Relative risk estimates for long-term ozone (O3) exposure and respiratory mortality from the American Cancer Society Cancer Prevention Study II (ACS CPS-II) cohort have been previously used to estimate global O3-attributable mortality in adults. Updated relative risk estimates are now available for the same cohort based on an expanded study population with longer follow-up. The study estimates the global burden and spatial distribution of respiratory mortality attributable to long-term O3 exposure in adults over 30 years of age.

Simulations using the GEOS-Chem atmospheric chemical transport model on 2 × 2.5 degree grid resolution were made to estimate annual O3 exposures, and estimated total respiratory deaths in 2010 that were attributable to long-term annual O3 exposure based on the updated relative risk estimates along with minimum risk thresholds set at the minimum or fifth percentile of O3 exposure in the most recent CPS-II analysis.

These estimates were then compared with attributable mortality based on the earlier CPS-II analysis, using 6-monthly average exposures and risk thresholds corresponding to the minimum or fifth percentile of O3 exposure in the earlier study population.

The results show an estimated 1.04–1.23 million respiratory deaths in adults attributable to O3 exposures using the updated relative risk estimate and exposure parameters, compared with 0.40–0.55 million respiratory deaths attributable to O3 exposures based on the earlier CPS-II risk estimate and parameters. Increases in estimated attributable mortality were larger in northern India, southeast China, and Pakistan than in Europe, eastern United States, and northeast China.

These findings suggest that the potential magnitude of health benefits of air quality policies targeting O3, health co-benefits of climate mitigation policies, and health implications of climate change-driven changes in O3 concentrations, are larger than previously thought.

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