Get the Facts! We found a great information sheet out of New Hampshire that explains how seal coat can be dangerous and what to do about it.
Coal-tar and asphalt based sealants are used across the nation to protect and beautify parking lots, roads and driveways. These sealants are used commercially and by homeowners on driveways, playgrounds, and parking lots.
Scientific studies have identified coal-tar sealcoat (CTS) as a major source of polycyclic aromatic hydrocarbon (PAH) contamination in urban areas for large parts of the nation. PAHs are a concern because several are suspected or probable human carcinogens and are also toxic to aquatic life. The research is still ongoing with regard to PAHs and there are no acute or chronic exposure levels in the US at this time.
Other communities are noticing elevated levels of PAHs in their storm water pond sediment and are finding that is it very costly to properly dispose of this contaminated sediment. In River Falls, we have over 90 storm water management ponds that collect sediments prior to water discharging to the river.
Asphalt based sealants are similar to coal tar in their use and application. Asphalt sealants are also cheaper than CTSs; however, their effective life is shorter at 4-6 years as opposed to 8-10 years. The main advantage is that pure asphalt sealants are not carcinogenic.
Due to the significant cost of PAH-contaminated sediment disposal, the use of CTSs could have future financial impacts on the City. We are asking for your cooperation in using asphalt based sealcoat if you choose to sealcoat your driveway or parking lot. If you are hiring a professional, ask which type of sealant they use.