The Texas Commission on Environmental Quality (TCEQ) has issued tougher air emissions regulations for producers, effective April 1, 2011, for Barnett Shale areas, according to this article in the Houston Chronicle. "TCEQ commissioners voted Wednesday to beef up air emission limits on toxic chemicals associated with natural gas drilling and required producers to do expanded testing of their drilling sites."
For a copy of the rules and related materials, see here (Rule Project No. 2010-018-106-PR).