Wakeford Richard
Dalton Nuclear Institute, The University of Manchester, Pariser Building G Floor, Sackville Street, Manchester M13 9PL, UK.
J Radiol Prot. 2012 Mar;32(1):N89-93. doi: 10.1088/0952-4746/32/1/N89. Epub 2012 Mar 6.
Statistical models describing how the radiation-related risks of particular types of cancer vary with the doses of radiation received by specific tissues are derived from data gathered in epidemiological studies of exposed groups of people, guided by an incomplete understanding of radiobiological mechanisms gleaned from experimental studies. Cancer risk models have been developed for a dozen or so different types of cancer, and take account of the effect of important risk modifying factors such as age at exposure and time since exposure. Of primary importance in the development of cancer risk models is the experience of the Japanese atomic bomb survivors, but other exposed groups contribute information, including those exposed to radiation from internally deposited radioactive material, such as inhaled radon. Cancer risk models predict that at low doses or low dose rates the excess risk of cancer is directly proportional to the dose of radiation received, with no threshold dose--the linear no threshold (LNT) dose-response model--and the inferred summary estimate of the overall average lifetime excess risk of developing a serious cancer is ∼ 5%/Sv. It is these cancer risk models and this inferred nominal risk estimate that provide the technical basis of radiological protection. Although it is difficult to definitively test the LNT model at low doses or low dose rates, because the predicted excess risk is small compared with fluctuations in the baseline risk, evidence exists that a small risk of cancer results from low-level exposure to radiation and that the excess risk is around that predicted by current risk models.
描述特定类型癌症的辐射相关风险如何随特定组织所接受的辐射剂量而变化的统计模型，是从对受辐射人群的流行病学研究收集的数据中推导出来的，这些数据受从实验研究中收集到的对放射生物学机制的不完全理解所指导。已经针对大约十二种不同类型的癌症开发了癌症风险模型，并考虑了重要的风险修正因素的影响，例如暴露时的年龄和暴露后的时间。在癌症风险模型的开发中，最重要的是日本原子弹幸存者的经验，但其他受辐射群体也提供了信息，包括那些暴露于体内沉积放射性物质（如吸入氡）辐射的人群。癌症风险模型预测，在低剂量或低剂量率下，癌症的超额风险与所接受的辐射剂量成正比，不存在阈值剂量——即线性无阈值（LNT）剂量反应模型——并且推断出的患严重癌症的总体平均终生超额风险的汇总估计约为5%/Sv。正是这些癌症风险模型和这个推断出的名义风险估计提供了放射防护的技术基础。尽管在低剂量或低剂量率下很难明确测试LNT模型，因为与基线风险的波动相比，预测的超额风险很小，但有证据表明，低水平辐射暴露会导致患癌症的小风险，并且超额风险约为当前风险模型所预测的风险。
