by Stephen Kale
Have you ever driven into the parking lot of your favorite shopping center or walked on a school playground and noticed that the shiny black surface has been freshly painted and sealed? If so, you may have smelled a strong gasoline or mothball odor. The source of that smell is a chemical substance called coal tar, a primary ingredient in parking lot, playground and blacktop driveway sealants. Coal tar is actually the residue that remains after coal is made into coke, a product used in steel production.
Probable Human Carcinogens
Scientists have known for many years that coal tar is a complex substance made up of many different chemicals. One class of these chemicals is known as polycyclic aromatic hydrocarbons or PAHs. Scientists have learned that certain coal tar PAHs are toxic to small invertebrate animals found in creeks and in the Edwards Aquifer. In addition, the U.S. Environmental Protection Agency (EPA) classifies some of these PAHs as probable human carcinogens. Seven of these probable human carcinogens are contained in the coal tar sealants used on parking lots, playgrounds and driveways.
In 1993 the City of Austin began a pollution survey of Austin’s creeks including Barton Springs Pool. These surveys eventually led to the discovery of harmful levels of PAHs in sediments in the creeks but not in the pool. Austin and the U.S. Geological Survey (USGS) joined forces to determine the source of these PAHs. They found that the PAHs were migrating from coal tar-sealed parking lots and polluting nearby creeks and residences. From these studies, Baylor University evaluated the health risks posed by PAHs in residences near coal tar-sealed lots and concluded that the PAHs pose excessive cancer risks to small children. In 2005 Austin passed an ordinance prohibiting the application of coal tar pavement sealants.
USGS scientists and others have found the same pattern of coal tar PAHs migrating from parking and playgrounds in other communities across the country. As a result, the states of Washington and Minnesota and other local communities have enacted bans against their use. Several Midwestern states, with financial assistance from the EPA, have formed a region-wide PAH reduction project, and a number of retailers no longer sell coal tar sealants and offer sealants with alternative materials.
Closer to Home
In 2012 the Edwards Aquifer Authority banned the application of coal tar sealants in the recharge zones in Hayes and Comal County. The USGS and others have found these harmful PAHs in some San Antonio creeks. The City of San Antonio does not allow the application of coal tar sealants on city-owned properties, but this prohibition does not apply to privately owned property. Recognizing this, in late 2012 the City of San Antonio Citizens Environmental Advisory Committee (CEAC) launched an initiative to persuade city leaders to enact a city-wide ban. While the committee has devoted time and energy to educating city leaders about the dangers of these coal tar sealants, the city continues to allow the use of these sealants throughout our community.
What can you do? First, become educated and aware of the pavement sealants you and your family are exposed to. Like me, the more you learn, the more concerned you will become about the use of these harmful sealants. Second, voice your support to city leaders for an end to the use of coal tar sealants in San Antonio.
Stephen Kale is a Navy veteran and registered professional engineer. He is a member of the San Antonio Citizens Environmental Advisory Committee and currently serves as a consultant to the U.S. Department of Energy’s Smart Grid Investment Grant program. He spent more than five decades in nuclear and energy engineering with the E.I. DuPont de Nemours, Inc., Westinghouse Corporation and the U.S. Department of Energy.