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The Effects of Coal Tar Based Pavement Sealer on Amphibian Development and Metamorphosis


Coal tar based pavement sealers are applied regularly to parking lots and contain significant levels of polycyclic aromatic hydrocarbons (PAHs). Recently a connection between elevated levels of PAHs in streams and storm water runoff from parking lots has been identified. We tested the hypothesis that coal tar based pavement sealers could alter the survival, growth, and development of amphibians using a model species, Xenopus laevis. Ten fertilized individuals were placed singly into containers containing one of four treatment groups: control, low, medium, and high (respective nominal concentrations 0, 3, 30, and 300 ppm TPAH). All of the individuals in the high exposure group died by the sixth day of exposure. By day 14 there were significant patterns of stunted growth (p<0.0001) and slower development (p=0.006) in the medium and high exposure groups relative to the control and low treatment groups. When the experiment ended on day 52 the control and low-dose individuals had achieved more advanced developmental stages than the medium group (p=0.0007). These data indicate that these commonly used coal tar based pavement sealers may potentially affect the amphibian taxa living in areas that receive storm water runoff.

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The City of Austin Watershed Protection Department provided the coal tar pavement sealant flakes, the photograph of the sealant flakes, and the corresponding chemical data that made this project possible. Special thanks to Nancy McClintock and Mateo Scoggins of the City of Austin for keeping this project going. We would also like to thank Christina Byerly for assistance in the lab.

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Correspondence to Pamela J. Bryer.

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Bryer, P.J., Elliott, J.N. & Willingham, E.J. The Effects of Coal Tar Based Pavement Sealer on Amphibian Development and Metamorphosis. Ecotoxicology 15, 241–247 (2006).

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  • PAHs
  • Xenopus
  • runoff
  • non-point source pollution