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Environmental fate & pathways

Bioaccumulation: aquatic / sediment

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Description of key information

The BCF was calculated to be 120 L/kg (regression-based estimate) and 0.899 L/kg (Arnot-Gobas method), respectively. [with BCFBAF v3.01 (EPIWIN software by US-EPA)]

Key value for chemical safety assessment

BCF (aquatic species):
120 L/kg ww

Additional information

The prediction for the bioconcentration factor (BCF) of the substance tris(2 -ethylhexyl) 2-(acetyloxy)propane-1,2,3-tricarboxylate was done by the computer program BCFBAF v3.01 (EPIWIN software) by US-EPA. Furthermore, the whole body primary biotransformation rate estimation for fish was calculated with the notation that the bio half-life normalised to 10 g fish at 15 °C. It is possible to predict the apparent metabolism half-life in fish for three different trophic levels (lower, mid and upper). Using the regression-based estimate (traditional method) a BCF of 120 L/kg wet-wt (LogBCF = 2.08) was calculated for tris(2 -ethylhexyl) 2-(acetyloxy)propane-1,2,3-tricarboxylate (ATEHC). Using the Arnot-Gobas method, which is based on mechanistic first principles, an aquatic BCF of 0.899 L/kg wet- wt (upper trophic; LogBCF = -0.05) is the result. Both values have been calculated based on an estimated LogPOW of 9.96. Further, the whole body primary biotransformation rate estimate for fish results in a half-life of 0.0237 days, whereby the bio half-life is normalised to 10 g fish at 15 °C. The rate constant (kM) for 10 g fish is 25/day, whereby the predicted value exceeds theoretical whole body maximum value. This is taken into account to predict the apparent metabolism half-life in fish of the test substance. With the Arnot-Gobas method it is possible to differentiate between three trophic levels. For the lower trophic level the BCF results in 0.949 L/kg wet-wt, for a mid trophic level the result is 0.94 L/kg wet-wt and for the higher trophic level 0.899 L/kg wet-wt. Based on these calculated results, a low potential for bioconcentration is to be expected (according to CLP Regulation 1272/2008 substances with a BCF ≥ 500 have a potential for bioconcentration in aquatic organisms). 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). With a molecular weight of 570.8 g/mol the potential to cross biological membranes is very low for tris(2-ethylhexyl) 2-(acetyloxy)propane-1,2,3-tricarboxylate. The water solubility of the substance is very low [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 pH7 in an experimental test], which also implies that absorption is presumed to be hindered. 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.