Noise-induced hearing loss in Korean workers


A new study carried out in Korea has shown that workers exposed to heavy metals and organic solvents in association with noise have higher pure tone averages than unexposed workers. Noise-exposure is a well-documented risk for hearing loss in an occupational setting. Several studies in the last few years have provided evidence that coexposure to ototoxic chemicals and noise may potentiate hearing loss.

To assess the possible link between coexposure and hearing loss, Korean researchers from the Department of Preventive Medicine, Gachon University School of Medicine, and from the Occupational Safety and Health Research Institute in Incheon, examined nationwide data on 30,072 workers in a wide range of industries from the Korea National Occupational Health Surveillance 2009 survey. Organic solvent exposure was considered for toluene, isopropyl alcohol, and/or xylene, and heavy metal exposure was considered for lead, cadmium, mercury, chrome, and/or manganese.

The study looked at subject data on industry-based exposure such as occupational noise and exposure to heavy metals and organic solvents, and at subject-specific health outcomes, specifically audiometric examination results with computation of pure-tone averages (PTAs). Noise exposure at work was based on the daily 8-hour time-weighted average. A multivariate linear statistical model was used and results showed that increments in PTAs with occupational noise were 1.64-fold and 2.15-fold higher in individuals exposed to heavy metals and organic solvents, respectively, than in unexposed individuals.

Possible limitations of the study cited by the authors include the fact that occupational organic solvent and heavy metal exposure were classed as exposure or not (with no data available on actual measured levels), and absence of data on potential confounding factors such as smoking or exposure to non-occupational noise at home or in the recreational sphere.

Source: Choi YH, Kim K. Noise-induced hearing loss in Korean workers: co-exposure to organic solvents and heavy metals in nationwide industries. PLoS One. 2014 May 28;9(5):e97538.