A number of dose criteria were set after the accident in Fukushima, including a criterion regarding the use of school playgrounds in Fukushima. Considering the band of 1–20 mSv/year recommended by the International Commission on Radiological Protection (ICRP) for public exposure under existing exposure situations, Japanese authorities set 20 mSv/year as a ‘start line’ for reducing the dose to school children. However, this led to considerable confusion among the general public and some experts. They thought that the dose limit was increased to 20 mSv/year (20 times as high as before), and that school children could be exposed to 20 mSv in 1 year. This is just an example of confusion caused by inadequate comprehension of radiation effects, misunderstanding of radiation protection concepts, or both. Another issue was raised regarding the higher radiosensitivity of children compared with adults. In the 2007 ICRP Recommendations, a higher risk coefficient is given to the whole population than the adult population, because the whole population includes children; a subpopulation with higher radiosensitivity and a longer life span. The point of argument was whether a lower reference level should be set for children alone. Radiation protection experts should continue to collect scientific information to improve the radiation protection system. In addition, it is the role of these experts to explain the framework of radiation protection to the general public in plain language.