Differences in Estimated Effects of Air Pollution by Decedent Age Groups

REBECCA KLEMM (1) Eddie Thomas (1) Ron Wyzga (2)

(1) Klemm Analysis Group, Inc. (2) EPRI

     Abstract Number: 404
     Last modified: November 9, 2009

Abstract
Background and Objective
Prior studies have shown that estimated effects of pollution on human mortality are greater among decedents at least 65 years of age. This research investigates differences in estimated effects by subgroups of decedents at least 65 years of age: 65 – 84 and 85 or greater years of age.

Methods
Generalized linear models were developed in S-Plus to estimate the effects of air pollution on daily, non-accidental deaths among four major counties in Atlanta, GA between 1998 and 2006. We examined various scenarios using sub-populations among elderly decedents and five categories of non-accidental causes of death: all non-accidental, circulatory, respiratory, cancer and other non-accidental. Daily mortality counts were associated with time smoothed via knots placed every 30 days, temperature and dew point smoothed via knots placed at the 25th and 75th percentiles, day of the week indicators, and average of the current and prior day's measure of air pollution. Air pollution includes PM2.5 as well as its components and trace gases.

Results
Overall, 64 percent of the decedents at least 65 years of age were less than 85 years of age at the time of death. The proportion varied by cause of death: 60 percent of circulatory causes, 65 percent of respiratory causes, 81 percent of cancer causes and 56 percent of other non-accidental causes of the decedents at least 65 years of age were less than 84 (65-84) years of age.

Although decedents at least 85 years of age show a larger positive estimated effect of PM2.5 the estimated effect does not meet a t-value of 1.96 or greater. Estimated effects for CO2 and NO2 are higher for decedents less than 84 years of age than for decedents at least 85 years of age. The greatest differences in estimated effects between the two age subgroups were illustrated by EC and OC: larger positive estimated effects with t-values greater than 1.96 for decedents under 85 years of age and t-values of less than 1.0 for decedents at least 85 years of age.

Results of comparable models regarding other US cities will be compared to those of Atlanta.

Conclusion
Particular pollutants may impact human health differently among decedent age groups. Although it is generally understood that air pollution has more of an effect on mortality in elderly populations, certain sub-populations may be more susceptible to particular types of pollution than others. The impact of air pollution on death from certain health conditions may not be homogeneous among decedents at least 65 years of death.