Studies in tobacco carcinogenesis.

The vapour phase of freshly generated cigarette mainstream smoke, of sidestream smoke and of environmental tobacco smoke was analysed for such tumorigenic agents as benzene, 1,3-butadiene and acrolein with a newly developed, highly sensitive gas chromatography-mass selective detection method. The major carcinogen in tobacco smoke, catechol, was studied in regard to its specific action on the metabolism of benzo[a]pyrene in mouse lung and mouse skin. The major tobacco-specific carcinogens in tobacco and its smoke are the nicotine-derived N-nitrosamines, N'-nitrosonornicotine and 4-(nitroso-methylamino)-1-(3-pyridyl)-1-butanone. A third nitrosamine that can be formed in vitro by nitrosation of nicotine is 1-(nitrosomethylamino)-1-(3-pyridyl)butylaldehyde. This aldehyde is not present in tobacco products, but its noncarcinogenic oxidation product, 4-(nitrosomethylamino)-1-(3-pyridyl)butyric acid, was found in tobacco and can be formed from the major nicotine metabolite, cotinine. It is also likely that this acid can be formed by endogenous reactions.