Synergistic Effects of Traffic-Related Air Pollution and Exposure to Violence

ISEE-274 Objective: Disproportionate life stress and consequent physiologic alteration (ie, immune dysregulation) have been proposed as a major pathway linking socioeconomic position, environmental exposures, and health disparities. Asthma, for example, disproportionately impacts lower-income urban communities, where air pollution and social stressors may be elevated. We aimed to examine the role of exposure to violence (ETV), as a chronic stressor, in altering susceptibility to traffic-related air pollution in asthma etiology. Material and Methods: We developed GIS-based models to retrospectively estimate residential exposures to traffic-related pollution for 413 children in a community-based pregnancy cohort, recruited in East Boston, MA between 1987 and 1993, using monthly NO2 measurements for 13 sites over 18 years. We merged pollution estimates with questionnaire data on lifetime ETV and examined the effects of both on childhood asthma etiology. Results: Correcting for potential confounders, we found an elevated risk of asthma with a one standard deviation (4.3 ppb) increase in NO2 exposure solely among children with above-median ETV [OR = 1.63 (95% CI = 1.14–2.33)]. Among children always living in the same community, with lesser exposure measurement error, this association was magnified [OR = 2.40 (95% CI = 1.48–3.88)]. Of multiple exposure periods, year-of-diagnosis NO2 was most predictive of asthma outcomes. Conclusions: We found an association between traffic-related air pollution and asthma solely among urban children exposed to violence. Future studies should consider socially patterned susceptibility, common spatial distributions of social and physical environmental factors, and potential synergies among these. Prospective assessment of physical and social exposures may help determine causal pathways and critical exposure periods.