Acute Toxicity of Beta-Emitting Radionuclides That May Be Released in a Reactor Accident and Ingested

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Abstract
Suckling, weanling and adult rats received 106Ru-106Rh by gavage and adult beagle dogs ingested 106Ru-106Rh to determine the toxicity of this high-energy (1.4 MeV) .beta.-emitting nuclide pair. The LD50 for suckling, weanling and adult rats were 1.5, 18 and 9.0 mCi/kg, respectively. Adult rats were given 147Pm by gavage to determine if a low-energy (0.06 HeV) .beta. emitter could also cause death by damaging the bowel. The LD50 of 147Pm in rats was about 5 Ci/kg. The calculated radiation doses absorbed in the target cells at the LD50 level were approximately the same for the 2 radionuclides (3500 rad), although the doses at the mucosal surface differed widely. The LD50 for 106Ru-106Rh in dogs was about 3.5 mCi/kg. Dosimeters placed beneath the mucosa in dogs indicated that the radiation dose to the target cells that caused death from 106Ru-106Rh was about the same as for rats. The signs of intestinal injury, their duration and the probabilities of tissue repair were much different in the dog than in the rat. The midcolon and lower colon of dogs were usually denuded at focal sites after ingestion of 2.5-4.0 mCi/kg, and frequently that damage was irreversible. The fatal consequence of severe mucosal damage was averted in 2 dogs by colectomy and an ileorectal anastomosis.