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--> 2 Other Studies of the Human Health Effects of Radiation Exposure Human physical health effects of radiation fall along a continuum that includes immediate death, shortened lifespan due to radiogenic cancers such as leukemia, increased morbidity due to radiogenic conditions such as cataracts or nonfatal cancers, no discernible effect, and, in the view of some, beneficial physiologic response. U.S. military personnel exposed to nuclear weapons tests did not receive radiation in amounts that would be immediately lethal. The questions we addressed in this mortality study of atomic veterans concern the long-lasting, difficult-to-prove effects of lower levels of radiation that can result in increased incidence of cancer. This study looks specifically at exposed veterans. Other studies, not reviewed here (NRC 1990, UNSCEAR 1994, Shigematsu et al. 1995), have examined associations of radiation and health outcomes in groups defined by widely varying sources of radiation (for example, occupational, environmental, medical, and acts of war). Reports from individual veterans and advocacy groups brought to attention concerns about mortality and long-term morbidity believed to be caused by the radiation exposures received during nuclear weapons testing. The leadership of the National Association of Atomic Veterans (NAAV) and Trinity Post 7–45 have collected data and testified passionately about such increased illness. The NAAV Medical Survey Data Base (see Appendix A) had information (as of 28 January 1995) on 167 deaths among the 1,263 Operation CROSSROADS participants known to NAAV. Of the 379 death certificates NAAV gathered from participants in any U.S. nuclear test (not only CROSSROADS), about 75
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--> percent are from cancer (Campbell 1994). That appears unusually high, since national data show malignant neoplasms accounting for about 30 percent of male deaths in each 10-year age span covering deaths between ages 45 and 74. About 13 percent of years of potential life lost before age 65 is attributed to cancer deaths (NCHS 1992). In 1976, following notice of a patient who associated his acute myelocytic leukemia with his presence at an atmospheric nuclear test, the Centers for Disease Control mounted an epidemiological study of military personnel who had attended that test—Shot SMOKY, a detonation of Operation PLUMBBOB—conducted at the Nevada test site in August 1957 (Caldwell et al. 1980, 1983). Findings of increased leukemias among participants generated concern that their health may have been adversely affected by participation in the atmospheric testing program. An extensive study of participants at five test series (chosen to represent a range of testing circumstances) was conducted by the Medical Follow-up Agency of the National Academy of Sciences (now within the Institute of Medicine) to pursue that hypothesis (Robinette et al. 1985). In 1989, the Defense Nuclear Agency informed MFUA that the data DNA had provided—and on which all MFUA analyses were based—incorrectly identified members of the participant cohort. DNA's initial estimate of the error was larger but, after detailed review, the congressional Office of Technology Assessment (OTA) estimated that approximately 15,000 names should have been but were not on the participant roster and another approximately 4,500 were wrongly included on the participant list (Gelband 1992). The total number of participants in that 1985 study was 49,148. MFUA (with support and concurrence from the OTA, the General Accounting Office, and congressional and Department of Defense staff) decided that the published study results (Robinette et al. 1985) should be withdrawn from discussion pending reexamination of the data and correction for possibly substantial errors in participant group identification. At the request of DNA, MFUA is redoing the Five Series Study with the more complete data. Results from the newer study are not expected before the end of 1997. Other formal epidemiologic studies have not revealed distributions of rates that clearly confirm or refute radiation-caused mortality and long-term morbidity. Watanabe et al. (1995) compared military participants at Hardtack I, a 1958 U.S. test series in the Pacific, with a military comparison group. All-cause mortality (relative risk 1.10; 95% confidence interval 1.02–1.19) and digestive cancer mortality (RR 1.47; 1.06–2.04) mortality was higher among the Hardtack participants, but excess rates were not observed in deaths from all cancers, leukemia, or other hypothesized radiogenic cancers. The authors described the patterns of increased (and decreased) rates, but stopped short by neither concluding there were increased risks nor ruling them out. Darby et al. (1993) studied mortality and cancer incidence in military participants of United Kingdom nuclear weapons tests and found no "detectable
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--> effect on expectation of life or on subsequent risk of developing cancer or other fatal diseases." Although participants had significantly higher leukemia rates than controls, the authors attribute that to an abnormally low rate among the controls rather than to a radiation-associated high rate among the participants. That both the control and the participant groups had fewer cancers than expected based on general U.K. population rates (even after controlling for social class) is presented to support that interpretation. The standardized mortality ratio (standardized to the U.K. population) for leukemias in the control groups was 0.56 for the entire follow-up period and 0.34 for the time period 2 to 25 years postexposure. The results of this study of CROSSROADS participants and the earlier mentioned Five Series Study simultaneously under way should add more information about, and therefore a more stable understanding of, the association between nuclear test participant exposure and mortality. These studies are constructed carefully to include appropriate comparison groups and to avoid known biases (operational as well as conceptual) in the data collection and analysis, and, finally, in their interpretation.
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