Model for estimating initial burden and daily absorption of lipophilic contaminants in cattle
Model voor de schatting van de initiele lichaamsbelasting en de dagelijkse absorptie van lipofiele verontreinigingen in landbouwhuisdieren
Freijer JI, van Eijkeren JCH, Sips AJAM
RIVM Report 643810005
Many lipophilic organic contaminants in the environment are toxic for humans and animals. The presence of this class of contaminants in animal products (meat and milk) intended for human consumption thus involves health risks to the general population. In order to assess these risks, concentrations of contaminants in domestic animals are monitored by occasional measurements on blood (plasma) or milk of living animals. A computer model to translate such measured concentrations into historical absorption and burden of the compound, and into the future residues expected in meat and milk products, is described. The methodology is based on a Physiologically Based Pharmaco Kinetic model for lipophilic contaminants in domestic animals. Validation of the proposed method was carried out using the results of experiments in which lactating and non-lactating cows were exposed to 2378-TCDD, and lactating and non-lactating goats to lindane and a number of PCB congeners. In the above-mentioned experiments, the animals were internally exposed by injecting known amounts of contaminant into their rumen. Concentration measurements were used to estimate the initial burden and the daily absorption of the PBPK model. Validation was carried out by comparing estimated initial burden and the daily absorption with the doses imposed in the experiment. The results show that the estimated initial body burdens are lower than the doses imposed by the bolus injection in the rumen. This indicates that absorption from the intestine is probably incomplete. The estimates of daily absorption correspond to zero or trace values for the stages in which the animals were fed with food devoid of the contaminant. The model is intended for use by veterinary services/inspections as a screening tool to estimate exposures and residues.