INS and type 2 diabetes mellitus: Though the pathogenic mechanism of air pollution on T2DM remains equivocal, it was suggested that toxic constituents of pollutants may play a crucial role in triggering oxidative stress and systemic inflammation, suppressing insulin signaling, and contributing to glycolipid metabolism disorder (Lucht et al., 2019; Sanjay Sanjay Rajagopalan and Brook, 2012).