Identification of persons with cardiorespiratory conditions who are at risk of dying from the acute effects of ambient air particles

This study was undertaken to identify subgroups of the population susceptib le to the effects of ambient air particles. Fixed-site air pollution monito rs in Montreal; Quebec, Canada, provided daily mean levels of various measu res of particulates and gaseous pollutants. Total sulfates were also measur ed daily (1986-1993) at a monitoring station 150 km southeast of the city ( Sutton, Quebec, Canada). We used coefficient of haze (COH), extinction coef ficient, and Sutton sulfates to predict fine particles and sulfates from a fine particles model for days that were missing. We used the universal Queb ec medicare system to obtain billings and prescriptions for each Montreal r esident who died in the city from 1984 to 1993. These data were then used t o-define cardiovascular and respiratory conditions that subjects had before death. Using standard Poisson regression time-series analyses, we estimate d the association between daily nonaccidental mortality and daily concentra tions of particles in the ambient air among persons with cardiovascular and respiratory conditions diagnosed before death. We found no persuasive evid ence that daily mortality increased when ambient air particles were elevate d for subgroups of persons with chronic upper respiratory diseases, airways disease, cerebrovascular diseases, acute coronary artery disease, and hype rtension. However, we found that daily mortality increased linearly as conc entrations of particles increased for persons who had acute lower respirato ry diseases, chronic coronary artery diseases (especially in the elderly), and congestive heart failure. For this latter set of conditions, the mean p ercent increase in daily mortality (MPC) for an increase in the COH across its interquartile range (18.5 COH units per 327.8 linear meters), averaged over the day of death and the 2 preceding days, was MPC = 5.09% [95% confid ence interval (CI) 2.47-7.79%], MPC = 2.62 (95% CI 0.53-4.75%), and MPC = 4 .99 (95% Cl 2.44-7.60%), respectively. Adjustments for gaseous pollutants g enerally attenuated these associations, although the general pattern of inc reased daily mortality remained. In addition, there appeared to be a strong er association in the summer season. The positive associations found for pe rsons who had acute lower respiratory diseases and congestive heart failure are consistent with some prevailing hypotheses and may also be consistent with recent toxicologic data implicating endothelins. Further epidemiologic studies are required to confirm these findings.