The Environmental Protection Agency has completed their runoff report as was promised to Congressman Lloyd Doggett 2 years ago.  The official title is Assessment of Water Quality of Runoff from Sealed Asphalt Surfaces, but perhaps a more appropriate title would be: "An Assessment of PAH Pollution Potential from Pavement Sealants During the Curing Process."  That's because the study used only one coat of sealant (usually 2 are recommended), didn't allow car traffic on the lot, and collected only one runoff sample between 30 and 160 days after application.

Important findings were:
  • Runoff from a coal tar sealed surface is about 100 times more potent in PAHs than asphalt based sealant.
  • Choosing to ban coal tar sealants may be the most cost-effective way for communities to deal with the pollution impacts of this product. 
Lessons learned, I hope, are:
  • Pavement sealants don't always cover as much as the label states; buy a little extra!
  • Don't use a toxicity test that is negatively affected by the kind of water used.  And if the first one doesn't work, try another one.  For example, try the Ames Test.
  • Don't do your experiment downwind of what appears to be a crumbling coal tar sealed roof.
  • If traffic is the major cause of wear and sealant loss during the sealant's life, recognize the limitations of the research.

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