In the final stages of World War II, the United States dropped a 16 kiloton yield uranium atomic bomb named Little Boy on Hiroshima on August 6, 1945. Three days later, a 21 kiloton yield plutonium bomb was dropped on Nagasaki (30). These bombs, thankfully, remain the only human experience with actually using nuclear weapons because of the horror of what was unleashed. Far more power­ful hydrogen fusion bombs were later developed by both the United States and the Soviet Union, unleashing the Cold War and a reign of terror that lasted until the 1990s. The number of people killed in the two cities is uncertain, but it is estimated that about 140,000 died in Hiroshima and 70,000 died in Nagasaki by the end of 1945 (31). Most of the people died of the intense heat and the bomb blast, not so different from people who died from the fire-bombing of Tokyo and other Japanese cities, as well as Dresden and other cities in Germany. But a sinister new form of death occurred within days, weeks, and months from the radiation, known as acute radiation syndromes.

There are three different ways that very high doses of radiation kill peo­ple: hematopoietic syndrome, gastrointestinal (GI) syndrome, and cerebrovascu­lar syndrome. In addition, high doses of radiation cause a generalized temporary sickness known as the prodromal syndrome that causes nausea, diarrhea, fever, and low blood pressure. The prodromal syndrome begins with doses as low as 1 Gy but becomes more severe and prolonged after higher doses of several Gy. The hematopoietic syndrome is due to the death of stem cells in bone marrow that produce the white blood cells necessary for our immune systems. These are the most sensitive cells in our bodies. There is about a 50% chance that a human will die from a whole body dose of 4 Gy within several weeks, though treatment with antibiotics and isolation in a sterile environment can sometimes help people sur­vive doses up to 7 Gy. At higher doses of 8 Gy or more, 100% of people die within a week or so from the gastrointestinal syndrome. The rapidly growing stem cells of the intestine (crypt cells) become depleted and the intestines become leaky and unable to absorb food. Rampant infection, shock, and electrolyte imbalance usu­ally cause death from the GI syndrome. Finally, for extremely high doses of 50 Gy or more to the head, people die of the cerebrovascular syndrome within hours (7).