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Short-term toxicity to aquatic invertebrates

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Description of key information

The mean of the lower limit of the 48h EC50, 145 μg/L of partially unsaturated IQAC, DMS quaternised

and the 48h EC 50 of 65 μg/L is used as a realistic 48h EC50.

The realistic 48h EC50 is calculated to be 105 μg/L.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates
Effect concentration:
105 µg/L

Additional information

The 48 –hr-acute toxicity of Oleic-acid based IQAC, DMS quaternised to Daphnia magna was studied under static conditions. Daphnids were exposed for 48 hr. The 48 – hour EC50was 87 µg/l (48 hour EC50 = 65 µg/l based on a. i. -content of 75%), the 24h EC50 was 270 µg/L. Further information is available from the read across substance partially unsaturated IQAC, DMS quaternised (CAS 86088-85-9). The 24h EC50 is determined to be between 450 and 900μg/L. In a third test , the 24h EC50 is determined to be <1000 µg/l.

The difference between the three test results is a factor of more than 10. Taking into account that the only difference of the registration substance, oleic-acid based IQAC, and the read across substance, partially unsaturated IQAC, DMS quaternised is the chain-length distribution and the number and location of the C=C double bonds (see 1.1.2), this difference cannot be explained by the difference in fatty acid chains.

According to REACH Endpoint specific Guidance R.7b, pp24, it is not recommended to compare 24h EC50 values to 48h EC50 values.

Therefore the 24h EC50 were extrapolated to 48h EC50. Assuming the same slope of the dose-response curve for the acute tests (3.1 based on the nominal concentrations), the results of the 48h exposure of daphnids are calculated to be 145 – 290 μg/L and <322 μg/L respectively. The mean of the lower limit of the definite extrapolated 48h EC50, 145μg/L, and the 48h EC 50 of 65μg/L (based on 75% a.i. content) is used as a realistic 48h EC50. The realistic 48h EC50 is calculated to be 105μg/L.

Justification for read-across:

The structural similarities between the source and the target substances presented above are the basis for the read-across hypothesis. Adequate, reliable and available scientific information indicates that the source and target substances have similar physicochemical properties, ecotoxicological and toxicity profiles and thus support the read-across hypothesis.

Both substances are UVCB substances, produced by a similar process resulting in main constituents of the same structure, varying in the degree of saturation and chain length (C16 and C18 and mainly C18, for source and target substance, respectively). Given the underlying identical generic structure (outlined in chapter 1 and 2), similar absorption following oral or dermal uptake and the same metabolic patterns are expected for source and target substance. The findings from toxicokinetic data confirm that the discussed IQAC source and target substances are only poorly absorbed after oral application and rapidly excreted. There was no tendency for accumulation of the substance in the body of the test animals.

In conclusion the results obtained from source substance (partially unsaturated IQAC, DMS quaternised) are considered a reliable source to cover endpoints of the target substance (oleic-acid based IQAC, DMS quaternised). Beyond, the dose descriptors obtained from these studies performed on the source substance are considered as an appropriate starting point for deriving the respective PNECs.

A more detailed justification for read-across is outlined in a separate document:

“Justification for read-across - toxicological information”, is attached to the endpoint summary acute toxicity and provided in chapter 13 of Technical dossier.