The Future of Fracking: New Rules Target Air Emissions for Cleaner Natural Gas Production

Emissions of volatile organic compounds (VOCs) and hazardous air pollutants (HAPs) from oil and natural gas production were investigated using direct measurements of component-level emissions on pads in the Denver-Julesburg (DJ) Basin and remote measurements of production pad-level emissions in the Barnett, DJ, and Pinedale basins. Results from the 2011 DJ on-site study indicate that emissions from condensate storage tanks are highly variable and can be an important source of VOCs and HAPs, even when control measures are present. Comparison of the measured condensate tank emissions with potentially emitted concentrations modeled using E&P TANKS (American Petroleum Institute [API] Publication 4697) suggested that some of the tanks were likely effectively controlled (emissions less than 95% of potential), whereas others were not. Results also indicate that the use of a commercial high-volume sampler (HVS) without corresponding canister measurements may result in severe underestimates of emissions from condensate tanks. Instantaneous VOC and HAP emissions measured on-site on controlled systems in the DJ Basin were significantly higher than VOC and HAP emission results from the study conducted by Eastern Research Group (ERG) for the City of Fort Worth (2011) using the same method in the Barnett on pads with low or no condensate production. The measured VOC emissions were either lower or not significantly different from the results of studies of uncontrolled emissions from condensate tanks measured by routing all emissions through a single port monitored by a flow measurement device for 24 hr. VOC and HAP concentrations measured remotely using the U.S. Environmental Protection Agency (EPA) Other Test Method (OTM) 33A in the DJ Basin were not significantly different from the on-site measurements, although significant differences between basins were observed.Implications: VOC and HAP emissions from upstream production operations are important due to their potential impact on regional ozone levels and proximate populations. This study provides information on the sources and variability of VOC and HAP emissions from production pads as well as a comparison between different measurement techniques and laboratory analysis protocols. On-site and remote measurements of VOC and HAP emissions from oil and gas production pads indicate that measurable emissions can occur despite the presence of control measures, often as a result of leaking thief hatch seals on condensate tanks. Furthermore, results from the remote measurement method OTM 33A indicate that it can be used effectively as an inspection technique for identifying oil and gas well pads with large fugitive emissions.

Abstract. Emissions of volatile organic compounds (VOCs) associated with oil and natural gas production in the Uintah Basin, Utah were measured at a ground site in Horse Pool and from a NOAA mobile laboratory with PTR-MS instruments. The VOC compositions in the vicinity of individual gas and oil wells and other point sources such as evaporation ponds, compressor stations and injection wells are compared to the measurements at Horse Pool. High mixing ratios of aromatics, alkanes, cycloalkanes and methanol were observed for extended periods of time and for short-term spikes caused by local point sources. The mixing ratios during the time the mobile laboratory spent on the well pads were averaged. High mixing ratios were found close to all point sources, but gas well pads with collection and dehydration on the well pad were clearly associated with higher mixing ratios than other wells. The comparison of the VOC composition of the emissions from the oil and natural gas well pads showed that gas well pads without dehydration on the well pad compared well with the majority of the data at Horse Pool, and that oil well pads compared well with the rest of the ground site data. Oil well pads on average emit heavier compounds than gas well pads. The mobile laboratory measurements confirm the results from an emissions inventory: the main VOC source categories from individual point sources are dehydrators, oil and condensate tank flashing and pneumatic devices and pumps. Raw natural gas is emitted from the pneumatic devices and pumps and heavier VOC mixes from the tank flashings.

