Exposure of City-Dwellers to Particulate Matters during Commuting Trips in the Metropolitan Area of Karachi
KAMRAN KHAN, Haider Khwaja, Sumayya Saied, Saiyada Masood,
University of Karachi, Pakistan Abstract Number: 466
Working Group: Urban Aerosols
AbstractThis study provides the missing knowledge on the commuter’s exposure to PM in a megacity of the world seeing unprecedented growth in population, urbanization, traffic, and air pollution. Extensive sampling campaigns of real-time size-segregated PM (PM1, PM2.5, PM7, PM10 and TSP) were carried out to assess commuter’s exposure to these pollutants by seven diverse routes in the highly urbanized city of Karachi. The findings strongly indicate that commuters in Karachi were exposed to extremely high PM concentrations than many cities in the developed world. Size-fractions of PM revealed substantial intra-route and inter-route variability, indicating that PM may be dependent on many factors such as route topography, building and road layouts, extent of emissions, mixed fleet, distance from traffic, passage through intersections, traffic conditions, traffic densities between routes, vehicle speed, trip duration, and meteorological conditions. Results suggest that the highest trip average concentrations occur on the route (Route-5) connecting the industrial corridor and the commercial area. The PM1/PM2.5 and fine/coarse (PM2.5/PM10) ratios of all routes ranged 0.13 – 0.25 and 0.08 – 0.14, respectively, suggesting that traffic emissions were the cause of high PM. Karachi’s characteristic roadside sources (e.g., restaurants, outdoor barbecuing, cigarette smoking, resuspension of the dust, and construction activities) contributed to high PM. The PM2.5 inhalation dose was high (1.1 – 3.2 µg/km). The inhalation cancer risk associated with the exposure of PM2.5 exceeded the US EPA benchmark of 10-6 - 10-4. As this study is the first to extensively analyze commuters’ exposure, further research is needed by local and federal authorities to implement effective mitigation strategies towards better air quality in Karachi, Pakistan.