A bright and a Burley tobacco were grown at four fertilization rates and each tobacco was then both flue-cured and air-cured. Levels of alkaloids and nitrosamines were found to increase with increasing fertilization levels. Levels of alkaloids, N-nitrosonornicotine (NNN), and other tobacco-specific nitrosamines (TSNA) were consistently higher in the Burley tobacco than in the bright tobacco, regardless of curing method. In comparing the effects of curing, it was found that NNN and total TSNA levels were higher in the midrib than in the lamina of the air-cured samples, while just the opposite was found for the flue-cured samples. Flue-curing bright tobacco produced three times the level of TSNA vs air-curing the same tobacco. On the other hand, flue-curing Burley tobacco reduced the alkaloids, but greatly increased the TSNA in the lamina. As midribs from the air-cured Burley leaves had three times the TSNA concentration of the lamina, the use of air-cured midribs in tobacco products should be avoided. It was concluded that lower fertilization levels and careful manipulations of curing parameters could lower nitrosamine levels in cured tobacco.
A.P. Swain, F.G. Bock, J.E. Cooper, W.J. Chamberlain, E.D. Strange, L. Lakritz, R.L. Stedman and I. Schmeltz
Cigarette smoke condensate (CSC) was fractionated for biological experiments examining tumorigenic activity on mouse skin. The active fractions were combined in various ways in order to determine their additive effects. Steam distillation of the ether-soluble weak acid fraction (WAE) provided two subfractions which were submitted for assay separately and in combination. The totaI neutral fraction was separated by solvent partition between cyclohexane and 80 % aqueous methanol as in a previous study and each subfraction was further fractionated: the part insoluble in aqueous methanol (MIN) was subjected to a 200-tube countercurrent distribution between cyclohexane and nitromethane to provide five subfractions; and the part soluble in aqueous methanol (MSN) was separated into two subfractions by partition between nitromethane and carbon disulfide. Reconstituted MIN and MSN fractions were prepared by recombination of their subfractions. Finally, the total neutrals were separated into five fractions by chromatography on silicic acid as done in a previous study in order to obtain the active fraction eluted by methanol and soluble in aqueous methanol (MMW). This was subjected to gel filtration using benzene as eluant. The five subfractions of MMW were submitted for assay separately and in combination. In addition to these fractions, four combinations of active fractions were prepared: WAE with MMW; WAE with the polynuclear aromatic hydrocarbon (PAH) containing neutral fractions; MMW with the PAH-containing neutrals, i. e. all of the active neutral fractions; and WAE with MMW and the PAH-containing neutrals. The last comprises essentially all of the fractions shown to possess tumorigenic activity for mouseback skin in previous work.