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Parking Lot Sealants and Toxic Pollution in Urban Streams and Aquatic Life Impacts

Congressional Briefing
Friday, December 2, 2005
9:30 to 11:30 a.m.
2318 Rayburn House Office Building

Recent studies by the USGS National Water-Quality Assessment (NAWQA) have identified sealcoating, the black, shiny surface often applied to asphalt pavement, as a significant and previously unrecognized source of extremely elevated concentrations of polycyclic aromatic hydrocarbons (PAHs) in streams.  Runoff from parking lots sealed with one type of sealcoat, coal tar-based sealant, had PAH concentrations 65 times higher than concentrations in runoff from unsealed parking lots.

PAHs are suspected human carcinogens and are toxic to aquatic life.  Biological studies conducted by the City of Austin, Texas found a loss of species and decreased numbers of organisms at the PAH concentrations seen in Austin streams and observed these effects at sites downstream from the points where sealed parking lot runoff enters the streams. 

Because sealants are used nationwide and the concentrations of PAHs in lakes and reservoirs across the country are increasing, this information raises important local and national policy questions about the use of sealants and methods to prevent contaminated runoff from reaching urban water bodies.  The City of Austin Council is considering a ban on the use of coal-tar sealants and is currently requesting that citizens and businesses not use them.


  • Peter VanMetre, USGS Scientist:  USGS findings on PAH concentrations in sealcoat runoff and trends of PAH contamination in urban areas nationwide.

  • Mateo Scoggins, Biologist, City of Austin Watershed Protection and Development Review Department: Austin’s findings on how sealant impacts on aquatic life.

  • City of Austin representatives will be available to answer questions and provide a context for discussion of policy issues.

Sponsored by the Water Environment Federation in cooperation with The U.S. Geological Survey.

This briefing is free and open to the public.

For more information, please contact Pat Sinicropi at 703-684-2416 (