Automotive Sources of Carcinogenic Polycyclic Aromatic Hydrocarbons Associated with Particulate Matter in the Chesapeake Bay Region

We analyzed >400 particulate samples collected from throughout the Chesapeake Bay region between 1991 and 1998 for polycyclic aromatic hydrocarbons (PAHs). Isomer ratios of PAHs associated with aerosol and surface water particles demonstrate that motor vehicles are a major source of carcinogenic combustion-derived PAHs to Chesapeake Bay. Most of the benz[a]anthracene, benzo[a]pyrene, benzo[b]fluoranthene and their isomers in air, rain, and surface waters of Chesapeake Bay appear to be derived from automotive sources. Lesser, but still significant amounts (53(±5)%) of these PAHs in the sea surface microlayer near urban areas are motor vehicle-derived, with 47(±5)% being coal-derived. In contrast, PAHs in surface sediments of Chesapeake Bay are predominantly coal-derived (86(±8)%) and at most 14(±8)% motor vehicle-derived. Thus, carcinogenic PAHs input to the bay from motor vehicles are either degraded prior to deposition to the sediments or are diluted by previously deposited coal-derived PAHs in the seabed. Like anthropogenic nitrogen (NOx), which leads to coastal eutrophication, managing the impact of carcinogenic PAHs on coastal regions will need to focus on motor vehicle use, which continues to outpace population growth in areas such as Chesapeake Bay.