To estimate the necessity of air ions (AIs) as a natural source of atmospheric gaseous superoxide for mammalia the effect of air ion deprivation on mice and rats was investigated. Ambient air deionization inside an experimental acrylic glass cage (AGC) was performed by electrostatic field, built up by acrylic glass surfaces. Under these conditions, four hours after the animals were placed into the AGC, the concentration of negative AIs was not detectable, the concentration of positive ions was (mean +/- SD) 77 +/- 18 ions x cm-3. The negative and positive AI concentrations in identical silicate glass cages (control) were 482 +/- 128 ions x cm-3 and 660 +/- 148 ions x cm-3 respectively. It was found that the prolonged deficiency of AIs in ambient air leads to accelerated death of the animals. The life span of the deprived mice and rats was 16.2 +/- 0.9 and 23.0 +/- 1.1 days respectively. The pathological symptoms and ultrastructural changes in the adeno- and neurohypophysis in deprived animals observed strongly suggest that animal death is related to disturbances in neurohormonal regulation and pituitary insufficiency. The possible physiological need of AIs and atmospheric superoxide, and its role in the development of environmental stress in human beings and in particular in premature infants is discussed.