Coal-Tar Sealant Ban Found Effective

A ban on coal-tar-based pavement sealants in Austin, Texas, has curbed water pollution, concludes a study by U.S. Geological Survey researchers. Sealants, which are based either on coal tar or asphalt, are applied to pavement to make it last longer. Austin banned the coal-tar variety in 2006 after city and USGS scientists determined that parking lots treated with this type of sealant were a major source of polycyclic aromatic hydrocarbons (PAHs) tainting local waterways. Coal-tar-based sealants have much higher concentrations of PAHs, which are toxic to aquatic organisms, than do asphalt-based ones. The study found that average PAH concentrations in the sediment of a city lake dropped by 58% since the ban took effect (Environ. Sci. Technol. 2014, DOI: 10.1021/es405691q). The Pavement Coatings Technology Council, an industry group, says the study failed to take into account the 2007 closing of a natural-gas- and oil-fired power plant, which was a source of PAHs, adjacent to the lake.