Model for estimating initial burden and daily absorption of lipophilic contaminants in cattle
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Series / Report no.
Open Access
Type
Report
Language
en
Date
1999-05-31
Research Projects
Organizational Units
Journal Issue
Title
Model for estimating initial burden and daily
absorption of lipophilic contaminants in cattle
Translated Title
Model voor de schatting van de initiele
lichaamsbelasting en de dagelijkse absorptie van lipofiele verontreinigingen
in landbouwhuisdieren
Published in
Abstract
Veel lipofiele organische milieucontaminanten zijn
toxisch voor mens en dier. De aanwezigheid van deze contaminanten in vlees-
en/of melkproducten bestemd voor menselijke consumptie kunnen daarom een
gezondheidsrisico voor de bevolking vormen. Om de risico's te kunnen
beoordelen worden incidenteel concentraties gemeten in bloedplasma of melk
van levende dieren. Dit rapport presenteert een computer model om
dergelijke metingen te vertalen naar de historische opname van de component
en de te verwachten residuen in vlees en melk. De methodologie is gebaseerd
op een "Physiologically Based Pharmaco Kinetic" model voor lipofiele
contaminanten in landbouwhuisdieren. Validatie van de voorgestelde methode
werd uitgevoerd m.b.v. de resultaten van experimenten waarin lacterende en
niet-lacterende koeien werden blootgesteld aan 2378-TCDD en lacterende en
niet-lacterende geiten aan lindaan en een aantal PCB congeneren. In de
bovengenoemde studies werden de dieren blootgesteld door bekende
hoeveelheden contaminant in het rumen te spuiten, waarna concentraties in
melk, bloedplasma, of vet werden gemeten in de tijd. Deze metingen werden
aangewend om de initikle belasting en de dagelijkse absorptie van de
contaminant te schatten. Validatie vond plaats door de geschatte waarden te
vergelijken met de initikle belasting en de dagelijkse absorptie die waren
opgelegd in het experiment. De resultaten laten zien dat na een bolus
injectie in het rumen de geschatte initikle belasting van het lichaam over
het algemeen lager is dan de opgelegde hoeveelheid. Dit kan duiden op
incomplete absorptie uit de darm. De geschatte dagelijkse absorptie was nul
of bijna nul voor de perioden dat de dieren schoon voedsel aangeboden
kregen. Het model is bedoeld om gebruikt te worden door veterinaire
inspecties als een 'screening' instrument om een eerste indruk te krijgen
van blootstellingen en residuen en de daarbij behorende
gezondheidsrisico's.
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.
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.
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