Tritium biology in Japan: A search for a new approach

The health effects of tritium are a major public concern in Japan due to the presence of tritium (HTO) contaminated water at the Fukushima Dai-ichi Nuclear Power Plant (Fukushima NPP). From a scientific view, the biological effects of the contaminant HTO at the Fukushima NPP could conceivably be quite small, but the possibility of stochastic effects from tritium radiation cannot be neglected. This reasoning is based on the linear no-threshold (LNT) model, which is cited in ICRP recommendations and suggests an elevation in the frequency of the stochastic effects of radiation, even when the doses are less than 100 mGy. However, at the present, only a small amount of experimental data is available describing the biological effects of low doses radiation, and there are no established experimental systems that can clearly show whether or not the LNT model is appropriate. This is due to a wide scatter in data for the incidence of stochastic effects, which makes it difficult to distinguish radiation-induced events from spontaneous events. We propose overcoming this difficulty for radiobiology experiments using low doses or low dose rate radiation by establishing hypersensitive assay systems, and report on the current status of work investigating tritium radiobiology in Japan.