Abstract
Metals, such as lead, may be ototoxic, but this property is not well understood, especially in conjunction with noise. This cross-sectional study investigated hearing, noise, and metal biomarkers in informal electronic waste (e-waste) recycling workers in Accra, Ghana. Workers (N = 58) participated in audiometric testing, a survey, blood collection, and personal noise dosimetry. Sixty percent of participants displayed audiometric notches indicative of noise-induced hearing loss (NIHL). Most workers (86%) reported high noise while working. Daily average noise levels were in the range 74.4–90.0 dBA. Linear regression models indicated participants who lived at Agbogbloshie Market for longer periods were significantly associated with worse hearing thresholds at 4 and 6 kHz. The models did not identify blood levels of lead, mercury, or cadmium as significant predictors of worse hearing thresholds or larger noise notches, but increased levels of selenium were significantly associated with better hearing at 6 kHz. Models of thresholds at 4 and 6 kHz were improved by including an interaction term between the maximum noise exposure and the level of zinc in whole blood, suggesting that zinc may protect hearing at lower noise levels, but not at higher levels. Further study of the relationships between elements, noise, and NIHL is needed.
Highlights
Worldwide, 466 million people are estimated to suffer from hearing loss (HL) and global prevalence is increasing [1]
Our study indicated that these workers had unexpectedly high noise exposures during both occupational and non-occupational periods
These elevated noise exposures could help explain the decrements in hearing threshold levels (HTLs) observed among workers through audiometric testing—average right ear thresholds at 4 and 6 kHz were >20 dB, which, in a group of workers as young as those assessed, is much worse than would be expected in a similar group of noise-free workers [55]
Summary
466 million people are estimated to suffer from hearing loss (HL) and global prevalence is increasing [1]. The prevalence of adult-onset HL in developing nations, a large portion of which is due to occupational noise [2], is increasing [3]. HL has profound impacts on human health and quality of life as well as a wide variety of adverse social, psychological, occupational, and educational outcomes [4]. Individuals with HL experience detrimental impacts on educational achievements and employment status, as well as challenges within the workplace [5,6]. Estimating the exact prevalence of NIHL is challenging as many individuals in the US either do not have access to, or do not give priority to, their hearing health, even when they would benefit from treatment. Three in ten US adults under age 35 with hearing impairment will obtain a hearing aid [8]
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