Pretreatment of animal wastes containing radioisotopes with dry-distillation

Mice that had been radiolabeled with one of seven isotopes by intraperitoneal or subcutaneous administration were dry-distilled at 800 degrees C for 10 min, and the fate of the radionuclide was examined. The radionuclides administered were 3H, 14C, 32P, 35S, 45Ca, 51Cr, and 125I, all of which are commonly used in animal experiments. After dry-distillation, 95% of 3H was found in the distillate (condensate), and 80% and 16% of 14C were recovered from exhaust gas and residual solids, respectively. Only between 10 and 20% of 35S was found in distillate. The remainder of the residual 35S was recovered from the inner wall of the exhaust vent of the dry-distillation equipment. About 24% of 125I was also recovered from the inner wall of this same exhaust vent, and the residual radioactive materials were recovered from the residual solids. On the other hand, 32P, 45Ca, and 51Cr were recovered entirely from the residual solids. The weight of the animals decreased to about 10%, and the volume to about 20% (mice and rats) to 40% (rabbits) after dry-distillation. The residual solids of animal wastes generated by dry-distillation were odorless and chemically and biologically stable. Dry-distillation has many merits as a pretreatment for the disposal of animal wastes containing radioactive material because of the easy handling, storage, and transportation of the residual solids.