Sealcoat
Sealcoating Your Driveway? Be Sure You Don’t Use a Product with a Coal-Tar Base.
The U.S. Geological Survey (USGS) has identified coal-tar-based sealcoat—the black, viscous liquid sprayed or painted on asphalt pavement such as parking lots and driveways—as a major source of polycyclic aromatic hydrocarbon (PAH) contamination. PAHs are a group of chemical compounds that are of concern to the environment because several of them are toxic. Aquatic life is especially affected. PAHs diminish the ability to swim in salamanders, impair the growth and development of frogs, and cause liver damage in fish. PAHs can potentially affect animal and human development: cancers linked to PAH exposure include lung, skin, bladder, and gastrointestinal cancers. How does it happen? Over time, coal-tar-based sealant begins to degrade and enters the water supply through storm-water runoff. The dust created from sealcoat, mostly as a result from friction from vehicle tires and snow plows, is rich in PAHs and is blown by the wind, tracked indoors on the soles of shoes, inhaled, and absorbed by the skin. Many materials contain PAHs. It is the amount of PAHs in coal-tar-based sealcoat that is of concern. An asphalt driveway contains 1.5 milligrams of PAHs per kilogram of fresh asphalt. If you sealcoat the driveway with a coal-tar-based product, you just coated your driveway with 70,000 milligrams of PAHs per kilogram. Quite an increase in toxic waste for something that only produces a temporary cosmetic effect. Chain retailers, like Home Depot and Ace Hardware, have banned the sale of coal-tar-based sealants and only sell alternative products using asphalt or latex as a base. However, commercial sealcoat applicators are able to make purchases of coal-tar-based sealcoat through their distributors. If you use a sealcoat applicator to work on your driveway, make sure your contactor uses an asphalt- or latex-based product.
For more information on coal-tar-based sealcoat, you can search for “USGS coal-tar” or go to the USGS and Environmental Protection Agency (EPA) websites and download USGS studies.