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09/27/2016 - Just imagine a hidden health risk lurking in your driveway or a nearby parking lot that could be harming you, your children, and the nearby environment. A growing number of scientists, community leaders and environmentalists think there is, and many are taking action to do something about it. The problem, they say, rests in the coal tar-based sealcoat that is often applied to asphalt driveways and parking lots to protect the pavement from oils, tire wear and other factors that lessen the life of the surface.

Coal tar sealcoat typically contains 20 to 35 percent coal tar pitch, which is considered by the National Toxicology Program to be a known human carcinogen. Coal tar, a byproduct of the steel manufacturing industry, is made up of about 50 percent polycyclic aromatic hydrocarbons (PAHs) by weight. Many of those PAHs, which includes hundreds of chemical compounds, are believed to cause cancer and promote cancer by altering human DNA. Exposure to PAHs have also been linked to cardiovascular disease and poor fetal development.

Studies by the United States Geological Service (USGS), some academic institutions, and some state and local agencies have identified coal tar sealcoat as a major source of PAH contamination in urban and suburban areas, with a potential concern for human health and aquatic life.

While coal tar-based sealcoat does a good job of protecting pavement, researchers say that it wears into small particles as it ages. Those particles contain high levels of PAHs, which can be tracked into homes and incorporated into house dust. For people who live next to seal-coated pavements, ingestion of PAH-contaminated house dust and soil can result in an elevated risk of cancer, particularly for young children. Exposure to PAHs, especially early in childhood, has been linked by health professionals to an increased risk of lung, skin, bladder and respiratory cancers.

The USGS also says that runoff from coal tar sealcoated pavement is toxic to certain aquatic life, particularly fathead minnows and water fleas, which are commonly used to assess toxicity. Exposure to even diluted runoff from coal tar sealcoated pavement can cause DNA damage and impair DNA repair for aquatic life.

Last month, representatives from the Michigan Department of Environmental Quality (DEQ) met with researchers from the USGS to discuss research on coal tar sealants and PAHs as they relate to stormwater pollution. The Michigan Department of Transportation has agreed to phase out the use of coal tar-based sealcoat.

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