Air Pollution, Mortality, and Weather

Daily deaths for the years 1960 through 1964 in New York city (excluding April to September) were studied in relation to SO2, smoke shade, temperature deviations from normal, wind speed, sky cover, and rainfall. To eliminate seasonal effects. deaths were expressed as deviations from a five-year “normal.” SO2 was related to mortality to a greater degree when smoke shade was held constant than was smoke shade when SO2 was held constant and was, therefore, used as an index of air pollution. Evidence suggests that this increase in mortality was associated with increased SO2 independent of weather factors studied. The difference in mean number of daily deaths on days with mean SO2 levels of 0.20 ppm or less compared with days having mean SO2 levels of 0.40 ppm or more is estimated to have been 10 to 20 deaths per day.