Differential exposure of the urban population to vehicular air pollution in Hong Kong.

This study aims to characterize the spatial variations in, and examine the influence of socio-economic class on, the exposure of urban population of Hong Kong to air pollution from vehicular sources. Hong Kong provides a unique and interesting case for an in-depth study of environmental inequality because of its dense environment and housing provision mechanism through which about half of the population is accommodated in public housing estates provided by the government. To estimate the exposure of the urban population to vehicular air pollution, the IMMIS(net) air dispersion model developed for city-wide air quality assessment was used. The annual mean concentrations of CO, NO(x), SO(2) and PM(10) were estimated for various assessment points of 275 public and 295 private building groups. The results show more pronounced inequality among residents living in private than in public housing estates. Elderly people and those of lower socio-economic status were found to be exposed to relatively higher levels of vehicular air pollution compared with groups of higher socio-economic status. However, when all the residents in Hong Kong were pooled together for analysis, no distinct class-biased patterns were found. This could be ascribed to the housing provision mechanism, in which less well-off people are accommodated in public housing estates where the air quality is relatively better. This study highlights the importance of government intervention in housing provision, through which the deprived groups in Hong Kong are inadvertently more protected from air pollution exposure.