The Texas Commission on Environmental Quality (TCEQ) released a study of air emissions in the Barnett Shale last Wednesday finding:
All chemicals monitored at the majority of monitoring sites were either not detected or were detected below levels of immediate health concern. At two monitoring sites in one geographic area, benzene was measured above the TCEQ short-term, health-based comparison value of 180 parts per billion (ppb) and the Toxicology Division (TD) recommends a reduction in volatile organic compounds (VOC) emissions in this area. While not an immediate health concern, benzene was measured at short-term levels that could cause concern about long-term cumulative exposure levels at an additional 19 monitoring sites in 11 geographic areas.
For a sample of the differing ways the study's results are being reported, see here (Houston Chronicle) and here (ABC News).