低剂量辐射效应——辐射防护的基础

Various Biological Effects of Low Dose Ionizing Radiation and the Challenge on Radiological Protection Practice

低剂量辐射对生物体效应展现出多样性,而且不同LET辐射源的效应差异明显, 很难通过大剂量效应中推导.低剂量辐射的健康危害主要是远期致癌风险性,而早期效应随辐射品质、剂量、剂量率以及受照个体的不同会有不同的表现形式,突出的有三个方面:1) 细胞在接受一次几个cGy低剂量预照射后,能够对随后大剂量辐照损伤产生一定的防护作用,这种作用被称为适应性反应,或单次低剂量整体照射产生的免疫刺激效应; 2) 单次低剂量辐照所产生的单位剂量的急性损伤效应比大剂量的更大,这被称为低剂量辐射超敏感性,其剂量大小通常在0.2～0.5 Gy的范围内;3) 旁效应,是指发生在照射细胞周围的未受照细胞中的生物效应,该效应会导致高于预测值的辐射损伤效应.低剂量辐射的这些多样性效应给辐射防护实践带来了新的思考.

The biological effects of low dose ionizing radiation are various and can＇t be deduced from the high dose effects. An obvious different effect also exists among different LET radiation sources. The health harmfulness of low dose radiation would be its cancer risk. There are mainly three aspects for its early effects： 1 ） Adaptive response, i.e. a priming low dose of several cGy may protect against the lesion induced by a subsequent high dose challenge, or the stimulation of immuno-function by a single low dose exposure in whole body; 2） Exposure at a single low dose may induce an acute injury by more effective per unit dose than the larger dose exposure, which has been termed low-dose hyper-radiosensitivity （HRS）. The effective dose is generally between 0.2 - 0.5 Gy; 3） Bystander effect, which describes the biological effects occurring in the unirradiated neighboring cells, this phenomenon results in a higher damage level than predicted. Such various effects of low dose radiation have brought new thought on radiological protection practice.