Health risk from toxic pavement

When you think of pollution, you might picture an industrial center like Camden, N.J., or Jersey City. But new research shows that when it comes to a potent class of cancer-causing toxic chemicals, many American parking lots are a lot worse. New studies paint an increasingly alarming picture – particularly for young children – about how these chemicals are being spread across big swaths of American cities and suburbs by what may seem an unlikely source – a type of asphalt sealer. These sealants are derived from an industrial waste, coal tar. Advertise | AdChoices Four new studies (links are at the end of this article) announced this week further implicate coal tar-based asphalt sealants as likely health risks.  The creosote-like material typically is sprayed onto parking lots and driveways in an effort to preserve the asphalt. It also gives the pavement a dark black coloring that many people find attractive. Coal tar is a byproduct of the steelmaking industry. In 1992, the U.S. Environmental Protection Agency declared that it would not be classified as a hazardous waste, even though it met the characteristics of one, because it could be recycled for uses that include coating asphalt. That meant steel mills didn’t have to pay for costly landfilling or incineration of the waste. Only in recent years have scientists discovered the ill effects of this practice. Coal tar sealants are used most heavily in the eastern United States, but were applied in all 50 states until Washington state banned the products last year. More than a dozen local governments, including Washington, D.C., and Austin, Texas, also have banned the coal tar sealants in favor of the other major type of sealant, which is asphalt-based. Asphalt-based sealants contain about 1/1000th the concentration of the cancer-causing chemicals that coal tar-based products do. Home Depot and Lowe’s stores have dropped the coal tar sealants from their product lines, but still some 85 million gallons of the coal tar-based sealants are applied annually in the United States. The new research, published in peer-reviewed science journals, focuses on a class of chemicals found in coal tar and known as “polycyclic aromatic hydrocarbons,” or PAHs. Previously, researchers believed that people’s exposure to PAHs came primarily through food, which contains trace amounts produced primarily from smoking food or cooking it at high temperatures in practices such as grilling, roasting, and frying. PAHS are produced when any organic matter burns. The new research shows: It appears that children – especially those from 3 to 5 years old – living by coal tar-sealed parking lots and driveways are getting a bigger dose of PAHs from house dust than from their food. The kids who put their hands in their mouth most often are likely receiving 9 ½ times more exposure through house dust than through food, according to research led by E. Spencer Williams, a Baylor University human health risk assessment expert. That’s just from the house dust. When the kids are outside in the yard or playing on coal tar-sealed pavement, they likely are picking up much larger doses. While researchers previously theorized that airborne PAHs come mostly from power plants, factories and cars’ and trucks’ tailpipe emissions, U.S. Geological Survey researchers measured large amounts vaporizing into the air off coal tar-sealed parking lots.  The concentrations coming off parking lots in suburban Austin, where the researchers are based, were higher than in centers of heavy industry, including Jersey City and Camden, N.J.; Chicago; London and Manchester, England; and Guangzhou, China. The Austin parking lots tested were three to eight years old. Much more off-gassing occurs in the first few years after the sealants are applied, researchers said. Concentrations measured four feet above the coal tar-sealed lots in some cases exceeded health-protection guidelines recommended by a European Union science panel to protect against cancer. The United States has no similar guidelines. Extrapolating from the 85 million gallons of coal tar sealants laid down annually and the out-gassing rates measured in Austin, Geological Survey researchers calculated that nationwide, more PAHs are getting into the air from coal tar-sealed parking lots, driveways and playgrounds than from all the auto and truck exhaust.