EFFECTS OF LOW CONCENTRATIONS OF BENZENE ON MOUSE HEMATOPOIETIC-CELLSIN-VIVO - A PRELIMINARY-REPORT

Evaluation of benzene-induced hematotoxicity following exposure to low concentrations is important for understanding mechanisms of toxicity and determining the dose response at benzene levels close to the curre nt occupational exposure limit (1 ppm). Male B6C3F1 mice were exposed to O, 1, 10, 100, or 200 ppm benzene by inhalation for 6 hr/day, 5 day s/week for 1, 2, 4, or 8 weeks. At each sampling time, we evaluated pr imitive and committed progenitor cells, differentiating and maturing l ineage-specific cells, and stromal cells in the bone marrow; T and B l ymphocytes of the spleen and thymus; micronucleated reticulocytes and erythrocytes; and standard blood parameters. At 100 and 200 ppm benzen e, there were rapid and significant reductions in number of reticulocy tes in the blood, B lymphocytes in the bone marrow and spleen, and an increased frequency of micronucleated reticulocytes in the bone marrow . At 10 ppm, the only parameter affected was a transient reduction in the number of splenic B lymphocytes. There were no significant effects induced by 1 ppm benzene in this study. The present study suggests nu mbers of B lymphocytes and maturing erythrocytes, and frequency of mic ronucleated reticulocytes are sensitive indicators of benzene-induced hematotoxicity and will be useful in further investigation of the hema totoxicity induced by 10 to 100 ppm benzene.