[sixpakistan]

The study's comparing 2-3 joints per day (max) to 40 cigarettes a day. Of course, noone smokes 40 joints a day, but pretty much any smoke inhalation is horrible for your lungs.

The upside of marijuana is that it's not grown commercially, so a bunch of poisons aren't added to it (the best pot growers will at worst use organic insecticide).

You could probably potentially mitigate the risk of tobacco by smoking something like Sherman MCDs or American Spirits (all natural tobacco). Or for that matter, a pipe - pipe smokers have actually been shown to have longer lives than non-pipe smokers.. though I don't think this has anything to do with pipe smoking, and I think they'd live longer if they didn't smoke pipes.

Also, marijuana has a lot of other debilitating effects aside from lung damage (lower sperm count, hippocampus damage, etc). So do cigarettes, of course.