Smoldering its way across the U.S., the question of whether municipalities and retailers should act on a ban of coal tar-based pavement sealants won’t quite go out – but hasn’t fully engulfed, either.
For 60 years the midwest, southern and eastern United States have applied a diluted formula of the toxic by-product of Iron coke smelting across bare land like Turtle Wax on a Mustang. Ninety percent of Chicago’s driveways are coal-tar sealed, and Hydrologist Peter Van Metre of the United States Geological Society estimates 30 to 40 percent of the vehicle spaces in four recently-tested watersheds in the South, West and Midwest are covered with the compound.
Coal tar sealant’s superior impermeability compared to asphalt sealants makes it makes it an effective protector of surfaces likely to come in contact with fuel. The product is infrequently used in road construction, though, due to contamination concerns and because it breaks down more quickly than asphalt, or oil-based, sealcoats.
Since 2006 a list of municipalities that have banned the product’s sale and use has developed in response to persistent, if not overwhelming, contamination concerns.
That year, the USGS began testing sites for the carcinogenic, polycyclic aromatic hydrocarbons present in coal tar. It quickly identified the PAHs in coal tar as a “major source” of contamination in urban areas where the product is heavily preferred over asphalt sealcoat.
PAHs are established animal carcinogens, and have been confirmed as human carcinogens by the U.S. Department of Health and Human Services, although detractors maintain that human studies of PAH exposure are hampered by the mix of compounds that humans ingest.
Among the USGS’s key findings were that half of all PAHs found in 40 urban lakes can be attributed to coal tar-based sealcoat; that residences next to coal tar-sealed parking lots have PAH concentrations 25 times higher than those found in the house dust of residences next to parking lots not sealed with coal tar pitch; and that dust collected directly from pavement with coal-tar-based sealcoat had PAH concentrations hundreds to thousands of times higher than dust from pavement with no sealcoat or with asphalt based sealcoat. Coal tar sealants and the dust generated when they break down have been found to contain higher levels of PAH than other PAH sources like soot, vehicle emissions and even used motor oil.
Coal tar-sealed parking lots contained 530 times more PAHs than dust from parking lots with other surface types. Rainwater washes sealant particles and dust down storm drains and into local streams and rivers. The USGS has documented upward trends in the amount of PAHs in urban lakes concentrations allegedly causing mutations in marine life. But the most direct human contact with PAHs comes from inhaling coal-tar-containing household dust.
Moves to ban
USGS policy is to refrain from making legislative recommendations based on their work. But the EPA has preliminarily corroborated the USGS’ findings and concerns regarding PAH levels in water runoff and its negative effects on aquatic life.
Austin, Texas, which first rang the coal tar sealant warning bell in 2005, didn’t wait
for consensus. It banned the sale or use of Refined Tar-Based Pavement Sealers
in 2006 as a “precautionary” measure. Dane County, Wis., did the same in 2007,
followed by the District of Columbia in 2009, several suburbs of Minneapolis, Minn., and numerous other municipalities. McHenry County, Ill., Administrator Peter Austin and Water Resources Director Cassandra McKinney have collected “tons” of material condemning coal tar sealant since McKinney became aware of the potential hazard four years ago. Two, four-inch thick binders of scholarly, peerreviewed and non-bias studies document her cause for concern.
“We really researched this, and haven’t found anything yet that tells us it’s not bad,” McKinney said.
As a non-home rule community, McHenry County lacks the authority to ban coal tar sealants on its own. But McKinney and Austin feel strongly enough about the product’s dangers that they’ve taken the step of requesting permission from the state of Illinois to ban coal tar on the 2012 Illinois legislative agenda.
Industry representatives insist that the USGS’ findings are flawed due to incorrect methodology and that intervention is an overreaction, According to a report prepared by Robert DeMott of Environ corporation, even Denorex dandruff shampoo contains a higher percentage of PAHs than coal tar sealant. In a presentation prepared for the Pavement Coatings Technology Council, DeMott alleged that the levels of PAH contamination that alarmed Austin were no higher than levels found in more than a dozen other bodies of water in Minnesota, New York, New Jersey, Texas, Virginia and Washington.
PCTC Executive Director Anne LeHuray points out that, first of all, the sealant’s components can’t pollute the water if they’re water insoluable. Rather, PAHs accumulate in sediment. At PCTC’s initiative, environmental forensic analyses were done after the USGS’s initial studies. Not only were coal tar PAHs acting not acting alone in the environment, but could not be determined to be the cause of pollution, she said.
She added that if coal tar sealant was a significant danger, it’s unlikely that it would have failed to show up before now.
“This is a product that has been used extensively for four decades. Many of the people who apply it are in multigenerational, family-owned businesses. If there was a health concern, wouldn’t it have shown up in those families?”
In recent years, sealcoat manufacturers have been successful refining the performance of asphalt emulsion sealers through the use of specialty chemicals and pigments. But asphalt emulsion’s resistance to petrochemicals and solvents — while improved — has yet to be perfected. Federal Aviation Administration Specifications accept only refined coal tar-based sealcoatings for use on airport projects, because asphalt tends to soften with fuel.
In spite of its deficiencies, some sealcoaters recognize advantages of asphalt emulsion over refined coal tar sealers that include their user friendliness, lack of odor and irritation to lungs and sensitive skin.
COAL TAR SEALANT BANS
Austin, Texas • Bee Cave, Texas • Buffalo, Minn. • Centerville, Minn. • Circle Pines, Minn. • Dane County, Wis. • Edina, Minn. • Golden Valley, Minn. • Inver Grove Heights, Minn. • Home Depot Stores Throughout US • Little Canada, Minn. • Lowes Stores Throughout US • Maplewood, Minn. • New Hope, Minn. • Prior Lake, Minn. • Roseville, Minn. • Suffolk County, N.Y. • Vadnais Heights, Minn. • Washington, D.C. • State of Washington • White Bear Lake, Minn.
RESTRICTED USE JURISDICTIONS
Boone, N.C. • Commonwealth of Massachusetts • Sudbury, Mass.
GOVERNMENT USE RESTRICTIONS
Lake in the Hills, Ill. • McHenry County, Ill. • State of Minnesota
Spring Grove, Ill. • Springfield, Mon.
By Jodi Magallanes