More than 15 million Americans are now estimated to live within one mile of a natural gas well drilled since 2000.1 Research has demonstrated that natural gas development results in the emission of pollutants that include suspected developmental toxicants, such as benzene, toluene, and xylenes,2 although few studies have investigated the public health impact of these emissions. In this issue of EHP, researchers report preliminary evidence of an association between two birth defects and a mother’s residential proximity to natural gas wells at the time of birth.3 “Studies like this underscore the need for more representative and comprehensive research on workers and communities to understand their exposures and potential health risks,” says Aubrey Miller, a senior medical advisor at the National Institute of Environmental Health Sciences. Researchers led by Lisa McKenzie at the Colorado School of Public Health estimated exposure to natural gas development for nearly 125,000 Colorado women. They used an “inverse distance weighting” method in which they determined the density of natural gas wells within a 10-mile radius of each mother’s home at the time she gave birth, with greater weighting for wells nearer the home. Then they compared proximity to gas wells between mothers who had adverse birth outcomes—including three types of birth defects, preterm birth, and term low birth weight—and those who did not. Future studies should assess exposure to benzene (inset) among people living near gas wells. Among 59 cases of neural tube defects, prevalence was twice as high among babies of mothers in the highest exposure group—a group of 19 women with more than 125 wells per mile within a 10-mile radius of the home—compared with babies of unexposed mothers. However, there was no evidence that neural tube defects were increased among the 13 babies of mothers classified as having low or medium exposure. Among 1,823 cases of congenital heart defects, prevalence was 30% higher among babies of mothers in the highest exposure group, compared with babies born to unexposed mothers. In contrast to neural tube defects, however, the likelihood of a congenital heart defect increased steadily with increasing exposure. Congenital heart defects are the most common type of birth defect, affecting about 8 of every 1,000 newborns in the United States.4 There was no association observed between proximity to natural gas development and having babies with an oral cleft. In addition, babies whose mothers experienced the highest exposures to natural gas wells were slightly less likely to be born prematurely or at a low birth weight. However, the association between proximity to gas wells and improving birth weights diminished when the researchers accounted for elevation. “Higher elevations are associated with lower birth weights, while most natural gas drilling in Colorado occurs at low elevations,” McKenzie explains. Although low levels of maternal folic acid—a B vitamin found in green leafy vegetables—is an established risk factor for neural tube defects,5 little is known about other environmental factors that may contribute to these birth defects. Two previous studies suggested that maternal exposure to benzene could increase congenital heart defects and neural tube defects.6,7 Another study reported associations between several birth defects in California and increased ambient concentrations of carbon monoxide and ozone.8 “The study certainly raises legitimate concerns, given that there are plausible mechanisms for many of the chemicals that are used in natural gas development,” says Kenneth Spaeth, medical director of the Occupational and Environmental Medicine Center at North Shore University Hospital inNew York, who was not involved in the study. The authors suggest that exposure to benzene from the wells is one such plausible explanation for their findings. However, they did not identify or measure specific pollutants that may have been present at natural gas wells or specific activities occurring at the sites, so it is not possible to know which chemicals and/or other environmental stressors—if any—explain the associations. It’s also possible that some other risk factor not associated with wells, such as mothers’ folic acid consumption or level of prenatal care, could have influenced the results. “Our findings are far from representing a causal effect,” says McKenzie. Her plans for future research include interviews with study mothers to get more information about their pregnancy and place of residence during the first trimester, a critical period for birth defect formation. She also plans to obtain more detailed information on specific activities taking place at well sites during the first trimester.

As part of an effort to assess the potential impacts associated with global climate change, the U.S. Environmental Protection Agency's Office of Research and Development is supporting global atmospheric chemistry research by developing global scale estimates of volatile organic compound (VOC) emissions (excluding methane). Atmospheric chemistry models require, as one input, an emissions inventory of VOCs. Consequently, a global inventory of anthropogenic VOC emissions has been developed. The inventory includes VOC estimates for seven classes of VOCs: paraffins, olefins, aromatics (benzene, toluene, xylene), formaldehyde, other aldehydes, other aromatics, and marginally reactive compounds. These classes represent general classes of VOC compounds which possess different chemical reactivities in the atmosphere. The technical approach used to develop this inventory involved four major steps. The first step was to identify the major anthropogenic sources of VOC emissions in the United States and to group these sources into 28 general source groups. Source groups were developed to represent general categories such as “sources associated with oil and natural gas production” and more specific categories such as savanna buming. Emission factors for these source groups were then developed using different techniques and data bases. For example, emission factors for oil and natural gas production were estimated by dividing the United States' emissions from oil and gas production operations by the amount of oil and natural gas produced in the United States. Multiplication of these emission factors by production/consumption statistics for other countries yielded global VOC emission estimates for specific source groups within those countries. The final step in development of the VOC inventory was to distribute emissions into 10° by 10° grid cells using detailed maps of population and industrial activity. The results of this study show total global anthropogenic VOC emissions of about 110,000 Gg/yr. This estimate is about 10% lower than global VOC inventories developed by other researchers. The study identifies the United States as the largest emitter (21% of the total global VOC), followed by the (former) USSR, China, India, and Japan. Globally, fuel wood combustion and savanna burning were among the largest VOC emission sources, accounting for over 35% of the total global VOC emissions. The production and use of gasoline, refuse disposal activities, and organic chemical and rubber manufacturing were also found to be significant sources of VOC emissions.

