The influence of benzene on the erythroid cell system in mice.

Female BDF1 mice were exposed up to 8 weeks to airborne concentrations of 100, 300, and 900 ppm of benzene, 6 h/day, 5 days/week. The erythropoietic cell compartment in the bone marrow and the peripheral blood was studied using the erythroid burst-forming unit (BFU-E) and erythroid colony-forming unit (CFU-E) assays, the incorporation of 59Fe, and standard methods. In the peripheral blood only a slight anemia was observed. In the bone marrow, however, a considerable decrease of CFU-E numbers was seen, the CFU-E being more depressed than the BFU-E numbers. In bone marrow smears a variable content of erythroblasts was found. The 59Fe kinetics showed an enhanced turnover within the erythron, suggesting the decrease in transit time as a compensating mechanism for the low CFU-E numbers. After 4 weeks of exposure to all benzene concentrations, greater than 17 days in benzene-free atmosphere are needed for a complete recovery of BFU-E and CFU-E compartment sizes.