Air pollution and mortality in Madrid, Spain: a time-series analysis.

OBJECTIVE

To assess the relationship, if any, between air pollutant (sulfur dioxide and total suspended particulate) levels and mortality in the city of Madrid during the period 1986-1992, controlling for weather, season, and influenza epidemics.

METHODS

Daily death counts were obtained from the Regional Mortality Registry. Pollution data were supplied by the Municipal Monitoring Network. Time-series analysis methodology was used to assess the link between non-accidental as well as circulatory- and respiratory-disease mortality, on the one hand, and mean daily concentrations of SO2 and total suspended particulate (TSP), on the other. Multivariate autoregressive integrated moving-average (ARIMA) models were used to adjust for season, temperature, relative humidity, and influenza. A sensitivity analysis was run to assess the robustness of the estimators.

RESULTS

Graphical analysis revealed a linear relationship between mortality and TSP. The relationship was logarithmic in the case of SO2. TSP lagged 1 day and SO2 lagged 3 days with an independent effect on mortality. This relationship was produced without the detection of a minimal threshold in emission values.

CONCLUSIONS

These results support the hypothesis of an association between pollution levels and mortality between 1986-1992 in Madrid. Additional measures designed to reduce pollution levels without compromising thermal comfort should be implemented.