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Toxicity to microorganisms

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Description of key information

NOEC (14 d) > 29.1 mg/L (OECD 301 B, Toxicity Control)

Key value for chemical safety assessment

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One study for the substance itself and one read across study investigating the toxicity of 3,5,5-trimethylhexanoic acid mixed tetraesters with pentaerythritol and valeric acid (CAS 131459-39-7) to activated sludge microorganisms are available. For 2,2-bis[[(1-oxoisononyl)oxy]methyl]-1,3-propanediyl diisononanoate (93803-89-5) the ready biodegradability study is used to derive a NOEC for the toxicity to activated sludge microorganisms. In accordance with the ECHA Guidance R.7b (ECHA, 2012) the result from a biodegradation study can be used to derive a NOEC if a compound degrades well in a ready biodegradability test, or does not inhibit the degradation of a positive control at a certain concentration (biodegradation > 25%). For 2,2-bis[[(1-oxoisononyl)oxy]methyl]-1,3-propanediyl diisononanoatea biodegradation test according to OECD 301B is available (Muckle, 2012). The toxicity control, containing 25 mg/L inoculum, 29.1 mg/L of the test substance and 26 mg/L of the reference material aniline attained 34.3% degradation after 14 days of incubation. Hence, the substance is not toxic to aquatic microorganisms in the toxicity control and the test item concentration of 29.1 mg/L can be used to derive the NOEC (14 d) of ≥ 29.1 mg/L.

Additionally, in accordance to Regulation (EC) No 1907/2006 Annex XI, 1.5 a read across to the structurally similar analogue substance 3,5,5-trimethylhexanoic acid mixed tetraesters with pentaerythritol and valeric acid (CAS 131459-39-7) was conducted. The substance consists of the same alcohol component(pentaerythritol) and similar fatty acid chain lengths as the target substance (C9iso for the target substance compared to C5-6 for the source substances, respectively).

The test was performed according to OECD 209 (Mead, 1999) with activated sludge of a predominately domestic sewage treatment plant. Mircoorganisms were exposed to a limit concentration of 1000 mg/L for 3 h. No effects on the respiration rate of activated sludge microorganisms population were observed. Therefore, this study resulted in an EC50 (3 h) of > 1000 mg/L (nominal). The NOEC (3 h) was derived to be ≥ 1000 mg/L (nominal).

Based on the results from the substance itself and from structurally related read-across substances (in accordance to Regulation (EC) No 1907/2006 Annex XI, 1.5), characterized by a similar ecotoxicological profile and structure, it can be concluded that 2,2-bis[[(1-oxoisononyl)oxy]methyl]-1,3-propanediyl diisononanoate will not exhibit microbial inhibition to aquatic microorganisms up to the limit of water solubility.