evidence suggests that contamination of groundwater, if it occurs, is most likely to be caused by leakage through the vertical borehole. Contamination of groundwater from the underground hydraulic fracturing process itself (i.e. the fracturing of the shale) is unlikely. However, surface spills of hydraulic fracturing fluids or wastewater may affect groundwater, and emissions to air also have the potential to impact on health. Where potential risks have been identified in the literature, the reported problems are typically a result of operational failure and a poor regulatory environment." A 2012 report prepared for the European Union Directorate-General for the Environment identified potential risks to humans from air pollution and ground water contamination posed by hydraulic fracturing. This led to a series of recommendations in 2014 to mitigate these concerns. A 2012 guidance for pediatric nurses in the US said that hydraulic fracturing had a potential negative impact on public health and that pediatric nurses should be prepared to gather information on such topics so as to advocate for improved community health. A 2017 study in The American Economic Review found that "additional well pads drilled within 1 kilometer of a community water system intake increases shale gas-related contaminants in drinking water." A 2022 study conduced by Harvard T.H. Chan School of Public Health and published in Nature Energy found that elderly people living near or downwind of unconventional oil and gas development (UOGD) -- which involves extraction methods including fracking—are at greater risk of experiencing early death compared with elderly persons who don't live near such operations. Statistics collected by the U.S. Department of Labor and analyzed by the U.S. Centers for Disease Control and Prevention show a correlation between drilling activity and the number of occupational injuries related to drilling and motor vehicle accidents, explosions, falls, and fires. Extraction workers are also at risk for developing pulmonary diseases, including lung cancer and silicosis (the latter because of exposure to silica dust generated from rock drilling and the handling of sand). The U.S. National Institute for Occupational Safety and Health (NIOSH) identified exposure to airborne silica as a health hazard to workers conducting some hydraulic fracturing operations. NIOSH and OSHA issued a joint hazard alert on this topic in June 2012. Additionally, the extraction workforce is at increased risk for radiation exposure. Fracking activities often require drilling into rock that contains naturally occurring radioactive material (NORM), such as radon, thorium, and