tert-pentyl 2-ethylperoxyhexanoate

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

April 2012 - September 2012

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: 1a GLP guideline study

Reason / purpose for cross-reference:

reference to same study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

The inoculum was prepared in the laboratory from secondary effluent from wastewater treatment plants with activated sludge treating the domestic wastewater in the municipalities of Abidos and Mourenx (France, 64). The inoculum used provides bacteria at concentration levels usually situated between 10^4 and 10^6 cells per litre.
The inoculum has not been pre-conditioned.

Duration of test (contact time):

28 d

Initial conc.:

2 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

A 10 mg/L solution of TERT-AMYL PEROXY-2-ETHYLHEXANOATE in dilution water was prepared and used in a proportion of 200 mL/L of inoculated medium, i.e. 2 mg/L, corresponding to a theoretical O2 mass of 1.5 mg per flask (ThOD 2.5 mg O2/mg). Test flasks are filled with this solution.

Sodium benzoate (108 mg) was dissolved in 100 mL of mineral medium. A volume of 3.33 mL/L of this solution are diluted in inoculated medium, i.e. 1.08 mg per flask, which corresponds to a theoretical O2 mass of 1.804 mg per flask (ThOD 1.67 mg O2/mg). Procedure control flasks are filled with this solution.
In the inhibition monitoring flask, 100 mL/L of test item solution and 1.667 mL of Reference item solution are mixed with inoculated medium. Toxicity control flasks are filled with this solution. The corresponding theoretical mass of O2 is 1.65 mg per flask.

The test solutions were inoculated with micro-organisms from a heterogeneous population, and stored in closed, completely full bottles, away from light and at a constant temperature (22.6 to 22.9 °C).

Reference substance:

benzoic acid, sodium salt

Preliminary study:

No preliminary study

Parameter:

% degradation (O2 consumption)

Value:

62

Sampling time:

28 d

Results with reference substance:

The percentage degradation of the reference item reached a level of 84 % by 14 days which is above the required level of 60 %.

The calculated theoretical oxygen demand of TERT-AMYL PEROXY-2-ETHYLHEXANOATE is 2.5 mg O2/mg. This theoretical oxygen demand is calculated by assuming formation of ammonium, water and carbon dioxide (if no nitrification is observed). The theoretical oxygen demand of sodium benzoate is 1.67 mg O2/mg. The maximum degradation level of TERT-AMYL PEROXY-2-ETHYLHEXANOATE was 62 % in 28 days. TERT-AMYL PEROXY-2-ETHYLHEXANOATE did not inhibit the micro-organisms as shown by the toxicity control flask where biodegradation percentage is already 71 %, higher than 25 % after 14 days.

Validity criteria fulfilled:

yes

Remarks:

See conclusions

Interpretation of results:

readily biodegradable

Conclusions:

The following quality criteria have been met:

The oxygen uptake of the inoculum blank has been 0.75 mg O2/L in 28 days, which is below 1.5 mg O2/L.

The residual concentration of oxygen did not fall below 0.5 mg/L at any time.

The difference of extremes of replicate values of the removal of test chemical at the plateau, at the end of the test, or at the end of the 10-d window, was less than 20 %.

The percentage degradation of the reference item reached a level of 84 % by 14 days which is above the required level of 60 %.

In the toxicity control flasks, containing both the reference item and TERT-AMYL PEROXY-2- ETHYLHEXANOATE, the percentage of biodegradation reached 71 % after 14 days. Since this value is higher than 25%, the test item is not inhibitory for inoculum.

Executive summary:

The ready biodegradability of TERT-AMYL PEROXY-2-ETHYLHEXANOATE was evaluated in a study performed in accordance with OECD testing guideline 301 D and GLP requirements.

 

The maximum level of biodegradation was 62% in 28 days. Therefore, according to these results, TERT-AMYL PEROXY-2-ETHYLHEXANOATE is considered as readily biodegradable but failing the 10 -days window.

This is the conclusion given in the report, but for this type of substance the following holds:

In ready biodegradability tests, the time window concept has been introduced as a simple alternative to quantify the rate of biodegradation. In order to pass the test, over 60% biodegradation has to be achieved within a period of 10 days immediately following the attainment of 10% biodegradation. An estimation of growth rates from biodegradation curves obtained in for instance ready biodegradability tests is only possible and valid when a single water-soluble chemical substance is studied.

 

Tert-amyl-peroxy-2-ethylhexanoate is a chemical in which two moieties are is linked together with a peroxy bond. Upon hydrolysis of tert-amyl-peroxy-2-ethylhexanoate, 2-methyl-2-butanol and 2-ethylhexanoate require the concerted action of at least two microorganisms as a single organism usually lacks the full complement of enzymatic capabilities. In ready biodegradability tests, the two moieties usually do not have identical lag periods and are thus degraded sequentially. The biodegradation of the two moieties may be fully in line with the time window criterion when judged as separate chemicals. The biodegradation curve of the peroxide should therefore not be used to assess a time window.

Tert-amyl-peroxy-2-ethylhexanoate can therefore be considered readily biodegradable.

In the test conditions, no inhibitory effect of TERT-AMYL PEROXY-2-ETHYLHEXANOATE on the micro-organisms of the inoculum was observed.

Validity criteria were fulfilled.

Description of key information

OECD 301D, GLP, key study, validity 1:
28 days, 62%: TERT-AMYL PEROXY-2-ETHYLHEXANOATE is readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Additional information

In ready biodegradability tests, the time window concept has been introduced as a simple alternative to quantify the rate of biodegradation. In order to pass the test, over 60% biodegradation has to be achieved within a period of 10 days immediately following the attainment of 10% biodegradation. An estimation of growth rates from biodegradation curves obtained in for instance ready biodegradability tests is only possible and valid when a single water-soluble chemical substance is studied.

 

Tert-amyl-peroxy-2-ethylhexanoate is a chemical in which two moieties are is linked together with a peroxy bond. Upon hydrolysis of tert-amyl-peroxy-2-ethylhexanoate, 2-methyl-2-butanol and 2-ethylhexanoate require the concerted action of at least two microorganisms as a single organism usually lacks the full complement of enzymatic capabilities. In ready biodegradability tests, the two moieties usually do not have identical lag periods and are thus degraded sequentially. The biodegradation of the two moieties may be fully in line with the time window criterion when judged as separate chemicals. The biodegradation curve of the peroxide should therefore not be used to assess a time window.