INHALATION STUDIES OF THE GENOTOXICITY OF TRICHLOROETHYLENE TO RODENTS

Trichloroethylene (TCE) (CAS No. 79-01-6) is an industrial solvent use d in degreasing, dry cleaning, and numerous other medical and industri al processes. Controlled inhalation studies were performed using male C57BL/6 mice and CD rats to determine if TCE can induce cytogenetic da mage in vivo. Animals were exposed in groups of five to target concent rations of either 0, 5, 500, or 5000 ppm TCE for 6 h. Tissue samples w ere taken between 18 and 19 h post exposure. Peripheral blood lymphocy tes (PBLs) in rats and splenocytes in mice were cultured and analyzed for the induction of sister-chromatid exchanges, chromosome aberration s, and micronuclei (MN) in cytochalasin B-blocked binucleated cells. B one marrow polychromatic erythrocytes (PCEs) were analyzed for MN. The only positive response observed was for MN in rat bone marrow PCEs. T CE caused a statistically significant increase in MN at all concentrat ions, inducing an approximate fourfold increase over control levels at 5000 ppm. TCE was also cytotoxic in rats, causing a significant conce ntration-related decrease in the ratio of PCEs/normochromatic erythroc ytes. This study indicates that there may be species-specific cytogene tic effects attributed to TCE inhalation exposure. In follow-up studie s, CD rats were exposed for 6 h/day over 4 consecutive days to either 0, 5, 50, or 500 ppm TCE. No statistically significant concentration-r elated increases in cytogenetic damage were observed. While the MN fre quencies in the 4-day study were comparable to those at the equivalent concentrations in the 1-day study, they were not significantly elevat ed due to an unusually high MN frequency in the controls. A subsequent replication of the 1-day 5000 ppm TCE exposure with rats again showed a highly significant increase in MN frequencies compared to concurren t controls.