have longer employment. Lymphopoietic malignancies are of interest because human data indicate that inhaled insoluble uranium compounds accumulate in the tracheobronchial lymph nodes (Singh et al. 1987). The trend by duration of employment was in the positive direction for lymphopoietic cancers other than leukemia but was not significant.
Within the category of nonmalignant respiratory disease, there were excesses of emphysema (standardized mortality ratio [SMR], 1.96; 95% confidence interval [CI], 1.21-2.99; n = 21) and pneumoconioses and other respiratory diseases (SMR, 1.68; 95% CI, 1.26-2.21; n = 52). However, all non-malignant respiratory diseases and emphysema were inversely associated with duration of milling work.
There was a suggestion of an excess of deaths from chronic renal failure in the Colorado uranium-miller cohort for the period 1940-1998, when only the primary cause of death was examined (SMR, 1.35; 95% CI, 0.6-2.7; 8 observed, 5.9 expected). In support of a possible increase in risk was the trend with duration of uranium-milling employment (SMRs, 1.27, 1.33, and 1.53 for 1-2, 3-9, and over 10 y of employment, respectively). However, when multiple causes of death as given on a death certificate were examined, there was no excess (SMR, 1.05); and when the incidence of treated end-stage renal disease was evaluated with HCFA’s program data, there again was no excess (standardized incidence rate [SIR], 0.71; 95% CI, 0.26-1.65). A possible explanation for not finding significant effects is that renal exposures may have been low because the workers were exposed mainly to uranium compounds of low solubility.
From June 1943 to May 1947, the Tennessee Eastman Corporation (TEC) plant was engaged in the enrichment of uranium with the electromagnetic separation process. Polednak and Frome (1981) determined the mortality experience through 1974 of a cohort of 18,869 white men who worked at the TEC Y12 plant. A substantial number of the employees (8,345) worked in the chemical departments (code named alpha and beta to refer to stages in the electromagnetic separation process), where exposures were high. In the alpha departments, uranium trioxide was converted to enriched uranium tetrachloride. Those departments, which had the highest uranium concentrations, operated until September 1945. Thereafter, uranium hexafluoride from the Oak Ridge K-25 (gaseous-diffusion) facility was fed to the beta stage of the process. Before late 1945, uranium trioxide was received from Mallinckrodt Chemical Works and converted to uranium tetrachloride, but thereafter exposure to the insoluble oxides was partly replaced by exposure to the more soluble uranium hexafluoride and uranyl fluoride. Uranium hexafluoride was converted to the oxides uranium tetraoxide and uranium trioxide and then to “green salt” in the beta departments. Other toxic exposure in the workplace included exposure to phosgene gas, mercury, carbon tetrachloride, and trichloroethylene.