environmental metric, and additional research would be encouraged to reduce current uncertainties and refine that environmental metric in future reviews. Some additional reasons for reducing the upper end of the range - or for other possible more protective revisions to other aspects of the secondary standard metrics include the following: A reason for our previous recommendation to include "at least" 12 daylight hours in aggregating the W 126 was the knowledge that not all the effects of ozone occur during daylight /photosynthesis (Musselman and Minnick, 2000). But the current staff argument (SP page 8-17) that "nocturnal stomatal conductance varies widely between species" (emphasis added) does not provide a compelling reason to discard the all the nighttime hours. The fact that some plant species are less sensitive than others to nocturnal ozone exposures is not a good reason to constrain the standard's applicability to disregard effects on those species which are sensitive. As a practical matter, most of the higher hourly ozone levels " I i"t C-25