Raabe Otto G
Center for Health and the Environment, University of California, Davis, 95616, USA.
Health Phys. 2010 Mar;98(3):515-36. doi: 10.1097/HP.0b013e3181c20e25.
The ionizing radiation dose-response relationships for internally deposited radionuclides are examined using data from humans involving Ra and laboratory animal studies involving alpha-emitters Ra, Ra, Ra, Th, Pu, Pu, and Am and beta-emitters Y, Sr, Y, and Ce. Intake routes included ingestion, inhalation, and injection. The lifetime effects are best described by three-dimensional average-dose-rate/time/response surfaces that compete with other causes of death during an individual's lifetime. Using maximum likelihood survival regression methods, the characteristic logarithmic slope for cancer induction was found to be about negative one-third for alpha-emitters or about negative two-thirds for beta-emitters. At the higher average dose-rates the principal deleterious effects were those associated with radiation-induced injury while at intermediate average dose-rates radiation-induced cancer predominates. The relative biological effectiveness for cancer induction of high linear energy transfer alpha radiation with respect to low linear energy transfer beta radiation is a strong function of dose-rate. As average dose-rate decreases, the effectiveness of the beta irradiation drops off more rapidly than that of the alpha irradiation. The cumulative dose yielding a specific level of induced cancer risk is less at lower dose-rates than at higher dose-rates showing an apparent inverse dose-rate effect (up to a factor of about 10 for high linear energy transfer alpha radiation and a factor of about 2 for low linear energy transfer beta radiation). The cumulative radiation dose is neither an accurate nor an appropriate measure of cancer risk associated with protracted ionizing radiation exposure. Cancer risk associated with protracted ionizing radiation exposure is a non-linear function of lifetime average dose-rate to the affected tissues. At low average dose-rates the long latency time required for radiation-induced cancer may exceed the natural lifespan. This long latency results in a lifespan virtual threshold (cancer risk p < 0.001) for each internally deposited radionuclide. For young adult beagles, bone sarcoma induction from alpha-emitting radionuclides was unlikely for cumulative doses below about 1 Gy (20 Sv) delivered specifically to the sensitive tissues at bone surfaces in a manner associated with radionuclide relative potency from highest for Th, Pu, and Pu to lowest for Ra. Bone sarcoma induction from ingested Sr was unlikely for cumulative beta radiation doses below about 20 Gy (20 Sv), but beta irradiation of tissues adjacent to bone also induced leukemia and soft tissue carcinomas above 10 Gy (10 Sv). Inhaled radionuclides tended to be most potent in producing lung carcinoma when the radiation dose was most uniformly distributed in the lung. In young adult beagles lung carcinoma from inhaled alpha-emitting Pu in the dispersible nitrate form was unlikely for cumulative doses below about 0.5 Gy (10 Sv) and below higher cumulative doses for other forms of Pu and Pu depending on relative potency. Lung carcinoma from inhaled beta-emitting Y in relatively insoluble fused aluminosilicate particles was unlikely for cumulative doses below about 5 Gy (5 Sv) and below higher doses for inhaled particles with Y, Ce, or Sr in order of decreasing potency.
利用来自涉及镭的人体数据以及涉及α发射体镭、镭、镭、钍、钚、钚和镅和β发射体钇、锶、钇和铈的实验动物研究数据，研究了体内沉积放射性核素的电离辐射剂量-反应关系。摄入途径包括摄入、吸入和注射。终生效应最好用三维平均剂量率/时间/反应曲面来描述，这些曲面与个体一生中的其他死亡原因相互竞争。使用最大似然生存回归方法，发现α发射体诱发癌症的特征对数斜率约为负三分之一，β发射体约为负三分之二。在较高的平均剂量率下，主要的有害效应是与辐射诱导损伤相关的效应，而在中等平均剂量率下，辐射诱发的癌症占主导。高传能线密度α辐射相对于低传能线密度β辐射诱发癌症的相对生物效能是剂量率的强函数。随着平均剂量率降低，β辐射的效能比α辐射下降得更快。产生特定水平诱发癌症风险的累积剂量在较低剂量率下比在较高剂量率下要小，显示出明显的剂量率反效应（对于高传能线密度α辐射高达约10倍，对于低传能线密度β辐射约为2倍）。累积辐射剂量既不是与长期电离辐射暴露相关的癌症风险的准确度量，也不是合适的度量。与长期电离辐射暴露相关的癌症风险是受影响组织终生平均剂量率的非线性函数。在低平均剂量率下，辐射诱发癌症所需的长潜伏期可能超过自然寿命。这种长潜伏期导致每种体内沉积放射性核素的寿命虚拟阈值（癌症风险p<0.001）。对于年轻成年比格犬，以与放射性核素相对效能相关的方式，即从钍、钚和钚最高到镭最低，专门输送到骨表面敏感组织的累积剂量低于约1 Gy（20 Sv）时，由α发射放射性核素诱发骨肉瘤的可能性不大。摄入锶的累积β辐射剂量低于约20 Gy（20 Sv）时，诱发骨肉瘤的可能性不大，但骨附近组织的β辐射在超过10 Gy（10 Sv）时也会诱发白血病和软组织癌。当辐射剂量在肺中分布最均匀时，吸入的放射性核素往往在诱发肺癌方面最有效。对于年轻成年比格犬，以可分散硝酸盐形式吸入的α发射钚诱发肺癌的累积剂量低于约0.5 Gy（10 Sv）时可能性不大，对于其他形式的钚和钚，在更高累积剂量下可能性不大，这取决于相对效能。以相对不溶性熔融铝硅酸盐颗粒形式吸入的β发射钇诱发肺癌的累积剂量低于约5 Gy（5 Sv）时可能性不大，对于吸入含有钇、铈或锶的颗粒，在更高剂量下可能性不大，效能依次降低。
