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.

Eight 13C-labelled PCDD's and PCDF's dissolved in olive oil were administered intraruminally to four lactating cows as a single dose. Milk and body fat concentrations were monitored for 93 days. Mean elimination half lifes of most congeners varied from 27–49 days. Bioavailability varied with the degree of chlorination from 36 - 2%.

Eight C-13-labelled PCDD's and PCDF's dissolved in olive oil were administered intraruminally to four lactating cows as a single dose. Milk and body fat concentrations were monitored for 93 days. Mean elimination half lifes of most congeners varied from 27-49 days. Bioavailability varied with the degree of chlorination from 36 - 2%.