In-vehicle Ultrafine Particles Exposure Measurements in a South Asian Mega City: Dhaka, Bangladesh

Shaikh Ashik-Un-Noor, Mustafizur Rahaman, Albert Presto, PROVAT SAHA, Bangladesh University of Engineering & Technology

     Abstract Number: 273
     Working Group: Urban Aerosols

Abstract
We measured and compared in-vehicle ultrafine particle concentrations in common transportation modes in Dhaka city of Bangladesh. In-vehicle measurements of particle number concentration (PNC; a measure of ultrafine particles) were collected in public buses, private cars, and rickshaws. In-car measurements were collected under (i) window-open, (ii) window-closed and air-recirculation 'off', and (iii) window-closed and air-recirculation 'on' conditions. For each case, about ten days of repeated measurements were collected on a selected 15-km route covering different times of the day (morning, mid-day, and afternoon). Results indicate that in-vehicle PNCs vary by transportation mode, higher in the public bus and substantially lower for the private cars under window-closed and air-recirculation 'on' conditions. The inter-modal variation is about a factor of two. In all modes, in-vehicle PNCs are substantially higher than the urban background level; about 4-8 times higher in public buses and 2-4 times higher in private cars with window-closed and air-recirculation 'on'. Substantially higher in-vehicle PNCs and their inter-modal variations have implications on PNC personal exposures. About 1-2 hours of commuting time (4-8% of daily hours) contribute to 15-35% of daily exposure. Exposures are higher for public bus commuters and lower for private car commuters, specifically, those who commute under window-closed and air-recirculation 'on' conditions. This study's results could help design appropriate mitigation measures for reducing personal exposure to ultrafine particles.