The production of indium-tin oxide has increased wing to the increased manufacture of liquid-crystal panels. It has been reported that interstitial pneumonia occurred in two indium-processing workers; therefore, the present study aimed to evaluate whether interstitial pulmonary disorders were prevalent among indium workers. The study was carried out in 108 male workers in the indium plant where the two interstitial pneumonia patients mentioned above were employed, and included high-resolution computed tomography (HRCT) of the lungs, pulmonary function tests and analysis of serum sialylated carbohydrate antigen KL-6 and the serum indium concentration. Significant interstitial changes were observed in 23 indium workers on HRCT and serum KL-6 was abnormally high (>500 U.mL-1) in 40 workers. Workers with serum indium concentrations in the highest quartile had significantly longer exposure periods, greater HRCT changes, lower diffusing capacity of the lung for carbon monoxide and higher KL-6 levels compared with those in the lowest quartile. The serum indium concentration was positively correlated with the KL-6 level and with the degree of HRCT changes. In conclusion, the results of the present study indicated that serum KL-6 and high-resolution computed tomography abnormalities were prevalent among indium workers and that these abnormalities increased with the indium burden, suggesting that inhaled indium could be a potential cause of occupational lung disease.
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