Pollutants in Alberta's Athabasca River system are natural, the joint oilsands industry-government group responsible for monitoring the region's water maintains.

"We do find elevated levels of things in [our] study area," said Fred Kuzmic on behalf of the Regional Aquatics Monitoring Program (RAMP), a joint industry-government group. "Those are generally associated with naturally occurring compounds."

Kuzmic, who heads a research and reclamation team for Shell Albian Sands, was responding to a study led by biologists Erin Kelly and David Schindler of the University of Alberta. Those findings, published Tuesday in the Proceedings of the National Academy of Sciences, linked high levels of toxins to oilsands mining.

Concentrations of pollutants like mercury and cadmium were higher downstream from oilsands mining than upstream, the researchers found. They did not find the same difference between water upstream and downstream of undeveloped oilsands deposits.

Kuzmic said one would expect water downstream of oilsands mining to contain more toxins.

"The Athabasca River and many of its tributaries in this particular region run through oilsands deposits," he said. "It's not surprising that we would see these elevated concentrations downstream from oilsands operations because oilsands operations are operating where these oilsands exist."

He said it's not clear that the higher levels are associated with human activity.

"I think it's difficult to try and tease that out."

Kelly and Schindler's paper said their results confirm "serious defects" in the monitoring program, as the ability to distinguish the sources of contaminants is "essential" to control the potential impact of pollutants on human health. In an interview with CBC News Tuesday, Schindler called for Environment Canada to take over water monitoring in the Athabasca River system.

Kuzmic said RAMP already works with Environment Canada and is willing to see how they can work together more co-operatively.

"As for responsibility, I don't know if I'd want them to take the whole program over," he said. "It's great now as a multi-stakeholder agency with different views represented and decisions made from a number of different viewpoints."

He added that RAMP is currently in the middle of a peer review process to see how it can use new technologies or sampling techniques.

"We're trying to improve the program as we go," Kuzmic said.