Following a January report of a new "dust study" attempting to link refined coal tar-based sealer to possible cancer-causing compounds, the Pavement Coatings Technology Council (PCTC) has mounted a multi-pronged defense of the sealcoating material, which has been under attack since Austin, TX, banned refined coal tar- based sealer in 2006.
Anne LeHuray, PCTC executive director, says PCTC met at National Pavement Expo to formulate a response to the dust study findings as part of its continued efforts to help public agencies, contractors, and the public understand the refined coal tar-based pavement sealing material.
Among the first steps taken, because PCTC is not versed in dust studies, was hiring a specialist who will analyze the new Austin study and a related Canadian Settled Dust Study and report back to PCTC in March about the studies' process, results, and conclusions. In addition, a PCTC follow-up study that LeHuray says refutes the 2005 Austin study that resulted in a refined coal tar-based sealer ban is in the final stages of the scientific review process.
"If you believe some of the hyperbole that has appeared in the press about these studies, then refined coal tar-based materials are the most dangerous substances on earth," LeHuray says. "PCTC member companies and contractors have safely used this product for six decades and have no reason to think there are any adverse effects when used according to manufacturers recommended specifications."
Flawed Assumptions, Unjustified Leaps
LeHuray says the new attack, which attempts to link refined coal tar-based sealer to concentrations of polycyclic aromatic hydrocarbons (PAHs) in dust collected from ground floor apartments in Austin, suffers from many of the same flaws of the initial Austin Barton Creek study, which purported to study PAH sources in water runoff.
"The assumptions underlying many of the conclusions in this 'dust study' are suspect because they rely on the same flawed logic that formed the basis of the Austin Barton Creek study," LeHuray says. "The lack of evidence of damage to organisms in Austin's Barton Creek Pool and the U.S. Public Health Service finding that there is little risk to people who swim in the pool seem to have spurred the Austin opponents of sealant use to look for other ways to create human health concerns."
In the new study, house dust from 23 ground floor apartments - 11 near parking lots sealed with refined coal tar-based sealant and 12 near parking lots either unsealed or coated with other substances - was collected and analyzed. According to the results the study found that dust in apartments next to parking lots sealed with refined coal tar-based sealant had PAH levels an average of 25 times higher than other locations. The study draws the conclusion that refined coal tar-based sealers are the source of the PAHs.
But the PCTC says that's not the wording in the study's own report. In a preliminary response to the dust study PCTC says, "The underlying premise of the dust study is the same as what it was in the first study in Austin back in 2005. What they concluded is that refined coal tar-based sealant is likely a significant source of PAHs. But if you follow the studies the initial report says 'could be' which was changed in subsequent publications from 'could be' to 'are', and that's a big difference. It's just a language change, but the change in language replaces speculation with certainty without any substantiation."
Other dust study questions include:
- The lack of "fingerprinting" of the PAH sources which results in more reliance that conclusions reached in the earlier suspect Austin studies are valid,
- The failure to normalize PAH levels to total dust collected, and
- A reliance on concentrations despite the fact EPA has indicated that using the "concentration (weight per weight) of a contaminant in settled dust is a poor indicator of risk."