SOD1 and chronic obstructive pulmonary disease: In exhaled breath condensate of COPD patients, increased levels of ethane, H2O2, malondialdehyde (MDA), 4-hydroxynonenal (HNE), or 8-isoprostane have been measured compared to smokers without COPD and healthy non-smokers,68, 69, 70, 71 whereas the levels of antioxidants glutathione (GSH), superoxide dismutase (SOD), and GSH peroxidase (GSH-PX) are reduced.72