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The use of coal tar sealcoat has been restricted in several communities in Michigan, and has been banned for use or sale completely in Ann Arbor, Van Buren Township and Spring Lake Township. The state of Minnesota and Washington D.C. have also banned the application of coal tar sealants, and proposals to ban the use of the product across Michigan have already been proposed in the state legislature.
Much of the research on PAHs and coal tar-based sealcoat began in 2003 when staff with the city of Austin, Texas found elevated PAH concentrations in some sediment samples collected from small tributaries and drainage in largely residential areas. Such concentrations, researchers with the USGS said, were typically found near manufactured gas plant Superfund sites. The city staff in Austin hypothesized the source came from particles eroded from parking lots that were coated with coal tar-based sealcoat. Subsequent studies by the USGS determined the source to be coal tar-based sealcoat that flake and cling to sediments when washed away by stormwater.
The research resulted in Austin passing a ban on the use and application of coal tar sealants – the first such ordinance in the country.
Judy Crane, a research scientist with the Minnesota Pollution Control Agency, said a study of stormwater ponds and lakes in the state showed about 67 percent of PAHs in those sediments come from coal tar sealants.
"The Minnesota Pollution Control Agency requires municipalities to measure PAH compounds and metals in sediments before they dredge them. They were finding some (sediments) with really high levels, and because of that, they had to dispose of that sediment in a lime-lined landfill. Some were getting estimates of about $250,000 to dispose of it," she said. "At that point, we weren't sure what the source was, but I was familiar with some of the USGS work, and suspected coal tar sealants. And the study confirmed that."
As a result, the use of coal tar based sealants in Minnesota has been banned across the state. However, not everyone agrees with the research.
Anne LeHuray, executive director of the Pavement Coatings Technology Council, which represents dozens of sealcoat manufacturers across the country, said she believes research by the USGS and others that are blaming sealcoat as a source of PAHs is based on faulty science that is skewed to find the results those agencies sought.
"They are basing it all on – not just flawed science – but bad science," she asserted. "I went to Van Buren Township and asked them if it was their goal to ban PAHs, and if they are going to ban other sources – the employees in these communities aren't experts – and they said no....continued on page 3