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--> 1 Study Rationale and Overview Rationale In July 1946, the United States conducted a test of atomic weapons code named Operation CROSSROADS. From then until the test ban treaty in 1963, the Department of Defense and earlier agencies conducted 235 nuclear detonations, involving at least 210,000 military participants—dubbed atomic veterans—in 19 test series. Fifty years later, scientists, veterans advocates, health and environmental advocates, military spokespersons, politicians, and veterans and their families debate whether and to what extent exposure to the nuclear tests affected the participants health. The mass media showed the world pictures of fall-out covered ships and personnel. Individual participants have published vivid accounts of their experiences (e.g., Bradley 1948). Many veterans have applied to the Department of Veterans Affairs for compensation for health problems and disability they attribute to radiation exposure (The Washington Post and Senator Rockefeller mention more than 3,000 claims by 1984, when hearings and legislation gave impetus to this study. Studies to date (e.g., Darby 1988, 1993; Watanabe, Kang, and Dalager 1994; Robinette 1985; Campbell 1995) both government-supported and veterans-advocate designed, have added to our understanding of mortality outcomes in atomic veterans, but none has specifically addressed the mortality of CROSSROADS participants.
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--> Congress has passed legislation and three presidents have signed three laws that address certain concerns of the atomic veterans.3 These allow for increased priority for medical care and some loosening of record standards for compensation purposes for specific, listed health conditions.4 In 1983, section 601 of PL 98–160 directed the Secretary of Veterans Affairs to contract with an unbiased, disinterested scientific group to study the mortality effects of atomic radiation on Operation CROSSROADS participants. The Institute of Medicine at the National Academy of Sciences was chosen. The Medical Follow-up Agency (MFUA) of the Institute of Medicine-National Academy of Sciences presents in this report the description and findings of the mortality study it has conducted since 1986. It compared the rates and causes of death of the approximately 40,000 military personnel who were present at Operation CROSSROADS with those of a reference group of personnel not exposed to those activities. Our charge has been to answer, using the best available information on exposure and mortality outcome, the focused question: Have CROSSROADS participants had more or earlier deaths from all causes and from various specific causes than did military personnel who are alike in all respects save CROSSROADS participation? While the report discusses a somewhat broader range of questions in light of its findings, it does not purport to answer such questions as: Does low-level radiation cause cancer? Did the United States act appropriately, from the perspectives of medical science, environmental hazard control, and ethics, in its design and conduct of nuclear tests and follow-up activities? At the sponsor's request, we have conducted detailed verification studies to ascertain the accuracy and completeness of the CROSSROADS participant list provided to us by the Defense Nuclear Agency (DNA). 5 In summary, this report will present data and findings about the mortality experience of CROSSROADS participants, discuss possible meanings of those findings, and suggest avenues of further study. It is outside the scope of our charter to determine what fiduciary responsibility anyone holds or should take for the health experience of those personnel. Those are questions that science alone cannot answer and this study will not address. 3 Public Law 98–542, January 1984; PL 100–321, May 1988; and PL 102–578, January 1992. 4 At the time of this report, federal statute requires the Secretary of Veterans Affairs to providepresumptive service-connected benefits to veterans with expert testimony of radiation exposure and one of the following diseases: leukemia (other than chronic lymphocytic leukemia), cancer of the thyroid, cancer of the breast, cancer of the pharynx, cancer of the esophagus, cancer of the stomach, cancer of the small intestine, cancer of the pancreas, multiple myeloma, lymphomas (except Hodgkin's disease), cancer of the bile ducts, cancer of the gall bladder, primary liver cancer (except if cirrhosis or hepatitis B is indicated), cancer of the salivary gland, and cancer of the urinary tract. VA regulations cover a few additional conditions for medical-care access. 5 In June 1996, the Defense Nuclear Agency was renamed the Defense Special Weapons Agency.
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--> Overview In this study, the basic comparisons are between CROSSROADS participants and non-CROSSROADS participants. The specifics of the study plan involve choice of comparison groups and choice of outcomes to study. This study is solely a mortality study; that is, we do not consider the incidence of nonfatal or not-yet-fatal diseases in this population. The analyses are based on deaths of CROSSROADS participants and individuals in various comparisongroups that occurred after the July 1946 tests through 31 December 1992. The initial overall health outcome comparisons are: all-cause mortality, all-cancer mortality, and leukemia mortality. The benefit of the first of these comparisons is its use of all the mortality information available on the participants. The drawback, too, lies in its broad scope. Our knowledge of radiation biology and earlier study findings suggested health effects on a narrower range of outcomes. In addition to these three disease groups, which will be used to test for CROSSROADS effects, we also look, descriptively, at 44 other disease categories6 that have been (a) identified in earlier studies of atomic veterans, (b) hypothesized to be radiogenic, (c) declared by statute or regulation to be radiogenic for purposes of federal veterans compensation programs, or (d) known to be of interest to atomic veterans. For two reasons, we do not include other reported or hypothesized radiogenic conditions, such as ophthalmic cataract, and dermatologic, immunologic, psychiatric, and reproductive conditions. First, this study's endpoint is mortality—chosen because such data are available and definable—and most of these other conditions do not consistently result in death. Second, a recent Institute of Medicine report lays out in detail reasons for not studying adverse reproductive outcomes in atomic veterans, their spouses, and children (IOM 1995). The participant group included all military personnel assigned to a unit and verified as being on site7 during the official operational period of CROSSROADS: 1 July 1946 through 31 August 1946. This report compares the participants' mortality with that of three types of reference groups: a military nonparticipant cohort, the U.S. male population, and mortality rates from other relevant published studies. 6 See Chapter 10 for details. 7 ''Onsite participation'' is defined in Federal Register Vol. 54, No. 118, 21 June 1989, page 26029.
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--> A military comparison group is considered the most closely comparable to the military participants. It includes men who served in the military at the same time, in the same types of military occupations and paygrades, and in similar settings as the participants, but who did not participate in Operation CROSSROADS. Whatever the unmeasured nonradiation risk factors the participants may have carried (e.g., behavioral, such as cigarette smoking; environmental, such as living on a ship; or demographic, such as education and income), the comparison group is likely to be equivalent, reducing the opportunity for biased study results. Comparison with the general U.S. male population is a useful adjunct to a military comparison group. Scientists and other readers of mortality studies are used to seeing U.S. rates and can weigh interpretation accordingly. A very large drawback to using U.S. population rates exists, however. The "healthy worker effect" or, in this case, the "healthy soldier effect" makes interpretation of these comparisons difficult; we discuss this in Chapter 3.
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