The retention times of (S)-NNN and (R)-NNN were confirmed by analyzing standard solutions of the enantiomers, both individually and in combination. Enantiomers of the related commonly occurring TSNA N��-nitrosoanatabine (NAT) and N��-nitrosoanabasine (NAB) were also detected, but not quantified because the (R)-NAT peak coelutes with (R)-NAB sellckchem (Carmella et al., 2000). Figure 1. Chromatogram obtained upon chiral GC-TEA analysis of (S)-NNN and (R)-NNN in a tobacco sample (Camel Snus Robust). In tobacco, the percent contribution of (S)-NNN to NNN was larger than that of (R)-NNN in all product categories, and averaged 62.9��6.3% (SD) among the products analyzed here. The percentage of (S)-NNN was lower in conventional moist snuff than in novel smokeless products or in the cigarette tobacco filler (p < .

0001 for both comparisons). The absolute amount of (S)-NNN in conventional moist snuff ranged from 0.71 to 2.5 ��g/g tobacco; in novel smokeless products from 0.47 to 1.19 ��g/g tobacco; and in cigarette filler from 0.17 to 2.56 ��g/g tobacco (all values are per wet weight). The levels of (S)-NNN were lower in novel smokeless products than in conventional moist snuff or in the cigarette tobacco filler (p = .01 for both comparisons). In cigarette smoke, the contribution of (S)-NNN to NNN was similar to that in the corresponding tobacco filler and averaged 64.9% (S)-NNN (range, 51.3%�C75.9%) in all brands in Table 1. DISCUSSION NNN is a strong carcinogen present in unburned tobacco and cigarette smoke and is believed to play an important role in the esophageal and oral cancers associated with tobacco use.

Metabolic and carcinogenicity studies in laboratory animals indicate that its enantiomer (S)-NNN is more tumorigenic than (R)-NNN. Numerous studies documented the levels of NNN in various tobacco products. However, there is no information available on the enantiomeric composition of NNN in products currently marketed in the United States. We report the results of (S)-NNN analysis in a sample of conventional and novel smokeless tobacco products and in cigarettes purchased in the United States in 2010�C2012. To our knowledge, there was only one report in the literature on the levels of (S)-NNN in tobacco (Carmella et al., 2000). In that study, (S)-NNN averaged 75% of total NNN in a set of samples that included a few unidentified cigarettes and conventional smokeless tobacco.

In agreement with those results, the (S)-enantiomer of NNN predominated in all products analyzed here (Table 1). These results once again emphasize both the urgent need and the opportunity for the reduction of the levels of this potent carcinogen in tobacco products. It has been shown that NNN can be formed via Batimastat nitrosation of either nicotine or nornicotine in tobacco (Hecht, Chin, Hirota, et al., 1978; Hecht, Chin, Ornaf, et al., 1978; Mirvish, Sams, & Hecht, 1977).