Abstract
BackgroundNoise exposure is a well-known contributor to work-related hearing loss. Recent biological evidence suggests that exposure to ototoxic chemicals such as organic solvents and heavy metals may be additional contributors to hearing loss. However, in industrial settings, it is difficult to determine the risks of hearing loss due to these chemicals in workplaces accompanied by excessive noise exposure. A few studies suggest that the effect of noise may be enhanced by ototoxic chemicals. Therefore, this study investigated whether co-exposure to organic solvents and/or heavy metals in the workplace modifies the risk of noise exposure on hearing loss in a background of excessive noise.MethodsWe examined 30,072 workers nationwide in a wide range of industries from the Korea National Occupational Health Surveillance 2009. Data on industry-based exposure (e.g., occupational noise, heavy metals, and organic solvents) and subject-specific health outcomes (e.g., audiometric examination) were collected. Noise was measured as the daily 8-h time-weighted average level. Air conduction hearing thresholds were measured from 0.5 to 6 kHz, and pure-tone averages (PTA) (i.e., means of 2, 3, and 4 kHz) were computed.ResultsIn the multivariate linear model, PTA increment with occupational noise were 1.64-fold and 2.15-fold higher in individuals exposed to heavy metals and organic solvents than in unexposed individuals, respectively.ConclusionThis study provides nationwide evidence that co-exposure to heavy metals and/or organic solvents may exacerbate the effect of noise exposure on hearing loss in workplaces. These findings suggest that workers in industries dealing with heavy metals or organic solvents are susceptible to such risks.
Highlights
Work-related hearing loss is a critical issue in workplace safety and health
The Korea National Occupational Health Surveillance (KNOHS) estimated that 64,974 Korean workers in 7,394 industries were exposed to a daily occupational noise $80 dB and that 77% of them had hearing loss (PTA . 25 dB in one or both ears) in 2009
The age-adjusted mean of occupational noise exposure was high at 88.665.3 decibels of ambient noise (dBA), which is unsurprising considering that participants were originally collected from the industries with problematic noise levels
Summary
Work-related hearing loss is a critical issue in workplace safety and health. The U.S National Institute for Occupational Safety and Health (NIOSH) and the occupational safety and health community designated hearing loss as one of the 21 priority research areas in the 21st century [1]. Evidence accumulated over recent decades suggests that exposure to neurotoxic chemicals is an additional contributor to occupational hearing loss. Several workplace studies suggest that such solvents are associated with an increased risk of hearing loss [17,18,19,20,21,22]. Recent biological evidence suggests that exposure to ototoxic chemicals such as organic solvents and heavy metals may be additional contributors to hearing loss. This study investigated whether co-exposure to organic solvents and/or heavy metals in the workplace modifies the risk of noise exposure on hearing loss in a background of excessive noise
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