It should be kept in mind that a number of gaseous and particulate pollutants in our atmospheric environment will primarily affect the small airways in the lungs possibly causing an insidious development of its obstruction. The present review is presented in the hope that it may prove helpful in understanding a unique mechanical property of the small airways. A special emphasis is laid on the fact that an early, partial obstruction of the small airways can not be detected by such routine methods for ventilatory capacity as spirometry and respiratory resistance measurement. Recent research works to develop techniques sufficient to detect functionally the obstruction of small airways and their application in the field of environmental health are reviewed.

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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.

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Recently the finance of the Japanese National Railways (JNR) is in the red because of its unreasonable management and insufficient subsidy from the government. The authority of JNR has developed a drastic reduction of workers by force as one of measures for solving the finance problems, causing many serious problems on working condition among the workers of JNR.
There are many research projects and study reports about working conditions of drivers, while there are very few reports concerning other workers. The author studied on the working condi-tions of conductors on board of cabooses who have their responsibility for many kinds of job like adjustment, examining train, verifying instrument, management after accidents on and off train and so on.
The results are as follows :
1. They had many physical, mental and social complaints resulting from evening and night work, which had disrupted the daily living pattern such as disturbance in eating and sleeping habits.
2. High prevalence of gastro-intestinal disorders were observed in their past histories though they were relatively young.
3. About forty percent of them reported that they had been affected with abdominal pains on train, and more than eighty five percent of their injuries resulted from receiving shocks on train. These injuries were mainly burns, scratches and contusions caused by shocks due to abrupt stopping of the train or acute change in the speed.
4. They pointed out that many of the present working conditions needed improvements, especially with respect to shift systems, construction of cabooses, and safety and health measures.

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