WPX Energy owns and operates state of the art water treatment facilities in the Piceance Basin, located in Western Colorado. Recycling and reusing water is key to the company's success in unconventional tight gas development. Natural gas drilling and production in the Piceance Basin is a long-term play expected to continue for another 20 years or more. Given this extended time horizon, WPX implemented permanent and centralized water management infrastructure to control costs and improve profitability. The role of the Centralized Water Management Facility (CWMF) is to treat water produced from natural gas wells, recover oil and condensate, operate within federal, state and county regulations, and consistently provide high quality treated water for hydraulic fracturing operations and disposal. The CWMF generates a revenue stream by capturing the oil and condensate that remains in the water after wellhead separation. Produced water is unique and specific to the oil and gas reservoir from which it came, therefore, a complete characterization of the produced water to be treated is essential. What works in one basin may not work in others, effective facility design and treatment processes must be customized on an individual level and automated to ensure proper process control and safety. The state regulates volatile organic compound (VOC) emissions for ponds used to store treated water. The challenge is developing a process that removes dissolved and suspended hydrocarbons for compliance with state VOC emission limits for treated water stored in ponds. Processes within the CWMF generate waste streams such as sludge and separated chemicals from production operations. The CWMF must be able to process, clean and recycle these waste streams. WPX centralized water management facilities have a proven track record of supporting production operations needs and consistently providing clean water for hydraulic fracturing operations. These water management strategies have lowered operating costs allowing the Piceance Basin to lead the way in company profitability during times of low gas prices. An outstanding environmental and safety track record has fostered strong community relations and led to awards of recognition from government agencies including the BLM and COGCC (Colorado Oil and Gas Conservation Commission). Natural gas development in the Piceance Basin began to increase in the mid 1990s. Operators moving into the basin were focused on drilling to hold leases and defining the boundaries of the producing zones. Most water movements during the ramp-up were accomplished by water haulers operating in the challenging mountainous and hilly terrain. The daily water volumes from producing wells grew in lock step with the rising natural gas production. Strong demand for trucking services drove higher trucking costs. By 2005 the boundaries of the natural gas producing zones were well established and operators started to transition into an optimization phase by drilling and completing multi-well pads to reduce costs and maximize production. In 2005, water hauling costs made up 25% of the total cost for completing a well in unconventional tight gas development and water haul cost up to $3.50/bbl for moving water around the field were common. Clearly, water moving strategies needed to be challenged. Controlling these costs is a key factor contributing to lease holder and mineral owner profitability and can often be the driving factor determining whether an asset development remains viable, especially in times of low gas prices. Properly designed, implemented and operated water management facilities (WMFs) provide the means for controlling these costs. WMFs also allow for predictable operations and provide a consistent high quality water product, on demand for hydraulic fracturing. Three types of water management facilities will be discussed in this paper, and can be either permanent or temporary. Centralized pumping stations for water transfer Pipelines Centralized water treatment facilities Once it is determined that a facility is needed, the decision to build a permanent or temporary facility is primarily driven by economics. The operator needs to complete an economic analysis comparing the total cost of building a permanent facility versus using contract services and rented equipment to accommodate the business need. As a simple example of economic analysis, let's evaluate the need for a permanent or temporary water transfer facility. In this example, water from producing wells is gathered at a central tank facility. From the central tank facility, water can be pumped, via pipeline, for reuse in a nearby hydraulic fracture operation or pumped to a larger water storage pit. The operator could use contract water pumping services and rented equipment or they could design and build a permanent water transfer facility including automation and plan to operate the new facility with company personnel. Table 1 details a simple cost breakdown used for the economic analysis. Note: Economic analysis examples presented in this paper have been simplified and are intended to illistrate a point. Examples to do not include full project or operations detail and tax considerations are not included. Each new project is unique, costs and service rates will vary from basin to basin. Operators need to determine economic justification on a projet by project basis. Table 1 Economic analysis comparing costs of renting/contracting services and building a permanent water transfer facility In this example, the cost of the permanent facility is paid out in less than 94 days and the cost for running the facility goes from $3,870/day using contract services and rented equipment to $1,760/day using company personnel. It makes sense to build a permanent facility if it is expected to be used for more than 94 days. This is, of course, a simplified example. Each new project will be unique and require using different project cost variables for comparison, but a similar economic analysis approach would be used for larger more complex facilities. For permanent water facilities projects in the Piceance Basin, the average payout is one to two years, and it makes sense to build a permanent facility if the facility is expected to be used beyond that time frame.

