Purpose: Alpha-radiation from polonium-210 ((210)Po) can elevate background radiation dose by an order of magnitude in people consuming large quantities of meat and seafood, particularly caribou and reindeer. Because up to 50% of the ingested (210)Po body burden is initially found in the blood, a primary target for the short range alpha-particles is the endothelial cells lining the blood vessels. This study examined the relative biological effectiveness (RBE) of (210)Po alpha-particles versus 250 kVp X-rays in producing injury to cultured bovine aortic endothelial cells.
Materials and methods: Radiation effects on cells were measured in four different ways: the percentage viable cells by trypan blue dye exclusion, the number of live cells, the lactate dehydrogenase (LDH) release to medium and the ability to form colonies (clonogenic survival).
Results: Comparison of dose-response curves yielded RBE values of 13.1+/-2.5 (SEM) for cell viability, 10.3+/-1.0 for live cell number and 11.1+/-3.0 for LDH activity. The RBE values for clonogenic survival were 14.0+/-1.0 based on the ratio of the initial slopes of the dose-response curves and 13.1, 9.9 and 7.7 for 50, 10 and 1% survival rate, respectively. At X-ray doses <0.25 Gy, a pronounced stimulatory effect on proliferation was noted.
Conclusions: Exposure to (210)Po alpha-particles was seven to 14 times more effective than X-ray exposure in causing endothelial cell damage.