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(W/MF209) Higher tier ecological risk assessment for rice pesticides using direct toxicity assessment on paddy samples. Sanchez, P.1, Najera, I.1, Ramos, C.1, Carbonell, G.1, Fernandez, C.1, Pablos, M.V.1, Tarazona, J.V.1, 1 ABSTRACT- Flooding/draining practices used in rice farming and timing of application influence pesticide fate and behaviour. Generic exposure scenarios developed for pesticide risk assessment by the EU are not suitable for rice pesticides. Therefore field dissipation studies are usually needed. Field studies developed for exposure assessment can also be suitable for an ex-situ evaluation of ecotoxicological risk using direct toxicity assessment of paddy waters. This paper presents a proposal for the design of rice field studies for the registration of pesticides in the EU. A decision tree, considering the application conditions and mechanisms of action has been designed. The first key element for this design is the capability to conduct direct toxicity tests on paddy water. The results of a semi-field study conducted in Spain confirmed this possibility. On the basis of the OECD standard guidelines, test protocols were modified. Recommended protocols for ambient paddy water toxicity tests on Chlorella vulgaris and Daphnia magna are presented. The second key element is the selection of a positive control. This aspect is particularly relevant for pesticides applied on drained paddies which are re-flooded after application. The decision tree includes a proposal for solving this problem, using a combination of up to three different consecutive treatments in the positive control plots. This combination covers the key ecological elements that can be affected. Results confirmed that direct measures of toxicity of paddy waters are cost/effective tools to be included in a specific protocol for higher tier effect assessment of rice pesticides. Key words: rice pesticides, direct toxicity assessment, EU registration, n/a |
