Coal Tar Sealant Largest Source of PAHs in Lakes

Coal-tar-based pavement sealant is the largest source of polycyclic aromatic hydrocarbons (PAHs) found in 40 urban lakes studied by the U.S. Geological Survey.

USGS scientists collected sediment cores from 40 lakes, analyzed the cores for PAHs, and determined the contribution of PAHs from many different sources using a chemical mass-balance model. On average, coal-tar-based sealcoat accounted for one-half of all PAHs in the lakes, while vehicle-related sources accounted for about one-quarter. Lakes with a large contribution of PAHs from sealcoat tended to have high PAH concentrations, in many cases at levels that can be harmful to aquatic life. Analysis of historical trends in PAH sources to a subset of the lakes indicates that sealcoat use since the 1960s is the primary cause of increases in PAH concentrations.

PAHs are an environmental health concern because several are probable human carcinogens, they are toxic to fish and other aquatic life...