Cigarette smoke has a number of carcinogens in it. While nicotine itself is not known to be a carcinogen [0] it does inhibit programmed cell death [1]. Thus,

Cigarette smoke has a number of carcinogens in it. While nicotine itself is not known to be a carcinogen [0] it does inhibit programmed cell death [1]. Thus, nicotine promotes carcinogenic activity in the lungs and in other bodily tissues. Interestingly, THC seems to have the exact opposite effect promoting programmed cell death rather than inhibiting it [2]. This may lead to a low risk of lung cancer when smoking marijuana as compared to a high risk of lung cancer when smoking cigarettes [3]. [0] http://en.wikipedia.org/wiki/Nicotine#Toxicology http://en.wikipedia.org/wiki/Nicotine#Toxicology [1] http://toxsci.oxfordjournals.org/content/79/1/1.full http://toxsci.oxfordjournals.org/content/79/1/1.full [2] http://www.jci.org/articles/view/37948#ABS http://www.jci.org/articles/view/37948#ABS [3] http://www.washingtonpost.com/wp-dyn/content/article/2006/05/25/AR2006052501729.html http://www.washingtonpost.com/wp-dyn/content/article/2006/05...