The Modifying Effects of Individual Socioeconomic Status on Mortality Risk Associated with Air Pollution:

SM2-PD-05 Introduction: While socioeconomic inequity is a continuous concern in public health, its role in modifying air pollution effects is now a major research interest. We will explore whether individuals with low socioeconomic status (SES) are more susceptible to the acute effects of ambient air pollution than those with high SES. Methods: The study included 24,656 Hong Kong Chinese who died of natural causes at the age of 30 or above in 1998. Information on individual SES as well as lifestyle and physical status was obtained by interviewing the informants via a standardized questionnaire. Based on physical demands in jobs, occupational classes were categorized into 3 groups: blue-collar, jobless, and white-collar. Levels of education were classified into no formal education, primary education, and secondary or higher education. Two types of housing were considered: self-owner and public estate. Poisson regression was performed to assess excess risks per 10 μg/m3 increase of air pollutant (ER) for each SES subgroup. The differences in ER between SES subgroups were estimated by inclusion of interaction terms (ie, indicator of SES times concentration of each air pollutant) in the model for data with all subgroups put together. Case-only logistic regression was used as sensitivity analysis with adjustment for potential confounding by lifestyle and physical status. Results: We found that the effects of air pollution were significantly associated with types of housing, occupational classes, and levels of education. The differences in ER between people living in public estate and those owning private house were 1.63% (95% CI, 0.02%–3.61%) and 1.65% (0.45%–2.84%) for NO2 and PM10, respectively. The highest effects of air pollution were observed in those with primary education among 3 education subgroups, and the differences in ER were significant for NO2, O3, and PM10 (P < 0.05) but not for SO2. ER for all pollutants were significantly greater in blue-collar workers compared with the other 2 occupational classes (P < 0.05). The results changed slightly but in general remained significant and were consistent after adjustment for potential confounders. Discussion and Conclusions: The result provides insight to the role of individuals’ SES in modifying the effects of air pollution on mortality.