A Comparison of Particulate Matter Exposures Between a Student’s Private Vehicle and Public Bus Transit Commutes

Daily commuters of public transportation and private vehicles are exposed to a wide range of traffic-related air pollution (TRAP). However, evidence of differences between commuting method has been building. In this study, the personal ultrafine particle (UFP) and black carbon (BC) air pollution exposures of a high school student were measured during their daily commute. In total, 39 commutes made between the student’s home and school were measured. These commutes were either by bus or private vehicle. Data was analysed using box plots and T-tests of statistical significance. Levels of BC were not significantly higher on buses (mean(SD) = 849(645) ng/m 3 ) than cars (650(689) ng/m 3 ) (p-value = 0.199). For UFP, levels were significantly higher for bus commutes (9393(6923) pts/cm 3 ) than those of private vehicle (4234(6446) pts/cm 3 ) (p-value = 0.045). Our findings suggest that bus commuters may experience higher exposure to UFP relative to private vehicle commuters. The higher UFP exposure may be accounted by the fact that city buses can have a higher air exchange rate due to the constant opening of doors.  As well, buses are mainly diesel vehicles, which are a strong source of UFP.