Updated Global Estimates of Respiratory Mortality in Adults ≥30Years of Age Attributable to Long-Term Ozone Exposure

Abstract

Background: 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 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.

Objectives: We estimated the global burden and spatial distribution of respiratory mortality attributable to long-term O₃ exposure in adults ≥30y of age using updated effect estimates from the ACS CPS-II cohort.

Methods: We used GEOS-Chem simulations (2×2.5º grid resolution) 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 and minimum risk thresholds set at the minimum or fifth percentile of O₃ exposure in the most recent CPS-II analysis. These estimates were compared with attributable mortality based on the earlier CPS-II analysis, using 6-mo average exposures and risk thresholds corresponding to the minimum or fifth percentile of O₃ exposure in the earlier study population.

Results: We 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.

Conclusions: 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. https://doi.org/10.1289/EHP1390.

Figure 1.

Estimated long-term ${\mathrm{O}}_3$-exposure attributable respiratory deaths in 2010 for adults $\ge 30\mathrm{y}$ of age. Units are attributable deaths per 100,000 people, and estimates were derived using the T2016 relative risk estimate [$\text{HR}=1.12$ (95% CI: 1.08, 1.16), adjusted for near-source and regional ${\text{PM}}_{2.5}$, and ${\text{NO}}_2$ exposure] and annual average daily maximum 8-h ${\mathrm{O}}_3$ concentration as the ${\mathrm{O}}_3$ exposure metric, with a low-concentration cutoff set at the minimum exposure in the Turner et al. (2016) cohort ($26.7\text{ppb}$) (Map Data: © EuroGeographics for the administrative boundaries).

Figure 2.

Spatial distribution of changes in estimated long-term ${\mathrm{O}}_3-\text{attributable}$ respiratory deaths when using the J2009 relative risk estimates [$\text{HR}=1.04$ (95% CI: 1.013, 1.067), adjusted for total ${\text{PM}}_{2.5}$ exposure] and 6-mo daily maximum 1-h concentration as the ${\mathrm{O}}_3$ exposure metric ($33.3-\text{ppb}$ low-concentration cutoff), and T2016 relative risk estimates [$\text{HR}=1.12$ (95% CI: 1.08, 1.16), adjusted for near-source and regional ${\text{PM}}_{2.5}$, and ${\text{NO}}_2$ exposure] and annual average daily maximum 8-h concentration as the ${\mathrm{O}}_3$ exposure metric ($26.7-\text{ppb}$ low-concentration cutoff). (a) shows the absolute difference in attributable respiratory deaths per 100,000 people estimated using the J2009 and T2016 relative risk estimates. (b) shows the percent of T2016-based attributable respiratory death estimates accounted for by J2009-based attributable respiratory deaths estimates (colder colors indicate a smaller increase in estimated ${\mathrm{O}}_3-\text{attributable}$ respiratory deaths when calculated using the T2016 relative risk estimate, warmer colors indicate a larger increase). (c) shows the percent decrease in the magnitude of the long-term ${\mathrm{O}}_3$ exposure metric when using the annual average daily maximum 8-h metric (relevant for T2016 relative risk estimates), compared with the maximum 6-mo average daily maximum 1-h metric (relevant for J2009 relative risk estimates). Gray areas in each panel indicate those grids where the 6-mo or annual ${\mathrm{O}}_3$ exposure metric was below the LCC, and therefore no ${\mathrm{O}}_3-\text{attributable}$ respiratory deaths were estimated (Map Data: © EuroGeographics for the administrative boundaries).