Epidemiological studies of Fukushima residents exposed to ionising radiation from the Fukushima Daiichi Nuclear Power Plant prefecture-a preliminary review of current plans

It is now more than six months since the beginning of the accident on 11 March 2011 at the Fukushima Daiichi Nuclear Power Plant in Japan. The Japanese government and local health authorities have started to collect the information necessary to estimate radiation doses received by those living in the area around the plant, drafted plans for the health care of residents, and started to implement some of them. This paper reviews and discusses the studies necessary for risk evaluation of cancer and non-cancer diseases, including those already planned, mainly from the view point of evaluating health risk using epidemiological approaches. In the long run, it is important to establish a cohort with a control group. Even if the cumulative doses are estimated to be so low that it is difficult to evaluate the risk of cancer and non-cancer diseases, it is necessary to conduct such a study to reassure residents. The health care programme of the Fukushima Prefecture government, including health check-ups of residents, will help to assess indirect effects of radiation exposure, including psychological problems. The success of any studies of radiation epidemiology depends on the collection of accurate information on radiation doses received by the study subjects. However, some of the dosimetry surveys were not conducted in a timelymanner. (It should be recognised, though, that such a problemmight have been inevitable, considering the chaotic condition after the nuclear accident.) Accurate estimation of the radiation dose received by each resident is not only important for scientific risk evaluation but also to inform each resident about his or her potential risk. Otherwise, residents will bear an undue psychological burden from uncertainties regarding their radiation exposure and its health consequences. One of other important tasks in Fukushima is the improvement of the quality of the regional cancer registry in this prefecture. It is also important to start thyroid cancer screening in a year or two since the expected minimum latent period among those exposed in early childhood is about 4 years. Recently, local health authorities decided to start a thyroid screening programme for those aged 18 years or younger. Any scientific efforts in Fukushima, which need to gain the trust of study subjects about the objectivity of research, may suffer from the fact that residents in Fukushima Prefecture have begun to suspect that the Japanese government and local authorities are keeping important information from them. It seems necessary to make more effort to reflect the opinions of residents when planning health care programmes and to gain the understanding of the public for the programme. In summary, there are many problems that make the evaluation of cancer and non-cancer disease risk in Fukushima difficult. The help of international colleagues will be invaluable for overcoming those problems. In this paper, these efforts are briefly summarised and some comments are made.