Tissue Digestion - Technical Information

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> Digestion of Radioiodine Labeled Tissues
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Digestion of Radioiodine Labeled Tissues

Among the most difficult biological wastes to deal with are tissues and carcasses that have been generated in biomedical and pharmaceutical research that contain minute amounts of radioactive isotopes that had been injected into animals to study cell and tissue function, drug localization and metabolism, and toxin localization. To meet Federal and state regulations for disposal of solid LLRBW, whole carcasses of small animals must be packed in lime and an adsorbant, then sealed in a 30 gal can. The 30 gallon cans hold approximately 25 kg of animal carcasses. Therefore, large animals must be dismembered and otherwise butchered for packing of their parts into multiple 30 gallon cans. Each 30 gallon can must then be packed in a 55 gal drum, also filled with adsorbant, and shipped to a licensed low-level radioactive waste (LLRW) burial site. There are only two such sites currently operating in the United States, one of which, in Hanford, Washington, is limited to accepting LLRW only from the Northwest and Rocky Mountain states and the other, in Barnwell, South Carolina, accepts only limited amounts of LLRW from states other than South Carolina, Vermont, and Connecticut (the Atlantic Compact). The cost for shipping and burying each 55 gal drum containing the can of radioactive carcasses is currently nearly $200.00 per kilogram at Barnwell and is scheduled to increase rapidly with surcharges until Barnwell closes its doors to out-of-compact waste in 2008.

However, it must be emphasized that the amount of radioisotope in each animal is usually such that, if it were in an aqueous solution, could be released to a sanitary sewer and meet all Federal and state regulations. 10 CFR 20 and state regulations derived from it list the maximum permissible sewer disposal concentrations, as well as weekly and yearly release limits, for over 500 radionuclides.

In contrast, to the disposal process described above, the WR2 Process converts animal tissues and carcasses from solid low-level radioactive biological waste (LLRBW) to an aqueous solution that is suitable for release to a sanitary sewer under 10 CFR 20 and derivative state regulations and does so at a cost of $0.07-$0.13 per kilogram*. The graph and table below summarize the results of one of the experiments used to demonstrate the validity of this procedure, which led the New York State Department of Environmental Conservation to approve the use of the WR2 Model 100 Tissue Digestor for disposal of radioactive animal carcasses at the Albany Medical College. Radioiodine was used in this experiment because of its ease of measurement, although several other isotopes, notably 3H and 14C, were also tested in the validation studies.

The College has been using the Tissue Digestor since 1994, not only saving the cost of shipment and burial of radioactive biological waste, but attracting funded grants and contracts that involve the use of isotopically labeled compounds in whole animal studies because it is able to dispose of the carcasses safely, efficiently and economically.

Analysis of Digestion of 125I- and 131I- Labeled Animal Carcasses by Alkaline Hydrolysis


Analysis of Digestion by Alkaline Hydrolysis of 125I/ml and 131I/ml Labeled Animal Carcasses


Bone seeking isotopes, such as 45calcium and 90strontium, remain with the bone shadows, which can be disposed of as dry active waste as defined by 10 CFR 61.