The Association of Lead Exposure and Impairment of Brainstem Auditory-evoked Response and Cochlea Function

Abstract

PP-31-156 Background/Aims: On the basis of some researches, the heavy metals (including lead, mercury, and tin) may be toxic on hearing in human beings and animals. Complex exposures to lead and noise were the 2 common sources of occupational exposures in the factories. The aim of the study was to investigate the effect of occupational lead on the auditory system. Methods: We measured the auditory brainstem-evoked response and cochlea function with distortion product otoacoustic emissions (DPOAEs) that are preneural responses of the outer hair cells of the inner ear in 12 adult lead-workers and 12 age- and sex- matched persons who were not exposed to lead and noise. Results: The results showed that the auditory brainstem-evoked response latency of wave I, II, III, and III–V significantly increased in the group of lead-workers (blood lead: 36.13 ± 4.52 μg/dL), as compared with the group without lead exposure (blood lead: 4.09 ± 1.41 μg/dL). The latency of wave I, II, III, V, and interpeak latency I–III were correlated to blood lead levels. Mean DPOAEs of the lead workers were significantly different from the reference group at DP frequencies of 812, 1000, 1281, 1593, 2031, 2562, and 3187 Hz. However, the DPOAEs for the lead workers were within the normal ranges of the reference group only at 4031 Hz. Although there was a tendency for the lead workers to have diminished DPOAEs, no consistent correlation of DPOAEs with lead level was found. The prevalence of normal DPOAEs in the lead workers was up to 79%. Conclusion: We concluded that lead should be otoneural toxic, especially, in the workers exposed to lead and noise both. The hearing conservation program should enhance more for the worker exposing to both ototoxic agents.