Tobacco-specific nitrosamines. A multidisciplinary research area

The group of tobacco-specific nitrosamines, TSNA, includes N-nitrosonornicotine (NNN), N-nitrosoanabasine (NAB), nitrosoanatabine (NAT), and 4-methylnitrosoamino-1-(3-pyridyl)-1-butanone (NNK) as well as three less commonly encountered nitrosamines. The concentration of TSNA in tobacco and smokeless tobacco products are in the mu g/g range, while amounts in the ng range are found in the mainstream smoke from one cigarette. Because of the toxicity of some of these nitrosamines, the research on the formation of TSNA has been intense during the past decade. The results obtained show that TSNA are generated during the post-harvest processing of tobacco by nitrosation of the secondary tobacco alkaloids nornicotine, anabasine and anatabine. The tertiary alkaloid nicotine may also undergo nitrosation with formation primarily of NNN and NNK. The nitrite required is generated by microbial dissimilatory nitrate reduction. This reaction may only fake place when the cells have disintegrated due to moisture loss and the nutrients are made accessible to invading microorganisms. Possible measures to limit or inhibit the formation of TSNA in tobacco have involved modified curing experiments as well as model experiments using various naturally occurring nitrite scavengers.