Evaluation of soil ecotoxicity tests with functional endpoints for the risk assessment of plant protection products

This paper outlines the state-of-the-art in discussing tests with functional endpoints for the soil compartment for regulatory purposes. In spite of the fact that organic matter decomposition is one of the most important functions in the soil ecosystem, this process has not been the subject of a test requirement for risk assessment of plant protection products until very recently. Since EU Directive 91/414/EEC concerning the placing of plant protection products on the market requires in its Annex III, point 10.6.2 (entitled “Effects on other soil, non-target macro-organisms”), the evaluation of effects on organic matter breakdown, there is an urgent need to fulfil this requirement. The use of functional endpoints in terrestrial model ecosystems is also under discussion in the framework of the notification process for chemicals. Four potential methods (bait-lamina-test, litterbag test, minicontainer test, cotton-strip assay) taken from ecological literature are briefly reviewed and evaluated in this paper using several defined criteria regarding their usefulness for registration purposes. In this context, areas for further research are identified. The insecticide Dimilin (a.i. diflubenzuron) is used as an example to show how such a test improves risk assessment. Therefore, it is strongly recommended that a guidance paper describing the main principles of at least one test method on organic matter decomposition should be written in order to realise the EU requirement.