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Abstract：
The primary aim of the epidemiologic study of one million U.S. radiation workers and veterans [the Million Worker Study (MWS)] is to provide scientifically valid information on the level of radiation risk when exposures are received gradually over time and not within seconds, as was the case for Japanese atomic bomb survivors. The primary outcome of the epidemiologic study is cancer mortality, but other causes of death such as cardiovascular disease and cerebrovascular disease will be evaluated. The success of the study is tied to the validity of the dose reconstruction approaches to provide realistic estimates of organ-specific radiation absorbed doses that are as accurate and precise as possible and to properly evaluate their accompanying uncertainties. The dosimetry aspects for the MWS are challenging in that they address diverse exposure scenarios for diverse occupational groups being studied over a period of up to 70 y. The dosimetric issues differ among the varied exposed populations that are considered: atomic veterans, U.S. Department of Energy workers exposed to both penetrating radiation and intakes of radionuclides, nuclear power plant workers, medical radiation workers, and industrial radiographers. While a major source of radiation exposure to the study population comes from external gamma- or x-ray sources, for some of the study groups, there is a meaningful component of radionuclide intakes that requires internal radiation dosimetry assessments. Scientific Committee 6-9 has been established by the National Council on Radiation Protection and Measurements (NCRP) to produce a report on the comprehensive organ dose assessment (including uncertainty analysis) for the MWS. The NCRP dosimetry report will cover the specifics of practical dose reconstruction for the ongoing epidemiologic studies with uncertainty analysis discussions and will be a specific application of the guidance provided in NCRP Report Nos. 158, 163, 164, and 171. The main role of the Committee is to provide guidelines to the various groups of dosimetrists involved in the MWS to ensure that certain dosimetry criteria are considered: calculation of annual absorbed doses in the organs of interest, separation of low and high linear-energy transfer components, evaluation of uncertainties, and quality assurance and quality control. It is recognized that the MWS and its approaches to dosimetry are a work in progress and that there will be flexibility and changes in direction as new information is obtained with regard to both dosimetry and the epidemiologic features of the study components. This paper focuses on the description of the various components of the MWS, the available dosimetry results, and the challenges that have been encountered. It is expected that the Committee will complete its report in 2016.
摘要：
对100万美国放射工作者和退伍军人进行流行病学研究的主要目的是提供有关辐射风险水平的科学有效信息，这些信息是随着时间的推移而不是在几秒钟内逐渐受到辐射。日本原子弹幸存者也是如此。流行病学研究的主要结果是癌症死亡率，但是将评估其他死亡原因，例如心血管疾病和脑血管疾病。研究的成功与剂量重建方法的有效性有关，以提供尽可能准确和精确的器官特异性辐射吸收剂量的现实估计，并正确评估其伴随的不确定性。MWS的剂量学方面具有挑战性，因为它们针对长达70年的不同职业群体进行了不同的暴露场景。剂量学问题在被认为的不同暴露人群中有所不同：原子退伍军人，美国能源部工作人员暴露于穿透性辐射和放射性核素的摄入量，核电站工人,医疗放射工作者,和工业射线技师.虽然研究人群的主要辐射暴露源来自外部伽马射线或X射线源，对于一些研究小组来说，放射性核素摄入量中有一个有意义的组成部分，需要进行内部辐射剂量学评估。国家辐射防护和测量委员会（NCRP）成立了科学委员会6-9，以编写有关MWS的全面器官剂量评估（包括不确定性分析）的报告。NCRP剂量测定报告将涵盖正在进行的流行病学研究的实际剂量重建的细节，并进行不确定性分析讨论，将是NCRP报告编号中提供的指导的具体应用。158、163、164和171。委员会的主要作用是向参与MWS的各类剂量测定者提供指导方针，以确保考虑到某些剂量测定标准:计算感兴趣器官的年吸收剂量，分离低和高线性能量转移分量，不确定性的评估，质量保证和质量控制。人们认识到，MWS及其剂量测定方法正在进行中，随着获得有关剂量测定和研究组成部分的流行病学特征的新信息，将具有灵活性和方向上的变化。本文重点介绍了MWS的各个组成部分,可用的剂量测定结果，以及遇到的挑战。预计委员会将在2016年完成其报告。
