Occupational Noise Exposure and Hearing Protector Use in Canadian Lumber Mills

Abstract

Noise exposure is probably the most ubiquitous of all occupational hazards, and there is evidence for causal links between noise and both auditory and nonauditory health effects. Noise control at source is rarely considered, resulting in reliance on hearing protection devices to reduce exposure. A comprehensive noise survey of four lumber mills using a randomized sampling strategy was undertaken, resulting in 350 full-shift personal dosimetry measurements. Sound frequency spectrum data and information on hearing protector usage was collected. A determinants-of-exposure regression model for noise was developed. Mean (L _eq,8hr) exposure level was 91.7 dBA, well above the exposure British Columbia (BC) limit of 85 dBA. Of 52 jobs for which more than a single observation was made, only 4 were below the exposure limit. Twenty-eight jobs had means over 90 dBA, and four jobs had means over 100 dBA. The sawmill and by-products departments of the lumber mills had the highest exposure to low frequency noise, while the planing and saw filing areas had the highest exposure to high frequency noise. Hearing protector use was greatest among those exposed above 95 dBA, and among those exposed between 85 and 95 dBA, self-reported use was 84% for 73% of the time. The determinants of exposure model had an R² of 0.52, and the within-participant correlation was 0.07. Key predictors in the final model were mill; enclosure and enclosure construction material; and certain departments, jobs, and noise sources. The study showed that workers in lumber mills are highly exposed to noise, and although the prevalence of the use of hearing protection is high, their use is unlikely to provide complete protection again noise-induced hearing loss at the observed exposures. Determinants of noise exposure modeling offers a good method for the quantitative estimation of noise exposure.

Keywords:

• ear protective devices
• hearing loss
• noise
• noise induced
• occupational exposure

ACKNOWLEDGMENTS

Funding for this study was provided by the British Columbia Medical Services Foundation and by the Canadian Institutes for Health Research (CIHR). The authors would like to thank the lumber mill workers of British Columbia, the management of the participating mills, and the IWA, CEP, and PPWC labor unions. Thanks also to Todd Yip, Bob Hirtle, and Martine Dennekamp who assisted with field work

Notes

^A Sawmill surface area refers to only the sawmill and does not include other buildings on the site.

^B Refers to the construction dates of the current buildings. Mill with older construction date has been upgraded with respect to technology, but not building structure (although most have been continually modified).

^A Mill P worked 12-hr shifts, the rest worked 8-hr shifts.

^A By descending order of unweighted L_p

^A Wears both plugs and muffs.

^A CI, confidence interval; ref, reference category; n, number of observations.

^A Time-weighted average

^B Combination of dosimetry and sound level measurements