Health Risk of Exposure to Vehicular Emissions in Wind-Stagnant Street Canyons

Abstract

In recent years, most stationary sources of air pollution have been removed from urban areas; however, mobile sources are currently the direct causes of air pollution–related health problems. In particular, in the complex configurations of city buildings, the wind becomes stagnant in street canyons, which leads to higher levels of air pollution inside these areas. In this chapter, the health risks due to exposure to vehicular emissions in street canyons are discussed using a case study of field measurement and risk assessment in the street canyons of Bangkok, Thailand. The pollutants of focus are polycyclic aromatic hydrocarbons (PAHs), one of the major hazardous air pollutants from vehicular emissions. Environmental standards have not been introduced in most of the countries, and information on PAH pollution is still lacking in Asian developing countries, where the population densities and levels of traffic pollution are reported to be very high, particularly in the large cities. This chapter also includes a literature review on PAHs. The Bangkok case study of field measurement and risk assessment was conducted for roadside residents who live in possible hot spots of traffic air pollution. The field measurements provide detailed information on PAH levels, such as the diurnal variations and seasonal variations in concentrations, taking influential factors of traffic and wind conditions into consideration. The results of the risk assessment suggested that Bangkok roadside residents in the street canyons are exposed to significant levels of health risk due to PAH exposure.