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Executive Summary Radiation dose reconstruction is the process of estimating radiation doses that were received by individuals or populations at some time in the past as a result of particular exposure situations. This report is concerned with dose reconstructions for military personnel—atomic veterans—who participated in various activities during atmospheric testing of nuclear weapons at the Trinity site in New Mexico, at the Nevada Test Site (NTS), and in the Pacific in 1945-1962, or who were prisoners of war in Japan or were stationed in Hiroshima or Nagasaki, Japan, after the atomic bombings of 1945. The types of ionizing-radiation exposures received by military personnel depended on characteristics of the detonations, the roles of the participants, and the proximity of personnel to detonations and fallout of nuclear debris from each detonation. Few of the hundreds of thousands of military participants were close enough to the locations of shots to receive exposures from gamma rays or neutrons produced directly by a detonation. Most radiation doses to military personnel in the continental United States, the Pacific, and Japan were due to exposure to beta- and gamma-emitting fission and activation products produced by nuclear-weapon detonations and to plutonium that did not undergo fission. Possible radiation exposures of military personnel during the atomic testing program have been of concern since the middle 1970s. Efforts to develop a program of dose reconstruction for atomic veterans began in the late 1970s, and a compensation program for atomic veterans whose diseases might have been caused by radiation exposure began in the early 1980s. The Defense Nuclear Agency (now the Defense Threat Reduction Agency, DTRA) was designated as the responsible Department of Defense (DOD) agency
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to assess radiation exposures of atomic veterans. Science Applications Incorporated (now Science Applications International Corporation, SAIC) has held a contract to perform dose reconstructions for military personnel almost since the inception of the Nuclear Test Personnel Review (NTPR) program. SAIC eventually teamed with JAYCOR, which is responsible for confirming each veteran’s status as a participant in the testing program and developing background information for estimating exposures to the veterans, such as detailed records of activities of veterans’ units at the NTS or in the Pacific. From the inception of the dose reconstruction and compensation programs, the responsibilities of DTRA and the Department of Veterans Affairs (VA) have been different. DTRA is responsible for confirming service status, estimating doses to participants, and reporting doses to VA; VA is the primary avenue of contact for the veterans and is responsible for determining eligibility for compensation. In April 1998, the Senate Committee on Veterans Affairs held a hearing that focused on radiation issues concerning the efficacy of current legislation governing compensation benefits for radiation-exposed veterans. The hearings highlighted the controversy about the use of dose reconstruction as a tool for determining veterans’ eligibility for benefits. In August 1998, the Senate committee asked the General Accounting Office (GAO) to review available information related to dose reconstruction to determine its reliability for measuring veterans’ radiation exposures and to assess the completeness of historical records that are used to assign radiation doses. GAO completed its review in January 2000 and found that although dose reconstruction is a valid method of estimating veterans’ doses for compensation claims and no better alternative was identified, the program lacks an independent review process. In December 2000, in response to GAO’s findings, the National Research Council was asked to review the DTRA dose reconstruction program, and the present committee was formed for this purpose. The committee was charged by Congress to conduct a review that included the random selection of samples of doses reconstructed by DTRA to determine Whether or not the reconstruction of the sample doses is accurate. Whether or not the reconstructed doses are accurately reported. Whether or not the assumptions made regarding radiation exposure based on the sampled doses are credible. Whether or not the data from nuclear tests used by DTRA as part of the reconstruction of the sampled doses are accurate. The committee was asked to make recommendations, if appropriate, on a permanent system of review of the DTRA dose reconstruction program. To address the questions posed in the committee’s statement of task summarized above, it is important to understand the capabilities and limits of historical dose reconstruction in general. Dose reconstruction can be a complex, tedious, and intensive undertaking, and there often is substantial uncertainty in estimates
