O,O-tert-butyl isopropyl monoperoxycarbonate

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

Experimental start date: 1998-10-14 Experimental completion date: 1999-02-18

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

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

Deviations:

yes

Remarks:

Please see any other info on materials and methods for details of deviation

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

• name: tert-butylperoxyisopropylcarbonate
• Akzo Nobel trade name: Trigonox BPIC-C75
• composition: tert-butylperoxyisopropylcarbonate 75%
isododecane 23%
• batch/lot No. 0419804 130350
• solubility in water insoluble
• storage at room temperature in the dark

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, non-adapted

Details on inoculum:

Secondary activated sludge was obtained from the WWTP Nieuwgraaf in Duiven, The Netherlands (1998-10-22).
The WWTP Nieuwgraaf is an activated sludge plant treating predominantly domestic waste water.
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. The sludge was diluted to a concentration of 2 mg DW/L in the BOD bottles.

Duration of test (contact time):

112 d

Initial conc.:

2 mg/L

Based on:

test mat.

Initial conc.:

6 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

Deionized water
Deionized water containing no more than 0.01 mg/L Cu and 1 mg/L non-purgeable organic carbon was prepared in an Elgastat water purification system (Elga, Breukelen, The Netherlands).

Test bottles
The test was performed in 250 to 300 ml BOD (biological oxygen demand) bottles with glass stoppers.

Nutrient solution and stock solutions
The nutrient medium of the Closed Bottle test contained per liter of deionized water: 8.5 mg KH2P04, 21.75 mg K2HP04, 4 mg Na2HP04·2H20, 22.5 mg MgS04·7H20, 27.5 mg CaCl2, 0.25 mg FeCl3·6H20. Ammonium chloride was omitted from the medium to prevent nitrification. Due to this omission the pH of the medium decreased slightly.
The decrease of the pH does not effect the biodegradation in the Closed Bottle test. Sodium acetate. trihydrate was added to the bottles using a stock solution of 1.7 g/L.
tert-butylperoxyisopropylcarbonate is a poorly soluble substance in water and therefore the test substance was first dissolved in dichloromethane (1 g/l). The test substance in dichloromethane (0.54 ml) was added to 2 g silica gel (100-200 mesh) weighed in a glass petri dish. The solvent was allowed to evaporate by placing the petri dish in a ventilated hood for 3 hours, and the entire contents were then transferred to the BOD bottle. During the test period, the test compound should be released slowly from the silica gel. Although no additional oxygen consumption was expected, controls with silica gel were carried out as well.

Test procedures
The Closed Bottle test was performed according to the study plan.
Use was made of 10 bottles containing silicagel and inoculum, 10 bottles containing test substance, silicagel and inoculum, 6 bottles containing only inoculum, and 6 bottles containing sodium acetate and inoculum. The concentrations of the test compound and sodium acetate in the bottles were 2.0 and 6.7 mg/L, respectively.
The inoculum was diluted to 2 mg DW/L in the closed bottles. 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 at 20°c ± 1°c 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.

Determination of oxygen, pH, dry weight and temperature
The dissolved oxygen concentrations were determined electrochemically using an oxygen electrode and meter. 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 100 ml of the activated sludge over a preweighed 12 mm Schleicher and Scholl filter. This filter was .dried for 1.5 hours at 104°C and weighed after cooling. DW was calculated by subtracting the weighed filters.

Reference substance:

other: Sodium acetate trihydrate

Key result

Parameter:

% degradation (O2 consumption)

Value:

23

Sampling time:

28 d

Key result

Parameter:

% degradation (O2 consumption)

Value:

49

Sampling time:

112 d

Details on results:

ThOD
The calculated theoretical oxygen demand of tert-butylperoxyisopropylcarbonate in isododecane is 1. 75 mg/mg.
The theoretical oxygen demand 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 compound in the Closed Bottle test was not determined because possible toxicity of tert-butylperoxyisopropylcarbonate to microorganisms degrading acetate is not relevant. Inhibition of the endogenous respiration of the inoculum by the test substance was not detected. Therefore, no inhibition of the biodegradation due to the "high" initial concentration of the test compound is expected.

Test conditions
The pH of the media was 7.1 at the start of the test. The pH of the medium at day 28 was 6.7. Temperatures ranged from 19 to 21°C.

Validity of the test
The validity of the test is demonstrated by an endogenous respiration of 1.1 mg/Lat 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 76%. Finally, the validity of the test is shown by oxygen concentrations >0.5 mg/Lin all bottles during the test period.

