For about 40 years, state workers have been dumping saltwater left over from oil production on some North Dakota roads. That's news to the health department, which wants the practice stopped.

The Transportation Department claims oil well wastewater - up to 10 times saltier than sea water - is a safe, effective and cheap deicer.

Environmentalists are stunned that workers have been dumping tens of thousands of gallons of the potentially contaminated stuff on roads every year, causing unknown harm to wetlands, streams and water supplies.

"I can't imagine anybody would sign off on this," said Wayde Schafer, a North Dakota spokesman for the Sierra Club.

"When it leaves the well site and is in an oil company truck it's considered toxic material," Schafer said. "If they have just one drip from the truck, they're fined. But when it's transferred to a state truck, it's spread wholesale along the interstate. It definitely makes one wonder."

Transportation spokeswoman Peggy Anderson said the state Health Department had approved the use of the salty wastewater for de-icing. But the health department's water quality director, Dennis Fewless, said he hadn't even heard about the practice until asked about it this week by the Associated Press.

"In our opinion, we did not give them our blessing on this practice," Fewless said Friday.

Fewless said the wastewater pulled from oil wells may contain oil and chemicals from drilling operations.

"The bottom line is, we need to look to the future and look for better options and phase this process out," Fewless said.

Transportation Department officials say they have not seen any ill effects caused by the saltwater, such as dead vegetation along highways or rustier-than-normal vehicles.

Transportation engineer Brad Darr said the saltwater has been used on state roads in the Dickinson area of southwestern North Dakota since the late 1960s, and that the practice has expanded to some other parts of the state in the last decade.

Darr said the Transportation Department had no exact figure, but uses "tens of thousands of gallons" of the saltwater each year, at no charge from the oil companies - who otherwise would have to pay someone to haul it off.

"They can have all they want," said Dave Wanner, a manager at Missouri Basin Well Service in Belfield.

Darr said the use of the oil field wastewater has been expanded in the last decade to state roads in Williston, Minot and Devils Lake.

Larry Gangl, the district engineer for the Transportation Department in Dickinson, said about 30 gallons of the undiluted saltwater is applied each mile to slick highways. Sometimes it is mixed with sand, he said.

"It cuts through the ice, and helps sand stick to the ice," Gangl said.

Gangl said the salty water has been applied in just the past couple of years before a predicted storm. That led to a few complaints, he said, but he believes it helps keep roads safe.

"We're doing it for the safety of the traveling public," Gangl said. "Once they hear that they are pretty fine with it."

Schafer, of the Sierra Club, said his group has found no other states that use oil well saltwater for de-icing.

Charity Watt Levis, a spokeswoman for the Montana Department of Transportation, said the state does not use the salt brine from oil wells.

"It is something that we looked at - not something that we've really studied closely - but on the surface, it looks as though the heavy metals that might be in there wouldn't meet the Montana Department of Transportation specifications," she said.

Wanner said the saltwater may contain traces of oil residue with a "little tiny film to it," but that it is not dangerous to the environment if applied sparingly.

"It's not that nasty at all. You don't see dead grass along the highways out here," Wanner said. "They don't put it on that heavy."

A year ago, a saltwater disposal pipeline owned by Zenergy Inc. of Tulsa, Okla., ruptured, spilling nearly 1 million gallons of salty water in northwestern North Dakota. Fewless said it could take years to clean up the spill, which killed creek life and forced ranchers to move their cattle.