Claim: Children at risk for ingestion of PAHs from pavement sealant

Is there a problem among children with black-topped driveways?

The Baylor University media release is below.

Click for the USGS media release.


Children at risk for ingestion of PAHs from pavement sealant, study finds

Children living near coal-tar-sealed pavement are likely to receive a far higher dose of carcinogenic polycyclic aromatic hydrocarbons (PAHs) from incidental ingestion of house dust than do children living near unsealed pavement, and that dose is more than two times higher than the PAH dose children are estimated to receive from food.

In a paper published in the journal Environmental Pollution, researchers at Baylor University in Waco, Texas, and the U.S. Geological Survey (USGS) in Austin, Texas, reported that the calculated non-dietary dose of B2 (carcinogenic) PAHs for children in residences adjacent to coal-tar-sealed pavement is 14 times that for children in residences adjacent to unsealed pavement.

Access the full study through this link:

The results are an important step in evaluating the human-health risk associated with use of coal-tar-sealcoat products.

“Our study indicates that house dust in residences adjacent to coal-tar-sealed pavement might represent a primary and biologically relevant exposure to B2 PAHs, especially in young children. This is of particular interest because of the widespread use of coal-tar-based sealant on parking lots and residential driveways in the U.S.,” said E. Spencer Williams., Ph.D., principal author of the study and Baylor University assistant research scientist at the Center for Reservoir and Aquatic Systems Research in the College of Arts & Sciences.

Coal-tar-based pavement sealant, a product applied to many parking lots, driveways, and even playgrounds primarily in the Central, Southern, and Eastern U.S., has PAH concentrations 100 to 1,000 times greater than most other PAH sources. An earlier study documented that house dust in residences adjacent to coal-tar-sealed parking lots had PAH concentrations 25 times higher than in house dust in residences adjacent to parking lots with other types of surfaces.

Humans regularly are exposed to PAHs through ingestion of cooked and uncooked foods, incidental ingestion of soil and dust, inhalation of ambient air and absorption through skin. While some previous studies have indicated that diet is the most important source of PAHs to humans, those studies did not consider house dust contaminated with PAHs from coal-tar-based sealcoat.

“Until now, common knowledge held that dietary ingestion was the most important way that children are exposed to PAHs, but these dose calculations challenge that assumption for some settings,” added Barbara Mahler, also an author of the exposure study and a researcher with the USGS.



  1. “…….might represent a primary and biologically relevant exposure to B2 PAHs, especially in young children. ” Yup. It “might” so bring on the precautionary principle. Of course that also means it might not….

  2. Yes, asphalt pavement is a definate hazzard to children! If they fall on it and skid along, it damages their skin.

  3. This study doesn’t come close to replicating what comes from blacktop pavements. It might have replicated ‘urban stream systems’, but the PAHs could have come from anything in the local watershed.

    What’s more, children are *not* ‘sediment-dwelling benthic macroinvertebrates’. Children are vertebrates, and even in the most unsanitary conditions, cannot be considered ‘sediment-dwelling’. So where do they get ‘children at risk for ingestion’?

    Let’s assume that ‘house dust in residences adjacent to coal-tar-sealed parking lots had PAH concentrations 25 times higher’. 25 times higher than what? And PAHs found in sealants are ‘100 to 1,000 times greater’ than in other stuff’? Not all streets are coated with sealant, and streets in residential areas don’t occupy most of the real estate.

    They haven’t even established a real correlation. The study assumes that children might get ‘ingestion of house dust’ from eating food. Imagine (gasp, choke) how this ‘likely’ might happen. If they *really* thought this was a problem, they’d administer blood tests and compare the results.

    What’s more, if this study involves real scientists, they’d know that just because you can detect something in one place doesn’t prove there’s a problem in another place. Where do they get the money to do this bogus crap?

  4. So they ground up some asphalt sealant, mixed it with dirt, put it in several streams

    What does water-leechable contaminant have to do with inhaled dust?
    How could they possibly justify 300 ppm limit? If the highest natural limit was 7.5, then a high value of 18 should be more than adequate.
    What is the expected exposure level? Twice that of food? The food exposure is diminishingly small. 2 x 0 = 0
    They deliberately polluted the Brazos river with known carcinogens. How is this not a violation of the Clean Water Act?

  5. It’s not Baylor’s fault.

    It’s not the sealant’s fault.

    It’s not the children’s fault.

    It’s the asphalt.

  6. The abstract given at the end of this post is for a different scientific paper published by researchers at the City of Austin, TX who looked at the effects of PAHs from coal tar-based sealants on benthic invertebrates (bottom-feeding critters in aquatic environments). When you click the link given in the article for the Williams et al. (2012) paper on “Coal-tar pavement sealants might substatially increase children’s PAH exposures”, the ScienceDirect web page pops up with other articles that may also be of interest to the reader. Whoever wrote this post copied the wrong abstract from a paper ScienceDirect thought would also be of interest to the reader into the end of this post. The abstract for Williams et al. (2012) paper is not currently available on the ScienceDirect web site.

  7. Carconogenic risk assement models were based on lifetime exposure (70 yrs). Occasional high level exposures from driveway sealer wouldn’t make any significant difference. Looks like another study playing the children exposure card to obtain funding. Beats working for a living.


  8. Mr. Milloy,

    This may interest you with regards to federal scientists from the U.S. Geological Survey (USGS) acting as environmental advocates. In 2008, there was an article published (peer reviewed) which provides justification by the USGS why they are somehow exempt from from basic tenets of the scientific method because they want to preserve their organization. In fact, all of the USGS studies have been authored or co-authored by the same two USGS scientists within that program that is mentioned in the article. I would be happy to provide you a copy of the article if you would like.

    Another example of advocacy by USGS is their refusal to provide industry with raw data from their studies. On one occasion, USGS actually questioned the industry group why they wanted this information. Mind you, none of this information falls into the exempt status of FOIA. This has been going on since 2006! As you can imagine, hypothesis testing is a little difficult if you do not have the details of the experiment. So much for Popper’s falsification and the scientific method!

    As a larger scale issue, USGS has been held up as a poster child of “scientific integrity” since they have a policy of scientific integrity where as most federal agencies do not even have a policy(EPA for example). When you closely look at the USGS integrity policy, it covers only the bare minimum of what one would expect of an integrity policy. In fact, if you compare the USGS policy versus that of an typical undergraduate college program, it is almost the same.

    The Obama administration has taken a step forward by requiring those federal organizations which perform science have an scientific integrity policy. However, these polices fall short of of what one would consider a policy of integrity. The actions of the USGS is a perfect example of science based upon minimum standards. Science based upon advocacy is biased and of little use to society. We need to demand better quality science from our federal employees.



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