Exposure to hardly soluble indium compounds in ITO production and recycling plants is a new risk for interstitial lung damage.

OBJECTIVES

To identify the effects of indium on the lung and to assess exposure-effect and exposure-response relations between indium exposure and effects on the lungs.

METHODS

Ninety three male indium exposed and 93 male non-exposed workers from four ITO manufacturing or ITO recycling plants were analysed in a cross-sectional study. Indium in serum (In-S) was determined as a biological exposure index. Geometric means (GSD) of In-S were 8.25 ng/ml (4.55) in the exposed workers and 0.25 (2.64) in the non-exposed workers. The maximum concentration of In-S was 116.9 ng/ml. A questionnaire for respiratory symptoms and job histories, spirometry, high-resolution computerised tomography (HRCT) of the chest, serum KL-6, serum SP-A, serum SP-D and serum CRP were measured as the effect indices.

RESULTS

Spirometry, subjective symptoms and the prevalence of interstitial or emphysematous changes on lung HRCT showed no differences between exposed and non-exposed workers. Geometric means (GSD) of KL-6, SP-D and SP-A in the exposed workers were 495.4 U/ml (2.26), 85.2 ng/ml (2.02) and 39.6 ng/ml (1.57), and were significantly higher than those in the non-exposed workers. The prevalence (%) of the exposed and non-exposed workers exceeding the reference values were also significantly higher in KL-6 (41.9 vs 2.2), SP-D (39.8 vs 7.5), and SP-A (43.0 vs 24.7). Very sharp exposure-effect and exposure-response relations were discovered between In-S and KL-6 and between In-S and SP-D when the exposed workers were classified into seven groups by In-S.

CONCLUSIONS

The study outcomes with regard to the basis of serum immunochemistry biomarkers and HRCT indicate that exposure to hardly soluble indium compound dust may represent a risk for interstitial lung damage.