It's entirely possible that many people are dying from carcinogenic pesticides in cannabis. Similar to the way people die from impure cocaine, heroin, etc. Igniting and inhaling petroleum products is not going to be found to be healthy.
The secondary affects of drugs being illegal and unregulated is one of the great sins of the War on Drugs.
Commercial cannabis should be highly regulated. Look to startups and technology to bring the price of pure organic ganja down over a short few years.