Recent studies have shown that asphalt sealant derived from coal tar (an industrial waste) poses a risk to human health. Asphalt sealants are usually sprayed onto parking lots and driveways to seal in asphalt. However, the chemicals found in coal tar are believed to cause cancer. Past research has established that coal tar causes cancer in humans, as well as genetic mutations in animals.
The chemicals found in coal tar believed to pose health risks are known as “polycyclic aromatic hydrocarbons,” or PAHs. PAHs can also be found in food that has been cooked at high temperatures such as food that has been fried or grilled. PAHs are produced whenever a substance with a carbon base is burned such as cigarettes, gasoline, meat, and wood. PAHs are considered to be toxic, and have been shown to cause cancer and birth defects in aquatic life. Seven forms of PAHs are thought to be human carcinogens.
Prior research has shown that tiny coal sealant particles are being washed by rain into nearby lakes and streams causing the aquatic life to become sick. Aquatic animals, such as fish, frogs, newts, and salamanders, contaminated by the chemicals found in coal tar sealants were found to suffer from developmental problems, liver issues, and stunted growth, among other things. What is concerning is that over the last two decades, the level of these chemical concentrations in our waterways have been rising even though concentration levels of other contaminants have decreased.
One way in which humans are exposed to the chemicals used in coal tar sealants is through house dust. Alarmingly, the U.S. Geological Survey (USGS) has found large amounts of PAHs vaporizing into the air off coal tar-sealed parking lots, and scientists have discovered that some of the toxic materials are being found in house dust in homes adjacent to these parking lots and driveways. In addition, the USGS discovered that PAH concentration levels in house dust in apartments with coal tar-sealed parking lots were 25 times higher than in house dust found in apartments which did not have coal-tar sealed parking lots. Small children are especially at risk of exposure due to the fact that they spend more time on the floor and are constantly placing their hands in their mouth. Research led by E. Spencer Williams, a human health risk assessment expert at Baylor University, has indeed found that children who put their hands in their mouth are receiving 9 ½ times more exposure of PAHs through house dust than through food. Scientists have yet to find out how toxic it is for children to play in playgrounds or parks next to coal tar-sealed asphalt or on the asphalt itself. However, the level of chemicals found on coal tar-sealed asphalt has been measured to be 37 times higher than what is found in house dust. Furthermore, in some cases, the level of PAHs found in coal tar-sealed lots were much higher than what a European Science panel recommended in order to guard against cancer.
The U.S Protection Agency does not classify coal tar as a hazardous waste material, even though it meets the standards of one, so that it can be recycled for purposes such as sealing asphalt. Coal tar sealants are used in all 50 states, but last year the state of Washington put a ban on coal tar sealant. Local governments in Washington D.C. and Austin, Texas have also placed a ban on coal tar sealant, preferring the use of an asphalt based sealant which only contains about 1/1000th of the concentration of cancer-causing chemicals as coal tar products. Nevertheless, 85 million gallons of coal tar sealant are used annually in the United States.
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