In line with the notion that EcSOD plays a critical role in the first line of defense against superoxide generation in the lung tissue, acute loss of EcSOD in adult mice (inducible EcSOD−/− mice) causes a dramatic increase of mortality with ALI/ARDS even in ambient oxygen although global EcSOD−/− mice are viable and tolerate exposure to ambient oxygen levels without difficulties. The gene discussed is SOD3; the disease is acute respiratory distress syndrome.