Occupational noise-induced hearing loss: What is the contribution of personal noise exposures? A case study of mineworkers at a large-scale platinum mine in South Africa

Background: South African mineworkers are exposed to excessive noise which leads to occupational noise-induced hearing loss (ONIHL). However, there is a dearth of literature on the contribution of personal noise exposure measurements to predict the development of ONIHL. Aim: We aimed to determine the predictive ability of age, sex, personal noise measurements, and work shift duration as early signs of hearing deterioration associated with ONIHL for mineworkers at a large-scale platinum mine in South Africa. Methods: Two merged electronic datasets, comprising records of 521 mineworkers, were analysed, viz. a dataset of personal noise exposure measurements and an audiometry screening dataset, for the period 2014 to 2018. Pearson Chi 2 test described the associations between personal noise measurements, age, sex and shift duration, and hearing deterioration (STS). LOWESS assessed the correlation between personal and area noise measurements and hearing deterioration and personal noise measurements. Multinomial logistic regression analysis was used to identify risk for ONIHL, classified as mild, moderate, moderate-severe and profound hearing loss. Results: Most of the mineworkers were male ( n = 480; 92.1%), aged 26-55 years ( n = 452; 86.6%), and most were exposed to personal noise measurements less than 85 dB(A) ( n = 303; 61.1%). Pearson Chi 2 indicated age as a significant risk factor associated with STS. LOWESS indicated a positive association between personal and area noise measurements, but no association between personal noise measurements and STS. Multinomial logistic regression showed age as a significant risk for STS, mostly for mineworkers with STSs at mild, moderate and moderate-severe hearing loss in both ears. Conclusion: Mineworkers’ age was associated with STSs and was a risk factor that had a significant predictive ability for ONIHL. We highlighted the usefulness of personal noise measurements as risk-based assessment tools for audiometry surveillance that the South African mines could use to evaluate noise reduction strategies and outcomes for ONIHL prevention.