AG 2007 10 15 - Laserfiche WebLink

Home Browse Search

"Final" Staff Paper draft. This is not only because the calculations are made for only those people living in 12 MSAs, but also because it ignores the people living outside of all of the MSAs in the U.S. The fact that ozone is regional in nature, and is often higher in concentration downwind of MSAs than within them, has not been considered in the risk assessment. 2) Another, perhaps related, deficiency in this chapter is the lack of any summary section on "margin of safety", a factor that is supposed to be explicitly considered in setting a NAAQS. This is an issue that is an especially troubling one for ozone, where the Staff Paper acknowledges that health effects that it judges to be adverse are expected to occur in large numbers of people living in the 12 MSAs who are considered to be susceptible, at least for the 74/4 and 70/4 options. 3) The section on Margin of Safety in the Agency's NAAQS proposal should also address the fact that the clinical laboratory exposures of healthy human volunteers provided much of the quantitative exposure-response information that guided the selection of the NAAQS options that were presented in the Jan. 2007 final draft, involved exposure to ozone alone. 4) While ozone is an appropriate indicator species for the Ozone and Photochemical NAAQS, it must be remembered that there is evidence, cited in the Staff Paper, from the childrens' camp studies and studies of workers and adults engaged in recreational exercise outdoors, that the ambient air mixtures produce greater responses than those seen in the studies of children and healthy adults in chambers with exposures to ozone alone. Thus, the chamber responses are likely to provide underestimates of the responses to ozone in ambient air mixtures. 5) For the reasons summarized above, I consider the effects that are estimated for the 74/4 level to be too high for a NAAQS that provides an acceptable degree of public health protection. I recognize that any limit lower than 70/4 is not technologically feasible for the U.S. in the near future, and that the costs of implementation for a still lower limit would likely exceed the public health benefits. 6) I believe that the issues that are raised above that deal with the adequacy of the protection that can be provided by the alternate NAAQS levels and the extent of a Margin of Safety, if any, at these levels, should be more thoroughly and explicitly addressed in the Federal Register proposal for a revised Ozone NAAQS than they were in the Final Draft of the Ozone Staff Paper. ~_ "'' ~` C-20