Fatty acids, tall-oil, esters with trimethylolpropane

Biodegradation in water: screening tests

Description of key information

Readily biodegradable: 60 - 91% after 28 d (OECD 301B and OECD301F)

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Additional information

Since no studies investigating the ready biodegradability of fatty acids, tall-oil, triesters with trimethylolpropane (CAS 94581-09-6) are available for this endpoint, in accordance to Regulation (EC) No 1907/2006 Annex XI, 1.5 a read across to the structurally related source substances Fatty acids, C16-18 and C18 unsatd., triesters with trimethylolpropane (CAS 68002-78-8), Fatty acids, C16-18 (even numbered) and C16-18-unsatd. (even numbered), triesters with trimethylolpropane (CAS 68002-79-9), 2-ethyl-2-(((1-oxoisooctadecyl)oxy)methyl)-1,3-propanediyl bis(isooctadecanoate) (CAS 68541-50-4) and fatty acids, C16-18 and C18-unsatd., branched and linear ester with trimethylolpropane (CAS 403507-18-6) was conducted. 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 first study with the read-across substance fatty acids, C16-18 and C18-unsatd., triesters with trimethylolpropane (CAS 68002-78-8) was conducted according to OECD guideline 301B (Bouillon, 2012). The substance was incubated under aerobic conditions with domestic activated sludge for 28 days. Based on the CO2 production of the inoculum a degradation rate of 86.6% was determined at test termination. Therefore, the test substance is readily biodegradable according to the OECD criteria.

The second study with the read-across substance fatty acids, C16-18 (even numbered) and C16-18-unsatd. (even numbered), triesters with trimethylolpropane (CAS 68002-79-9) was performed according to OECD 301F (Börner, 2000). Effluent from a municipal sewage treatment plant was used as inoculum. After 28 d a degradation of 86% was observed and the 10-day window was fulfilled. In conclusion, the test substance is readily biodegradable according to OECD criteria.

The third study with the read-across substance 2-ethyl-2-(((1-oxoisooctadecyl)oxy)methyl)-1,3-propanediyl bis(isooctadecanoate) (CAS 68541-50-4) followed OECD 301B using domestic activated sludge as inoculum (Oggier, 2011). The degradation rate was determined by measuring the CO2 evolution of the inoculum. After 28 days of incubation a degradation rate of 91% was determined. Thus the substance is regarded as readily biodegradable according to OECD criteria.

The fourth study with the read-across substance fatty acids, C16-18 and C18-unsatd., branched and linear ester with trimethylolpropane (CAS 403507-18-6) was conducted according to OECD 301B under GLP conditions (Clarke, 2002). Activated sludge from the aeration stage of a domestic sewage treatment plant was used for the study. The test substance was degraded to 58% after 28 d (CO2 evolution). To drive off any inorganic carbon, hydrochloric acid was added and the CO2 produced was measured on day 29 resulting in 60% degradation. Since fatty acids, C16-18 and C18-unsatd., branched and linear ester with trimethylolpropane is a UVCB substance and consists of structurally similar constituents with [e. g. different chain-lengths, degree and/or site of branching or stereo-isomers], sequential (instead of concurrent) biodegradation of the individual structures can take place, but all can be considered as readily biodegradable. Thus, referring to Annex I to the OECD Guideline for Testing of Chemicals ‘Revised introduction to the OECD guidelines for testing of chemicals, section 3’ (OECD, March 2006), the 10-day window should not be considered for this UVCB substance and due to a degradation of 60% within 28 days the substance can be regarded as readily biodegradable according to the OECD criteria.

Thus, based on the available studies from structurally related read-across substances (in accordance to Regulation (EC) No 1907/2006 Annex XI, 1.5) which are characterized by an equal ecotoxicological profile and a similar structure, it can be concluded that fatty acids, tall-oil, triesters with trimethylolpropane is readily biodegradable according to the OECD criteria.