Biomarkers for Lung Epithelium Injury in Occupational Hexavalent Chromium-Exposed Workers

Objective: To evaluate whether Club (Clara) cell protein (CC16) and surfactant-associated protein D (SP-D) can be used as biomarkers for lung injury caused by chromium exposure. Methods: The concentrations of chromium in the air (CrA), chromium in the blood (CrB), lung function, CC16, SP-D, tumor necrosis factor-alpha (TNF-alpha), and interleukin-6 (IL-6) were detected in 91 chromium-exposed workers and 38 controls. Results: In chromium-exposed group, the levels of CrA, CrB, SP-D, TNF-alpha, and IL-6 were significantly higher, whereas forced expiratory volume in one second (FEV1), FEV1/FVC, maximal expiratory flow (MEF), maximum ventilation volume (MVV), CC16, and CC16/SP-D were lower. Negative correlations were shown between CC16, SP-D or CC16/SP-D, and CrB or inflammatory cytokines (TNF-alpha and IL-6). Positive relationships were shown between CC16 or CC16/SP-D with indicators of lung function. Tobacco smoking and chromium exposure had synergic effects on lung injury. Conclusions: CC16, as an immunosuppressive protein, and CC16/SP-D can be used as sensitive and noninvasive biomarkers for lung injury. Smoking should be banned in chromium workplaces.