Analysis of the mortality patterns in an area supplying migratory tunnel workers 1. Regional differences in the mortality patterns

Abstract

Tunnel work, digging a tunnel at the face, is a highly specialized job today. Many tunnel workers migrate from one place to another away from home throughout the year. They are exposed to hazardous factors such as dust, vibration, noise and so on, working under the two 12-hour shift system. Recently it has been reported that many workers who had suffered from pneumoconiosis and/or vibration disease returned to their home areas. The southern part of Oita Prefecture is well known as being one of the areas which supply many tunnel workers. In order to study the long-term effects of tunnel work on the health of the tunnel workers, the authors compared the mortality rate in the district supplying many tunnel workers with that of the district supplying few workers. Nine causes of death were chosen among many as indices indicating the characteristics of the structure of mortality in the district supplying many tunnel workers. The authors estimated these causes of death in relation to sex and age, analyzing simple correlations between the 9 causes of death and 33 socioeconomic factors. A principal component analysis of these indices was also carried out. The results were as follows. A close relationship was found between tunnel work and three causes of death such as silicotuberculosis (010), tuberculosis (010-019, A 6), and infective and parasitic diseases (000-136). The other 5 causes of death such as diseases of the digestive system (520-577), neoplasms (014-259), all causes (000-999), stomach cancer (151, A 47) and pneumoconiosis (515) were related not only to tunnel work but also to other regional characteristics such as fishery workers rate. No relationship was found between tunnel work and death by cerebrovascular disease (430-438, A 85). These results show that the tunnel work has an influence on the structure of mortality in the area supplying these workers.