Conclusions and Suggestions on Low-Dose and Low-Dose Rate Radiation Risk Estimation Methodology

Background: For radiological protection and control, the International Commission on Ra- diological Protection (ICRP) provides the nominal risk coefficients related to radiation expo- sure, which can be extrapolated using the excess relative risk and excess absolute risk obtained from the Life Span Study of atomic bomb survivors in Hiroshima and Nagasaki with the dose and dose-rate effectiveness factor (DDREF).Materials and Methods: Since it is impossible to directly estimate the radiation risk at doses less than approximately 100 mSv only from epidemiological knowledge and data, support from radiation biology is absolutely imperative, and thus, several national and international bodies have advocated the importance of bridging knowledge between biology and epidemiology. Be- cause of the accident at the Tokyo Electric Power Company (TEPCO)’s Fukushima Daiichi Nu- clear Power Station in 2011, the exposure of the public to radiation has become a major concern and it was considered that the estimation of radiation risk should be more realistic to cope with the prevailing radiation exposure situation.Results and Discussion: To discuss the issues from wide aspects related to radiological protec- tion, and to realize bridging knowledge between biology and epidemiology, we have established a research group to develop low-dose and low-dose-rate radiation risk estimation methodology, with the permission of the Japan Health Physics Society.Conclusion: The aim of the research group was to clarify the current situation and issues relat- ed to the risk estimation of low-dose and low-dose-rate radiation exposure from the viewpoints of different research fields, such as epidemiology, biology, modeling, and dosimetry, to identify a future strategy and roadmap to elucidate a more realistic estimation of risk against low-dose and low-dose-rate radiation exposure.Keywords: Radiation Risk Estimation, Low Dose and Low Dose Rate, Epidemiology, Biology, Modeling, Dosimetr

The influence of beryllium on cell survival rates in theIn-vitro culture system, on intracellular DNA synthesis and on SRBC-IgM antibody production responses

Immunocytotoxicity of beryllium (Be) was evaluated by studying cell viability, intracellular DNA synthesis and SRBC-IgM response in an in-vitro culture system using non-sensitized spleen cells of a C57BL mouse. Be addition showed a suppressive effect on cell viability, an enhancing effect on DNA synthesis and on IgM antibody production. The suppressive effect on cell viability manifested itself markedly as the concentration of Be was increased or the culture time was prolonged. The DNA synthesis-enhancing effect was noted at a relatively low concentration of Be (not more than 10μM). The enhancing effect on the IgM response was related to Be concentration at not more than 20μM. The experimental results mentioned above speculate that the cytotoxicity of Be shows a conflicting pattern of enhancement or suppression according to the concentration used and that immunologically it has a modulating effect or an activating effect on the immunocompetent cells