Smoking and COPD increase sputum levels of extracellular superoxide dismutase.
Regan EA, Mazur W, Meoni E, Toljamo T, Millar J, Vuopala K, Bowler RP, Rahman I, Nicks ME, Crapo JD, Kinnula VL. Smoking and COPD increase sputum levels of extracellular superoxide dismutase. Free Radic Biol Med. 2011 Aug 01; 51(3):726-32.