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.
Highlights
Noise-induced hearing loss (NIHL) is an underestimated public health concern [1,2]
The aims of this study were to determine the prevalence of NIHL among iron and steel workers, and to compare the hearing thresholds at different frequencies between these workers and a control group exposed to a low level of occupational noise
The overall prevalence of hearing loss was significantly higher (Chi square test, p = 0.003) among exposed workers (48%) than among the controls (31%)
Summary
Noise-induced hearing loss (NIHL) is an underestimated public health concern [1,2]. Estimates of the prevalence of hearing loss related to noise exposure above 85 dB(A) vary in the range of 7–21% or higher [5]. Prevalence is estimated to be higher in the low and middle-income countries compared to the findings in other parts of the world [4]. This may be due to ongoing economic investments in industrialization coupled with challenges related to an inadequate public health policy, lack of regulatory frameworks and limited resources spent on preventive measures. Studies highlight noise exposure as one major risk factor contributing to hearing loss [1,4,5]
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