Basic Study on the Hearing-threshold Levels of Workers with Noise-induced Hearing Loss in Korea

Ahn, Yeon Soon; Moon, Young Han; Lee, Sang Yeal; Lee, Kyung Nam

Abstract

OBJECTIVES
This study was carried out to analyze the hearing-threshold levels and relating factors of 1,048 workers with noise-induced hearing loss(D1).
METHODS
We analyzed the hearing-threshold levels and relating factors of 1,048 workers with noise-induced hearing loss(D1) examined by the summary reports of specific health examination results of industries and personal reports of specific health examination results reported by 58 specific health examination institutes and 8 secondary pneumoconiosis examination institutes in 1996.
RESULTS
Among 1,048 workers at 510 workplaces, male workers were 1,009 (96.3%) and female workers were 39 (3.7%). The mean ages of workers initially exposed to noise and at present were 28.7 and 47.2, respectively. The duration of total exposure was 16.5 years. Average hearing-threshold levels analyzed by three-divided classification of the study subjects were 43.7dB(Lt) and 42.6dB(Rt). Those analyzed by six-divided classification were 50.5dB(Lt) and 48.6dB(Rt). Among workers with noise-induced shearing loss(D1), 16.3% was unilateral hearing loss and 84.6% was classified to compensation case. 8.8%(Rt) and 10.2%(Lt) of them were suspected to be conductive hearing loss by differences of air-bone hearing-threshold levels. Hearing-threshold levels of workers in manufacturing industry were significantly increased during the short exposure compared with the levels in mining industry. Among manufacturing industries, hearing-threshold levels of workers in trailer and other transportation equipment manufacturing industry were significantly increased. Age and duration of total noise exposure were not significantly related to the average hearing-threshold levels analyzed by three-divided classification. Hearing-threshold levels of female workers were significantly increased during the short exposure compared with those of male workers. Hearing-threshold levels of workers at the high risk group, ages of 20s, 30s and total exposure duration of less than 10 years, were not significantly increased compared with those of the other groups. However, they were exposed at young ages. The 3 leading industries of workers at high risk group were trailer and other transportation equipment manufacturing, automobile manufacturing and assemble-metal manufacturing industries.
CONCLUSIONS
This study was the first nationwide analysis of the hearing-threshold levels and relating factors of workers with noise-induced hearing loss(D1). We found the differences of the real number by the statistics of the department of labour and the expected number of worker's compensations for occupationally-induced hearing loss estimated by this study. According to the results of this study, we should carefully examine the methods to narrow this difference.