Transfer of planar and non-planar chlorobiphenyls, 4,4′-DDE and hexachlorobenzene from blood to milk and to suckling infants

The transfer coefficients of tetra- and hexachlorobiphenyls (PCB-54; -80; -155; and -169), HCB and 4,4′-DDE between milk and blood were monitored for eight weeks in sheep previously administered with these compounds by intramuscular injection. Analyses were performed by high resolution gas chromatography. The milk/blood ratio on a fat basis was close to 1 for HCB, over 1 for 4,4′-DDE, PCB-155, and -169 and below 1 for PCB-54 and -80. It is speculated that the deviation from the ratio 1 results from the interactions of organochlorines with (lipo)proteins in blood and/or milk. In milk, the enrichment of 4,4′-DDE, PCB-155 and -169 was observed. The relative toxicity expressed by the toxic equivalent (on a fat basis) was approximately 2.5 times higher in milk than in blood.