Identification of polynuclear aromatic hydrocarbons in cigarette smoke and their importance as tumorigens.

Fraction F20, which in other studies was the most tumorigenic neutral fraction of cigarette smoke condensate (CSC), was separated by gel filtration chromatography into refined subfractions for identification of the polynuclear aromatic hydrocarbons (PAH) and for bioassay on mouse skin. Several hundred PAH were positively identified. Subfraction F55. containing most of the carcinogenic PAH as well as numerous unidentified components, was almost as tumorigenic to 7,12-dimethylbenze[a]anthracene (DMBA)-pretreated female outbred CD-1 mice as was F20. When F55 was separated into two parts, the first containing unidentified material (F55A) and the second containing the PAH (F55B), neither was significantly tumorigenic. F55B, combined with two other active fractions from the neutral and the acidic portions of CSC, exhibited a synergistic tumorigenic effect on DMBA-pretreated mice. The results supported the concept that the PAH in cigarette smoke must interact with other components in order to exert a tumorigenic effect.