THE EFFECT OF SUSTAINED-RELEASE BOLI WITH AMMONIUMIRON(III)-HEXACYANOFERRATE(II) ON RADIOCESIUM ACCUMULATION IN SHEEP GRAZING CONTAMINATED PASTURE

Sustained release boli with the cesium binder ammoniumiron(III)-hexacy anoferrate(II) (AFCF) were tested under practical conditions for sheep grazing on pastures contaminated with radiocesium (Cs-134+Cs-137) fro m the Chernobyl fallout, Two types of AFCF boli were developed: boli w ithout a protective surface coating intended to last 4-8 wk; and boli coated by a wax-mixture with an extended duration of 10-12 wk. From 19 89 to 1993 we measured the effect of wax-coated and uncoated boli admi nistered at various times during the grazing season to a total of 3,24 8 animals, Reductions in radiocesium levels in meat of sheep were meas ured by iii vivo monitoring. Administration of AFCF boli without a wax -coating reduced the mean radiocesium levels in lambs by 43-75% over a 4-8 wk period, and administration of the wax-coated AFCF boli reduced the mean radiocesium levels by 48-65% over a 9-11 wk period, The coef ficients of variation in meat radiocesium levels were similar in treat ed and control groups at the end of the observation period, showing th at the reduction of meat radiocesium values was homogenous throughout the treated groups, The boli giving sustained release of AFCF is a lab or-saving and cost effective countermeasure for sheep grazing radioces ium contaminated pastures.