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Ecotoxicological information

Short-term toxicity to fish

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Description of key information

Weight of Evidence approach; geometric mean between the two results (experimental and QSAR results):
- 96h-LC50 = 1.87 mg/L.

Key value for chemical safety assessment

LC50 for freshwater fish:
1.87 mg/L

Additional information

Due to a suspected analytical problem in the experimental study (EU Method C.1 with GLP statement), a weight of evidence approach with ECOSAR estimation has been applied to assess the acute toxicity of the substance to fish.

In a the acute toxicity study, according to EU Method C.1 with GLP statement, zebra fish (Brachydanio rerio) were exposed to the substance at nominal concentrations of 0 (blank control), 0.3, 0.6, 1.25, 2.5, and 5 mg/L under semi-static conditions. Analytical monitoring of the concentrations was performed. An analytical problem is suspected based on the unexpectedly low analytical measurement in the old media, especially for the highest concentrations. Such behaviour is not expected for a relatively low volatility substance that is tested below its water solubility limit as is the case here. Based on this, this study should be considered as reliable but with restrictions. The LC50 value was recalculated with ToxRat Professional v2.10 using the geometric mean of the initial measured concentrations only during the study. The recalculated 96h-LC50 for fish was determined to be 2.13 mg/L.

In addition, the acute toxicity of the substance to fish was estimated using the ECOSAR v1.11 QSAR model available from the U.S. EPA. The estimation 96h-LC50 was 1.64 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 LC50 value, the geometric mean between these two results was determined to be 1.87 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.