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Environmental fate & pathways

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Experimentally derived values on hydrolysis and photooxidation of L-threonine mother liquor are not available. In Annex VIII of Regulation (EC) No 1907/2006, it is laid down that further degradation testing shall be considered if the chemical safety assessment according to Annex I indicates the need to investigate further the degradation of the substance. According to reliable study results, Biofert Plusz (mixture of L-threonine mother liquor and modified waste) is considered to be rapidly biodegraded in the environment and the bioaccumulation potential is regarded to be insignificant. Based on the composition of Biofert Plusz this statement applies likewise to the test material under investigation (L-threonine mother liquor).Therefore, the performance of experimental studies on hydrolysis or photodegradation are assumed to be scientifically not justified.

No data are available on the biodegradation of L-threonine mother liquor. Based on the composition of Biofert Plusz (mixture of approximately equal amounts of L-threonine mother liquor and modified waste) and taking into account that modified waste (mortified microbiological material) itself is not subject to biodegradation it can be assumed that the results obtained with Biofert Plusz apply likewise to the test material under investigation (L-threonine mother liquor).

The ready biodegradability of Biofert Plusz was investigated in a study conducted according to OECD Guideline 301 B over a period of 28 days and using non-adapted activated sludge as inoculum source. The biodegradation rate was determined by measurement of CO2 evolution. Inoculum blank, procedural/functional control with the reference substance sodium benzoate, and toxicity control using 80 mg/L test material and 20 mg/L reference compound were performed. Biofert Plusz proved to be readily biodegradable and fulfilling the 10-d window criterion (92% biodegradation after 28 d). The functional control reached the pass level >60% after 14 d. In the toxicity control containing both test and reference substance 81% biodegradation based on ThCO2 occurred within 14 d thus indicating that the test item was not inhibitory at the concentration tested.

For the bioaccumulation of L-threonine mother liquor no experimental studies are available. L-Threonine mother liquor is a complex mixture containing organic and inorganic components (UVCB-substance). L-Threonine is the main component of L-threonine mother liquor. For the bioaccumulation of L-threonine - the main component of L-threonine mother liquor - no experimental studies are available. Therefore the bioaccumulation factor of L-threonine was calculated via EPIWIN v4.0, BCFBAF v3.00. The calculation yielded a BCF of 3.162 L/kg ww.

Experimental studies on adsorption/desorption of L-threonine mother liquor are not available.

According to REACH Regulation (Annex VIII, 9.3.1, column II), the study on adsorption/desorption does not need to be done if the the test material is readily biodegradable. Biofert Plusz (mixture of L-threonine mother liquor and modified waste) proved to be readily biodegradable. Based on the composition of Biofert Plusz this statement applies likewise to the test material under investigation (L-threonine mother liquor).

L-Threonine mother liquor is a complex mixture containing organic and inorganic components (UVCB-substance). Based on the log Kow of the lead component L-threonine of the test substance (-2.94; Hansch, 1995) the sorption onto sediment organic matter is expected to be negligible.

No data are available for L-threonine mother liquor in respect to Henry's Law constant. Henry's Law constant of threonine as the main constituent of L-threonine mother liquor was calculated using EPIWIN (v4.0), HENRYWIN (v3.20). The calculation of Henry's Law constant according to the equation H=vp/ws yielded a value of 7.34E-009 Pax m3/mole using an estimated water solubility of 2.79e+005 mg/l and a vapour pressure of 7.88E-009 mm Hg. Based on the result, threonine can be considered as practically non-volatile from aqueous solution.