Salty oil well wastewater dumped by the state for decades on North Dakota roads as a deicer has not hurt water or vegetation along roadsides, the state Health Department says.

But health officials are recommending that the ban on the oil well wastewater continue until more studies are done. State Transportation Department Director Francis Ziegler said the practice of using the oil waste, which was halted in February, may be banned indefinitely.

"It all depends," Ziegler said Wednesday. "We will be working with the Health Department."

The Transportation Department had been using the oil well wastewater, 10 times saltier than sea water, to melt ice and snow on North Dakota roads - mostly in the Dickinson area - since 1963. The practice stopped after the Associated Press raised questions about it. Some health officials had never heard of the practice before then.

Health and transportation officials released a report to the state Industrial Commission on Wednesday about the effects of using oil field brine. The commission's members are Gov. John Hoeven, Attorney General Wayne Stenehjem and Agriculture Commissioner Roger Johnson.

"We didn't see a significant impact," said Dave Glatt, director of the state Health Department's environmental health section.

Glatt said samples of oil wastewater were taken from 10 well sites, where pollutants "varied from well to well."

Samples also were analyzed alongside four highways in western and north central North Dakota where the wastewater had been used to melt ice and snow, Glatt said. Two highways where the state has used rock salt were studied for a comparison. The sampling was done in July.

Glatt said three states - Michigan, Pennsylvania and Ohio - use oil field wastewater as a deicer on roads but have rules that regulate its use.

North Dakota would have to adopt similar rules and identify wastewater safe enough to apply to roads, and determine the rate, before resuming its use, Glatt said.

The Sierra Club and the Dakota Resource Council, a Dickinson-based environmental and landowner group, say the state's practice of spraying the briny wastewater on roads was illegal and questioned the thoroughness of the state's study.

Representatives from both groups attended the state Industrial Commission meeting on Wednesday.

"They're trying to find a way out of this problem," said Wayde Schafer, a North Dakota spokesman for the Sierra Club. "Basically, they were putting pollution on our public roadways and that's illegal."

Transportation officials said tens of thousands of gallons of the oil well wastewater were used on North Dakota roads each year. The state got it free from oil companies, which otherwise would have to pay to dispose of it in underground wells.

Ziegler said his agency will spend between $200,000 and $400,000 this year on rock salt and other commercial deicers to replace the free briny wastewater. He said it would be too expensive to transform oil well wastewater into a commercial-grade rock salt.