Objective To identify the suitability of excess relative risk (ERR) coefficient of radon induced miner lung cancer proposed by NIH Publication (1994) which was based on the data of Yunnan tin miners. Methods Using the collected materials of epidemiology, underground ventilation, radon progeny monitoring and environmental arsenic pollution, the problems in the process of estimation of cumulative exposure of radon progeny and adjustment of combined effect of arsenic exposure for Yunan tin miners by NIH Publication were analyzed. Results Because of overestimation of the time of underground working and actual exposure to radon progeny for previous Yunnan tin miners by NIH, the resultant ERR coefficient of radon induced lung cancer was underestimated.The relative risks of different radon arsenic exposure groups were used by NIH to adjust the combined effect of arsenic without considering the difference of environmental pollution in miner and control groups;that was the another reason for the decrease of ERR coefficient. Conclusion The ERR coefficient of radon induced lung cancer was probably underestimated for Chinese miners by NIH Publication;therefore it is unsuitable to be used in the risk projection and risk management for radon induced lung cancer in China.It may be premature to use the Yunnan tin miner data as the value for Chinese miners in the combined analysis of world miner studies.]]> 2true Objectives To research whether prolonged or repeated low level ionizing radiation can induce female breast cancer or not and to investigate other risk factors related to breast cancer risk,a nested case control study was done.Methods 30 cases of breast cancers were enrolled in the study,4 normal persons were selected from X-ray workers as controls to match each case.Logistic regression model was used for risk analysis.Results ①Accumulative breast dose is a significant risk factor,odds ratio(OR) between two dose levels (10c Gy) is 1.73(95%CI=1.05—2.84).②ORs of other two factors,obesity and family history of breast cancer,are 4.07(P = 0.01) and 26.67(P =0.024) respectively.③Interaction may exist between occupational X-ray exposure and obesity or non lactation.Conclusions Long time and low level occupational X-ray exposure may relate to excess risk of female breast cancer among medical diagnostic X-ray workers.Family history of breast cancer and obesity are also the significant risk factors of the cancer.The existence of obesity and non lactation may enhance the effect of radiation induced breast cancer.]]> 1true