Modelling the effects of urban morphology, traffic and pedestrian dynamics on students’ exposure to air pollution

Abstract

The United Nations Environment Programme stated that the human exposure to air pollutants primarily emitted by road traffic is associated to nearly 0.8 million premature deaths annually, especially in sensitive groups such as children. This paper evaluates the individual exposure of students in a Portuguese town accounting for their walk to school and the time spent in the classroom. The analysis was carried out for 8 hypothetical walking routes that were tracked and profiled with a GPS. Ambient air pollutant concentrations of CO and PM10 were simulated with a Computational Fluid Dynamics (CFD) model, while indoor air pollutant levels were estimated for different classrooms using the simulated outdoor concentrations and a mass transfer approach. Results show that the individual exposure of pedestrians in a city is extremely spatially dependent, as a consequence of air pollutant dispersion patterns, leading to significant disparities between the children’s exposure. A tendency between the orientation of classroom’s façade and resulting exposure was not found, but in the case of the outdoor exposure the children coming from N and NE have the highest values. The variability of the estimated exposure values shows the magnitude of the error that can be committed when using a single value of air quality as a surrogate of air pollution exposure. This problem can be overcome by using building-resolving CFD models that provide an accurate and detailed understanding of how human behaviour and habits can affect the exposure of urban citizens and ultimately their health.