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of dose to individuals. In the present context of adjudicating claims, it is also important to have some knowledge of the history of the atomic-veterans compensation program and the laws, regulations, and objectives that guide it. The public laws and regulations governing compensation for atomic veterans have changed over the last two decades. And, there have been advances in the science and tools available for the conduct of dose reconstruction and for administering the program. Those changes are reflected in changes to the dose reconstruction process noted by the committee during its review. The various laws governing the dose reconstruction and compensation programs are implemented in Title 38, Code of Federal Regulations, Part 3 (38 CFR Part 3). Those regulations authorize the VA to provide medical care and pay compensation benefits to confirmed test participants and their dependents and to pay indemnity compensation to some survivors. Under 38 CFR 3.309, the so-called presumptive regulation, veterans who are confirmed participants and experience any of 21 specified cancers are eligible to receive compensation regardless of their radiation exposures. Under 38 CFR 3.311, the nonpresumptive regulation, a dose assessment is used to evaluate whether a veteran’s disease was at least as likely as not to have been caused by radiation exposure during the atomic-testing program. In accordance with the policy set forth in 38 CFR 3.102, a veteran is to be given the benefit of the doubt if his1 participation cannot be definitely confirmed when the nonpresumptive regulation is applied. Most important, veterans are to be given the benefit of the doubt in the estimation of their doses. That requirement led to the policy of the NTPR program that estimates of doses to atomic veterans should include an upper bound that is intended to represent at least a 95% confidence limit or that the dose estimates themselves should be sufficiently “high-sided” that they represent an upper bound. Thus, the goal of the NTPR program is that there should be only a small chance (no more than 5%) that an upper bound or “high-sided” estimate of dose to an atomic veteran is lower than the true dose. The committee’s report addresses all aspects of the process of dose reconstruction for atomic veterans, including how the estimated doses are used in the compensation program for the veterans. The committee is fully cognizant of the importance of the dose reconstruction program and of the controversies about the feasibility and value of dose reconstruction in the compensation program. During the 25-year existence of the NTPR program, there have been significant improvements in the scientific foundations of dose reconstruction and in the tools that can be used to estimate doses and evaluate uncertainty. Many of these improvements are discussed in this report and are reflected in the committee’s findings and recommendations on specific technical issues related to methods of dose reconstruction used in the NTPR program. The committee 1 Masculine pronouns are used throughout this report, as needed; fewer than 1% of the participants were female.
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recommends that the improvements be evaluated and incorporated into the NTPR program in a timely manner. That does not mean that methods of dose reconstruction for atomic veterans need to be changed each time a new piece of information becomes available, but there must be deliberate and periodic efforts to evaluate changes in data and methods of dose reconstruction and to incorporate improvements into the dose reconstruction process as warranted. The committee recognizes that many improvements have been made in the NTPR program since its inception, and it recognizes the challenge confronting DTRA and VA associated with the need to use records and data that are incomplete and often difficult to piece together to reconstruct historical doses and make decisions about compensation to thousands of veterans who were exposed decades ago. Peer review of the methods of dose reconstruction and the availability of a detailed procedures manual, with proper procedures for document control and updating, are important. Most of the committee’s effort in reviewing the program of dose reconstruction for atomic veterans was directed at the first part of the statement of task concerning whether doses to atomic veterans estimated by the NTPR program are “accurate.” Because dose reconstruction is not an exact science, the committee has interpreted the question to be whether uncertainty in estimating dose has been appropriately addressed in dose reconstructions and whether credible upper bounds of doses to atomic veterans have been obtained. That interpretation is consistent with the policy of giving the veterans the benefit of the doubt in reconstructing their doses and with the intent of the NTPR program that the dose reports provided to VA for use in evaluating claims for compensation include upper bounds (95% confidence limits) of uncertain doses. In addressing the issue, the committee conducted a detailed review of 99 randomly selected dose reconstructions for individuals and many other documents of the NTPR program, including unit dose reconstructions for participant groups, documents describing methods of calculation and databases used in dose reconstructions, and documents describing participant activities and other conditions at various atomic tests. On the basis of its review, the committee reached the following conclusions related to all aspects of the process of dose reconstruction for atomic veterans: The methods used to estimate average doses to participants in various military units from external exposure to gamma rays, on the basis of exposures measured by film badges worn by participants or by field survey instruments, and from external exposure to neutrons, on the basis of established methods of calculation, are generally valid. However, because the specific exposure conditions for any individual often are not well known, many participants did not wear film badges during all possible times of exposure, and the available survey data used as input to the models often are sparse and highly variable, the resulting estimates of total dose for many participants are highly uncertain.
