The Environmental Protection Agency last month issued revised permits for oil companies to dump literally rivers of wastewater—including hydraulic fracturing fluids—on the Wind River Reservation in Wyoming.

When the companies pump oil, water from deep in the earth comes up too. This water can include naturally occurring substances, such as metals, that can pollute streams. It can also include toxic chemicals the companies injected into the wells during hydrofracturing to make the oil flow better. Under these EPA permits, the companies release water onto the dry ground in quantities large enough to create permanent streams. Some flow for long distances on the arid reservation and join the Wind River and Little Wind River.

Public Employees for Environmental Responsibility, an environmental watchdog group, plans to appeal the five permits this week, arguing that they are illegal because they do not set limits for many of the chemicals the companies inject in the wells or require adequate monitoring of pollutants.

“Against all reason, EPA is refusing to regulate fracking fluids even after they flow back to the surface and are pumped into streams,” Jeff Ruch, PEER’s executive director, said in a statement announcing the appeal.

Some of the chemicals the companies have told the EPA they are adding to the wells, or that have been found in the wastewater, include benzene, arsenic and hydrogen sulfide. These chemicals are known to or likely to cause cancer or other serious effects when consumed or breathed in at high enough concentrations. The remote streams of wastewater are used by livestock and wildlife, but not by people as drinking water, creating a regulatory loophole.

I first learned about the loophole, which the EPA uses to issue National Pollutant Discharge Elimination System permits, when I worked for NPR. I reported two stories based on a visit to several oilfields on the reservation and documents obtained from the EPA with two separate Freedom of Information Act requests.

When the EPA was banning oil companies from dumping their wastewater decades ago, ranchers, especially in Wyoming, argued that livestock needed the water. So in 1979, the EPA made an exception for the arid West: If oil companies demonstrated that livestock or wildlife use the water, the companies could release it, literally creating streams of noxious water that are barely regulated.

Environmental scientists criticized the EPA for allowing the releases. That’s because modern drilling techniques can require a lot of chemicals that flow out of wells during the production process.

Legal scholars say the EPA’s loophole raises questions of environmental justice, because states do in fact regulate such releases when they are not on reservations, and their rules appear stricter.

“It’s completely nonsensical that the discharges allowed on the reservation would not be allowed off the reservation,” said Hillary Hoffmann, a professor at Vermont Law School who has been researching this loophole in recent years and plans to publish a paper on it this summer. “They’ve drawn this random line that is in no way protective of human health and the environment.”

However, in its comments the EPA disagrees, saying “the permits drafted by EPA are as, or more, stringent in controlling specific pollutants as similar permits issued by the Wyoming Department of Environmental Quality.”

The newly revised permits tighten limits for some contaminants in the wastewater and include limits for a couple more chemicals than in previous permits. One of the five permits, for example sets seven “effluent limitations” and prohibits foam or solids on the water except in trace amounts. The revised permits also require these companies to test the water to see if small fish or aquatic insects die when exposed to it, and to send the EPA an inventory of chemicals they inject down the wells.

But legal scholars and environmentalists criticized the EPA for not requiring prior public disclosure of hundreds of chemicals and other ingredients that the companies might use in hydraulic fracturing fluids. Neither do they require testing for them.

“It looks like what they’re testing for is what they accidentally found in the water,” Hoffmann said. “But the problem is there might be 450 others that they’re slipping in the waste stream.”

In responses to public comments, the EPA conceded that it set the new permit requirements without knowing what chemicals companies are injecting.

“EPA did not have sufficient information on quantities and concentrations of chemical substances either provided by the permittee or available from publicly available information sources (e.g., websites such as FracFocus), to assess whether any of the pollutants potentially present in the well treatment fluids … will cause toxicity in the produced water discharge,” EPA said in a document released with the permits.

Under new chemical inventory requirements in these revised permits, the EPA will know more in the future.

PEER, however, said it is worried that these permits could open the door for more lax regulations elsewhere. Last year the group petitioned the EPA to prohibit companies from releasing wastewater that includes hydraulic fracturing fluids. The EPA has not responded.

“(T)his water is utterly unfit for human or animal consumption, and exposure to it can cause severe health problems and, in some cases, even result in death,” PEER said in its petition to the EPA. “EPA must rectify its position and take action to prevent the further discharge of these dangerous chemicals.”

Hoffmann, who is both an expert in Indian law and natural resources law, said the EPA was abdicating its responsibility under the federal trust doctrine. “They’re creating a loophole that allows discharges to happen without any disclosure to the tribes about what they’re getting,” she said, “which I think is pretty scary.”