A recent scientific journal came out with little attention or really no media coverage at all. While there may be a variety of reasons why, my hunch is that part of the reason is that it contains some pretty complex and difficult concepts to communicate. Well I thought I would try to decipher a bit of that for you here.

The first task at making this a little more lay-friendly was to redo the above graph using data from the report. The essence of the paper is really contained in this graph. If you take your time to understand it, these are the key points:
  1. There is some cancer risk from ingestion from background PAH (polycyclic aromatic hydrocarbons) sources that we get from food and the environment, but it is in a risk range that the EPA would review on a case-by-case basis. This is why we frequently hear public service announcements to minimize eating grilled meat and exposure to tobacco smoke (incidental 2nd hand if you will).
  2. Any exposure scenario to from the proximity to coal tar sealed asphalt puts the risk into the zone of "desired remediation" or as stated previously "federally unacceptable."
  3. Most exposure comes from coal tar sealant contaminated soil instead of indoor dust.
  4. Early childhood exposure is most troubling, but so is also in the red zone is a lifetime of exposure or even just exposure during adulthood.

The article, entitled "Cancer Risk from Incidental Ingestion Exposure to PAHs Associated with Coal Tar Sealed Pavements," is a further refinement of work led by Dr. Spencer Williams, a toxicologist from Baylor University and co-authored by Drs. Barbara Mahler and Peter Van Metre of the USGS.

His work has been covered on Coal Tar Free America with the following posts:


This is far from the last word that we will hear on the health effects of coal tar sealants. This paper covered just one exposure mechanism: ingestion. Also possible routes are inhalation and dermal. Also we have learned over the years that PAH's cause many maladies, not just cancer, including birth defects, fertility, and IQ.

Do you now know enough to stop this practice in your sphere of influence, whether it is your driveway, business, church, school district, community or state?

A video of Dr. Williams presenting these findings is found here:

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