Large CH4 leak rates have been observed in the Uintah Basin of eastern Utah, an area with over 10,000 active and producing natural gas and oil wells. In this paper, we model CH4 concentrations at four sites in the Uintah Basin and compare the simulated results to in situ observations at these sites during two spring time periods in 2015 and 2016. These sites include a baseline location (Fruitland), two sites near oil wells (Roosevelt and Castlepeak), and a site near natural gas wells (Horsepool). To interpret these measurements and relate observed CH4 variations to emissions, we carried out atmospheric simulations using the Stochastic Time‐Inverted Lagrangian Transport model driven by meteorological fields simulated by the Weather Research and Forecasting and High Resolution Rapid Refresh models. These simulations were combined with two different emission inventories: (1) aircraft‐derived basin‐wide emissions allocated spatially using oil and gas well locations, from the National Oceanic and Atmospheric Administration (NOAA), and (2) a bottom‐up inventory for the entire U.S., from the Environmental Protection Agency (EPA). At both Horsepool and Castlepeak, the diurnal cycle of modeled CH4 concentrations was captured using NOAA emission estimates but was underestimated using the EPA inventory. These findings corroborate emission estimates from the NOAA inventory, based on daytime mass balance estimates, and provide additional support for a suggested leak rate from the Uintah Basin that is higher than most other regions with natural gas and oil development.

Knowlton et al. (2004) argued that increasing temperatures associated with climate change will increase urban ozone and related health risks. They have disregarded important factors in reaching this conclusion. During the last 20 years, nationwide exceedances of the federal 1-hr ozone standard declined 90%, and the June–August average of daily 1-hr peak ozone levels declined 10% (Schwartz et al., in press), presumably with ensuing declines in ozone-related mortality. Ozone declined despite a roughly 1°C increase in urban temperatures during the last few decades (Karl et al. 1988). Knowlton et al. (2004) did not explain why we should expect the future to be the opposite of the past. Knowlton et al. (2004) used ozone-precursor [nitrogen oxides (NOx) and volatile organic compound (VOC)] emissions estimates for 1996 to predict ozone levels in the 2050s. However, even current emissions are substantially lower than 1996 levels, while, as shown below, already-adopted U.S. Environmental Protection Agency (EPA) requirements will eliminate most remaining ozone-precursor emissions, even after accounting for growth. The U.S. EPA (2003) estimated that between 1996 and 2001, total emissions of NOx and VOC declined, 10 and 14%, respectively. [The U.S. EPA updated its trend estimates in November 2004 (U.S. EPA 2004a) and now believes the decline was even steeper, although these new estimates were obviously not available to Knowlton et al.] During 2003 and 2004, the U.S. EPA capped total NOx from coal-fired power plants and industrial boilers at 60% below 2000 levels (U.S. EPA 1998a, 2004b). A range of emissions data show the average automobile’s NOx emissions rate declined 4–9% per year between 1995 and 2001, with greater improvements for vehicles up to 4 years old (Pokharel et al. 2003; Schwartz 2003). Total driving is increasing < 2% per year, resulting in large net NOx declines (Texas Transportation Institute 2004). Data on heavy-duty diesel vehicles are sparse, but there is every reason to believe that diesel NOx has also declined. The U.S. EPA has tightened NOx standards for new on- and off-road diesels several times over the last 15 years, and also recently required additional NOx reductions from in-use 1993–1998 model year trucks (U.S. EPA 2002a, 2004c, 2004d). VOCs have declined far more than NOx and far more than U.S. EPA estimates. The U.S. EPA’s official VOC inventory understates significantly the gasoline-vehicle contribution to total VOCs (Watson et al. 2001). Real-world data show the average automobile’s VOC emission rate is declining 11–15% per year, again much more rapidly than driving is increasing, and with a more rapid decline for recent models (Pokharel et al. 2003; Schwartz 2003). The U.S. EPA also recently implemented VOC reductions for other sources (U.S. EPA 1998b, 2002b, 2004e). Overall, between 1996 and 2004, anthropogenic NOx and VOC emissions likely declined, respectively, at least 25 and 50%—declines overlooked by Knowlton et al. (2004). Emission declines will continue. For example, a vehicle fleet meeting the U.S. EPA’s “Tier 2” automobile standards, implemented in 2004, on-road diesel standards set for 2007, and off-road diesel standards set for 2010, will emit 90% less NOx and VOCs per mile over their lifetime than the current average vehicle, resulting in huge emissions declines, even with predicted increases in driving (Schwartz 2003; U.S. EPA 2000a, 2000b, 2004c). Knowlton et al. (2004) assume ozone-precursor emissions several times greater than any plausible future scenario. Their projections of future ozone and related health impacts are therefore unrealistically high. Heat-related mortality has also declined, by 70% nationwide since the 1960s, despite warming urban climates, with the hottest and most humid cities achieving the greatest risk reductions (Davis et al. 2003). These health improvements resulted from a range of adaptive technologies and processes, including increased air conditioning, changes in building design, physiologic adaptations, and improved emergency medicine. Nevertheless, because of a single major blackout on a warm day in 2003, Knowlton et al. (2004) maintain that “air conditioning may not really be an appropriate ‘fix’ for adapting to climate change.” Air conditioning is clearly a vital adaptive technology that has saved countless lives. One study reported a relative risk of death on hot days of 1.7 for people with no air conditioning compared to those with central air (Rogot et al. 1992). The nondiscriminating reader might be impressed by the downscaling of a general circulation model using a regional mesoscale model to predict localized differences in future air-pollution related mortality, but the complexity of the models is irrelevant in the face of Knowlton et al.’s failure to temper their theoretical exercise with real-world data. Had Knowlton et al. (2004) accounted for observed historical health and pollution trends and future emission-reduction requirements, they would have arrived at a markedly different story.

