...[H]undreds of thousands of new wells and drilling rigs...[are exploring] for natural gas...[D]rilling companies have only in recent years developed techniques to unlock the enormous reserves...[Using] the relatively new drilling method — known as...hydrofracking...a well can produce over a million gallons of wastewater that is often laced with...carcinogens like benzene and radioactive elements like radium...Other carcinogenic materials can be added...by the chemicals used in the hydrofracking...[I]nternal documents obtained...from the Environmental Protection Agency, state regulators and drillers show that the dangers to the environment and health are greater than previously understood. The documents reveal that the wastewater, which is sometimes hauled to sewage plants not designed to treat it and then discharged into rivers that supply drinking water, contains radioactivity at levels...far higher than the level that federal regulators say is safe... [refers to Shell, Chesapeake Energy]