Relative toxicity of (45)Ca beta-particles and (242)Cm alpha-particles following their intravenous injection into mice as radiolabelled FAP.
OBJECTIVE
To determine the relative toxicity of alpha- and beta-radiations under conditions of controlled temporal and spatial dose distribution.


METHODS
Fused aluminosilicate particles were radiolabelled with either (45)Ca (a beta-emitter) or (242)Cm (an alpha-emitter). These were injected into CBA/Ca mice to give lifespan, whole-body doses of approximately 0.5, 1.0 or 1.5 Gy. Most animals were entered into a lifespan toxicity study, but some were killed for radiochemical analysis and autoradiography.


RESULTS
Twenty-seven tumour types were identified. The most common malignant tumours were: Mammary carcinoma; liver carcinoma; malignant lymphoma; uterine histiocytic sarcoma. Excess relative risk (strictly hazard ratio) was higher for radiation-induced carcinomas than for sarcomas. The carcinomas, but not sarcomas showed a reduction in relative risk at the highest radiation dose employed. This reduction was most easily attributed to a systemic effect. The highest relative toxicity measured was for liver carcinoma (5.9, 95% confidence intervals [CI] 2.4, 14) and the lowest for uterine carcinoma (0.6, CI 0.03, 9.7). Overall, the excess relative risk ratio for SURVIVAL WAS 1.9 (CI 1.1, 3.2), FOR ALL CARCINOMA WAS 2.3 (CI 1.7, 3.0) AND FOR ALL SARCOMA WAS 2.7 (CI 0.72, 10).


CONCLUSIONS
The 10-fold variability in the observed toxicity ratio for different tumour endpoints shows that tissue sensitivity is a more important determinant of relative toxicity than radiation quality. The use of single radiation-weighting (w(R)) factors for radiation risk prediction and for radiological protection dosimetry is inconsistent with scientific observation.
Priest
Nicholas D
ND
Radiological Protection Research and Instrumentation, AECL Chalk River Laboratory, Chalk River, Ontario, Canada. priestn@aecl.ca
Hoel
David G
DG
Brooks
Paul N
PN
D000512:Alpha Particles / Q000009:adverse effects; D000538:Aluminum Silicates / Q000737:chemistry*; D000818:Animals; D001345:Autoradiography; D001610:Beta Particles / Q000009:adverse effects; D002132:Calcium Radioisotopes / Q000009:adverse effects / Q000633:toxicity*; D002277:Carcinoma / Q000532:radiotherapy; D003476:Curium / Q000009:adverse effects / Q000633:toxicity*; D004307:Dose-Response Relationship, Radiation; D005260:Female; D006845:Hydrocarbons, Fluorinated / Q000737:chemistry*; D007275:Injections, Intravenous; D008113:Liver Neoplasms / Q000532:radiotherapy; D008223:Lymphoma / Q000532:radiotherapy; D015674:Mammary Neoplasms, Animal / Q000532:radiotherapy; D051379:Mice; D008808:Mice, Inbred CBA; D009381:Neoplasms, Radiation-Induced / Q000209:etiology* / Q000473:pathology; D018570:Risk Assessment; D012509:Sarcoma / Q000532:radiotherapy; D016019:Survival Analysis; D014594:Uterine Neoplasms / Q000532:radiotherapy; D005466:Fluorocarbons
D000538:Aluminum Silicates; D002132:Calcium Radioisotopes; D003476:Curium; D006845:Hydrocarbons, Fluorinated; C542685:tris(pentafluoroethyl)trifluorophosphate anion; D005466:Fluorocarbons; C049037:aluminosilicate