Robert L. Tanguay, Ph.D.
Oregon State University
A study supported in part by NIEHS showed that certain pavement sealcoats used on asphalt driveways and parking lots are significantly more toxic and mutagenic than previously suspected.
The researchers determined the concentrations of 23 polycyclic aromatic hydrocarbons (PAHs) that are classified as unsubstituted PAHs, as well as 56 PAH derivatives and 11 high molecular weight PAHs in coal tar-based and asphalt-based sealcoat products. The high molecular weight PAHs had not been included in previous studies of sealcoat products.
Including the high molecular weight PAH compounds increased the calculated benzo[a]pyrene carcinogenic equivalent by 4.1 to 38.7 percent, suggesting a greater potential risk to human health from coal tar-sealed surfaces than had been previously determined. The asphalt-based sealcoats, which are more commonly used in the western U.S., were toxic, but showed far less toxicity than coal tar sealcoats, which use byproducts of the coal coking process and are more commonly found in the Midwest and East. Further analysis indicated that the asphalt-based products were not mutagenic, but the coal tar-based ones were.
The study results were consistent with previous findings from the U.S. Geological Survey. However, in the new study, the researchers studied a greater number of PAH compounds and found even higher levels of toxicity in sealcoats based on coal tar than had previously been suspected.
Citation: Ivan A. Titaley, Anna Chlebowski, Lisa Truong, Robert L. Tanguay, Staci L. Massey Simonich. Identification and toxicological evaluation of unsubstituted PAHs and novel PAH derivatives in pavement sealcoat products. Environmental Science & Technology Letters; doi:10.1021/acs.estlett.6b00116 [Online 25 April 2016].