Socioeconomic status, particulate air pollution, and daily mortality: Differential exposure or differential susceptibility

Abstract

Background Short‐term increases in particulate air pollution are linked with increased daily mortality and morbidity. Socioeconomic status (SES) is a determinant of overall health. We investigated whether social class is an effect modifier of the PM₁₀ (particulate matter with diameter 10 daily data were available from two urban monitoring sites. A case‐crossover analysis was utilized in which control days were selected according to the time stratified approach (same day of the week during the same month). Conditional logistic regression was used. Results Due to the social class distribution in the city, exposure to traffic emissions was higher among those with higher area‐based income and SES. Meanwhile, people of lower social class had suffered to a larger extent from chronic diseases before death than more affluent residents, especially diabetes mellitus, hypertension, heart failure, and chronic obstructive pulmonary diseases. Overall, PM₁₀ (lag 0–1) was strongly associated with mortality (1.1% increase, 95%CI = 0.7–1.6%, per 10 µg/m³). The effect was more pronounced among persons with lower income and SES (1.9% and 1.4% per 10 µg/m³, respectively) compared to those in the upper income and SES levels (0.0% and 0.1%, respectively). Conclusions The results confirm previous suggestions of a stronger effect of particulate air pollution among people in low social class. Given the uneven geographical distributions of social deprivation and traffic emissions in Rome, the most likely explanation is a differential burden of chronic health conditions conferring a greater susceptibility to less advantaged people. Am. J. Ind. Med. 50: 208–216, 2007.