DNA content of cultured mammalian cells exposed to smoke and smoke fractions from cigarettes containing tobacco or NSM, a tobacco substitute.

The effects of smoke and smoke fractions from tobacco and a substitute smoking material (NSM) on the DNA content of mammaliam cells in culture were measured. Tobacco smoke caused significant (P less than 0.001) changes in the DNA content of all the mammalian cells exposed compared with controls. NSM smoke did not have a significant effect on the DNA content of the exposed cells (P less than 0.95). Smoke from blends of NSM and tobacco caused changes in DNA content in proportion to the amount of tobacco in the mixtures. Condensate from cigarettes containing tobacco or blends of tobacco and NSM caused significant (P less than 0.001) changes in DNA content of mammalian cell populations in culture, whereas equal weights of condensate from NSM alone or NSM containing nicotine did not cause significant changes (P less than 0.05). NSM produces 28% of the weight of condensate per cigarette in comparison with tabacco and would, therefore, be expected to be far less biologically active than tobacco. Filtered smoke from cigarettes containing tobacco caused significant (P less than 0.001) changes in the DNA content of mammalian cells in culture. These changes were quantitatively similar to those caused by whole smoke suggesting that the gas phase of cigarette smoke is biologically more reactive than the particulate phase. The filtered smoke from the substitute smoking material NSM did not cause significant (P less than 0.95) changes in DNA content of cultured mammalian cells. Filtered smoke from blends of NSM and tobacco caused changes in DNA content in proportion to the amount of tobacco in the mixture.