Neurotoxicologic Examination of Rats Exposed to 1,1,2,2-Tetrachloroethylene (Perchloroethylene) Vapor for 13 Weeks

Large evoked potential and EEG changes occurred in a pilot study in Fischer 344 rats during exposure to 800 ppm of 1,1,2,2-tetrachloroethylene [perchloroethylene (Perc)], a cleaning solvent with anesthetic properties. In the main study, rats were evaluated for persistent nervous system effects the week following exposure to 0, 50, 200, or 800 ppm Perc for 6 h/day, 5 days/week, for 13 weeks. The only effect related to treatment was in the flash evoked potential (FEP-V), recorded from the visual cortex. The longer latency potentials (N3) of the FEP-V had a greater amplitude in the 800 ppm Perc group. The FEP-Vs were of normal shape and latency. Although mild neurotoxicity could not be ruled out completely, amplitude changes in N3 can occur for a variety of psychophysiological reasons other than neurotoxicity. Consequently, as a stand-alone finding, the toxicologic significance of the larger FEP in the 800 ppm exposure group was unknown. Other data did not support a diagnosis of neurotoxicity. No treatment-related alterations were noted in expanded clinical observations, in the FEP recorded from the cerebellum (as opposed to visual cortex FEP-V), or in auditory, somatosensory, or caudal nerve evoked potentials. No treatment-related lesions were noted during histopathologic examination of eyes, optic nerves, optic tract, or multiple sections of brain, spinal cord, peripheral nerves, or limb muscles. The no-observed-effect-level (NOEL) was 200 ppm, based on increased amplitude of the longer latency potentials of the FEP at 800 ppm.