The report, published in the journal Environmental Science and Technology, said dust collected in the central and eastern United States contained concentrations of polycyclic aromatic hydrocarbons about 1,000 times greater than levels found in western U.S. cities where coal-tar sealcoat is less commonly used.

PAHs are an environmental concern because they are toxic to aquatic life, and several are suspected carcinogens, the USGS said Thursday in a release.

"In 2005, the USGS and the City of Austin, Texas, reported that particles in runoff from parking lots treated with coal-tar sealcoat in Austin contained extremely high concentrations of PAHs," lead researcher Peter Van Metre said in a release.

Concentrations of PAHs in dust from coal-tar treated parking lots sampled in Minneapolis; Chicago; Detroit; New Haven, Conn.; Washington; and Austin, Texas, were about 1,000 times higher than levels from sealed and unsealed parking lots in Seattle, Portland, Wash., and Salt Lake City, the report said.