Milwaukee wants to give coal-tar sealants the boot

Milwaukee officials hope a proposed citywide ban on the use of coal-tar sealants will go a long way toward preventing a known carcinogen from contaminating area rivers and streams.

The sealants up for consideration can be sprayed or painted onto asphalt parking lots, driveways and playgrounds to protect the underlying asphalt and improve its appearance. But those benefits come with one big drawback: The sealants’ primary ingredient is coal tar, which contains extremely high levels of polycyclic aromatic hydrocarbons, also known as PAHs.

PAHs, which are found in far lower levels in asphalt-based pavement sealants, are toxic to fish and other aquatic life. Even worse, they are believed to be a cause of cancer in people.

In late December, scientists with the U.S. Geological Survey published a study concluding that most of the PAHs now found in Milwaukee streambed sediments come from runoff from pavements patched with coal-tar sealant.

As part of the study, scientists collected sediment samples from 40 streambeds, as well as dust samples from six parking lots in the Milwaukee area. They found that dust from coal-tar sealant was the source of between 42 and 94 percent of the PAHs that were found in the samples. A full 78 percent of the sediment samples had PAH levels that could harm aquatic life.

Some of the most toxic samples came from Lincoln Creek, Underwood Creek and the West Milwaukee Ditch.

The study prompted several Milwaukee aldermen to propose ordinance modifications that would effectively ban the use of coal-tar-based sealants throughout the city. With the city’s Public Works Committee having given its approval to the ban Wednesday, the proposal is now making its way to the Milwaukee Common Council.

“This is an issue that needed the city of Milwaukee to take some action,” Alderman James Bohl said during the committee meeting. Bohl is listed as a sponsor of the proposal, along with his fellow aldermen Nik Kovac and Michael Murphy.

Milwaukee would not be the first governmental body in Wisconsin to prohibit the use of coal-tar sealants. Dane County, for instance, banned the sealant in 2007.

The Wisconsin Department of Transportation, meanwhile, has specifically called for the use of asphalt-based sealants on state projects since the 1970s, said Barry Paye, chief materials engineer at the department.

Bohl said these previous restrictions have proved it’s possible to curtail the amount of PAHs that get into streambeds and lakebeds.

Austin, Texas, for instance, banned coal-tar sealants in 2006, making it one of the first cities to do so. Just four years later, city officials found that the amount of PAHs in one of Austin’s most-contaminated lakes had decreased by 58 percent.

Bohl said the possible countywide ban of coal-tar sealants has also been brought up with the Intergovernmental Cooperation Council, a group made up of representatives from each of the 19 cities and villages in Milwaukee County, as well as the county itself.

Erick Shambarger, sustainability director for the city’s Environmental Collaboration Office, praised the proposal.

“There’s mountains of evidence that this is nasty stuff that we don’t want in our waterways or tracking into our schools and daycares,” he said. “Ultimately I’d (like) to see a statewide ban, but I think taking action here and now is very appropriate.”

The proposal also has the backing of the city’s Department of Public Works. DPW officials already call for the use of asphalt-based sealants on their projects and have not had coal-tar-based sealants on a project since the late 1990s.