Analyses of Combined Mortality Data on Workers at the Hanford Site, Oak Ridge National Laboratory, and Rocky Flats Nuclear Weapons Plant

Abstract

An important objective of studies of workers exposed occupationally to chronic low doses of ionizing radiation is to provide a direct assessment of health risks resulting from this exposure. This objective is most effectively accomplished by conducting combined analyses that allow evaluation of the totality of evidence from all study populations. In this paper, combined analyses of mortality in workers at the Hanford Site, Oak Ridge National Laboratory, and Rocky Flats Nuclear Weapons Plant are presented. These combined analyses provide no evidence of a correlation between radiation exposure and mortality from all cancer or from leukemia. Of 11 other specific types of cancer analyzed, multiple myeloma was the only cancer found to exhibit a statistically significant correlation with radiation exposure. Estimates of the excess risk of all cancer and of leukemia, based on the combined data, were negative. Upper confidence limits based on the combined data were lower than for any single population, and were similar to estimates obtained from recent analyses of A-bomb survivor data. These results strengthen support for the conclusion that estimates obtained through extrapolation from high-dose data do not seriously underestimate risks of low-dose exposure, but leave open the possibility that extrapolation may overestimate risks.

Mortality among workers in a thorium-processing plant--a second follow-up.

“…Their SMR values for all causes (SMR 0.74), all cancers (SMR 0.53), and circulatory diseases (SMR 0.66) were all significantly below those of the general US female population. These low SMR values were generally consistent with results reported in other studies of workers who have been exposed occupationally to low levels of external radiation (23,(26)(27)(28)(33)(34). The healthy worker effect might be one of the reasons for the low SMR values.…”

“…The SMR values for cancers of the stomach, rectum, bone, prostate, lymphosarcoma, and Hodgkin's disease were all greater than one , but none of them was statistically significant. By combining mortality data on workers at the Hanford Site, Oak Ridge National Laboratory, and Rocky Flats Nuclear Weapons Plant, Gilbert et al (33) found no evidence of a correlation between radiation exposure and mortality from all cancers or from leukemia. Of the 11 other specific types of cancers analyzed, they found that multiple myeloma was the only cancer with a statistically significant correlation with radiation exposure .…”

Epidemiology of Accidental Radiation Exposures

“…The statistical power of individual studies was, however, low and in most cohorts the confidence intervals of the risk estimates were compatible with a range of possibilities, from negative effects to risks an order of magnitude greater than those on which current radiation protection recommendations are based. Combined analyses of data from some of these studies have therefore been carried out at the national and international levels (4,5,(55)(56)(57) specifically to test the adequacy of existing risk extrapolations. Table 2 presents the results of the International Agency for Research on Cancer (IARC) international combined analyses (5), carried out on 96,000 workers, and compares them to estimates obtained from IARC reanalyses of the atomic bomb survivors data.…”

The association betweeen cancers and low level radiation: An evaluation of the epidemiological evidence at the Hanford Nuclear Weapons Facility

“…For radiosensitive tissues, particularly multiple myeloma and leukemia, only multiple myeloma was consistently associated with low level radiation at Hanford (3,5,(7)(8)(9)(11)(12)(13). In the trend tests multiple myeloma continually showed a positive trend, or increases in mortality with increased exposure.…”