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Pesticides in foods: Risk assessment of multiple residues is to be optimised

36/2005, 15.11.2005

At the second BfR Consumer Protection Forum scientists and consumer protectionists discussed new concepts and approaches

Testing of foods for pesticide residues frequently reveals the remains of several active substances in fruit and vegetables - multiple residues. The impact of a mixture of various active substances on human beings has only been described scientifically for a few groups of active substances. Suitable concepts must, therefore, be developed in order to permit a more comprehensive health assessment of multiple residues in foods in future. At the second Consumer Protection Forum of the Federal Institute for Risk Assessment (BfR), scientists and consumer protectionists came together to discuss suitable assessment models in Berlin on 9 and 10 November. One of the approaches discussed is also used in other countries: substances with the same mechanisms of action are added together and substances with different effects are treated as individual substances.

Like all chemical remains pesticide residues in foods are not desirable. However, in technical terms they cannot always be avoided. Residues of several active substances may occur for various reasons. Different pesticides are applied consecutively over time to combat various pests. Combination products with a specific effect are used or agricultural products of different origin are mixed together prior to their going on sale. These are just a few causes.

The following principle applies: pesticide residues may not impair the health of the consumer. Hence, maximum levels have been set for the individual substances that definitely do not constitute a health risk for human beings. If a maximum level is exceeded, the food may no longer be offered for sale.

But what about the health assessment of the residues of several active substances in a sample - even when they are below the safe maximum levels? "Already now BfR uses aggregate maximum levels for a few groups of active substances when assessing multiple residues", comments Dr. Ursula Banasiak, Head of the BfR Department Safety of Substances and Preparations. This is possible for certain fungicides and insecticides that have the same mechanism of action. Most of the substances are still, however, assessed on an individual basis. The derived values for long-term intake as well as the acute toxicity of the active substance are used as the health assessment parameters when setting maximum levels. There are normally two to three-digit safety margins between the set maximum levels and the concentrations that are toxic in animal experiments.

BfR is developing a concept for the health assessment of multiple residues which draws on international expertise and experience. For this concept comprehensive data on exposure are required. Exposure is understood to be the amount of a substance that the consumer comes into contact with from all relevant sources. When it comes to the assessment of multiple residues of pesticides up-to-date data on consumer eating habits are very important. Tests on mechanisms of action and possible interactions between substances are also needed. Based on these data groups of active substances with the same mechanism of action can be identified and equivalence factors derived for the weighting of the individual substances according to their toxicity.

"I would like to stress that we are talking about a residual risk and improvements to assessment practice - here we are in the precautionary area", said BfR President Professor Dr. Dr. Andreas Hensel. The Forum had also underlined the fact that what was needed was a uniform assessment concept for multiple residues coordinated on the European level. Hensel concluded, "Agreement was reached on the fact that a comprehensive assessment model must have a scientific basis".

Further information on the subject of multiple residues can be accessed on our website www.bfr.bund.de under Press/Background information.

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