Predicting standard threshold shifts for occupational hearing loss among miners age categories. The differences in mean STS between males and females were greatest in the high PLH and > 41 years age categories. Predicting standard threshold shifts for occupational hearing loss The year 2014 was set as the baseline year; 2015, 2016, 2017, and 2018 represented cumulative years of noise and dust exposure. The log-transformed STS data was used in the mixed effects linear regression model as the outcome variable; the predictor variables were sex, age, PLH, noise exposure level, dust exposure level, and years of exposure (as described in Table III). 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 effects on STS of a unit increase in PLH, age, duration of exposure, and noise exposure level were all < 10%, but nevertheless statistically significant. The effect of dust exposure on STS was not statistically significant. The likelihood ratio test showed that the predictive model was a good fit (p < 0.001). Figure 4 shows an increasing effect of years of exposure on predicted STS for both male and female miners, controlling for age, PLH, and noise and dust levels. There was a steady increase in the predicted STS (and, therefore, a gradual hearing deterioration) for both the left and the right ears over time. Males start with a higher baseline STS and maintain higher STS levels across all years of exposure, compared to females. Figure 5 shows the effect of increasing age on the predicted STS for males and females, when years of exposure, PLH, and noise and dust levels were controlled for. For males, the predicted STS increased steadily, and was higher than that for females for both the left and right ears. Again, males start with a higher baseline STS than females, which is consistent across all ages. (2020) that male gold miners older than 40 years and exposed to excessive occupational noise had hearing deterioration in the high frequencies. Bilateral loss of hearing, measured by STS (HFA234) was generally worse in male than female miners. This may be due to differences in genetic susceptibility (SliwinskaKowalska and Pawelczyk, 2013), recreational noise exposure (Gates et al., 2000), previous occupational noise exposure (Grobler et al., 2020), diagnosis of conductive hearing loss (Ntlhakana, Khoza-Shangase, and Nelson, 2020), or medical conditions such as TB and HIV, and treatments thereof (Khoza- Discussion Although the STS milestone (Regulation 839) was introduced by the DMRE and due to be updated in 2024 (‘by December 2016, no employee’s STS will exceed 10 dB from the baseline when averaged at 2000, 3000 and 4000 Hz in one or both ears’) (Chamber of Mines, 2016), our study is the first to evaluate the progress made by this platinum mine. By analysing the mine’s data we were able to benchmark miners’ hearing, track STS deterioration, and identify miners at risk of developing hearing loss. In this group of miners, both age and sex were associated with deterioration in hearing, measured by increases in STS in the high frequencies. This supports the findings of Grobler et al. Figure 4—Prediction of STS for males and females, over 10 years (A and B) 95% CI predictive margins Table III Average predicted STS for miners from 2014 to 2018 Standard threshold shifts (dBHL) Left ear Variable Estimated effect (%) 95% CI p value Estimated effect (%) Sex (male) PLH Age (years) Duration of exposure from 2014 (years) Noise level (dBA) Dust level (mg/m3) 0.27 0.08 0.03 0.03 0.01 0.02 0.220–0.323 0.078–0.083 0.0367–0.040 0.0524–0.059 0.003–0.008 –0.094–0.1538 The Journal of the Southern African Institute of Mining and Metallurgy < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 0.270 VOLUME 121 0.21 0.08 0.04 0.03 0. 00 –0.01 Right ear 95% CI p value 0.162–0.261 < 0.001 0.075–0.079 < 0.001 0.038–0.041 < 0.001 0.024–0.031 < 0.001 0.002–0.007 0.002 –0.132–0.109 0.850 AUGUST 2021 401 ◀