The LD50 associated with exposure to the atomic bombing of Hiroshima.

Data on a total of 7,593 persons in Hiroshima who were in 2,518 wooden Japanese houses and exposed to A-bomb within 1.6 km from the hypocenter have been used to estimate the LD50/60. The effect of radiation shielding for these people in particularly well-characterized in the new dosimetry system DS86. A range of values emerge, varying slightly with the method of estimation used. This range, derived from DS86 marrow doses, and based on a linear fit to equally weighted estimates of the probabilities of death at various doses, is 2.3-2.6 Gy. A linear estimate in which the probabilities of death at the various doses are weighted by the inverse of their variances is somewhat lower, 2.2 Gy. These values may be underestimates of actual LD50/60 because of inclusion of deaths in the first day, and the severely injured (burns, trauma) who survived the first day but succumbed later to their injuries.