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Upper bounds of doses from external exposure to photons often are underestimated, sometimes considerably (for example, by a factor of 2-3), particularly when reconstructed doses are based on field survey data and uncertain assumptions about an individual’s locations and times of exposure, as opposed to being based on film-badge data. Upper bounds of doses from external exposure to neutrons are always underestimated—by a factor of about 3-5, depending on the value of the neutron quality factor assumed in a dose reconstruction—because of neglect of the uncertainty in the biological effectiveness of neutrons relative to gamma rays in all calculations. However, few participants received significant doses from exposure to neutrons. Doses to the skin and lens of the eye from external exposure to beta particles are claimed by the NTPR program to be upper bounds (“high-sided”) because they are based on multiplying a presumed upper-bound external gamma dose by a calculated beta-to-gamma dose ratio, which also is presumed to be “high-sided.” However, upper-bound gamma doses based on a reconstruction are often too low, as noted above, and the beta-to-gamma dose ratios are not evidently “high-sided” in all cases. In addition, the committee found no evidence in the 99 reviewed files that estimates of beta dose to skin include the dose due to contamination of the skin, for example, by means of adhering dirt particles. That probably was an important exposure pathway for many participants at the NTS because of the substantial dust in areas of participant activity at many shots. Methods used to estimate inhalation doses are highly uncertain and subject to potentially important sources of error because of the lack of relevant air monitoring or bioassay data, and most uncertainties and sources of error have not been evaluated by the NTPR program. Nonetheless, in some exposure scenarios, the committee believes that inhalation doses assigned to atomic veterans are credible upper bounds. That is probably the case, for example, when veterans received inhalation exposures mainly from descending fallout at the NTS or in the Pacific or from resuspension of activation products in soil at the NTS. In other scenarios, such as exposure to resuspended fallout caused by walking or other light activity, upper bounds may have been underestimated but the doses still were apparently low. However, the committee has concluded that there are important scenarios in which credible upper bounds of inhalation doses exceed alleged “high-sided” doses estimated by the NTPR program by large factors. Large underestimates of upper bounds occurred in scenarios in which participants (including maneuver troops and close-in observers) were exposed in forward areas shortly after a detonation at the NTS, especially late in the period of atomic testing, and were due mainly to neglect of the effects of the blast wave produced in a detonation on resuspension of previously deposited fallout, the frequent neglect of aged fallout that accumulated at the NTS throughout the period of atomic testing, and the general neglect of fractionation of radionuclides, especially plutonium, in fallout. Furthermore, in scenarios in which inhalation
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doses were underestimated by large factors, credible upper bounds of organ equivalent doses could be high enough to be important to a decision about compensation. Thus, the committee has concluded that the methods that have been used to estimate inhalation doses to atomic veterans do not consistently provide credible upper bounds of possible doses and that this could be an important deficiency in some exposure scenarios. The possibility of ingestion exposures apparently is not considered routinely in dose reconstructions for atomic veterans. However, except in rare situations, the committee has concluded that potential ingestion doses were not significant. Therefore, in nearly all cases, neglect of ingestion exposures should not have important consequences with regard to estimating credible upper bounds of total doses to the veterans. Veterans are not always given the benefit of the doubt in developing exposure scenarios and assessing film-badge data. Veterans often were not contacted to verify their exposure scenarios even when such contact was feasible and could have been helpful. In some cases, there was inadequate follow-up with other participants who might have been able to clarify scenario assumptions. As a result of inconsistent application of the policy of benefit of the doubt, the committee has concluded that upper bounds of dose have been underestimated substantially in a number of dose reconstructions for individual veterans. As a result of problems identified by the committee in scenario development and estimation of external and inhalation doses, as summarized above, total doses reported by the NTPR program do not consistently provide credible upper bounds, and the degree of underestimation of upper bounds is substantial in many cases. In response to the second part of the statement of task, the committee has concluded that doses, as they have been calculated by the NTPR program, have been accurately reported to VA and the veterans. However, the committee also believes that uncertainty in assigned doses should be reported and carefully explained to VA and the veterans. A broader communications issue is related to how changes within the program are communicated to the community of atomic veterans. The committee found that some of the changes that have been made in the dose reconstruction program over time, if adopted retroactively, would have changed a veteran’s reconstructed dose and, in perhaps a few cases, even the result of the adjudication of a claim for compensation. There is no mechanism within the present system for revisiting these decisions when changes in methods of dose reconstruction are made. The committee found that veterans are not always aware of these changes or of the fact that they can request a re-evaluation of their dose reconstruction. In response to the third part of the statement of task, the committee has concluded for reasons described in earlier statements that assumptions about input parameter values and exposure scenarios often were not credible (that is, reasonable and appropriate) and led to reported upper bounds of
