DDIT3 and chronic obstructive pulmonary disease: The toxic effects of Cd operate by disrupting normal cellular signaling pathways, particularly by activating the C/EBP-DDIT3 signaling pathway, inducing endoplasmic reticulum (ER) stress and inflammatory responses, damaging the normal functions of airway cells, and potentially leading to various pulmonary diseases such as chronic obstructive pulmonary disease (COPD) (Kim et al., 2017).