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Toxicity to aquatic algae and cyanobacteria

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Description of key information

ErC50 (72 h) > 100 mg/L (nominal) for of Pseudokirchneriella subcapitata (OECD 201)

Key value for chemical safety assessment

EC10 or NOEC for freshwater algae:
100 mg/L

Additional information

One study is available investigating the effects of 2,2'-[ethane-1,2-diylbis(oxy)]bisethyl diacetate (CAS 111-21-7) to algae (Vryenhoef, 2012). The study was performed according to OECD 201 (GLP) with the freshwater algae Pseudokirchneriella subcapitata. A preliminary range-finding study did not result in any effects on growth and yield up to a concentration of 100 mg/L. Test concentrations determined by GC/FID were within the range of 80-120% of nominal. Based on the results from the range-finding study a limit test with a nominal concentration of 100 mg/L was performed. No effects on growth rate and yield were recorded after an exposure of 72 h resulting in an ErC50 (72 h) > 100 mg/L and a NOErC (72 h) ≥ 100 mg/L (nominal concentrations). Analytical measurement of the test concentration showed a drop from 92% of nominal at the beginning of the study to 9% of nominal at the end of the study resulting in an ErC50 (72 h) of > 28 mg/L and a NOErC (72 h) of ≥ 28 mg/L (geometric mean concentrations). This decline was considered by the laboratory to be due to degradation of the test item, predominantly by alkaline hydrolysis at the pH of the study. However, this decline was not observed in the preliminary range-finding study and in the study with Daphnia magna. Moreover, hydrolysis at pH 7 and pH 8 is not considered to be relevant since DT50 values were determined to be greater than the duration of the study (pH 7: 152.39 d; pH 8: 15.24 d (Müller, 2011)). Nevertheless, even if hydrolysis occurred in this study it is justifiable to base the effect concentrations on the nominal values since this concentration was initially introduced in the study and reflects the effects of possible hydrolysis products as well as it would also occur in the aquatic environment. Differences between nominal and measured concentrations might be due to deficiencies in the analytical methods. The results of the range-finding study, showing no effects up to a concentration of 100 mg/L, support the conclusion that no toxicity of 2,2'-[ethane-1,2-diylbis(oxy)]bisethyl diacetate to algal species is expected.

In accordance with ECHA guidance oninformation requirements and chemical safety assessment, Chapter R.7b: Endpoint specific guidance, theErC50 endpoint is used in DNEL derivation. This is because use of values based on biomass cannot be applied to an analysis of results from a system in exponential growth without logarithmic transformation.