Dr. Donald Tashkin, professor emeritus of medicine at UCLA, has being researching the effects of marijuana smoke in the lungs for over 30 years and has come to the conclusion that marijuana is less harmful to your lungs than tobacco. The tar in marijuana, similar to tobacco, has cancer-causing chemicals, he says, but it turns out that marijuana users actually have less risk of lung cancer than a tobacco smoker or non-smoker. COPD, another illness caused by tobacco smoke has not shown to be cause by marijuana smoke.
But, he says, “Through my studies, we failed to find any positive association.” Instead, “the association would be negative, between lung cancer and the use of marijuana. The likelihood is, that despite the fact that marijuana smoke contains carcinogens, we don’t see the same heightened risks of cancers that we see in tobacco.”