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Original Articles
- Evaluation of Puretone Threshold Using Periodic Health Examination Data on Noise-exposed Workers in Korea .
- Kyoo Sang Kim, Yangho Kim, Jung Keun Choi, Jung Sun Park, Young Han Moon
- Korean J Prev Med. 1999;32(1):30-39.
- 2,193 View
- 24 Download
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Abstract
PDF - OBJECTIVES
This study was carried out to evaluate hearing impairment judgement and to investigate the differences in various diagnostic criteria for noise-induced hearing loss (NIHL) among workers who required for close observation (C). METHODS: Out of 731,029 workers who had taken the specific periodic health examination in 1994, we used the audiometric data on 37,999 workers (C) eliminating the employees who had previous otologic problems. Many investigators have being using different criteria for the evaluation of hearing impairment. In this study, we used the criteria of early (1989-1994), current, compensation for NIHL in Korea, 2-, 3-, 4-divided classification and hearing loss at 4,000 Hz and compared the evaluation results. RESULTS: The prevalences of C and workers who had occupational disease (D1) diagnosed for NIHL were 11.1 % and 0.44 %. There were significant difference in the prevalences of C and D1 depending on different province of Korea. Pure tone averages (PTAs) were not appropriately applied in their evaluation. 97% of workers whom we studied on were below the level of mild hearing loss judged by ISO standard. However, there were wide variations in the prevalence rate of mild hearing loss by diagnostic criteria. Thus, there were different judgements in determining the degree of NIHL depending on which diagnostic criteria were utilized. PTAs were found 20.54 (Rt) and 20.74 (Lt) when the method of 3-divided classification was applied for audiometric data. The degree of hearing impairment of the left ear was more severe than that of right ear. The prevalence of normal hearing threshold below 20 dB was 75.4% and the range of difference in both ear was below 10 dB. Right sided hearing threshold levels were 21.08 dB (500 Hz), 18.44 dB (1,000 Hz), 22.09 (2,000 Hz) and 52.36 dB (4,000 Hz). There was typical high frequency loss (C5-dip at 4,000 Hz) above 30 - 40 dB in normal hearing level. The increasing trend in hearing threshold level was gradually decreased by the increase of PTAs. The difference between PTAs and threshold at 4,000 Hz was about 10 dB. CONCLUSIONS: We could found that PTAs in the previous examination were not appropriately evaluated. This study revealed that they did not use unique criteria for managing the workers of NIHL. For the prevention of NIHL, it was found that the quality control on diagnosis and comprehensive management program were required, especially for those of hearing loss (C). -
Summary
- A study on diagnostic criteria of noise-induced hearing loss among workers in an iron foundry.
- Ji Yong Kim, Hyun Sul Lim, Hae Kwan Cheong, Ok Ryun Moon
- Korean J Prev Med. 1993;26(3):371-386.
- 2,076 View
- 28 Download
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Abstract
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- This study was carried out to evaluate diagnostic criteria of noise-induced hearing loss (NIHL) among workers in an iron foundry. Of 1,093 workers under the observation of noise-specific health examination, 184 workers were selected by way of first and second screening audiometric examination. A questionnaire survey, otological examinations, Rinne test and audiometric test were performed and the results were as follows; The degree of hearing impairment in the left ear was more severe than in the right ear(p<0.05). The difference between hearing threshold of the first and the second hearing test at 1,000 Hz was about 5 dB with a narrow range of deviations while the difference at 4,000 Hz was about -7dB with a wide range. Of the total study workers, 84.8% were tested within 15 hours away from noise exposure, and the rest after 16 hours. This study has identified that mean hearing loss at 4,000 Hz showed a significant statistical difference among the two study groups while mean hearing loss by 4-divided classification did not. The same phenomena were observed between the group with and without tinnitus and between the group with and without difficulty in hearing(p<0.05). Among 184 workers, 10 workers(5.4%) diagnosed as NIHL by old diagnostic criteria in contrast to 150 workers diagnosed as NIHL by the new diagnostic criteria. There was a significant difference between the two groups in the average hearing loss at 4,000 Hz and 4-divided classification(p<0.01), but there were no significant difference in age, the duration of employment, blood pressure and the duration wearing the personal hearing protector(p>0.05). If we apply Early Loss Index(ELI) method, some workers in younger age group diagnosed as NIHL by the new diagnostic criteria were fallen into within the normal range. In the mean time older age group show reverse results in contrast to the above finding. It is too early to confirm the value of the usage of the new diagnostic criteria in hearing examination. Further study is called for to verify the value of this criteria.
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