The risk of dying on days of higher air pollution among the socially disadvantaged elderly

Rationale

The estimated mortality rate associated with ambient air pollution based on general population studies may not be applicable to certain subgroups.

Objective

The objective of the present study was to determine the influence of age, education, employment status and income on the risk of mortality associated with ambient air pollution.

Methods

Daily time-series analyses tested the association between daily air pollution and daily mortality in seven Chilean urban centers during the period January 1997–December 2007. Results were adjusted for long-term trends, day-of-the week and humidex.

Results

Interquartile increases in particulate matter (PM₁₀ and PM_2.5), sulphur dioxide, nitrogen dioxide, carbon monoxide, and elemental and organic carbon were associated with a 4–7% increase in mortality among those who did not complete primary school (p<0.05) vs. 0.5–1.5% among university graduates (p>0.05). Among those at least 85 years of age respective estimates were 2–7%. However, among the elderly who did not complete primary school, respective estimates were 11–19% (p<0.05). The degree of effect modification was less for income and employment status than education, and sex did not modify the results.

Conclusion

The socially disadvantaged, especially if elderly appear to be especially susceptible to dying on days of higher air pollution. Concentrations deemed acceptable for the general population would not appear to protect this susceptible subgroup.