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external and internal doses that are less than the 95th percentile goal in many cases. The committee found that existing documentation of individual dose reconstructions is unsatisfactory in a large majority of the 99 sampled cases reviewed by the committee. There is little evidence of quality control over the work, and many calculations in dose reconstructions are illegible or lack an explanation of their meaning or use. The committee also noted that information presented in dose reconstructions should be sufficiently complete and understandable to allow a knowledgeable individual to reproduce the calculations, but the committee found too few instances where this expectation reasonably could be met. The committee also believes that lack of a comprehensive manual of standard operating procedures is an important problem that has led to inconsistencies in dose reconstructions. In response to the fourth part of the statement of task, the committee has concluded that the radiological and historical information compiled by the NTPR program is suitable and sufficient for use in historical dose reconstruction for the atomic veterans. All in all, the committee is impressed with the large amount of information that has been brought together by the NTPR program. There is a large repository of information from which to draw data about exposures. In addition, the committee believes that the veterans themselves are a valuable source of information about their own exposures. Although some attempts have been made to contact them and seek their input about scenarios of exposure, this source of information seems to be underused. If the program of dose reconstruction continues, the committee recommends that an external system of review and oversight be established. The degree of review and oversight should be commensurate with the anticipated scope of the compensation program in the future. Although the responsibility for a permanent system of review rests with DTRA and VA, the committee provides some guidelines that may be helpful in its design and implementation. One approach to continuing review and oversight among possible alternatives is to create an advisory board that consists of persons who can evaluate the many aspects of the program, such as historical dose reconstruction, radiation risk and probability of causation, communication with the veterans and between VA and DTRA, quality assurance and quality control, and historical research related to service experience. In addition to review and oversight of the dose reconstruction program of DTRA, review and oversight of the program as a whole, including the responsibilities of DTRA and VA in the administration of the atomic veterans’ program, is desirable. If such an advisory committee is created, it should include at least one representative of the atomic veterans; meet frequently enough to understand the program fully, to conduct ran
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dom audits of doses being reconstructed and decisions regarding claims, to review methods, and to recommend changes when needed; meet with atomic veterans regularly, listen to their concerns, and ensure that their concerns are addressed; and help DTRA and VA to provide information to veterans that effectively communicates the program’s mission and process and the health risks posed by radiation exposures. About 70% of all dose reconstructions have been in response to veterans’ claims for compensation, but many of the diseases that have been claimed by veterans are now included in the presumptive regulation (38 CFR 3.309), and a dose reconstruction is no longer required unless a veteran’s participation cannot be established. With the exception of dose reconstructions for beta exposures and skin cancer, it is clear to the committee that in most future cases, even revised upper-bound dose estimates, taking into account the committee’s findings on deficiencies in methods of dose reconstruction, would be too low for the VA to conclude that the veteran’s disease was at least as likely as not caused by his radiation exposure and thus qualify the veteran for compensation. The committee appreciates the frustrations of the veterans who willingly performed their duties under extraordinary circumstances and who are confronted with the burden of seeking compensation for diseases that they believe are related to the service they performed for their country. Although the number is probably small, the committee has concluded that some veterans would have been compensated if more-credible upper bounds of dose had been estimated in their dose reconstructions. The committee’s belief applies, for example, in cases of participants who could have received a much higher inhalation dose at the NTS than was assigned in dose reconstructions, were nonsmokers, and later experienced lung cancer. One of the veterans’ many concerns about the program of dose reconstruction and compensation is that very few claims have been granted for nonpresumptive diseases under 38 CFR 3.311. VA reported to the veterans in 1996 