Effect of noise exposure on occupational injuries: a cross-sectional study.

BACKGROUND Noise exposure is the most frequent occupational factor which may increase the risk of work-related injuries. The purpose of this study was to estimate the association between occupational injuries and noise exposure as well as hearing loss. METHODS This study was conducted from April 2008 to March 2009 on 1062 workers in the Tabriz Tractor Manufacturing Plant. Sound pressure level (SPL) ≥85 dB in the workplace was considered as the independent variable (exposure) and physical occupational injuries as the dependent variable (outcome). Data were extracted from the workers' medical records using a checklist. RESULTS Of 1062 volunteers, 392 (36.9%) were exposed (with SPL≥85 dB) and 670 (63.1%) were unexposed (with SPL<85 dB). One hundred and seventy-six injuries occurred during the study period. Frequency of injuries was about 16 per 200,000 hours, severity of injuries was about 75 per 200,000 hours and incidence rate of injuries was 16%. The exposed group had 1.52 fold increased risk of injury compared to unexposed group (P=0.012). Compared to group with normal hearing status, the risk of occupational injuries increased 1.72 fold in group with partial hearing loss (P=0.062), 7.87 fold in group with mild hearing loss (P=0.003), and 4.58 in group with moderate hearing loss (P=0.049). CONCLUSION Occupational noise exposure and hearing impairment have adverse effect on work safety and can increase the probability of work-related injuries. This means reducing noise exposure can contribute to increase safety in workplaces where noise is a factor. Furthermore, using assistive listening devices may reduce risk of work injuries among hearing-impaired workers.