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The dose-response relationship between in-ear occupational noise exposure and hearing loss
  1. Peter M Rabinowitz1,
  2. Deron Galusha1,
  3. Christine Dixon-Ernst2,
  4. Jane E Clougherty3,
  5. Richard L Neitzel4
  1. 1Occupational and Environmental Medicine Program, Department of Medicine, Yale University School of Medicine, New Haven, Connecticut, USA
  2. 2Alcoa, Inc., Pittsburgh, Pennsylvania, USA
  3. 33Department of Occupational and Environmental Health, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
  4. 4Department of Environmental Health Sciences and Risk Science Center, University of Michigan, Ann Arbor, Michigan, USA
  1. Correspondence to Dr Peter M Rabinowitz, Occupational and Environmental Medicine Program, Department of Medicine, Yale University School of Medicine, 135 College Street, 3rd Floor, New Haven, Connecticut 06510, USA; peter.rabinowitz{at}yale.edu

Abstract

Objectives Current understanding of the dose-response relationship between occupational noise and hearing loss is based on cross-sectional studies prior to the widespread use of hearing protection, and with limited data regarding noise exposures below 85 dBA. We report on the hearing loss experience of a unique cohort of industrial workers, with daily monitoring of noise inside of hearing protection devices.

Methods At an industrial facility, workers exhibiting accelerated hearing loss were enrolled in a mandatory programme to monitor daily noise exposures inside of hearing protection. We compared these noise measurements (as time-weighted LAVG) to interval rates of high-frequency hearing loss over a 6-year period using a mixed-effects model, adjusting for potential confounders.

Results Workers’ high-frequency hearing levels at study inception averaged more than 40 dB Hearing threshold level (HTL). Most noise exposures were less than 85 dBA (mean LAVG 76 dBA, IQR 74–80 dBA). We found no statistical relationship between LAvg and high-frequency hearing loss (p=0.53). Using a metric for monthly maximum noise exposure did not improve model fit.

Conclusions At-ear noise exposures below 85 dBA did not show an association with risk of high-frequency hearing loss among workers with substantial past noise exposure and hearing loss at baseline. Therefore, effective noise control to below 85 dBA may lead to significant reduction in occupational hearing loss risk in such individuals. Further research is needed on the dose-response relationship of noise and hearing loss in individuals with normal hearing and little prior noise exposure.

  • Hearing loss
  • Noise induced
  • Dose response

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