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Toxicity to microorganisms

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Description of key information

EC50 > 100 mg/L for activated sludge (OECD 209)

Key value for chemical safety assessment

Additional information

There are no studies available on microorganism toxicity for 2-ethylhexyl stearate (CAS No. 22047-49-0). The assessment was therefore based on studies conducted with the structurally most similar substances, for which data is available, isopropyl myristate (CAS No. 110-27-0), ethyl linoleate (CAS No. 544-35-4) and isopropyl oleate (CAS No. 112-11-8) as part of a read across approach. This is in accordance with Regulation (EC) No 1907/2006, Annex XI, 1.5. Grouping of substance and read across approach. Further justification is given within the endpoint summary 6.1 and within the category justification section 13. In this case of read-across, the best suited (highest degree of similarity, nearest physico-chemical properties) read-across substances were entered into IUCLID. Nevertheless, as can be seen in the data matrix of the category justification in Section 13, all reliable data in the category support the hazard assessment for this endpoint, by showing a consistent pattern of results.

The key study with isopropyl oleate (CAS No. 112-11-8) was performed as a limit test according to the guideline ISO 10712 (Mead, 1997). A culture of the test organism Pseudomonas putida was exposed to the test substance in a static system for 16 hours, at the nominal concentration of 10000 mg/L. There was no significant difference in growth rate between the control and the 10000 mg/L loading rate. A nominal EC50 > 10,000 mg/L is reported.

The key study with ethyl linoleate (CAS No. 544-35-4) was performed as a limit test according to OECD guideline 209 and GLP (Desmares-Koopmans, 2010). Activated sludge of a predominantly domestic sewage was exposed to ethyl linoleate in a static system for 3 hours, at the loading rate of 100 mg/L. No inhibition of respiration rate of the sludge was recorded, and the EC50 of ethyl linoleate was reported to be > 100 mg/L.

The supporting study with isopropyl myristate (CAS No. 110-27-0) was performed according to a national guideline similar to DIN 38412, part 8 and GLP (Coenen, 1988). A culture of the test organism Pseudomonas putida was exposed to the test substance in a static system for 18 hours, at the nominal test concentrations 0, 0.004, 0.008, 0.016, 0.031, 0.063, 0.125, 0.25, 0.5, 1, 2, 4, 8, 16 mg/L. Since all the measured extinction values were very close to the reference, no real toxicity threshold could be determined. It can, however, be concluded that the substance has no effect on the growth of P. putida up to the concentration of 16 mg/L.

Thus, based on theabove mentioned results, and due to the structural and profile similarities of the substances, as are explained with in the overall endpoint summary 6.1 it can be concluded that the EC50 (nominal) of 2-ethylhexyl stearate (CAS No. 22047-49-0) is > 100 mg/L.