Noise Exposure and Hearing Loss Among Sand and Gravel Miners

Abstract

The objectives of this study were to describe workplace noise exposures, risk factors for hearing loss, and hearing levels among sand and gravel miners, and to determine whether full shift noise exposures resulted in changes in hearing thresholds from baseline values. Sand and gravel miners (n = 317) were interviewed regarding medical history, leisure-time and occupational noise exposure, other occupational exposures, and use of hearing protection. Audiometric tests were performed both before the work shift (following a 12-hour noise-free interval) and immediately following the work shift. Full shift noise dosimetry was conducted. Miners' noise exposures exceeded the Recommended Exposure Limit (REL) of the National Institute for Occupational Safety and Health (NIOSH) for 69% of workers, and exceeded the Mine Safety and Health Administration's action level for enrollment in a hearing conservation program for 41% of workers. Significantly higher noise exposures occurred among employees of small companies, among workers with a job classification of truck driver, among males, and among black workers. Hearing protection usage was low, with 48% of subjects reporting that they never used hearing protection. Hearing impairment, as defined by NIOSH, was present among 37% of 275 subjects with valid audiograms. Black male workers and white male workers had higher hearing thresholds than males from a comparison North Carolina population unexposed to industrial noise. Small but statistically significant changes in hearing thresholds occurred following full shift noise exposure among subjects who had good hearing sensitivity at baseline. In a logistic regression model, age and history of a past noisy job were significant predictors of hearing impairment. Overall, sand and gravel workers have excessive noise exposures and significant hearing loss, and demonstrate inadequate use of hearing protection. Well-designed hearing conservation programs, with reduction of noise exposure, are clearly needed.

Keywords:

• hearing
• miners
• noise exposure

Notes

^A 80-dBA threshold, 3-dB exchange rate.

^B 80-dBA threshold, 5-dB exchange rate.

^C Job classifications with fewer than 3 subjects not included.

^D <.01.

^E <.001.

^A p < .001.

^B Job categories with 3 or fewer subjects not presented.

^A Odds ratio and for an increase of 10 years in age.

^A Good hearing sensitivity = mean threshold at 1000, 2000, 3000, and 4000 Hz ≤ 15 dB.

^B Poorer hearing sensitivity = mean threshold at 1000, 2000, 3000, and 4000 Hz > 15 dB.

^A p < .001.

^B p < .01.

^C Job categories with three or fewer subjects not presented.