Background/aim Asthma is a burdensome disease which has been cited as the most common chronic disease in children. Traffic-related air pollution (TRAP) may be an important exposure in its development. Bradford, UK, is a multi-ethnic deprived city suffering from asthma rates higher than national and regional averages. TRAP is of concern to local communities and is thought to contribute to the asthma burden.

Methods We estimated childhood population exposure to traffic-related NOx and NO2 at the smallest census tract level in Bradford using three validated exposure assessment methods: two novel full-chain models linking transport, two different emission models and air dispersion models and one land-use regression (LUR) model, which was developed as part of ESCAPE and which also provided estimates for other pollutants including PM2.5, PM10 and black carbon. We extracted national and local childhood asthma incidence rates and used meta-analytic exposure-response functions. We calculated the relative risk and population attributable fraction of childhood asthma attributable to each pollutant. We estimated asthma cases attributable to each pollutant and exposure combination.

Results Depending on the exposure assessment method used and the pollutant studied, the estimated TRAP-attributable asthma cases varied between 279 and 687 annually, representing between 15% to 38% of all asthma cases in the city. The health impacts estimated were sensitive to the exposure assessment method used, the pollutant selected in the analysis but, differently from the initial hypothesis, not to the vehicle emission factors used in the full-chain models.

Conclusion TRAP is estimated to cause a large, but preventable, childhood asthma burden. This study is the first study undertaking full-chain health impact assessment that considers the full-chain from source, through exposure pathway to outcome. The study also adds to the scarce literature exploring the impacts of different exposure assessments on the estimated burden of disease.