Study of occupational noise - induced hearing loss in a tractor manufacturing plant

Noise Induced Hearing Loss (NIHL) is one of the most common occupational diseases in the world. About 16% of hearing loss is associated with noise exposure in the workplaces. The aim of this research was investigation of the relationship between noise exposure and hearing loss. This cross-sectional study was conducted in 2010 on1062 workers in Tabriz Tractor Manufacturing Plant. In this study، the equivalent sound level (Leq) more than 85dB (A) was considered as exposure and hearing loss as outcome. A checklist of items was used in order to extract data from the workers'' medical records which included age، work experience، duration of daily work in a noisy environment and hearing loss. Based on the results، a regression model was suggested. Total of 1062 workers under study، including 392 workers (36. 9%) were exposed to equivalent sound level equal or more than 85dB (A) (exposed group) and 670 workers (63. 1%) to less than 85dB (A) (non exposure group). Results showed that the hearing loss increased by age، noise exposure and work experience. Based on the results، it is suggested to control noise exposure for studied workers and apply noise control mechanisms for reducing hearing loss، increase work efficiency and reduce cure costs. Suggested regression model can be used for prediction of NIHL in that workplace for care of hearing loss of studied workers.