ECO42: Fate-directed toxicity testing and risk assessment of UVCBs

Description

The objectives of this project are (1) to develop and test new approaches for fate-directed ecotoxicity assessment of UVCBs based on new combinations of analytical methods, dosing methods, fate directed fractionation, toxicity testing and models, (2) to conduct a case study on selected UVCBs and to develop a generic risk assessment strategy for UVCBs and (3) to cross fertilize and partially align the ongoing research activities related to UVCBs at three European research institutes. The short-term expected outcome is scientific and technical progress that will support fate-directed toxicity testing of UVCBs, and a case study that will illustrate a fate-directed risk assessment methodology for selected UVCBs. The long-term benefit of the project will be more scientifically informed and higher quality testing of UVCBs, and thus an improved basis for future environmental risk assessment of UVCBs.

Scientific and technical basis for the project

Fate directed toxicity testing means toxicity testing of the relevant UVCB constituents and/or the relevant mixture composition when taking modifying fate processes into account, with the overall aim to increase the environmental relevance of obtained toxicity test results. Within UVCB-FATETOX we will address this in different ways:

Sample introduction. The way a test substance is introduced into an aqueous media can be crucial for the outcome of the test. While substance introduction is already crucial and challenging for single compounds, it is even more important for complex mixtures and UVCBs. Often the WAF method is used for UVCB exposure but this approach has a number of disadvantages. It is a challenge to maintain stable water concentrations and consequently keep the composition proportional to the start conditions. Hydrophobic constituents will bioaccumulate more than less hydrophobic constituents in the test organism which will change the composition pattern in the water, and therefore depletion of specific constituents can occur. We therefore will use and evaluate a passive dosing system for the exposure control of UVCBs. In UVCB-FATETOX, we will introduce the UVCBs as WAF (dispersion, dissolution & partitioning) and compare it to passive dosing (partitioning). Modern analytical methods will then be applied to determine and visualize composition differences of the dissolved UVCB mixtures in the aqueous media. In all subsequent experiments, the sample introduction principle will be chosen very carefully based on (i) the relevant exposure scenario, (ii) high reproducibility, (iii) aiming for sufficiently constant exposure during the test and (iv) avoiding non-dissolved UVCB in the test media.

With case studies the methods developed will be applied both on the whole UVCB substance but also on discrete chemicals with structures that are representative of specific blocks (constituent approach). These studies will show the advantages and disadvantages from a technical feasibility and hazard and risk assessment point of view for UVCB assessment. These assessments include exposure modelling to predict the environmental concentration (PEC). Advanced Analytical Chemistry will be crucial in this project and we expect it to become a keystone in the future risk assessment of UVCBs. The project will include biomimetic Solid Phase Micro Extraction (SPME) directed at determining the baseline toxic potential and bioaccumulation potential of UVCBs, Headspace-SPME applied to biodegradation and bioaccumulation studies and GCxGC coupled to FID and MS for separating UVCBs into its individual components or at least into a very large number of generic structures (blocks). If needed also LC-MS, LCxLC-QTOFMS techniques will be applied. We will give special attention to the optimal alignment between analytical methods and the experiments. Additionally, we envisage that analytical methods in combination with models can be used to link fate and toxicity studies in situations where it is difficult or not possible to physically couple fate and toxicity studies.