◆ Result for radiation dose estimated on the basis of personal action pattern using the system developed by the National Institute of Radiological Sciences.

Fig.1　Estimation of external radiation dose for four months after the accident

• On the basis of the data on personal action patterns examined in health survey, radiation doses for 4 months after the accident were estimated for more than 100,000 people.
• Radiation doses of more than 99% people were lower than 3 mSv.
• The highest radiation dose of a person was 13 mSv.

Fig.2　Annual radiation dose of a person in Fukushima City in FY 2014

Additional radiation doses are evaluated by distributing personal dosimeters to many residents in the other many municipalities.

• On the basis of the results obtained by personal dosimeters, additional radiation doses in a year were estimated excluding contribution of natural radiation.
• Additional radiation doses for more than 95 % persons were lower than 1 mSv, and those for more than 90 % were lower than 2 mSv.

(Ishikawa, T., Yasumura, S., Ozawa, K., et al., (2015) The Fukushima Health Management Survey: estimation of external doses to residents in Fukushima Prefecture. Sci. Rep. 5: 12712. doi:10.1038/srep12712)

• Estimation of radiation doses just after the accident using a model was also conduced by the United Nations Scientific Committee. The results are in good agreement with those measured in Fukushima Prefecture.
• It is confirmed by annual measurements with personal dosimeters that radiation doses have decreased gradually year by year.

Related articles

• What were the radiation exposures just after the accident?
• What kind of unit is used for the evaluation of radiation dose? What is the relationship between the unit and air dose rates?
• Is it possible to precisely estimate radiation doses from air dose rates?
• Does the radiation dose measured with a personal dosimeter represent the real radiation dose?
• What methods are there for measurement and evaluation of external radiation doses? What are the characteristics of each method?
• Does the radiation dose of a person depend on age, gender, race, and physique?

Reference

1. 福島県, “県民健康管理調査「基本調査」の実施状況について”.
2. Ishikawa, T. et al, The Fukushima Health Management Survey: estimation of external doses to residents in Fukushima Prefecture, Scientific Report, vol.5, 2015, Article number: 12712.