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Environmental fate & pathways

Adsorption / desorption

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In Article 13 of Regulation (EC) No 1907/2006, it is laid down that information on intrinsic properties of substances may be generated by means other than tests, provided that the conditions set out in Annex XI (of the same Regulation) are met. Furthermore according to Article 25 of the same Regulation testing on vertebrate animals shall be undertaken only as a last resort.

According to Annex XI of Regulation (EC) No 1907/2006 (Q)SAR results can be used if (1) the scientific validity of the (Q)SAR model has been established, (2) the substance falls within the applicability domain of the (Q)SAR model, (3) the results are adequate for the purpose of classification and labeling and/or risk assessment and (4) adequate and reliable documentation of the applied method is provided.

For the assessment of the bulk form (Q)SAR results were used for adsorption. The criteria listed in Annex XI of Regulation (EC) No 1907/2006 are considered to be adequately fulfilled and therefore the endpoint(s) sufficiently covered and suitable for risk assessment.

Therefore, further experimental studies on adsorption are not provided.

The log Koc was determined to be 4.25 (MCI method) and 3.84 (logkow method) using SRC PCKOCWIN (BASF SE, 2022). However, the present compound exhibits a conjugated system with a core structure of completely delocalized electrons. A delocalized electron system results in thermodynamically very stable molecules which at least partially prevents the interaction with neighboring surfaces. Due to the limited interaction caused by the lack of functional groups and the high stability of the substance, significant adsorption/desorption is not expected.  

Furthermore, a heteroagglomeration/aggregation with other particles with same material or other particle, e.g. organic matter, or to the interface between phases is very unlikely due to the very low water solubility and non-occurrence of functional groups of the molecule. Thus, sorption of the substance to soil particles is very unlikely.

In Regulation (EC) No 2018/1881 which amends Regulation (EC) No 1907/2006 it is stated, that data about dispersion stability may significantly influence the endpoint adsorption and estimations of exposure to nanoforms.  In this case an OECD 318 study concerning dispersion stability resulted in a quick agglomeration and sedimentation of the substance, meaning homoagglomeration. Thus, stability of discrete particles in the nano size scale in the water phase is unlikely. Since the results of the dispersion stability study of the bulk form are very similar compared to the nano form, this statement is true for both the bulk and the nanoform. Hence, existence of the test substance in environmental systems is unlikely and due to agglomeration, an adsorption effect based on its properties can be excluded.

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