OBJECTIVETo investigate the carcinogenic and mutagenic mechanism of bitumen fume.

METHODSThe experimental mice were forced to inhale the bitumen fume at different exposure level (55 mg/m(3), 165 mg/m(3)) and in different time (30 days, 60 days). The pathological changes of the lung tissue in mice were observed with H.E staining. The content of the DNA in the lung tissue of mice and the cell circles were determined with flow cytometry.

RESULTSThe lesion of the lung tissue in mice comprised the atypical hyperplasia of different levels and the carcinoma in situ with the increase of the containment time and dosage; the cycle index was changed: the number of the G 1 phase cells was decreased, the S phase was retarded, the cells entering the G 2/S phase were decreased, the cell proliferation index (P I) was increased and the heteroploid DNA index (DI) was increased (P < 0.05). The cell index in the 55 mg/m(3) group and the 165 mg/m(3) group was higher than that in the control group when the containment time was same. The heteroploid DNA index (DI) in the 55 mg/m(3) group was significantly higher than that in the 165 mg/m(3) group (P < 0.05 or P < 0.01). When the containment dosage was same, the DI in the 60 days treatment group (1.16 +/- 1.51 x 10(-2), 1.20 +/- 2.3 x 10(-2)) was all significantly higher than those in the 30 days treatment group (1.14 +/- 8.8 x 10(-2), 1.16 +/- 1.47 x 10(-2)) (P < 0.05).

CONCLUSIONThe precancerous lesion in the lung tissue of the mice induced by the bitumen fume may be related with the changes of the cell cycle.