Want to seal your driveway? Don’t use coal-tar based sealant!

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Beautiful but deadly? Credit: USGS

Many people like to use driveway sealants to prolong the life of their asphalt driveways and to give them an attractive, shiny glow.  However, in recent years there have been a number of scientific studies that indicate using coal tar sealants have significant environmental and health effects.  Coal tar sealants contain very high levels of polycyclic aromatic hydrocarbons (PAHs), many of which are suspected or known carcinogens.

  • Coal tar pitch from sealcoat reaches streams and lakes via runoff as the sealcoat erodes. Coal tar sealcoat was determined in a study to be the largest source of PAH contamination to urban lakes.
  • PAHs are toxic to mammals, birds, fish, amphibians, invertebrates and plants. Invertebrates that live in the bottom sediment where PAHs accumulate are particularly susceptible to PAH contamination. Possible effects include reduced reproduction, forcing creatures from their habitat, and death.
  • The routine wear and tear of coal tar sealcoated pavements produces dust and particles contaminated with PAHs that can be breathed and accidentally ingested by people living by the pavements.  For someone who spends their entire lifetime living adjacent to coal tar sealcoated pavement, the average excess lifetime cancer risk is estimated to be 38 times higher than the urban background exposure. More than one-half of the risk occurs during the first 18 years of life.
  • Much of the scientific argument against coal tar comes from the USGS, and you can learn more here: Studies and information from the United States Geological Survey.

There is a safer alternative if sealants are needed.  Asphalt based sealcoats are safer, readily available, and very affordable according to the Minnesota Pollution Control Agency website.  (The state of Minnesota has banned coal tar sealcoats and provides information on alternatives.)  The most common and least expensive alternative to coal tar sealcoat now on the market is petroleum asphalt based sealcoat.  Asphalt sealcoats contain PAHs, but at far lower levels than coal tar sealcoats—about 1/1000th the PAH level of coal tar sealcoats.

HRWC is currently investigating how wide-spread the use of coal tar sealants is in our communities.  We are not sure if this is a minor problem here, or a serious issue. We will release more information as more is learned over the coming month. However, one thing seems undeniable- you do not want this material used at your house, at your neighbors’ houses, or on parking lots that you and your children walk on.

This June 20, 2013 USA Today article gives some pertinent advice. “Before sealing your driveway, hire only a contractor who provides a MSDS (material data safety sheet) for the intended product. Check to see if it contains this CAS number for coal tar: 65996-93-2. If doing the work yourself, buy only products with a “coal tar free” logo.”



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