Society News Archive

6 March 2000

1985 Recalculations of neutron effects on A-bomb victims were wrong and 1965 calculations of doses received--and of the consequent risk from those doses--were more accurate, says a Canadian report on a Japanese study. Jerry Cuttler, Atomic Energy of Canada Ltd. (AECL) technical services manager at Sheridan Park, writes in the latest issue of AECL's house organ "Contact" of the report of a Japanese delegation to Canadian Nuclear Society members and Toronto radiologists last August. Cuttler said physicists now recalculating estimates of the radiation sustained by the Hiroshima and Nagasaki bomb victims say they likely received the large radiation doses calculated in 1965. Re-estimates made 20 years later reassessed the role of neutrons and concluded the damage incurred from radiation alone was four times greater than previously thought, Cuttler noted. Occupational and public dose safety limits have been cut back worldwide in the 1990s based on that 1985 reassessment. Cuttler said the new study is coming up with neutron numbers closer to the 1965 conclusions. In addition, studies are finding the risk appears to decrease as the survivors age, and they are living longer than the unirradiated people in neighboring cities. "The efficacy of the DNA repair (mechanism) is not constant and the actual proliferation of cancer cells is not compatible with the linear-no-threshold model," Cuttler said.