Air pollution monitoring strategies for assessing emissions of volatile organic compounds from oil and gas development

Oil and gas developments, whether from tight sandstone or shale, have an array of air pollutant emission sources related to drilling, production, and transmission activities. Emissions of oxides of nitrogen (NOx) and volatile organic compounds (VOC) are important, in terms of the level of emissions and the potential for impacts upon human health. Together NOx and VOC reactively combine to create ozone. Ozone and nitrogen dioxide are both regulated through mandated National Ambient Air Quality Standards as defined by the Clean Air Act. The impact of oil and gas emissions is nevertheless case specific. Developments in populated areas can raise human health concerns that result from VOC emissions. The ratio of non-methane hydrocarbons (NMHC) to methane emissions from natural gas wells is often of particular importance. While methane is a significant greenhouse gas, higher levels of NMHC in produced wet gas lead to the production of a higher level of condensate. Condensate compositions vary between fields but the aromatic hydrocarbons; benzene, toluene, ethylbenzene, m+p-xylene and o-xylene, collectively known as BTEX, are of particular concern for both chronic and acute exposures. These compounds are all included in the US EPA Air Toxic Pollutants list. The US Department of Health and Human Services and the International Agency for Cancer Research both classify benzene as a human carcinogen. Long-term exposure is associated with leukemia and other blood related health problems. Results of VOC and BTEX monitoring in ambient air from the Pinedale Anticline in Wyoming are presented. Based on these and other measurements associated with oil and gas developments, a strategy for air quality impact assessment that includes measuring methane, NMHC and selected VOC is proposed. In addition, health impact assessments of communities with nearby oil and gas developments are considered, in the context of current legislative and air quality management frameworks.