Sealcoat is a black liquid that is sprayed or painted on asphalt pavement in an effort to protect and beautify the asphalt. Many of the coal-tar based sealcoat products that are commercially sold contain as much as 30 percent coal-tar by weight. In a study conducted by the City of Austin Texas and the U.S. Geological Survey, it was discovered that the amount of polycyclic aromatic hydrocarbons (PAHs) washing off parking lots where sealcoat had been applied was 65 times higher than concentrations in parking lots that had not been treated with sealcoat. Several PAHs are suspected human carcinogens and are toxic to aquatic life.
As an alternative to coal-tar based sealcoating of parking lots and driveways, homeowners and businesses are encouraged to use asphalt-based sealcoat products that are also commercially available. Asphalt-based sealcoat contains lower levels of PAHs. In addition, individuals are encouraged to eliminate the need for the use of sealcoating by installing concrete and unsealed asphalt pavement.