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406 Japanese Indium Cohort Study: Five-Year Follow-up
  1. M N Nakano1,
  2. A Tanaka2,
  3. M Hirata2,
  4. N Yoshioka1,
  5. K Omae1
  1. 1School of Medicine, Keio University, Tokyo, Japan
  2. 2Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan


Background Since the demand for manufacturing flat panel display expands, we are ongoing an indium cohort study and followed up 310 indium exposure workers for 5 years to assess the changes on the lung effects.

Methods We conducted a baseline epidemiologic survey in 14 indium related plants between 2003 and 2006. A 5-year follow-up study was conducted in 11 of these 14 initial plants between 2008 and 2011. Follow-up rate is 57.2% (310/542). Indium concentration in serum (In-S) was determined as an exposure parameter, and effects on the lungs were examined. Some potential confounders were also checked. All participates were classified into three categories, non-, current, and former exposure, according to occupational history of indium exposure.

Results During the follow-up, intensive efforts for improvement of working environments were made in all 11 factories. In currently and formerly exposed workers, mean In-S and geometric means of interstitial biomarkers, KL-6 and SP-D, were significantly lower at follow-up than in the baseline study. In currently and formerly exposed workers, prevalence decreased by approximately 30% for KL-6 abnormalities but did not significantly decrease at all for FEV1.0/FVC, %FVC, or %FEV1.0 abnormalities. In the formerly exposed group, chest high-resolution computed tomography (HRCT) showed high prevalence of interlobular septal thickening and emphysematous change (15.1% and 26.7%, respectively). Aggravation of interstitial change on HRCT was not affected by In-S level, whereas that of emphysematous change progressed in a dose-response manner, even after adjustment for smoking and age. Workers with ≥In-S 20 µg/L had a greater risk of aggravation of emphysematous findings (AOR: 13.31; 95% CI: 3.29–53.89). During the 5-year-follow-up, two non-exposed worker at the baseline were diagnosed as lung and stomach cancers, and one currently exposed worker was diagnosed as renal cancer.

Conclusion Emphysematous changes might cause more chronic and longer-term lung effects than interstitial pneumonia.

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