May I add to Dr. Guigard's comments?
The heavy metals are extremely difficult to remove from the bitumen. They have no mobility in the ecosystem. My own personal research has been in finding ways to try to remove those metals from the oil sands system. So far we have not succeeded. It's so difficult that even in a laboratory we have not found effective ways to remove those metals and get them to mobilize. If anyone could come up with a method, we would be thrilled to use it in processing this heavy material so that the metals are not an issue.
The tailings material and the nature of the oil sands are unique compared to mining anywhere else in the world. If you hear about tailings problems in mines elsewhere in Canada, the tailings are fundamentally different for the oil sands. The contamination is organic material. It's partly biodegradable, as Dr. Guigard said, based on studies at Waterloo and Alberta. It's not things like arsenic, cyanide, nickel, or other heavy metals, which are so much of a problem with tailings elsewhere in Canada.
So it's a completely unique system. If you canoe through these rivers, which I have, you find that oil is part of the natural ecosystem in the Fort McMurray area. You go to a campsite on the Clearwater River, and you see little droplets of oil coming up out of the riverbank with naphthenic acids at low concentration. As Dr. Guigard said, the key question for the ecosystem is not whether these compounds are present, it's the concentration. It's a unique system. The Athabasca River has an amazing capacity to degrade oil. You can watch little oil slicks form and then disappear as the organisms in the water degrade the material.
The load is the key question. How much release, how much concentration, and how much of that material will go downstream to communities like Fort Chipewyan? That's the question for which, as Dr. Guigard said, we don't yet have the answers.