Studies related to oil and gas wells have attracted worldwide interest due to the increasing energy shortfall and the requirement of sustainable development and environmental protection. However, the state of oil and gas wells in terms of research characteristics, technological megatrends, article-produced patterns, leading study items, hot topics, and frontiers is unclear. This work is aimed at filling the research gaps by performing a comprehensive bibliometric analysis of 6197 articles related to oil and gas wells published between 1900 and 2021. VOSviewer and CiteSpace software were used as the main data analysis and visualization tools. The analysis shows that the annual variation of article numbers, interdisciplinary numbers, and cumulative citations followed exponential growth. Oil and gas well research has promoted the expansion of research fields such as engineering, energy and fuels, geology, environmental sciences and ecology, materials science, and chemistry. The top 10 influential studies mainly focused on shale gas extraction and its impact on the environment. More studies were produced by larger author teams and inter-institution collaborations. Elkatatny and Guo have greatly contributed to the application of artificial intelligence in oil and gas wells. The two most contributing institutions were the Southwest Petr Univ and China Univ Petr from China. The People’s Republic of China, the US, and Canada were the countries with the most contributions to the development of oil and gas wells. The authoritative journal in engineering technology was J Petrol Sci Eng, in environment technology was Environ Sci Technol, in geology was Aapg Bull, and in materials was Cement Concrete Res. The keyword co-occurrence network cluster analysis indicated that oil well cement, new energy development, machine learning, hydraulic fracturing, and natural gas and oil wells are the predominant research topics. The research frontiers were oil extraction and its harmful components (1992–2016), oil and gas wells (1997–2016), porous media (2007–2016), and hydrogen and shale gas (2012–2021). This paper comprehensively and quantitatively analyzes all aspects of oil and gas well research for the first time and presents valuable information about active and authoritative research entities, cooperation patterns, technology trends, hotspots, and frontiers. Therefore, it can help governments, policymakers, related companies, and the scientific community understand the global progress in oil and gas well research and provide a reference for technology development and application.

