Modeling of in-vehicle human exposure to ambient fine particulate matter
A method for estimating in-vehicle PM(2.5) exposure as part of a scenario-based population simulation model is developed and assessed. In existing models, such as the Stochastic Exposure and Dose Simulation model for Particulate Matter (SHEDS-PM), in-vehicle exposure is estimated using linear regression based on area-wide ambient PM(2.5) concentration. An alternative modeling approach is explored based on estimation of near-road PM(2.5) concentration and an in-vehicle mass balance model. Near-road PM(2.5) concentration is estimated using a dispersion model and fixed site monitor (FSMs) data. In-vehicle concentration is estimated based on air exchange rate and filter efficiency. In-vehicle concentration varies with road type, traffic flow, windspeed, stability class, and ventilation. Average in-vehicle exposure is estimated to contribute 10-20 percent of average daily exposure. The contribution of in-vehicle exposure to total daily exposure can be higher for some individuals. Recommendations are made for updating exposure models and implementation of the alternative approach. (C) 2011 Elsevier Ltd. All rights reserved.