"More than 450 natural gas compressor stations and processing plants have been built in Pennsylvania since 2008, when Marcellus Shale gas development kicked into another, higher gear."

"Collectively, the rapidly multiplying facilities emit tens of thousands of tons of pollutants a year. And the growing emissions load may eventually lead to poorer air quality, according to environmental organizations.

Despite that emissions load, none of those Marcellus gas facilities are grouped together for permitting purposes by the state and labeled a "major source" of pollution -- a Clean Air Act designation that could require more extensive, and expensive, emission controls."

Don Hopey reports for the Pittsburgh Post-Gazette October 6, 2013. [2]