| Cancers induced by ionizing radiation are called radiogenic cancers or radiogenic neoplasms. Radiogenic cancers have no special pathological or clinic characteristics which made it difficult to distinguish them from cancers caused by other factors. Along with the development of nuclear technology, many occupational staff and public have suffered or are suffering from man-made ionizing radiation. Some of them may develop cancers. To adjudicate claims for cancers diagnosed following exposure to ionizing radiation has became an important problem of labour insurance and occupational disease prevention.Now, judging radiogenic neoplasms by estimating"probability of causation"(PC) values has been approved by many countries. There are two conditions to calculate PC, first is to estimate the cancers excess relative risk by analyzing epidemiological data, and second is to determine organ dose of the cancer site. In China, cancers with PC great than 50% are considered radiogenic cancers and the parameters for PC calculation of five cancer sites are given in national standard. PC estimating methods for many other cancer sites have not been established for Chinese population.In this paper, we studied the PC calculation methods and releated organ dose reconstruction for Chinese population. The main results are as follows:1. Analyses were conducted using solid cancer incidence of atomic bomb survivors published in 2007. Based on a model that excess relative cancer risk varies with radiation dose, age at exposure, gender, and attained age, we performed parameter estimation using EPICURE software for each cancer site of stomach, colon, liver, lung, bladder, female breast, non-melanoma skin cancer, thyroid, oral cavity, esophagus, rectum, gallbladder, pancreas, renal cell, brain and other nervous system, uterus, ovary, prostate, and for all other solid cancers.2. A linear combination between the additive and multiplicative model was used to transfer excess relative risk (ERR) estimates of LSS data to Chinese population. For breast cancer, the additive transfer model was used. For thyroid and skin cancer, the multiplicative transfer model was used. For stomach cancer, a probability weight of 30% was assigned to the multiplicative model, and 70% to additive model. For all other solid cancers, probability weight of 50% was assigned to both the additive and multiplicative model.3. The interaction between radiation dose and epidemiological risk factors was investigated and some modification factors were applied to ERR for Chinese population. It was assumed that the interaction of smoking and exposure to low-LET radiation was additive, and a smoking category-related factor was used to adjust the ERR for lung cancer. And for all solid cancers, according to the minimal latent period and distribution of risk over time following exposure, a set of scaling factors was used.4. Conversion from monitored photon, neutron, and electron dose to absorbed dose in the organ of interest was conducted by simplifying the external exposure scenarios to PA, AP, ROT, ISO and their combinations.5. A computer program was compiled for estimating PC values of solid cancers for Chinese population. We compared the calculated PC values of thyroid cancer with the current national standard calculation method. The calculated PC values of both methods show the same dependence on sex, dose and age at exposure. When the age at exposure increases, the calculated PC values both decrease but our results decrease more. Our method was based on the latest radio-epidemiologic data and the results may be more reliable.This paper established methods of estimating PC of radiogenic cancers for Chinese population based on the analysis of latest radio-epidemiologic data. The intent of this study is to facilitate the adjudication of compensation claims for cancers diagnosed following exposure to ionizing radiation and to provide assistance for the revision of diagnostic criteria of occupational radiation sickness.
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