There are various studies and opinions regarding the extent of the effects of the atomic bombings in Hiroshima and Nagasaki. These studies are important as they relate to compensation for those affected. This chapter traces how environmental radioactivity of the atomic bombings has been measured and how damage to the human body has been considered, and examines the difficulties in clarifying environmental contamination and compensating for it.

Introduction: The black rain lawsuit

The black rain that fell on Hiroshima and Nagasaki has an important political, cultural and psychological meaning for those affected by it. Ibuse Masuji's novel Black Rain, one of the most well-known books about the atomic bombings and the aftermath, portrays the problems of late radiation effects and marriage discrimination against atomic bomb survivors. For the sake of his niece Yasuko's marriage, Shigematsu, the protagonist, struggles to hide the fact that she was exposed to the black rain. Despite Shigematsu's efforts, the marriage breaks up and Yasuko develops atomic bomb disease. As depicted by Ibuse, survivors of the atomic bombing have been subject to discrimination due to being affected by radiation on a genetic level, as they could develop atomic bomb disease at any time in the future, a fear they lived under.

Black rain is also a concept that reflects the gray zone surrounding the notion of hibakusha (lit., “bomb-affected-person”). The word hibakusha started to be used widely after the Japanese government established the Act on Medical Care for Atomic Bomb Survivors (Genshi bakudan hibakusha no iryō nado ni kansuru hōritsu; hereinafter “Medical Law”) to provide compensation for hibakusha in the form of medical relief (House of Representatives 1957), setting the terms and defining the scope of hibakusha. The strict definition of hibakusha, the people eligible for receiving compensation based on the law, has been defined by the law based on the area where the person was at the time of the bombing and the days following. Though this area has been expanded in response to repeated requests from people outside of the originally-defined area, the movement and class action suit by many people to seek recognition as hibakusha is still ongoing. In contrast to Shigematsu's attempt to hide that Yasuko had been hit by the black rain, some survivors have fought to be recognized that they were hit by the rain that contained radioactive material.