Di-tert-butyl 1,1,4,4-tetramethylbut-2-yn-1,4-ylene diperoxide

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:

from 2001-01-19 to 2001-08-29

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

(1992)

Deviations:

yes

Remarks:

see 'Principles of method it other than guideline'

Qualifier:

according to guideline

Guideline:

EU Method C.6 (Degradation: Chemical Oxygen Demand)

Version / remarks:

(1984)

Deviations:

yes

Remarks:

see 'Principles of method it other than guideline'

Principles of method if other than guideline:

A minor deviation of the test procedures described in the guidelines was introduced: instead of an effluent/extract/mixture, activated sludge was used as an inoculum. The activated sludge was preconditioned to reduce the endogenous respiration rates.

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: Secondary activated sludge was obtained from the WWTP Nieuwgraaf in Duiven, The Netherlands (2001-01-19). The WWTP Nieuwgraaf is an activated sludge plant treating predominantly domestic waste water.
- Laboratory culture: Yes
- Pretreatment: The activated sludge was preconditioned to reduce the endogenous respiration rates. To this end, 200 mg Dry Weight (DW)/L of activated sludge was aerated for one week.
- Concentration of sludge: 2 mg DW/L
- Initial cell/biomass concentration: 2 mg DW/L

Duration of test (contact time):

28 d

Initial conc.:

0.33 mg/L

Based on:

test mat.

Initial conc.:

2.1 mg/L

Based on:

test mat.

Initial conc.:

6.7 mg/L

Based on:

test mat.

Details on study design:

TEST CONDITIONS
- Composition of medium: according to OECD guideline 301
- Test temperature: 19.0 to 21.2 °C
- pH: 6.7 to 7.2

TEST SYSTEM
- Culturing apparatus: 250 to 300 mL BOD (biological oxygen demand) bottles with glass stoppers
- Number of culture flasks/concentration: Use was made of 10 bottles containing only inoculum, 10 bottles containing test substance and inoculum, 10 bottles containing mineral oil and inoculum, and 6 bottles containing sodium acetate and inoculum. The concentrations of the test substance in mineral oil, mineral oil and sodium acetate in the bottles were 2.1, 0.33 and 6.7 mg/L, respectively.
- Measuring equipment: The dissolved oxygen concentrations were determined electrochemically using an oxygen electrode (WTW Trioxmatic EO 200) and meter (WTW OXI 530)

STATISTICAL METHODS:
The validity of the test is demonstrated by an endogenous respiration of 1.6 mg/L at day 28. Furthermore, the differences of the replicate values at day 28 were less than 20 %. The biodegradation percentage of the reference compound, sodium acetate, at day 14 was 83. Finally, the validity of the test is shown by oxygen concentrations >0.5 mg/L in all bottles during the test period.

Reference substance:

other: Sodium acetate anhydrous

Test performance:

The dissolved oxygen concentrations were determined electrochemically using an oxygen electrode (WTW Trioxmatic EO 200) and meter (WTW OXI 530) (Retsch, Ochten, The Netherlands). The pH was measured using a Consort pH meter (Salm en Kipp BV, Breukelen, The Netherlands). The temperature was measured and recorded with a thermo couple connected to a data logger. The dry weight (DW) of the inoculum was determined by filtrating 50 mL of the activated sludge over a pre-weighted 12 µm Schleicher and Schüll filter.

Parameter:

% degradation (O2 consumption)

Value:

2

Sampling time:

7 d

Parameter:

% degradation (O2 consumption)

Value:

0

Sampling time:

14 d

Parameter:

% degradation (O2 consumption)

Value:

4

Sampling time:

21 d

Key result

Parameter:

% degradation (O2 consumption)

Value:

4

Sampling time:

28 d

Key result

Parameter:

% degradation (O2 consumption)

Value:

0

Sampling time:

140 d

Details on results:

Mineral oil used as solvent was biodegraded 0 % at day 28 in the Closed Bottle test. Since, in the prolonged Closed Bottle test the test compound is biodegraded 0 at day 140 it should be classified as not biodegradable.
The test item in solvent was biodegraded 4 % at day 28 in the Closed Bottle test. Since, in the prolonged Closed Bottle test the test compound was biodegraded 0 % at day 140, it should be classified as not biodegradable. Lack of biodegradation does not mean that the test item in mineral oil is recalcitrant in nature. The stringency of the test procedures could account for the recalcitrance in the Closed Bottle test.

Results with reference substance:

The biodegradation percentage of the reference compound, Sodium acetate, at day 14 was 83 %.

Validity criteria fulfilled:

yes

Interpretation of results:

under test conditions no biodegradation observed

Conclusions:

The test item in solvent was biodegraded 4 % at day 28 in the Closed Bottle test. In the prolonged Closed Bottle test the test compound was biodegraded 0 % at day 140. The biodegradation reached at the last day of the test demonstrated that this test should be classified as not ready biodegradable.

Executive summary:

A ready biodegradability test with the test item in solvent was performed which allows the biodegradability to be measured in an aerobic aqueous medium. The ready biodegradability was determined in the Closed Bottle test performed according to OECD guideline 301 and EU method C.6. The test was prolonged because the pass level was not reached at day 28.
Slight inhibition of the endogenous respiration of the inoculum by the test substance and mineral oil was detected. Therefore, inhibition of the biodegradation due to the "high" initial concentrations may occur.
The test item in solvent was biodegraded 4 % at day 28 in the Closed Bottle test. In the prolonged Closed Bottle test this compound was biodegraded 0 % at day 140. Under the test conditions chosen, no biodegradation was observed.

The validity of the test is demonstrated by an endogenous respiration of 1.6 mg/L at day 28. Furthermore, the differences of the replicate values at day 28 were less than 20 %. The biodegradation percentage of the reference compound, sodium acetate, at day 14 was 83. Finally, the validity of the test is shown by oxygen concentrations > 0.5 mg/L in all bottles during the test period.

Description of key information

In a closed bottle test according to OECD guideline 301, no biodegradation was observed.

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Type of water:

freshwater

Additional information

A ready biodegradability test with the test item in mineral oil was performed which allows the biodegradability to be measured in an aerobic aqueous medium. The ready biodegradability was determined in the Closed Bottle test performed according to OECD guideline 301 and EU method C.6. The test was prolonged because the pass level was not reached at day 28.
Slight inhibition of the endogenous respiration of the inoculum by the test substance and mineral oil was detected. Therefore, inhibition of the biodegradation due to the "high" initial concentrations may occur.
The test item in solvent was biodegraded 4 % at day 28 in the Closed Bottle test. In the prolonged Closed Bottle test this compound was biodegraded 0 % at day 140. Under the test conditions chosen, no biodegradation was observed.

The validity of the test is demonstrated by an endogenous respiration of 1.6 mg/L at day 28. Furthermore, the differences of the replicate values at day 28 were less than 20 %. The biodegradation percentage of the reference compound, sodium acetate, at day 14 was 83. Finally, the validity of the test is shown by oxygen concentrations > 0.5 mg/L in all bottles during the test period.
The test substance should be classified as not biodegradable. Lack of biodegradation does not mean that the test item in mineral oil is recalcitrant in nature. The stringency of the test procedures could account for the recalcitrance in the Closed Bottle test.