Severe noise-induced deafness--a 10-year review of cases

Noise Induced Deafness (NID) is the leading occupational disease in Singapore. Every year, over 500 new cases of NID are detected by the Department of Industrial Health (DIH). Severe NID is a disabling disease which is compensable under the law. A retrospective study was conducted to elicit the profile of workers with severe, disabling NID. From 1 January 1985 to 31 December 1994, the DIH confirmed 127 of such cases. Of these, 57 (44.9%) were involved in the building and repair of ships and boats, 30 (23.6%) with the basic steel industries, manufacture and fabrication of metal products and storage batteries, 9 (7.2%) with the transport and allied support industries, 7 (5.5%) in granite quarrying, 7 (5.5%) in the manufacture of food and drinks, 5 (3.9%) in the manufacture of wooden furniture and 7 (5.5%) in other industries such as manufacture of glass, electricity generation, construction, textiles, printing and so on. The mean age of these workers upon diagnosis of severe NID was 48 years (SD 8.07). The mean duration of exposure to noise was 24 years (SD 9.11). The mean of the average hearing thresholds at 1, 2 and 3 kHz for these workers was found to be 61.5 dBA (SD 4.26). The main jobs at risk were grit blasters, steel workers, fitters, boiler fabricators, panel beaters and carpenters. Noise dosimetry was performed on 46 of the cases and the mean time-weighted exposure level was 90 dBA (SD 10.00). Finally, 82.7% of cases already had audiometric evidence of severe deafness at the time of notification.