A Study of Mortality and Morbidity Among Persons Occupationally Exposed to ⩽50 mSv in a Year: Phase I, Mortality Through 1984

A retrospective follow-up study is in progress of mortality and morbidity among persons who reportedly received greater than or equal to 5 rem [50 millisieverts (mSv)] of penetrating ionizing radiation in any calendar year of employment at all facilities operated for the U.S. Department of Energy (DOE) or its predecessor agencies. The purpose is to identify any adverse health outcomes and to determine if any such outcomes are related to prior occupational radiation exposure at these facilities. A population of 3145 present and former civilian employees at DOE facilities and at the U.S. Navy's Nuclear Reactor Propulsion Program (NRPP) who meet the radiation exposure criteria were identified from personnel radiation monitoring records maintained at the facilities for the years 1943 through 1978. Vital status through 1984 was determined for 86.6 percent of this population; 588 deaths (18.6%) were observed. The median career external radiation dose for individuals in the population through 1978 was 153.4 mSv, with a collective dose of 718.0 person-Sv. The median duration of follow-up was 20 years, with a total of approximately 69,000 person-years. Using comparable age/race/gender groups in the U.S. general population as the standards, mortality through 1984 was examined for all white males (N = 2392) and for two subcohorts of this group for whom vital status was known for more than 90 percent: black males (N = 131), and other males for whom no race data were available (N = 280). The remainder of the population comprised 25 females and 317 persons for whom race and gender data were unavailable. The overall mortality experience of the total white male cohort was consistent with a healthy worker effect. Standardized mortality ratios (SMRs) for all causes of death combined (SMR = 0.88) and diseases of the circulatory (SMR = 0.78) and digestive (SMR = 0.52) systems were statistically significantly decreased. Mortality due to all cancers combined was similar to that of the comparison group (SMR = 1.09). There were no statistically significant differences in mortality due to cancers of the major organ systems, including those strongly associated with exposure to high levels of radiation in other populations. Mortality increases observed for non-Hodgkin's lymphoma (SMR = 2.26) and all lymphatic malignancies combined (SMR = 1.46) were not statistically significant. Three of the five deaths in the “other lymphatic malignancy” category were due to multiple myeloma; there were no deaths due to Hodgkin's lymphoma, malignant bone disease, or cancer of the thyroid gland. Lung cancer mortality (SMR = 1.09) was as expected. No significant deviations in mortality experience were observed within the two white male subcohorts nor in the other race/gender groups evaluated, except that there were no deaths due to leukemia in either of the white male subcohorts. Further analyses and follow-up of this population are dependent on the research interests of the responsible agencies.