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Toxicity to microorganisms

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Description of key information

No toxicological effects on microorganisms are expected up to the water solubility limit (<0.41 mg/L).

Key value for chemical safety assessment

Additional information

One study investigating the biodegradation of Fatty acids, C16-18 and C18-unsaturated, dimerized (CAS No 71808-39-4) was tested in an in a CO2 evolution test according to OECD guideline 301B using domestic activated sludge as inoculum. This test also consisted of a toxicity control. The toxicity control reolicates each contained 1911 mL of mineral medium, 20 mL of microbial inoculum, the appropriate weight of test item and 69 mL reference material stock (sodium benzoate). This corresponds to 20 mg DOC/L for the test item and 20 mg DOC/L for sodium benzoate. Thus, the absolute amount of DOC in the toxicity control vessels with 2 L capacity amounts to 80 mg DOC/L. With 3.67 being the conversion factor (44/12) for carbon to carbon dioxide, the % degradation can be calculated with the following formula: % degradation = (mg CO2 produced) x 100/(mg TOC added x 3.67). Thus, the toxicity control attained 38.9 % degradation after 28 days of incubation and can be assumed to be non-inhibitory.

This result is supported by two studies, investigating the toxicity to microorganisms of Fatty acids, C18-unsaturated, dimers (CAS No. 61788-89-4) and Fatty acids, C16-18 and C18-unsaturated, branched and linear (CAS-No. 68955-98-6), which were used as read across to Fatty acids, C16-18 and C18-unsaturated, dimerised (CAS No 71808-39-4), “Crude dimer” in accordance with Regulation (EC) No. 1907/2006, Annex XI, 1.5. grouping of substance and read across approach. Tests of these structurally related category members are considered to be representatble as they are two of the main components of the crude dimer.

The growth inhibition of Pseudomonas putida was recorded in a GLP study according to ISO 10712 for Fatty acids, C18 -unsaturated, dimers (CAS No. 61788-89-4) (Sewell, 1997). No effects on the growth of P. putida at the tested WAF loading rates after 16 hours were observed (EL10/EL50 > 10000 mg/L, NOELR ≥ 10000 mg/L. Thus one can conclude that there were no effects up to 10000 mg/L (nominal). Similarly a study report with the test substance Fatty acids, C16 -18 and C18-unsaturated, branched and linear (CAS No. 68955-98-6) (Mead, 1997) indicated that there was no toxicity of the test substance to microorganisms resulting from a cell multiplication inhibition test with Pseudomonas putida according to ISO 10712 (NOELR ≥ 10000 mg/L). In both cases, due to the low water solubility of the test substance, the test solutions were prepared as water accommodated fractions (WAF).

Thus, it is assumed that due to structural similarities of the tested category members and the results of the toxicity control indicating no microbial inhibition, no toxicological effects on microorganisms are expected up to 10000 mg/L for Fatty acids, C16-18 and C18-unsaturated, dimerized (CAS No. 71808-39-4).

 

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