Contribution of polycyclic aromatic compounds to the carcinogenicity of sidestream smoke of cigarettes evaluated by implantation into the lungs of rats.

Particles and semivolatiles from sidestream smoke of cigarettes smoked on a smoking machine were collected by a filter combination consisting of a glass fibre filter and silanized polystyrene beads. The extract of the glass fibre filter was separated by a Sephadex LH-20 column chromatography into a fraction containing non-aromatic material plus polycyclic aromatic compounds (PAC) with 2 and 3 rings and a fraction consisting of PAC with 4 and more rings. To evaluate the carcinogenicity, both fractions as well as the semivolatiles were implanted into the lungs of Osborne-Mendel rats at a dose level of one cigarette per animal and compared with three dose levels of benzo[a]pyrene (BaP). The most pronounced carcinogenic effect of the sidestream smoke (100 ng BaP per cigarette) was caused by the fraction containing polycyclic aromatic hydrocarbons (PAH) with 4 and more rings (5 carcinomas of the lungs/35 rats). This fraction represents only 3.5% by weight of the total sidestream smoke condensate. By contrast, the semivolatile material did not provoke any tumors. Only a small contribution to the total carcinogenicity (1 carcinoma of the lungs/35 rats) was observed for the fraction containing non-aromatic material and 2- and 3-ring PAHs.