Carbon tetrachloride and 1, 1, 2, 2-tetrachloroethane have a specific hepatotoxicity and belong to the most toxic agents among chlorinated hydrocarbons. The threshold limit value (TLV) of carbon tetrachloride by ACGIH is 10 ppm, and that of 1, 1, 2, 2-tetrachloroethane is 5 ppm. Therefore, it has been evaluated that the toxicity of carbon tetrachloride is lower than that of 1, 1, 2, 2-tetrachloroethane in the field of industrial hygiene. In order to examine the validity of this evaluation, the authors made Cb female mice weighing 20-23 g inhale the above vapors at 800 ppm for 3 hours separately, and attempted to compare the acute toxicity of carbon tetrachloride with that of 1, 1, 2, 2-tetrachloroethane, observing the course of the changes of lipid contents in the liver and plasma and the damage of liver microsomes after the exposure. The results obtained are summarized as follows: 1. The changes of hepatic triglyceride and phospholipid levels by the exposure to carbon tetrachloride were almost similer to those of 1, 1, 2, 2-tetrachloroethane. 2. The decreasing rate of plasma triglyceride and phospholipid contents by the exposure to carbon tetrachloride was significantly higher than those of 1, 1, 2, 2-tetrachloroethane. 3. The damage of liver microsomes was recognized in the exposures to both carbon tetrachloride and 1, 1, 2, 2-tetrachloroethane. As whole, it is concluded that the hepatotoxicity of carbon tetrachloride is almost the same as that of 1, 1, 2, 2-tetrachloroethane, or the former is a little higher than the latter.

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This study was designed with attention to the narcotic effect which is one of the effects of toluene on higher nervous functions. A, B and C groups of rats had been exposed respectively in 1, 000, 200, and 0 ppm of toluene for 8 hours per day for 25 weeks. In the experiment, each group was narcotized 5 times by inhalation of 20, 000 ppm of toluene. The durations of each inhalation were (1) 15 min. (2) 30 min. (3) 45 min. (4) 60 min. and (5) 75 min. in turn. The following facts were made clear by observations on the duration of convalescence and the mortality from narcotism. (1) In the duration of convalescence, there was no significant difference between three groups. (2) In the elongation of convalescence in accordance with the prolongation of inhalation, there were some significant differences between C and A or B groups. (3) In the mortality from narcotism after 5 times of inhalation, A and B groups were significantly higher than C group. (4) The rats which died at 5th inhalation required longer convalescence after 3rd and 4th inhalations than in the rats which survived at 5th inhalation. (5) There was no relation between the weight and the incidence of deaths or the duration of convalescence.

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In an attempt to objectively investigate the effect of TTFD (Thiamine Tetrahydrofurfuryl Disulfide) on fatigue of workers in high temperature environments in an iron works, a double-blind comparative study was made in summer, 1969. The experiment was designed on the basis of the results of a preliminary investigation carried out about one month before. The drugs used in the study were F25 tablets containing 25 mg of TTFD each and F50 tablets containing 50mg of TTFD each. These drugs and the placebo were used in the form of similar sugarcoated tablets which could not outwardly be distinguished. The workers were divided into two groups: one being administered F25 or placebo, the other F50 or placebo, and thus the crossover study was accomplished. Allocation was performed at random. In both the first term and the second term, the drug was administered for ten days, one tablet daily just before work and washout was carried out with the placebo for five days prior to each term of the administration. Fatigue was examined in terms of the flicker test, and in ten check items each of A and C of "Fatigue Scale of the Industrial Fatigue Research Committee of Japan Association of Industrial Health". The condition of fatigue was also examined according to five-graded score in order to investigate the relationship between the feeling of fatigue of workers and the characteristic values obtained in the examination. For both the first term and the second term, the examination was performed daily for eight days before and after work. By the use of the characteristic values obtained in the examination as described above the effect of the drugs was analyzed for the same subjects who worked at each comparison time of 1, 2 or 3; the data in the period during which F25 was given being compared with those in the period during which the placebo was given, and the data in the period during which F50 was given with those in the period during which the placebo was given. The conclusions thus reached are as follows: 1. The flicker test values obtained after work were higher when TTFD was given than when the placebo was given, with a statistically significant difference. In comparison of F25 with F50, the estimated effect of F50 was greater than that of F25. 2. In the analysis of the number of items complained out of the Fatigue Scale A, C and A+C, the number of workers without any subjective fatigue after work was more when F50 was given than when the placebo was given, with a statistically significant difference. 3. Correlations between: a) the condition of fatigue and the flicker test value, b) the condition of fatigue and the number of items complained out of the Fatigue Scale A, c) the condition of fatigue and the number of items complained out of the Fatigue Scale C were calculated in terms of Spearman's rank correlation coefficients and the sign test was carried out. Furthermore, exactly in the same way, the mutual correlations between i) the flicker test value, ii) the number of items out of the Fatigue Scale A, iii) the number of items out of the Fatigue Scale C were also calculated and the sign test was carried out. From the result of the sign test, a statistically positive correlations concerning the degree of fatigue was found between the condition of fatigue, the flicker test value, the number of items of the Fatigue Scale A or C. In other words, it was shown in many cases that when fatigue was indicated by any of the characteristic values, it was indicated by other characteristic values as well.

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Recently, there has been an increase in the number of workers complaining of low back pain. This is related to the changing patterns of work due to industrialization and automation which have been noted to increase the stress in workers' bodies. Inflexible regulations and attitudes on the part of governmental administration make it difficult to meet the changing needs and the working conditions of the workers. In 1968, a new regulation came into force, which states that low back pain without a history of trauma is admitted as an occupational disorder. However, such cases of low back pain as spondylosis deformans is likely to be attributed to advancing age, and spondylosis or spondylolisthesis would be considered as a congenital anomaly. Physical examinations and X-ray findings among construction workers in Okayama City revealed the following results: 1. Fortyfive percent of the workers complained of the low back pain. 2. Low back pain is related to the type of work performed. And, the worker's posture is related to the occurrence of the low back pain. 3. One third of the workers with low back pain reported a history of low back trauma. 4. Workers with low back pain showed a high incidence of other musculo-skeletal symptoms. 5. Disappearance of physical lordosis, punch tenderness over vertebrae, weakness of extension tendon of the big toe, positive Lasegue test and differences in patellar and Achilles tendon reflexes between both sides were more often observed among the workers with low back pain than among the workers without it. 6. Spondylosis, spondylolisthesis and spondylosis deformans were noted to have high incidence among the workers studied, particularly in the younger age groups. The findings described above indicate that physical and radiologic examinations verify that both trauma and chronic stress are related to the occurrence of the low back pain. We conclude that low back pain is related to the person's occupation. This raises some serious questions regarding the interpretation of the new regulation. There is a great need for additional investigations on low back syndromes.

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