javascript:; Industry Denial of Toxic House Dust is Off-Track | Coal Tar Free America

A few weeks ago we introduced a series of posts to look at the pavement sealcoat industry's latest PR piece to get people to continue to use their coal tar  product. Now we'll investigate their claim that there really isn't any truth to the studies about contaminated dust from these sealers getting into homes and being a cancer risk to people.

Third Issue is this: I heard about it becoming hazardous to dust in houses. 

Just for clarification coal tar is not hazardous to dust. It is hazardous to people.

Let's summarize the study that is referred to. A toxicologist from Baylor University joined a team of USGS scientists to perform a risk assessment for people living in first floor apartments in Austin where elevated levels of chemicals, polycyclic aromatic hydrocarbons (PAHs) were found. Key findings were (quoting from the USGS website):
  • Residences adjacent to parking lots with coal-tar-based sealcoat have concentrations of PAHs in house dust 25 times higher than residences adjacent to unsealed pavement or asphalt-sealed pavement. 
  • Doses of carcinogenic PAHs through non-dietary ingestion of house dust in residences with coal-tar sealant on the parking lot are 14 times greater than in residences with unsealed pavement, and are more than twice the dose from dietary ingestion, reversing a long-held assumption that dietary PAH exposure exceeds non-dietary exposure. 
  • Living adjacent to coal-tar-sealed pavement (a parking lot or driveway, for example) is estimated to increase excess lifetime cancer risk 38 times, and much of the increased risk occurs during early childhood.
Keep in mind that this research did not include the exposure to a child playing on a coal tar sealed surface. The risks would be so much greater, which led Dr. Spencer Williams to comment:

"I definitely don't think it is a stretch to say that with the concentrations that you see in the dust on coal tar sealed pavement, you would get a significant exposure with even one hand to mouth motion." Source.

As to the quality of the USGS research, a point-by-point examination of these claims was performed when they came out. We found their criticisms baseless. The EPA recently agreed.

Claim: "PAHs are Everywhere"

This obvious statement implies that someone has stated something to the contrary. No one who supports the science of coal tar sealer pollution has EVER stated anything different. Most presentations on this topic include relative concentrations of many common materials as the one shown here. The point isn't whether they are or aren't everywhere. The point is that coal tar sealers are a PAH source with an "exceptionally high" concentration.

Claim: "The WHO (World Health Organization) says most PAHs comes from food"

Sure they said this when speaking about the entirety of the human race, most of whom don't have cars, driveways or coal tar sealers. And the statement is from 1998, before the discovery of coal tar sealer pollution in 2003.

When you compare dietary ingestion with exposure to coal tar sealer dust in soil and in homes, coal tar sealer is shown to be the dominant source, far surpassing food intake.

Inferred Claim: "If you can buy coal tar shampoo, then coal tar sealers and its dust must be OK"

Industry representatives encourage contractors to carry around a bottle of coal tar shampoo with them to convince the public that it is OK to put on their driveway. We devoted an entire article to this in a post entitled, "Apples, Oranges and Coal Tar Shampoo."

Here are the main points:
  • Comparing coal tar sealers to coal tar shampoo isn't exactly a ringing endorsement to its safety. Coal tar shampoos have been outlawed in many parts of the world.
  • People who use coal tar shampoos apply them in a controlled manner, presumably understanding the risks. People exposed to coal tar sealers don't get that choice, either when it is on a commercial parking lot, school playground or when not informed of the risks on their own driveways.
  • After coal tar use in shampoos, the residue is washed down the drain for some additional treatment prior to exposure in the environment. On the other hand, when coal tar sealers are applied to asphalt, it leaves in an uncontrolled manner to the air, soil, water and people at high concentrations.
Yes this industry-led, dust-denial is off-track just like other claims we have examined. The head-scratcher here is why anyone would defend this use.

Post a Comment