TOXICITY OF TECHNETIUM-99. CAN IT REPRESENT A RISK TO MAN?
Movement through the environment and toxicity to plants of technetium-99 have found considerable attention, but little information exists on toxicity of technetium to mammals although this represents a critical link in the assessment of the consequences of technetium release. High accumulation of technetium may cause damage to the thyroid. The developing organism may be another system particularly sensible to the action of technetium. Since technetium might interfere with iodine metabolism in the thyroid, its toxicity could depend on dietary iodine. These aspects were studied in rats given large amounts of technetium-99 in the diet (up to 50 mug/g food) from the beginning of pregnancy. Technetium feeding of the mothers was continued for the following pregnancies, and the newborn were maintained on Tc food after weaning from their contaminated mothers. Group of rats were maintained on a normal or on an iodine deficient diet (60 and 80 mug iodine/kg food). The parameters determined were: occurrence of pregnancy and litter size, thyroid hormones (T3, T4 and TSH) in serum, uptake of 131-J by the thyroid 24 hours after injection, histology of the thyroid and concentration of technetium in tissues of the mothers and their descendants. Selected data on toxicity of Tc in rats on a normal diet already published demonstrated that levels of 10 mug/g food or more are needed to cause damage. This low toxicity of Tc has now been confirmed for the various parameters studied. It has now also been found that very large Tc doses are also needed to enhance the deleterious effects of an iodine - deficient diet and that at levels of iodine close to minimal requirements, Tc is not much more toxic than at high levels of iodine. The amounts of Tc needed to cause damage to the thyroid are of the same order of magnitude as those expected to damage the thyroid via their beta radiation emitted. Technetium 99, therefore, does not appear to possess marked chemical toxicity in mammals, and its radiological toxicity is low. Consequently it is unlikely that contamination levels in the environment would ever reach a level that could lead to acute and subacute serious consequences in man. Carcinogenesis remains still to be studied in this respect.
Bibliographic Reference: BEHAVIOUR OF TECHNETIUM IN TERRESTRIAL AND AQUATIC ENVIRONMENTS, SEATTLE, WASHINGTON (USA), MAY 5-10, 1986 WRITE TO CEC LUXEMBOURG, DG XIII/A2, POB 1907 MENTIONING PAPER E 32986 ORA
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Record Number: 1989125027500 / Last updated on: 1987-03-01
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