Washington, D.C., has banned the use and sale of coal-tar pavement products to curb the flow of a toxic chemical contaminant called polycyclic aromatic hydrocarbons (PAHs) to the Anacostia River, Potomac River and Chesapeake Bay.
Coal-tar pavement sealers, which are commonly used to seal asphalt driveways and parking lots, are a major source of PAHs. The dust from parking lots sealed with coal tar has more than three times the concentration of PAHs as undiluted used motor oil, which is considered a leading source of PAHs. Other sources include auto exhaust, tire particles and broken-up asphalt.
A recent scientific study by the U.S. Geological Survey showed that PAH concentrations in dust from parking lots sealed with coal-tar products are about 80 times higher than in dust from unsealed parking lots. In D.C., rain washes these toxic PAHs from coal-tar sealant off paved surfaces and into the streams and creeks that flow to the Anacostia River, the Potomac River and the Chesapeake Bay. Research suggests that total PAH loads washed off parking lots could be reduced by as much as 90 percent if parking lots were left unsealed.
PAHs have been shown to cause cancerous tumors in animals, even in single doses. Non-cancerous health effects can include immune system suppression and red blood cell damage. In fish and invertebrates, adverse health effects have included cataracts, fin erosion, liver and reproductive abnormalities, and even death.
In the Anacostia River, scientists have discovered high rates of PAH-related lesions and tumors on bottom-dwelling fish. In one Fish and Wildlife Service study, 50 to 60 percent of collected fish had liver tumors. Tests suggested that PAH exposure was likely responsible for the tumors.
“It’s rare that we have a chance to knock out this kind of pollution in one fell swoop,” said George S. Hawkins, director of the D.C. Department of the Environment. “Now that we’ve discovered what’s in coal tar and what it does, we have a rare opportunity to protect our waterways relatively easily.”
The coal-tar pavement product ban took effect on July 1. Learn more about the ban at the District of Columbia’s website.