that this number was on the order of 50. Confirmation of the number of claims awarded under the nonpresumptive regulation from the beginning of the program to the present time is difficult to obtain because the information needed to determine this number is not available in the VA database. In an effort to address the veterans’ concern, the committee looked at about 300 records of claims filed and the disposition regarding awards. We concluded that the number of claims awarded under the nonpresumptive regulation, excluding recent awards for skin cancer, is indeed very small and likely to be on the order of 50, as previously reported to the veterans. This indicates that when a veteran files a claim for a disease other than skin cancer under the nonpresumptive regulation, the probability is very low (less than 1%) that the claim will be granted. If claims granted for skin cancer since 1998 are included, the current rate of granting claims for all
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nonpresumptive disease may be as high as 10%. Before 1998, few, if any, claims for skin cancer were granted. However, it is important for the veterans to understand that there are legitimate reasons for the low number of successful claims for nonpresumptive diseases, and that these reasons are unrelated to any deficiencies in the methods of dose reconstruction used in the NTPR program. On the basis of studies of radiation dose and risk in human populations, it is evident that ionizing radiation is not a potent cause of cancer. That is indicated, for example, by the small number of excess cancers that have been observed in the Japanese atomic-bomb survivors, even though many in this population received doses much higher than the doses received by most atomic veterans. That conclusion is also indicated by the screening doses based on current radioepidemiological tables. For a given cancer type, the screening dose gives the 99% lower confidence limit of the dose associated with a probability of causation of 50%, taking the uncertainty in the cancer risk per unit dose into account. The screening doses are used to judge whether, given the current uncertain state of knowledge, it is at least as likely as not that a veteran’s cancer was caused by radiation exposure, giving the veteran the benefit of the doubt. New screening doses that will be used in the future are 10 rem or greater for most cancers, and this indicates that high doses will be required to give an appreciable probability that a veteran’s cancer was caused by the radiation exposure. Screening doses that have been used until now also are high for most cancers, although compensation could be awarded at doses of less than 10 rem in a few cases (such as 1 rem for liver cancer and 4 rem for lung cancer in a nonsmoker). The committee emphasizes that the established policy of using upper-bound estimates of dose (95th percentiles) with the more extreme lower-bound estimates of doses associated with a 50% probability of causation of various cancers is highly favorable to the veterans’ interests. If credible upper bounds of dose are obtained in dose reconstructions, atomic veterans can be compensated for nonpresumptive diseases even if the true probability that radiation exposure caused the diseases is substantially less than 50%. None of that is to say that the veterans do not have legitimate complaints about their dose reconstructions; in many cases, they do. Rather, the committee hopes that veterans will understand that their radiation exposure probably did not cause their cancers in most cases and that reasonable changes in methods of dose reconstruction in response to this report are not likely to greatly increase their chance of a successful claim for compensation in most cases when a dose reconstruction is required. The committee offers a number of recommendations that would, if implemented, improve the dose reconstruction process of DTRA and the atomic-veterans compensation program in general: If the program of dose reconstruction continues, there should be ongoing external review and oversight of the dose reconstruction and compensation pro
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grams for atomic veterans. One way to implement this recommendation would be to establish an independent advisory board. There should be a comprehensive re-evaluation of the methods being used to estimate doses and their uncertainties to establish more credible upper-bound doses to atomic veterans. A comprehensive manual of standard operating procedures for the conduct of dose reconstructions should be developed and maintained. A state-of-the-art program of quality assurance and quality control for dose reconstructions should be developed and implemented. The principle of benefit of the doubt should be consistently applied in all dose reconstructions in accordance with applicable federal regulations. Interaction and communication with the atomic veterans should be improved. For example, veterans should be allowed to review the scenario assumptions used in their dose reconstructions before the dose assessments are sent to the Department of Veterans Affairs for claim adjudication. More effective approaches should be established to communicate the meaning of information on radiation risk to the veterans. In addition to presenting general information on radiation risk, information should be communicated to veterans who file claims regarding the significance of their doses in relation to their diseases. The community of atomic veterans and their survivors should be notified when the methods for calculating doses have changed so that they can ask for updated dose assessments and re-evaluation of their prior claims.
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