in june 2014 public health england published a review of the potential public health impacts of exposures to chemical and radioactive pollutants as a result of shale gas extraction in the uk, based on the examination of literature and data from countries where hydraulic fracturing already occurs. the executive summary of the report stated: "an assessment of the currently available evidence indicates that the potential risks to public health from exposure to the emissions associated with shale gas extraction will be low if the operations are properly run and regulated. most 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."