21. 委员会 2006 年报告附件 A 所列的各项结果表明，辐射照射引起的癌症的生命期风险估计数很容易受到自发性癌症本底发生率变化的影响。这些研究结果表明，这种可变性造成的差别可以与使用不同的人群间风险估计转移方法或风险预测方法所产生的差别相比较。所有这些预测的可变性突出说明，很难选择单独一个值来表示辐射诱发癌症的寿命风险。另外，特定类型癌症的风险估计中的不确定性一般大于所有癌症的风险估计不确定性。
21. The results presented in annex A to the Committee’s 2006 report illustrate the sensitivity of estimates of lifetime cancer risk due to radiation exposure to variations in the background rates of spontaneous cancers. These findings suggest that this variability can lead to differences that are comparable with those associated with different methods of transferring risk estimates between populations or methods of risk projection. The variability in all these projections highlights the difficulty of choosing a single value to represent the lifetime risk of radiation-induced cancer. Furthermore, uncertainties in estimates of risks for specific types of cancer are generally greater than the uncertainties in estimates of risks for all cancers together.