Health Impacts from Climate-Change Induced Changes in Ozone Levels in 85 United States Cities

Abstract

Introduction: Global warming could impact human health through multiple pathways, including the shifting of ecosystems and associated vector-borne diseases, changes to water resources, and heat-related mortality. As the chemical reactions that form tropospheric ozone are temperature dependent, global warming could raise ambient ozone levels. This could subsequently result in an increase in ozone-associated health effects. Methods: Global warming’s potential effects on ambient ozone concentrations were modeled for 85 cities in the Eastern U.S. for five summers representing current climatic conditions (1993–1997) and five summers representing possible future climatic conditions (2053–2057) using the IPCC A-2 climate scenario and current emissions levels. A linked climate/air quality modeling system developed by the New York Climate and Health Project was used to derive ozone concentrations under climate change. The modeling system included the GISS global climate model (National Aeronautics and Space Administration), MM5 meteorological model (Penn State/United Corporation for Atmospheric Research), CMAQ air quality model (U.S. Environmental Protection Agency), and SMOKE emissions processor (MCNC Supercomputing Center). The difference in ozone levels predicted by the model was combined with concentration-response functions from epidemiological studies and current mortality data to estimate the changes in mortality associated with the changes in ozone concentrations. Results: Preliminary results indicate that the climate change scenario would produce higher ambient ozone levels, with an average increase of 2.8 ppb in the daily average ozone (range −0.1 to 6.4 ppb). The daily 1-hour and 8-hour maximums increased for all 85 cities, with an average increase of 4.6 and 4.2 ppb, respectively. Results were not spatially uniform with some cities experiencing larger increases than others. Louisville, Kentucky had the largest elevation in ozone levels with an increase of 9.6 ppb in the daily 1-hour maximum. Exceedances of regulatory standards would also increase under the climate change scenario. For instance, Cincinnati, Ohio is estimated to experience 12 more days exceeding the 8-hour standard under the future climatic conditions. The corresponding health effects will be estimated. For example, elevated ozone concentrations from global warming in the 2050’s is estimated to produce a 0.25% increase (95% confidence interval 0.14, 0.36%) in daily mortality, averaged across the cities, with Louisville experiencing a 0.52% increase (0.30, 0.75%) (based on meta-analysis by Thurston and Ito, 2001). Discussion: This research demonstrates global warming’s potential impact on health through the pathway of elevated ambient ozone levels. This provides evidence for decision.