Susan Urbanek Linville. “The Case Against Legalizing Marijuana”. Herald-Times. May 15, 2002 – “While doses of marijuana are not fatal, long-term use may trigger secondary problems such as cancer, heart attack and accidental death. Marijuana is a plant product that contains more than 400 chemical compounds. When exposed to heat, these compounds react, subjecting the smoker to some 2,000 chemicals including hydrogen cyanide, ammonia, carbon monoxide, acetaldehyde, acetone and phenol as well as carcinogens found in tobacco smoke: benzopyrene, benzoanthracene, benzene and nitrosamine. Benzopyrene, in particular, has been implicated in lung cancer and is known to suppress a gene (P53) that governs cell growth.
It is true that no study has definitively linked marijuana smoking to lung cancer, but this is because a high percentage of marijuana smokers are also tobacco smokers and it is difficult to untangle the two effects. It is interesting to note that MAPS (Multidisciplinary Association for Psychedelic Studies) and NORML (National Organization for the Reform of Marijuana Laws) are sponsoring research to develop vaporizers to reduce the amount of tar reaching the marijuana smoker’s lungs. Their own literature (the MAPS Bulletin, Summer 1966) states: ‘marijuana tars are rich in carcinogenic compounds.'”