Washington state has banned coal-tar-based asphalt sealants—the first state in the nation to do so. Environmental reporter Robert McClure has an in-depth article on the state’s decision here. Previous research has shown that runoff from surfaces coated with these types of sealants can harm aquatic environments; more recent studies—which heavily influenced the Washington decision—link them to human health hazards as well.
In 2006, Stormwater magazine ran an article by David Richardson about a similar ban that the city of Austin, Texas, had recently enacted; it was the first city in the US to put such a ban in place, and other local governments have followed. Water-quality testing beginning in the 1990s had shown higher than expected levels of polycyclic aromatic hydrocarbons (PAHs) in Austin-area creeks. Painstaking detective work eventually led local officials to determine a major source: parking lots that had been sealed with coal-tar-based sealants. Researchers measured creek sediments to determine which areas had the highest concentrations of PAHs, and ultimately tested the runoff from parking lots that had been coated with different types of sealant as well as from uncoated concrete lots. (Another type of sealant, which is asphalt based, does not release PAHs.)
Sealants are applied as often as every two years to protect parking lot pavements and improve their appearance. Before the city’s 2006 ban, about 600,000 gallons of sealant were used in the city each year. Tom Ennis of Austin’s Watershed Protection Department, who is also quoted in McClure’s article, noted that the less-toxic asphalt-based sealants would still be allowed in Austin, but he speculated that other techniques might become more widely used: concrete pavement, which would reduce the urban heat island effect; “white topping” the asphalt with a couple-inch-thick layer of concrete; or pavers.
Does your city have a similar ban, or is it considering one? Do you think Washington state’s decision will spur other states to follow?