Fatty acids, C12-16 (even numbered) and C18 unsatd., Me esters

Toxicity to microorganisms

Description of key information

NOEC (3 h) ≥  1000 mg/L (nominal) for activated sludge (OECD 209, read across)

Additional information

No data investigating the toxicity to microorganisms are available for Fatty acids, C12-16 (even numbered) and C18-unsatd., methyl esters (CAS No. 1234694-02-0).

 

Therefore, data from a structurally related category member, methyl laurate (CAS No. 111-82-0) are used as read-across (in accordance with Regulation (EC) No. 1907/2006, Annex XI, 1.5). Both substances are fatty acids esterified with methanol, containing C12 (methyl laurate) and C12-16 and C18 unsaturated (target substance) fatty acids. Despite the fact that the water solubility value of methyl laurate is not comparable (7.7 mg/L) to that of Fatty acids, C12-16 (even numbered) and C18-unsatd., methyl esters (< 1 mg/L), the target substance has a high content of C12 fatty acids (40-50%). Furthermore, methyl laurate (C12 FA content > 80%) exhibits the highest toxicity to aquatic organisms (Daphnia and algae) throughout the whole SCAE Me category, with EC50 and NOEC values < 1 mg/L.Therefore, methyl laurate is used as worst-case read-across substance in accordance with Regulation (EC) No. 1907/2006, Annex XI, 1.5.

 

The study evaluating the toxicity of methyl laurate to aquatic microorganisms (Fiebig, 2013) was conducted according to OECD Guideline 209, under GLP conditions. Activated sludge microorganisms from a municipal sewage treatment plant were exposed to the test substance for 3 hours at a concentration of 1000 mg/L (limit test). After the exposure period, no inhibiting effects of the substance on microorganisms activity were reported, leading to a NOEC (3 h) ≥ 1000 mg/L (nominal concentration).

 

In addition, Fatty acids, C12-16 (even numbered) and C18-unsatd., methyl esters is poorly soluble (< 1 mg/L), which limits the exposure of activated sludge microorganisms in sewage treatment plants significantly. 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, Fatty acids, C12-16 (even numbered) and C18-unsatd., methyl esters is considered to be readily biodegradable (78%, 90% and 75% in 28 days). According to Chapter R7.b of the Guidance on information requirements and chemical safety assessment (ECHA, 2008), for substances with a good biodegradation rate in a ready biodegradation test, inhibitory effects to aquatic microorganisms are not expected and the concentration tested can potentially be used as a NOEC for hazard assessment.

 

The lack of toxicity observed for methyl laurate (showing the highest aquatic toxicity within the category) confirms that the members of the SCAE Me category are not expected to show toxicity to aquatic microorganisms. This statement is supported by the readily biodegradable nature of these substances.

 

Based on the ready biodegradability of the substance and the results of the respiration inhibition test conducted with a structurally related category member (in accordance with Regulation (EC) No. 1907/2006, Annex XI, 1.5), no toxicity to aquatic microorganisms is expected for Fatty acids, C12-16 (even numbered) and C18-unsatd., methyl esters (CAS No. 1234694-02-0).