Five-year cohort study: emphysematous progression of indium-exposed workers

Chest. 2014 Nov;146(5):1166-1175. doi: 10.1378/chest.13-2484.


Background: Dose-dependent adverse lung effects due to indium exposure have been reported in a cross-sectional study. This is a 5-year longitudinal cohort study of indium-exposed and unexposed workers, assessing indium exposure levels and its clinical lung effects.

Methods: From 2008 to 2011, a 5-year follow-up study was conducted on 40 unexposed and 240 workers formerly or currently exposed to indium at 11 factories. Indium exposure was assessed by serum indium (In-S) (μg/L). Lung effects were assessed by subjective symptoms, serum biomarkers, spirometry, and chest high-resolution CT scan. Effect biomarkers used were Krebs von den Lungen and surfactant protein D.

Results: Mean values of In-S, Krebs von den Lungen, and surfactant protein D among the workers exposed to indium at baseline declined during the 5-year follow-up by 29.8%, 27.2%, and 27.5%, respectively. Of the exposed subjects with In-S levels > 20 μg/L, 26.3% experienced emphysematous progression on high-resolution CT scan. Ninety percent (18 of 20) of workers with emphysematous progression during follow-up were current smokers at baseline, and a trend of increasing incidence of emphysematous progression at higher In-S levels was observed among the smokers (P = .005). Emphysematous changes among subjects with In-S levels > 20 μg/L were likely to progress, after adjusting for age, mean duration since initial indium exposure, and smoking history (OR = 10.49, 95% CI = 1.54-71.36).

Conclusions: Long-term adverse effects on emphysematous changes were observed. The results suggest workers exposed to indium with In-S levels > 20 μg/L should be immediately removed from exposure.

Publication types

  • Comparative Study
  • Multicenter Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Cross-Sectional Studies
  • Disease Progression
  • Female
  • Follow-Up Studies
  • Humans
  • Incidence
  • Indium / adverse effects*
  • Japan / epidemiology
  • Male
  • Middle Aged
  • Occupational Diseases / epidemiology*
  • Occupational Exposure / adverse effects*
  • Pulmonary Emphysema / chemically induced*
  • Pulmonary Emphysema / diagnosis
  • Pulmonary Emphysema / epidemiology
  • Pulmonary Surfactant-Associated Protein D / metabolism
  • Retrospective Studies
  • Spirometry
  • Time Factors
  • Tomography, X-Ray Computed


  • Pulmonary Surfactant-Associated Protein D
  • Indium