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SGS science for a cIran:ghng world 16 f 0. Prepared in cooperation with the City of Austin. Texas Parking Lot Sealcoat: A Major Source of Polycyclic Aromatic Hydrocarbons (PAHs) in Urban and Suburban Environments By Peter C. Van Metre', Barbara 1 Mahler', Mateo Scoggins and Pixie A. Hamilton' Collaborative studies by the City of Austin and the U. S. Geological Survey (USGS) have identified coal -tar based sealcoat—the black, shiny emulsion painted or sprayed on asphalt pavement such as parking lots —as a major and previously unrecognized source of polycyclic aromatic hydrocar- bon (PAH) contamination. Several PAHs are suspected human carcinogens and are toxic to aquatic life. Studies in Austin, Texas, showed that particles in runoff from coal -tar based sealcoated parking lots had concentrations of PAHs that were about 65 times higher than concentrations in particles washed off parking Its that had not been sealcoated. Biological studies, conducted by the City of Austin in the field and in the laboratory, indicated that PAH levels in sediment contami- nated with abraded sealcoat were toxic to aquatic life and were degrading aquatic communities, as indicated by loss of species and decreased numbers of organisms. Identification of this source of PAHs may help to improve future strategies for controlling these compounds in urban water bodies across the Nation where parking lot sealcoat is used. U.S. Department of the Interior U.S. Geological Survey Particles in runoff from coal -tar based sealcoated parking Tots had concentrations of PAHs that are about 65 times higher than concentrations in particles washed off parking Tots that had not been sealcoated. Printed an recycled paper What are PAHs, coal tar, and seatcoat? Polycyclic aromatic hydrocarbons (or PAHs) are a group of organic contam- inants that form from the incomplete combustion of hydrocarbons, such as coal and gasoline. PAHs are an environmental concern because they are toxic to aquatic life and because several are suspected human carcinogens. Coal tar is a byproduct of the coking of coal, and can contain 50 percent or more PAHs by weight. Sealcoat is a black liquid that is sprayed or painted on asphalt pave- ment in an effort to protect and beautify the asphalt. Most sealcoat products are coal-tar or asphalt based. Many coal -tar sealcoat products contain as much as 30 percent coal tar by weight. Product analy- ses by the City of Austin indicated that coal -tar sealcoat products have median concentrations of total PAHs about 70 times higher than concentrations in asphalt -based sealcoat products. Sealcoat is used commercially and by homeowners across the Nation. It is applied to residential driveways and to parking lots associated with commercial businesses (including strip malls and shopping centers), apartment and condo- minium complexes, churches, schools, and business parks. The City of Austin, Texas, estimates that about 600,000 gal- lons of sealcoat are applied every year in the greater Austin area. National use numbers are not available, but commer- cial availability suggests that asphalt based sealcoat is commonly used on the West Coast and coal-tar based sealcoat is commonly used in the Midwest, the South, and on the East Coast. Fact Sheet 2005 -3147 January, 2006