They've proved that a few years ago that said smoking pot is worse on the lungs that cigarettes.
There were other reports about the fine airways in the lungs, but I can't find them right now. A lot of questions have been raised about the study you brought up. I think it is safe to say that a lot more research needs to be done before stating categorically that smoking pot is bad for you or what the effects on the body are. It's too bad we can't study it in this country so much, but we have some ridiculous laws about all that.