The Data Gap: Can a Lack of Monitors Obscure Loss of Clean Air Act Benefits in Fracking Areas?

The U.S. is shifting to a greater reliance on natural gas to meet its energy needs, and a large part of this demand is being met by the development of shale gas formations. The increased utilization of natural gas is driven by the supply and thus lower cost, which largely results from new advances in engineering techniques. Primarily, gas production from horizontal drilling and high-volume hydraulic fracturing of shale and other low-porosity rock drives the favorable economics. Discussion of the environmental impacts of these operations has largely focused on water quality issues, but air pollution is also an important potential impact due to emissions associated with drilling, extraction, and associated transportation activities. Recently, air quality impacts have been measured in active oil and gas well areas. The extent to which these increased emissions impact air quality, especially in highly developed shale gas regions where there are no air monitors represents a substantial data gap and hinders effective air quality management. Throughout the United States, ambient concentrations of criteria pollutants have been decreasing in response to the implementation of the Clean Air Act. For example, Russell et al. (2012) find the rate of decrease in ambient NO2 concentrations in the mid 2000s to be, on average, about 4.5% yr−1 for U.S. cities. Using data from the Environmental Protection Agency’s Technology Transfer Network (TTN) (http://www.epa.gov/ ttn/airs/airsaqs/detaildata/downloadaqsdata.htm; data downloaded on September 23, 2013 and processed with R statistical software), we find overall similar decreasing trends in New York, Ohio, Pennsylvania, and West Virginia for SO2, CO, NO2, NOx, and PM2.5. This improvement in air quality through reduction in ambient concentrations of a variety of criteria air pollutants represents a tremendous success of the Clean Air Act. However, there can be local differences. An example is the Marcellus Shale Region of Western Pennsylvania where the amount of gas development activities has recently exploded (e.g., >6000 active wells in Pennsylvania alone). Ambient NOx (NO+NO2) concentrations generally were decreasing since the mid 2000s in most Eastern U.S. locations. However, in some areas a clear decrease is not evident and at a few locations the pollutant concentrations have been increasing in recent years. TTN air quality data indicates that at a monitor in Beaver County in western Pennsylvania, near several active wells in the Marcellus Shale region, monthly mean ambient NOx concentrations have been steadily increasing since 2010. In fact, some recent wintertime monthly average NOx concentrations have reached levels not observed since the implementation of the “Clean Air Interstate Rule” (CAIR) in 2009 (Figure 1). We find a similar trend in Steuben County, New York in a forested area downwind of shale gas activities in PA, where ambient NO2 concentrations have been increasing since 2008. The increase in pollutant concentrations and potential onset of losses in Clean Air Act benefits started in the latter part of the 2000s, coincident with the onset of shale gas activities in the surrounding areas. In addition to these findings, we observe that the individual counties with the highest number of active wells by State in the Marcellus Shale region, that is, Carroll, OH; Marshall, WV, and Bradford, PA have no routine air quality monitors. As a consequence, current trends in criteria air pollutants such as NO2, SO2, CO, Pb, PM2.5 cannot be effectively evaluated with observational data in those locations. This represents a data gap that may be obscuring negative air quality effects from shale gas activities. NOx emissions from electric generating units (EGUs) in Pennsylvania have been decreasing and are unlikely to explain the increases in ambient NOx concentrations measured at these sites. Continuous emissions monitoring (CEM) data from EPA clean air markets division (www.epa.gov/airmarket downloaded November 9, 2013) indicates that statewide NOx emissions from EGUs in Pennsylvania peaked in 2008. The CEM data suggest year-to-year variability in NOx emissions exists, possibly as a combination of meteorology and NOx credit trading price,