I have a book on this.. I'll quote directly from it

"Moderate smoking of marijuana appears to pose minimal dangers to the lungs. Like tobacco smoke, marijuana smoke contains a number of irritants and carcinogens. But marijuana users typically inhale much less smoke. As a result, the risk of serious lung damage should be lower in marijuana smokers. There have been no reports of lung cancer related solely to marjuana. HOWEVER, because researchers have foun precancerous changes in cells taken from the lungs of heavy marijuana smokers, the possibilty of lung cancer from marijuana cannot be ruled out. Unlinke heavy tobacco smokers, heavy marijuana smokers exhibit no obstruction of the lung's small airways. This indicates that people will not develop emphysema from smoking marijuana. "

- Marijuana Myths Marijauna Facts, a review of the scientific evidence. by Lynn Zimmer, Ph.D and John P. Morgan, M.D
BabyFacedAbortion Reviewed by BabyFacedAbortion on . dont' worry too much about lung cancer. I realise alot of the smokers here and other places are concerned with lung cancer. Afterall inhaling any combusted plant matter into your lungs is unhealthy. But unhealthy does not mean it will cause cellular DNA mutations necessary to produce abnormal cell growth. We really don't know what causes cancer in this case but it sure isn't tar. If we understand that cancer is an actual DNA mutation of the cell then it becomes clear that for cacer to occur there must be something present in the Rating: 5