A historical prospective mortality study of workers in copper and zinc refineries

Earlier health studies of workers in electrolytic refinery operations have raised concern that workers may experience excess morbidity and premature death as a result of hazardous occupational exposures. This study was designed to determine if the refinery operation is associated with any excess mortality patterns. A cohort of 4,802 male workers exposed for at least one year during 1946-1975 was assembled from nine U.S. zinc and copper refineries. Vital status was ascertained for 4,241 (88%) of the cohort. Death certificates were obtained for 84% (355/423) of the deceased. Overall standard mortality ratios (SMRs) were calculated to be 92 for the cohort, 97 for the subgroup of copper refinery workers, and 83 for the subgroup of zinc refinery workers. Significantly high cause-specific SMRs were as follows: (1) cerebrovascular disease (CBVD) for the cohort; (2) all cancers, cancer of the digestive tract, and CBVD for the copper subgroup; (3) all cancers, cancer of the respiratory tract, and CBVD for one plant that demonstrated a significantly high overall SMR (133). The significant excess of cancer deaths among the study cohort is largely due to the plant that exhibited the significantly high overall mortality rate, but lack of smoking data qualifies this finding. The significant excess of CBVD seems to be consistent across plants and further research seems warranted to verify the finding.