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Short-term toxicity to aquatic invertebrates

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Description of key information

Four acute daphnia tests have been performed to evaluate toxicity of the sodium salt of coco fatty acids 2-sulfoethylester. In the Key study an EC50 of >48 mg a.i./L has been derived using the weighted mean of the measured dissolved concentration. At concentrations above the EC50 precipitates of test substance were observed.  

Key value for chemical safety assessment

EC50/LC50 for freshwater invertebrates:
48 mg/L

Additional information

Four acute daphnia tests have been performed to evaluate toxicity of the sodium salt of coco fatty acids 2-sulfoethylester. EC50 values ranging from 7.9 to > 48 mg a.i./L were observed. In two studies, the effects observed were addressed to indirect effects of precipitates adhering to the carapac or antennae of the daphnia. In the Key study test solutions of Fatty acids, C12-18 and C18-unsatd., 2-sulfoethyl esters, sodium salts (CAS no 85408-62-4) which is a substance very similar to coco fatty acids 2-sulfoethyl sodium salt were prepared containing a nominal concentration of 0, 18, 32, 56, 100 and 180 mg/L of test substance.

After preparing the test solutions they were left for 1 hour to allow for settling of precipitate. Measured concentrations using LC-MS are reported as time weighted averages for both total and dissolved: Total measured concentrations: 15.7, 29.1, 49.8, 101.6 and 169.2 mg/L. Dissolved measured concentrations: 10.8, 19.6, 34.6, 50.1 and 80.6 mg/L. An EC50 of >48 mg a.i./L has been derived using the weighted mean of the measured dissolved concentration. None of the concentrations caused 100% immobility. Immobility in the Daphnia is due mainly to indirect effects. Read-across from the source chemical Fatty acids, C12-18 and C18-unsatd., 2-sulfoethyl esters, sodium salts (CAS no 85408-62-4) to the target chemcial coco fatty acids 2-sulfoethyl sodium salt is considered to be justified as both substance are very similar and the source chemical contains a higher content of longer alkyl chain products which are known to more toxic than the shorter alkyl chain products. The conclusion that the source chemical is more toxic than the target chemical is considered sufficient to select the more toxic derivative as the worst-case representative in the hazard assessment of both substances. For this reason read-across of ecotoxicity results of the source chemical (C12-18 and C18-unsatd) to the target chemical (Coco) is considered to be justified without the introduction of an additional safety factor.