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Ecotoxicological information

Toxicity to microorganisms

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Description of key information

NOEC (3h) ≥ 100 mg/L (OECD 209, activated sludge); read-across

Key value for chemical safety assessment

Additional information

No studies are available on the toxicity of Sorbitan tristearate (CAS No. 26658 -19 -5) to microorganisms. The assessment was, therefore, based on studies conducted with the structurally similar category members Sorbitan monoisooctadecanoate (CAS No. 71902-01-7), Sorbitan laurate (CAS No. 1338-39-2) and Sorbitan, octanoate (2:3) (CAS No. 91844-53-0) as part of a read-across approach, which 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.

The key study conducted with Sorbitan laurate (CAS No. 1338-39-2) was performed as a limit test according to the OECD Guideline 209 and GLP (Desmares-Koopmans, 2010). Activated sludge of a predominantly domestic sewage was exposed to the test concentration of 100 mg/L during 3 hours. No effect on the respiration rate of the activated sludge was observed.

The toxicity of Sorbitan, isooctadecanoate (CAS No. 71902-01-7) and Sorbitan, octanoate (2:3) (CAS No. 91844-53-0) to microorganisms was tested in toxicity controls during ready biodegradation studies (OECD 301 B and OECD 301 F, respectively). If a compound degrades well in a ready biodegradability test, or does not inhibit the degradation of a positive control at a certain concentration, this concentration can be used as a NOEC value. This approach is in accordance with the Guidance on information requirements and chemical safety assessment (Chapter R.7b: Endpoint specific guidance, ECHA 2012). A substance can be assumed to be not inhibitory to aquatic microorganisms, if in the toxicity control of a ready biodegradation test, more than 25% degradation based on CO2 evolution (CO2/ThCO2) occurred within 14 days (OECD guideline 301).

For Sorbitan, isooctadecanoate a biodegradation test according to OECD guideline 301 B is available (Clarke, 2012). The test includes a toxicity control, which contains 14.4 mg/L of Sorbitan, isooctadecanoate and 17.1 mg/L of the reference material sodium benzoate. The toxicity control attained 82% 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 14.4 mg/L can be used as NOEC.

For Sorbitan, octanoate (2:3) a biodegradation test according to OECD guideline 301 F is available (Ley, 2005). The test includes a toxicity control, which contains 100 mg/L of Sorbitan, octanoate (2:3) and 100 mg/L of the reference material sodium benzoate. The toxicity control attained 73% 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 100 mg/L can be used as NOEC.