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Environmental concerns <br />1110111111w- <br />0 <br />NBUtion <br />Control <br />Agency f you decide to sealcoat ,-our asphalt <br />driveway this year., there are a few <br />things you should know. Sealcoating <br />makes old asphalt look new and protects its <br />surface, but there are serious environmental <br />concerns with its use. <br />Se,alcoat comes in two basic varieties: coal <br />tar-based and asphalt-based. The coal tar <br />variety is more resilient, but it contains <br />much higher levels of a class of chemicals <br />called, P` .Hs (polN T cyclic aromatic <br />hydrocarbons) that harni fish', and with <br />prolonged exposure, pose a risk of cancer <br />in humans (see Figure 1). <br />Environmental problems <br />Coal tar is a waste material generated in the <br />conversion of coal to coke. Manufacturers <br />choose coal tar for sealcoat because of its <br />resistance to petroleum products like <br />gasoline and oil,, which drip from cars and <br />deteriorate asphalt surfaces. In time, <br />sunlight and vehicle traffic wears down <br />sealcoat and sealcoat flat-ces are washed <br />awav by rain or carried zmvay by wind,, <br />contaminating stormwater ponds, streams <br />and lakes with PAHs. <br />PAHs cause tumors in some fish, disrupts <br />the reproduction of aquatic organisms!, alid <br />causes some water-bottom species to avoid <br />sediment altogether. Health risks to <br />hum,-uis related to PAHs are based on the <br />length of exposure to vapors or sediments <br />contaminated with PAHs. <br />PAH Concentrations <br />Coal tar contains as much as 30 percent <br />PAHs by weight. A study in Austin, Texas, <br />compared the level of PAHs in water <br />coming off parking lots without sealcoat to <br />q <br />wq-strm4-12 * September 2009 <br />water coming off parking lots coated with <br />asphalt- and coal-tar sealcoat (Figure 2). <br />Figure 1: Relative amounts of PAHs in <br />sealcoat products <br />An Austin, Texas, study determined that <br />sealcoat products based on coal tar <br />contained up to 1,000 times more PAHs than <br />asphalt-based products. Consider asphalt- <br />based sealcoat if you choose to coat your <br />driveway. <br />Figure 2: Concentrations of PAHs in runoff <br />Asphalt-based sealcoat runoff (B) can contain <br />10 times more PAHs than an uncoated <br />driveway (A) and runoff from a coal-tar <br />sealcoated driveway (C) may have <br />concentrations of PAH 65 times higher than <br />an uncoated driveway. <br />Minnesota Pollution Control Agency 520 Lafayette Rd. N., St. Paul, MN 55155-4194 * www.pca.state.mn.us <br />651-296-6300 * 800-657-3864 TTY 651-282-5332 or 800-657-3864 * Available in alternative formats <br />