INVESTIGATIONS ON THE TRANSFER OF SELECTE D DIBENZODIOXINS AND DIBENZOFURANES (PCDD F) AFTER ALL SUPPLEMENTATION INTO THE MILK OF LACTATINGCOWS/

Approaches for determining the carry over rate of polychlorinated dibe nzodioxin- and furan congeners are possible by comparing coherent data as regards feedingstuff and milk fat by assuming a typical feed ratio n. However, controlled experiments with individual lactating cows kept under environmental conditions are burdened with methodical error sou rces. In this study carry over trials on the relevant congeners of the PCDD/F-expositions originating from the environment were performed. U sing specially labelled congeners (13 C-6, 37 Cl-4) they show, besides the individual carry over rate, also the kinetics of depot buildup an d excretion with the milk fat as a function of supplementation time. W ith the pattern ''one cow = one congener'' a substance optimized GC/MS measurement is feasible. The individual carry over rates of the conge ners (cows orally supplemented on wheat starch: 50 and 100 ng/day) wer e <1 % for 2,3, 7,8-TCDF and 1,2,4,6,7,8-HPCDF; 1-5 % for 1,2, 3,7,8-P eCDF; 5-10 % for HxCDF and HxCDD without pos. 6; 10-15 % for 1,2,3,7,8 -PeCDD and 1,2,3,6,7,8-HxCDD; 25-35 % for 2,3,4,7,8-PeCDF and >35 % (u p to 60 %) for 2,3,7,8-TCDD. As approximately 84 % of the toxic equiva lents (NATO/CCMS) in milk fat are condensed in 5 congeners, the carry over rate for this couple of 3 dioxins and 2 furans can be calculated as much as 19.4 %. On the basis of this value it can formally be concl uded, that for observing the background value of approximately 0.6 pg iTE/g milk fat feedingstuffs must not be contaminated with quantities exceeding 0.15 ng iTE/kg dry matter.