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Ecotoxicological information

Short-term toxicity to aquatic invertebrates

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Description of key information

Weight of Evidence approach; geometric mean between the two results (experimental and QSAR results):
- 48h-EC50 = 4.65 mg/L.

Key value for chemical safety assessment

EC50/LC50 for freshwater invertebrates:
4.65 mg/L

Additional information

Due to the unexpected and inconsistent loss of substance observed in the static experimental study (EU Method C.2 with GLP statement), a weight of evidence approach with ECOSAR estimation has been used to assess the acute toxicity of the substance to aquatic invertebrates.

In the acute toxicity study, performed according to EU Method C.2 with GLP statement, Daphnia magna were exposed to the substance at nominal concentrations of 0 (blank control), 3.2, 5.0, 6.4, 10.0, 12.8 and 20.0 mg/L under static conditions. Analytical monitoring of the concentrations was performed at t = 0h and t= 48h. This study is considered invalid because the test method used was not appropriate, the substance was apparently lost rapidly during this static test although similar final concentrations of the test substance were found in all test solutions at the end of the study. This profile would not be expected for a relatively low volatility substance tested below the water solubility limit as is the case here. The EC50 value was therefore recalculated with ToxRat Professional v2.10 using the initial measured concentrations. The recalculated 48h-EC50 for Daphnia magna was determined to be 8.09 mg/L (95% CL: 7.39 - 8.87 mg/L).

In addition, the short term toxicity of the substance to daphnid was estimated using the ECOSAR v1.11 QSAR model available from the U.S. EPA.

The estimation 48h-LC50 was 2.67 mg/L (esters class), calculated from a measured log Kow value (4.3) and a linear regression. The substance falls within the applicability domain and therefore the predicted value can be considered reliable.

To obtain a more reliable EC50 value, the geometric mean between these two results was determined to be 4.65 mg/L.

Further investigation is ongoing on this difficult substance in order to determine whether instability or analytical issues account for the rapid loss observed under ecotoxicological test conditions.