Determinants of lung cancer risk among cadmium-exposed workers

Workers at a cadmium recovery plant in Globe, Colorado, showed an increased risk of lung cancer, which some investigators have attributed to cadmium exposure. We conducted a cohort mortality analysis of this work force and a case-control analysis of the lung cancer cases within this work force in order to assess the probable causes of the lung cancer excess. The Globe plant began as a lead smelter about 1886, switched to arsenic production in 1920, and became a cadmium metal production facility in 1926. Cadmium, arsenic, and cigarette smoking are three potential lung carcinogens found in this workplace. Industrial hygiene data collected from 1943 onward served as the basis for the National Institute for Occupational Safety and Health (NIOSH)-derived exposure algorithm that assigned cadmium exposure estimates to employees based on their work area in the plant and calendar time. Few exposure data existed for substances other than cadmium. Feedstock ore concentrations were used as a surrogate measure of air arsenic levels. The arsenic content of the fines used as feedstock prior to 1940 was considerably higher than that of the fines used after 1940. Smoking histories had been obtained previously for 45% of the workers. A case-control analysis of the 25 cases of lung cancer known to have occurred among these workers through 1982 was conducted using three controls per case, matched by closest data of hire and age at hire. Potential causal agents for lung cancer included cadmium exposure, cigarette smoking, and arsenic exposure. Exposure variables for each case and control included estimated cumulative cadmium exposure in milligram-years per cubic meter, cigarette smoking history, and plant arsenic exposure status at the time of hire. Estimated cumulative cadmium exposures of cases and controls did not differ overall or within the date-of-hire strata. Cases were more than eight times more likely to have been cigarette smokers than were controls. Lung cancer risk in this workplace was more closely related to the period of hire, not to the cumulative cadmium exposure. The period of hire appears to be a surrogate for arsenic exposure as related to feedstock. The measures used here seem to indicate that exposure to arsenic and cigarette particulates, rather than to cadmium particulates, may have caused the increased rate of lung cancer of these workers.