In our Backyard

From Stef 06 at the DEP:

Help Reduce the Pollutants, In Our Back Yard

Thinking about resealing the driveway this summer, might want to think twice ….

There are basically two types of driveway sealants on the market today. The first type is made from coal tar and the second from asphalt bases. The bases make the difference in how toxic these products are for you and the neighborhood stream or lake.

You might be thinking, wait a minute what does my neighborhood stream or lake have to do with driveway sealant? Research conducted in Austin, Texas found high levels of Polycyclic Aromatic Hydrocarbons or PAHs in some of their local streams. PAHs are linked to various health issues including cancer.

Researchers in Austin found hot spots of PAHs in streams and were able to trace them back to pavement sealers used on parking lots and driveways. They found that the average concentration of PAHs to be 1,600 times higher in coal tar based sealants than asphalt based sealants. For this reason, coal tar based sealants are a potentially higher health risk than asphalt based sealants.

But wait, how do these PAHs get from the driveway or parking lot into the neighborhood stream? When it rains or the snow melts, the stormwater carries with it little hitchhikers of whatever it hits or runs across, in this case, pavement sealants. The polluted stormwater runs off the pavement to a storm drain or ditch which drains to the local stream. In Austin they found that particles in runoff from parking lots sealed with coal tar sealants were 65 times higher in total PAHs than runoff from unsealed asphalt and cement.

A report from the Great Lakes Environmental Center in March, 2005 showed that coal tar sealants in sediments were toxic to the life in the streams at the concentrations observed in Austin streams.

So if you are considering sealing your driveway or parking area this summer read the labels and use asphalt based sealant; avoid coal tar based sealants. The asphalt based sealants may cost a bit more but they are more environmentally friendly and less toxic for you and our waters. Please do your part to keep Maine's lakes, rivers and streams healthy.

This column was submitted by Kathy Hoppe, an Environmental Specialist IV with the Maine Department of Environmental Protection's (DEP) Bureau of Land and Water Quality. In Our Back Yard is a weekly column of the DEP. E-mail your environmental questions to infoDEP@maine.gov or send them to In Our Back Yard, Maine DEP, 17 State House Station, Augusta, ME 04333.