Tobacco-specific nitrosamines in commercial cigarettes: possibilities for reducing exposure.

Tobacco-specific nitrosamines (TSNA) are powerful carcinogens found in tobacco and tobacco smoke in relatively high concentrations. Tar delivery, which is generally accepted as an index for the carcinogenic potential of cigarette smoke, must be declared in most European countries. In this investigation of more than 170 types of commercial cigarettes from several European countries and the USA, no correlation was observed between tar delivery and mainstream smoke concentration of N'-nitrosonornicotine (NNN) and 4-(N-nitrosomethylamino)-1-(3-pyridyl)-1-butanone (NNK). Therefore, although crucial, tar delivery alone is not a sufficient index for the carcinogenic potential of cigarette smoke. It is proposed that TSNA concentrations be determined for characterization of the carcinogenic potential of cigarettes with low and ultra-low tar yields and that these be declared by an additional and adequate parameter. The mainstream smoke concentrations of NNN and NNK are given by the amounts of preformed compounds in tobacco, which is dependent on the nitrate content of the tobacco and the tobacco type. A further important determinant of the exposure of smokers to TSNA is the total volume drawn through a cigarette while smoking, which is dependent on puff volume and puff frequency and which directly influences TSNA transfer. Smokers inhale higher volumes when smoking low-nicotine cigarettes, so that low NNN:nicotine and NNK:nicotine ratios result in decreased exposure to TSNA. Reduction of exposure to TSNA can be achieved by selecting tobaccos with low levels of preformed TSNA (low nitrate content, small amounts of burley tobaccos and stems) and by manufacturing cigarettes with low NNN:nicotine and NNK:nicotine ratios.