Prevalence of noise induced hearing loss among employees at a mining industry in Zimbabwe

Background: Noise induced hearing loss (NIHL) is within the top five occupational illnesses in Zimbabwe. Workers at a mining company complained about loss of hearing at the mine clinic. Objective: To determine the prevalence of NIHL among employees at the Mine. Methods: We conducted a descriptive cross sectional study at the mine. Workers were proportionally selected to represent all the mine departments or working areas. We measured noise levels at various mine sites, conducted a walk-through survey to observe noise related worker practices and conducted audiometric testing. Results: Mean age for workers was 34.8±7.6 years and the mean duration of exposure to noise was 7.5±1.2 years. All workers could define noise. Ninety (53%) workers attributed NIHL to noisy work environment. Excessive noise levels were in Plant Processing (94 dBA), Underground Mining (102 dBA) and (Underground Workshop (103 dBA). Sixty two (36.7%) workers had NIHL. NIHL increased as a function of age (chi square=30.99 df=3 p 0.01) and was associated with work area (chi square=24.96 df=5 p 0.01). Observed workers took heed of noise warnings. There was no documented hearing conservation program at the mine. Conclusion: The prevalence of NIHL of 37% is high. Age and work area were associated with NIHL. Studies reported that age tends to distort the relationship between noise exposure and NIHL. Mine management should institute a hearing conservation program to protect employees against hazardous noise. Management may meanwhile use administrative controls and adhere to permissible exposure limits according to the noise regulations.