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Short-term toxicity to aquatic invertebrates

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Description of key information

The 48-h EC50 value in Daphnia magna is 0.280 mg/L.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates
Effect concentration:
0.28 mg/L

Additional information

A total of six studies with aquatic invertebrates are available for evaluation, a flow-through study with the amphipod Gammarus fasciatus and an additional five studies with Dapnia magna.

In the first study, Gammarus fasciatus (non-standard species) was exposed to the test substance under flow-through conditions which is the preferred approach given the substances degradation behavior in water (Resource Analysts, Inc., 1990). The study was not conducted in accordance with generally accepted test guidelines but reporting is detailed and the study design shows no restrictions. Mean measured recoveries were ≥79%.

All Daphnia studies were conducted in accordance with GLP and OECD TG 202 or similar test guidelines. Two of the studies were conducted using a static test design (Haskell Laboratory, 1985c/d). In both these studies test substance analysis revealed that at the start of the test (t=0) recoveries decreased from 50-60% to 11-19%. Therefore, it was decided that no analysis was performed at the end of the 48-hour exposure period. In addition, two of the Daphnia studies were performed under semi-static conditions with renewal of test solution every 24 hours (Haskell Laboratory, 1990; Japan Food Research Laboratories, 2002). In these studies, test concentrations were not reported. The final Daphnia study was performed to get a better understanding of the behavior of the substance in the test medium and thereby improve the data in the REACH dossier submitted in 2010. In this new semi-static study additional emphasis was put on test substance analysis (a semi-static design was preferred over flow-through as the latter gave methodological difficulties). Recovery rates of test item in the fresh media (0 and 24 hours) were in the range of 96 to 105 % of the nominal values at all tested concentration levels. The recovery rates in the old media (24 and 48 hours) were in the range of 26 to 73 % of the nominal values. The geometric mean recovery rates were in the range of 50 to 82 %.

Although in the older Daphnia studies test substance recoveries at the end of the test were not determined, in most of these studies a (nominal) concentration-dependent increase in toxicity is reported. Overall, the effect concentrations obtained from the Daphnia studies are significantly lower than that observed in in Gammarus fasciatus. Therefore, despite the limitations in design and reporting, daphnids are considered to be the most sensitive species. As five studies are available with the same species and test design, a geomean effect concentration was calculated based on all reported effect concentrations. Considering that especially in the older studies test concentrations were not well-maintained and the results obtained may thus over-estimate the toxicity of the substance, this approach may be considered conservative. A calculated geometric mean 48-h EC50 value of 0.280 mg/L is considered for assessment.

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