Concentration changes for 5 PCDD/F congeners after administration in beef cattle

Ten cattle were treated with daily doses of five PCDD/F congeners, over a 4 week period. Four control animals were not treated. They were subsequently slaughtered as three groups, at 5, 18 and 31 weeks after the first dose. A ll congeners showed an increase in concentration within animal tissues when sampled at 5 weeks post-dosing. Concentrations had reduced after 18 weeks and there was a further small reduction after 31 weeks. Halflives for each congener were calculated at 13-21 weeks (93-148 days). Concentrations of co ngeners were different in the various tissues analysed. At 5 weeks after do sing commenced, concentrations in sub-cutaneous fat and in perirenal fat we re close to 40 ng/kg (a predicted level based on 50% absorption of the dose d compounds). Concentrations on a fat basis in muscle tissue and liver were , however, about 5 and 10 times higher, respectively. The concentrations fo und in muscle tissue and liver samples taken at 18 and 31 weeks were approx imately twice that found in fat deposits, thus the differences were still a pparent, but at a reduced level. It is possible that the distribution phase was incomplete and that PCDD/Fs remained predominantly in association with circulating blood lipids rather than in equilibrium with depot fat. It fol lows that if livestock were recently exposed to PCDD/Fs (for example, throu gh the consumption of contaminated feed), the analysis of depot fats would not necessarily provide a reliable indicator of the concentrations of PCDD/ Fs in edible tissues. Crown Copyright (C) 2001 Published by Elsevier Scienc e Ltd. All rights reserved.