In our study, apocynin and Sim significantly increased the expression of E-cad, while decreased the expressions of TGF-β1, α-SMA and Vimentin in lung tissues, suggesting that Sim could alleviate the silica-induced lung fibrosis by inhibiting NOX-derived ROS production and reducing TGF-β1-induced EMT process. This evidence concerns the gene ACTA1 and pulmonary fibrosis.