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Environmental fate & pathways

Adsorption / desorption

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Description of key information

In accordance with REACH endpoint 9.3.1 and 9.3.3, column 2, adsorption/desorption screening is not required as the substance and its degradation products are readily biodegradable. Furthermore, the substance undergoes rapid hydrolysis (half-life < 1 h at 5 °C) and will thus not be present in the environment. Therefore, the key information is the adsorption coefficient of environmentally relevant hydrolysis products. The Koc of the most relevant identified breakdown product (that with the highest log Pow as a worst case: 3,5,5-trimethylhexanoic acid) was estimated by means of QSAR.

Key value for chemical safety assessment

Koc at 20 °C:
30.38

Additional information

The Koc for bis(3,5,5-trimethylhexanoyl) peroxide was estimated by means of QSAR (KOCWIN v2.00). Experimental determination is not mandatory under REACH because the substance and its relevant degradation products decompose rapidly (rapid hydrolysis and ready biodegradation).

However, for rapidly hydrolysing substances it is more appropriate to also determine the degree of adsorption of the hydrolysis products (see Guidance on information requirements and chemical safety assessment, Chapter R.7a: R.7.1.15.4).

Accordingly, the Koc value selected for the chemical safety assessment is that estimated for 3,5,5-trimethylhexanoic acid, an identified breakdown product formed during the rapid hydrolysis of bis(3,5,5-trimethylhexanoyl) peroxide. 3,5,5-trimethylhexanoic acid is the environmentally relevant compound, since that with the highest octanol-water partitioning coefficient among the two identifiable breakdown products (log Pow = 3.34; QSAR estimate, see IUCLID section 4.7). Therefore, the properties of 3,5,5-trimethylhexanoic acid govern the environmental fate of any residues of bis(3,5,5-trimethylhexanoyl) peroxide that may end up in the environment.

The Koc that was estimated based on MCI is relatively low (30.38 L/kg), indicating no significant soil adsorption of environmentally relevant substance residues.

[LogKoc: 1.4826]