Impact of urban form on concentration of air pollutants within street canyons at pedestrian level

Recent estimates published by WHO reported that in 2018 air pollution caused eight million premature deaths worldwide. The same report highlighted that outdoor air pollution was responsible for 4.2 million deaths. This implies that further efforts and mitigations are needed to reduce individuals’ exposure to harmful air pollutants. In this respect, governments around the world developed and published a number of air quality plans and frameworks. However, they either ignored or paid less attention to microclimate and urban form attributes and their impact on air pollution concentrations or dispersion in urban spaces, particularly within urban street canyons.
Considering the above, this study postulates that there is a correlation between urban form and air quality. Therefore, the core focus of this thesis is to investigate this relationship in greater depth and to propose a set of recommendations that can create a desirable microclimate within various urban street canyons capable of mitigating air pollution concentrations and thereby reducing its negative impact on human health. This thesis employs a variety of methods, including fieldwork, computational modelling, and correlation analysis, to measure the influence of various street canyon configurations on the concentration of air pollution.
The findings of this study confirmed several correlations between air pollution concentrations and urban form within street canyons. This study generated new knowledge on air pollution and microclimate behaviour within various street canyons. It provided recommendations for 30 distinct urban street canyon configurations in order to increase dispersion and protect pedestrians from harmful levels of air pollution. It also offered much needed knowledge and recommendations for urban designers and planners to consider to make informed design decisions to encourage greater dispersion of air pollution within various urban street canyons, particularly in areas with high pedestrian traffic to reduce and limit public exposure to harmful air pollution.