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Toxicity to microorganisms

Description of key information

NOEC ≥ 29.6 mg/L (OECD 301B, activated sludge)
EC50 (3 h) > 1000 mg/L (OECD 209, activated sludge)
EC10 (16 h) > 50 mg/L (ISO 10712, Pseudomonas putida)

Additional information

One study for the substance itself and two read across studies investigating the toxicity of fatty acids C5-10 esters with dipentaerythritol (CAS 70983-72-1) to activated sludge microorganisms are available. For fatty acids C5-10 esters with dipentaerythritol (CAS 70983-72-1) 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 fatty acids C5-10 esters with dipentaerythritol acid a biodegradation test according to OECD 301B is available (Muckle, 2012). The toxicity control, containing 25 mg/L inoculum, 29.6 mg/L of the test substance and 26 mg/L of the reference material aniline attained 48% 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 29.6 mg/L can be used to derive the NOEC (14 d) of ≥ 29.6 mg/L.

Additionally, in accordance to Regulation (EC) No 1907/2006 Annex XI, 1.5 a read across to the structurally similar analogue substance dipentaerythritol with fatty acids, C5 and C9iso (CAS 647028-25-9) and isononanoic acid, mixed esters with dipentaerythritol, heptanoic acid and pentaerythritol (CAS 84418-63-3) was conducted. This read-across is justified in detail in the overall summary (IUCLID chapter 6.1) and within the analogue justification in IUCLID Section 13.

Both substances consist of the same alcohol component (dipentaerythritol) and similar fatty acid chain lengths (C5-9 for the target substance compared to C9iso and C5-9iso for the source substances, respectively).

The first study investigated the toxicity of dipentaerythritol with fatty acids, C5 and C9iso to microorganisms. The test was performed according to OECD 209 (Mead, 1999) with activated sludge of a predominately domestic sewage treatment plant under GLP conditions. Mircoorganisms were exposed to a limit concentration of 1000 mg/L for 3 h. No effects on the respiration rate of the activated sludge microorganism population were observed. Therefore, this study resulted in an EC50 (3 h) of > 1000 mg/L and a NOEC (3 h) of ≥ 1000 mg/L. An additional study investigated the toxicity of isononanoic acid, mixed esters with dipentaerythritol, heptanoic acid and pentaerythritol) to aquatic microorganisms. The GLP study was conducted similarly to ISO 10712 investigating the growth of Pseudomonas putida (Comber, 1993). A Water Accommodated Fraction (WAF) of a loading of 50 mg/L was used for the test. No inhibitory effect was observed after 6 h. Hence the EL10 was determined to be > 50 mg/L (nominal) based on growth inhibition.

Based on the results for 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 fatty acids C5-10 esters with dipentaerythritol will not exhibit microbial inhibition to aquatic microorganisms up to the limit of water solubility.