Exposure assessment of diesel bus emissions

摘要

Exposure to diesel exhaust emissions has been classified by international health organisations as probably carcinogenic to humans (Boffeta et al.,2001;IARC,1989).Diesel exhaust contains a complex mixture of many gases and substances known to be hazardous air pollutants (CSE,1999).In particular,diesel particulate matter (DPM) is perceived as one of the major harmful emissions produced by diesel engines (Majewski,2000).Despite considerable amount of basic research,neither the formation of DPM in the combustion chamber,nor its physico-chemical properties or human health effects are fully understood at present.Almost all of the fresh diesel exhaust particle mass is in the ultrafine particle (UFP) range.Because of their minute sizes,these particles are easily inhaled and eventually trapped within the bronchial and alveolar regions of the lung.From a population exposure point of view,air quality in a street canyon is of major importance,since the highest pollution levels and the larger targets of impact are often concentrated in this kind of setting.The so-called canyon effect results in greater health complications (Spadaro & Rabl,2001).DPM from mobile sources (buses) have a greater potential for human exposure (per g of DPM emissions) compared to combustion particulates emitted from point sources (USEPA,2002).