Extreme concentrations of fine particulate matter and black carbon during commute

Commuters are vulnerable to traffic air pollutants, especially to fine particulate matter (PM_2.5) and black carbon (BC) because of their proximity to on-road vehicles. Both pollutants have been extensively associated to adverse health effects (i.e., stroke, diabetes, cardiovascular and respiratory diseases, and cancer). Therefore, this work aims to investigate the extreme concentrations of PM_2.5 and BC occurrence in commuters in the megacity of São Paulo, Brazil. We carried out a field campaign measuring the commuter exposure to PM_2.5 and BC concentrations inside buses, cars and undergrounds in São Paulo during morning and evening peak-hours. We fitted an Extreme Value Distribution to the collected data to investigate the behavior of the extreme values in the different transport modes and periods of the day. The results suggest that higher concentrations of PM_2.5 and BC occur more frequently inside buses, followed by cars and undergrounds. Extreme concentrations for both pollutants are more likely to happen during morning peak-hours when compared to evening peak-hours. Our findings add further evidence that the transport mode and period of the day affect substantially the PM_2.5 and BC exposure in commuters. Furthermore, the results are quite useful for supporting urban policies that consider the improvement of the efficiency of air filtering systems inside public transport and private cars.