Toxic driveways? Cities ban coal tar sealants
Could your driveway be making you sick? Studies suggest a common sealant using coal tar contains hazardous chemicals that elevate lifetime cancer risk. So some cities and states are banning its use.
Barbara Mahler, a hydrologist with the U.S. Geological Survey who's researched the hazards of coal tar pavement sealant, takes a sample of parking lot dust in 2007 in Lake In the Hills, a suburb of Chicago. (Photo: Peter Van Metre)
- Driveways and parking lots are often sealed with coal-based products
- Studies suggest these products contain hazardous chemicals
- More local governments are banning them, but industry says they're safe
Could your driveway be making you sick?
Mounting research suggests it could. It's prompting more cities, states and businesses to ban a common pavement sealant linked to higher cancer risks and contaminated soil.
These sealants, used mostly in the eastern half of the USA to beautify pavement and extend its life, contain up to 35% coal tar pitch, which the National Toxicology Program considers a human carcinogen.
Last month, Minnesota became the second state — after Washington — to ban pavement sealants that contain coal tar, and the New York Assembly passed a similar bill. In April, Rep. Lloyd Doggett, D-Texas, reintroduced such legislation in the U.S. Congress.
Last week in Chicago, the city's Committee on Finance held a meeting to discuss a newly proposed ban on the sale or use of these sealants.
Officials are acting to limit the cost of removing and disposing of contaminated sediment in waterways.They've passed bans in recent years in dozens of cities and counties in Minnesota, Washington, D.C., Illinois, Texas, New York, Maryland and Washington state. Others, in six additional states, have restricted use.
"We're at a tipping point" in the movement against coal tar sealants, says Nick Kelso, owner of Minnesota-based Jet-Black International. His seal-coating company, which has franchises in 13 states, is phasing out its use of them. He's turning to the alternative: asphalt-based products that he says are improving, cost about the same and contain much lower levels of worrisome chemicals.
Major retailers such as Home Depot, Lowe's, Ace and United Hardware have stopped selling coal tar sealants. The product gradually wears off and breaks down into particles that are washed off by rain into streams, blown elsewhere by wind or tracked into homes on the soles of shoes. Some of its toxic compounds evaporate into the air, which is why sealed parking lots give off a strong odor.
In 40 urban lakes nationwide, scientists with the U.S. Geological Survey (USGS) found these sealants account for about half of hazardous chemicals known as polycyclic aromatic hydrocarbons, or PAHs, while vehicle-related sources such as motor oil account for one-fourth. They say the sealants elevate lifetime cancer risks.
The industry disagrees, saying government and academic studies are flawed and there's no definitive proof that its coal tar products cause harm.
"This is controversial science," says Anne LeHuray, executive director of the Pavement Coatings Technology Council, which has lobbied successfully against proposed bans. She says the product has been safely used for decades by applicators who follow industry guidelines. She says her group's repeated requests for detailed data from USGS research have been denied, so it has funded its own studies that raise questions about the federal government's findings.
"We have done rigorous, scientific surveys and analyses showing coal tar sealants are a major sources of PAHs in the environment," says Judy Crane, a water quality scientist at the Minnesota Pollution Control Agency who has co-authored USGS research.
Academic studies, including separate ones by the University of New Hampshire and Missouri State University, have also found elevated PAHs in areas adjacent to parking lots covered in coal tar.
"It's been a detective story," says Barbara Mahler, a USGS hydrologist who has co-led the government research. She says many Americans may be surprised to find their blacktops could be a danger: " It's been under our noses, but we've never really thought about it."
Not until a decade ago when officials in Austin suspected something was wrong. They found high PAHs in area waterways and, noting that nearby parking lots were newly coated with coal tar products, they surmised the sealants were the culprit.
Subsequent research by the USGS and other scientists backed that up. It found the PAH concentration in settled house dust in 23 ground-level Austin apartments adjacent to coal-tar-sealed parking lots was 25 times higher than the dust in apartments next to lots without such sealant.
A professional applicator applies a coal-tar-based sealant to a test plot used to measure emission of polycyclic aromatic carbons (PAHs) into the air in Austin at the University of Texas. (Photo: Justin McInnis, U.S. Geological Survey)
How bad is that? In a study released this year, Mahler and Baylor University scientist E. Spencer Williams calculated that lifetime exposure to PAHs, via house dust, was 38 times higher for people living near coal-tar-sealed pavement than those who weren't. About half of this dose occurs by age 6 and 80% by age 18. PAHs are toxic to mammals, birds, fish, frogs and plants, and seven are suspected human carcinogens.
