Di-tert-butyl 3,3,5-trimethylcyclohexylidene diperoxide

Endpoint summary

Description of key information

Acute data of various reliability, based on international guidelines, are available for three trophic levels: Algae, Invertebrates and Fish and are available and are summarised in the table below. One valid chronic daphnia endpoint is available and a single chronic sediment study has been conducted.

In the species tested, an effect (growth inhibition) was found for the algaePseudokirchneriella subcapitata. The test was performed on this specie following the OECD 201 guideline. Based on the geometric mean of the tests, a NOEC(72h) of 0.11 mg/L was calculated (corresponding to 1 mg/L of nominal concentration). This is well above the water solubility.

Early studies by Höger (2011) and that by van Wijk & Garttener-Arends (1999) were performed using high energy techniques causing emulsions to be formed at concentrations greater than the true solubility limit of the registered substance.

Thus all effects value in daphnids found to date were from ecotoxicity studies performed well above the true limit of solubility (as emulsions).

Under environmental conditions in which the substance would pass through a WWTP, it would not be expected to be present in the form of an emulsion but would rapidly and strongly adsorb to particulate matter (due to the log Kow >7) and therefore the results from these studies are not considered relevant for risk assessment purposes.

Using a more appropriate test methodology but as a non-GLP screening study, Kean (2013) prepared two series of WAFs for the substance using a slow-stir preparation method at loading rates of 0.2, 0.5, 1.0, 5.0, 10 and 100 mg/L of which one series was centrifuged. At 48 h a maximum of 1 daphnid out of 10 was immobile and this only in WAFs of 5, 10 and 100 mg/L. In the non-centrifuged group no immobilisations were observed at a WAF of 0.2 mg/L, approximately 100 times higher than the determined solubility limit, only 3 out of 10 daphnids were immobilized at 0.5 mg/L and in contradiction with the early studies only 6 out of 10 daphnids were found immobile in the 1 mg/L WAF while only 50% were immobilised at 5 and 10 mg/L. None of the WAFs up to 100 mg/L resulted in 100 % immobilisation (maximum 80% at 100 mg/L).

The most recent and key study by Harris (2013) takes a similar approach to (Kean 2013) in its preparation of the test solutions to ensure adequate removal of undissolved material or dispersions. The measured concentrations observed were considerably closer to the true solubility limit of the test material eliminating the problems observed with earlier studies. No Effects were observed up to1 mg/L of test material. Furthermore due to the potential for loss of test material in a semi static or static setup and extended flow through sub-chronic supporting study was conducted (Kean 2013) to first brood. This demonstrated that also with continual replacement no acute effects were observed.

One acute study is available on Medaka fish,Oryzias latipes, and no toxicity was observed at the highest concentrations tested. Therefore, an LC50(48h) > 500 mg/L of 3,3,5-trimethylcyclohexylidene)bis[(1,1 dimethylethyl)peroxide] was derived for the fish.

The conclusion from the available acute studies is that no acute toxicity can be determined at or well above the solubility limit when some care is taken in the preparation of the tests concentrations. No EC50 can be derived from any of the acute ecotoxicity studies and no acute classification is necessary for this substance.

In order to determine if chronic effects occur a flow through study (OECD 211 withDaphnia magna) with a nominal loading of 15 mg/L of the test substance was conducted using a slow stir method (WAF) and two stage separation of the stock solution to avoid the testing of dispersed material. The stock (or large WAF solution 30L) was continually pumped into the test system the WAF itself was refreshed entirely 3 times per week to ensure continual presence of the test material. Analytical measurements demonstrated the presence of the test material in the WAF solution (33.9µg/L) throughout the test as well as in the secondary separation (12.8 µg/L) vessel at concentrations above the limit of solubility. Fed from the secondary separation vessels triplicate test vessels containing 10 test organisms were exposed to the test substance for 21 days over which primarily the effects on reproduction were assessed in comparison to an identical triplicate control.

No significant effects on reproduction or body length were observed. Indicating that1,1-Di(tert-butylperoxy)-3,3,5-trimethylcyclohexane causes no chronic effects toDaphnia magnaat or as close as possible to it's water solubility limit.

Due to the tendency of1,1 -Di(tert-butylperoxy)-3,3,5 -trimethylcyclohexane to partition to the sediment a chronic sediment test (OECD 225 Lumbriculus variegatus)was conducted. However the data remains of debatable environmental relevance due to steady state not being reached in the sediment. Pore water concentrations thousands of times higher than the solubility limit were measured and the characteristics of the test substance indicate that the test material is unlikely to be able to pass treatment plants. This has been confirmed by a subsequent sewage treatment simulation study.

As additional supporting evidence effluent tests for Algae(72h) and Daphnia (21d) were conducted. No toxicity was detected to P.Subcapitata or D.magna when testing in undiluted treated effluent.

Species Experimental data Algae:Pseudokirchneriella subcapitata NOEC(72h) = 0.11 mg/L  (>limit of solubility) Invertebrates:Daphnia magna EC50(48h) >limit of solubility EC50(21d) > limit of solubility Fish:Oryzias latipes LC50(48h) > 500 mg/L  (>limit of solubility) Sediment-dwelling oligochaete:Lumbriculus variegatus  NOEC (28d) 5.1 mg/kg Sediment/soil dwelling nematode:Caenorhabditis elegans     NOEC(96h) 1000 mg/kg/dw  Earthworm Reproduction :Eisenia fetida  NOEC(28d) 52.9 mg/kg/dw  Toxicity to terrestrial plants (most sensitive endpoint):Onion  NOEC(21d) 333.3 mg/kg/dw  Toxicity to soil microrganisms  NOEC(28d) 1000mg/kg/dw  Effluent Test - P.Subcapitata  No effects in undiluted effluent  Effluent Test - D magna (21d)  No Effects in undiluted effluent

Additional information

This substance is the main source material in a proposed family of Peroxyketal organic peroxides with very similar / identical properties. The justification for this approach has been attached in secton 13. The intention being facilitate the timely PBT / Ecotoxicity assessment of the other members of the group without uneccesary testing.