Polycyclic-Aromatic Hydrocarbons (PAHs) at Roadside Environments:Analysis of Ambient Air and Dry Deposition

Polycyclic aromatic hydrocarbons (PAHs), a group of compounds which includes toxicants and carcinogens, are emitted into ambient air in vehicle exhaust. Potentially harmful levels of PAHs are found in ambient air and dry deposition near high traffic roads. However, these compounds in this microenvironment have received little attention in regards to public health. This study seeks to better understand the spatial and temporal distribution of traffic-related pollutants in the near-road environment, and to identify susceptible populations with regards to highway proximity and contaminant transport. The study will use monitoring and spatial modeling for PAHs, elemental carbon and other pollutants, and a case study in Detroit, Michigan. Airborne particles will be captured on filters, and deposition will be collected on surrogate surfaces. Samples will be analyzed by GC/MS for 16 PAH species. To estimate the “roadway gradient,” ambient air and dry deposition samples will be collected simultaneously at multiple sites along a transect from major highways, and at a “background” site largely unaffected by highway traffic. These sites will be monitored seasonally. Modeling of key environmental variables, e.g., wind speed, direction and traffic flow, will aim to characterize the distribution of these traffic-generated pollutants, including both airborne and deposition levels. Spatial analysis methods will analyze the susceptible population based on prevailing winds and deposition patterns. In addition to assessing dry deposition's potential as an exposure pathway, the results will test the reliability of using dry deposition of PAHs as a surrogate for PAHs in air monitoring.