The temporal pattern of mortality responses to ambient ozone in the APHEA project

Background: The temporal pattern of effects of summertime ozone (O 3 ) in total, cardiovascular and respiratory mortality were investigated in 21 European cities participating in the APHEA-2 (Air Pollution and Health: a European Approach) project, which is fundamental in determining the importance of the effect in terms of life loss. Methods: Data from each city were analysed separately using distributed lag models with up to 21 lags. City-specific air pollution estimates were regressed on city-specific covariates to obtain overall estimates and to explore sources of possible heterogeneity. Results: Stronger effects on respiratory mortality that extend to a period of 2 weeks were found. A 10 μg/m 3 increase in O 3 was associated with a 0.36% (95% CI −0.21% to 0.94%) increase in respiratory deaths for lag 0 and with 3.35% (95% CI 1.90% to 4.83%) for lags 0–20. Significant adverse health effects were found of summer O 3 (June–August) on total and cardiovascular mortality that persist up to a week, but are counterbalanced by negative effects thereafter. Conclusions: The results indicate that studies on acute health effects of O 3 using single-day exposures may have overestimated the effects on total and cardiovascular mortality, but underestimated the effects on respiratory mortality.