Evaluation of impact of shale gas operations in the Barnett Shale region on volatile organic compounds in air and potential human health risks

Abstract

Shale gas exploration and production (E&P) has experienced substantial growth across the U.S. over the last decade. The Barnett Shale, in north-central Texas, contains one of the largest, most active onshore gas fields in North America, stretching across 5000 square miles and having an estimated 15,870 producing wells as of 2011. Given that these operations may occur in relatively close proximity to populated/urban areas, concerns have been expressed about potential impacts on human health. In response to these concerns, the Texas Commission on Environmental Quality established an extensive air monitoring network in the region. This network provides a unique data set for evaluating the potential impact of shale gas E&P activities on human health. As such, the objective of this study was to evaluate community-wide exposures to volatile organic compounds (VOCs) in the Barnett Shale region. In this current study, more than 4.6 million data points (representing data from seven monitors at six locations, up to 105 VOCs/monitor, and periods of record dating back to 2000) were evaluated. Measured air concentrations were compared to federal and state health-based air comparison values (HBACVs) to assess potential acute and chronic health effects. None of the measured VOC concentrations exceeded applicable acute HBACVs. Only one chemical (1,2-dibromoethane) exceeded its applicable chronic HBACV, but it is not known to be associated with shale gas production activities. Annual average concentrations were also evaluated in deterministic and probabilistic risk assessments and all risks/hazards were below levels of concern. The analyses demonstrate that, for the extensive number of VOCs measured, shale gas production activities have not resulted in community-wide exposures to those VOCs at levels that would pose a health concern. With the high density of active wells in this region, these findings may be useful for understanding potential health risks in other shale play regions.

Influence of oil and gas emissions on ambient atmospheric non-methane hydrocarbons in residential areas of Northeastern Colorado

“…An air sampling study conducted at a private residence in the same region by Colborn et al (2014) identified numerous chemical species that have the potential to cause detrimental health effects, such as endocrine disruptors, and detected levels of poly-aromatic hyrocarbons (PAHs) high enough to lead to diminished mental development in children who suffered prenatal exposure. Conversely, Bunch et al (2014) reported that ambient levels of NMHC air toxics in the Barnett Shale (e.g., benzene, toluene) were not present at levels that would constitute a health concern based upon both acute and chronic exposure limits, as defined by the Texas Commission on Environmental Quality (TCEQ). It should be noted, however, that exposure limits are typically determined upon exposure to individual chemicals, and do not account for effects from interactions amongst multiple chemicals, nor do they include impacts on prenatal development, such as is the case with endocrine disruptors (Colborn et al, 2014).…”

Air Concentrations of Volatile Compounds Near Oil and Gas Production: A Community-Based Exploratory Study

“…Nevertheless, existing research gives support to resident reports of acute and long-term health symptoms and other reductions in quality of life. Even as they offer conflicting evidence of the relative importance of one stage of production or another to air emissions [10,11], or differ in their ultimate conclusion regarding the existence [10,11,14,35,36,39] or lack [21,40,41] of human health threats from air emissions, they find VOC concentrations in ambient air considerable distances from well pads, including in residential areas and public spaces.…”

“…They also explain why air quality studies carried out in UOG regions yield conflicting results. For example, McKenzie et al [11] found greater cumulative cancer risks and higher non-cancer hazard indices for residents living less than 0.5 miles from certain well pads in Colorado, while Bunch et al [21] analyzed data from monitors focused on regional atmospheric concentrations in the Barnett Shale region and found no exceedance of health-based comparison values. Colborn et al [10] gathered weekly, 24-hour samples 0.7 miles from a well pad in Garfield County, and noted a "great deal of variability across sampling dates in the numbers and concentrations of chemicals detected."…”

Updated methods for assessing the impacts of nearby gas drilling and production on neighborhood air quality and human health

“…In this case, vociferous complaints have been raised in rural towns such as Karnes City regarding the lack of regulatory protection for residents from bad air quality allegedly due to local oil and gas activities within a few miles of their homes (Song et al, 2014). Increasingly, citizens demand accurate information on oil and gas site emissions and their public health consequences, information that remains scarce despite recent scientific attention (Petron et al, 2012;McKenzie et al, 2012McKenzie et al, , 2104Adgate et al, 2014;Bunch et al, 2014). Commonly acknowledged sources of uncertainty are the lack of sustained monitoring of ambient concentrations of pollutants associated with gas mining, poor quantification of their emissions, and inability to correlate health symptoms with specific emission events.…”