**Abstract**

 Advances in hydraulic fracturing technologies, and unconventional oil and gas (UOG) generally, spurred a boom in energy production in the United States. The rapid expansion of UOG has brought oil and gas production closer to homes, schools, and work places and thus increased potential human exposure to a range of chemicals, pollutants, and other health risks. Releases of such chemicals and pollutants occur throughout the full life cycle of UOG beginning with well-site preparation and continuing through hydraulic fracturing, well completion into production, well maintenance, and finally the plugging or abandoning of the well. While the risks to workers on UOG sites differ from those living, working or recreating nearby, both groups may be exposed to chemical and hazardous materials and injuries related to accidents and spills. This chapter characterizes the main occupational and public health risks throughout the life cycle of a hydraulically fractured well. Focusing on common practices in the United States, it identifies the main types of risks and pathways for human exposure. As a review, the chapter summarizes the peer-reviewed literature available to date, highlighting regulatory responses and identifying gaps in the current understanding of the risks involved in hydraulic fracturing.

**Keywords:** hydraulic fracturing, unconventional oil and gas development, health risk, air pollution, water pollution, occupational health risks, psychosocial health risks
