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PW09 Exposure and Effect Endpoints
(PW149) Use of a multilevel effects approach to evaluate the individual and joint toxicity of two insecticides to the midge Chironomus riparius (Chironomidae, Diptera).
Agra, A. R.1, Nogueira, A. J. A.1, Soares, A. M. V. M.1, 1 Universidade de Aveiro, Campus de Santiago, 3810-193, Aveiro, Portugal
ABSTRACT- Exposure to agrochemicals in the aquatic systems may occur due to runoff and spray drift associated with precipitation and application events. The widespread use of pesticides with different target organisms together with the introduction of new formulations of biologically active substances inevitably leads to a mixture of pesticides which toxicity effects to the non-target organisms that are difficult to assess. In many cases chemical mixtures may lead to greater non-target risk than that predicted based on traditional risk assessments for single chemicals. Toxicities of two insecticides, an organophosphate (chlorpyrifos) and a pyrethroid (cypermethrin) were evaluated individually and in combination using larvae of the aquatic midge, Chironomus riparius. The effects of short-term (48-h) and chronic (6 days) exposures were determined at different levels of biological organization. Biochemical effects were investigated through the measure of acetylcholinesterase activity. Growth, water content and dry weight of the larvae were used as morphological parameters and burrowing capacity was the behavioural effect assessed. Time to emergence and the emergence rate of adults were used as descriptors of population-level effects. Results of this study can provide new insights into the interactions of pesticide mixtures leading to cumulative toxicity to aquatic biota, thereby improving the evaluation of pesticide effects on aquatic environments.
Key words: cypermethrin, Chironomus riparius, chlorpyrifos, mixtures
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