Yes. In fact, you'll find that in some of the papers I have here that were done looking at slimy sculpin in a couple of these rivers...we suspect those may be impacts on fish that are occurring as a result of the natural levels of materials that are present in the system. I can show you streams up there that look as if the bottom of the thing has been paved. It looks as if it's been paved; it's eroded bitumen with the stream running over it. The trick is that the contaminants you see that are associated with oil sands exploration and exploitation are exactly the same contaminants that are there as a result of natural weathering.
So the question arises whether the naturally occurring compounds are having an effect. We have some indications that in some places they may be high enough that they are. Now the beauty of that, of course, is that it tells you what to look for when you're looking for an anthropogenic impact.