Technical Report No. 11-86
The impact of the reassessment of A-bomb dosimetry:Dose estimation mehtods and preliminary cancer mortality findings
Kopecky KJ, Preston DLEditor’s note: A publication based on this report was published in Exp Parasitol 64:71-7, 1987.
Summary
This report examines the anticipated impact of the adoption by RERF of a new atomic bomb radiation dosimetry system to replace the revised tentative 1965 dosimetry system (T65DR). The current binational effort to reassess A-bomb dosimetry will eventually produce information about air doses and attenuation due to shielding by structures and body tissue. A method for computing individual survivors’ total body surface exposure doses and organ doses from such data was developed, and a set of interim 1985 dosimetry (I85D) estimates was computed by this method using the data available to RERF in late 1984. Estimates of I85D total body surface exposure doses could be computed for 64,804 of 91,231 exposed survivors with T65DR dose estimates; following present plans, revised dose estimates may become available for an additional group of 10,000 to 12,000 exposed survivors. Mortality from leukemia and from all cancers except leukemia was examined in relation to I85D total body surface exposure doses (gamma plus neutron); parallel analyses using T65DR exposure doses were also conducted for the same set of survivors. Overall estimates of radiogenic excess risk based on I85D total body surface doses were about 50% greater than those based on T65DR doses. Nonsignificant differences of only 3% or less between the radiogenic excess risks for Hiroshima and Nagasaki survivors were observed in relation to I85D doses. Modification of the radiation dose response by sex, age at the time of the bombing, or time since exposure was qualitatively similar for I85D and T65DR. For both leukemia and nonleukemic cancer mortality, the radiogenic excess risk was found to increase as a linear function of I85D total body surface dose; significantly poorer fits were obtained with pure quadratic dose-response functions, while linear-quadratic dose responses did not provide significantly better fits. Under the assumption that for both dosimetries the relative biological effectiveness of neutrons is a constant 10, compared to gamma rays, estimates of radiogenic risks based on I85D rem dose estimates were 2.5 to 2.75 times greater than those based on T65DR.
This report examines the anticipated impact of the adoption by RERF of a new atomic bomb radiation dosimetry system to replace the revised tentative 1965 dosimetry system (T65DR). The current binational effort to reassess A-bomb dosimetry will eventually produce information about air doses and attenuation due to shielding by structures and body tissue. A method for computing individual survivors’ total body surface exposure doses and organ doses from such data was developed, and a set of interim 1985 dosimetry (I85D) estimates was computed by this method using the data available to RERF in late 1984. Estimates of I85D total body surface exposure doses could be computed for 64,804 of 91,231 exposed survivors with T65DR dose estimates; following present plans, revised dose estimates may become available for an additional group of 10,000 to 12,000 exposed survivors. Mortality from leukemia and from all cancers except leukemia was examined in relation to I85D total body surface exposure doses (gamma plus neutron); parallel analyses using T65DR exposure doses were also conducted for the same set of survivors. Overall estimates of radiogenic excess risk based on I85D total body surface doses were about 50% greater than those based on T65DR doses. Nonsignificant differences of only 3% or less between the radiogenic excess risks for Hiroshima and Nagasaki survivors were observed in relation to I85D doses. Modification of the radiation dose response by sex, age at the time of the bombing, or time since exposure was qualitatively similar for I85D and T65DR. For both leukemia and nonleukemic cancer mortality, the radiogenic excess risk was found to increase as a linear function of I85D total body surface dose; significantly poorer fits were obtained with pure quadratic dose-response functions, while linear-quadratic dose responses did not provide significantly better fits. Under the assumption that for both dosimetries the relative biological effectiveness of neutrons is a constant 10, compared to gamma rays, estimates of radiogenic risks based on I85D rem dose estimates were 2.5 to 2.75 times greater than those based on T65DR.