Bis(4-methylbenzoyl)peroxide

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

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP study according to protocol.

Qualifier:

according to guideline

Guideline:

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

Deviations:

yes

Remarks:

Ammonium chloride was omitted from the medium to prevent oxygen consumption due to nitrification (omission does not result in nitrogen limitation as shown by the biodegradation of the reference compound).

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

Secondary activated sludge (14-11-2013) was obtained from the wastewater treatment plant Nieuwgraaf in Duiven, The Netherlands. This plant is an activated sludge plant treating predominantly domestic wastewater. The activated sludge was preconditioned to reduce the endogenous respiration rates. To this end, 400 mg Dry Weight (DW)/L of activated sludge was aerated for one week. The sludge was diluted in the BOD bottles (van Ginkel and Stroo, 1992).

Duration of test (contact time):

28 d

Initial conc.:

2.7 mg/L

Based on:

test mat.

Initial conc.:

2 mg/L

Based on:

act. ingr.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium: The nutrient medium of the Closed Bottle test contained per liter of deionized water; 8.5 mg KH2PO4, 21.75 mg K2HPO4, 33.3 mg Na2HPO4·2H2O, 22.5 mg MgSO4·7H2O, 27.5 mg CaCl2, 0.25 mg FeCl3·6H2O. Ammonium chloride was omitted from the medium to prevent nitrification.
- Solubilising agent (type and concentration if used): Accurate administration of the water-insoluble test substance was accomplished by preparing a stock solution of 1.0 g/L in DCM. The test substance in DCM (0.8 mL) was added to the bottles. The solvent was allowed to evaporate overnight in a ventilated hood.
- Test temperature: 22-24 °C
- pH: The pH of the media was 7.3 at the start of the test. The pH of the medium at day 28 was 7.3 (controls) and 7.2 (test).
- pH adjusted: no
- Continuous darkness: yes

TEST SYSTEM
Use was made of 10 bottles containing only inoculum, 10 bottles containing only inoculum in bottle treated with DCM (added and evaporated), 10 bottles containing inoculum and test substance, and 6 bottles containing sodium acetate and inoculums. The concentrations of the test substance, and sodium acetate in the bottles were 2.7 (2.0 active) and 6.7 mg/L, respectively. Each of the prepared solutions was dispensed into the respective group of BOD bottles so that all bottles were completely filled without air bubbles. The zero time bottles were immediately analyzed for dissolved
oxygen using an oxygen electrode. The remaining bottles were closed and incubated in the dark. Two duplicate bottles of all series were withdrawn for analyses of the dissolved oxygen concentration at day 7, 14, 21, and 28.

Reference substance:

acetic acid, sodium salt

Parameter:

% degradation (O2 consumption)

Value:

88

Sampling time:

28 d

Details on results:

- Theoretical oxygen demand (ThOD)
The calculated theoretical oxygen demand (ThOD) of the active substance, di-(4-methylbenzoyl) peroxide, 75% in water, is 2.07 mg/mg. The ThOD of the test substance containing 27% water is 1.5 mg/mg. The ThOD of sodium acetate is 0.8 mg/mg

- Toxicity
Inhibition of the degradation of a well-degradable compound, e.g. sodium acetate by the test substance in the Closed Bottle test was not determined because
possible toxicity of di-(4-methylbenzoyl) peroxide, 75% in water to microorganisms degrading acetate is not relevant. Inhibition of the endogenous
respiration of the inoculum by the test substance at day 7 was not detected. Therefore, no inhibition of the biodegradation due to the "high" initial test substance concentration is expected.

- Validity of the test
The validity of the test is demonstrated by an endogenous respiration of 1.2 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 93. Finally, the validity of the test is
shown by oxygen concentrations >0.5 mg/L in all bottles during the test period.

- Biodegradability
Di-(4-methylbenzoyl) peroxide, 75% in water is biodegraded by 88% at day 28 in the Closed Bottle test. The time required to obtain 60%
biodegradation immediately following the attainment of 10% biodegradation was 9 days. Di-(4-methylbenzoyl) peroxide, 75% in water is therefore classified as
readily biodegradable based on the biodegradation percentage of 88% at day 28 and the time window of approximately 9 days.

Results with reference substance:

The biodegradation percentage of the reference compound, sodium acetate, at day 14 was 93.

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

This study is performed according to protocol under GLP and valid without restrictions. The results can therefore be used for Classification and Labelling and for Risk Assessment purposes.

Executive summary:

In order to assess the biotic degradation, a ready biodegradability test 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 slightly modified OECD, EU and ISO Test Guidelines, and in compliance with the OECD principles of Good Laboratory Practice.

The presence of di-(4-methylbenzoyl) peroxide, 75% in water did not cause a reduction in the endogenous respiration. The test substance is therefore considered to be non-inhibitory to the inoculum. Di-(4-methylbenzoyl) peroxide, 75% in water was biodegraded by 88% at day 28 in the Closed Bottle test. Over 60% biodegradation was achieved in a period of approximately 9 days immediately following the attainment of 10% biodegradation. Hence, this substance should be classified as readily biodegradable.

The test is valid as shown by an endogenous respiration of 1.2 mg/L and by the total mineralization of the reference compound, sodium acetate. Sodium acetate was degraded by 93% of its theoretical oxygen demand after 14 days. Finally, the most important criterion was met by oxygen concentrations >0.5 mg/L in all bottles during the test period.

Description of key information

The test substance is readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Additional information

In a ready biodegradability study performed under GLP, according to OECD 301D it was shown that the test substance is readily biodegradable with 88% biodegradation over 28 days.