New Studies Defend Use of Refined Tar-Based Sealers

This article reports on studies sponsored by the Pavement Coatings Technology Council (PCTC) that have concluded that refined tar-based sealants are not the main source of polycyclic aromatic hydrocarbons (PAH's) in the environment. The findings from the PCTC studies refute the findings of 2005 studies conducted in Austin, Texas, which showed that refined tar-based sealant contain PAHs and that soil or sediment samples taken next to a sealed parking lot sometimes contain high levels of PAHs. This proposed link between the PAHs in refined tar-based sealant and PAHs in rivers, streams, and lakes has resulted in regulatory challenges and bans of sealers in some locations. The city of Austin banned the use of refined tar-based sealant as of January 1, 2006. The PCTC study examined sediment samples collected from Austin's streams before the ban in October 2005, and again after the ban in April 2008. Findings showed that total concentrations of PAHs in sediments before and after the ban did not change. If sealers were the principal source of PAHs in sediments, then PAH concentrations should have declined once the ban was in place. PAHs in the Austin samples were also evaluated using environmental forensics techniques. PAH fingerprinting of sediments collected before and after the ban did not identify any marked changes. When all the data available in Austin is considered, it appears that refined tar-based sealant is not a major source of PAH in sediments downstream of the immediate area of a sealcoated lot. Although PAHs are found in sealers, they can also be found in used motor oil, grilled meats and vegetables, exhaust from internal combustion engines, products made from coal and petroleum, and emissions from fossil fuel power plants and forest fires.