Transformation of the Urban Transport Towards Low- and Zero-tailpipe Emission Technologies: Impacts on Commuter Exposure to Black Carbon, PM2.5, and UFP

RICARDO MORALES BETANCOURT, Boris Galvis, Olga Lucia Sarmiento, Universidad de los Andes

     Abstract Number: 446
     Working Group: Aerosol Exposure

Abstract
Commuters are often exposed to high concentrations of air pollutants due to its proximity to mobile sources and to other characteristics of transport micro-environments. Recent trends, driven by the need to curb air pollution and mitigate greenhouse gas emissions from transport, has accelerated the inclusion of zero- and low-tailpipe emission alternatives in many areas worldwide. These changes are expected to reduce overall commuter exposure. However, the assessments of these transformations on commuter exposure are limited by the low frequency of such studies. In this work, we use a unique data set of personal exposure concentrations measurements of equivalent Black Carbon (eBC), PM_2.5, and UFP collected over the span of 6 years to analyze the rapid changes in commuter exposure experienced by citizens of Bogota, in Colombia. The city, which has endured persistent air pollution challenges and has been shown to have extremely high levels of air pollution exposure in the past, has seen rapid adoption of cleaner public transport alternatives. Its bus-based mass transit system, which operates large-capacity buses, recently replaced over a thousand Euro-II and III diesel-powered buses with Euro-VI compressed natural gas (CNG) and DPF-equipped Euro-V diesel buses. Furthermore, a remanent of outdated diesel buses from its public transport system were replaced with the largest fleet of fully electric buses outside of China (1480 fully electric buses). Additionally, the last two years also saw the inclusion of thousands of CNG in the public transport fleet. In this work, we report our measurements of personal exposure concentrations of eBC, PM_2.5, and UFP before and after the public transit transformations. Our observations show significant reductions in the concentration of PM_2.5 and eBC, of up to 80% in some cases. Results also show persistently high levels of UFP concentration (between 65000 and 104500 #/cm3) in the near-road environment as well as in the in-cabin environment. The data set reported in this work demonstrates the rapid reductions attained by the adoption of stricter emissions standards and the observable immediate co-benefits of climate mitigation actions. Such results can be of use for other regions in the world were there has been hesitancy in adopting such technologies.