GSR and chronic obstructive pulmonary disease: Patients with BS-COPD (n = 30) and CS-COPD (n = 30, ex-smokers) had higher plasma levels of malondialdehyde (MDA) and increased activity of superoxide dismutase (SOD) compared to unexposed healthy controls (n = 30), with no significant differences in glutathione peroxidase (GPx), glutathione reductase (GR), and glutathione-S-transferase (GST), indicating a similar pattern of oxidative stress [150].