CXCL8 and chronic obstructive pulmonary disease: More recently, Jiag’s group has reported the positive correlation between urinary copper and the serum markers of chronic respiratory diseases (CRDs, including asthma, COPD, lung cancer, and emphysema), such as cytokines (IL-6, IL-8), and circRNAs in a case-control study (n = 101, 161; case vs. control).