Concomitant with frequent occurrence of disorders of the neck, arm, hand and low back among assembly-line female workers in confectionery work, there is an increased number of patients with occupational cervicobrachial disorders and/or low back pain. In suspicion of the close correlation between the working conditions and development of these local disorders, a field study was undertaken. The following are the results obtained.
1) More than 90% of these assembly-line female workers consisted of inexperienced part-time employees, mostly of middle to old age.
2) They were engaged in decorating conveyor-carried cakes with cream and chocolate. The work necessitated repetitive movements of the upper limbs and concentration of visuosensory and nervous attention in a half-sitting slouching posture. This was considered to exert excess load on the local muscles and nervous and sensory systems.
3) The causes that intensified the local symptoms as pointed out by the workers consisted of (1) repetitive use of the arms and hands, (2) static posture during the work and (3) sustained standing position. Complaints of low back pain were conspicuous from the unsuitable height of a conveyor-belt.
4) Thirty five percent of the female workers needed medical treatment for cervicobrachial and/or low back pain.
5) The forced adaptation to the belt height, sustained unnatural working posture and the imposition of forced movements seemed to be the main factors in the onset of cervicobrachial and/or low back pain in interrelation with working hours.
On the basis of these results, the work load on a machine-paced assembly-line was analyzed and the necessity of improvement of working conditions was discussed.

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Somatosensory evoked responses (SERs) to mechanical stimulation were recorded in 5 patients with occupational vibration disease and 10 grader drivers, and the results were compared with those obtained from 48 normal subjects.
SERs were recorded at room temperature of 20-23°C and after immersing the hand in hot (40°C) or cold (10°C) water for 5 minutes. SERs were also recorded while depressing the brachium and soon thereafter to examine the effect of ischemia. The following results were obtained.
1) In SERs recorded on the finger of patients with occupational vibration disease, it was observed that some peaks of SERs were absent in 6 out of the 10 cases and that peak latency time was abnormally prolonged in 3 out of them. On the other hand, in SERs recorded on the forearm, abnormality was observed in only 1 out of them.
2) In recording SERs in 6 patients with occupational vibration disease after immersing the hands in hot water, it was observed that abnormal SERs became normal in all 6 cases. However, these normalized SERs became abnormal in 5 out of the 6 cases within 25 minutes after removing the hands from hot water.
3) No appreciable change could be observed in SERs recorded after immersing the hands in cold water.
4) Partial absence of SER peaks could be observed in 2 out of 9 grader drivers while depressing the brachium. On the other hand, all SERs in 7 normal cases did not show any abnormality while depressing the brachium.
5) The results suggest the presence of a close relationship between peripheral vascular dysfunction and peripheral somatosensory disturbance in patients with occupational vibration disease. However, it was observed that peripheral vascular dysfunction could not always trigger peripheral neural dysfunction.
6) These findings have led to the conclusion that SERs to mechanical stimulation are more useful in the diagnosis of dysfunction of the peripheral nerve in patients with occupational vibration disease than SERs to electrical stimulation. The findings suggest that immersion in hot water and cold water and depression of the brachium are useful sensory tests for patients with occupational vibration disease and grader drivers.

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Migrant workers known in Japanese as “dekasegi” refer to workers who migrate seasonally from their town of residence to areas where work is readily available.
The eastern part of Toyama Prefecture is well known as a source of migrant workers who engage in jobs associated with dust exposure such as tunnel projects. Most of these workers suffered from silicosis.
A total of 695 migrant workers suffering from silicosis who had underwent health screening between 1977 and 1982 were followed until the end of 1983. For cases of death, the cause and date of death were individually confirmed on the basis of death certificates. Based on these data, the person-years of risk and cause-specific mortality rates were calculated. The mean person-years of risk per person was 4.7.
During this period of observation, there were 75 deaths among these silicosis patients, giving a mortality rate of 23.0 per 1, 000 person-years of risk. When classified by the Japanese roentgenographic category of pneumoconiosis, the mortality rate was 10.5 for category 1, 21.3 for category 2, 38.6 for category 3 and 49.3 for category 4. The mortality rates of categories 3 and 4 were significantly higher than those of categories 1 and 2.
The highest cause-specific mortality rate among silicosis patients per 1, 000 person-years was 5.2 for malignant neoplasms followed by 3.7 for pulmonary tuberculosis, 3.1 for both cardiovascular diseases and pneumoconiosis, and 2.8 for pneumonia and bronchitis.
High mortality rates in the 50-69 age group were found among silicosis patients belonging to categories 3 and 4. By cause of death, the mortality rates of all malignant neoplasms (especially lung cancer), pulmonary tuberculosis, and cerebrovascular diseases were relatively high in this age group. In the 70-89 age group, the mortality rate of those belonging to categories 2, 3 and 4 was high and by cause of death the mortality rates of pneumoconiosis, pulmonary tuberculosis, all malignant neoplasms (especially lung cancer), cardiovascular diseases and pneumonia and bronchitis were high.
The mortality rates of silicosis patients with abnormal findings in %VC, FEV₁% and AaDO₂ by pulmonary function tests tended to be higher than those of silicosis patients without such abnormalities.

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