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Toxicity to microorganisms

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Description of key information

No toxicity up to the limit of water solubility (WS < 0.05 mg/L) is expected

Key value for chemical safety assessment

Additional information

No data investigating the toxicity to microorganisms are available for docosanoic acid, ester with 1,2,3-propanetriol (CAS No. 77538-19-3).According to Regulation (EC) No. 1907/2006, Annex VIII, Column 2, 9.1.4, testing on aquatic microorganisms is not required if there are mitigating factors indicating that microbial toxicity is unlikely to occur, for example due to high insolubility of the substance in water. Docosanoic acid, ester with 1,2,3-propanetriol is insoluble in water (water solubility < 0.05 mg/L) and therefore limited exposure to activated sludge microorganisms is expected for this substance.

The Guidance on information requirements and chemical safety assessment, Chapter R7.b (ECHA, 2008) states that once insoluble chemicals enter a standard STP, they will be extensively removed in the primary settling tank and fat trap and thus, only limited amounts will get in contact with activated sludge organisms. Furthermore,docosanoic acid, ester with 1,2,3-propanetriol is readily biodegradable. According to the above mentioned guidance, for substances with a good biodegradation rate in a ready biodegradability test, inhibitory effects to aquatic microorganisms are not expected and the concentration tested can be used as a NOEC.

Additionally, a study conducted with Pseudomonas putida is available for the analogue category member1,2,3-propanetriyl trioleate(CAS No. 122-32-7).Both read-across and target substances are UVCB substances, formed from the esterification of fatty acids and glycerol, containing long-chain fatty acids (C14-18 and 18 unsaturated for CAS No. 122-32-7 and C16 to C22 for CAS No. 77538-19-3). Furthermore, their water solubilities are comparable (< 0.05 mg/L for both). Therefore, these two substances are expected to show similar behaviour in the water phase and comparable degrees of toxicity to aquatic organisms. Thus, the read-across in accordance with Regulation (EC) No. 1907/2006, Annex XI, 1.5, is justified.

 

The test conducted on 1,2,3-propanetriyl trioleate was performed according to the German method “Assessment of hazardous substances in water, Determination of the acute toxicity in Bacteria”, under GLP conditions. Pseudomonas putida cultures were exposed to the test substance for 18 hours in a static water regime at 25°C and effects on cell proliferation were assessed (as the extinction of the monochromatic radiation at 436 nm in a 10 mm layer). After the exposure period, no inhibitory effects on cell multiplication could be observed up to the highest concentration tested and therefore, the EC50 (18 h) was determined to be > 0.8 mg/L (nominal concentration).

 

Based on the results of the test conducted with the structurally related category member (in accordance with Regulation (EC) No. 1907/2006, Annex XI, 1.5), the ready biodegradability and poor solubility of docosanoic acid, ester with 1,2,3-propanetriol in water, this substance is not expected to show toxicity to aquatic microorganisms up to the limit of its water solubility (< 0.05 mg/L).

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