Exposure to Traffic-Related Air Pollution and Risk of Development of Childhood Asthma: Results from the Born in Bradford Cohort Study

Background Childhood exposure to traffic-related air pollution (TRAP) might lead to the onset of new childhood asthma. However, there has been little study of the modifying effect of ethnicity especially among South Asians. We aimed to evaluate the relationship between residential exposure to TRAP and new-onset asthma in the multi-ethnic Born in Bradford cohort study.Methods Using validated land-use regression models developed in the ESCAPE project (European Study of Cohorts for Air Pollution Effects), we estimated annual average childhood exposures to NO2, NOx, PM2.5, PM2.5 absorbance, PM10, and PMcoarse at the birth residence. As another TRAP exposure metric, we also estimated traffic intensity within 100m buffer and traffic intensity on the nearest major road. New childhood asthma cases were identified based on diagnostic codes entered by general practitioners onto the primary care databases of the 11032 eligible children. We used Cox proportional hazard models, adjusted for key confounders, to evaluat...