The association between daily mortality and ambient air particle pollutionin Montreal, Quebec 2. Cause-specific mortality

This study was undertaken to determine whether variations in concentrations of particulates in the ambient air of Montreal, Quebec, during the period 1984 to 1993, were associated with daily variations in cause-specific daily mortality. Fixed-site air pollution monitors in Montreal provided daily me an levels of various measures of particles and gaseous pollutants. Total su lfate was also measured daily (1986-1993) at a monitoring station 150 km so utheast of the city (Sutton, Quebec). We used coefficient of haze (COH), ex tinction coefficient, and sulfate from the Sutton station to predict fine p articles and sulfate from fine particles for days that were missing. We est imated associations between cause-specific mortality and PM2.5, PM10, predi cted fine particles and fine sulfate particles, total suspended particles, coefficient of haze, extinction coefficient, and total sulfate measured at the Sutton station. We selected a set of underlying causes of death, as rec orded on the death certificates, as the endpoint and then regressed the log arithm of daily counts of cause-specific mortality on the daily mean levels for the above measures of particulates, after accounting for seasonal and subseasonal fluctuations in the mortality time series, non-Poisson dispersi on, weather variables, and gaseous pollutants. We found positive and statis tically significant associations between the daily measures of ambient part icle mass and sulfate mass and the deaths from respiratory diseases and dia betes. The mean percentage change in daily mortality (MPC), evaluated at th e interquartile range for pollutants averaged over the day of death and the preceding 2 days, for deaths from respiratory diseases was MPCOH = 6.90% ( 95% CI: 3.69-10.21%), MPCPredicted (PM2.5) = 9.03% (95% CI: 5.83-12.33%), a nd MPCSutton sulfate = 4,64% (95% CI: 2.46-6.86%). For diabetes, the corres ponding estimates were MPCCOH = 7.50% (95% CI: 1.96-13.34%), MPCPredicted ( PM2.5) = 7,59% (95% CI: 2.36-13.09%), and MPCSutton sulfate = 4.48% (95% CI : 1.08-7.99%). Among individuals older than 65 years at time of death, we f ound consistent associations across our metrics of particles for neoplasms and coronary artery diseases. Associations with sulfate mass were also foun d among elderly persons who died of cardiovascular diseases and of lung can cer. These associations were consistent with linear relationships. The asso ciations found for respiratory diseases and for cardiovascular diseases, es pecially in the elderly, are in line with some of the current hypotheses re garding mechanisms by which ambient particles may increase daily mortality. The positive associations found for cancer and for diabetes may be underst ood through a general hypothesis proposed by Frank and Tankersley, who sugg ested that persons in failing health may be at higher risk for external ins ults through the failure of regulating physiological set points. The associ ation with diabetes may be interpreted in light of recent toxicological fin dings that inhalation of urban particles in animals increases blood pressur e and plasmatic levels of endothelins that enhance vasoconstriction and alt er electrophysiology. Further research to confirm these findings and to det ermine whether they are causal is warranted. (C) 2001 Academic Press.