A state study of air quality at Marcellus Shale wells in four northcentral Pennsylvania counties shows emissions from individual wells posed no public health concerns, but critics questioned its accuracy and noted it failed to look at the cumulative impact of the pollutants.
The Department of Environmental Protection study, based on air sampling done between August and December 2010 at gas well operations in Bradford, Lycoming, Sullivan and Tioga counties, found only low levels of volatile organic compounds -- including carcinogenic benzene, toluene and xylene -- and carbon monoxide and nitrogen dioxide.
"The results show there are no emission levels that would be of concern to the health of residents living and working near these operations," DEP Secretary Mike Krancer said in a news release issued Thursday.
To conduct the monitoring, the department's mobile laboratory trucks gathered air samples downwind from the Talisman Energy Thomas Compressor Station in Bradford County; East Energy's Shaw Compressor Station in Tioga County; East Energy's Chicken Hawk well; and Anadarko Petroleum's Hagemeyer well in Lycoming County.
According to the DEP, the monitors detected various components of natural gas -- methane, ethane, propane and butane -- plus low levels of other compounds, but none at levels high enough to be unhealthy for nearby residents or workers.
Mr. Krancer noted that the short-term air monitoring results were consistent with DEP's air monitoring findings around Marcellus wells in the southwestern and northeast regions announced in November 2010 and in January.
But Rachel Filippini, executive director of the Group Against Smog and Pollution, a Pittsburgh-based environmental group, said that consistency was due to the DEP's mobile air monitor, which isn't sensitive enough to detect certain pollutants, even when they are present at unhealthy levels.
"I haven't had a chance to look at the new study closely, but if the DEP is using the same methodology and monitoring equipment it did before, it doesn't surprise GASP that it's reached the same conclusions. That doesn't mean there isn't an air quality problem," she said.
When the first two air quality studies were released by the DEP, Joe Osborne, GASP's legal director, said the scope of the studies, which were limited like the latest one to a handful of samples, didn't support the department's broader conclusions or take into consideration the long-term exposure risks and cumulative impacts on airborne particle levels and ground-level ozone formation.
Air quality studies around shale gas drilling operations in other states and in Canada have found much higher emissions, including concentrations of hazardous pollutants such as benzene.
Don Hopey: email@example.com or 412-263-1983.