Estimation of occupational and nonoccupational nitrogen dioxide exposure for Korean taxi drivers using a microenvironmental model

Occupational and nonoccupational personal nitrogen dioxide (NO2) exposures were measured using passive samplers for 31 taxi drivers in Asan and Chunan, Korea. Exposures were also estimated using a microenvironmental time-weighted average model based on indoor, outdoor and inside the taxi area measurements. Mean NO2 indoor and outdoor concentrations inside and outside the taxi drivers’ houses were 24.7±10.7 and 23.3±8.3 ppb, respectively, with a mean indoor to outdoor NO2 ratio of 1.1. Mean personal NO2 exposure of taxi drivers was 30.3±9.7 ppb. Personal NO2 exposures for drivers were more strongly correlated with interior vehicle NO2 levels (r=0.89) rather than indoor residential NO2 levels (r=0.74) or outdoor NO2 levels (r=0.71). The main source of NO2 exposure for taxi drivers was considered to be occupational driving. Interestingly, the NO2 exposures for drivers’ using LPG-fueled vehicles (26.3±1.3 ppb) were significantly lower than those (38.1±1.3 ppb) using diesel-fueled vehicle (P<0.01). Since drivers spent most of their time inside their vehicle and indoors at home, a microenvironmental model was used to estimate the personal NO2 exposure with indoor and outdoor NO2 levels of the residence, and interior vehicle NO2 levels (P<0.001). Some subpopulations, such as professional drivers, might be exposed to high NO2 levels because they drive diesel-using vehicles outdoors in Korea.