Thursday, December 3, 2015

What Are the Health Implications of Using Coal-Tar Sealants on Driveways and Parking Lots?

Ball-and-stick model of the retene molecule, a...
Ball-and-stick model of the retene molecule, a polycyclic aromatic hydrocarbon present in coal tar. (Photo credit: Wikipedia)
Studies Raise Questions about Pavement Sealers (2 page pdf, Environ Health Perspect. 2012 May 1, 2012)

Also discussed here: Public Health Statement - Polycyclic Aromatic Hydrocarbons (Pahs) (6 Page Pdf, Department Of Health And Human Services, Public Health Service Agency For Toxic Substances And Disease Registry, Center For Disease Control, Aug. 1995)

And here: A review of airborne polycyclic aromatic hydrocarbons (PAHs) and their human health effects (Abstract, Ki-Hyun Kim, Shamin Ara Jahan, Ehsanul Kabir, Richard J.C. Brown, Atmospheric Environment, Oct. 2013)

 Today we review a short article that discusses the pros and cons of applying a sealant to driveways. The biggest pro is improving the cosmetic appearance of the driveway. The biggest con is that coal-tar based sealants act as source of polycyclic aromatic hydrocarbons (PAHs) for as long as eight years after the initial application, in addition to producing14.5 times higher concentration of PAH-contaminated indoor dust in residences located next to treated pavements. An asphalt pavement structure should last virtually forever if a thin coat of repaving is applied after 20 years along with interim crack sealing. The health impacts from exposure to PAH for long periods include a higher risk of cancer as well as cataracts, kidney and liver damage and jaundice.  

Key Quotes:

"Asphalt is used extensively to pave parking lots, driveways, airport runways, roads, playgrounds, paths, and other surfaces. … can help prevent pavement degradation and improve appearance, and they are used across the United States on all types of asphalt surfaces, with the exception of roads. “

Coal tar–based sealers contain an average concentration of 16 polycyclic aromatic hydrocarbons (PAHs) about 1,300 times greater than that found in asphalt-based sealers” “ingestion of PAH-contaminated indoor dust via hand-to-mouth contact was on average 14.5 times higher for young children living in apartments next to parking lots treated with coal tar–based sealer compared with children living next to untreated parking lots.”

“During the hottest part of the day they found that average concentrations of eight PAHs about an inch above the surface were 19 times greater for the coal tar–treated lots than for unsealed lots, and were 5 times greater about four feet above the surface”

“The PAH concentrations over the sealed lots were 3.2 times greater during the heat of the day than during the coolest part of the day, and the average rate of volatilization during the day was 62 times greater for coal tar–treated lots than for unsealed lots, “

“in the United States each year, the mass of emissions of six major PAHs within the first 16 days after application of all coal tar–based sealer projects may be about 20 times greater than that from all annual vehicle emissions.”

“PAHs can be harmful to your health under some circumstances. Several of the PAHs… have caused tumors in laboratory animals when they breathed these substances in the air, when they ate them, or when they had long periods of skin contact with them. Studies of people show that individuals exposed by breathing or skin contact for long periods to mixtures that contain PAHs and other compounds can also develop cancer.”

“The occurrence of PAHs in ambient air is an increasing concern because of their carcinogenicity and mutagenicity.”

Health effects from chronic or long-term exposure to PAHs may include cataracts, kidney and liver damage and jaundice. “

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