EFFECTS OF ETHYLENE ON MICRONUCLEUS FORMATION IN THE BONE-MARROW OF RATS AND MICE FOLLOWING 4 WEEKS OF INHALATION EXPOSURE

Male Fischer 344 rats and male B6C3F1 mice (10/species/group) were exp osed to ethylene 6 h/day, 5 days/week, for 4 weeks. The ethylene targe t concentrations were 0, 40, 1000, and 3000 ppm. An ethylene oxide (EO ) control group for each species was exposed under the same conditions at a target concentration of 200 ppm. Bone marrow was collected appro ximately 24 h after the final exposure. Polychromatic erythrocyte (PCE ) to normochromatic erythrocyte (NCE) ratios were determined and 2000 PCE/animal were scored for the presence of micronuclei. Ethylene did n ot produce statistically significant, exposure-related increases in th e frequency of micronucleated PCE (MNPCE) in the bone marrow of either rats or mice when compared to air-exposed control animals. As expecte d, EO exposure resulted in significant increases in the frequencies of MNPCE in both species.