Tobacco-specific nitrosamines

Tobacco-specific nitrosamines (TSNAs) comprise one of the most important groups of carcinogens in tobacco products, particularly cigarettes and fermented dipping snuff.

These nitrosamine carcinogens are formed from nicotine and related compounds by a nitrosation reaction that occurs during the curing and processing of tobacco. They are called tobacco-specific nitrosamines because they are found only in tobacco products, and possibly in some other nicotine-containing products. The tobacco-specific nitrosamines are present in cigarette smoke and to a lesser degree in "smokeless" tobacco products such as dipping tobacco and chewing tobacco; additional information has shown that trace amounts of NNN and NNK have been detected in e-cigarettes. They are present in trace amounts in snus, a Swedish style snuff that is not fermented (a type of curing) and is pasteurized. They are among the most important carcinogens in cigarette smoke, along with combustion products and other carcinogens.

Among the tobacco-specific nitrosamines, nicotine-derived nitrosamine ketone (NNK) and N-nitrosonornicotine (NNN) are the most carcinogenic. Others include N′-nitrosoanatabine (NAT) and N-nitrosoanabasine (NAB). NNK and its metabolite 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) are potent systemic lung carcinogens in rats. Tumors of the nasal cavity, liver, and pancreas are also observed in NNK- or NNAL-treated rats. NNN is an effective esophageal carcinogen in the rat, and induces respiratory tract tumors in mice, hamsters, and mink. A mixture of NNK and NNN caused oral tumors when swabbed in the rat oral cavity. Thus, considerable evidence supports the role of tobacco-specific nitrosamines as important causative factors for cancers of the lung, pancreas, esophagus, and oral cavity in people who use tobacco products.

...
Wikipedia