A probabilistic assessment of health risks associated with short-term exposure to tropospheric ozone

Overview of ozone human exposure and health risk analyses used in the U.S. EPA's review of the ozone air quality standard

“…Reports by Johnson et al (1996) and Whitfield et al (1996) present results of earlier exposure and risk assessments, respectively. The earlier ozone risk assessment was similar to the one reported here in that both assessments used results from the pNEM/03 exposure model to estimate ozone exposures.…”

“…(See Appendix A of Whitfield et al 1996 for details of this process.) The process starts with data from the laboratory experiments described earlier.…”

“…Thurston (1995) and (2) excess admissions attributable to exposures at ozone levels >0.04 ppm. For example, for the current standard (l-h, 1 expected exceedance, 0.124 ppm), the median number of admissions of asthmatics for any respiratory-related reason is 14,800 [which is approximately equal to 15,000 (the median of total admissions in the As-Is scenario) minus 388 (the median number of excess admissions in the As-Is scenario attributable to ozone exposure at concentrations greater than the estimated 0.04 ppm background level; from Whitfield et al 1996) plus 139 (the median number of excess admissions associated with attainment of the current standard [scenario 1124] for ozone exposures at concentrations > 0.04 ppm).…”

“…f Admissions of asthmaticsfor any respiratory-relatedreason; for scenarioi, based on estimatesof all admissions and excess admissions attributable to ozone levels >0.04 ppm for the As-Is scenario, and estimatesof excess admissions attributableto ozone levels >0.04 ppm for scenario i (e.g., for scenario 1124:14,800 x 15,000-388 + 139). Fifteen thousand is the number of admissions of New York City asthmatics for any respiratory-relatedreason during the 1988-1990ozone seasons (Thurston 1995);388 is the median number of excess admissionsassociatedwith the As-Is scenario (Whitfield et al 1996);and 139 is the median number of excess admissionsfor scenarioS with a backgroundozone level of 0.04 ppm. The corresponding0.05-and 0.95-fractileestimates for excessadmissions associatedwith the As-Is scenario,which are neededto calculatethe 0.05-and 0.95-fractileestimates for the third case (all admissions), are 132 and 644, respectively (Whitfieldet al 1996).…”

“…With respect to risk results, Whitfield et al (1996) discussed a number of limitations of exposure-response modeling and risk modeling that remain applicable. These include the following issues:…”