Fatty acids, C8-10, C8-10-alkyl esters

Toxicity to microorganisms

Description of key information

EC10 (3 h): > 1000 mg/L (OECD 209)

Additional information

Since no studies investigating the toxicity of Fatty acids, C8-10, C8-10 alkyl esters (CAS 129677-93-6) to activated sludge microorganisms are available, in accordance to Regulation (EC) No 1907/2006 Annex XI, 1.5 a read-across to the structurally related source substances Fatty acids, C8-10, C12-18-alkyl esters (CAS 95912-86-0) and octyl octanoate (CAS 2306-88-9) was conducted. The source substances are representative to evaluate the toxicity of the target substance to activated sludge microorganisms. The target substance is characterized as an ester of C8-C10 fatty acid and C8-C10 alcohol. The source substances are structurally very similar to the target substance. Fatty acids, C8-10, C12-18-alkyl esters (CAS 95912-86-0) is a UVCB substance of mainly C8-C10 fatty acid esterified with mainly C12-C14 alcohol. Octyl octanoate (CAS 2306-88-9) is a mono-constituent substance of C8 fatty acid esterified with C8 alcohol. Comparing both substances they only differ slightly in C-chain lengths distribution. None of the selected source substances has a structural alert for an increased toxicity via a specific mode of action. This read-across is justified in detail in the overall summary (IUCLID Section 6.1) and within the analogue justification in IUCLID Section 13. In this case of read-across, the best suited (highest degree of structural similarity, nearest physico-chemical properties) read-across substance was used for the assessment.
The study with the read-across substance Fatty acids, C8 - 10, C12 - 18-alkyl esters (CAS 95912-86-0) was performed according to OECD 209 under GLP conditions (Hammer, 2013). Activated sludge microorganisms were exposed to the test substance up to a nominal concentration of 1000 mg/L. No effects were observed based on the respiration rate after 3 h of incubation resulting in an EC10 (3 h) of > 1000 mg/L. An increase of respiration was recorded in all treatments compared to the control values.

The second study with the read-across substance octyl octanoate (CAS 2306-88-9) was performed according to OECD Guideline 209 (Hammer, 2013). Activated sludge was exposed to the test substance in a static system for 3 h, at nominal concentrations of 1000, 500, 250, 125 and 62.5 mg/L. No toxicity was observed at any of the concentrations tested, and the EC10 (3 h) was determined to be > 1000 mg/L.

Based on the available results from a structurally related read-across substance (in accordance to Regulation (EC) No 1907/2006 Annex XI, 1.5) which is characterized by a similar ecotoxicological profile and comparable structure, it can be concluded that Fatty acids, C8-10, C8-10 alkyl esters will not exhibit effects on activated sludge microorganisms and does not inhibit the microbiological process of degradation in sewage treatment plants.