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Texas Water Science Center

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Coal-tar-based sealcoat being applied to a test plot.

PAH and Sealcoat Contacts

  • Barbara Mahler
    USGS Research Hydrologist
    (512) 927-3566
  • Peter Van Metre
    USGS Research Hydrologist
    (512) 927-3506
  • Mailing Address:
    U.S. Geological Survey
    1505 Ferguson Lane
    Austin, TX 78754

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PAHs and Coal-Tar-Based Pavement Sealcoat

Recent Publications

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Coal-tar-based pavement sealant is a potent source of polycyclic aromatic hydrocarbons (PAHs), as documented by the USGS and other researchers.

Coal-tar-based sealcoat products typically are 20 to 35% coal tar or coal-tar pitch—these materials are known human carcinogens that contain high concentrations of PAHs and related chemicals. Coal-tar-based pavement sealcoat typically contains 35,000 to 200,000 mg/kg (parts per million, or ppm) PAHs, about 100 times more PAHs than in used motor oil and about 1,000 times more PAHs than in sealcoat products with an asphalt base.

Coal-tar sealcoat is abraded to a fine dust by car tires and snow plows, requiring reapplication every 2–5 years. The mobile high-PAH dust is blown, washed, or tracked into nearby soil, stormwater ponds, streams, lakes, and house dust. Many of the lighter-weight chemicals in coal-tar sealcoat volatilize (evaporate) into the air, primarily during the 2 weeks following application, but continuing for years after application.

Learn more about PAHs and coal-tar-based sealcoat from

Key Findings

Some USGS publications on PAHs and coal-tar-based pavement sealant have been subject to Information Quality Act correction requests. USGS Information Quality Guidelines, the correction requests, and USGS responses can be found at: http://www.usgs.gov/info_qual/

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Page Last Modified: Tuesday, 14-Apr-2015 13:07:59 EDT

PAH Concentrations in Lake Sediment Decline Following Ban on Coal-Tar-Based Pavement Sealants in Austin, TX Press release Paint it Black