title: Noise-induced hearing loss in Korean workers: co-exposure to organic solvents and heavy metals in nationwide industries.
abstract: BACKGROUND
  Noise 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.
  
  
  METHODS
  We 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.
  
  
  RESULTS
  In 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.
  
  
  CONCLUSIONS
  This 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.
authors.affiliation: Department of Preventive Medicine, Gachon University Graduate School of Medicine, Incheon, Korea.
authors.forename: Yoon-Hyeong
authors.initials: YH
authors.lastname: Choi
authors.affiliation: Occupational Safety and Health Research Institute, Korea Occupational Safety and Health Agency, Incheon, Korea.
authors.forename: KyooSang
authors.initials: K
authors.lastname: Kim
mesh_terms: D006317:Hearing Loss, Noise-Induced / Q000453:epidemiology* / Q000209:etiology*; D006801:Humans; D007221:Industry; D016014:Linear Models; D016015:Logistic Models; D019216:Metals, Heavy / Q000633:toxicity*; D009623:Noise, Occupational / Q000009:adverse effects*; D016273:Occupational Exposure; D009930:Organic Chemicals / Q000633:toxicity*; D056910:Republic of Korea / Q000453:epidemiology; D012997:Solvents / Q000633:toxicity*
chemical_list: D019216:Metals, Heavy; D009930:Organic Chemicals; D012997:Solvents