Cancer risk estimates for gamma-rays with regard to organ-specific doses. Part I: All solid cancers combined.
A previous analysis of the solid cancer mortality data for 1950-1990 from the Japanese life-span study of the A-bomb survivors has assessed the solid cancer risk coefficients for gamma-rays in terms of the low dose risk coefficient ERR/Gy, i.e. the initial slope of the ERR vs. dose relation, and also in terms of the more precisely estimated intermediate dose risk coefficient, ERR(D1)/D1, for a reference dose, D1, which was chosen to be 1 Gy. The computations were performed for tentatively assumed values 20-50 of the neutron RBE against the reference dose and in terms of organ-averaged doses, rather than the traditionally applied colon doses. The resulting risk estimate for a dose of 1 Gy was about half as large as the most recent UNSCEAR estimate. The present assessment repeats the earlier analysis with two major extensions. It parallels computations based on organ-average doses with computations based on organ-specific doses and it updates the previous results by using the cancer mortality data for 1950-1997 which have recently been made available. With an assumed neutron RBE of 35, the resulting intermediate dose estimate of the lifetime attributable risk (LAR) for solid cancer mortality for a working population (ages 25-65 years) is 0.059/Gy with the attained-age model, and 0.044/Gy with the age-at-exposure model. For a population of all ages, 0.055/Gy is obtained with the attained-age model and 0.073/Gy with the age-at-exposure model. These values are up to about 20% higher than those obtained in the previous analysis with the 1950-1990 data. However, considerably more curvature in the dose-effect relation is now supported by the computations. A dose and dose-rate reduction factor DDREF=2 is now much more in line with the data than before. With this factor the LAR for a working population is--averaged over the age-at-exposure and the age-attained model--equal to 0.026/Gy. This is only half as large as the current ICRP estimate which is also based on the assumption DDREF=2.
Radiobiological Institute, University of Munich, Schillerstrasse 42, 80336, Munich, Germany. Linda.Walsh@LRZ.uni-muenchen.de
Linda
L
Walsh
Werner
W
Rühm
Albrecht M
AM
Kellerer
D000465:Algorithms; D001822:Body Burden; D003198:Computer Simulation; D005720:Gamma Rays; D006801:Humans; D015994:Incidence; D007564:Japan / Q000453:epidemiology; D008954:Models, Biological; D009381:Neoplasms, Radiation-Induced / Q000401:mortality*; D009689:Nuclear Warfare; D009928:Organ Specificity; D011829:Radiation Dosage; D011834:Radiation Monitoring / Q000379:methods*; D011874:Radiometry / Q000379:methods; D012062:Relative Biological Effectiveness; D018570:Risk Assessment / Q000379:methods*; D012307:Risk Factors; D016019:Survival Analysis