http://rwma.com/Marcellus%20Shale%20Report%205-18-2010.pdf
Brine water can be contained in the rock formations for centuries and can contain extremely high levels of water-soluble radionuclides that are present in the underground formations. In addition to mixing with brine, the drilling fluid may also become contaminated when it comes in contact with radioactive rock. Radium-226 is a highly water-soluble radionuclide and will preferentially dissolve in the drilling fluid under the pressure and temperature conditions below ground. Drilling fluid can be reused many times and radium will progressively concentrate in it after each reuse. Since no sources specify the radioactivity of produced water, we assume that it is the same asbrine, which is measured at 15,000 pCi/L.

Soil Contamination
Radium-226 has a half-life of 1600 years and, if deposited in the
landfill, will remain there essentially forever. Landfill workers that come in contact with the contaminated materials may be exposed. Further, if the landfill is ever inhabited in the future, crops grown in the soil will concentrate radium and be ingested. Ra-226 is a carcinogen and, when ingested or inhaled, concentrates in the bone and can cause leukemia. Those who eat fruits or vegetables grown more than 1,000 years in the future over the closed landfill or buried impoundments would exceed current health-based dose limits.