ive been smokeing weed for a little over a year and a half and i rarely smoke tobacco. 95% of the time i dont use any water filtration. i usually use either a pipe, gravty bong, or a joint. I have never noticed any negative breating problems from weed, but if i smoke half a cig...my lungs will feel worse than they did before i smoked that cig, obviously. If weed if so bad for the lungs, i havent noticed it yet. I think that cannabis is one of the few exceptions, if not the only exception to the rule of, smokeing anything is bad for you, because cannabis is the only plant that contains thc.