For sure, marijuana smoke contains a number of irritants and carcinogens, just like cigarettes. But, there have been no reports of lung cancer related solely to marijuana, and in a large study presented to the American Thoracic Society in 2006, even heavy users of smoked marijuana were found not to have any increased risk of lung cancer. Also, Unlike heavy tobacco smokers, heavy marijuana smokers exhibit no obstruction of the lung's small airway. That indicates that people will not develop emphysema from smoking marijuana.
I'm not saying there aren't some negative consequences to marijuana use - only that I think they are largely exaggerated. A real solution to carcinogens is to buy a vaporizer. :D
And, I think it's really kinda bizarre they are keeping it so top-secret(switching to P:M talk - keep up). Come on, now - it's a game mod not a ****ing nuclear weapon. I guess they are trying to wait until it is largely playable, and avoid another Brawl+, but it seems more beneficial to release an alpha and let everyone rather play around with it and test it. But whatev, wishful thinking. D: