| Summary: | 碩士 === 高雄醫學大學 === 職業安全衛生研究所碩士班 === 94 === Objective: To investigate the characteristics and risk factors of hearing loss among noise-exposed workers in southern Taiwan, and evaluate the progression of hearing loss and the effect of hearing protection measures.
Method: Questionnaire of personal data (personal habit, occupational and non-occupational exposure) and data of pure tone auditory threshold test of 1117 workers were collected while annual health examination performed in medical center in southern Taiwan during 2003~2004, and pure tone auditory threshold test of 160 workers were analyzed for searching serial change (2002~2005).
Result:
1. Our study population included 604 noise-exposed male workers. The workers’ average age was 46.5 years old. 152(25.2%) workers suffered from hearing loss according to the criteria established by AAO-HNS(a 25dB or greater loss in either ear at an average of: 500, 1000 & 2000 Hz).
2. The lowest level of mean auditory threshold is at 1000 Hz (left ear: 18.68 dB, right ear: 18.20 dB). The highest level of mean auditory threshold is at 6000 Hz (left ear: 30.27 dB, right ear: 30.59 dB). The results of pure tone auditory threshold test at 500, 1000 and 2000Hz reveal that the threshold level of left ear is higher than that of right ear (left ear: 19.35 dB, right ear: 19.05 dB). The greatest hearing threshold shift in our study occurred at 6000 Hz. This finding differs from those of a typical case of noise-induced hearing loss(NIHL). The greatest hearing threshold shift in typical NIHL usually occurs at 4000 Hz.
3. After adjusting the confounding factors, the relative risk of hearing loss are as followings: a. chewing betel nut everyday to no betel nut chewing habit (OR=5.78)；b. relatives had hearing loss in childhood (OR=5.42)；c. organic solvent exposure frequency ≧1 time/day to 0~1 time/week (OR=2.93)；d. alcohol consuming > 3 times/week to no alcohol consuming habit (OR=2.25).
4. The mean hearing loss rate of 160 workers at different frequency are as followings: 500 Hz (1.61 dB/year), 1k Hz (1.43 dB/year), 2k Hz (1.54 dB/year) , 3k Hz (1.71 dB/year), 4k Hz (2.25 dB/year) and 6k Hz (2.43 dB/year). Comparison of the 160 workers’ mean auditory threshold (2k, 3k, 4k Hz) in 2005 to baseline in 2002, the prevalence of mean auditory threshold of either ear increases above 10 dB is 21.3%. According to OSHA, 3~6% of the prevalence is acceptable. Compare to our data, hearing loss prevalence is beyond the limit by 9~18%.
Conclusion: 1. Pure tone auditory threshold test should include 8000 Hz. 2.
The risk factors associated with hearing loss are as followings: (1) Aging (2)
Betel nut chewing (3) Familial history (4) Organic solvent exposure (5)
Alcohol drinking habit. 3. Current hearing conservation program need to be
enforced.
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