The transfer of 239+240Pu, 241Am, 137Cs and 90Sr to the tissues of horses

Horses are important food sources in several countries however, data on their radionuclide uptake is less available than for many other farm animals. Information on the transfer of artificial radioisotopes from the environment to the food supply is necessary for internal dose assessment and assuring the safety of the population relying on this food source. This study provides data for a less studied farm animal and, in the case of Am-241 and Pu239+240, relatively poorly studied radionuclides with respect to transfer to animal products. The transfer parameters for Pu239+240, Am-241, Cs-137 and Sr-90 to the organs of 1-year old fillies, 10-year old mares and through the placental barrier into foetuses were quantified after 60-days feeding with contaminated soil or diet contaminated by a leachate solution. The transfer of radionuclides from ingested soil to tissues was generally lower, by up to three orders of magnitude, than from a diet contaminated by a leachate solution. The ingestion of soil is a particularly important source of radionuclide intake to grazing animals in the Semipalatinsk Test Site. For Am-241 there is a lack of available data, the two singular entries for mutton and beef in the IAEA handbook are higher than all values observed in the current study. The maximum observed transfer factor for Am-241 was 72 +/- 22*10(-5) d kg(-1) FW in the liver of the mare fed with leachate contaminated feed. For Pu239+240 the maximum transfer factor was 31.8 +/- 8*10(-5) d kg(-1) FW observed also in the liver of the mare fed with leachate contaminated feed. The filly fed with leachate contaminated feed had the highest transfer parameter value for Cs-137, 35.3*10(-3) d kg(-1) FW. The highest Sr-90 transfer factor was found in the ribs of the filly fed leachate contaminated feed, 720 +/- 144 *10(-3) d kg(-1) FW. The results presented in this paper can be used to improve the current internal dose estimates from the ingestion of horse meat produced in the area, however they are based on a low sample size; future studies need to use a larger number of animals.