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. 2019 Apr 16;16(8):1367.
doi: 10.3390/ijerph16081367.

Prevalence of Noise-Induced Hearing Loss Among Tanzanian Iron and Steel Workers: A Cross-Sectional Study

Israel P Nyarubeli  1   2   3 , Alexander M Tungu  4 , Bente E Moen  5   6 , Magne Bråtveit  7
Affiliations

Prevalence of Noise-Induced Hearing Loss Among Tanzanian Iron and Steel Workers: A Cross-Sectional Study

Israel P Nyarubeli et al. Int J Environ Res Public Health. .

Abstract

Iron and steel factory workers in Tanzania are likely to develop noise-induced hearing loss (NIHL) due to exposure to high sound levels. Studies on hearing status in this population are lacking. The aims of this study were to determine prevalence of NIHL among iron and steel workers and compare hearing thresholds at different frequencies with a control group. We conducted a cross-sectional study among 221 iron and steel workers exposed to average noise level of 92 dB(A), compared with 107 primary school teachers recruited as controls and exposed to average noise level of 79.7 dB(A). We used a questionnaire-based interview to collect information on socio demographic characteristics and other confounding variables. Hearing loss was defined as hearing threshold levels ≥25 dB hearing loss in either ear at 3000, 4000 or 6000 Hz. The prevalence of hearing loss was significantly higher among the exposed group than among the controls, i.e. 48% and 31%, respectively. There were significant differences in hearing thresholds between the exposed and control groups at 3000, 4000, 6000, and 8000 Hz. Hearing loss was more frequent among workers exposed to higher noise levels than among the controls suggesting that iron and steel workers run a higher risk of developing hearing loss.

Keywords: Tanzania; audiometry; exposed; hearing threshold; iron and steel; noise-induced hearing loss; occupational.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Flow chart describing the participants in the study of hearing loss among exposed iron and steel factory workers (n = 221) and controls—primary school teachers (n = 107) in Tanzania.
Figure 2
Figure 2
Hearing threshold of noise-exposed male workers (n = 221) (dotted lines) compared with male controls (n = 107) (solid lines) in Tanzania, stratified into age groups (triplets).
Figure 3
Figure 3
(a–c) Mean of the measured hearing threshold by audiometry (dotted lines) and median noise-induced permanent threshold shift (NIPTS) predicted by ISO 1999 (solid lines) for the three age-groups of iron and steel workers in Tanzania exposed to an average noise level of LAeq8h of 92 dB(A) for the mean duration of noise exposure within each age group.
See this image and copyright information in PMC

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