Micronucleus formation induced by three polycyclic aromatic hydrocarbons in rat bone marrow and spleen erythrocytes following intratracheal instillation.

Benz[a]anthracene (BA), dibenz[a,h]anthracene (DBA) and dibenzo[a,i]pyrene (DBP) are polycyclic aromatic hydrocarbons (PAHs) found in incomplete combustion products of fossil fuels, coal tar, and other organic materials. Workers in related industries may be exposed to these chemicals by inhalation. The information related to the potential health hazards of these chemicals to the exposed workers, however, is very limited. In the present study, micronucleus (MN) formation in rat bone marrow and spleen polychromatic erythrocytes (PCEs) was determined following three intratracheal instillations within a 24-h period with either BA, DBA or DBP. Three doses with five rats per dose were used for each chemical. Bone marrow and spleen cells were harvested 24 h after the first dosing. Results showed that the order of toxicity for the three PAHs was DBP > DBA > BA. BA induced MN in a dose-related manner in both bone marrow and spleen PCEs at doses above 25 mg/kg. DBA caused significant increases in the frequencies of MN in both spleen and bone marrow PCEs at the dose of 8.5 mg/kg or higher. At 10 mg/kg, DBP significantly increased MN frequency in spleen PCEs, but the increase in bone marrow PCEs was not significantly different from the control. These results indicate that: (1) all three PAHs studied are absorbed through the respiratory tract and their genotoxic metabolites reach the bone marrow and/or spleen; (2) except for DBP which does not induce MN in the bone marrow, all three PAHs induced MN in both bone marrow and spleen PCEs; and (3) the sensitivity of the spleen to the three PAHs is comparable to or higher than that of the bone marrow.