2-phenoxyethyl isobutyrate

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:

25 August 1992 to 22 September 1992

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: A GLP study conducted to standardised guidelines with incomplete reporting but with insufficient information to assess the quality of the presented results.

Qualifier:

according to guideline

Guideline:

EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)

Deviations:

no

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge (adaptation not specified)

Details on inoculum:

- Source of inoculum/activated sludge: mixed population of aquatic microorganisms (activated sludge). Laboratory activated sludge plant is operated with municipal wastewater (Wupperverband).

Duration of test (contact time):

29 d

Initial conc.:

29 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST SYSTEM
- Method used to create aerobic conditions: Samples were aerated with carbon dioxide free air.
- Details of trap for CO2: Carbon dioxide was trapped in barium or sodium hydroxide, which was measured by titration of the residual hydroxide or as inorganic carbon.

Reference substance:

aniline

Parameter:

% degradation (CO2 evolution)

Value:

64

Sampling time:

29 d

Results with reference substance:

In the attempt with aniline reference substance after 29 days, a degradation of 67% was achieved.

Table 1: Results

Time (days)	Blank value CO2 (mg/L)	Test
		CO2 (mg/L)	Cumulative Net CO2 (mg/L)	Degradation (%)
2	3.74	3.14	-0.60	0
3	1.85	2.23	-0.22	0
6	8.76	37.10	28.12	38
7	1.65	2.29	28.77	39
8	1.96	10.26	37.07	50
9	2.29	7.98	42.76	58
10	2.48	5.97	46.25	63
13	8.34	8.39	46.30	63
15	2.75	3.44	46.99	64
17	2.15	3.03	47.87	65
20	4.05	5.06	48.88	66
24	5.06	5.34	49.16	67
27	5.20	4.07	48.03	65
29	4.71	3.50	46.82	64

Amount of CO2 generated during complete oxidation of the test material quantity used (ThCO₂): 2.54 mg CO₂/mg

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

Under the conditions of the test, biodegradation was reported to be 64% during the test period of 29 days. The test material is therefore considered to be readily biodegradable.

Executive summary:

The ready biodegradability of the test material was determined in accordance with standardised guidelines OECD 301 B and EU Method C.4-C in a carbon dioxide evolution test. The degradation rate of the test material during the test period of 29 days was reported to be 64%, and therefore the test material is considered to be readily biodegradable.

Reference 2

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

13 October 1994 to 14 November 1994

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Study conducted in compliance with agreed protocols, with no or minor deviations from standard test guidelines and/or minor methodological deficiencies, which do not affect the quality of the relevant results. The study report was conclusive, done to a valid guidelines and the study was conducted under GLP conditions.

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)

Deviations:

no

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: Fresh activated sludge from a biological waste water treatment plant treating predominantly domestic sewage (City of Geneva, Aïre) was used.
- Preparation of inoculum for exposure: The sludge was collected in the morning, washed three times in mineral medium (by centrifuging at 1000 g for 10 minutes, the supernatant was discarded and the mineral medium re-suspended) and kept aerobic until it was used on the same day.

Duration of test (contact time):

28 d

Initial conc.:

100 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium:
The following stock solutions were prepared:
Solution A: KH2PO4 (8.5 g), K2HPO4 (21.75 g), Na2HPO4.2H2O (33.4 g), NH4Cl (0.5 g) - dissolved in water and made up to 1 litre.
Solution B: CaCl2 (27.5 g) - dissolved in water and made up to 1 litre.
Solution C: MgSO4.7H2O (22.5 g) - dissolved in water and made up to 1 litre.
Solution D: FeCl3.6H2O (0.25 g), HCL Concentrated (one drop) - dissolved in water and made up to 1 litre.
Mineral medium: prepared by mixing 50 mL of Solution A and 2000 mL deionised water, adding 5 mL of each of solutions B, C and D and making up to 5 litres with deionised water.
- Water: The water used during the study was deionised water containing less than 10 mg/L dissolved organic carbon.
- Test temperature: 22ºC
- pH: 7.4 ± 0.2
- pH adjusted: if necessary, with phosphoric acid or potassium hydroxide.
- Suspended solids concentration: 30 mg/L (dry weight), corresponding to 3.49 mL of sludge.
- Determination of the dry weight of suspended solids: The dry weight of suspended solids was determined by taking two 50 mL samples of the homogenised sludge, evaporating water on a steam bath, drying in an oven at 105 – 110ºC for two hours and weighing the residue.


TEST SYSTEM
- Culturing apparatus: 250 mL volumetric flasks.
- Volume of suspended sludge:
- Number of culture flasks/concentration: 2.
- Measuring equipment: Respirometer.
- Test performed in closed vessels due to significant volatility of test substance: closed system.

- Details of trap for CO2 and volatile organics if used: Evolved carbon dioxide was absorbed in 2 g of soda lime pellets.

SAMPLING
- Sampling frequency: Oxygen consumption and temperature was measured daily. Stirring was also checked daily. pH was measured at the end of the incubation period.

