Oilfields are spinning off thousands of tons of low-level radioactive trash as the U.S. drilling boom leads to a surge in illegal dumping. The waste is a byproduct of drilling, as it unlocks naturally occurring radium from shale rock formations, during fracking. This waste is often buried at the extraction site, dumped illegally, or sent to local landfills. The extraction process displaces radium-tinged subterranean water that comes up through the wells, where it can taint soil and surface equipment. Radiation levels can build up in sludge at the bottom of tanks, pipeline scale, and other material that comes in extended contact with wastewater.