Abstract

In this report a toxicokinetic experiment with eight 13C-labelled polychlorinated dibenzo-p-dioxins and -furans in lactating cows is described. The test compounds were intraruminally administered as a single dose and the concentrations of the congeners in milk- and subcutaneous concentrations in other fat tissues were determined after slaughtering of the animals. Absorption from the gastrointestinal tract appeared to be rapid but the distribution phase took at least six days. The mean elimination halflife in milk fat of the congeners contributing predominantly to TEQ-values was between 40 and 50 days. The bioavailability from the dosage form used was approximately 30%. The ratio between the concentration of the TEQ-dominating congeners in body fat and milkfat varied between 1 and 2. Although the concentrations in the various fat compartments seemed to be in equilibrium to a considerable extent, as yet unexplained deviations have been found in some instances.