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401) <br />*10 <br />Minnesota <br />Pollution <br />Control <br />Agency <br />Coal Tar -based Sealcoat <br />Environmental concerns <br />I f you decide to sealcoat your 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 />Sealcoat 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 PAHs (polycyclic aromatic <br />hydrocarbons) that harm 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 flakes are washed <br />away by rain or carried away 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, and <br />causes some water -bottom species to avoid <br />sediment altogether. Health risks to <br />humans 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 offparking lots without sealcoat to <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 />I t t RE <br />8 <br />&Mrs m <br />viesnn <br />.,d tikes <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 altemative formats <br />