Occupational Noise Exposure and Hearing Impairment among Spinning Workers in Iran

Background Hearing impairment (HI), resulting from noise exposure, can be incapacitating and irreversible. Objectives The present study aimed to determine the relationship between noise exposure and HI among workers and employees in a spinning industry. Methods This cross sectional study was conducted on 489 workers in a spinning industry in Iran during 2015. The census method was applied for the purpose of sampling. The hearing threshold of each ear was determined during work shifts, using Madsen audiometric device. HI was calculated, based on the guidelines by the American Medical Association (AMA). The effects of different variables on HI were assessed via regression analysis. Results The mean noise level at workplace was 88.87 ± 13.6 dB. The highest noise level in the sampled worksites was observed in the ring spinning section (94.1 ± 3.2 dB). Based on the results, maximum HI in both ears was 41%. The findings showed a significant relationship between HI and noise level, age, educational level, and work shift. Also, a linear equation was proposed in which each dB increase in noise level resulted in an approximately 0.5% decline in HI. Conclusions By introducing an equation, this study demonstrated that spinning workers, who are exposed to relatively high noise levels, are at risk of major HI. In addition, a number of potential contributing factors, including age, work experience, occupation, and work shift, were correlated with HI.