Haemopoietic stem cells in mice chronically exposed to styrene vapour

Reduction of benzene toxicity by toluene

BDF1 mice were exposed in inhalation chambers to benzene (900 ppm, 300 ppm) and/or toluene (500 ppm, 250 ppm) 6 hr per day, 5 days per week, for up to 8 weeks. Benzene alone induced a slight anemia after 4 and 8 weeks and a reduction of BFU-E and CFU-E numbers in the marrow. The coexposure to toluene reduced the degree of anemia. These results confirm previous studies where toluene was found to reduce benzene toxicity. This protective effect was most pronounced when DNA damage was studied in peripheral blood cells, bone marrow, and liver using the single cell gel (SCG) assay. With benzene alone, either with 300 or 900 ppm, a significant increase in DNA damage was detected in cells sampled from all three organs. Toluene alone did not induce a significant increase in DNA damage. The coexposure of benzene and toluene reduced the extent of DNA damage to about 50% of benzene alone. This result is considered a clear indication for a protective effect of toluene on the genetic toxicity of benzene.

Hematological toxicity of tetrachloroethylene in mice

Female C57/BL/6 x DBA/2 hybrid mice were exposed to two concentrations (270 and 135 ppm) of tetrachloroethylene (PER) in inhalation chambers for 6 h/day, 5 days per week, up to 11.5 weeks (270 ppm) and 7.5 weeks (135 ppm), respectively, followed by a 3-week exposure-free period. In the peripheral blood a reduction of lymphocytes/monocytes and of neutrophils was observed with an almost complete regeneration in the exposure-free period. A reticulocytosis during and also after the exposure indicated a compensatory reaction in the erythroid cell system. Bone marrow pluripotent stem cells (CFU-S) were not affected up to 7.5 weeks. Erythroid committed cells (BFU-E and CFU-E) did react, with a reduction of CFU-E numbers at 7.5 and 11.5 weeks. A slight reduction of CFU-C numbers at 7.5 weeks indicated, in accordance with the peripheral blood data, a disturbance of the granulocytic cell series as well.