Fact: It's true that marijuana smoke, like tobacco smoke, contains carcinogens. But even hardcore pot smokers typically consume much less pot than tobacco smokers do cigarettes, probably not enough to cause cancer. A 2006 UCLA study concluded that even heavy marijuana use does not lead to lung cancer. "We hypothesized that there would be a positive association between marijuana use and lung cancer, and that the association would be more positive with heavier use," said the study's lead author. "What we found instead was no association at all, and even a suggestion of some protective effect." This and other studies suggest that pot can actually inhibit the growth of cancerous tumors. Finally, what risks there are involve smoking, and there are other ways to consume marijuana.