Abstract
In order to clarify the long-term effect of tunnel work on the health of its workers, we examined its cause-specific mortality pattern.
The subjects were 418 males who died after the age of 30 in 1977 in the southern part of Oita Prefecture, where many men come and work away from home as tunnel workers. Death certificates, 418 in number, presented to the health center were used to examine the causes of death. Occupational careers and life histories of the subjects were obtained by interviewing their families or relatives in 1980. The interviews were successfully carried out with 356 subjects (85.2%).
The subjects were divided into two groups. One group was consisted of 73 males who had engaged in the tunnel work (tunnel workers) and the other was of 283 males without experience of tunnel work (others). Proportional mortality ratio (PMR) and proportional mortality classified by age were compared between the two groups. The mean ages at death were also compared among these two groups and all Japanese males over 30 years of age.
The results were as follows.
1) The proportion of the deaths of “tunnel workers” among the total deaths in the area surveyed was correlated to the regional rate of tunnel workers and the distribution of pneumoconiosis due to tunnel work. These results show that many tunnel workers suffering from pneumoconiosis had returned to their home area before they died.
2) Excess deaths from the ICD category I; infective and parasitic diseases (000-136), tuberculosis (010-019) and silicotuberculosis (010) were found among the “tunnel workers.” These excess deaths covered a wide range of age. No excess was observed among the “others.”
3) The mean age at death of the “tunnel workers” was lower than that of the “others” and also that of all Japanese males.
4) A dose-response relationship was observed between the PMR for silicotuberculosis (010) of the “tunnel workers” and the duration of the tunnel work.
