Naturally occurring radionuclides are widely distributed in the earth's crust, so it's no surprise that mineral and hydrocarbon extraction processes, conventional and unconventional alike, often produce some radioactive waste. Radioactive drilling waste is a form of TENORM (short for "technologically enhanced naturally occurring radioactive material")—that is, naturally occurring radioactive material (NORM) that has been concentrated or otherwise made more available for human exposure through anthropogenic means. Both the rapidity and the extent of the U.S. natural gas drilling boom have brought heightened scrutiny to the issues of radioactive exposure and waste management.
A lined impoundment receives waste at a fracking site in Dimock, Pennsylvania.
© J. Henry Fair
Perhaps nowhere is the question of drilling waste more salient than in Pennsylvania, where gas extraction from the Marcellus Shale using hydraulic fracturing (fracking) made the state the fastest-growing U.S. producer between 2011 and 2012. The Marcellus is known to have high uranium content, says U.S. Geological Survey research geologist Mark Engle. He says concentrations of radium-226—a decay product of uranium—can exceed 10,000 picocuries per liter (pCi/L) in the concentrated brine trapped in the shale's depths.
To date the drilling industry and regulators have considered the risk posed to workers and the public by radioactive waste to be minor. In Pennsylvania, Lisa Kasianowitz, an information specialist with the state Department of Environmental Protection (PADEP), says there is currently nothing to "indicate the public or workers face any health risk from exposure to radiation from these materials." But given the wide gaps in the data, this is cold comfort to many in the public health community.