To determine the recovery time from noise-induced temporary threshold shift (TTS), a prospective field study was conducted at three worksites where workers are known to be exposed high level of noise. Subjects were selected according to answers on a questionnaire which inquired about otological history and previous noise exposure, including avocational, military and occupational exposures. After excluding employees with past otologic problems, recent exposure to high level noise, and under medications, total 92 employees participated in the study. Among 92 participants, complete consecutive audiometric examinations were carried out at 0~2 hours, 5~7 hours, 14~16 hours after worktime noise exposure on 26 participants wearing hearing protectors and 22 participants wearing no protective devices. The difference between the hearing level 0~2 hours after noise exposure and 5~7 hours is statistically significant by paired t-test(p<0.01). The median recovery times calculated from the data of 22 participants wearing no protective hearing devices are 15.6 hours at 4000 Hz, and 7.7 hours, 10.3 hours, 8.4 hours at 1000 Hz, 2000 Hz and 8000 Hz respectively. These data suggest that when measuring the pure tone audiometry for noise exposed workers, at least 16 hours noise-free interval is required.
Audiometry ; Hearing ; Hearing Loss, Noise-Induced ; Humans ; Military Personnel ; Noise ; Occupational Exposure ; Prospective Studies ; Protective Devices ; Questionnaires ; Workplace

To determine the recovery time from noise-induced temporary threshold shift (TTS), a prospective field study was conducted at three worksites where workers are known to be exposed high level of noise. Subjects were selected according to answers on a questionnaire which inquired about otological history and previous noise exposure, including avocational, military and occupational exposures. After excluding employees with past otologic problems, recent exposure to high level noise, and under medications, total 92 employees participated in the study. Among 92 participants, complete consecutive audiometric examinations were carried out at 0~2 hours, 5~7 hours, 14~16 hours after worktime noise exposure on 26 participants wearing hearing protectors and 22 participants wearing no protective devices. The difference between the hearing level 0~2 hours after noise exposure and 5~7 hours is statistically significant by paired t-test(p<0.01). The median recovery times calculated from the data of 22 participants wearing no protective hearing devices are 15.6 hours at 4000 Hz, and 7.7 hours, 10.3 hours, 8.4 hours at 1000 Hz, 2000 Hz and 8000 Hz respectively. These data suggest that when measuring the pure tone audiometry for noise exposed workers, at least 16 hours noise-free interval is required.
Audiometry ; Hearing ; Hearing Loss, Noise-Induced ; Humans ; Military Personnel ; Noise ; Occupational Exposure ; Prospective Studies ; Protective Devices ; Questionnaires ; Workplace

This cohort study is a collaborative effort of 8 institutions. The goal is to establish a large scale cohort that can be followed for 10 or more years to assess the relationship between life-styles and cancer occurrence, and to evaluate the role of environmental exposures in the development of six major sites of cancers(stomach, liver, lung, colorectum, uterine cervix and female breast) in the rural population. Since 1993, 11,304 men and women aged over 35 living in four areas have been recruited. The number of target population is 30,000 persons, which is expected to be successfully recruited until 1999. Each subject has completed a detailed questionnaire on general life-styles, reproductive factors, and agricultural chemical exposures through the interview. Anthropometric measurements with body fat composition and the routine clinical laboratories were examined. For the cancer-free cohort, physical examination by the physicians and serologic tests for hepatitis markers, some tumor markers, and lipid profile have been done, but not all. In order to provide an opportunity to incorporate barious biomarkers of exposure and effect as well as genetic susceptibility, a biologic tissue bank has been established from blood and urine sample(plasma, WBC buffy-coat, RBC clots, and urine supernatant) stored at-70degrees C. Re-examination of changes in exposere to risk factors will be done periodically. Disease occurrence will be ascertained by the active(mainly through diagnosis by physicians) and the passive surveillance(through both death certificate and screening of medical utilization records).
Adipose Tissue ; Biomarkers ; Cervix Uteri ; Cohort Studies* ; Death Certificates ; Diagnosis ; Environmental Exposure ; Female ; Genetic Predisposition to Disease ; Health Services Needs and Demand ; Hepatitis ; Humans ; Korea* ; Liver ; Lung ; Male ; Mass Screening ; Physical Examination ; Risk Factors ; Rural Population ; Serologic Tests ; Tissue Banks ; Biomarkers, Tumor ; Surveys and Questionnaires