The OECD 308 Guideline defines laboratory testing to assess the transformation of organic chemicals in aquatic sediment systems in the dark. Including natural sunlight and eventually algae in aquatic sediment study designs may enhance simulation of genuine environmental conditions. As a positive side effect, such modifications may ascertain shorter half-lives or disappearance times for test compounds. Innovative Environmental Services (IES) Ltd, Switzerland, as an independent GLP-CRO, brings more than ten years of experience with aerobic aquatic sediment studies under simulated natural sunlight conditions and has recently developed and successfully employed a respective functional set-up containing algae. Nevertheless, while OECD Guidelines for testing of chemicals are designed for examination of environmental fate and behavior of a single chemical compound per study and test system, in the field respective compartments are often treated with several active compounds of differing modes of action. Such combinations of pesticides, <i>e.g.</i> fungicides and herbicides, are applied either sequentially, or as tank mixtures. Hitherto, possible cumulative and/or synergistic effects and interactions between one and the other compound(s) in the environment have been very rarely investigated. As of 2019, IES Ltd in conjunction with RWTH Aachen University, Germany, is investigating the influence of tank mixtures on the rate and route of degradation of specific pesticides in water/sediment and in soil. An overview on intermediate results will be presented. Additionally, the experimental road of developing a water/sediment system containing algae, as well as the results obtained by an aerobic OECD 308 study with algae on the degradation of a persistent insecticide will be shown.

Test design modifications to assess the transformation of chemical compounds in aquatic sediment (OECD 308) and soil (OECD 307) test systems: Simulated natural sunlight, algae, pesticide mixtures

2019 Fall National Meeting

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