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Factors affecting laterality of standard threshold shift in occupational hearing conservation programs
T H Simpson1, D McDonald, M Stewart
1Department of Audiology, Wayne State University, Detroit, Michigan.
Ear and Hearing
|October 1, 1993
Summary
Most noise-induced hearing loss (NIHL) shifts meeting Occupational Safety and Health Administration (OSHA) criteria occur unilaterally, often influenced by initial hearing asymmetry. This challenges the assumption of symmetrical hearing damage in industrial noise exposure.
Area of Science:
- Audiology
- Occupational Health
- Industrial Hygiene
Background:
- Noise-induced hearing loss (NIHL) is typically considered bilaterally symmetrical.
- Occupational Safety and Health Administration (OSHA) criteria are used to identify significant audiometric shifts.
Purpose of the Study:
- To investigate the laterality of audiometric shifts meeting OSHA criteria in an industrial population.
- To identify factors influencing unilateral versus bilateral shifts in noise-exposed workers.
Main Methods:
- Analysis of audiometric data from a large industrial sample.
- Evaluation of baseline hearing levels and subsequent OSHA-defined shifts.
- Statistical assessment of factors associated with unilateral OSHA shifts.
Main Results:
- 80% of OSHA-defined audiometric shifts were unilateral.
- Asymmetric baseline hearing was the primary predictor of unilateral shifts.
- Better-hearing ears were more prone to OSHA shifts than poorer-hearing ears.
- In cases of symmetric baseline hearing, left ears showed more OSHA shifts.
Conclusions:
- OSHA shift laterality is frequently unilateral, contrary to general NIHL assumptions.
- Pre-existing hearing asymmetry significantly impacts the laterality of noise-induced shifts.
- Hearing conservation programs must consider individual asymmetries when interpreting OSHA shifts.