@misc{oai:repo.qst.go.jp:00062750,
 author = {Hayata, Isamu and 早田 勇},
 month = {Feb},
 note = {Positive relation between risk of cancer and the frequency of chromosome aberrations in lymphocytes has been shown by the follow up studies on the subjects whose chromosomes were analyzed (reviewed by S. Bonassi. et al., Cytogenet Genome Res., 2004). There are increasing evidences showing the higher frequency of chromosome aberrations (translocations) in the peripheral lymphocytes of the individuals exposed to the environmental clastogens such as the gasses in traffic air pollutions (O. Beskid et al., Mutat Res. 2007) as well as smoking (W. Zhang et al., J. Radiat. Res. 2004; A. J. Sigurdson et al., Mutat. Res. 2008) when such frequency was compared with that of less exposed to them. 
 Under the China-Japan collaborative studies, we analyzed the frequencies of translocations in the peripheral lymphocytes of the residents in the high natural background radiation area and its control areas in a remote village, and of the residents in a large city. The frequencies were high in all the categorized sub-groups. Individual variation among subjects within a sub-group was large. Effects of the high levels of natural background radiation were small, and invisible due to the large effects of clastogenic factors in the normal living circumstances (W. Zhang et al., J. Radial. Res. 2003; C. Wang et al., China Occupational Medicine, 2008). Chromosome aberrations are routinely used for the estimation of exposed doses in cases of radiation accidents. Science radiation doses can be calculated by the dose response curves of chromosome aberrations, the frequencies of translocations analyzed by us were converted to radiation doses assuming that all those translocations had been induced by radiation. D.C.Lloyd and A.A. Edwards. (1983) reported that the induction rate of dicentrics by chronic low dose gamma irradiation is about 2.5 in 10,000 cells per cSv. In case of acute exposure the frequency follows the dose response shown as :Y = 2.31x10^-4^D + 6.33 x10^-6D^2^(M.S.Sasaki et al., J.Radial.Res. 2000).where Y is the frequency of dicentrics per 1,000 cells, and D is the dose in cSv. Because translocations and dicentrics are induced by radiation in about equal frequency (W. Zhang and I. Hayata, J. Hum. Genent. 2003),those dose response relations of dicentrics were used for the calculation of radiation dose from the frequency of translocations.
 The subjects in the present report consist of 20 elders (61.2 year-old on the average) in a large city and 16 elders (64.4 year-old on average) and 8 children (12.3 year-old on the average) in the control group in the remote village. They were all non-smokers who had no history of radiation exposure except for the natural background radiation or routine medical diagnostic procedures such as chest X-ray examination. Based on the calculated doses from the background frequencies of translocations in the lymphocytes and their standard deviations, the detectable low dose limit in health effects is discussed, NIRS International Symposium on the Effects of Low Dose Radiation},
 title = {Detectable Low Dose Limit in Health Effect Predicted by The Study on The Background Frequency of Chromosome Aberrations.},
 year = {2008}
}