The unit "20 mSv/year" has suddenly become the talk of the town after the Special Advisor to the Cabinet, Toshiso Kosako, made a tearful protest and resignation over the decision by the Ministry of Education, Culture, Sports, Science and Technology (MEXT) to set it as the maximum guide level of radiation at which school children are allowed to engage in outdoor activities at school, arguing that the threshold would have adverse health implications for children.With his tears, the government guideline was scrapped and children are no longer allowed to play outdoors while at school.

When it comes to children's health, Japanese public opinion is very sensitive.Protect them at all cost, end of story, no ifs or buts.Hiroshima and Nagasaki aside, we have been exposed to a greater level of radiation when China conducted atmospheric nuclear testing.We seem to conveniently disregard the fact while eagerly building up concerns, without examining what the "20 mSv/year" figure really means.

Firstly, let us examine some facts.Four years ago, the International Commission on Radiological Protection (ICRP) determined the level of 20 – 100 mSv/year as the reference dose for the protection of people in emergency exposure situations.Since the Japanese government has yet to officially accept this recommendation, ICRP, after seeing the situation in Fukushima, re-conveyed it to our nation.Accordingly, Japan adopted 20 mSv/year, the lowest of the recommended range, when setting up the boundaries for no-entry zones in FukushimaPrefecture.This is how it started.MEXT's declaration to apply this figure for the restriction of outdoor activities at school came after that.

ICRP's reference dose does not draw a line between adults and children.I have no professional medical knowledge and cannot determine whether this is appropriate or not.However, the recommendation was compiled as a result of international academic discussions.It is only natural to assume that it has a solid ground.ICRP definitely concludes that the effect of radiation on human health is the same within the range of 20 and 100 mSv/year.

Since there is no difference in the level of effect on human health, the organization defined the reference dose in a range so that national authorities could set their own threshold within it.It is left up to the discretion of individual countries to which figure they adopt, be it 20 or 100.The Japanese government adopted the lowest figure.

The decision has been received favorably in general as it reflects the nation's strict stance on the effect of radiation and deep considerations for public health.Yet the decision seems to be a political performance to show off the government's tough stance and to avert future blame.Moreover, I cannot give it a pass mark because it fails to give enough political consideration at the time of emergency.

Let me give a specific example.In Iitate Village, now subject to planned evacuation, the level of environmental radioactivity measured on March 15 was above 40 μSv/hour, but no evacuation order was issued.On April 22, when the village was designated as a Deliberate Evacuation Area, the level of released radioactivity was down to 5 μSv/hour due to the radioactive decay of Iodine 131 (half-life of 8 days).Spending one year (approx. 9,000 hours) in this environment would bring residents' exposure dose to just above 20 mSv/year.This is why the village was designated as a Deliberate Evacuation Area subject to planned evacuation of residents.

However, supposing the government adopted 50 mSv/year as the threshold, a large portion of IitateVillage could escape Deliberate Evacuation designation.Residents would not have to evacuate or leave behind their cattle.If the threshold was 100 mSv/year, many of the people currently in evacuation due to the nuclear incident could return home.

Near the end of World War II, I was among school children who were forcibly evacuated in groups.I slept in the main hall of a temple, and survived on thin rice porridge.Suffering from malnutrition, I was also bitten all over by gnats, which became infected and festered.The hardship was so overwhelming that I had even wished for a quick death on a Kamikaze mission.The moment I heard the radio announcement by the Emperor that the war had ended, I literally danced with joy, realizing that I could finally go home.The news cleared the dark cloud of despair in my mind.

Life in evacuation is true hardship.Stress could cause greater health damage than radiation.That was a lesson learned from Chernobyl.As explained in the previous report, radioactivity that could escape into the atmosphere has already been released.Environmental contamination is also on the decline.Inconvenient life in evacuation should be stopped.The only reason evacuees cannot go home is the government's decision to set 20 mSv/year as the threshold.