Editorial Indoor and Built Environment Indoor Built Environ 2012;21;3:355–357 Time-Series Numerical Simulation of Wind Flow Within Urban Canopy Layer and Its Integration Effect for Prediction of Pollutant Concentration Variation

Source analysis shows that motor vehicle exhausts are the major pollutant emission sources in urban atmosphere. Street canyons are areas where vehicle exhausts are most frequently discharged into and where urban residents could be subjected to exposure of likely high concentra-tions of these emissions. The spread of pollutants in urban street canyons would affect the neighbourhood environ-ments and indoor air qualities [1]. The numerical simula-tion and in situ investigation of fine particle dispersion in an actual deep street canyon in Hong Kong has been reported [2]. Motor vehicle emissions in urban street canyons are thus serious threats to the health of pedestrians [3]. The link between certain respiratory health issues, such as the increase in asthma cases and mortality, and traffic-related pollutants, such as suspende