Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

When released in water

The determination of the hydrolysis as a function of pH was based on EEC Directive C.10 "Abiotic degradation: Hydrolysis as a function of pH"(1984). At pH 4, 7 and 9, a decrease in concentration > 50% was observed after 2.4 hours (half-life time < 2.4 hours). Hence it was concluded that the concerned substance is hydrolytically unstable at pH 4, 7 and 9,under the conditions of the test. The test was performed at 50.0 ± 0.5°C.

Biodegradation

The ready biodegradability of 3-hydroxy-1,1-dimethylbutyl 2-ethyl-2-methylheptaneperoxoate was evaluated in a study performed in accordance with OECD testing guideline 301 B (Bogers, 1993).

The relative degradation values calculated from the measurements performed during the test period showed a slight degradation at 10 mg/L (16%) but no significant biodegradation at 20 mg/L (4.4%). However, since the substance is hardly soluble in water, the lack of microbial degradation could be a consequence of the limited availability for micro-organisms. Thus under the conditions of this test, 3-hydroxy-1,1-dimethylbutyl 2-ethyl-2-methylheptaneperoxoate was not readily biodegradable.

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 at ca 10% 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, was ca 0.6 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-methylheptaneperoxoate or its degradation products are likely to persist in natutal aerobic water systems.

When released in soil

A study was performed to estimate the adsorption coefficient (Koc) of 3-hydroxy-1,1-dimethylbutyl 2-ethyl-2-methylheptaneperoxoate by HPLC. A log10Kocvalue of 3.3 (equivalent Koc= 2100) has been determined.