Relative biological effectiveness of tritium for induction of myeloid leukemia in CBA/H mice.
To help resolve uncertainties as to the most appropriate weighting factor for tritium beta rays, a large experiment was carried out to measure the relative biological effectiveness (RBE) of tritiated water compared to X rays for the induction of myeloid leukemia in male mice of the CBA/H strain. The study was designed to estimate the lifetime incidence of myeloid leukemia in seven groups of about 750 mice each; radiation exposures were approximately 0, 1, 2 and 3 Gy both for tritiated water and for X rays. The lifetime incidence of leukemia in these mice increased from 0.13% in the control group to 6-8% in groups exposed to higher radiation doses. The results were fitted to various equations relating leukemia incidence to radiation dose, using both the raw data and data corrected for cumulative mouse-days at risk. The calculated RBE values for tritium beta rays compared to X rays ranged from 1.0 +/- 0.5 to 1.3 +/- 0.3. A best estimate of the RBE for this experiment was about 1.2 +/- 0.3. A wR value of 1 would thus appear to be more appropriate than a wR of 2 for tritium beta rays.
Johnson
J R
JR
Health Sciences Division, Chalk River Laboratories, Ontario, Canada.
Myers
D K
DK
Jackson
J S
JS
Dunford
D W
DW
Gragtmans
N J
NJ
Wyatt
H M
HM
Jones
A R
AR
Percy
D H
DH
D000818:Animals; D004307:Dose-Response Relationship, Radiation; D005260:Female; D007951:Leukemia, Myeloid / Q000209:etiology*; D007953:Leukemia, Radiation-Induced / Q000209:etiology*; D008297:Male; D051379:Mice; D008808:Mice, Inbred CBA; D012062:Relative Biological Effectiveness; D014316:Tritium / Q000633:toxicity*
D014316:Tritium