MID-FREQUENCY HEARING-LOSS IN RATS FOLLOWING INHALATION EXPOSURE TO TRICHLOROETHYLENE - EVIDENCE FROM REFLEX MODIFICATION AUDIOMETRY

The present experiments were undertaken to characterize the hearing lo ss associated with 1,1,2-trichloroethylene (TCE) exposure. Adult male Long-Evans (LE) rats were exposed to TCE via inhalation (whole body) f or 6 h/day for 5 days. The concentration-effect function (0-4000 ppm) was determined 3 weeks post-exposure. Animals were tested for auditory thresholds to 4, 8, 16, 24, 32, and 40-kHz tones using reflex modific ation audiometry. In a separate experiment, the time course of effects was determined by monitoring 16-kHz thresholds prior to, 1 h followin g each of the 5 exposure days, and 5 days, 1, 2, 4, 8, and 12 weeks po st-exposure. At 14 weeks, these same animals were tested for threshold s to 0.5, 1, 2, 4, 8, 16, 24, 32, and 40-kHz tones. Results indicate e levated thresholds (hearing loss) for the 4000 ppm group at 8 and 16 k Hz of approximately 18 and 30 dB, respectively. Time-course data demon strated a rapid onset, a 20-dB loss at 16 kHz after the fifth exposure day, and a 40-dB loss by 2 weeks that persisted up to 14 weeks post-e xposure. These data demonstrate an atypical and persistent, mid-freque ncy hearing loss in rats following inhalation exposure to TCE.