Predicting standard threshold shifts for occupational hearing loss among miners at a large-scale platinum mine in South Africa

L Ntlhakana,G Nelson,I Maposa,K Khoza-Shangase

doi:10.17159/2411-9717/1318/2021

Abstract

Occupational noise-induced hearing loss (ONIHL) is associated with various risk factors in South African mines. We investigated the association between standard threshold shifts (STSs) and exposure to noise and platinum mine dust (PMD), using demographic data, five years of annual audiometry screening results, and noise and dust exposure data. Miners' age, sex, percentage hearing loss (PLH), and dust and noise exposure data were gathered, and a linear mixed effects regression model used to predict STS. Average occupational exposure levels to noise and dust were calculated from recorded measurements. A total of 12 692 records were analysed. Most miners were male (89.6%) and more than 50% were younger than 41 years. More than 70% were exposed to > 85 dBA noise and 58% were exposed to 1.5-2.99 mg/m3 PMD. Changes in hearing levels ranged from 8.3 dBHL at baseline (2014/2015) to 10 dBHL in 2016 (STS), with no changes thereafter. The model showed that the estimated effect on STS for males was 27% and 21% higher than for females, for the left and right ear, respectively The estimated effect of age, PLH, noise exposure and years of exposure on STS was < 10% for each variable. There was no statistically significant association between PMD and STS. The combined effects of age, sex, years of exposure to noise, and noise exposure levels, and strength of associations can be used to predict STS for this group of miners. Our findings may be used to measure the efficacy of the mine's hearing conservation programme.

Highlights

In 2005, the most recent year for which data is available 16% of global disabling hearing impairment, which affects about four million adults, was due to occupational noise; with the burden ranging from 7% to 21% in different subregions.(Nelson et al, 2005) The estimated prevalence in African countries was 18% (12–23%).(Nelson et al, 2005) In the USA, the estimated prevalence of occupational noiseinduced hearing loss (ONIHL) in the mining industry for the period 2006–2010 was reported to be 24% (Masterson et al, 2015)
Research in South African mines has shown that age, sex (Strauss et al, 2014), ototoxic drugs used for treatment of pulmonary tuberculosis (PTB) and human immunodeficiency virus (HIV) (Khoza-Shangase, 2019; Brits et al, 2012), and noise exposure levels ≥ 85 dBA are associated with ONIHL (Edwards et al, 2015; Strauss et al, 2012; Balfour-Kaipa, 2014)
There were more males (n = 11 283; 89.6%) than females (n = 1 309; 10.4%); most (53.4%) were younger than 41 years, most (76.4%) had low percentage loss of hearing (PLH); 72.4% were exposed to noise levels of 85 dBA or higher; and 57.9% were exposed to 1.5–2.99 mg/ m3 platinum mine dust (PMD)

Summary

Introduction

In 2005, the most recent year for which data is available 16% of global disabling hearing impairment, which affects about four million adults, was due to occupational noise; with the burden ranging from 7% to 21% in different subregions.(Nelson et al, 2005) The estimated prevalence in African countries was 18% (12–23%).(Nelson et al, 2005) In the USA, the estimated prevalence of occupational noiseinduced hearing loss (ONIHL) in the mining industry for the period 2006–2010 was reported to be 24% (Masterson et al, 2015). Research on the associations of socio-demographic factors (age, sex, and race), genetic predisposition, recreational noise exposure, and occupational exposures (noise, platinum mine dust, and chemicals) (Pillay, 2020, Sepadi, Chadyiwa, and Nkosi, 2020) with ONIHL has been extensively conducted, globally (Khoza-Shangase, 2019; Campo, Morat, and Hong, 2013; 2019, Strauss et al, 2012; Brits et al, 2012; Grobler et al, 2020). Research in South African mines has shown that age, sex (Strauss et al, 2014), ototoxic drugs used for treatment of pulmonary tuberculosis (PTB) and human immunodeficiency virus (HIV) (Khoza-Shangase, 2019; Brits et al, 2012), and noise exposure levels ≥ 85 dBA are associated with ONIHL (Edwards et al, 2015; Strauss et al, 2012; Balfour-Kaipa, 2014)

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