HARRISBURG, Pennsylvania — Pennsylvania state environmental regulators released a study Thursday on radiation levels in oil and gas industry wastewater and byproducts that they say shows little potential for direct radiation exposure to workers and the public. But it recommends a follow-up study to determine whether radiation can build up in the environment.
The 200-page study began in 2013 after questions arose about the radioactivity in the huge volumes of wastewater and solid waste coming out of the ground in Pennsylvania's natural gas drilling boom.
State officials had said drilling waste had triggered radiation monitors at landfills but cautioned that very low levels of naturally occurring radioactive materials were found in the drilling waste.
Since the study began, researchers from Duke University have reported finding high levels of radiological elements in sediments downstream of a treatment facility on western Pennsylvania's Blacklick Creek, a tributary of the Allegheny River, that had handled drilling wastewater.
The study by Pennsylvania's Department of Environmental Protection was peer-reviewed, it said, and included sampling at well sites, wastewater treatment plants, landfills and roads treated by oil and gas wastewater.
"There is little potential for additional radon exposure to the public due to the use of natural gas extracted from geologic formations located in Pennsylvania," it said.
However, it also cautioned that a buildup of radiological elements in the environment is possible from spills and at facilities that treat the waste, and those areas should be studied for the need to clean them up.
In addition, filter residue from wastewater treatment facilities will require safe long-term disposal, it said, and it urged further study of the impact of using oil and gas wastewater for dust suppression and road stabilization.
A buildup of radiological elements in the environment, such as river sediment, can result in its absorption into living systems, whether plants or fish, researchers say.
Drilling for natural gas into Pennsylvania's Marcellus Shale formation can require injecting huge volumes of water underground to help shatter the rock — a process called hydraulic fracturing. Some of that water returns to the surface, in addition to the gas, as ultra-salty brine tainted with metals like barium and strontium.
Particles in the water are also often tainted with radium, a naturally occurring radioactive substance.
In 2011, Pennsylvania barred drillers from taking the wastewater to municipal treatment facilities, effectively forcing them to haul the fluid to underground injection wells or to recycle it on-site.