Synergistic effects of traffic-related air pollution and exposure to violence on urban asthma etiology.
BACKGROUND
Disproportionate life stress and consequent physiologic alteration (i.e., immune dysregulation) has been proposed as a major pathway linking socioeconomic position, environmental exposures, and health disparities. Asthma, for example, disproportionately affects lower-income urban communities, where air pollution and social stressors may be elevated.


OBJECTIVE
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.


METHODS
We developed geographic information systems (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, Massachusetts, between 1987 and 1993, using monthly nitrogen dioxide 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 1-SD (4.3 ppb) increase in NO(2) exposure solely among children with above-median ETV [odds ratio (OR) = 1.63; 95% confidence interval (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 NO(2) 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.
Department of Environmental Health, Harvard School of Public Health, Boston, MA 02215, USA. jcloughe@hsph.harvard.edu
Jane E
JE
Clougherty
Jonathan I
JI
Levy
Laura D
LD
Kubzansky
P Barry
PB
Ryan
Shakira Franco
SF
Suglia
Marina Jacobson
MJ
Canner
Rosalind J
RJ
Wright
D000393:Air Pollutants / Q000032:analysis / Q000633:toxicity; D000397:Air Pollution / Q000009:adverse effects* / Q000032:analysis; D001249:Asthma / Q000453:epidemiology / Q000209:etiology*; D001900:Boston / Q000453:epidemiology; D002648:Child; D002947:Cities; D004781:Environmental Exposure / Q000009:adverse effects* / Q000032:analysis; D005260:Female; D006801:Humans; D008297:Male; D009585:Nitrogen Dioxide / Q000032:analysis / Q000633:toxicity; D013315:Stress, Psychological / Q000150:complications; D014505:Urban Population; D001335:Vehicle Emissions / Q000633:toxicity; D014754:Violence
D000393:Air Pollutants; D001335:Vehicle Emissions; D009585:Nitrogen Dioxide