An experimental study was carried out to obtain physiological data substantiating the maximum allowable concentration of aceton gas in industrial hygiene. For this purpose it was intented to detect polygraphically the variations of physiological functions of the autonomic nervous system of man evoked by exposure to 250-270 ppm or 500-750 ppm concentration of aceton gas for 6 hours, with 1 hour free from aceton gas exposure in the middle, that is, from 9 : 00 to 12 : 00 a.m. and from 1 : 00 to 4 : 00 p.m. Subjects consisted of volunteers of 24 healthy male students (age; 18-28), which were devided into 3 groups (group of control of 8 students, group of low concentrations of 9 students, and group of high concentrations of 9 students, 2 of them being duplicated). They were individually examined while resting in bed for 6 hours (Tests for about 1 hour were repeated 6 times with pauses in between) a day for consecutive two days, and exposed to the aceton gas on the 2nd day except the control. Spontaneous variations and evoked variations in response to 1 second or 30 second auditory and visual incitements by “The Sound and Photo Stimulator for EEG” were observed throughout the experiment, but only the variations during the last 1 hour of both days were compared individually. On the other hand, the tendency of the variations and of the correlations between the phenomena in each group were compared between the 3 groups. The results thus obtained are as follows :
1) Galvanic skin reflex
Spontaneous GSR after repeated stimuli decreased in the gas groups, while evoked GSR with repeated 30 sec. stimuli increased in the 250-270 ppm group. The latter phenomenon would probably be derived from both effects of the aceton gas and the high air temperature of the examination room. The evoked GSR with repeated 1 sec. stimuli and latent time of the reaction to 1 sec. stimuli showed no difference between three groups. Tendency of correlation between GSR and air temperature in the gas groups differed from that in the control group.
2) Reflection photoelectric finger plethysmogram
Vasoconstrictive reaction and latent time of the reaction to stimuli and patterns of plethysmogram showed no difference between three groups. But, tendency of correlation between vasoconstrictive reaction to 30 sec. stimuli and air temperature in the gas groups differed from that in the control group.
3) Period of heart beat
Period of heart beat in the 500 ppm group shortened, while that in the control group lengthened. Tendency of correlation between the period and air temperature in the gas groups differed from that in the control group.
4) Period of respiration
Period of respiration showed no difference between the three groups. But, tendency of correlation between the period and air temperature in the gas groups differed from that in the control group.
5) Cerebral activity from occipital electroencephalograph
Cerebral activities in the gas groups rised in comparison with the control group. Tendency of correlation between the cerebral activity and air temperature in the gas groups differed from that in the control group.
6) It was concluded that the aceton gas influenced not only the spontaneous GSR, the period of heart beat and the cerebral activity, but also the correlations between the physiological functions of the autonomic nervous system, air temperature and the cerebral activity.
7) From these facts it is a matter of course that the MAC of aceton gas must be lowered to the level below 250 ppm.