Spatiotemporal characterization of in-vehicle black carbon across different microenvironments in a Southeast Asian Megacity: a case study of Metro Manila, Philippines

Abstract:

Quantifying personal exposure to black carbon (BC) can help improve our understanding of its negative health impacts. Previous studies have identified unusually high BC concentrations in Metro Manila, Philippines, which affect millions of people every day. Of these affected populations, public utility jeepney drivers have been identified as a high-risk group, due to their long working hours, the jeepney’s open-air structure, and the inconsistent implementation of emission standards in the country. As part of the international collaborative “Transdisciplinary Approach to Mitigate Emissions of Black Carbon” (TAME-BC) project, this study quantifies the BC exposure of jeepney drivers, which is an essential first step for air pollution mitigation. Although jeepney drivers represent an extreme exposure case, measurements presented in this study can provide broader insights for the exposure of the general commuting public as well.

Spatiotemporal characteristics of BC were obtained using a mobile measurement instrument for two routes in Quezon City, Metro Manila: one with heavy traffic in the urban center, and the other with urban background conditions in a state university campus, which differ in busyness and zoning. Sampling was conducted in January and February 2020 over a span of two weeks for each route, from 6 AM to 7 PM. The city center route hosts a wide range of concentrations (11.0 - 199.2 μg m^-3) with a median of 50.4 μg m^-3, while those in the university route ranged from 18.7 to 72.9 μg m^-3 with a median of 31.0 μg m^-3. Overall concentrations for both routes are over three times higher than those reported in the US and Europe. Wider commercial roads with larger vehicular volumes are associated with consistently high in-vehicle concentrations all throughout the day, suggesting that the spatiotemporal distribution of BC is associated with traffic conditions and specific road types. Initial analysis showed that exposure is linked to route conditions that promote high vehicular volume, such as road width and overall street busyness, indicating that on-road sources are the primary factors for the significantly high concentrations. Further analysis using multiple linear regression will be performed to quantify the influence of identified emission hotspots within the routes on BC concentrations.