Science Features
USGS scientist Peter Van Metre examines a parking lot where coal-tar sealcoat has been applied.A USGS scientist adjusts an air pump used to measure emission of polycyclic aromatic carbons (PAHs) into the air.
What is sealcoat?
Coal-tar-based sealant is the black liquid sprayed or painted on many parking lots, driveways, and playgrounds.
Several PAHs are probable human carcinogens, and many are toxic to fish and other aquatic life. Coal tar, which can cause cancer in humans, is made up of more than 50 percent PAHs. An estimated 85 million gallons of coal-tar-based sealant are used on parking lots and driveways each year, primarily in the central and eastern United States.
What are the rates of PAH emissions to the air from coal-tar-based sealcoat?
Coal-tar-based sealants are emitting PAHs into the air at rates that could be greater than annual emissions from vehicles in the United States based on a study in which USGS scientists tracked PAH levels in air and in dried sealcoat following sealcoat application to a parking lot. Two hours after sealcoat application, PAH emissions were 30,000 times higher than those from unsealed pavement. In a second study, USGS scientists measured PAHs in air above parking lots with and without sealcoat, in suburban Austin, Texas. Parking lots with three- to eight-year-old sealant still released 60 times more PAHs to the air than parking lots without sealant.
A USGS scientist adjusts an air pump used to measure emission of polycyclic aromatic carbons (PAHs) into the air.
Children living near sealed parking lots are exposed to PAHs
Children living near coal-tar-sealed pavement are exposed to twice as many PAHs from ingestion of contaminated house dust than from food, according to a separate new study by Baylor University and the USGS. Baylor University scientist Spencer Williams used USGS measurements of PAHs in house dust to estimate the potential ingestion of PAHs by young children living near coal-tar-sealed parking lots. Ingestion of PAHs from food has long been thought to be the primary route by which children are exposed to PAHs. PAH ingestion by children living near coal-tar-sealed parking lots is estimated to be 14 times higher than by children in apartments adjacent to unsealed parking lots.
Sealcoat is a major source of PAHs to the environment
Past and current research on environmental contamination and coal-tar-based pavement sealants and implications for human health and stormwater management are summarized in a new Feature Article in the journal Environmental Science and Technology. The article is jointly authored by researchers with the USGS, Minnesota Pollution Control Agency, University of New Hampshire, City of Austin, Texas, and Baylor University.
Bans on coal-tar sealcoat
Some governments have taken action on the use of coal-tar-based sealcoat. Fifteen municipalities and two counties in four states (Minnesota, New York, Texas and Wisconsin), the District of Columbia and the state of Washington all have enacted some type of ban, affecting almost 10.4 million people. Several national and regional hardware and home-improvement retailers have voluntarily ceased selling coal-tar-based driveway-sealer products.
Coal-tar sealcoat compared to asphalt-based sealcoat
USGS scientists prepare a sampler used to measure emission of polycyclic aromatic carbons (PAHs) into the air.
Two kinds of sealcoat products are widely used: coal-tar-based and asphalt-based. The coal-tar products have PAH levels about 1,000 times higher than the asphalt products. Coal-tar-based sealcoat is more commonly used in the Midwest, southern, and eastern United States. Asphalt-based sealcoat is more commonly used in the western United States. Consumers can determine whether a product contains coal tar by reading the product label or the associated Materials Safety Data Sheet (MSDS), available from the applicator, retailer or on the Internet.
For more information, please visit the USGS website on PAHs and sealcoat, or contact Jennifer LaVista.
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Please comment on the USGS’ draft science strategies! Read more
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National Groundwater Awareness Week is Mar. 11-17, 2012. See how USGS science is connecting groundwater and surface water.
Since Japan’s March 11, 2011, Tohoku earthquake and subsequent tsunami, scientists at the USGS have learned much to help better prepare for a large earthquake in the United States.
Five USGS employees honored with Distinguished Service Awards for their service to the nation
Meet a member of the next generation of USGS hydrologic technicians.
Meet a member of the next generation of USGS hydrologic technicians.
It’s National Invasive Species Awareness Week. Did you know invasive species cost our country more than 100 billion dollars each year? Get to know America’s ten top invaders this week.
Groundwater in aquifers on the East Coast and in the Central U.S. has the highest risk of contamination from radium, a naturally occurring radioactive element and known carcinogen.
The proposed USGS budget reflects research priorities to respond to nationally relevant issues, including water quantity and quality, ecosystem restoration, hydraulic fracturing, natural disasters such as floods and earthquakes, and support for the National Ocean Policy, and has a large R&D component.
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As the team of responders struggled to end the worst oil spill in our Nation’s history, USGS scientist Paul Hsieh provided the critical scientific information needed to make a crucial decision.
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The Chesapeake Bay has long been an R&R destination for DC residents. However, the watershed’s overpopulation contributes to its decline. Join us when USGS’s Scott Phillips and Peter Claggett discuss new science efforts applied to restoring the Nation's largest estuary on October 6th.
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The United States Group on Earth Observations (USGEO) is working to connect Earth observations with public health, agriculture, climate, and data management and dissemination.
The USGS Science Strategy is a comprehensive report to critically examine the USGS's major science goals and priorities for the coming decade. The USGS is moving forward with these strategic science directions in response to the challenges that our Nation's future faces and for the stewards of our Federal lands.
7 p.m.—Public lecture (also live-streamed over the Internet)
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On Nov. 3, USGS scientists Patrick Barnard and William Ellsworth will present a public lecture in Menlo Park, CA, providing Bay Area residents information about USGS research in the San Francisco Bay Area, including recent discoveries beneath San Francisco Bay and ongoing studies to better understand earthquake probabilities and the potential hazards associated with strong ground shaking.
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7 p.m.—Public lecture (also live-streamed over the Internet)
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Join us in Menlo Park for our Evening Lecture on Scanning the Seafloor with Sound!
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Over the next 10 years, the USGS plans to conduct a new assessment of water availability and use. This national Water Census will address critical aspects of recent Federal legislation, including the need to establish a national water assessment program.
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USGS scientists will join thousands of scientists, managers, and decision makers in Boston this week to present new findings on toxics at the Society for Environmental Toxicology and Chemistry (SETAC) conference in the Hynes Convention Center, Nov. 13-17.
On Nov. 3, USGS scientists Patrick Barnard and William Ellsworth will present a public lecture in Menlo Park, CA, providing Bay Area residents information about USGS research in the San Francisco Bay Area, including recent discoveries beneath San Francisco Bay and ongoing studies to better understand earthquake probabilities and the potential hazards associated with strong ground shaking.
Rivers and streams in the United States are releasing substantially more carbon dioxide into the atmosphere than previously thought.
Meet the R/V Muskie and the R/V Kaho, the USGS Great Lakes Science Center's two newest additions to its Great Lakes research fleet!
U.S. Department of the Interior |
U.S. Geological Survey
URL: www.usgs.gov/blogs/features/usgs_top_story/coal-tar-sealcoat-a-major-source-of-pahs-to-air-and-to-children-living-nearby/
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Page Last Modified: September 14, 2011
