Febrile attacks were noticed among workers employed in electric welding of galvanized iron pipe in the holds of a boat. Hygienic and medical studies on the work-environment and the workers themselves were carried out. An analysis of the atmosphere of the holds made during the welding revealed high concentrations of zinc oxide (145.7, 69.7 and 14.6 mg/m³) and dust (81.6 and 245.1 mg/m³) which were inversely proportional to the area (height × width) of the entrance of the hold. Febrile attacks occurred several hours after the close of the welding work. Most of the cases complained of fever and chill. The other complaints were arthralgia, general malaise, myalgia, irritation of the throat and discomfort in the chest, while others complained of nausea, vomiting and diarrhoea. Recurrence of the attack was characteristic in most of the cases. Patch tests for zinc oxide were positive in 2 out of 49 cases tested. From the above-mentioned results, it is concluded that these febrile attacks were metal fume fevers caused by inhaling zinc oxide. Besides, to see the effects of the metal dust on the lung roentgenographic and spirometric examinations were done. In about half of 66 welders, punctiform opacities in the lung field were observed, the size of which was smaller than that of those found in the usual pneumoconiosis. And, there was no evidence of disturbance of ventilatory functions.

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Strain difference of responses to acute and long-term benzene inhalations was investigated in male mice of CFW and ddN lines. Observed responses included mortality and lethal time by acute exposure to higher concentrations of benzene, and changes in leucocyte counts and hemoglobin levels after repeated inhalations of lower concentrations. Experiments and results are as follows. 1) Groups of mice aged 5, 7 and 10 weeks for both strains were exposed to 1.5% benzene and mortalities were observed. Mice of 5 and 7 weeks of age did not show any significant strain difference in mortalities. In 10 weeks old mice, however, mortality of ddN was significantly higher than that af CFW. When these data were so arranged that comparison of strains could be made at the same body weight levels instead of the age classes, a significant difference in mortality was found only in the heaviest group of mice, ddN being higher than CFW. 2) Mice of the both strains were exposed, at 10 weeks of age, to 3% and 2% benzene and lethal time was determined for each animal. Mean lethal time of ddN was shorter than that of CFW in both concentrations and the difference was statistically significant in the case of 2%. Variances of lethal time were significantly smaller in ddN than in CFW. 3) After 20-days exposure to 200 ppm benzene, leucopenia was found only in ddN, and a decrease of hemoglobin concentration, on the contrary, was observed in CFW and not in ddN. From these results, it was concluded that the susceptibility of adult mice to the inhaled benzene of higher concentrations was greater in ddN than in CFW, and its variance was smaller in ddN than in CFW. And, consequently, it was noted that ddN was more suited for studying acute response, such as mortality or lethal time, to benzene inhalation in mice.

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Investigations on sick absence was carried out on a nation-wide scale by the committee appointed for this purpose of the Japan Association of Industrial Health, as a part of which the present studies were conducted with special attention to the locality of Hokkaido. The survey covered 4, 329 employees of two factories, four mines and one transportation company for a period of four months, from June to September of 1964 as the summer season of Hokkaido. The emphasis was laid on the relationship between sick absence and the type of work shift, sickness of occupational or private nature, frequent absence and classification of diseases, excluding absence due to other than diseases or injuries and of longer duration than 180 days. On the basis mentioned above the following points were discussed: (1) incidence rate per 100 persons, (2) average duration of absence per person under observation (disability rate), (3) average duration of absence per case (severity rate), and (4) the relation between the incidence rate and number of days elapsed from holiday to absence. The results obtained were as follows: 1) Night-shift or over-night work showed a tendency of higher incidence rate, which will be one of important keys to health administration. 2) The average duration of absence per person was about 4 days in mines, which is almost the same as shown in the report on sick absence by Enterline (U.S.A., 1964). 3) Concerning the occupational nature of sick absence, a high incidence rate was observed in mines, especially in underground work. In addition, the fact that the average duration of absence per case in mines was rather long (about 20 days) should be taken into consideration in relation to safety management. 4) Regardless of the type of the industry, the highest incidence rate was seen on the first day after a holiday.

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It is still obscure why the workers exposed to nitroglycol suffer from a heart attack on Monday morning. As a preliminary study on the mechanism of nitroglycol poisoning, the authors carried out the experimental studies on the subacute toxicity of nitroglycol in animals. 1. Subcutaneous LD₅₀ of nitroglycol in mice was 869.4 mg/kg. 2. Ten male rabbits received daily subcutaneous injections of nitroglycol at about 300 mg/kg. All animals died within 9 days. Development of severe anemia with Heinz bodies of 70% and reticulocytes of 20% has been found in these rabbits. In other three rabbits copper sulphate (1mg of copper/kg) was injected at the same time with nitroglycol subcutaneously. Hematological findings of these rabbits were not different from those of the animals treated with nitroglycol only. 3. Two groups of mice, thirty males each, received daily subcutaneous injections of nitroglycol at 100 and 400 mg/kg respectively for 16 days, and the animals were sacrificed at 2, 4, 6, 9, 13 and 16th days. No significant anemia was noted in both groups. Appearance of Heinz bodies in erythrocytes of mice treated with 400 mg/kg of nitroglycol was about 60%, but that in mice with 100 mg/kg was scarce. Relative weights of liver and spleen to body weight of mice treated with 400 mg/kg of nitroglycol increased gradually with injections, but in the mice treated with 100 mg/kg only the spleen gained the weight slightly with injections. Weights of other organs showed a change (increase or decrease) temporarily at an early stage, but these recovered to the normal values during further successive administrations of nitroglycol. From these results, it may be said that daily subcutaneous injections of 100 mg/kg of nitroglycol for 16 days are tolerated by mice. 4. Total copper and ceruloplasmin levels in the plasma of mice and rabbits treated with nitroglycol increased at an early stage, but these returned gradually to the normal values in spite of daily injections of nitroglycol.

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