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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

Calculation method, iSafeRat® Holistic HA-QSAR v1.4, key study, validity 2:
72h-ErL50 = 17 mg/L

Key value for chemical safety assessment

EC50 for freshwater algae:
17 mg/L

Additional information

To assess the toxicity of the registered substance to aquatic algae, one data endpoint is available.

This data (KREATiS, 2015), assessed as a key datapoint, is a QSAR. This QSAR used a calculation method to predict the inhibition of growth to algae of the registered substance, a multiconstituent mixture of known composition (72h-ErL50 value), which would be expected when testing the substance under experimental conditions in a laboratory following OECD Guideline 201 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 v1.4) 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 40 chemicals derived from 72h ErC50 test on algae, 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 and alcohols, 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 WAF is determined by using a series of calculation steps using phase equilibrium thermodynamics and excluding the non-bioavailable fraction. The 72h-ErL50 value based on growth rate was determined to be 17 mg/L.

In conclusion, as the same QSAR model was validated for the "short-term toxicity to aquatic invertebrates" endpoint with an experimental study and the result from this prediction was observed to be similar and more conservative to those obtained from the experimental study, this result can be used with high reliability. Therefore, the 72h-ErL50 value on algae was considered to be 17 mg/L.