Acute toxicity of benzene inhalation to hemopoietic precursor cells

When BDF1 mice were submitted to inhalation of benzene vapors (4680 ppm) for 8 hr, a significant depletion in bone marrow colony forming cells (CFC) was observed in cultures in vitro assayed 1 day after drug inhalation; however, femoral CFC returned to steady state values by Day 7. The return of femoral CFC values was not due to an increase in bone marrow cellularity. Although spleen cellularity increased significantly by Days 4 and 7, the splenic CFC value was not significantly different from controls. This acute toxicity to femoral CFC was enhanced by multiple sessions of benzene inhalation over a period of 3 and 3.5 days. After three and one-half 8-hr sessions of benzene vapor inhalation (4680 ppm), CFC content was dramatically reduced (13% of controls), in addition to significantly lowered values for body and spleen weights and bone marrow cellularity. Splenic colony forming unit (CFU) formation in irradiated mice which received bone marrow cells from benzene-treated mice corresponded well with in vitro femoral CFC formation from mice treated with the identical multiple benzene inhalation regimen as the donor mice; CFU and CFC production was reduced to the same extent, about 40–45% of controls. In summary, precursor cells of the hemic cell renewal system are sensitive to benzene inhalation in mice.