Cuts weren't found either in the dust containing XXX or in the dust containing YYY.
Pastabos apie vertimą
I think that here "to cut" means "to mix a substance with another substance". The fact that there aren't "cuts" in these chemicals means that they have not been mixed with anything else. In Italian we use this word applied to drugs (you can read something here: http://en.wikipedia.org/wiki/Cutting_agent).
I think that the explanation about "Cutting agent" is the one I was looking for. I It is not exactly 'traces' but this explantion helped me. I don't need any more. Thanks!