Kellerer A M, Nekolla E A
Radiobiological Institute of the University of Munich, Germany.
Health Phys. 2000 Oct;79(4):412-8. doi: 10.1097/00004032-200010000-00010.
There is no firm scientific information on the potential health effects, such as increased cancer rates, due to low doses of ionizing radiation. In view of this uncertainty ICRP has adopted as a prudent default option the linear no-threshold (LNT) assumption and has used it to derive nominal risk coefficients. Subsequent steps, such as the comparison of putative fatality rates in radiation workers with observed accident rates in other professions, have given the risk estimates a false appearance of scientific fact. This has encouraged meaningless computations of radiation-induced fatalities in large populations and has caused a trend to measure dose limits for the public not against the magnitude of the natural radiation exposure and its geographic variations, but against the numerical risk estimates. In reaction to this development, opposing claims are being made of a threshold in dose for deleterious health effects in humans. In view of the growing polarization, ICRP is now exploring a new concept "controllable dose" that aims to abandon the quantity collective dose, emphasizing, instead, individual dose and, in particular, the control of the maximum individual dose from single sources. Essential features of the new proposal are here examined, and it is concluded that the control of individual dose will still have to be accompanied by the avoidance of unnecessary exposures of large populations, even if their magnitude lies below that acceptable to the individual. If a reasonable cut-off at trivial doses is made, the collective dose can remain useful. Misapplications of collective dose are not the deeper cause of the current controversy; the actual root is the misrepresentation of the LNT-assumption as a scientific fact and the amplification of this confusion by loose terminology. If over-interpretation and distortion are avoided, the current system of radiation protection is workable and essentially sound, and there is no need for a fruitless LNT-controversy. The new concept of controllable dose promises simplifications and improvements, but any major change of principles needs to be carefully considered in a broad discussion that ICRP is presently seeking.
关于低剂量电离辐射对健康的潜在影响，如癌症发病率增加等，目前尚无确凿的科学信息。鉴于这种不确定性，国际放射防护委员会（ICRP）采用了线性无阈（LNT）假设作为审慎的默认选项，并据此得出名义风险系数。后续步骤，如将辐射工作人员的推定死亡率与其他行业观察到的事故率进行比较，使风险估计呈现出科学事实的假象。这鼓励了对大量人群中辐射诱发死亡的无意义计算，并导致了一种趋势，即衡量公众剂量限值不是依据自然辐射暴露的大小及其地理差异，而是依据数值风险估计。针对这一发展态势，有人提出了人类有害健康效应存在剂量阈值的相反观点。鉴于分歧日益两极化，ICRP目前正在探索一个新的概念“可控剂量”，旨在摒弃集体剂量这一量值，转而强调个人剂量，尤其是对单一源产生的最大个人剂量的控制。本文对这一新提议的基本特征进行了审视，并得出结论：即使大量人群的辐射暴露量低于个人可接受水平，对个人剂量的控制仍须辅之以避免不必要的照射。如果对微不足道的剂量进行合理截断，集体剂量仍可发挥作用。集体剂量的不当应用并非当前争议的深层原因；真正的根源是将LNT假设错误地表述为科学事实，并因术语不严谨而加剧了这种混淆。如果避免过度解读和歪曲，现行辐射防护体系是可行的且基本合理，无需进行毫无结果的LNT争议。可控剂量这一新概念有望带来简化和改进，但原则上的任何重大改变都需要在ICRP目前正在寻求的广泛讨论中仔细权衡。
