Passengers Exposure to PM2.5 in Self-polluted BRT-Diesel Operated Transport System Microenvironments

Abstract

BRT (Bus Rapid Transport) vehicles are a frequented microenvironment, it consists of exclusive lines for the transport of passengers in articulated buses. In many large cities of developing countries BRT vehicles are diesel operated buses emitting important amounts of PM2.5, a pollutant related with many health affectations. Evidence of high exposure levels have been reported onboard BRT vehicles, but detailed analysis of self-pollutions has not been developed. In this research, measurements of PM2.5 inside the BRT system of Bogota called TransMilenio were performed. Speed and location data were recorded in real-time. In-situ measurements were performed in 3 lines of the system: Av. El Dorado, Av. Caracas and Calle 80, in different seat locations inside the buses. PM2.5 concentrations above 120 µg/m3 were measured for all the cases studied. Values above the 24 h WHO (World Health Organization) recommendation were registered. Trips were determined to be between 20 to 40 minutes per passenger. A CFD (Computational Fluid Dynamics) model was implemented to simulate the exhaust emissions from the buses, 3 traffic velocities of BRT were evaluated: 20, 32 and 60 km/h. Measurements and simulation results were used to calculate the self-pollution ratios inside the vehicles. The rear of the buses was identified as the most polluted section onboard with a ratio of self-pollution about 35% average.