The Exposure-Response Curve for Ozone and Risk of Mortality and the Adequacy of Current Ozone Regulations Michelle L. Bell,1 Roger D. Peng,2 and Francesca Dominici2 1School of Forestry and Environmental Studies, Yale University, New Haven, Connecticut, USA; 2Department of Biostatistics, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA Abstract Time-series analyses have shown that ozone is associated with increased risk of premature mortality, but little is known about how O3 affects health at low concentrations. A critical scientific and policy question is whether a threshold level exists below which O3 does not adversely affect mortality. We developed and applied several statistical models to data on air pollution, weather, and mortality for 98 U.S. urban communities for the period 1987-2000 to estimate the exposure-response curve for tropospheric O3 and risk of mortality and to evaluate whether a "safe" threshold level exists. Methods included a linear approach and subset, threshold, and spline models. All results indicate that any threshold would exist at very low concentrations, far below current U.S. and international regulations and nearing background levels. For example, under a scenario in which the U.S. Environmental Protection Agency's 8-hr regulation is met every day in each community, there was still a 0.30% increase in mortality per 10-ppb increase in the average of the same and previous days' O3 levels (95% posterior interval, 0.15-0.45%) . Our findings indicate that even low levels of tropospheric O3 are associated with increased risk of premature mortality. Interventions to further reduce O3 pollution would benefit public health, even in regions that meet current regulatory standards and guidelines. Key words: mortality, ozone, regulations, threshold. Environ Health Perspect 114: 532-536 (2006) . doi:10.1289/ehp.8816 available via http://dx.doi.org/ [Online 23 January 2006] Address correspondence to M.L. Bell, School of Forestry and Environmental Studies, Yale University, 205 Prospect St., New Haven, CT 06511 USA. Telephone: (203) 432-9869. Fax: (203) 432-3817. E-mail: michelle.bell@yale.edu We thank J. Samet, S. Zeger, R. White, R. Brookmeyer, and D. Moffitt. Funding was provided by U.S. Environmental Protection Agency (EP05C000125, EPA-3D-6867-NAEX) , Johns Hopkins Centers for Disease Control Center of Excellence for Environmental Public Health Tracking (U50/CCU322417) , National Institute of Environmental Health Sciences (ES012054-01, P30 ES 03819) , and the Health Effects Institute (4720-RFA04-2/04-16) . Views expressed are those of the authors. The authors declare they have no competing financial interests. Received 4 November 2005 ; accepted 23 January 2006. The full version of this article is available for free in HTML or PDF formats. |