Parking Lot Sealant Identified as Major Contaminant

Parking Lot Sealant Identified as Major Contaminant

Released: 6/22/2005
U.S. Department of the Interior, U.S. Geological Survey
Office of Communication

The shiny black coating applied to parking lots and driveways has extremely high concentrations of a chemical compound that can affect the quality of water in urban areas, according to a recent joint USGS and City of Austin study. In the study, coal-tar based sealants are shown to have extremely elevated concentrations of polycyclic aromatic hydrocarbons (PAHs). PAHs are an environmental concern because they are toxic to aquatic life and some types are suspected human carcinogens.

PAHs are a group of organic contaminants that form from incomplete combustion of hydrocarbons such as coal. They are common in coal tar, a byproduct of the coking of coal.

The application of the coal-tar sealant on driveways and parking lots poses an environmental threat because small particles of the sealcoat begin to crumble from vehicular traffic and rain can cause them to wash into urban streams, lakes, and reservoirs.

According to Dr. Robert Hirsch, USGS Associate Director for Water, "Our study found that concentrations of PAHs were much higher in runoff from parking lots sealed with coal-tar based sealcoat than from all other types of parking lot surfaces. Until now, this has been an unrecognized source of PAHs in urban and suburban water resources."

In the past, likely sources of PAHs in urban watersheds were thought to be from leaking motor oil, tire wear, vehicle exhaust and atmospheric deposition."

The USGS study found that particles in runoff from coal-tar based sealcoated parking lots have PAH concentrations that are about 65 times higher than concentrations 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, are about 10 times higher in PAHs than those from unsealed lots, and about one-sixth the concentration from coal-tar based sealcoats.

http://www.usgs.gov/newsroom/article.asp?ID=718

LOL :crazy:

...lots and driveways in the country! And that is not just in the top sealants, but all the way through.

I'll show this to my wife, who's been bugging me for years to do it.;) :bounce: