As part of the actual risk assessment, the health-related limit values (ADI, ARfD) are contrasted in the context of potential exposure (MRLs). For consumers, exposure corresponds to intake of the substance being assessed via food.
For the risk assessment of pesticide residues in foodstuffs the general rule is that even the intake level of residues via foodstuffs to be expected in the worst case scenario has to be lower than the toxicological limit value (ADI or ARfD). Here both a one-time intake (normally via a meal/portion) as well as lifetime intake of pesticide residues are taken into account.
If the estimation of intake amounts results in the quantity of the active substance deemed to be critical for consumers being exceeded, the risk must then be countered via appropriate risk management measures. This would then mean, for example, an extension of the waiting time, a lowering of the application amount or even refusal of licensing and/or a ban on usage.
The often-cited “combined effect of pesticide residues” is being discussed internationally in various scientific bodies. An appropriate model for the assessment of risk to consumers is currently not available. No cumulative, i.e. combinatorial effect is to be expected in the concentration range in which pesticide residues are found. Nevertheless, a workshop was held in this regard in the winter of 2006/2007, initiated by the EFSA (European Food Safety Authority). This workshop started the process of possibly developing a model for scientific risk assessment. The starting point was that it could be conceivable that an additive effect could be observed if active substances with the same spectrum of effects are used (for example esters of phosphoric acid with regard to their cholinesterase inhibition). However, more scientific research is needed here.
Since there is currently no scientifically based model for the assessment of any possible combination/cumulative effect of active substances, robust assessment of individual substances - as practised by AGES - is the method of choice.
Residue behaviour of pesticides: