The authors have identified the cause of an accident which occurred during the excavation work of a tunnel in a National Highway costruction in an area of Wakayama Prefecture to be a high concentration of CO₂ and a marked O₂ deficit in the air of the accident site. Furthermore, the mechanism of the O₂ deficit and the generation of the high concentration of CO₂ has been deduced to be such that the geological characteristics of the particular stratum called Itogawa-Butsuzo Line passing the site of the tunnel excavation were acting as a main factor, and that the physical and chemical actions of the shale absorb O₂ and discharge CO₂. Itogawa-Butsuzo Line is a well-known geological structural line like the Central Structural Line passing southwestern Japan and Mikabu Line. The danger of incidence of such an accident as stated above is, therefore, conceivable in this area and other areas having such a structural line. And, sufficient precautions must be taken for a construction work in such a stratum of the earth, or such a structural zone should be avoided as much as possible by a scrupulous geological survey before the construction. It is absolutely necessary to conduct complete ventilation in the tunnel during the excavation if the excavation in sush a stratum is unavoidable. As hygienic management measures, the personnel in charge of health supervision in such a construction site ought to be supplied with the necessary instruments, reagents, and birds ready for detecting various gases at regular intervals in order to guard against the disaster. The authors deeply acknowledge various assistances ext5ended by Wakayama Labor Standard Bureau from the outset of our investigation, the help of the Industrial Science Laboratory of Kao Soap Co., Ltd. which took up the precision gas analysers, and the kind advice given to our geological investigation by Mr. Tsutomu Iwahashi, Assistant Professor of the Geological Laboratory, School of Education of Wakayama University.

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In an automobile factory, the concentration of toluene in the air and the content of hippuric acid in the urine of workers working in a shop where toluene is used was estimated by paperchromatography and Pagnotto's. method. Workers, after spraying toluene dissolved in the paste on the ceiling of driver's seat pasted plastic board on it. Average toluene density acting on the worker was calculated from the toluene density at the driver's seat and the actual working time on that seat by time study. Average density at which the toluene was inhaled was also calculated from the urinary hippuric acid content by the use of the line indicating their relationship as reported before. The results obtained were as follows. 1) There was a tendency that the toluene density decreased as the room temperature dropped in winter. 2) Excretion of the urinary hippuric acid taken at midday was more than that at the beginning of the work, and at the maximum at the end of the work. 3) Toluene density as well as urinary hippuric acid content in this shop decreased in 1965 compared to those in 1964, because air conditioning apparatus had been set at the beginning of 1965. 4) Toluene density to which workers were exposed was in accordance with the inhaled toluene density calculated from the urinary hippuric acid of workers. 5) A high correlation between urinary hippuric acid concentrations obtained by Ogata and Nagao's DAB method and Pagnotto's method seen at the level over 1 mg/ml of H.A.

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Investigations on sick absence, the summer data (1964) of which had been reported in part one of the studies, was continued for one year. The winter data thus obtained are compared in this report with those of the summer. Observations in Hokkaido were analysed from the viewpoint of frequent absence, classification of diseases, and the difference of occupations, in comparison with those of all Japan. The following results were obtained. 1) Incidence rates per 100 persons per year in the factory (scale 1) and mine (scale 2) were almost the same as those of all Japan in both scales (scale 1: less 500 employees, scale 2: 500-1, 000 employees), while in the transportation industry (scale 3: more than 1, 000 employees) showed a very low rate of about one third of that of all Japan. (Fig. 5) 2) Incidence rate per month was higher in winter than that in summer in all Japan, while in Hokkaido there was no difference in the factory (scale 1) and it was lower in winter than in summer in mines (scale 2) and transportation (scale 3). Considering the severe winters of Hokkaido, this observation is very interesting. (Fig. 6) 3) According to the distribution (%) of diseases as a cause of absence, VIIIa (common cold) and XIb (gastro-intestinal diseases) were the most frequent, approximately one third of all diseases were common colds. These tendencies were almost the same as those of all Japan. (Fig. 7) 4) Attention shold be put on the fact that XVII (occupational accident) especially XIII (diseases of the bones and organs of movement) was high in incidence in the mine. Health and safety management must be promoted further. (Fig. 7) 5) In the distribution of absentees by number of absence per year, those of six times or more were as high as 10% in the factory. When the incidence and severity rates are taken into consideration, it is recognized that there were many persons of frequent absence of short duration in the factory. The highest was absence of once a year, being 55% in the mine and 70% in the transportation. The rate decreased in inverse proportion with the increase of absence frequency. (Fig. 8)

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Many efforts have been made to find the best way of diagnosing Raynaud's phenomenon of occupational origin, but so far it has not been successful. The previous paper described the findings related to the recovery of the skin temperatures of the fingers having been exposed to the cold water for a short time, and the results as to the skin temperatures at the end of the 5-minute-immersion of hands in the cold water. The results of these examinations, however, were not satisfactory for diagnosing the phenomenon precisely. This paper presents an experimental study of the skin temperatures of the fingers during immersion of hands in the cold water for ten minutes. The average skin temperatures every one minute after the sixth minute of 10-minute-immersion were observed, since it was found that some cases had an initial fall or a gradual fall in the skin temperatures in the first five minutes and all cases had the skin temperature stabilized after the sixth minute. The results obtained from the workmen suffering from the phenomenon were compared with those from 10 healthy male subjects, which is defined here as the standard skin temperature (SST). In the water at 10°C the skin temperature of the workmen suffering from the phenomenon showed a tendency to be a little lower than SST. In the water at 5°C it was further lower than SST. Skin temperatures of 8.8°C (M-σ or the mean value less by one standard deviation obtained in the health subjects) or less were observed in many of the workmen suffering from the phenomenon, and those of 7.0°C (M-2σ) or less were observed in those suffering severely from the phenomenon. Consequently, measurement of the skin temperature of the hand immersed in the water at 5°C is considered appropriate for diagnosing the phenomenon. Besides, by immersion in 5°C water the 4 workmen suffered severely from the phenomenon and showed blanching of the fingers with their skin temperatures of 5.0-5.6°C.

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The method of the estimation of the mercury vapor by means of the atomic absorption phtometry has been refined. The instrument for the analysis is very stable and can easily indicate from 0.007 to 2.00 μg mercury with reliable accuracy.

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