Elevated levels of radioactivity have been found in a western Pennsylvania creek where treated water from fracking is discharged. High concentrations of salts and metals were also found, Science Daily reports.

“Radium levels were about 200 times greater in sediment samples collected where the Josephine Brine Treatment Facility discharges its treated wastewater into Blacklick Creek than in sediment samples collected just upstream of the plant,” Avner Vengosh, professor of geochemistry and water quality at Duke University, told Science Daily.

Levels of salinity in the discharged waste from the Josephine Brine Treatment Facility were also up to 200 times higher than allowable levels under the Clean Water Act, and 10 times saltier than ocean water, Vengosh told Live Science.

Industry sometimes pumps wastewater deep into the ground to injection wells in order to dispose of it, but sometimes the fracking waste is treated and released into the environment. While wastewater can be treated, some states do not have the technology to remove chemicals and radioactivity, and insufficient treatment of wastewater can be an issue.

The Duke study tested shale gas wastewater from hydraulic fracturing as well as stream water from above and below the discharge site from the treatment facility. “The radioactivity levels we found in sediments near the outflow are above management regulations in the U.S. and would only be accepted at a licensed radioactivity disposal facility,” said Robert B. Jackson, professor of environmental science at Duke.

The researchers found that the amount of radioactivity that has accumulated in river sediments as a result of fracking wastewater being released into the environment has created potentially long-term environmental risks.

“While water contamination can be mitigated by treatment to a certain degree, our findings indicate that disposal of wastewater from both conventional and unconventional oil and gas operations has degraded the surface water and sediments,” Nathaniel R. Warner, a Ph.D. graduate of Duke, told Science Daily. “This could be a long-term legacy of radioactivity.”

Heavy metals occur naturally in the ground in some regions. Hydraulic fracturing wastewater treatment removes some of the radioactivity, but does not remove many salts, including bromide. When naturally-occurring radioactive materials, heavy metals, and salts are released into the environment via wastewater, levels can become unsafe.

In the case of Blacklick Creek in Pennsylvania, there is the issue that increased bromide can mix with chlorine and ozone, which are used to disinfect river water and produce drinking water, leading to a greater risk of the formation of “highly toxic” byproducts in drinking water treatment facilities located downstream from the wastewater treatment plant.

In August, a study by researchers at the University of Texas at Arlington found high levels of arsenic and other heavy metals in aquifers overlying the Barnett Shale formation in northern Texas near active natural gas wells. Samples exceeding the EPA’s Maximum Contaminant Limit (MCL) were found throughout areas of active fracking.

As the study’s lead author, Brian Fontenot, pointed out, “These heavy metals do occur in the groundwater in this region. But we have a historical dataset that points to the fact that the levels we found are sort of unusual and not natural. These really high levels differ from what the groundwater used to be like before fracking came in.”

Of course, residents in many states have long been reporting water contamination due to hydraulic fracturing. Industry continues to deny the dangers of the practice, but emerging research is beginning to document its potentially long-term and damaging effects.

Alisha is a writer and researcher with Ring of Fire. Follow her on Twitter @childoftheearth.