ABSTRACT
BACKGROUND AND OBJECTIVES: There is no effective treatment for noise-induced hearing loss (NIHL), and for this reason, prevention is very important. The purpose of this study is to investigate the epidemiologic and audiometric properties of NIHL in subway workers. MATERIALS AND METHODS: This study included 10,792 employees who have worked in the subway. Their hearing acuity was screened out by pure tone audiometry for 1 K & 4 KHz. Of the employees, those whose hearing loss was not caused by noise were excluded from the study and the remaining 665 employees were investigated. The epidemiologic and audiometric properties were investigated on the basis of their ages and working durations. RESULTS: Among the 10,792 employees, 665 (6.2%) showed NIHL. The risk of NIHL increased significantly in individuals who had worked more than 5 years. At 4 KHz, the hearing threshold shift occured within 5 years, then reached a plateau. But below 2 KHz, it progressed gradually, becoming prominent after 10 years of noise exposure. CONCLUSION: We suggest that prevention from exposure to noise is necessary for individuals whose working duration is more than 5 years.