Short term effect of air pollution on mortality in Polish urban populations--what is different?

STUDY OBJECTIVE: To assess, within the multinational European Community funded APHEA project, the relationship between daily ambient air pollution with sulphur dioxide (SO2) and black smoke (BS) and the daily number of deaths from all causes except external, from cardiovascular diseases, and from respiratory diseases taking into account several possible confounding factors. DESIGN: Time series analysis with the application of Poisson regression to the counts of daily number of deaths from selected causes over several years. Data were obtained from the computer files of individual death records in four Polish cities. Criteria developed for all the centres participating in the project were applied to the process of model building. SETTING: Four Polish cities - Cracow (period 1977-89), Lodz (1977-90), Poznan (1983-90), and Wroclaw (1979-89). SUBJECTS: Permanent residents of the cities who died in a city of residence or in a surrounding region during the study period. MAIN RESULTS: There were significant positive associations between mortality from all causes excluding external ones and SO2 and BS in Cracow and in Lodz and between mortality from cardiovascular diseases and SO2 in Cracow alone. In other cities the association was either non-significant or significant but in the opposite direction. No significant positive association was found between respiratory deaths and these pollutants. CONCLUSIONS: Short term effect of air pollution on mortality in Polish urban population cannot be ignored. However, differences observed between the cities suggest that the association may be not so straightforward and therefore there is a need of further studies to identify additional factors that may modify and confound the association.