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Hearing Protector Attenuation and Noise Exposure Among Metal Manufacturing Workers

Sayler, Stephanie K.1; Rabinowitz, Peter M.2; Galusha, Deron3; Sun, Kan1; Neitzel, Richard L.1

doi: 10.1097/AUD.0000000000000650
Research Article: PDF Only

Objectives: This study utilized personal noise measurements and fit-testing to evaluate the association between noise exposures and personal attenuation rating (PAR) values among participating workers, and second, to compare the attenuated exposure levels received by the workers and the British Standards Institute’s recommended noise exposure range of 70 to 80 dBA.

Design: We measured hearing protection device (HPD) attenuation among a sample of 91 workers at 2 US metal manufacturing facilities, through performance of personal noise dosimetry measurements and HPD fit-testing over multiple work shifts. We compared this testing with participant questionnaires and annual audiometric hearing threshold results.

Results: The average 8-hr time-weighted average noise exposures for study participants was 79.8 dBA (SD = 7.0 dBA), and the average PAR from fit-testing was 20.1 dB (±6.7 dB). While differences existed between sites, 84% of the 251 PAR measurements resulted in effective protection levels below the recommended 70 dBA (indicating overprotection), while workers were underprotected (i.e., effective exposures >80 dBA) during <1% of monitored shifts. Our results also demonstrated a significant positive relationship between measured noise exposure and PAR among non–custom-molded plug users (p = 0.04). Non–custom-molded plug wearers also showed a significant increase in PAR by sequential fit-test interaction (p = 0.01), where on average, subsequent fit-testing resulted in increasingly higher HPD attenuation. Workers at site 1 showed higher PARs. PARs were significantly related to race, even when adjusting for site location. While age, hearing threshold level, task, and self-reported tinnitus showed no significant effect on individual PAR in an unadjusted model, site, race, and sand- or water-blasting activities were significant predictors in adjusted models. Within-worker variability in time-weighted averages and PARs across repeated measurements was substantially lower than variability between workers.

Conclusions: Careful selection of HPDs is necessary to minimize instances of overprotection to workers in low and moderate occupational noise environments. The use of fit-testing in hearing conservation programs to evaluate PAR is recommended to avoid overprotection from noise exposure while also minimizing instances of under-attenuation.

1Department of Environmental Health Sciences, University of Michigan School of Public Health, Ann Arbor, Michigan, USA;

2Department of Environmental and Occupational Health Sciences, University of Washington School of Public Health, Seattle, Washington, USA; and

3Yale School of Medicine, New Haven, Connecticut, USA.

ACKNOWLEDGMENTS: The authors wish to thank the participating workers and facilities, without whose support this research would not have been possible.

This research was funded by grants from the National Institute on Aging (Disease, Disability and Death in an Aging Workforce, NIH/NIA, 1 R01 AG026291-06 – current, administered through Stanford University) to D.H.G.; National Institute for Occupational Health and Safety (assessing hearing conservation effectiveness, 1 R01 OH010132-01 – past) to D.H.G., P.M.R., and R.L.N.; and a contract with Alcoa Inc (current) to D.H.G.

The authors have no financial or conflict of interest to disclose.

Address for correspondence: Richard L. Neitzel, Department of Environmental Health Sciences, University of Michigan School of Public Health, 1415 Washington Heights, SPH I 6611D, Ann Arbor, MI 48109, USA. E-mail:

Received December 1, 2017; accepted July 7, 2018.

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