EXCRETION OF POLYCHLORINATED DIBENZO-P-DIOXINS AND DIBENZO-P-FURANS IN MILK OF COWS FED ON DIOXINS IN THE DRY PERIOD

A toxicokinetic experiment with four cows fed polychlorinated dibenzo-p-dioxins and -furans in the dry period for about 100 days is described. The excretion of the dioxins in milk after calving was characterized by a distribution and an elimination phase. The distribution phase lasted for about 7 days. The duration of the elimination phase depended on the kind of congener. The. longest elimination half-life was found for hexachlorinated congeners. The elimination half-life in milk fat of the congeners 2,3,7,8-TCDD, 1,2,3,7,8-PECDD, and 2,3,4,7,8-PECDF, contributing predominantly to the I-TEQ value (international toxicological equivalent to 2,3,7,8-TCDD), varied between 63 and 76 days in three of the four cows. One cow deviated strongly, with an elimination half-life between 36 and 38 days for the predominant congeners, due to a low body fat content after calving twins and two molas. The I-TEQ elimination half-life, accounting for the composition of the congeners in the milk fat, varied for three cows between 78 and 87 days.