Just a guess, but I bet almost all the trees we buy are from tree farms which must practice good forestry if they are to stay in business. And while I don't drink the fear mongerer's kool-aid, I bet more 'toxins' are produced in the manufacture of artificial trees.
My sister and I were having this debate the other day. . . .which is better for the environment. I say the fresh tree. The Christmas tree was planted for this particular purpose and I imagine the farmer is planting another one in it's place. And the artificial tree is to end up in a land fill eventually -- at least the box that it was delivered in will. Don't get me wrong, I would LOVE an artificial tree (My husband won't even consider it!) And there are a lot of reasons to justify getting one. . . . I just don't think you can say that it's the GREEN way to go.