Experimental studies on the carcinogenicity of five nitrogen containing polycyclic aromatic compounds directly injected into rat lungs.

Using a beeswax/tricaprylin mixture as vehicle, three doses each of acridine, benz[a]acridine (BaAC), benz[c]acridine (BcAC), dibenz[a,h]-acridine (DBa,hAC) and dibenz[a,j]acridine (DBa,jAC) were injected into the lungs of 35 female Osborne-Mendel rats per group. To compare the carcinogenic potency of the heterocycles, benzo[a]pyrene (BaP) was taken as reference substance. Dose-response relationships were obtained for DBa,hAC as well as for BaP. DBa,jAC and BcAC exhibited no carcinogenic effects in the dose range from 0.1 mg to 1 mg tested in the lung implantation model. From the results presented here, it cannot be excluded that tumor development may occur when testing higher doses. BaP, however, must be considered much more potent since it revealed, by far, higher tumor incidences and diminished life times.