Daily mortality and "winter type" air pollution in Athens, Greece--a time series analysis within the APHEA project.

STUDY OBJECTIVE

There is evidence that air pollution in Athens between 1975 and 1987 had adverse short term health effects. The short term effects of "winter type" air pollution on the daily total number of deaths are investigated for the period 1987-91 as part of the European Community multi centre APHEA project.

DESIGN

A temporal study using aggregated data is presented. The associations of the daily time series of three pollutants, sulphur dioxide (SO2), black smoke (BS), and carbon monoxide (CO) and the daily total number of deaths in the Athens area were assessed.

DATA AND METHODS

The average measurement from three stations was used for each pollutant. The daily number of deaths was recorded from the Athens Town Registry and the registries of the 18 municipalities contiguous to Athens. Data on the mean daily temperature (degree C) and relative humidity (%) were also used. Poisson autoregressive models that also allowed for overdispersion were used. Seasonality, other long term patterns, temperature, humidity, day of the week, and holidays were adjusted for. Several a priori defined pollutant transformations and lags were investigated. One day measurements as well as cumulative exposure effects were assessed. Effect modification by season as well as among pollutants was tested.

MAIN RESULTS

Linear terms were used for all pollutants. The magnitude of the effect was greater at lags 0 for CO and 1 for BS and SO2 gradually declining after lag 1. For an increase of 100 micrograms/m3 in SO2 and BS there were corresponding increases (95% CI) of 12% (7%, 16%) and 5% (3%, 8%) in the daily total numbers of deaths, while for an increase of 10 micrograms/m3 in CO the increase (95% CI) in the daily total number of deaths was 10% (5%, 15%). A significant interaction of the effects of SO2 with season were found. The strongest effect was observed during the winter, when higher levels of SO2 were observed. A stronger effect of SO2 on the daily total number of deaths was observed when the levels of BS were > 100 micrograms/m3.

CONCLUSIONS

These results strengthen the evidence of a causal association between ambient particle, SO2, or CO levels in the air and the daily total number of deaths and points to an important public health issue for the Athens population.