Corrections in the atomic bomb data to examine low dose risk

Cancer incidence and mortality data from the cohort of Japanese atomic bomb survivors in Hiroshima have been adjusted for the uncertainty that exists in the dose estimates, the systematic error in the neutron dose estimates, and a dose-dependent relative biological effectiveness. Once the adjustments were incorporated in the dose estimates, the data were modeled with a threshold term to allow for the possibility of a threshold dose response. The dose response models that were fit to the data were otherwise the same models used in the original papers. The threshold term was included in the model allowing for possible threshold values ranging from 0 to 0.35 Sv. These analyses suggest that the fit of the A-bomb solid tumor and leukemia incidence data are significantly improved by the addition of a threshold term in comparison with the purely linear or linear quadratic model. The results from the mortality data suggest that the leukemia data agree more with the threshold model than the linear quadratic model although the linear quadratic model is statistically equivalent, while the solid tumor data does not suggest any improvement with a threshold.