Study Sees Parking Lot Dust as a Cancer Risk
Tamara R Pearlman
by Robert McClure | InvestigateWest
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.
updated 10:02 a.m. ET,Tues., 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 coal tar.
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.
A researcher vacuums up dust from an Austin apartment used in the
house dust study.
Peter Van Metre
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 o f 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.”
A tiny toxic creek
The path that led to the discovery of the toxic dirt inside Americans’
homes traces back to a tiny creek in Austin, Texas.
When researcher Mahler saw test results on dirt scooped from the
bottom of a tributary of Barton Creek in 2001, the pollution readings
for PAHs were so high she felt certain someone had made an error. The
concentrations found in a drainage ditch leading from a parking lot
to Barton Creek were higher than levels typically measured at toxic-
waste sites — higher even than Boston’s notoriously polluted Charles
River, where PAHs are listed as among the “contaminants of concern”
on that major industrial waterway.
Further testing showed the high readings were accurate. But what was
the source?
Barton Creek feeds Barton Springs, a public bathing site cherished by
Austin residents because it offers a cool respite from tyrannically
hot Texas summers. Levels of PAHs measured in Barton Springs were
high enough that the Austin American-Statesman dispatched reporters to
track down what was suspected to be a hidden toxic waste dump along
Barton Creek where city biologists had pinpointed extremely high
levels of PAHs.
“I spent a good half an hour walking around looking for cars gushing
out fluid or someone dumping stuff, but none of that was happening,”
Bashara recalls.
He did notice that the parking lot was a rich black color. Then he
noticed the deep black color had been rubbed off by cars’ tires in
some places. So it was newly sealed.
He moved on to other pollution hot spots on the creek, where he found
more parking lots colored the same deep, rich black.
“That’s when it dawned on me: There’s some connection between the seal
coat and the hot spots,” Bashara said.
Tadpoles in toxic Dixie Cups
A series of scientific studies followed.
In one, Mahler and her colleagues demonstrated that the particles of
dirt in water running off a parking lot with coal tar sealant had PAH
levels about 65 times higher than those from water running off lots
where no sealant had been applied.
In another, tadpoles were put into containers with high, medium and
low levels of PAHs pollution. The tadpoles in the cups with the
highest concentration all died within six days, said Mateo Scoggins, a
City of Austin biologist. The ones exposed to medium and low levels of
PAHs, comparable to the concentrations in Barton Creek, showed stunted
growth.
Researchers from the city of Austin and Texas Tech University also
looked at how the PAH pollution was affecting life in the creeks in
Austin, and found a reduced number of insects available for birds,
frogs and other creatures to eat.
That, said Scoggins, indicated that “there is more of a problem . . .
than we thought.”
Sweeping the parking lot
Scientists from the USGS Texas Water Science Center involved in the
Barton Creek findings measured pollution in lakes around the country,
noting an increase in PAHs. In the next phase of their inquiry, they
swept up dust in parking lots in Seattle, Portland, Salt Lake City,
Minneapolis, Austin, Chicago, Detroit, Washington and New Haven,
Conn.
Coal tar sealants are used predominantly in the East, and that’s where
the highest PAH readings were found — roughly 1,000 times higher than
those in the West, where it’s much more likely that a driveway or
parking lot will be coated with an asphalt sealant.
That figures, because the levels of PAHs in coal tar sealants is about
1,000 times what it is in asphalt sealants, researchers have found.
One parking lot near Seattle had high pollution levels, while the
other Western readings were relatively low.
The big question is how do parking lots figure into the big picture on
these growing levels of PAH contamination?
USGS researchers, led by hydrologist Peter Van Metre, expect they will
soon have an answer. Research expected to be finalized in coming
months will analyze the “fingerprint” of PAHs in various lakes to
determine the source of the chemicals.
“We’re able to isolate the (parking lot) seal coat in some of these
settings as the only really logical source,” Van Metre said.
The 'poster child' community
The “poster child,” he said, may be Lake in the Hills, a town
northwest of Chicago. In the last two decades it went from a small
town tucked amid cornfields to a sprawling suburb dotted with big-box
stores. Roughly 40 percent of the paved areas that drain into the
town’s manmade lake had been covered with seal coating. PAH pollution
levels in the lake went up tenfold, Van Metre said, and the
contamination included the two homes with PAH levels in their
driveways at thousands of times the amount that would trigger a toxic-
waste site cleanup.
That earlier study in the Journal of Environmental Science and
Technology found that on average, the PAHs were 530 times higher in
the parking lots sealed with coal tar.
For his part, Doggett, the congressman representing the Austin area,
is glad that EPA is finally taking seriously the threat posed by the
coal tar sealant.
“Under the prior administration, I confronted EPA inaction and
excuses. I am pleased my repeated efforts have resulted in the EPA
now initiating this long-overdue work, and we might finally move
toward a nationwide ban on this dangerous substance,” Doggett said in
a written statement.
Researcher Van Metre said the public doesn’t have to accept increasing
levels of pollution as a price of development.
“Just because we live in urban environments — and most people do live
in urban environments — doesn’t mean they have to be polluted,” he
said.
InvestigateWest is a non-profit investigative news organization
covering the environment, health and social justice. Find out more at
www.invw.org.
URL: http://www.msnbc.msn.com/id/34809699/ns/us_news-%20environment/