Mortality patterns among uranium enrichment workers at the Portsmouth gaseous diffusion plant, Piketon, Ohio.
In 1992, the National Institute for Occupational Safety and Health (NIOSH) received a Congressional request to conduct an update study of mortality at the Portsmouth Gaseous Diffusion Plant in Piketon, Ohio. The plant enriches uranium by increasing the proportion of the uranium-235 isotope (235 U) using a gaseous diffusion process. This report presents the methods and findings of the study. Specifically, this report addresses: 1) the use of available employment records to assemble a cohort of gaseous diffusion workers; 2) the use of existing health physics and industrial hygiene data to reconstruct past occupational exposures to selected physical and chemical agents; 3) a survey of electromagnetic field exposures to the contemporary workforce; 4) the overall mortality experience of the workers compared to that of the general population; 5) the cause-specific mortality experience of the workers by degree of occupational exposures using: a) individually measured alpha count activity in urine (resulting from exposure to soluble uranium), b) personal dosimetry for exposure to external (gamma and X ray) ionizing radiation, and c) estimated historical occupational exposures to chemical compounds of uranium, nickel, and fluorine. Overall mortality at the facility was significantly less than expected [SMR = 0.72; 95% confidence interval (CI) = 0.67 - 0.76] as was mortality from "All Cancers" [SMR = 0.82; CI = 0.73 - 0.92]. Statistically non-significant excesses of mortality were found for some specific causes of death including cancers of the stomach and of the lympho-hematopoietic tissue, both of which had been noted in an earlier NIOSH study at this facility. Epidemiologic evaluation of the data to detect trends in risk of death after radiation/chemical exposures was performed in nested case control and sub-cohort analyses. Analyses of possible relationships between cause of death and external radiation produced the same results as those resulting from the analysis performed upon the full cohort. A statistically non-significant elevated SMR for cancer of the stomach was present similar to that observed in the overall analysis. Non-significant excesses of deaths were observed due to diseases of the arteries, veins and pulmonary circulation; and due to diseases of the musculoskeletal system and connective tissue. No dose-response relationships were observed for cancers of the stomach, lung, Hodgkin's disease, lymphoreticulosarcoma, and all cancers combined. The analyses of possible relationships between cause of death and internal radiation exposure produced essentially the same results observed in the total cohort and for external radiation. Analyses of possible relationships between cause of death and exposures to fluorine and fluoride compounds, uranium metal, and nickel for the respective sub-cohorts working in departments where airborne concentrations for these agents were measured failed to reveal any dose-response relationships. Temporal effects, effect modification and interaction, confounding by concomitant occupational exposures and risk factors such as age, race and gender were also examined. No patterns were identified for any of these exposures or factors. Statistically non-significant excesses of deaths due to cancers of the stomach were again noted in the sub-cohorts restricted to departments with measured airborne concentrations of fluorine and fluoride compounds and metallic uranium. Evidence for and against associations of mortality and occupational factors were evaluated and are presented and discussed. No statistically significant excesses in mortality were identified even though extensive efforts were taken to utilize contaminant exposure information, latency periods, and appropriate comparison groups. Reasons for the lower than expected mortality experienced by this cohort and the limitations of the study are discussed. Recommendations are made for future studies at the site. The limitations of exposure monitoring data collected for compliance purposes in epidemiologic studies are discussed. Recommendations are made to expand exposure monitoring so that future epidemiologic study results can be more specific. These recommendations include more inclusive monitoring programs based on statistical sampling principles and more complete documentation of reasons for monitoring certain areas or groups
Heavy-metals; Heavy-metal-poisoning; Radiation-hazards; Radiation-injury; Electromagnetic-fields; Electromagnetic-energy; Electromagnetic-radiation; Mortality-rates; Stomach-cancer; Gastrointestinal-system-disorders; Hematopoietic-system; Lymphatic-system-disorders; Lymphatic-cancer; Cardiovascular-system-disorders; Cardiovascular-system-disease; Cardiopulmonary-system-disorders; Cardiopulmonary-system; Age-factors; Racial-factors; Sex-factors; Region-5