MOUNTLAKE TERRACE, Wash. – A substance designed to protect asphalt parking lots is putting people and the environment at risk, government scientists are telling state lawmakers.
Polycyclic aromatic hydrocarbons (PAHs) are used a lot in coal tar-based sealants used in many parking lots.
"The coal tar products have about ten percent PAHs by weight and this is something we measure in the environment in parts-per-million, so 10 percent is a big number," said Peter Van Metre with the U.S. Geological Survey.
That far outweighs the most wanted list for PAH sources, including car exhaust, charcoal and the long time PAH boogeyman, used motor oil.
"Used motor oil has about one-200th of the concentration of PAHs as the coal tar seal coat products do," said Van Metre.
Van Metre and his team found elevated levels of PAHs in lakes all over the country including Lake Ballinger in Mountlake Terrace. They traced most of the sources to nearby parking lots treated with coal tar-based sealants.
The results of the study are being shared with a Washington state legislative panel considering a bill to ban those sealants. Other city and state governments are also considering it.
Most companies and suppliers in this area say they have already stopped using it and have found alternative, asphalt based products that are comparable in performance and price with a fraction of the toxins.