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Environmental fate & pathways

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Screening tests for environmental fate and pathways were conducted for tris(2-ethylhexyl) 2-(acetyloxy)propane-1,2,3-tricarboxylate. An experimental result is available for biodegradation in water (Feil, 2010), concluding that the substance is not readily biodegradable - contrary to a calculated ready biodegradation prediction with the help of the QSAR software BIOWIN v4.10 (by US-EPA), where the substance was found to be biodegradable. Simulation testing has not to be conducted since the substance was found to be insoluble in water (Frischmann, 2011), which is in accordance with REACH, Annex IX, Section 9.2.1.2, Column 2. A read-across approach to acetyl tributyl citrate regarding its biodegradation behaviour as well as the adsorption potential in soil is intended (please refer to the separate read-across statement for further details). The substance was investigated for mineralisation processes in soil and compost, whereby it can be considered as readily biodegradable in these substrates. Therefore, simulation testing on ultimate degradation in sediment, information requirement 9.2.1.4 in Annex IX, has also no need to be conducted.

The adsorption potential to soil / sewage sludge of the read-across substance was experimentally investigated according to OECD Guideline 121 and EU Method C.19, whereby a logKoc of 4.271 was determined. Furthermore, a QSAR prediction was performed for tris(2-ethylhexyl) 2-(acetyloxy)propane-1,2,3-tricarboxylate regarding soil adsorption potential, using the US-EPA software KOCWIN v2.00. Two different methods: the Sabljic molecular connectivity (MCI) method, resulting in a value of 9204000 L/kg and the traditional method, giving a Koc value of 2009000 L/kg. For the chemical safety assessment, the result of the MCI method is taken into account. These values reinforce the indicated very strong binding potential of the test substance to soil particles.

Also the bioconcentration factor (BCF) can be predicted with the help of the QSAR software BCFBAF v3.01 (by US-EPA). The regression-based estimate (traditional method) resulted in a BCF of 120 L/kg wet-wt and also the Arnot-Gobas method (based on mechanistic first principles) resulted in a low BCF of 0.90 L/kg wet-wt. The substance specific LogPow (9.96, Frischmann, 2011) is taken into account for these predictions. Based on these calculated results, a low potential for bioconcentration is to be expected (< 500 L/kg). Further, some more factors have been taken into account: In general, absorption of a chemical is possible, if the substance crosses biological membranes. This process requires a substance to be soluble, both in lipid and in water and is also dependent on its molecular weight (substances with molecular weights below 500 are favourable for absorption). In conclusion tris(2-ethylhexyl) 2-(acetyloxy)propane-1,2,3-tricarboxylate is expected to be poorly absorbed, considering its molecular weight and water solubility.

Another QSAR prediction was performed for tris(2-ethylhexyl) 2-(acetyloxy)propane-1,2,3-tricarboxylate regarding phototransformation in air, resulting in an overall gas-phase reaction constant of 33.47 E-12 cm³/molecules-sec (= 2.89 m³/molecules-day), with an half-life of 0.32 d (3.83 h) by assuming a 12 h day with an OH rate constant of 1.5E6 OH/cm³ and 25°C, thus it can be concluded that the substance will be rapidly degraded in air.

The Henry's Law Constant was calculated with the US-EPA computer program HENRYWIN (v3.20) to be 1.15E-003 Pa*m3*mol-1 at 25°C.

The hydrolytic behaviour of tris(2-ethylhexyl) 2-(acetyloxy)propane-1,2,3-tricarboxylate has not be investigated since the substance was found to be insoluble in water (< 0.05 mg/L at 20 °C and pH 7, Frischmann, 2011) and therefore, a hydrolysis study has not to be conducted in accordance with REACH, Annex VIII, Section 9.2.2.1, Column 2.

No monitoring data or field study results are available for tris(2-ethylhexyl) 2-(acetyloxy)propane-1,2,3-tricarboxylate. These types of experiments are also not mandatory under REACH.