Influences of black carbon levels in the micro-environment inside urban buses

Sammanfattning: Several studies indicate that the cabin of buses is the micro-environment in urban public transport where commuters might be the most exposed to black carbon. Black carbon functions as an indicator of air pollution, which is shown to have harmful impacts on the human body and because it may lead to cancers, systemic inflammation, and cardiovascular diseases, it is listed as one of the top causes to premature deaths, globally. This makes it important to understand what mechanisms there are to the elevated levels of pollutants in urban buses, and by performing mobile in-cabin measurements of black carbon concentrations during 55 bus trips in the public transport system of Stockholm, this study have tried to assess the influences from using different types of fuel, self-contamination, meteorological conditions and driving factors. Although concentrations showed large variability both spatially and temporally, idling at intensely trafficked bus stops showed an average increase of concentrations by 42% compared to the overall average. The risk of allowing increased number of pollutants at bus stops increases with idling for longer time and having the doors open meanwhile.