Short-term effects of carbon monoxide on mortality: an analysis within the APHEA project.

OBJECTIVES: We investigated the short-term effects of carbon monoxide on total and cardiovascular mortality in 19 European cities participating in the APHEA-2 (Air Pollution and Health: A European Approach) project. METHODS: We examined the association using hierarchical models implemented in two stages. In the first stage, data from each city were analyzed separately, whereas in the second stage the city-specific air pollution estimates were regressed on city-specific covariates to obtain overall estimates and to explore sources of possible heterogeneity. We evaluated the sensitivity of our results by applying different degrees of smoothing for seasonality control in the city-specific analysis. RESULTS: We found significant associations of CO with total and cardiovascular mortality. A 1-mg/m(3) increase in the 2-day mean of CO levels was associated with a 1.20% [95% confidence interval (CI), 0.63-1.77%] increase in total deaths and a 1.25% (95% CI, 0.30-2.21%) increase in cardiovascular deaths. There was indication of confounding with black smoke and nitrogen dioxide, but the pollutant-adjusted effect of CO on mortality remained at least marginally statistically significant. The effect of CO on total and cardiovascular mortality was observed mainly in western and southern European cities and was larger when the standardized mortality rate was lower. CONCLUSIONS: The results of this large study are consistent with an independent effect of CO on mortality. The heterogeneity found in the effect estimates among cities may be explained partly by specific city characteristics.

Acute effects of ozone on mortality from the "air pollution and health: a European approach" project.

In the Air Pollution and Health: A European Approach (APHEA2) project, the effects of ambient ozone concentrations on mortality were investigated. Data were collected on daily ozone concentrations, the daily number of deaths, confounders, and potential effect modifiers from 23 cities/areas for at least 3 years since 1990. Effect estimates were obtained for each city with city-specific models and were combined using second-stage regression models. No significant effects were observed during the cold half of the year. For the warm season, an increase in the 1-hour ozone concentration by 10 mug/m3 was associated with a 0.33% (95% confidence interval [CI], 0.17-0.52) increase in the total daily number of deaths, 0.45% (95% CI, 0.22-0.69) in the number of cardiovascular deaths, and 1.13% (95% CI, 0.62-1.48) in the number of respiratory deaths. The corresponding figures for the 8-hour ozone were similar. The associations with total mortality were independent of SO2 and particulate matter with aerodynamic diameter less than 10 mum (PM10) but were somewhat confounded by NO2 and CO. Individual city estimates were heterogeneous for total (a higher standardized mortality rate was associated with larger effects) and cardiovascular mortality (larger effects were observed in southern cities). The dose-response curve of ozone effects on total mortality during the summer did not deviate significantly from linearity.