This article explores how the models of medical risk from radiation established in the aftermath of the nuclear attacks on Hiroshima and Nagasaki are insufficient for understanding the risks faced by people in contaminated environments like Fukushima. These models focus exclusively on levels of external radiation, while the risk faced by people in areas affected by radioactive fallout comes from internalizing fallout particles. These models have helped to obscure the health impacts over the last 76 years of those exposed to fallout, from the people who experienced the Black Rain in Hiroshima, to the global hibakusha exposed through nuclear testing, production and accidents, and now to those living where the plumes deposited radiation in Fukushima.