1,1,3,3-tetramethylbutyl 2-ethylperoxyhexanoate

Endpoint summary

Description of key information

The algae study was the only study where effects were seen. The ErC₁₀(72h) was calculated as 2.9 mg/L (Growth rate). The ErC₅₀(72h) was estimated as 7.1 mg/L (Growth rate) expressed as degraded parent material derived from average measured initial concentrations of Neopentyl alcohol and 2-Ethylhexanoic acid and the available decomposition mechanism.

The algae study indicates that the degradation product mixture have a higher toxicity than would be expected from the separate degradation products or from the parent material alone. For this reason, the toxicity was expressed as the amount of degraded parent needed to generate the observed effects. This was back calculated from the degradation product measurements and is an indicator of the absolute worst case toxicity to algae.

This situation happens in isolated test vessels, where single substances are degraded and maximum solubility can be elevated due to degradation products acting as solvents (e.g. acetone). In reality in surface water, this phenomenon will not occur because concentrations of substances will be much lower. Due to the quick hydrolysis of the parent substance (< 12h) concentrations of parent substance in the aquatic environment will be negligible.

Additional information

Short term toxicity to fish

1,1,3,3-tetramethylbutyl peroxy2-ethyl hexanoate is highly insoluble in water, and no toxicity up to the water solubility limit has been observed in previously conducted tests on daphnia and algae. Hence, to avoid vertebrate testing, read across is performed with the more soluble analogous substance CAS 22288 -41 -1. No toxicity up to the maximum water solubility was found, for this worst case material, therefore EL50 > ws. A FET (OECD 236) was performed with CAS 22288 -41 -1 and the registered substance to show similarity and to strengthen the read across. A loading of 10 mg/L test material in a semi static 96 hour test with daily refreshment did not result in any significant alterations to Danio rerio embryos for both substances. This concentration is far above the waters solubility of the substance. The results support that the substance is unlikely to be toxic to fish.

Short term toxicity to aquatic invertebrates

One OECD 202 GLP study is available. The toxicity of the test chemical to Daphnia Magna prepared as a Water Accommodated Fraction (WAF) due to its low solubility and degradation to multiple components was determined in a semi static system over an exposure period of 48 hours at several loading concentrations. WAF solutions were prepared for each test concentration by adding of an accurate amount of the test substance to the test media and allowing it to equilibrate under slow agitation over 36 hours in a sealed vessel. 

An exact EL50 determination was not possible as the substance displayed no toxicity despite a high test material loading being used at the highest concentration. No acute effects were observed. The test material and its subsequent degradation products can be concluded as not acutely toxic to Daphnia magna.

Long term toxicity to aquatic invertebrates

In a GLP study according to OECD guideline 211 the chronic toxicity of 1,1,3,3-tetramethylbutyl peroxy2-ethyl hexanoate (CAS 22288-43-3) and its degradation products to Daphnia magna in a 21 day reproduction test under semi-static conditions was investigated.

Due to the low water solubility of the substance and subsequent degradation to multiple components a WAF was prepared as described in the RSS. The test substance at its maximum achievable concentration in test medium and the accumulated degradation products resulting from a loading concentration of 10 mg/L degraded for 6 days did not have any detectable effects. It can be concluded that the water soluble degradation products as well as the residual parent material are not likely to display any chronic toxicity at the concentrations achievable in the environment.

Toxicity to aquatic algae and cyanobacteria

Two studies were performed to assess the toxicity of 1,1,3,3-TETRAMETHYLBUTYL PEROXY2-ETHYL HEXANOATE (CAS 22288-43-3) and its degradation product to aquatic algae. In the first OECD 201 study on the parent including degradation products, using WAF loading, no toxicity was observed below the water solubility limit. The second study with chemical analyses of parent material and degradation products the endpoints were expressed as the amount of degraded parent material needed to generate the observed effects. With measurements of concentrations of degradation products it was possible to express endpoints in different ways from the first study where only parent material concentrations were measured.

The ErC₁₀(72h) was calculated as 2.9 mg/L (Growth rate). The ErC₅₀(72h) was estimated as 7.1 mg/L (Growth rate) expressed as degraded parent material derived from average measured initial concentrations of Neopentyl alcohol and 2-Ethylhexanoic acid and the available decomposition mechanism.

The NOEC was determined as 2.7 mg/L (Growth rate) and the LOEC was determined as 3.7 mg/L (Growth rate) expressed as degraded parent material derived from measured initial concentrations of Neopentyl alcohol and 2-Ethylhexanoic acid and the available decomposition mechanism.

The limit test data dosed at the water solubility of the test material demonstrated that there was no significant difference between the control and the degraded and non-degraded parent material at this concentration. Hence the parent material can be concluded to display no effects up to its solubility limit.

The algae study indicates that the degradation product mixture have a higher toxicity than would be expected from the separate degradation products or from the parent material alone. For this reason, the toxicity was expressed as the amount of degraded parent needed to generate the observed effects. This was back calculated from the degradation product measurements and is an indicator of the absolute worst case toxicity to algae.

Toxicity to microorganisms

The EC10 and EC50 of 1,1,3,3-tetramethylbutyl 2-ethylperoxyhexanoate for activated sludge after 3 hours contact time are > 1276 mg/L.