AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
In-Cabin Ultrafine Particle Concentration Inside Passenger Car Fleet on Several Los Angeles Roadways
NEELAKSHI HUDDA, Constantinos Sioutas, Ralph Delfino, Scott Fruin, University of Southern California
Abstract Number: 244 Working Group: Aerosol Exposure
Abstract For large sections of the population, the highest pollutant concentration is encountered during travel where close proximity to relatively undiluted fuel combustion emissions occurs. In order to accurately assess exposure to travel related pollutants like ultrafine particles, this micro-environment needs to be correctly accounted. However, since particulate pollutant species are lost to surfaces or filtered by vehicle’s ventilation system, in-cabin concentrations can vary from nearly zero to nearly equal to roadway concentrations. The objectives of this study were to characterize in-cabin-to-roadway (I/O) ratios for ultrafine particles (UFP) through extensive measurements and modeling, and to generate realistic fleet-wide in-vehicle concentration distributions. Results for the US passenger car fleet incorporated vehicle age, manufacturer, and cabin volume distributions were used to generate fleet wide I/O distributions, which were then linked to particle concentrations observed on seven Los Angeles freeways and over 50 mile of arterial roadways. Each roadway route was sampled for a full spread of traffic and meteorological conditions to capture the full range of expected real world concentrations. In-cabin exposures varied by over a magnitude, due to inter vehicle variability and ventilation choice (in-cabin air recirculation or continuous fresh outside air intake), and inter-vehicle variation in I/O ratios was often more important than differences in on-road concentrations at different locations or on different roadway types. In general, exposure concentrations increased two to four fold when ventilation mode is switched from recirculation to outside air intake, despite air filtration during outside air intake.