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Short-term toxicity to aquatic invertebrates

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Description of key information

 Concentration levels of test substance that induced effects on crustaceans exceeded the maximum solubility of test substance in water (<0.64 mg/l).

Key value for chemical safety assessment

EC50/LC50 for freshwater invertebrates:
4.5 mg/L

Additional information

The test substance was assessed for acute toxicity to invertebrates according to EU Method C2 under static conditions for 48 hours.

After a limit test, two full tests were performed with daphnids exposed to 4.5 to 100 mg/l and 0.1 to 4.5 mg/l, respectively. In the limit test, the test solution was prepared using Tween 80 as a dispersent. No additives were used in the full tests. The test consisted of two vessels per group containing 10 daphnids per vessel. Samples for analysis were taken at the start and the end of the full tests and analysed for determination of Total Organic carbon (TOC).

A part of the organisms became immobilised during the limit test in both the filtered and the unfiltered solution.

During the first full test, no effect on mobility of Daphnia magna was observed at any of the concentrations during the first 24 hours of exposure, while significant numbers became immobilised in all test solutions during the last part of the 48-hour test period. There was no clear relation between response and test concentration. In the second full test, however, no immobilisation was induced by any of the concentrations tested, including 4.5 mg/l.

TOC analyses showed that during the second full test, Daphnia magna were exposed to a higher average concentration of test substance in the water phase of the nominal concentration of 4.5 mg/l, while no effect on mobility was observed.

In conclusion, concentration levels of test substance that induced effects on crustaceans exceeded the maximum solubility of test substance in water (<0.64 mg/l). These effects were not test concentration related, but probably caused due to physical damage to or mechanical obstruction of the swimming apparatus of the organisms exposed caused by flocculation of the undissolved fraction of the test substance. Hence, the 48h EC50 for Daphnia magna was beyond the maximum solubility of the test substance in water.