Results with reference substance:

The biodegradation percentage of the reference compound, sodium acetate, at day 14 was 76%

Dissolved oxygen concentrations (mg/L) in the closed bottles.

Time (days	Oxygen Concentration (mg/L)
	Ocs	Ots	Oc	Oa
0	8.7	8.7	8.7	8.7
	8.7	8.7	8.7	8.7
Mean	8.7	8.7	8.7	8.7
7	8.3	7.9	8.3	4.5
	8.3	8	8.4	4.5
Mean	8.3	8	8.4	4.5
14	8	7.4	8.1	4
	8	7.5	8	4
Mean	8	7.5	8.1	4
21	7.7	7
	7.8	7.1
Mean	7.8	7.1
28	7.6	6.7
	7.5	6.8
Mean	7.6	6.8
42	7.4	6.3
	7.4	6.4
Mean	7.4	6.4
56	7.2	5.6
	7.3	5.7
Mean	7.3	5.7
84	6.9	5.4
	7.2	5.4
Mean	7.1	5.4
112	6.8	5.3
	7.2	5.2
Mean	7	5.3

O_cs = Mineral nutrient solution without test material but with inoculum and evaporated silica gel.

O_ts = Mineral nutrient solution with test material (2.0 mg/L), silica gel and inoculum.

O_c = Mineral nutrient solution without test material but with inoculum.

O_a = Mineral nutrient solution with sodium acetate (6.7 mg/L) and inoculum.

Oxygen consumption (mg/L) and the percentages biodegradation of tert-butylperoxyisopropylcarbonate

(BOD/ThOD) and sodium acetate (BOD/ThOD)in the Closed Bottle test.

Time (days)	Oxygen consumption (mg/L) Biodegradation (%)		Biodegradation (%)
	Test	Acetate	Test	Acetate
0	0	0	0	0
7	0.3	3.9	9	72
14	0.5	4.1	14	76
21	0.7		20
28	0.8		23
42	1		29
56	1.6		46
84	1.7		49
112	1.7		49

Validity criteria fulfilled:

yes

Interpretation of results:

inherently biodegradable

Conclusions:

tert-butylperoxyisopropylcarbonate was tested in the Closed Bottle in the presence of silica gel was biodegraded 23% at day 28. Silica gel was used because it permits an accurate administration of the test compound. In the prolonged Closed Bottle test the biodegradation percentage reached 49% at day 112.
Hence, tert-butylperoxyisopropylcarbo.nate should be classified as inherently biodegradable. The biodegradation percentage reached at the last day of the test indicates that tert-butylperoxyisopropylcarbonate was completely mineralized.

Executive summary:

tert-butylperoxyisopropylcarbonate was tested in the Closed Bottle in the presence of silica gel was biodegraded 23% at day 28. Silica gel was used because it permits an accurate administration of the test compound. In the prolonged Closed Bottle test the biodegradation percentage reached 49% at day 112.

Hence, tert-butylperoxyisopropylcarbonate should be classified as inherently biodegradable. The biodegradation percentage reached at the last day of the test indicates that tert-butylperoxyisopropylcarbonate was completely mineralized.

Reference 2

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:

guideline study

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 and river water instead of an effluent/extract/mixture was used as inoculum.

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

natural water: freshwater

Details on inoculum:

River water was sampled from the Rhine near Heveadorp, The Netherlands (08-02-2018). The nearest plant (Arnhem-Zuid) treating domestic wastewater biologically was 3 km upstream. The river water was aerated for 7 days before use to reduce the endogenous respiration (van Ginkel and Stroo, 1992). River water without particles was used as inoculum. The particles were removed by sedimentation after 1 day while moderately aerating.

Duration of test (contact time):

28 d

Initial conc.:

2 mg/L

Based on:

test mat.

Initial conc.:

1.5 mg/L

Based on:

act. ingr.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

Test bottles
The test was performed in 0.30 L BOD (biological oxygen demand) bottles with glass stoppers.

