Early changes in clinical, functional, and laboratory biomarkers in workers at risk of indium lung disease.

Abstract

Occupational exposure to indium compounds, including indium-tin oxide, can result in potentially fatal indium lung disease. However, the early effects of exposure on the lungs are not well understood. To determine the relationship between short-term occupational exposures to indium compounds and the development of early lung abnormalities. Among indium-tin oxide production and reclamation facility workers, we measured plasma indium, respiratory symptoms, pulmonary function, chest computed tomography, and serum biomarkers of lung disease. Relationships between plasma indium concentration and health outcome variables were evaluated using restricted cubic spline and linear regression models. Eighty-seven (93%) of 94 indium-tin oxide facility workers (median tenure, 2 yr; median plasma indium, 1.0 μg/l) participated in the study. Spirometric abnormalities were not increased compared with the general population, and few subjects had radiographic evidence of alveolar proteinosis (n = 0), fibrosis (n = 2), or emphysema (n = 4). However, in internal comparisons, participants with plasma indium concentrations ≥ 1.0 μg/l had more dyspnea, lower mean FEV1 and FVC, and higher median serum Krebs von den Lungen-6 and surfactant protein-D levels. Spline regression demonstrated nonlinear exposure response, with significant differences occurring at plasma indium concentrations as low as 1.0 μg/l compared with the reference. Associations between health outcomes and the natural log of plasma indium concentration were evident in linear regression models. Associations were not explained by age, smoking status, facility tenure, or prior occupational exposures. In indium-tin oxide facility workers with short-term, low-level exposure, plasma indium concentrations lower than previously reported were associated with lung symptoms, decreased spirometric parameters, and increased serum biomarkers of lung disease.