Session 4
Compliance of feed limits, do not means compliance of food limits

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L.W.D. van Raamsdonk1, M. J. Zeilmaker2, G.A.L. Meijer3, M. Rennen4, J. C. H. van Eijkeren2, L. A. P. Hoogenboom1 and M. Mengelers5

1 RIKILT-Institute of Food Safety, Wageningen, The Netherlands,
2 RIVM National Institute of Public Health and the Environment, Bilthoven,
3 Animal Sciences Group of Wageningen UR, Division Nutrition and Food, Lelystad,
4 TNO, Division Quality of Life, Zeist,
5 Food and Consumer Product Safety Authority (VWA), The Hague.

One reason, among others, to set limits to contamination levels of chemicals in feeds and feed ingredients is to ascertain that reasonable levels of those chemicals can be achieved in animal products intended for food. Limits in food are set for some chemicals to avoid high exposure levels for human consumption. There is a limited range of chemicals for which limits in feed as well as in food are provided: dioxins, aflatoxinB1/M1, cadmium, lead, and 13 “old” pesticides (Directive 2002/32/EC). In most cases the limits in feed and those in food are not empirically related to each other. This situation is due to the different backgrounds of feed and food limits, and to the lack of sufficient data for carry-over from the feed, through the intestine and the metabolism of the animal to the target organ or product. More recently tools for calculating this carry-over and the final level in the target organ became available, in combination with relevant data.

A calculation model for simulating the carry-over from feed to food has to be designed and adjusted individually to every combination of chemical compound – animal – target product. It is vital to have the correct data and a possibility to define the correct mathematic model for the actual calculations. Therefore, a group of Dutch research institutes together with the VWA is developing an expert system for performing the complex process of collecting the necessary data, deciding on the simulation model and performing the calculations.

This expert system consists of:

1. Calculation models. Time based kinetic-physiologic [1], exponential and linear models, as well as steady state models and a comprehensive database on carry-over [2] are available.
2. Decision tree. Based on type of question, level of expertise and the combination chemical compound – animal – target product, a decision tree guides the user to the optimal choice for a calculation model.
3. Knowledge grid. A grid ordered along chemical compounds and target animal/organ consists of indication for the level of expertise in every combination. This grid shows several levels of detail.
4. Databases. Data on consumption amount, composition of the daily diet of major farm animals, background levels of chemical compounds in feeds, overview of legal limits, and data on composition of animals and production of animal products are collected in order to provide data for calculations.

The expert system is currently in development and prototypes of parts are available. Simulation models for specific situations are operational, such as dioxin carry-over to milk and eggs, cadmium carry-over to kidney (cattle), aflatoxin B1 to milk (M1). During the lecture several examples of calculation will be shown.

The expert system is capable of achieving several goals:

1. estimating the compliance between feed and food limits,
2. calculation of the optimal contamination level throughout the production chain (ingredient – feed – product),
3. deciding on the optimal choice for a calculation model for a particular incidence (and possible risk) in the chain,
4. give an overview of expertise levels for individual chemical contaminants and groups of contaminants.

References:
[1] Eijkeren J. C. H. van, M. J. Zeilmaker, C. A. Kan, W. A. Traag en L. A. P. Hoogenboom, 2006. A toxicokinetic model for the carry-over of dioxins and PCBs from feed and soil to eggs. Food Additives and Contaminants 23: 509–517
[2] Leeman, W.R., K. J. Van Den Berg, & G. F. Houben, 2007. Transfer of chemicals from feed to animal products: The use of transfer factors in risk assessment. Food Additives and Contaminants 24(1): 1–13