For example, federally funded research at the University ofCalifornia, Los Angeles compared the lifetime risk of lungcancer among more than 2,000 long-term marijuana smokers,tobacco smokers, and non-smokers. Other studies indicate that cannabis smoke and tobaccosmoke aren't equally carcinogenic and that subjects whoexclusively smoke cannabis have less exposure to harmfultoxicants and carcinogens than tobacco smokers.