The impact of seating location on black carbon exposure in public transit buses: Implications for vulnerable groups

This study assesses the differences in personal exposure to black carbon (BC) in the cabin of modern public buses in Stuttgart, Germany. We measured BC concentrations in four different seating locations, including priority seating locations, during rush hour and non-rush hour periods, and determined average exposures as well as the frequency of peak exposures. We hypothesize that the elderly and children (known to be more vulnerable to health impacts of air pollution) are exposed to higher concentrations as they are encouraged to make use of priority areas in proximity to doors in the middle of the bus, allowing for a greater flux of pollutants. We found no statistically significant difference in the mean BC concentrations between priority seating areas and other locations. However, a significant increase (+ 32%) in the frequency of BC peaks ('spikes') was observed in one priority seating area when compared to the back of the bus. Furthermore, we found that travelling during rush hour was associated with significantly higher average in-vehicle BC concentrations in all seating locations compared with off peak hours (1122 ng/m(3) or 38% higher), as well as a greater magnitude of the largest concentration spike of each trip 1295 ng/m(3) (38%). Further work may be necessary to refine most appropriate location for priority seating areas in buses and bus stops.