Studies in Austin, Texas, showed that particles in runoff from coal-tar based sealcoated parking lots have concentrations of PAHs that are about 65 times higher than concentrations in particles washed off parking lots that have not been sealcoated. Biological studies, conducted by the City of Austin in the field and in the laboratory, indicate that PAH levels in sediment contaminated with abraded sealcoat are toxic to aquatic life and are degrading aquatic communities.
Laboratory studies included toxicity tests conducted with waters collected downstream of areas which received seal-coating, and representative control areas. These studies led the researchers to estimate that about 13% of Greater Austin area streams had PAH concentrations high enough to be toxic to benthic invertebrates.
This research has led the City of Austin to ban the use of coal-tar sealants for roads, parking lots, driveways, and other paved areas.
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