Interspecies scaling of risk for radiation-induced bone cancer.
The induction of bone cancer in mice, dogs and humans, due to protracted alpha-irradiation from skeletal burdens of radium, was found to be represented by a single dose-rate/time/response function, when time was normalized with respect to species natural life-span. In the absence of other causes of death, the median time to death from bone cancer after 226Ra intake is given by tm* = 790-d*-0.29, based on the dog data, with -d* the time-weighted average absorbed dose rate in cGy/mLSF to skeleton and where time is measured as milli-life-span-fraction. On the basis of life-span scaling of the time dimension, data on cancer induction from studies with laboratory animals can be scaled to estimate human risks in a three-step process involving a three-dimensional analysis. The overall cancer risk distribution is shown to be a mountain-like surface rising from a Euclidean plane formed by the dose rate and survival time co-ordinates. At lower dose rates the time required for cancer induction may exceed the natural life-span yielding a quasi-threshold for cancer risk. For intakes of 226Ra in young adults this quasi-threshold is predicted to occur at a cumulative life-time alpha-radiation dose to the skeleton of about 1 Gy.
Raabe
O G
OG
Department of Veterinary Pharmacology and Toxicology, University of California, Davis 95616.
Rosenblatt
L S
LS
Schlenker
R A
RA
D000818:Animals; D001859:Bone Neoplasms / Q000209:etiology*; D004285:Dogs; D006801:Humans; D051379:Mice; D009381:Neoplasms, Radiation-Induced; D011883:Radium; D012306:Risk; D013045:Species Specificity
D011883:Radium