Fatty acids, coco, 2-sulfoethyl esters, sodium salts

Toxicity to aquatic algae and cyanobacteria

Description of key information

The toxicity of coco fatty acids 2-sulfoethyl ester, sodium salt to algae was tested according to OECD guideline 201. The ErC50 was observed to be >4.8 mg a.i./L and the ErC10 was observed to be 0.3 mg a.i./L

Key value for chemical safety assessment

EC50 for freshwater algae:

4.8 mg/L

EC10 or NOEC for freshwater algae:

0.3 mg/L

Additional information

In this study the effects of Fatty acids, C12-18 and C18-unsatd., 2-sulfoethyl esters, sodium salts (CAS no 85408-62-4) on the growth of the freshwater green alga Pseudokirchneriella subcapitata were tested

The result of the algae test with Fatty acids, C12-18 and C18-unsatd., 2-sulfoethyl esters, sodium salts is read-across to coco fatty acids 2-sulfoethyl sodium salt. 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 chemical coco fatty acids 2-sulfoethyl sodium salt is considered to be justified as both substances are very similar and the source chemical contains a higher content of longer alkyl chain products which are known to be 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.

The test substance has limited solubility in water and ISO media. Significant losses of the test substance over the 72 hr testing period were observed. At 0 hours the measured concentration of each chain length dissolved in solution is close to the expected nominal concentration taking into account the chain length distribution of the test item. The concentrations of C₈, C₁₀and C₁₂remain stable over the test period however there is a significant decrease in the concentration of chain lengths ≥ C₁₄in solution. Comparisons between solutions with and without algae reveal a significant decrease in the total concentration remaining at 72 hours when algae is present (30% of the 100 mg/L solution remaining compared to 65% for the same concentration without algae).

For the definitive study final test media concentrations were prepared of 0, 3, 10, 30, 100 and 300 mg/L. Cell concentration was determined at 48 and 72 hours. Test concentrations were determined every 24 hours by Liquid Chromatography/Mass Spectroscopy (LC/MS). The EC50-value for specific growth rate inhibition (ErC50) after 72 h was >= 4.87 mg/L (dissolved measured concentrations) based on active ingredient concentration. The NOEC value for specific growth rate inhibition was >= 0.31 mg/L (dissolved measured concentrations) based on test substance concentration and 0.3 mg/L based on active ingredient concentration.