Mortality among migrant tunnel workers.

To clarify the mortality pattern of migrant tunnel workers, a retrospective cohort study was conducted in the southern part of Oita Prefecture, which is well known as a source area for tunnel workers. This study was made on 1,078 tunnel workers and 943 non-tunnel workers who were observed for 8 years and 6 months from January 1975 to June 1983. The overall SMR of tunnel workers was 162 which was statistically significant. The SMRs for pulmonary tuberculosis (SMR = 3,267), industrial accidents (SMR = 1,000), and pneumoconiosis (SMR = 26,000) which were all closely related to tunnelling work were extraordinarily high and statistically significant. Mortality from lung cancer was considerably higher among tunnel workers than among non-tunnel workers. The results of ratios of observed to expected deaths by age-group showed significant excess mortality in three age-groups: 40 to 49, 50 to 59, and 60 to 69. These findings show that migrant tunnel workers have serious health problems. On the other hand, in non-tunnel workers, the overall SMR was 89. No significant excess mortality was observed for any cause of death or any age-group.