The recent proliferation of oil and natural gas energy development in the Greater Green River Basin of southwest Wyoming has accentuated the need to understand wildlife responses to this development. The location and extent of surface disturbance that is created by oil and natural gas well pad scars are key pieces of information used to assess the effects of energy infrastructure on wildlife populations and habitat. A digital database of oil and natural gas pad scars had previously been generated from 1-meter (m) National Agriculture Imagery Program imagery (NAIP) acquired in 2009 for a 7.7million hectare (ha) (19,026,700 acres) region of southwest Wyoming. Scars included the pad area where wellheads, pumps, and storage facilities reside and the surrounding area that was scraped and denuded of vegetation during the establishment of the pad. Scars containing tanks, compressors, the storage of oil and gas related equipment, and produced-water ponds were also collected on occasion. This report updates the digital database for the five counties of southwest Wyoming (Carbon, Lincoln, Sublette, Sweetwater, Uinta) within the Wyoming Landscape Conservation Initiative (WLCI) study area and for a limited portion of Fremont, Natrona, and Albany Counties using 2012 1-m NAIP imagery and 2012 oil and natural gas well permit information. This report adds pad scars created since 2009, and updates attributes of all pad scars using the 2012 well permit information. These attributes include the origination year of the pad scar, the number of active and inactive wells on or near each pad scar in 2012, and the overall status of the pad scar (active or inactive). The new 2012 database contains 17,404 pad scars of which 15,532 are attributed as oil and natural gas well pads. Digital data are stored as shapefiles projected to the Universal Transverse Mercator (zones 12 and 13) coordinate system. These data are available from the U.S. Geological Survey (USGS) at http://dx.doi.org/10.3133/ds934. 1 Garman, S.L., and McBeth, J.L., 2014, Digital representation of oil and natural gas well pad scars in southwest Wyoming: U.S. Geological Survey Data Series 800, 7 p., http://dx.doi.org/10.3133/ds800. 2 Biewick, L.R.H., and Wilson, A.B., 2014, Energy map of southwestern Wyoming, Part B—Oil and gas, oil shale, uranium, and solar: U.S. Geological Survey Data Series 843, 20 p., 4 pls., http://dx.doi.org/10.3133/ds843. Suggested citation: Garman, S.L., McBeth, J.L., 2015, Digital representation of oil and natural gas well pad scars in southwest Wyoming—2012 update [abs.]: U.S. Geological Survey Data Series 934, http://dx.doi.org/10.3133/ds934. For more information concerning this publication, contact: Center Director, USGS Geosciences and Environmental Change Science Center Box 25046, Mail Stop 980 Denver, CO 80225 (303) 236‒5344 Or visit the Geosciences and Environmental Change Science Center Web site at: http://gec.cr.usgs.gov/

Abstract. Recent increases in oil and natural gas (NG) production throughout the western US have come with scientific and public interest in emission rates, air quality and climate impacts related to this industry. This study uses a regional-scale air quality model (WRF-Chem) to simulate high ozone (O3) episodes during the winter of 2013 over the Uinta Basin (UB) in northeastern Utah, which is densely populated by thousands of oil and NG wells. The high-resolution meteorological simulations are able qualitatively to reproduce the wintertime cold pool conditions that occurred in 2013, allowing the model to reproduce the observed multi-day buildup of atmospheric pollutants and the accompanying rapid photochemical ozone formation in the UB. Two different emission scenarios for the oil and NG sector were employed in this study. The first emission scenario (bottom-up) was based on the US Environmental Protection Agency (EPA) National Emission Inventory (NEI) (2011, version 1) for the oil and NG sector for the UB. The second emission scenario (top-down) was based on estimates of methane (CH4) emissions derived from in situ aircraft measurements and a regression analysis for multiple species relative to CH4 concentration measurements in the UB. Evaluation of the model results shows greater underestimates of CH4 and other volatile organic compounds (VOCs) in the simulation with the NEI-2011 inventory than in the case when the top-down emission scenario was used. Unlike VOCs, the NEI-2011 inventory significantly overestimates the emissions of nitrogen oxides (NOx), while the top-down emission scenario results in a moderate negative bias. The model simulation using the top-down emission case captures the buildup and afternoon peaks observed during high O3 episodes. In contrast, the simulation using the bottom-up inventory is not able to reproduce any of the observed high O3 concentrations in the UB. Simple emission reduction scenarios show that O3 production is VOC sensitive and NOx insensitive within the UB. The model results show a disproportionate contribution of aromatic VOCs to O3 formation relative to all other VOC emissions. The model analysis reveals that the major factors driving high wintertime O3 in the UB are shallow boundary layers with light winds, high emissions of VOCs from oil and NG operations compared to NOx emissions, enhancement of photolysis fluxes and reduction of O3 loss from deposition due to snow cover.

