OIL AND GAS WASTEWATER: WHAT WE KNOW ABOUT POTENTIAL EXPOSURE PATHWAYS TO HUMANS (Invited Presentation)

Produced water is a chemically complex wastewater co-produced during the development of oil and gas. Roughly four trillion liters were generated in the United States in 2021 alone. Much of this water is re-injected into the subsurface and has been associated with localized increases in seismic activity. Produced-water reuse not only seeks to limit risks posed by re-injection, but also to offset and reduce freshwater demands in water-stressed regions and to explore critical mineral extraction potential. Water managers and end users need to understand potential human exposures from current and proposed produced water uses and management practices. In this presentation we summarize what is known about human exposure to produced water from onshore oil and gas development in the United States. We identify knowledge gaps with the purpose of informing decisions about the management of produced water in a manner that may better protect human health. We also synthesize the research into a conceptual model of potential human exposure that illustrates the current state of scientific inquiry and knowledge based on a scoping review of literature using two databases curated by the U.S. Geological Survey and HEI Energy. People can be exposed to produced water through surface spills or leaks. Exposure can also arise from planned releases, such as permitted surface-water discharges, crop irrigation, and road treatment for ice or dust. Knowledge gaps remain in understanding the variable composition and toxicity of produced water released to various ecosystems, the efficacy and economic feasibility of treatment methods required for safe use, migration pathways through the environment that can result in human exposure, and the significance of the exposures for health. Reducing these uncertainties could allow the benefits of produced-water reuse to be more fully realized while simultaneously protecting human and environmental health.