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Environmental fate & pathways

Endpoint summary

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Additional information

Biodegradation in water

Tris(2-ethylhexyl) 2-(acetyloxy)propane-1,2,3-tricarboxylate was tested for its biodegradation potential according to OECD Guideline 301F and EU Method C.4D (Feil, 2010). Aerobic activated sludge, microorganisms from a domestic waste water treatment plant was taken as inoculum. Sodium benzoate was used as reference compound. Also a toxicity control (test item and reference compound mixed) was run in parallel, to ensure, that the chosen test concentration was not inhibitory to microorganisms. The mean biodegradation after 28 days of the test substance was 2%; the 10 day window criterion was not passed and therefore the substance has to be considered as not readily biodegradable. The reference item attained 88 % degradation after 28 days of incubation. The test item can be assumed to be not inhibitory to the aerobic activated sludge microorganisms and all validity criteria of the test method were met. This result is in contrast to the ready biodegradability prediction done with the computer program BIOWIN v4.10 (EPIWIN software) by US-EPA, as according to this ATEHC is suspected to be biodegradable.

Biodegradation in water and sediment

Based on the available data tris(2-ethylhexyl) 2-(acetyloxy)propane-1,2,3-tricarboxylate is considered to be highly insoluble in water. The water solubility for this substance was determined to be lower than 0.05 mg/L [7.804E-07 mg/L (at 25 °C) by QSAR estimation (EPIWIN/WSKOWWIN v1.42 by US-EPA); < 0.05 mg/L at 20 °C and pH 7 in an experimental test]. Hence, it may be practically difficult or impossible to conduct the test at concentrations below the water solubility of the substance. According to the Safety Assessment it is also unlikely that the surface water environment will be the principal environment of concern.

Although the substance shows a high to very high sorption potential onto soil organic matter based on the available LogKoc [LogKoc = 7.96 by QSAR estimation (EPIWIN/KOCWIN v2.00 by US-EPA); LogKoc= 4.271 (Read-across data from ATBC)], simulation testing on ultimate degradation in sediment, information requirement 9.2.1.4 in Annex IX, does also not need to be conducted, as it has been shown in soil biodegradation tests with the structural analogue acetyl tributyl citrate (CAS 77-90-7; ATBC) that the test substance is readily biodegradable.

The hazard assessment of the substance reveals neither a need to classify the substance as dangerous to the environment, nor is it a PBT or vPvB substance, nor are there any further indications that the substance may be hazardous to the environment. Therefore, a simulation test on biodegradation in surface water and sediment is scientifically not justified.

Biodegradation in soil

No experimental results are available for tris(2-ethylhexyl) 2-(acetyloxy)propane-1,2,3-tricarboxylate regarding its biodegradation behaviour in soil. For this purpose a read-across approach to the structural analogue tributyl-O-acetylcitrate (CAS 77-90-7) was intended (please refer to the separate read-across statement for further details). Three experimental results are available. In a test on biodegradation in soil according to EPA OPPTS 835.3300 tributyl-O-acetylcitrate (CAS 77-90-7) was found to be readily biodegradable (Farrell, 2000). The same was concluded out of a Respirometry test in ‘static’ compost biometer system (Farrell, 2000). Microbial degradation of the test substance in the compost was, in part, retarded at the very high substrate loading used in another experiment (Farrell, 2000). Despite randomisation in bioreactor placement, the reduced air supply due to NaOH crystal formation in the air distribution manifold became more significant along the manifold and throughout the exposure period, potentially influencing the results achieved during this study. It can be assumed that the same applies to tris(2-ethylhexyl) 2-(acetyloxy)propane-1,2,3-tricarboxylate (CAS 144 -15 -0) as it is a near analogue to the test substance acetyl tributyl citrate.