Investigations on the origin of tobacco-specific nitrosamines in mainstream smoke of cigarettes

Introduction:
This text is a scientific article published in Carcinogenesis in 1990, investigating the origin of tobacco-specific nitrosamines (TSNa) in mainstream smoke of cigarettes. The authors, Sophia Fischer, Bertold Spiegelhalder, Josef Eisenbarth, and Rudolf Preussmann, aimed to determine whether the addition of nitrosamine precursors to tobacco prior to smoking changed the mainstream smoke concentrations of TSNa, and whether pyrosynthesis of TSNa occurred during the smoking procedure. They also calculated the mainstream smoke/tobacco ratios for NNN and NNK and related them to the nitrate and nicotine level in commercial cigarettes.

Key Points:

* The addition of nitrate and nicotine to tobacco prior to smoking did not change the mainstream smoke concentrations of W-nitrosonornicotine (NNN) and 4-(methyl-nitrosamino)-1-(3-pyridyl)-1-butanone (NNK), whereas the mainstream smoke concentration of N'-nitrosoanabasine (NaB) and N'-nitrosoanatabine (NaT) increased after spiking the cigarettes with nitrate.
* The mainstream smoke/tobacco ratios for NNN and NNK were constant and did not depend on the nicotine level or on the nitrate level of the tobacco, except for NNK in nitrate-rich dark tobacco type cigarettes.
* The transfer rates of NNN and NNK were calculated and corrected for ventilation and cigarette length. The transfer rates for nonfilter cigarettes were 23% or 34%, and for filter cigarettes, 13% and 23%, respectively.
* The mainstream smoke/tobacco ratios for NNN and NNK were constant over the whole length of the cigarettes, except for NNK in dark tobacco type cigarettes.
* The results suggest that pyrosynthesis of NNN did not occur and that it is very unlikely for NNK, at least for lower nitrate levels. Therefore, the TSNa burden of smokers is predominantly influenced by the amount of preformed NNN and NNK in tobacco.

Main Message:
This study provides evidence that the transfer of preformed TSNa in tobacco is the primary source of TSNa in mainstream smoke, and pyrosynthesis during the smoking procedure is unlikely. The study also highlights the importance of reducing the amount of preformed TSNa in tobacco as a means of reducing the TSNa burden of smokers. The findings have implications for tobacco control policies and regulations aimed at reducing exposure to harmful tobacco smoke constituents.

Fischer, Sophia, Bertold Spiegelhalder, Josef Eisenbarth, and Rudolf Preussmann. “Investigations on the Origin of Tobacco-Specific Nitrosamines in Mainstream Smoke of Cigarettes.” Carcinogenesis 11, no. 5 (1990): 723–30.