The comments of Fedak et al. emphasize points we made in our paper (McKenzie et al. 2014) about the importance of conducting comprehensive and rigorous research on the health effects of oil and gas development. We dedicated much of our “Discussion” to describing the limitations of our study. However, Fedak et al. have overstated these limitations. As we stated in our paper (McKenzie et al. 2014), our study was limited by the lack of temporal and spatial specificity in using the density of existing gas wells around the maternal residence in the year of birth as the exposure. That being said, based on studies of maternal residential relocation during pregnancy, it is unlikely that a substantial proportion of subjects relocated during their pregnancy (Lupo et al. 2010; Miller et al. 2010). In addition, lack of temporal and spatial specificity of the exposure assessment would most likely have been similar for mothers with and without adverse outcomes and would have therefore resulted in weakened associations (Ritz and Wilhelm 2008; Ritz et al. 2007). Actual associations may be stronger that what we observed. Some nondifferential exposure misclassification in the analysis of birth defects likely resulted from using data on wells existing in the birth year rather than in the year in which the first trimester of pregnancy occurred. We do not know the extent and severity of this limitation, but in many cases, it is unlikely that the density of existing wells around the maternal residence would have changed dramatically over a few months. Our results support Fedak et al.’s statement that the most relevant benzene exposures will occur from nearby sources. Emissions from oil and gas wells are associated with the accumulation of benzene and other volatile organic compounds in the atmospheric surface layer in the general vicinity of oil and gas wells (Helmig et al. 2014). On average, one would expect more benzene emissions, and thus greater potential for benzene exposure, in areas with greater densities of natural gas wells. The results of our main analysis and sensitivity analyses indicate a linear dose response between increasing well density and the prevalence of congenital heart defects: The prevalence of congenital heart defects increases as the potential for benzene exposure increases. Fedak et al. misinterpret our sensitivity analysis and incorrectly state that the results are insignificant. In the sensitivity analysis, we did not restrict our analysis to 1- and 5-mile radii. Rather, we restricted our exposed group to 2- and 5-mile radii. Restricting the exposure definitions would have provided stronger and more accurate associations if exposure in the narrower radii were more accurate than in the 10-mile radius. Because the restriction to the narrower radii did not markedly change the results, we can infer that the 2-, 5-, and 10-mile radii were similarly accurate. Fedek et al. also take issue with benzene exposure as a plausible explanation for our findings because they assert that benzene is not a proven teratogen. Lack of direct evidence of causation between benzene and birth defects does not exclude the plausibility of benzene as a teratogen. Some studies have suggested an association between maternal exposure and birth defects (Lupo et al. 2011; Wennborg et al. 2005). Benzene is genotoxic, is known to cross the placenta, and has been associated with fetal demise [Agency for Toxic Substances and Disease Registry (ATSDR) 2007]. Although exposure to benzene is one plausible explanation for the observed associations, we stated in our paper that further research is needed to examine whether benzene is responsible for these associations and that other plausible explanations exist. Fedek et al.’s comments do not change our findings or conclusions. The results of our study suggest a positive association between greater density and proximity of natural gas wells within a 10-mile radius of maternal residence and greater prevalence of congenital heart defects and possibly neural tube defects, but not oral clefts, preterm birth, or reduced fetal growth. These results and the current trends in production underscore the importance of conducting additional research on the potential health effects of oil and gas development.

Completing the Bridge to Nowhere: Prioritizing Oil and Gas Emissions Regulations in Western States

Radioactivity surrounds us; each day we are exposed to a certain amount by virtue of being alive on planet Earth. Some of this exposure comes from radioactive substances (radionuclides) that occur naturally in a wide variety of geologic and soil formations. Occasionally these naturally occurring substances become more concentrated or accessible through human activities such as mining and nuclear energy production, resulting in greater potential for exposure than their original natural occurrence would suggest. Other radionuclides are artificially created. Residents in almost all parts of the United States live on lands that contain minor to substantial concentrations of radionuclides of one type or another.1 These substances often make their way into tap water, leading to exposures by ingestion, inhalation, or dermal pathways during showering or other contact with the water. Although radionuclides are widespread, there are large gaps in our knowledge about sources of these materials, their distribution, associated health risks, and mitigation measures. However, the information we do have suggests that current drinking water standards for radionuclides established by the U.S. Environmental Protection Agency (EPA) may not adequately protect health. The EPA is set to review these standards relatively soon, and the next two years are prime time for filling in numerous information gaps and doing other legwork to make sure the review is as well informed as possible.

