ASSOCIATION BETWEEN AMBIENT CARBON-MONOXIDE LEVELS AND HOSPITALIZATIONS FOR CONGESTIVE-HEART-FAILURE IN THE ELDERLY IN 10 CANADIAN CITIES

We examined the role that ambient air pollution plays in exacerbating cardiac disease by relating daily fluctuations in admissions to 134 ho spitals for congestive heart failure in the elderly to daily variation s in ambient concentrations of carbon monoxide, nitrogen dioxide, sulf ur dioxide, ozone, and the coefficient of haze in Canada's 10 largest cities for the 11-year period 1981-1991 inclusive. We adjusted the hos pitalization time series for seasonal, subseasonal, and weekly cycles and for hospital usage patterns. The logarithm of the daily high-hour ambient carbon monoxide concentration recorded on the day of admission displayed the strongest and most consistent association with hospital ization rates among the pollutants, after stratifying the time series by month of year and adjusting simultaneously for temperature, dew Fei nt, and the other ambient air pollutants. The relative risk for a chan ge from 1 ppm to 3 ppm, the 25th and 75th percentiles of the exposure distribution, was 1.065 (95% confidence interval = 1.028-1.104). The r egression coefficients of the other air pollutants were much more sens itive to simultaneous adjustment for either multiple pollutant or weat her model specifications.