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Ecotoxicological information

Endpoint summary

Administrative data

Description of key information

To assess the short-term toxicity to aquatic invertebrate and algae, one experimental study and two reliable QSAR results are available.

The experimental study, performed according to OECD Guideline 202 with GLP compliance, was carried out using a state of the art method, a passive dosing system using a silicone disk, maximally charged with the registered substance in an appropriate solvent, in an attempt to determine the toxic effects of this poorly soluble, volatile substance to Daphnia magna after 48 hours of exposure (static conditions, in a limit test at maximum water solubility under test conditions). No immobilisation was observed during the test at the limit concentration and the control. Despite numerous attempts using the passive dosing method, it was not possible to attain the maximum solubility in the medium that had previously been achieved in the water solubility study. Therefore, it's not possible to prove experimentally that no effect is observed up to the water solubility limit (measured at 0.43 mg/L in an OECD 105 study) but only up to the maximum achievable concentration in the present study (0.0853 mg/L).

However, in silico predictions are available.

The QSAR predictions obtained with iSafeRat® holistic HA-QSAR v1.7 has been validated with the OECD recommendations for QSAR modeling (OECD, 2004) and predict the ecotoxicological values which would be expected when testing the substance under experimental conditions in a laboratory following OECD Guidelines.

The ecotoxicological predictions were determined using a validated QSAR for the Mode of Action in question, (MOA 1, non-polar narcosis). This QSAR is based on validated data for training sets for which the concentrations of the test substance had been determined by chemical analyses over the test period. The water solubility of the substance given as the input was experimentally measured at 0.43 mg/L and does not fall within the descriptor domain of the model. However it does fall within the intermediate domain where baseline toxicity cannot be experimentally measured accurately. Moreover, the solubility is so low for the registered substance that the toxicity is likely greater than the water solubility limit. Based on a statistical k-NN approach (k = 3), the 48h-EC50 of the substance to daphnids and the 72h-ErC50 of the substance to algae are considered as greater than the subcooled liquid water solubility value. No acute toxicity is expected at levels up to the water solubility.

Enormous effort has been made experimentally to obtain a maximum solubility concentration of the substance in test medium while avoiding the creation of an emulsion which typically occurs for this kind of low solubility liquid. It is not believed that further attempts to obtain meaningful experimental results will be successful and this is supported by the in silico model which has positioned the substance in a zone where acute toxicity is no longer expected. The substance is therefore considered not to be toxic in acute studies.

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