Prince George’s County joined the District of Columbia and Montgomery County, MD, when its ban of coal tar pavements went into effect at the beginning of July. This category of thick brown or black liquid is a byproduct of the carbonization of coal that has been used for decades to seal driveways, parking lots, playgrounds and recreational trails to extend the life of asphalt and concrete surfaces.PAHs are one of the major classes of contaminants associated with urbanization. In addition to coal tar, they are also created by various other forms of combustion, including barbecuing and grilling. There's absolutely no doubt they can be both acutely poisonous and carcinogenic, but as with many poisons, it also has medicinal uses. Coal tar extracts are used in medical and dandruff shampoos (which often smell like hot pavement. Coal tar extract (creosote) is also used to treat wood to make it rot and insect resistant.
But mounting evidence shows that these products, to which there are alternatives, contribute toxic chemicals that persist in waterways and harm human and wildlife health. The coal tar products contain high levels of polycyclic aromatic hydrocarbons (PAHs) that are toxic to fish and cause cancer in humans.
A study in the April issue of the journal Environmental Science showed runoff from coal tar-sealed pavement remained deathly toxic to minnows and water fleas (which make up the base of the food chain) in rainwater runoff as long as three months after coal tar sealant was applied.
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Fred Pinkney, toxicologist with the Chesapeake Bay Field Office at U.S. Fish and Wildlife Service, said it’s difficult to know how widely PAHs are used in the Bay watershed. Coal tar sealants are more widely used east of the Mississippi River and less toxic asphalt sealants are largely used in the West, he said.
The U.S. Geological Survey has conducted most of its research on the substances out of Austin, TX, which was one of the first municipalities to ban the sealants. Washington and Minnesota have statewide bans on the coal tar products, and cities in two dozen states have some form of ban or restriction on the products, according to the advocacy group Coal Tar Free America.
Coal tar sealant often requires reapplication every two to five years where tires and snowplows reduce the coating to a fine dust. The dust, which contains high concentrations of PAHs, can be blown, washed or tracked into nearby soil and waterways and can persist for years after application, according to research by the USGS.
According to their research, people living next to coal tar-sealed pavement are 38 times more likely to get cancer during their lifetime and are at a greater risk if they lived there during early childhood.
While I suspect coal tar driveway sealant has been used on our driveway. I would support a similar ban in my community.