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Ecotoxicological information

Short-term toxicity to aquatic invertebrates

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Description of key information

OECD Guideline 202, EU Method C.2, GLP, key study, validity 1:
48h-EL50 = 7.77 mg/L (loading; 95% CL: 6.85-8.90 mg/L).

Key value for chemical safety assessment

EC50/LC50 for freshwater invertebrates:
7.77 mg/L

Additional information

To assess the short-term toxicity of the registered substance to aquatic invertebrates, a set of two data are available.

The first study (LPL, 2016) was performed on the registered substance according to OECD Guideline 202 and EU Method C.2 with GLP statement. In this study, Daphnia magna (twenty daphnids: four replicates, five daphnids per replicate) were exposed to Water Accommodated Fractions (WAFs) of the test substance over a range of nominal loading values of 1.9, 3.4, 6.2, 11.1 and 20 mg/L and to a control, for 48 hours, under closed semi-static conditions. The concentrations of the test substance, represented by analytical monitoring of the main constituent, were determined by chemical analyses at the start (t=0h), at t=24h (new and old solutions) and at the end of the test (t=48h), and revealed that concentrations of this major constituent were satisfactorily maintained within or very close to ± 20% of the initial concentration throughout the test, especially at loading rates where effects on daphnids were observed. It must also be noted that in WAF preparations the concentration of the constituents having different stability and behaviours in aqueous solutions will vary during testing. Here the major constituent of the mixture was maintained to an overall satisfactory level from 66 to 77% with regards to its expected nominal initial concentration, reflecting satisfactory stability with time and within the concentrations. After 48 hours of exposure, immobilisations were 0% at 1.9 and 3.4 mg/L (loading), 15% at 6.2 mg/L (loading), 95% at 11.1 mg/L (loading) and 100% at 20 mg/L. Turbidity analysis revealed the absence of undissolved material of the test substance in test tubes and therefore confirmed the toxicity due to the test substance rather than a physical effect. Therefore, according to the results of this study, the 48h-EL50 was determined at 7.77 mg/L (loading; 95% CL: 6.85 - 8.90 mg/L)

The second data (KREATiS, 2016) is a QSAR. This QSAR used a calculation method to predict the acute toxicity of the registered substance, an UVCB substance with three major constituents, to aquatic invertebrates Daphnia sp. (48h-EL50 value).

This calculation method predicts the endpoint value which would be expected when testing the substance under experimental conditions in a laboratory following OECD Guideline 202 adapted for testing as a mixture using the WAF method. This method has previously been validated in an internal publication (Bicheral and Thomas, 2014; available in the Endpoint Study Record). This algorithm is based on a QSAR model (iSafeRat® Holistic HA-QSAR v1.5) which has been validated to be compliant with the OECD recommendations for QSAR modelling (OECD, 2004). The QSAR is based on validated data for a training set of 58 chemicals derived from 48h test on daphnids, for which the concentrations of the test item had been determined by chemical analyses over the test period. Based on the chemical structure of ketones, the three main constituents of the test substance are expected to fall on the MOA 1 regression line and they can attributed to the class of non-polar narcotic compounds (MOA 1). Further to this, the effect loading rate of the mixture is determined by using a series of calculation steps using phase equilibrium thermodynamics and excluding the non-bioavailable fraction. The 48h-EL50 value based on mobility was determined to be 4.4 mg/L. This QSAR result supports the experimental study performed on the same substance, with a predicted EL50 value slightly more conservative, validating the model for use with this substance. As the EL50 values are not significantly different (lower than a factor 2), the experimental data (LPL, 2016) was chosen as the key study. In conclusion, according to the key study, the retained 48h-EL50 value on aquatic invertebrates is 7.77 mg/L.