Air pollution and mortality in Chile: susceptibility among the elderly.

Objective: The estimated mortality rate associated with ambient air pollution based on general population studies may not be representative of the effects on certain subgroups. The objective of the present study was to determine the influence of relatively high concentrations of air pollution on mortality in a general population sample and in the very elderly.

Study Design: Daily time-series analyses tested the association between daily air pollution and daily mortality in seven Chilean urban centers during 1997-2003. Results were adjusted for day of the week and humidex.

Results: Daily averaged particulate matter with aerodynamic matter < 10 microm (PM(10)) was 84.88 microg/m(3), sulfur dioxide was 14.08 ppb, and carbon monoxide was 1.29 ppb. The 1-hr maximum ozone was 100.13 ppb. The percentage increases in nonaccidental mortality associated with an increase in PM(10) equivalent to its mean were 4.53 (t-ratio 1.52) for those < 65 years and 14.03 (3.87) for those > 85 years. Respective values were 4.96 (1.17) and 8.56 (2.02) for O(3); 4.77 (2.50) and 7.92 (3.23) for SO(2); and 4.10 (2.52) and 8.58 (4.45) for CO.

Conclusion: Our results suggest that the very elderly are particularly susceptible to dying from air pollution. Concentrations deemed acceptable for the general population may not adequately protect the very elderly.