Summary. Despite the promises of the Reagan administration to deregulate where practical and to reduce the number of new regulations, Congress continues to write and to enact more environmental legislation, and the U.S. Environmental Protection Agency (EPA) continues to develop more environmental regulations. The overall scale and impact of these regulations, largely ignored outside the affected industries, add greater momentum to the ongoing petroleum industry restructuring process. The Promise of Deregulation One of the promises of the Reagan administration was to return government to the people by cutting back on unnecessary regulations. Overall, the number of new federal regulations has been cut from the level of previous administrations. The amount of paperwork required of businesses has been reduced. New regulatory proposals undergo far greater administration scrutiny at the Office of Management and Budget than in earlier years. The Environmental Exception As with all generalizations, a major exception exists. That exception has been environmental regulation. Although the first Reagan appointee to head EPA, Anne Burford, succeeded in reducing some EPA regulations, the scope of environmental regulation continued to grow even during her tenure. Since 1980, the federal office dealing with noise pollution has been eliminated. but Congress has enacted wider statutory authority for regulating hazardous wastes, groundwater contamination, and drinking water supplies. Congress has also used its oversight of EPA to force a stepped-up enforcement of a wide range of environmental laws. In addition, EPA has continued to issue more and stiffer regulations covering all areas of the environment. In particular, EPA has added new oft-ices and new or substantially increased programs covering groundwater, marine and estuarine protection, underground storage tanks, wetlands protection, and hazardous air pollutants. Despite administration concerns about budgetary impacts and program effectiveness, Congress has enacted legislation expanding the Superfund program, the Safe Drinking Water Act, the Resource Conservation and Recovery Act (RCRA), and the Clean Water Act, extending EPA's regulatory responsibilities. Along with these added duties have come new and tighter statutory deadlines, more rigorous environmental standards, and greater financial burdens on the affected industries and states. Virtually all these additions to environmental law and their accompanying regulations will impact the petroleum industry. Some impacts, such as the tax increases under the Superfund Amendments and Reauthorization Act (SARA), can probably be partially passed on to the ultimate consumer. Others cannot. While some environmental regulations are well known to the entire industry, others are obscure or known only to that segment of the industry primarily impacted. It is clear that few, if any, government policy makers and legislators seem to have grasped the overall immediate and midterm impacts of these regulations on the petroleum industry. Even less well understood are the long-term impacts of continuing additional environmental regulatory requirements. In addition to the impact of more recent environmental laws, older statutes continue to place requirements on the industry. The Clean Air Act and the Clean Water Act and their accompanying regulations have basic programs that are well understood and have not changed substantially in the last decade. As well understood as they are, however, both the Clean Air Act and the Clean Water Act have a few surprises left. The Clean Air Act Despite the apparent maturity of the Clean Air Act, EPA continues to impose additional requirements on the petroleum industry. For example, in 1985, EPA required stricter new source performance standards (NSPS) for natural gas processing plants to reduce volatile organic compound emissions by 73 % by tightening standards for valves, compressors. and pumps. Another NSPS rule was published that would reduce sulfur dioxide emissions from new or rebuilt onshore natural gas sweetening plants. EPA estimated the capital cost at over $93 million for the plants involved. During 1985, EPA's lead phase-down rule almost totally eliminated lead in gasoline, with a possible cost to refiners of up to $0.02/gal [$5.301m 3 ] and an eventual annual cost to the industry of from $450 million to $600 million. Until recently, EPA has taken few actions under Sec. 112 of the Clean Air Act-the section requiring EPA to list those air pollutants that are especially toxic and to develop rules that restrict or ban their emissions. P. 1113^

The Marcellus Shale is one of the largest natural gas reserves in the United States; it has recently been the focus of intense drilling and leasing activity. This paper describes an air emissions inventory for the development, production, and processing of natural gas in the Marcellus Shale region for 2009 and 2020. It includes estimates of the emissions of oxides of nitrogen (NOx), volatile organic compounds (VOCs), and primary fine particulate matter (≤2.5 µm aerodynamic diameter; PM2.5) from major activities such as drilling, hydraulic fracturing, compressor stations, and completion venting. The inventory is constructed using a process-level approach; a Monte Carlo analysis is used to explicitly account for the uncertainty. Emissions were estimated for 2009 and projected to 2020, accounting for the effects of existing and potential additional regulations. In 2020, Marcellus activities are predicted to contribute 6–18% (95% confidence interval) of the NOx emissions in the Marcellus region, with an average contribution of 12% (129 tons/day). In 2020, the predicted contribution of Marcellus activities to the regional anthropogenic VOC emissions ranged between 7% and 28% (95% confidence interval), with an average contribution of 12% (100 tons/day). These estimates account for the implementation of recently promulgated regulations such as the Tier 4 off-road diesel engine regulation and the U.S. Environmental Protection Agency's (EPA) Oil and Gas Rule. These regulations significantly reduce the Marcellus VOC and NOx emissions, but there are significant opportunities for further reduction in these emissions using existing technologies. Implications: The Marcellus Shale is one of the largest natural gas reserves in United States. The development and production of this gas may emit substantial amounts of oxides of nitrogen and volatile organic compounds. These emissions may have special significance because Marcellus development is occurring close to areas that have been designated nonattainment for the ozone standard. Control technologies exist to substantially reduce these impacts. PM2.5 emissions are predicted to be negligible in a regional context, but elemental carbon emissions from diesel powered equipment may be important.