Long-Term Trends in Air Quality in Unconventional Oil and Gas Development Regions in the United States

This report, available for download below, presents a study led by Gunnar W. Schade (Texas A&M University) and Detlev Helmig (Boulder AIR). Schade, Helmig, and colleagues evaluated long-term air quality trends across unconventional oil and gas development (UOGD) regions in the United States, primarily in Texas (1997–2023) and Colorado (2008–2024).

Key takeaways:

• The investigators compiled publicly available data on methane, nonmeth­ane hydrocarbons, and nitrogen oxides (NOx) concentrations from air quality monitoring stations in each state. They then evaluated long-term air quality trends associated with UOGD in both states using statistical techniques for analyzing time-series data.
• Long-term trends in nonmethane hydrocarbon and NOx concentrations increased and then stabilized over time in Texas, generally correlating with regional UOGD production volumes in the state. In contrast, long-term trends in nonmeth­ane hydrocarbon and NOx concentrations declined over time in Colorado, and methane growth was slower than the global background, while UOGD production continued to increase.
• These findings suggest that emissions levels near UOGD are likely declining in Colorado but not noticeably in Texas, demonstrating that differences in long-term trends in air pollutant concentrations near UOGD in Texas and Colorado reflect differences in a mix of local and regional factors in each state.