We found that the increased IGF2 expression in AT2s within the alveolar epithelium caused by exposure to NB for 3 months was sustained even after NB withdrawal for 2 months (see Supplementary Fig. 3, Additional file 3).These results suggest that chronic NB exposure leads to sustained IGF2 signaling activation, which contributes to the development of COPD and lung tumors. Here, IGF2 is linked to chronic obstructive pulmonary disease.