CONTROL AND BLANK SYSTEM
- Inoculum blank: Duplicate inoculum blanks was run in parallel.
- Toxicity control: Duplicate flask containing mineral medium and inoculums were prepared with either the test material (100 mg/L) and aniline (100 mg/L) or just aniline (100 mg/L). Respiration rates were measured as for the test flasks and compared. The test material was considered to inhibit the inoculums if the respiration rate was lower in flask containing the test material.

STATISTICAL METHODS: oxygen uptakes, as read on the respirometer, were corrected by deducing the basic oxygen uptake of sludge and proportionally to account for the differences between actual and nominal concentrations of test and reference materials.

Reference substance:

aniline

Remarks:

100 mg/L

Parameter:

% degradation (O2 consumption)

Value:

98

Sampling time:

28 d

Parameter:

% degradation (O2 consumption)

Value:

90

Sampling time:

10 d

Details on results:

No toxic effects were observed in the micro-organisms exposed to the test material at 100 mg/L.

Results with reference substance:

Degradation of aniline exceeded 40% after 7 days and 65% after 14 days; the activity of the inoculum was therefore verified and the test was considered valid.

Table 2: Biodegradability of the Test Material

	Flask	Calculation	Days
			1	7	11	14	21	28
BOD Sludge	1	B1	0.0	6.0	6.0	6.0	6.0	6.0
	2	B2	1.0	15.0	19.0	20.0	24.0	25.0
	mean	B	0.5	10.5	12.5	13.0	15.0	15.5
BOD Test Material	1	C1	32.2	202.1	219.2	224.2	234.2	241.3
	2	C2	32.3	181.5	206.7	212.8	221.8	225.9
	1^stflask correction	C1-B	31.7	191.6	206.7	211.2	219.2	225.8
	2^ndflask correction	C2-B	31.8	171.0	194.2	199.8	206.8	210.4
% Degradation	1	D1	14	86	93	95	98	101
	2	D2	14	77	87	90	93	94
	mean	D	14	81	90	92	96	98

ThOD = 2.23 mg O₂/mg

Table 3: Biodegradability of Reference Substance

	Flask	Calculation	Days
			1	7	11	14	21	28
BOD Sludge	1	B1	4.0	6.0	6.0	6.0	6.0	6.0
	2	B2	9.0	14.0	18.0	20.0	24.0	25.0
	mean	B	6.5	10.0	12.0	13.0	15.0	15.5
BOD Reference Substance	1	C1	127.7	169.8	179.4	180.4	180.5	180.5
	2	C2	21.8	159.6	185.8	193.3	203.7	211.1
	1^stflask correction	C1-B	121.2	159.8	167.4	167.4	165.5	165.0
	2^ndflask correction	C2-B	15.3	149.6	173.8	180.3	188.7	195.6
% Degradation	1	D1	50	66	69	69	69	68
	2	D2	6	62	72	75	78	81
	mean	D	28	64	71	72	73	75

ThOD = 2.41 mg O₂/mg

Calculations:

B = (B1 + B2)/2

D1 = 100* (C1 – B)/ThOD* [S]

D2 = 100* (C2 – B)/ThOD* [S]

D = (D1 + D2)/2

Where: [S] = initial test material or reference substance concentration.

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

Under the conditions of the test, the test material underwent 98% biodegradation after 28 days of which 90% were within the 10-day window. This means that the test material is considered to be readily biodegradable.

Executive summary:

The ready biodegradability of the test material was determined in a GLP study conducted in accordance with the standardised guidelines OECD 301 F by the measurement of oxygen consumption of the micro-organisms in the inoculum over a 28 day period. Oxygen consumption indicated that the test material underwent 98% biodegradation after 28 days under the conditions of the test, the biodegradation rate being 90% at the end of the 10-day window, and therefore the test material is considered to be readily biodegradable.

The results obtained from the toxicity control bottles showed that the test material did not inhibit the biodegradation of the inoculum.

Description of key information

Readily biodegradable (98% degradation after 28 days), OECD 301 F, Rudio (1994).

Readily biodegradable (64% degradation after 29 days), OECD 301 B, EU Method C.4 - C, Müller (1993).

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Additional information

The key study (Rudio, 1994) determined the biodegradability of the test material in line with GLP and the standardised guideline OECD 301 F. Measuring the oxygen consumption of the micro-organisms in the inoculum treated with the test material at 100 mg/L over 28 days. Under the conditions of the test, oxygen consumption indicated that the test material underwent 98% biodegradation after 28 days, where 90% degradation was achieved at the end of the 10-day window. The test material was therefore, considered to be readily biodegradable. The results obtained from the toxicity control showed that the test material did not inhibit the biodegradation of the inoculum. The study was performed to a high standard, and accordingly was assigned a reliability score of 1 in line with the principles for assessing data quality as defined in Klimisch (1997).

A further study (Müller, 1993) was provided as supporting data, where the biodegradability of the test material was determined in accordance with standardised guidelines OECD 301 B and EU Method C.4 -C in a carbon dioxide evolution test. The degradation rate of the test material during the test period of 29 days was reported to be 64%, and therefore the test material is considered to be readily biodegradable. This study was conducted to standardise guidelines and in accordance with GLP, however incomplete reporting meant that the study was assigned a reliability score of 2 in line with Klimisch (1997).