LeHuray says there are more potent sources of PAHs in the environment that include not only car and power plant emissions but also wood smoke and grilled hamburgers. Given the commonality of these compounds, she says bans on coal tar sealants won't help cities but will cause her industry undue harm. She says asphalt alternatives don't last as long, so customers might give up on resealing pavement..
COAL TAR VS. ASPHALT
"It does what customers want it to do," she says, adding that they pick coal tar products over asphalt ones 85% to 90% of the time when both are offered.
"There are pros and cons to each product," says Lonnie Harris of West Suburban Asphalt Maintenance, based in the Chicago suburb of Carol Stream. He says asphalt wears off sooner than coal tar in high-traffic areas but does well in lower-use places such as driveways.
Both types — similar in density to a thick coat of paint — are water-based emulsions that are typically sprayed on asphalt pavement.
Hearris applied coal tar sealants to parking lots for years and says he got second-degree burns on his neck from carrying an applicator hose around his shoulders. He says he got lightheaded and had panic attacks, which would go away during his work's off-season.
"It's very difficult to attribute it to coal tar, but it was the only new chemical introduced into my system then," he says, noting he now uses only asphalt-based products and feels better.
"We're not seeing much of a difference in performance," says Kelso of Jet-Black International, adding that the industry is working to improve asphalt products. He says asphalt sealants aren't as smelly after application and don't burn a workers' skin upon contact.
"The evidence is on our side. The problem is trying to combat the lobbying of industry," says New York Assembly member Linda Rosenthal, D-Albany, whose ban on coal tar sealants passed the state's lower house but may have trouble in the GOP-controlled Senate.
The industry has managed to stop ban-related bills. Last month, it helped to defeat one — by a narrow margin — in Maine's House of Representatives and the same effort — by unanimous vote — in its Senate. It's stopped efforts in Illinois, Michigan and Maryland and in several cities, such as Des Plaines, Ill., and Springfield, Mo.
Coal tar pitch is among the residue that remains after coal is heated to make coke for steel. Some sealant manufacturers are vertically integrated into the steel business, so they have a "vested interest in the current product mix," says Al Innes, a Minnesota state official who's running an EPA-funded program to reduce the use of coal tar sealants. He'll hold webinars throughout the Great Lakes region this summer to prod businesses to shift to asphalt products.
"We're making progress," he says, noting schools are abandoning coal tar on playgrounds and parking lots and at least 73 contractors (24 in Wisconsin and 49 in Minnesota) have pledged to switch to asphalt sealants. He says there are few applications for which asphalt sealants won't work well.
Tom Ennis, a watershed protection official in Austin who tracks the issue on a blog called Coal Tar Free America, says bans have ebbed and flowed since his city passed the first one in 2005. He expects that the country is entering a period in which more bans will become law despite the industry's opposition.
"We've got more and more data, at the state and local level, showing it (coal tar sealant) is a problem," Ennis says.
LeHuray sees just the opposite. "As time goes by, our information is stronger," she says. Still, she says, some companies may make fewer coal tar sealants to avoid the "hassle" factor.
Kelso says the marketplace will continue to shift. If the movement against coal tar sealants continues, he says he'll be shocked if businesses continue to use them much longer, adding, "I can see, 10 years from now, they won't even exist."
HOW TO AVOID, TEST FOR OR REMOVE COAL TAR SEALANTS
Tom Ennis recommends these steps to avoid coal tar. He's an official in Austin, the first city to ban coal tar sealants, and oversees the Coal Tar Free America blog.
• Before sealing your driveway, hire only a contractor who provides a MSDS (material data safety sheet) for the intended product. Check to see if it contains this CAS number for coal tar: 65996-93-2. If doing the work yourself, buy only products with a "coal tar free" logo.
• You can't tell by looking at pavement if it contains coal tar, and definitive testing is costly, but there's an alternative for those careful to wear safety goggles and gloves: Scrape off a small amount of pavement sealant with a screwdriver or razor. Place it in a glass vial filled with mineral spirits. Seal and shake the vial. Allow it to sit for 30 minutes. If the liquid is dark and coffee-colored, the sealant is probably asphalt-based, but if it's like amber-colored tea, it's probably coal tar-based.
• If your sealant contains coal tar, you can hire contractors to remove it safely via shot blasting. You can also coat over it with an asphalt-based product to keep the coal tar from leaching out.