Simulation of NO2 commute exposure – Investigation of its contribution to total exposure and comparison of air pollution models

Abstract

Background: Little is known about the commute exposure to traffic-related air pollution of a general population and its contribution to total daily exposure. Aims: Our aim is to estimate population based NO2 exposure during commute in Basel, Switzerland, using detailed information on commute behavior and commute route and three air pollution models of varying spatial resolutions. Methods: Firstly, trips between home and work places are simulated by means of a Geographic Information System model using extensive time-activity information from the Swiss 2010 Microcensus database, which provides temporally and spatially resolved data on travel behavior. Secondly, exposure to air pollution is estimated by combining the commute patterns and home and work locations with estimates from air pollution models. Thirdly, the contribution of time-weighted commute exposure to annual NO2 estimates is assessed. Simulating variations of commute patterns (e.g. avoiding main roads) allows us to test scenarios of change in commute behavior on exposure distribution. Finally, three air pollution models (land use regression model, a high and low resolution dispersion model) are evaluated for estimating commute and total NO2 exposures as a marker of traffic-related air pollution in epidemiological exposure assessment studies. Results: The main mode of travel to work in Basel was public transport (52%), followed by car (18%) and bike (17%).Within the Basel area, the average daily time spent in transit between home and work locations was 52 ±37min. Our first results reveal significantly higher average NO2 concentrations during commute (28.2µg/m³, range: 11.6-54.5µg/m³) than at home outdoor locations (25.5µg/m³, range: 11.8-43.4µg/m³). Conclusions: The results will be further examined and contribution of commute to total daily exposure will be quantified. The study will contribute to a better understanding of population commute exposure to NO2 and its relevance in long-term epidemiological exposure assessments.