A cluster of cases of lymphoma in an underground colliery

An apparent occupational outbreak of cases of non-Hodgkin's lymphoma among the employees of an underground colliery on the NSW south coast has been investigated. The employment register of the mine recorded that 1004 men had worked at the colliery from its opening in 1946 until December 31, 1986. In this period, this cohort of men had amassed 18,818 person-years. A person-years analysis of the mortality and morbidity of cancer showed a standardized incidence ratio for non-Hodgkin's lymphoma of 3.27 (95% confidence interval [CI], 1.31-6.74) and for Hodgkin's disease of 7.27 (95% CI, 1.98-18.59). All of the cases of non-Hodgkin's lymphoma were diagnosed after 1978. An excess of cases of cancer of the salivary gland also was present (standardized incidence ratio, 10.00; 95% CI, 1.21-36.10). The method of coal extraction, the geology and chemistry of the coal-seams that were mined and the general characteristics of the work-force at the colliery are similar to those at other collieries in the region. Furthermore, an exhaustive work-place environmental study at the colliery has failed to identify any plausible carcinogenic agent to which the findings of this study can be attributed. Coal-miners previously have not been shown to be at a greater risk of developing lymphoma or related malignancies, and the region in which the mine is located has lower prevalence rates of non-Hodgkin's lymphoma and Hodgkin's disease than does New South Wales as a whole.