30 cigarettes' worth of carcinogens? Challenge your teacher to locate one shred of evidence suggesting that cannabis-only smokers get lung cancer more than non-smokers. Make your teacher back up these arguments with credible reports from peer-reviewed medical journals. Remind the teacher that regurgitating crap from the DEA and DARE and other anti-pot groups is deliberately misinforming the students, since these groups have a clear bias in the debate. Impartial sources and real science are what counts, not scare tactics.