Vibration of chain saws and bush cleaners widely used in Hokkaido was measured at the handle of these machines to evaluate the degree of the effect of vibration on machine operators. And then, subjective symptoms of operators were surveyed. An electro-vibrometer was used for the vibration measurement, with an electrodynamic pickup for vibration amplitude measurement and with a barium titanate pickup for accerelation measurement and frequency analysis. Table 1 and 2 show the results of the vibration measurement at various conditions of engine operation, and Fig.1 shows the results of the frequency analysis. Most of the values of vibration amplitude exceeded allowable limits of vibration as proposed by Miura and used in the Soviet Union. Sixty nine chain saw operators and 18 bush cleaner operators were questioned with regard to Raynaud's phenomenon and other complaints. These operators had short experience in the machine operation, i.e. 87% of the chain saw operators had experience less than 4 years and the other 4∼7 years. Experience of bush cleaner operators was about 1 year. Complaints of Raynaud's phenomenon at fingers were found in 10 of chain saw operators (occurrence rate 15.6%) and in 2 of bush cleaner operators (11.1%). Numbness feeling at fingers and hands were found in 30 of chain saw operators (46.9%) and in 7 of bush cleaner operators (38.9%). Pains at hands and fingers were found in 25% of the operators. These symptoms occured more frequently at the right hand than at the left. The author recognized that these symptoms were caused by the vibration of the machines. As a conclusion, widely used chain saws and bush cleaners have harmful effects causing vibration disease at the fingers and hands of operators, as, in fact, was foud among the operators.

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An investigation with our simplified Cornell Medical Index (CMI), which was previously reported, jointly with Awazi-Okabe's thinking-version test and several kinds of clinical examinations, was carried out on 203 male shift workers. Their health conditions were estimated by the number of items answered "yes" on CMI and by the nature of each item related to the somatic system. The roentgenological sign and the result of the test of gastric juice were used for the close examination of the gastric function, and according to the results of these examinations, it was explained that their somatic complaints were based on clinical signs. And in so far as they had some complaint without any clinical sign, some abnormality was found on the close examination. These observations have made certain that our simplified CMI was one of useful methods in the practice of screening at periodic health examinations. An inverse correlation was found between the number of items answered "yes" on CMI and the score of thinking-version scale. It was shown that the workers characterized with introversion had much complaints.

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The concentration of mercury in head hair obtained from a man, who is suspected to have been exposed to mercury vapours and inhaled it, was determined by a method of non-destructive activation analysis based on the detection of the 68 Kev X-rays and 77 Kev Gamma-rays of 65-hour ¹⁹⁷Hg. About 100 mg of hair, cut to equal length and at the same distance from the scalp at the same part of the head every month for seven months, was washed to be got rid of surface contamination with either a nonionic detergent or organic solvents, followed by rinsing with distilled water. After neutron irradiation of the sample in HTR reactor for 5 hours in a thermal neutron flux of about 1×10¹²n/cm²-sec, followed by cooling for 5 days to decrease short-lived contaminating activities, mercury was determined by direct gamma-ray spectrometry. Results from the hair samples showed that the concentration of mercury decreased monotonically from 20.4 ppm to 4.6 ppm. On the other hand, results from samples obtained from a group consisting of seven individuals who had shared similar diets with the man above stated and another group of twelve individuals belonging to the other groups showed a significant difference between the man inhaling mercury vapours and these groups. Namely, the range of the concentration of mercury of these groups was from 1.9 ppm to 6.2 ppm. By the non-destructive activation analysis of head hair, it is able to deal with more cases in a shorter period. Detectable limit is 0.07 ± 0.02μg, and the necessary minimum quantity of hair is enough below 50 mg. It is necessary to care in obtaining hair, because mercury is very tightly bound to the hair and not easily removed by washing.

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