Editor’s Note, Oct. 9: Based on several comments that mentioned that the Josephine Brine Treatment Facility stopped treating fracking wastewater in 2011, we did a bit of digging and found that the treated water downstream from the plant still showed signatures that fresh fracking water had run through it, according to the study’s authors. The post has been revised with this information, along with the fact that treatment does remove a good bit of contamination.

In the state of Pennsylvania, home to the lucrative Marcellus Shale formation, 74 facilities treat wastewater from the process of hydraulic fracturing (a.k.a. “fracking”) for natural gas and release it into streams. There’s no national set of standards that guides this treatment process—the EPA notes that the Clean Water Act’s guidelines were developed before fracking even existed, and that many of the processing plants “are not properly equipped to treat this type of wastewater”—and scientists have conducted relatively little assessment of the wastewater to ensure it’s safe after being treated.

Recently, a group of Duke University scientists decided to do some testing. They contacted the owners of one treatment plant, the Josephine Brine Treatment Facility on Blacklick Creek in Indiana County, Pennsylvania, but, “when we tried to work with them, it was very difficult getting ahold of the right person,” says Avner Vengosh, an Earth scientist from Duke. “Eventually, we just went and tested water right from a public area downstream.”

Their analyses, made on water and sediment samples collected repeatedly over the course of two years, were even more concerning than we’d feared. As published today in the journal Environmental Science and Technology, they found elevated concentrations of the element radium, a highly radioactive substance. The concentrations within sediments in particular were roughly 200 times higher than background levels. In addition, amounts of chloride and bromide in the water were two to ten times greater than normal.

This is despite the fact that treatment actually removes most of the contaminants from the wastewater–including 90 percent of the radium. “Even if, today, you completely stopped disposal of the wastewater,” Vengosh says, there’s enough contamination built up in sediments that “you’d still end up with a place that the U.S. would consider a radioactive waste site.”

In recent years, the use of fracking to extract natural gas from shale formations has boomed in several areas, most notably Pennsylvania’s Marcellus Shale, which has been called “the Saudi Arabia of natural gas.” The process involves injecting mix of water, sand and proprietary chemicals deep into rock at high pressure, causing the rock to fracture and allowing methane gas to seep upward for extraction.

Much of the concern over fracking has related to the seepage of these chemicals or methane from drilling wells into groundwater or the fact that high-pressure injection can trigger earthquakes, but the wastewater recently tested presents a separate, largely overlooked problem.

Between 10 and 40 percent of fluid sent down during fracking resurfaces, carrying contaminants with it. Some of these contaminants may be present in the fracking water to begin with. But others are leached into the fracking water from groundwater trapped in the rock it fractures.

Radium, naturally present in the shales that house natural gas, falls into the latter category—as the shale is shattered to extract the gas, groundwater trapped within the shale, rich in concentrations of the radioactive element, is freed and infiltrates the fracking wastewater.

Other states require this wastewater to be pumped back down into underground deposit wells sandwiched between impermeable layers of rock, but because Pennsylvania has few of these cavities, it allows fracking wastewater to be processed by normal wastewater treatment plants and released into rivers.

In 2011, Pennsylvania Department of Environmental Protection (PADEP) issued a recommendation that plants, including Josephine, voluntarily stop treating fracking wastewater. But Jim Efstathiou Jr. at Bloomberg News reports that, even though spokespeople at PADEP and Josephine say that the plant has stopped treating fracking wastewater, those claims are “contradicted by today’s study, which shows that the Josephine plant continued to treat Marcellus Shale wastewater through the beginning of this year,” according to Vengosh.

“Based on the isotopes that we measured we can see that the effluent that’s coming from Josephine in the last three years, including two months ago, still has the fingerprint of the Marcellus,” Vengosh told Efsathiou.

The treatment plants, many scientists note, are not designed to handle the radioactive elements present in the wastewater. Neither are they required to test their effluent for radioactive elements. As a result, many researchers have suspected that the barely-studied water they release into local streams retains significant levels of radioactivity.

This new work confirms that suspicion for at least one plant—which as about an hour east of Pittsburgh, and releases effluent into the watershed that supplies the city’s drinking water—and Vengosh believes that the findings would likely be similar for many of the other facilities in Pennsylvania. Especially concerning is the fact that, apart from in the water, the team found high levels of radioactivity accumulating on the sediments at the bottom of the stream over time. Radium has a half-life of 1600 years, so unless these sediments are removed, they’ll keep releasing radiation into the water for an extremely long period.

In addition, the high levels of bromide found in the wastewater is a concern, because even in slight quantities, the compound can trigger the formation of a toxic class of chemicals called halomethanes when it’s combined with chlorine. This is a problem because in rural areas, many residents treat well water by chlorinating it.

The study—which is part of a larger Duke project studying the effect of fracking on water—doesn’t show that fracking is inherently unsafe, but does show that without proper controls, the wastewater being dumped into the environment daily represents a very real danger for local residents.

Vengosh notes that there are better methods of treating fracking wastewater (he points to the plants operated by Eureka Resources as a model for adequately removing radioactivity), but these are more expensive to operate. But currently, without the push of federal regulations, companies looking to dispose of wastewater have no incentive to pay for this type of solution.