Reactive oxygen species as essential components of ambient air.

In this review evidence for the presence of the anion radical O2(-*) in atmospheric air is considered, and the biological activity of superoxide and negative air ions is compared. Various aspects of the biological effect of superoxide and other reactive oxygen species contained in air at the cell, tissue, and organism levels are discussed. The results of the therapeutic use of exogenous gaseous superoxide and low doses of H2O2 for the treatment of bronchial asthma, pain, and Parkinson's disease are reported. A hypothesis on the mechanism of physiological action of exogenous reactive oxygen species is discussed.