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Background. Analyses of Japanese A-bomb survivors' cancer mortality risks are used to establish recommended annual dose limits, currently set at 1 mSv (public) and 20 mSv (occupational). Do radiation doses below 20 mSv have significant impact on cancer mortality in Japanese A-bomb survivors, and is the dose-response linear?. Methods. I analyse stomach, liver, lung, colon, uterus, and all-solid cancer mortality in the 0 - 20 mSv colon dose subcohort of the 1950-90 (grouped) mortality cohort, by Poisson regression using a time-lagged colon dose to detect latency, while controlling for gender, attained age, and age-at-exposure. I compare linear and non-linear models, including one adapted from the cellular bystander effect for α particles. Results. With a lagged linear model, Excess Relative Risk (ERR) for the liver and all-solid cancers is significantly positive and several orders of magnitude above extrapolations from the Life Span Study Report 12 analysis of the full cohort. Non-linear models are strongly superior to the linear model for the stomach (latency 11.89 years), liver (36.90), lung (13.60) and all-solid (43.86) in fitting the 0 - 20 mSv data and show significant positive ERR at 0.25 mSv and 10 mSv lagged dose. The slope of the dose-response near zero is several orders of magnitude above the slope at high doses. Conclusion. The standard linear model applied to the full 1950-90 cohort greatly underestimates the risks at low doses, which are significant when the 0 - 20 mSv subcohort is modelled with latency. Non-linear models give a much better fit and are compatible with a bystander effect. © 2007 Dropkin; licensee BioMed Central Ltd.
Dropkin, G. (2007). Low dose radiation and cancer in A-bomb survivors: Latency and non-linear dose-response in the 1950-90 mortality cohort. Environmental Health: A Global Access Science Source, 6. https://doi.org/10.1186/1476-069X-6-1