Study sees parking lot dust as a cancer risk


JF-Expert Member
Feb 3, 2009


JF-Expert Member
Joined Feb 3, 2009
39,792 4,940 280
Sealant doesn't stay put on pavements, raising health concerns

Peter Van Metre
Coal tar sealcoat is applied at a test site at the University of Austin in Texas, where it was studied for a year.
View related photos

By Robert McClure
updated 10:02 a.m. ET Jan. 12, 2010

Chemicals in a cancer-causing substance used to seal pavement, parking lots and driveways across the U.S. are showing up at alarming levels in dust in homes, prompting concerns about the potential health effects of long-term exposure, a new study shows.
The substance is coal tar sealant, a waste product of steel manufacturing that is used to protect pavement and asphalt against cracking and water damage, and to impart a nice dark sheen. It is applied most heavily east of the Rockies but is used in all 50 states.
But scientists with the U.S. Geological Survey say the sealant — one of two types commonly used in the U.S. — doesn’t stay put. It slowly wears off and is tracked into homes on the shoes of residents. The USGS study, which found high levels of chemicals used in the sealant in house dust, marks the first time researchers have raised alarms about potential health effects for humans — especially young children — from the parking-lot coatings.
Taken with previous studies indicating that the chemicals contaminate waterways, where they have been shown to harm insects and tadpoles, the finding raises serious questions about the advisability of using coal tar as a sealant, the scientists say.
“This is the kind of thing where, when you give a presentation, people’s eyes get big — even scientists,” said Barbara Mahler, a USGS hydrologist who directed the latest research.
The scientists’ published their research Monday in the journal Environmental Science & Technology. The research, which examined both parking lot dust and dust tracked into homes, focused on a class of chemicals known as polycyclic aromatic hydrocarbons, or PAHs, which are a significant component of [ame=""]coal tar[/ame].
A known carcinogen
Coal tar is known to cause cancer in humans. That finding dates to the 1770s, when chimney sweeps in London were found to have high levels of scrotal cancer. Late the next century, it was associated with skin cancers among creosote workers. PAHs themselves are listed by the U.S. Environmental Protection Agency as a probable human carcinogen, based on laboratory studies in which they caused cancer in animals.
Emerging evidence also suggests that babies exposed to PAHs while in the womb may be more prone to asthma and other ailments, and may have lowered IQs.
Peter Van Metre​
A researcher vacuums up dust from an Austin apartment used in the house dust study.
The new U.S.G.S. study compared house dust from 23 ground-floor apartments in Austin — 11 with coal tar-sealed parking lots and 12 coated with other substances, or not sealed at all. The study found that dust in the apartments next to the coal-tar-sealed lots had PAH pollution levels 25 times higher, on average, than the other lots.
More than half the apartments with the coal tar-sealed lots contained dust with levels of PAHsthat would increase the risk of cancer if ingested by preschoolers, the researchers said. They came to this conclusion by comparing their results to a 2008 study that estimated those risks based on lab tests on animals. The increased risk means one additional child in 10,000 would develop cancer if exposed to that level of toxins over a lifetime.
Although adults are at risk from toxic pollutants in house dust, young children are especially vulnerable, studies have shown. That’s because they have a higher metabolic rate, they get a bigger dose per pound of body weight, their organs are still developing and they play on or near floors where carpets concentrate and retain toxics. Stanford University researchers have recorded children putting their hands on contaminated surfaces, such as floors, and then into their mouths up to 60 times an hour.
The new research on parking lots is important because scientists have been trying to figure out the sources of PAHs for years, said Ted Schettler, science director of the Collaborative on Health and the Environment, a group of medical professionals trying to reduce environment-related diseases.
“This parking lot (research) is very interesting because it could be there’s a large contributor out there that people didn’t know about,” said Schettler, who was not involved in the research.
Components of coal tar escape parking lots and driveways — not from most public roads — and get into the environment, causing stunted growth in creatures that live in streams, scientists have shown. Research also reveals that the chemicals in coal tar kill tadpoles, cause tumors on fish and eliminate whole species of tiny aquatic creatures near the base of the food chain.
Congressman calls for national ban
One congressman — Rep. Lloyd Doggett, D-Texas — is calling for a nationwide ban of the coal tar pavement sealants, which are applied by big contractors as well as operators with little more than a truck and a spray tank.
Not only was the toxic house dust found in apartment units surrounded by paved parking lots, but USGS researchers also measured contamination in dust from apartment house parking lots and the driveways of a few single-family homes. The most dangerous coal tar component — a PAH chemical called benzo[a]pyrene – was found in driveway dust at two suburban single family homes at thousands of times the level that would trigger a cleanup at a toxic-waste site.
The United States has no standard for benzo[a]pyrene in house dust, but Germany has an official guideline of 10 parts of the chemical for every 1 million parts of dust, which it says is necessary “to avoid adverse health effects.” In the U.S.G.S. tests of apartments near coal-tar lots, a third of the apartments showed levels of the toxic chemical exceeding that standard.
Some PAHs, including benzo[a]pyrene, are “highly potent” when it comes to causing cancer, according to the EPA.
The EPA did not provide a representative to discuss the new findings with InvestigateWest, despite repeated requests. Doggett began asking for EPA action in 2003. In 2009 the agency launched research on coal tar sealants that is expected to be completed this year. In a July letter to Doggett and answers to written questions from InvestigateWest last month, the agency did not offer an explanation for the delay.
No solid figures on usage
While there are no reliable estimates of the total amount of the coal tar sealants applied to pavement nationwide, the industry has said that some 59 million gallons — enough to fill nearly 90 Olympic-sized swimming pools — are applied in Texas each year. In the much-smaller watershed surrounding New York City’s harbor, something like 1.4 million gallons is estimated to be applied annually, according to a 2007 study for the New York Academy of Sciences.
Local governments in Austin, Washington, D.C., and the county that includes Madison, Wis., have banned pavement sealants containing coal tar after findings of PAHs in local waterways. In its place, they rely on the second main type of sealant used in the U.S., which is asphalt based.
But a spokeswoman for a trade group of companies that apply the coal tar sealants said research has not been comprehensive enough to justify such bans. Anne P. LeHuray, director of the Pavement Coatings Technology Council, said people who advocate bans are looking for a “magic bullet” to solve a complicated problem.
She points out that cancer-causing chemicals contained in the pavement sealants also get into cities and suburbs from a number of other sources, including motor oil, vehicle exhaust and tires.
“Right now the research is not that convincing that this is that important a source of PAHs relative to all the other sources that are out there,” LeHuray said. “They didn’t look at all the potential sources.”
CONTINUED : A tiny toxic creek1 | 2 | Next >

Forum statistics

Threads 1,190,287
Members 451,082
Posts 27,666,623