Early Effects on Survivors
Within several months to several years after the atomic bombings
Early effects include various acute radiation symptoms. Information on these symptoms was obtained by interviewing more than 100,000 atomic-bomb survivors primarily from 1956 to 1961. Among the acute radiation symptoms recalled by survivors, epilation (hair loss) is regarded as the most reliably reported. That is, it is considered to be more objectively remembered than other symptoms, such as vomiting, bleeding from the gums, diarrhea, and purpura.
In general, acute radiation symptoms do not appear at low-dose radiation exposures, giving rise to a concept known as a threshold dose. That is, below a certain radiation dose, no acute symptoms occur. This is in contrast to a theory known as the linear dose-response relationship, which is illustrated by malignant diseases, one of the most well established late effects of radiation exposure. This concept implies that the higher the radiation dose, the greater the risk of developing a malignancy.