Nutrients, and stocks
The river water used in the Closed Bottle test was spiked per liter of water with 8.5 mg KH2PO4, 21.75 mg K2HPO4, 33.4 mg Na2HPO4·2H2O, 22.5 mg MgSO4·7H2O, 27.5 mg CaCl2, 0.25 mg FeCl3·6H2O. Ammonium chloride was not added to the river water to prevent nitrification.
Accurate administering of the test substance was accomplished by preparing a solid stock of 3.0 mg of the test item (active ingredient with isododecane) per g of silica gel in a 50-mL serum flask. Only part of the top layer of the silica gel was brought into contact with the test substance. The serum flask was closed with a screw top and the content was mixed vigorously. Subsequently, 0.20 g of silica gel with the test substance was added to the test bottles. The resulting concentration of test substance in the bottles was 2.0 mg/L (1.5 mg/L O,O-tert-butyl isopropyl monoperoxycarbonate and 0.5 mg/L isodocecane). Next the bottles were filled with nutrient medium with inoculum and closed. Sodium acetate was added to the bottles using a stock solution of 1.0 g/L.

Test procedures
The Closed Bottle test was performed according to the study plan. The study plan was developed from ISO Test Guidelines (1994). Use was made of 10 bottles containing only river water, 10 bottles containing river water and silica gel with isododecane, 10 bottles containing river water and silica gel with test substance, 6 bottles with river water and sodium acetate. The concentrations of the O,O-tert-butyl isopropyl monoperoxycarbonate, isododecane and sodium acetate in the bottles were 1.5, 0.5 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.

Test conditions
The pH of the media was 8.0 at the start of the test. The pH of the medium at day 28 was 8.0 (test and controls). The temperature ranged from 22.6 to 22.9°C which is within the prescribed temperature range of 22 to 24°C.

Reference substance:

acetic acid, sodium salt

Test performance:

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 O,O-tert-butyl isopropyl monoperoxycarbonate 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.

The validity of the test is demonstrated by an endogenous respiration of 1.0 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 80. Finally, the validity of the test is shown by oxygen concentrations >0.5 mg/L in all bottles during the test period.

Parameter:

% degradation (O2 consumption)

Value:

78

Sampling time:

28 d

Details on results:

O,O-tert-Butyl isopropyl monoperoxycarbonate was biodegraded by 78% at day 28 in the Closed Bottle test . The time-day window concept assumes that biodegradation of a single organic compound in a ready biodegradability test is a growth-linked process which follows an S-shaped growth curve. O,O-tert-Butyl isopropyl monoperoxycarbonate is a substance consisting of two chemicals linked together by a peroxide bond. Upon hydrolysis two compounds are formed i.e. acetone and tert-butanol. The biodegradation kinetics (lag period, growth rate, and yield) of the individual hydrolysis products are not necessarily same. The time window applied as criterion to Closed Bottle tests is therefore considered not applicable OECD 2006), even though it is met. Over 60% biodegradation was achieved in a period of approximately 14 days immediately following the attainment of 10% biodegradation after 5 days, therefore fulfilled the 14-day time window (10-day time window for other OECD 301 tests) criterion for ready biodegradable compounds. O,O-tert-Butyl isopropyl monoperoxycarbonate should therefore be classified as readily biodegradable.

Results with reference substance:

The biodegradation percentage of the reference compound, sodium acetate, at day 14 was 80.

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

O,O-tert-Butyl isopropyl monoperoxycarbonate should be classified as readily biodegradable.

Executive summary:

In order to assess the biotic degradation of O,O-tert-Butyl isopropyl monoperoxycarbonate, 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.

O,O-tert-Butyl isopropyl monoperoxycarbonatedid not cause a reduction in the endogenous respiration at day 7. The test substance is therefore considered to be non-inhibitory to the inoculum.O,O-tert-Butyl isopropyl monoperoxycarbonatewas biodegraded by 78% at day 28 in the OECD 301 Closed Bottle test. The substance should therefore be classified as readily biodegradable.

The test is valid as shown by an endogenous respiration of 1.0 mg/L and by the complete degradation of the reference compound, sodium acetate. Sodium acetate was degraded by 80% 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

In order to assess the biotic degradation of O,O-tert-Butyl isopropyl monoperoxycarbonate, 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.

O,O-tert-Butyl isopropyl monoperoxycarbonatedid not cause a reduction in the endogenous respiration at day 7. The test substance is therefore considered to be non-inhibitory to the inoculum.O,O-tert-Butyl isopropyl monoperoxycarbonatewas biodegraded by 78% at day 28 in the OECD 301 Closed Bottle test. The substance should therefore be classified as readily biodegradable.

The test is valid as shown by an endogenous respiration of 1.0 mg/L and by the complete degradation of the reference compound, sodium acetate. Sodium acetate was degraded by 80% 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.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable