Studies See Toxic Risk from Coal Tar Pavement Sealants

Four new studies claim coal tar-based asphalt sealants pose serious health risks to the public.

According to an report, the studies confirm the widespread belief that asphalt sealants sprayed on freshly paved driveways and parking lots pose much more serious health risks than its alternative. These sealants contain chemicals in the class known as polycyclic aromatic hydrocarbons (PAHs).

These sealants are used to protect and preserve new asphalt. It is sprayed onto a parking lot or driveway and gives the paving a deep black color, something most consumers desire as a finished look. That look, using this traditional material, comes at a cost, based on the findings of these recent studies.

Coal tar-based sealants use the byproducts of steel making. The material was declared to not be a hazardous waste about 20 years ago by the Environmental Protection Agency, namely because of its use as a driveway sealant. Prior to and since then, use of coal-tar based asphalt sealants has been on the rise, with as much as 85 million gallons applied in the U.S. last year.

The recent studies highlight some of the gravest dangers of using these sealants containing high levels of PAHs. In comparison, new alternative forms of asphalt sealants (which are asphalt-based) contain just one-thousandth of the amount of toxic PAHs.

In one study conducted at Baylor University, children living closest to driveways and parking lots where coal tar-based sealants suffered more than 9-times higher PAH exposure from house dust than they did their food, where most PAH exposure traditionally derives because cooking foods through grilling, frying or roasting often create PAHs.

In addition to being exposed to PAHs through their food, the same children living near these sealed lots are exposed to even higher levels of the toxin.

Researchers at the U.S. Geological Survey determined that vapors rising off driveways and parking lots across the country have created a more toxic environment – especially when comparing levels of PAH in the air – than some of the most industrial centers around the world, where PAHs are released into the air from power plants.

Air just four feet above a parking lot or driveway with a coal-tar based sealant was discovered to have dangerous levels of PAHs, high enough to be considered carcinogenic by the European Union. Those same standards have not been adopted by domestic regulators, though.

Also, the widespread use of these sealants on parking lots, driveways and even on playgrounds has created more PAH pollution than all automobile exhaust worldwide.

Use of these sealants have a harmful effect on more than just air. Rain and other wet weather can erode the PAHs in the sealants, causing them to wash off into storm drains, into groundwater or into nearby streams or creeks. PAHs are also tracked into homes simply by people walking on lots or sidewalks where the sealants are applied.

While use of these sealants is still considered widespread, a safer alternative is available and earning a share of the market namely because some retailers have agreed to stop selling the more toxic sealants. According to the report, some local governments have stopped using coal-tar sealants on their lots and driveways and national retailers Home Depot and Lowe’s have stopped marketing these products.

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