Hate to spoil your joy to be ignorant fool, but when I use that your claim in the google, what I found? WP article with 161 references. It seem to me that there is lot of studies about the matter, and your claim is bullshit. It causes lot of long term damages, and not only in your lungs. In fact, there isn't any kind of smoke which doesn't make damages in your lungs, so claims like yours is plain and simple just stupid.
http://en.wikipedia.org/wiki/Long-term_effects_of_cannabis
DID YOU EVEN READ YOUR OWN LINK?! SRS QUESTION.
"Although cannabis smoke contains many of the same carcinogens as tobacco smoke,[77] current scientific data supports the possibility that cannabis smoking may not induce cancer.[78] Of the various methods of cannabis consumption, smoking is considered the most harmful; the inhalation of smoke from organic materials can cause various health problems (e.g., coughing and sputum). Isoprenes help to modulate and slow down reaction rates, contributing to the significantly differing qualities of partial combustion products from various sources.[79][80] Compared to tobacco much less cannabis material in weight is burned, with the average hand rolled cigarette at about 1 gram, tobacco or cannabis. Commercial cigarettes have numerous additives, many of which modify combustion in such a way to create a very consistent aerosol at any given air flow rate, perhaps to maximize nicotine delivery/bio-availability, and thus reduce total amount of smoke consumed to nicotine crossing the blood brain barrier. A relative abundance of terpenes and other higher molecular weight, adhesive molecules results in a smoke with higher mean particle size, as well as a corresponding higher deposition rate of particulate matter. This means more is deposited on the bronchioles, and larger airways, which the lungs can clear easier, as less of the very fine, highly toxic amorphous particles reach the delicate alveoli. Cilia cannot "sweep" up the combustion products effectively. Subjective lung irritation not based upon the amount of matter crossing the semipermeable gas exchange surfaces deep in the lungs, rather the primary factor is amount of matter which adheres to motile cilium. This also contributes to a noted expectorant effect of any smoke to some extent, due to the defense system the mucus membranes in the lungs possess. The study concluded: "A significant interaction revealed that the impact of a vaporizer was larger as the amount of cannabis used increased. These data suggest that the safety of cannabis can increase with the use of a vaporizer. Regular users of joints, blunts, pipes, and water pipes might decrease respiratory symptoms by switching to a vaporizer".[81] Another study found vaporizers to be "a safe and effective cannabinoid delivery system."[82][83]
In a 20-year study of 5,000 young adults, researchers found that, unlike tobacco use, smoking cannabis once a week or a bit more doesn't harm the lungs, with less clear results regarding heavy users due to a lack of very heavy users in the study. In fact, the study found that occasional cannabis use actually increases both lung capacity and volume over the years, possibly because cannabis smokers often take deep breaths, which exercises lung tissue. The correlation only decreased after the equivalent of about ten years of smoking cannabis once a day. Only lung volume and capacity were examined, not throat irritation, coughing, or lung cancer.[84]"
