Registration Dossier
Registration Dossier
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EC number: 201-128-1 | CAS number: 78-63-7
Endpoint summary
Administrative data
Description of key information
One key study was available on the biodegradation of di-tert-butyl 1,1,4,4-tetramethyltetramethylene diperoxide.
This study was performed according to modified OECD Test Guidelines to permit prolonged measurements with no GLP statement.
In the SCAS test, di-tert-butyl 1,1,4,4-tetramethyltetramethylene diperoxide was exposed to activated sludge maintained by daily addition of primary settled sewage for a period of 8 weeks. The test substance caused no reduction of the biodegradation of the organic compounds present in primary settled sewage. Therefore the test substance is considered to be non-inhibitory to the activated sludge. The test substance was not degraded in prolonged Closed Bottle tests inoculated with unacclimated and acclimated sludge from the SCAS unit. This result demonstrates that microorganisms do not have the ability to grow on this organic peroxide under aerobic conditions. Potential decomposition products of the test substance i.e. tert butanol and 2,5-dimethyl-2,5-hexanediol were degraded in Closed Bottle tests with both acclimated and unacclimated sludge (> 80% within 56 days).The length of the lag period found with 2,5-dimethyl-2,5-hexanediol with acclimated sludge was short compared to the period obtained with unacclimated sludge. This result suggests that the peroxide bond of di-tert-butyl 1,1,4,4-tetramethyltetramethylene diperoxide is cleaved in the SCAS unit.
Additional information
In first instance in our comments to the draft decision received 27 August 2021, it was proposed to start with a Sediment simulation study (OECD 308), because the substance has a high log Kow of 7.34 and a high adsorption coefficient (log Koc 4.72) and it is shown in several hydrolysis studies, as well as aquatic ecotoxicity studies that the substance is lost from the water phase over time and measured concentrations in test medium are very low.
In the non-GLP OECD 303A study almost all test substance is removed from the water phase (> 99.89%). This suggests that exposure of the aquatic compartment is minimal and surface water is not the compart concern. Due to the high adsorption potential sediment was considered compartment of concern.
It is now known that it is not possible to obtain radiolabelled material of this test substance. Consequently, it will be difficult or even impossible to obtain a good mass balance in Simulation studies in sediment or soil and therefore, these studies will most likely be technically impossible. In surface water there is a higher chance to obtain better recoveries.
Even though conduct of the Simulation study in surface water is still considered difficult and not most relevant, feasibility of the Simulation study in surface water will be determined first.
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