Short-term effects of air pollution on mortality in Athens

Short-term effects of air pollution on mortality in Athens during the years 1975-1982 were studied. Daily values of sulphur dioxide (SO2) and smoke, measured by a five-station network of the National Observatory of Athens, were used as air pollution indicators. Mortality data were abstracted from the Town Registries of Athens and 18 other contiguous towns within the Greater Athens area. It was found that the adjusted daily mortality (estimated by subtracting from the observed value of mortality an 'expected' value, calculated after fitting a sinusoid curve to the empirical mortality data) depends positively and significantly on the level of SO2 (b = +0.0058, p = 0.05). This relation is independent of temperature, relative humidity, secular, seasonal, monthly and weekly variations of mortality as well as of synergistic effects of the above variables with season. No relation was found between smoke and adjusted daily mortality. An analysis for the determination of a possible threshold in the levels of SO2 causing health effects was also undertaken, by studying changes in the SO2 regression coefficients after successive deletion from the regression model of the days with the highest SO2 values. Our study shows that if there is an SO2 threshold it must lie slightly below the level of 150 micrograms/m3 (mean daily value).