Dodecyl laurate

Sediment toxicity

Description of key information

No toxic effects up to the limit of water solubility (OECD 218, C. riparius); read-across

Additional information

No experimental study is available, in which the sediment toxicity of the target substance lauryl laurate (CAS 13945-76-1) was assessed.Therefore, read-across to the structurally related source substance decyl laurate (CAS 36528-28-6) was conductedin accordance with Regulation (EC) No 1907/2006 Annex XI, 1.5. The source substance is characterized by similar fatty acid and alcohol components and is therefore considered a suitable representative for the assessment of the toxicity of the target substance to sediment organisms. A detailed justification of the analogue approach is provided in IUCLID section 13.

In the available study with the source substance decyl laurate (CAS 36528-28-6), a static sediment-freshwater toxicity test according to OECD guideline 218 and GLP was performed in which the model organism Chironomus riparius, a widespread sediment-dwelling midge in freshwater habitats, was exposed to the nominal test item concentrations of 62.5, 125, 250, 500 and 1000 mg/kg sediment dry weight for 28 d via spiked artificial soil. A sediment spiking method was selected because the most likely entry route into the aquatic environment is expected to occur via particulate material carrying adsorbed substance. The artificial sediment was formulated from sand, kaolinite, calcium carbonate and finely sieved sphagnum moss peat according to the guideline, resulting in a final organic carbon content of 2.89%, slightly above the 2.0 ± 0.5%, as recommended by the guideline. Nevertheless, the organic matter content of 4.93% is nearly in line with the recommendations given in ECHA Guidance R.7b (5%; ECHA, 2017). The sediment was spiked by adding 10 mL of the test substance dissolved in the solvent Tetrahydrofuran to the dry sand component of the sediment only, which was allowed to evaporate overnight. Subsequently, all sediment components were combined, liquefied with reconstituted water and mixed on a tumble mill overnight. The spiked sediment was then dispensed to the test vessels, covered with overlying water (reconstituted) and allowed to equilibrate for 7 d prior test start. A control and solvent control (Tetrahydrofuran) were included in the test design. The measured endpoints included effects of the test item on larval development and emergence, effects on the sex ratio of emerged adult insects, development rates and on the time to first emergence. The actual test item concentrations in the sediment and overlying water were analytically verified by GC-MS/HPLC on Day -7 (for sediment only), 0, 7 and 28.

The measured test item concentrations in wet sediment was 90 – 95% of nominal on Day -7, 67-80% of nominal on Day 0, 61 – 88% on Day 7 and 40 – 59% on Day 28. The measured test item concentrations in the overlying water was < LOQ on Day 0, 7 and 28. Based on these findings, the effect values were based on the geometric mean measured test item concentrations in the sediment, resulting in test item exposure concentrations of 39.7, 81.3, 176, 383 and 787 mg/kg sediment dry weight.

At the end of the test, no statistical differences between the control and solvent control was found for any endpoint and all statistical comparisons were made against the solvent control. After 28 d exposure, no significant differences between the total emergence of adults, sex ratio and development rates in the treatments and solvent control were found. The mean times to first emergence ranged from 15 to 17 d, which was similar to that of the controls (15 and 15.5 d, respectively) but was not statistically analyzed.

Thus, the test resulted in an overall NOEC (28 d) of ≥ 787 mg/kg sediment dw (highest exposure concentration) based on development rates, total number of emerged adult insects and their sex ratio. The LOEC (28 d) was > 787 mg/kg sediment dw for all endpoints.