Parking Lot Sealcoat Contaminates New York/New Jersey Harbor Watershed

Coal-tar sealants, widely used on parking lots and driveways to make asphalt last longer, are a major source of polycyclic aromatic hydrocarbon (PAH) contamination in the New York/New Jersey Harbor Watershed, according to a 2007 study published by the New York Academy of Sciences in September.

PAHs make up a collection of more than 100 different chemicals that are known to cause lesions and tumors in fish, destroy aquatic communities and a serious concern because they are a suspected human carcinogen.

Of the numerous sources evaluated by the NYAS, coal-tar based sealant was one of the 11 major sources of PAHs released in the Watershed. The NYAS defines a major source as one contributing individually more than two percent to the total emissions released to air, water and land within the Watershed. The study estimates 12 percent of the PAH loadings come from the sealants.

Coal-tar sealants were also found to be a major source of PAH contamination in local waterways in Austin, Texas. The U.S. Geological Survey in 2003 sampled runoff from parking lots in Austin, which found runoff from coal tar sealed parking lots to have concentrations of PAHs 65 times higher than parking lots without the sealcoat.

The environmental problem is great since coal tar based sealants are mainly used east of the Rocky mountains and field and lab studies by the City of Austin show coal-tar sealant is toxic to aquatic organisms at levels seen in streams in the Austin area, according to Mateo Scoggins an aquatic biologist for the City.

"We found subtle shifts in aquatic communities at the Probable Effect Concentration (PEC) and at high concentrations we found radical changes," he said. The studies also saw toxicity at slightly below the PEC levels for PAHs. The PEC, a widely used sediment-quality guideline, is 22.8 mg/kg for PAHs. The average concentration of PAHs from parking lots sealed with coal-tar in Austin was 3,500 mg/kg.

Industry representatives challenged the USGS study, according to Peter C. Van Metre, one of the authors. He said a group of ten parties within the industry sent a letter to USGS questioning the findings and demanding the agency make changes to the report.

"We responded to the challenge of complaint," Van Metre said. "We made some revisions, but the results are still the same and the conclusion is still the same."

The studies prompted the City of Austin and Dane County, Wisconsin to ban the use of coal-tar based sealants; big box stores like Home Depot and Lowe's no longer carry them, according to public affairs representatives for both retailers.

While the NYAS did not recommend banning coal-tar sealants, the study advised people to avoid using sealants containing PAHs and to consider alternative designs and paving materials for certain surfaces.

PAHs are also a high priority pollutant in the Chesapeake Bay. U.S. Fish and Wildlife, though not looking at the source of PAHs, have found a strong link between the high tumor rates in catfish in the Anacostia River and the high concentration of PAHs there, according to Fred Pinkney, a biologist with the agency.

Greg Allen with the Environmental Protection Agency at the Chesapeake Bay Program, a consortium of agencies directed toward restoring the Bay, says they are trying to determine where the PAHs are coming from.

"If we can attribute a significant portion of the load to coal-tar based sealants, it would make sense for us to talk about how we may be able to either voluntarily get people not to use them or possibly something a little more formal along the lines of a ban in the region for the products," he said.

The Chesapeake Bay Program isn't formally studying PAH contamination in the Bay from coal- tar sealants. The only step it has taken, according to Allen, is talk to people in the industry to find out how much is applied in the area.

In general, concentrations of PAHs, not just from coal-tar sealants, have been increasing in lakes and reservoirs in urban and suburban areas since 1970, according to the USGS.

While most of the sources of PAHs are difficult to control, using coal tar sealants is controllable. Alternatives like concrete or asphalt-based sealcoat exist. There are also companies making PAH-free sealant, according to Scoggins, the aquatic biologist with the City of Austin.

Companies making PAH-free sealant:

Neyra

Carbonyte Inc.

Blacklidge Emulsions