Kathren R L
Washington State University, Richland 99352, USA.
Health Phys. 1996 May;70(5):621-35. doi: 10.1097/00004032-199605000-00002.
This paper traces the evolution of the linear nonthreshold dose-response model and its acceptance as a paradigm in radiation protection practice and risk analysis. Deterministic effects such as skin burns and even deep tissue trauma were associated with excessive exposure to x rays shortly after their discovery, and carcinogenicity was observed as early as 1902. Still, it was not until 1925 that the first protective limits were suggested. For three decades these limits were based on the concept of a tolerance dose which, if not exceeded, would result in no demonstrable harm to the individual and implicitly assumed a threshold dose below which radiation effects would be absent. After World War II, largely because of genetic concerns related to atmospheric weapons testing, radiation protection dose limits were expressed in terms of a risk based maximum permissible dose which clearly implied no threshold. The 1927 discovery by Muller of x-ray induced genetic mutations in fruit flies, linear with dose and with no apparent threshold, was an important underpinning of the standards. The linear nonthreshold dose-response model was originally used to provide an upper limit estimate of the risk, with zero being the lower limit, of low level irradiation since the dose-response curve could not be determined at low dose levels. Evidence to the contrary such as hormesis and the classic studies of the radium dial painters notwithstanding, the linear nonthreshold model gained greater acceptance and in the centennial year of the discovery of x rays stands as a paradigm although serious questions are beginning to be raised regarding its general applicability. The work includes a brief digression describing the work of x-ray protection pioneer William Rollins and concludes with a recommendation for application of a de minimis dose level in radiation protection.
本文追溯了线性无阈剂量反应模型的演变及其在辐射防护实践和风险分析中作为一种范式被接受的过程。在X射线被发现后不久，诸如皮肤灼伤甚至深部组织创伤等确定性效应就与过量暴露于X射线相关联，并且早在1902年就观察到了致癌性。然而，直到1925年才首次提出防护限值。在三十年的时间里，这些限值基于耐受剂量的概念，即如果不超过该剂量，对个体就不会造成明显伤害，并且隐含地假定存在一个阈值剂量，低于该剂量辐射效应就不会出现。第二次世界大战后，主要由于与大气武器试验相关的遗传问题，辐射防护剂量限值以基于风险的最大允许剂量来表示，这显然意味着不存在阈值。1927年穆勒发现X射线可诱发果蝇基因突变，且突变与剂量呈线性关系且无明显阈值，这是这些标准的一个重要基础。线性无阈剂量反应模型最初用于提供低水平照射风险的上限估计，下限为零，因为在低剂量水平无法确定剂量反应曲线。尽管有诸如兴奋效应和镭表盘画家的经典研究等相反证据，但线性无阈模型得到了更广泛的接受，在X射线发现一百周年之际，它已成为一种范式，尽管人们开始对其普遍适用性提出严重质疑。这项工作包括一段简短的题外话，描述了X射线防护先驱威廉·罗林斯的工作，并以在辐射防护中应用可忽略剂量水平的建议作为结论。
