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Environmental fate & pathways

Biodegradation in water and sediment: simulation tests

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Description of key information

Under the conditions on the test performed according to OECD guideline 309 and GLP requirements, neither 3-hydroxy-1,1-dimethylbutyl 2-ethyl-2-methylheptaneperoxoaten or its degradation products are likely to persist in natutal aerobic water systems.

Key value for chemical safety assessment

Half-life in freshwater:
0.6 d
at the temperature of:
20 °C

Additional information

A study according to OECD guideline 309 and GLP requirements has been performed in order to determine the extent of mineralisation of 3-hydroxy-1,1-dimethylbutyl 2-ethyl-2-methylheptaneperoxoate in a natural surface water at 20 ± 2°C and to determine its route and rate of degradation under the test conditions (Lewis, 2016).

Two radiolabelled forms of 3-hydroxy-1,1-dimethylbutyl 2-ethyl-2-methylheptaneperoxoate have been used in the study: [hexylene glycol-4 - 14C]3-hydroxy-1,1-dimethylbutyl 2-ethyl-2-methylheptaneperoxoate and [2 -14C-methylheptanoate] 3-hydroxy-1,1-dimethylbutyl 2-ethyl-2-methylheptaneperoxoate.

Two test concentrations were used for each radiolabel (10 and 95 µg/L). Sodium [14C] benzoate was used as a reference substance.

Under these conditions, the test substance mineralised rapidly; mineralisation rates were very similar for each concentration and were also similar between radiolabels (DT-50 values were 8-10 days).No significant mineralisation occurred under sterile conditions.

Primary degradation occurred by hydrolysis and probably also microbially to produce transient degradation products in the aqueous phase which, themselves, were rapidly mineralised. There were four major (> 10% AR) degradation products present in the water phase, two from each half of the molecule, and a further two degradation products atca10% AR detected only after treatment with the hexylene glycol label. There were no degradation products present at > 10% AR in the water phase by the end of the study (59 DAT).

The DT-50 for the test substance in the water, determined by SFO kinetics, wasca0.6 days and the DT-50 values for the degradation products in the water phase were in the approximate range of 2-14 days, except for one degradation product detected from the hexylene glycol label that had an apparently longer DT-50 value. Although degradation rates were only determined at the higher of the two application rates, the mineralisation rates were not concentration dependent and therefore the primary degradation rates must also have been similar.

As a conclusion, neither 3-hydroxy-1,1-dimethylbutyl 2-ethyl-2-methylheptaneperoxoaten or its degradation products are likely to persist in natutal aerobic water systems