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Zie ook rapport 716601008

Bij de evaluatie van de toelaatbaarheid van gewasbeschermingsmiddelen spelen gegevens uit laboratorium- en veldexperimenten een belangrijke rol. Ook gegevens uit monitoring programma's kunnen bij de registratie van gewasbeschermingsmiddelen worden gebruikt. Bij de beoordeling van uitspoeling worden gegevens van monitoring programma's in de laatste stadia van de beoordeling gebruikt. Het CTB gaat bij de toelatingsbeoordeling uit van het voorzorgsprincipe. Dat wil zeggen dat een toelating pas wordt verstrekt als uit de evaluatie blijkt dat een stof voldoet aan wettelijke gestelde normen. Om bruikbaar te zijn in het evaluatieproces dienen monitoring gegevens dan ook een antwoord te geven op de vraag of een stof aan de wettelijke normen voldoet. Gezien de plaats in het evaluatieproces dienen aan opzet, uitvoering, interpretatie en evaluatie hoge eisen te worden gesteld. Dit rapport geeft richtlijnen voor elk van deze aspecten van monitoring studies. Tevens wordt een richtlijn gegeven voor het samenvatten van dergelijke studies.

The Dutch working group for the "Revision of the decision tree leaching" commissioned by the Ministry of Housing, Spatial Planning and the Environment, has worked on the improvement of the decision tree leaching, including triggers, safety factors, scenarios, models, field- en lysimeter studies and monitoring. The guidelines developed by the working group enable a more consistent and comprehensive registration process for pesticide admission. This report deals with monitoring in the decision tree. In the registration process in the Netherlands the precautionary principle will always be followed which implies that a pesticide is not registered until it has been demonstrated that it complies with legal criteria. Monitoring results will be introduced in the final phase of registration. A prerequisite is that the monitoring data comply with generally accepted quality standards and, if applicable, international Good Laboratory Practice protocols. Furthermore the monitoring programmes should be dedicated to the question whether the substance of interest will leach when it is applied according to Good Agricultural Practice. This report gives guidelines for the set-up of monitoring studies and interpretation and evaluation of monitoring data to be used in the registration process. Furthermore guidance for summarising and evaluation of monitoring results is provided.

The Dutch decision tree on leaching from soil has been re-designed to be more in line with EU guidelines on the assessment of the leaching potential of substances. The new decision tree explicitly defines reasonable worst-case conditions as the 90th percentile of the area to which a substance is applied. The tree also determines whether the median annual leaching concentration over a period of 20, 40 or 60 years complies with the EU-drinking water limit, with the length of the period depending on the application frequency. The FOCUS Kremsmnster scenario, officially adopted in the Netherlands as the national scenario, is, in the first tier, used to identify substances with a negligible leaching risk, which can then be registered without further assessment. The core of the decision tree is the second tier, in which the spatially distributed model, GeoPEARL, is used to calculate the leaching. The third tier considers the water-saturated zone up to a depth of 10 m below soil surface. As this tier did not need an update, the new approach is expected to have very little influence on the number of registered substances. Comparing the new approach with the old, we found the new first tier to be almost as strict as the old one, at least when the safety factor of 100 was not used, as in the old tree. For substances for which the leaching concentration was calculated at around 0,1 ug dm-3 using the old procedure, GeoPEARL yielded results that were approximately 10 times higher. This difference was mainly due to the annual application of the substances in the new procedure.