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

Toxicity to aquatic algae and cyanobacteria

Description of key information

Two studies were performed to assess the toxicity of 1,1,3,3-TETRAMETHYLBUTYL PEROXY-2-ETHYL HEXANOATE (CAS 22288-43-3) and its degradation product to aquatic algae. In the first OECD 201 study 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.

Key value for chemical safety assessment

EC50 for freshwater algae:

7.1 mg/L

EC10 or NOEC for freshwater algae:

2.9 mg/L

Additional information

One OECD 201 study carried out under GLP is available. Due to the speed the test chemical reaches saturation in water, preliminary information on half life and preliminary studies, a 3 day stirring period for the WAF vessels was chosen. This means that a mixture of the parent peroxide, degradation products (including temporary intermediate breakdown products) and any impurities were essentially tested for their effects on the test organism. All critical validity criteria for the test and analytical method were met. Chemical analysis of the parent only was conducted to confirm the presence and subsequent disappearance of the main peroxide ingredient. Results were expressed as loading values as is acceptable for test solutions containing multiple components. The concentration of the active ingredient was also measured as far as stability allowed at the start and end of the test. Data indicates therefore that the increasing effects observed on the test organism are likely not due to the initial parent peroxide concentration but the increasing level of breakdown products. To conclude, no toxicity was observed up to the water solubility of the parent.

A second study was performed in order to predict the effects of 1,1,3,3 -tetramethylbutyl peroxy-2-ethylhexanoate and its degradation productsin an aquatic environment. an Algal Growth Inhibition test was conducted in accordance with OECD test guidelines. In this study parent material as well as two degradation products were analyzed at the beginning and end of the test. 

Comparing effects expressed as loading rates of the parent material both studies gave similar results. 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.

Due to the degradation product mixture having a higher toxicity than would be expected from the separate degradation products (see table below) or from the parent material alone, the toxicity has been 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. The parent material and degradation products may also be assessed separately as required. 

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.

 

Measured and estimated data on lagae for the degradation products:

Substance	Test data [mg/L]	ECOSAR [mg/L]
2 -ethylhexanoic acid	ErC10: 31.9 ErC50: 49.3	EC50: 34.6 ChV: 109
Neopentyl alcohol	-	EC50: 106 ChV: 23.7
Acetone	- TTC (toxic threshold concentration) 530	EC50: 711 ChV: 118