Skip to main content
U.S. flag

An official website of the United States government

Coal-tar-based pavement sealcoat—Potential concerns for human health and aquatic life

April 20, 2016


Sealcoat is the black, viscous liquid sprayed or painted on many asphalt parking lots, driveways, and playgrounds to protect and enhance the appearance of the underlying asphalt. Studies by the U.S. Geological Survey (USGS), academic institutions, and State and local agencies have identified coal-tar-based pavement sealcoat as a major source of polycyclic aromatic hydrocarbon (PAH) contamination in urban and suburban areas and a potential concern for human health and aquatic life.

Key Findings:

Human Health Concerns—As coal-tar-based sealcoat ages, it wears into small particles with high levels of PAHs that can be tracked into homes and incorporated into house dust. For people who live adjacent to coal-tar-sealcoated pavement, ingestion of PAH-contaminated house dust and soil results in an elevated potential cancer risk, particularly for young children. Exposure to PAHs, especially early in childhood, has been linked by health professionals to an increased risk of lung, skin, bladder, and respiratory cancers.

Aquatic Life Concerns—Runoff from coal-tar-sealcoated pavement, even runoff collected more than 3 months after sealcoat application, is acutely toxic to fathead minnows and water fleas, two species commonly used to assess toxicity to aquatic life. Exposure to even highly diluted runoff from coal-tar-sealcoated pavement can cause DNA damage and impair DNA repair. These findings demonstrate that coal-tar-sealcoat runoff can remain a risk to aquatic life for months after application.

Publication Year 2016
Title Coal-tar-based pavement sealcoat—Potential concerns for human health and aquatic life
DOI 10.3133/fs20163017
Authors Barbara Mahler, Michael D. Woodside, Peter C. Van Metre
Publication Type Report
Publication Subtype USGS Numbered Series
Series Title Fact Sheet
Series Number 2016-3017
Index ID fs20163017
Record Source USGS Publications Warehouse
USGS Organization National Water Quality Assessment Program