An air quality study conducted near Marcellus Shale natural gas operations in northeastern Pennsylvania during four separate weeks last year found no emission levels that would constitute a concern to the health of residents living nearby, the state's Department of Environmental Protection (DEP) said Monday.

"This study provides us with good information as part of our ongoing effort to gauge the impact these operations have on our air quality, public health and the environment," said DEP Director of the Bureau of Air Quality Joyce Epps. The sampling effort was not meant to address potential cumulative impacts, DEP said.

The sampling was conducted during the weeks of Aug. 9, Sept. 13, Oct. 14 and Oct. 25 at a completed and operating gas well (Cabot Oil & Gas Corp.'s Gesford 2V/7H) in Dimock Township; two compressor stations (Cabot's Lathrop and Teel stations) near Springville; and at a well site being fractured (Stone Energy's Loomis well site) near Lawton, all in Susquehanna County. The agency gathered samples to provide background data at Sones Pond in the Loyalsock State Forest in Sullivan County.

The study focused on concentrations of volatile organic compounds including benzene, toluene and xylene, which are typically found in petroleum products. DEP sampled for other pollutants, including carbon monoxide (CO) and nitrogen dioxide. The surveys detected the main constituents of natural gas, including methane, ethane, propane and butane, as well as low levels of associated compounds such as CO, the gasoline additive methyl tertiary butyl ether and the odor-producing compound methyl mercaptan. Fugitive and direct emissions were detected from well equipment at the Dimock Township well site.

"Overall, DEP's air sampling did not find concentrations of any compound that would likely trigger air-related health issues associated with Marcellus Shale drilling activities in the northeast region," DEP said.

DEP conducted similar air-monitoring studies near Marcellus gas facilities in north-central Pennsylvania. Those results are currently being evaluated.

A five-week air quality study last year found no air contaminant emission levels indicating problems for residents living near Marcellus operations in southwestern Pennsylvania's Greene and Washington counties (see Shale Daily, Nov. 3, 2010).

The air quality report is available at Click first on "Regional Resources," followed by the "Northeast Region" link and finally on the "Community Information" link.