ShaleTest, a private effort that has been critical of natural gas operations, says two recent air tests showed "elevated" levels of benzene. The Texas Commission on Environmental Quality, which conducted one of the tests, said the short-term measurements aren't necessarily a concern unless they prove to be long-term. The Star-Telegram has a report here.
Benzene, a human carcinogen, is fairly widely used -- it's a component of gasoline, for example -- and has varying levels of risk tied to different concentrations. Hence, it's one of the components of oil and gas operations that TCEQ tracks as part of its air monitoring in the Barnett shale. The concentrations found at a compressor station near downtown Fort Worth and a compressor station west of the Denton County community of Dish exceeded TCEQ's threshold for long-term exposure, but that is based on continuous exposure throughout a lifetime. Additional sources of information on the health effects of benzene can be found at the Centers for Disease Control and Prevention (CDC), here, and at the federal Agency for Toxic Substances and Disease Registry, here.
-- Jim Fuquay