This study involving BLM-induced pulmonary fibrosis mice and BLM-treated primary pulmonary alveolar epithelial cells suggests a model whereby the lipid peroxide produced by cyto •OH causes a shortage of GSH and heme, increases H2O2, and induces cellular senescence via the ATM/p-p53ser15/p21 and p-HRI/p-elF2α/ATF4/p16 pathways. Here, ATF4 is linked to pulmonary fibrosis.