Effect of Negative Air Ion in Human Electroencephalogram / 日本温泉気候物理医学会雑誌

ABSTRACT

High levels of negative ions have been detected in the air in forests, at spas, near waterfalls, and so forth, and there have been reported that they have a favorable effect on human beings' feeling of comfort and their feeling of fatigue. In this study we prepared an experimental room in which it was possible to maintain temperature constant at 25°C and constant humidity, and turn the supply of negative ions on and off, and in addition to assessing comfort level and fatigue level subjectively, we assessed them by means of the -wave component of the EEG, which indicates the degree of relaxation, and by auditory evoked potential P300, which reflects attentiveness and degree of fatigue.<br>Methods: The subjects were 15 healthy physicians and nurses. The experiment was conducted in a room maintained at a constant temperature of 25°C and a constant humidity of 50% during a 2-hour period on different days without informing the subjects of whether the air was loaded with negative ions or not. Constant temperature and humidity were maintained, and the level of negative ions was adjusted by using a shinki genertor (Geochto Ltd.). The parameters measured were determined with a flicker test and P300 (auditory evoked) test, and the α-wave ratio was calculated from the 60-minute closed-eye resting EEG.<br>Results: A higher percentage of subjects reported subjective comfort when the air was loaded with neagtive ions (6/15, 40%) than when it was not (4/15, 27%).<br>Significant difference was not observed in the P300 tests, but the α₂ (10-13Hz) ratio of the EEG and flicker test tended to be higher with negative ion-air than without nagative ion-air.