A proposed change to astronaut exposures limits is a giant leap backwards for radiation protection
A proposed change to astronaut exposures limits is a giant leap backwards for radiation protection
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DOI：
10.1016/j.lssr.2021.07.005
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发表时间：
2021-08-17
影响因子：
2.5
通讯作者：
Hei, Tom K.
中科院分区：
文献类型：
--
作者：
Cucinotta, Francis A.;Schimmerling, Walter;Hei, Tom K.
解决宇宙射线重离子健康风险评估中的不确定性是一项重大的科学挑战，美国国家科学院（NAS）和国家辐射防护和测量理事会（NCRP）为美国国家航空航天局（NASA）提供咨询意见的许多先前报告都承认这一点。这些报告提出了一系列步骤，以寻求空间辐射防护的科学基础，包括实施与年龄和性别有关的风险评估和适合于少数辐射工作人员的照射限值，评价风险预测的不确定性，以及制定强有力的重离子放射生物学研究方案，以减少不确定性并发现有效的应对措施。对风险评估中的不确定性进行评估，可防止风险评估发生变化，揭示空间使命行动所用信息的局限性，并推动减少不确定性，通过研究发现风险的真实程度和对策的可能效力。然而，最近NAS报告的建议，为了尽量减少飞行机会的年龄和性别差异，建议基于中位数估计的600 mSv职业有效剂量限值，以达到35岁女性3%的癌症死亡率。NAS的报告并没有列举出使用NASA目前的辐射限制将女性排除在本十年计划的太空任务之外的例子。此外，在重离子放射生物学的不确定性、癌症风险以及认知障碍和循环系统疾病方面，很少考虑在这一照射水平下将遇到的风险水平。此外，他们建议限制Sieverts，而不是与豁免程序相结合的风险，本质上是建议取消宇航员的辐射限制。我们讨论了NAS建议中的几个问题，得出的结论是，这些建议可能对机组人员的健康和安全产生负面影响，并违反了辐射防护的三个原则（防止临床显著的确定性效应，限制随机效应，并实践ALARA），这将是辐射防护的一个巨大倒退。
Addressing the uncertainties in assessing health risks from cosmic ray heavy ions is a major scientific challenge recognized by many previous reports by the National Academy of Sciences (NAS) and the National Council on Radiation Protection and Measurements (NCRP) advising the National Aeronautics and Space Administration (NASA). These reports suggested a series of steps to pursue the scientific basis for space radiation protection, including the implementation of age and sex dependent risk assessments and exposure limits appropriate for a small population of radiation workers, the evaluation of uncertainties in risk projections, and developing a vigorous research program in heavy ion radiobiology to reduce uncertainties and discover effective counter-measures. The assessment of uncertainties in assessing risk provides protection against changing assessments of risk, reveals limitations in information used in space mission operations, and provides the impetus to reduce uncertainties and discover the true level of risk and possible effectiveness of countermeasures through research. However, recommendations of a recent NAS report, in an effort to minimize differences in age and sex on flight opportunities, suggest a 600 mSv career effective dose limit based on a median estimate to reach 3% cancer fatality for 35-year old females. The NAS report does not call out examples where females would be excluded from space missions planned in the current decade using the current radiation limits at NASA. In addition, there are minimal considerations of the level of risk to be encountered at this exposure level with respect to the uncertainties of heavy ion radiobiology, and risks of cancer, as well as cognitive detriments and circulatory diseases. Furthermore, their recommendation to limit Sieverts and not risk in conjunction with a waiver process is essentially a recommendation to remove radiation limits for astronauts. We discuss issues with several of the NAS recommendations with the conclusion that the recommendations could have negative impacts on crew health and safety, and violate the three principles of radiation protection (to prevent clinically significant deterministic effects, limit stochastic effects, and practice ALARA), which would be a giant leap backwards for radiation protection.