Urban ambient air pollution and daily mortality in Salamanca (Spain)

Several new studies published over the past decade have demonstrated a link between ambient air pollution and several adverse effects on human health even at the lower concentrations typically observed in North America and Europe today, suggesting that air pollution may pose a risk to public health. The effects on human health of gaseous air pollutants, such as ozone, nitrogen oxides, sulphur dioxide, and carbon monoxide, are not as weld established. Our study set out to determine the possible relations of variations in pollutants on mortality in the city of Salamanca (Spain), taking into account the possible confounding effect of other atmospheric variables. The study was based on daily mortality data (ICD-9 codes:390-459 cardiovascular; 460-519 respiratory; 520579 digestive causes) from Spanish Institute of Statistics, and meteorological and air pollution data from the Municipal Automatic Air Pollution Monitoring, from 1995 to 1997. Since we were interested in the acute effects of air pollution on mortality, the time series of daily counts of deaths were smoothed to remove trend, seasonal and sub-seasonal cycles. A minimum set of weather predictors (atmospheric variables and time lags) was selected using forward inclusion stepwise regression methods and these were used to produce a multivariate model of the different causes of mortality. A significant association was found among ozone, sulphur dioxide, mean temperature, relative humidity, solar radiation and mortality.