Commentary on the regulatory implications of noise-induced cochlear neuropathy

Objective: A discussion on whether recent research on noise-induced cochlear neuropathy in rodents justifies changes in current regulation of occupational noise exposure. Design: Informal literature review and commentary, relying on literature found in the authors’ files. No formal literature search was performed. Study sample: Published literature on temporary threshold shift (TTS) and cochlear pathology, in humans and experimental animals, as well as the regulations of the US Occupational Safety and Health Administration (OSHA). Results: Humans are less susceptible to TTS, and probably to cochlear neuropathy, than rodents. After correcting for inter-species audiometric differences (but not for differences in susceptibility), exposures that caused cochlear neuropathy in rodents already exceed OSHA limits. Those exposures also caused “pathological TTS” (requiring more than 24 h to recover), which does not appear to occur with human broadband noise exposure permissible under OSHA. Conclusion: It would be premature to conclude that noise exposures permissible under OSHA can cause cochlear neuropathy in humans.