Effect of the fine fraction of particulate matter versus the coarse mass and other pollutants on daily mortality in Santiago, Chile

Daily counts of non-accidental deaths in Santiago, Chile, from 1988 to 1996 were regressed on six air pollutants-fine particles (PM2.5), coarse partic les (PM10-2.5), CO, SO2, NO2, and O-3. Controlling for seasonal and meteoro logical conditions was done using three different models-a generalized line ar model, a generalized additive model, and a generalized additive model on previously filtered data. Single- and two-pollutant models were tested for lags of 1-5 days and the average of the previous 2-5 days. The increase in mortality associated with the mean levels of air pollution varied from 4 to 11%, depending on the pollutants and the way season of the year was considered. The results were not sensitive to the modeling approa ches, but different effects for warmer and colder months were found. Fine p articles were more important than coarse particles in the whole year and in winter, but not in summer. NO2 and CO were also significantly associated w ith daily mortality, as was O-3 in the warmer months. No consistent effect was observed for SO2. Given particle composition in Santiago, these results suggest that combustion-generated pollutants, especially from motor vehicl es, may be associated with increased mortality. Temperature was closely ass ociated with mortality. High temperatures led to deaths on the same day, wh ile low temperatures lead to deaths from 1 to 4 days later.