Threshold assumption in A-bomb and nuclear power plant lawsuits

This study aims to examine the possibility of calculating damages for the health effects of lowdose radiation exposure under an untraditional tort doctrine. This is because nuclear damage is a specific type of damage that has no precedent in Japan. In the A-Bomb «Black Rain» Lawsuit, the Hiroshima High Court extensively ruled that the health effects of internal radiation exposure were acceptable, without relying on scientific dose estimates. This is a different decision from the precedent in similar cases. This paper argues that the Hiroshima case is beneficial to the relief of the Hibakusha. However, the Hiroshima case did not deal with specific considerations of the threshold assumption and made a qualitative decision. And this had a negative impact on the Nagasaki judgement. In other words, the Nagasaki case led to an underestimation of the health effects of lowdose radiation exposure and, as a result, the scope of relief for Hibakusha was limited.