Like other rock formations, shales can contain high concentrations of naturally occurring radioactive material (NORM), e.g. radium, uranium and thorium. NORM as a potential contaminant for ground water may be released to the environment by  several mechanisms related to unconventional petroleum exploration/production: flowback water spills on the surface, leakage of flowback from containment ponds, well casing failure, and introduction of new/larger fractures to the subsurface. 

Recently, some studies have addressed the potential environmental impact of NORM from shale gas operations. Overall, the studies suggest little potential of NORM from shale gas operations to harm the public. However, the number of studies  is very limited and more investigations are needed on analytical methodologies as well as on site-specific and regional studies.

Technologically Enhanced Naturally Occurring Radioactive Materials (TENORM) Study Report

The Pennsylvania Department of Environmental Protection released Technologically Enhanced Naturally Occurring Radioactive Materials (TENORM) Study Report on Jan. 15, 2015. While the study outlines recommendations for further research, it concluded there is little potential for harm to workers or the public from radiation exposure due to oil and gas development. 

Monitoring radionuclides in subsurface drinking water sources near unconventional drilling operations: a pilot study

Journal of Environmental Radioactivity,  April 2015 (Link to abstract)

From the abstract: This pilot study investigated the levels of natural uranium, lead-210, and polonium-210 in private drinking wells within 2000 m of a large-volume hydraulic fracturing operation – before and approximately one-year following the fracturing  activities. Observed radionuclide concentrations in well waters tested did not exceed maximum contaminant levels recommended by state and federal agencies. No statistically-significant differences in radionuclide concentrations were observed in well-water samples collected before and after the hydraulic fracturing activities.

The flux of radionuclides in flowback fluid from shale gas exploitation

Environmental Science and Pollution Research, November 2014 (link to article, link to research brief)

From abstract and conclusions: This study considers the flux of radioactivity in flowback fluid from shale gas development in three areas: the Carboniferous Bowland Shale, UK; the Silurian Shale, Poland; and the Carboniferous Barnett Shale, USA, and compares fluxes with radionuclide emissions from other technologies. The authors conclude that shale gas exploitation will result in an increased flux of radioactive elements to controlled waters including to surface waterbodies. However, fluxes are within a range of those that might be experienced elsewhere in the world from use of natural groundwaters.

These studies address methodologies to analyse the radium concentrations in flowback water:

Analysis of Radium-226 in High Salinity Wastewater from Unconventional Gas Extraction by Inductively Coupled Plasma-Mass Spectrometry

Environmental Science & Technology Letters, February 2015 (link to article)

Matrix Complications in the Determination of Radium Levels in Hydraulic Fracturing Flowback Water from Marcellus Shale

Environmental Science & Technology Letters, February 2014 (link to article)