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No Toxic Run-Off

Study Shows Asphalt Sealcoat

Poses Environmental Threat

Asphalt previously treated with

sealcoat shows signs of wear.

According to a recent study in Texas by the U.S. Geological Survey National Water-Quality Assessment (NAWQA) Program and the City of Austin, the black emulsion sealcoat applied to asphalt pavement has extremely elevated concentrations of polycyclic aromatic hydrocarbons (PAHs) and can significantly affect the quality of downstream water resources. PAHs are known to have adverse health effects on animals, plants and people. Small particles of sealcoat flake off as they are abraded by vehicle tires, and can wash into urban streams with rain and runoff. The study found that particles in runoff from coal-tar based sealcoated parking lots have PAH concentrations that are about 65 times higher than in particles washed off parking lots that have not been sealcoated. Particles in runoff from parking lots sealed with asphalt-based sealcoat, the other major product on the market, have PAH concentrations about 10 times higher than those from unsealed lots.

Sept. 2006 Update: Two Senators Urge EPA to Study Asphalt Sealant Runoff

Sens. Jim Jeffords (I-Vt.) and John Warner (R-Va.) have asked EPA Administrator Stephen Johnson to conduct studies on how sealants commonly used on asphalt pavements increase concentrations of toxic substances (polycyclic aromatic hydrocarbons-- PAHs) in watersheds, and how such contaminants affect human health and the environment. Studies from the U.S. Geological Survey (USGS) over the past two years have shown that the chemicals can cause cancer in humans and kill aquatic life in high concentrations. The substance has long been associated with lung cancer among roofers and asphalt workers, according to the National Institute of Environmental Health Science. (Based on a report by E & E Daily.)

November 2008 Update: Follow-Up Report by Authors of Austin, TX Research

"We reported in 2005 that runoff from parking lots treated with coal-tar-based sealcoat was a major source of polycyclic aromatic hydrocarbons (PAHs) to streams in Austin, Texas. Here we present new data from nine U.S. cities that show
nationwide patterns in concentrations of PAHs associated with sealcoat."

► Click Here to View the Report (PDF)

This article is based on

reporting in the websites of

Science Daily and USGS.