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

BACKGROUND: We investigated the temporal pattern of effects of summertime ozone (O(3)) in total, cardiovascular and respiratory mortality in 21 European cities participating in the APHEA-2 project, which is fundamental in determining the importance of the effect in terms of life loss. METHODS: Data from each city were analyzed 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: We found stronger effects on respiratory mortality that extend to a period of two weeks. A 10 mug/m(3) increase in O(3) was associated with 0.36% (95%CI: -0.21, 0.94) increase in respiratory deaths for lag 0 and with 3.35% (95% CI: 1.90, 4.83) for lags 0-20. We also found significant adverse health effects 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: Our 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.