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Toxicity to microorganisms

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Description of key information

EC10 (3 h): > 1000 mg/L for activated sludge microorganisms (OECD 209)

Key value for chemical safety assessment

Additional information

Since no studies investigating the toxicity of Tetraesters of pentaerythritol with 2-ethylhexanoic acid, heptanoic acid and nonanoic acid (EC 806-879-4) to activated sludge microorganisms are available, in accordance to Regulation (EC) No 1907/2006 Annex XI, 1.5 a read-across to the structurally related source substance Decanoic acid, mixed esters with heptanoic acid, octanoic acid, pentaerythritol and valeric acid (CAS 71010-76-9) was conducted.

The source substance is representative to evaluate the toxicity of Tetraesters of pentaerythritol with 2-ethylhexanoic acid, heptanoic acid and nonanoic acid (EC 806-879-4) to activated sludge microorganisms. The target substance is characterized as a tetraester of pentaerythritol and different fatty acids (C7, C9 and 2-ethylhexanoic acid). Decanoic acid, mixed esters with heptanoic acid, octanoic acid, pentaerythritol and valeric acid (CAS 71010-76-9) is a tetraester of C5/C7/C9/C10 with pentaerythritol. All substances share similar physico-chemical properties, only differ in the distribution of chain lengths of the fatty acid and do not share any functional group which might increase aquatic toxicity the read-across is suitable to investigate the aquatic toxicity using read-across. This read-across is justified in detail in the overall summary (IUCLID Section 6.1) and within the analogue justification in IUCLID Section 13. In this case of read-across, the best suited (highest degree of structural similarity, nearest physico-chemical properties) read-across substances were used for the assessment.

The study with the source substance decanoic acid, mixed esters with heptanoic acid, octanoic acid, pentaerythritol and valeric acid (CAS 71010-76-9) to activated sludge microorganisms was conducted according to OECD 209 (GLP; Dickinson, 2008). Non-adapted activated sludge obtained from a domestic sewage treatment plant was used as inoculum. Test concentrations of 10, 100 and 1000 mg/L were applied and added directly to the test vessels. The test substance did not inhibit the respiration rate of activated sludge microorganisms at any of the concentrations employed in the test. Hence, the EC50 (3 h) was determined to be > 1000 mg/L based on the nominal test concentration. Therefore, it can be concluded that the test substance will not exhibit effects on the respiration rate of microorganisms. As it can be seen in the data matrix of the category justification in section 13 and the overall summary, all reliable data in the category support the hazard assessment of each category member by showing a consistent pattern of results, i.e. no microbial inhibition.

Based on the available result from one structurally related source substance (in accordance to Regulation (EC) No 1907/2006 Annex XI, 1.5) which is characterized by a similar ecotoxicological profile and comparable structure, it can be concluded that Tetraesters of pentaerythritol with 2-ethylhexanoic acid, heptanoic acid and nonanoic acid (EC 806-879-4) will not exhibit effects to activated sludge microorganisms and will not inhibit the degradation in sewage treatment plants.

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