Boronic acid, (4-ethylphenyl)-

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:

2006-12-12 to 2007-02-26

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

adopted July 17,1992

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)

Version / remarks:

July 31, 1992

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: Activated sludge, microorganisms from a domestic waste water treatment plant.

- Preparation of inoculum for exposure: The activated sludge used for this study was washed by centrifugation and the supernatant liquid phase was decanted. The solid material was re-suspended in tap water and again centrifuged. This procedure was repeated twice. An aliquot of the final sludge suspension was weighed, dried and the ratio of wet sludge to its dry weight was determined. Based on this ratio, calculated aliquots of washed sludge suspension, corresponding to 1.5 g dry material per litre were mixed with test water and then aerated until use overnight.

Duration of test (contact time):

28 d

Initial conc.:

104 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium: Reconstituted Test Water
- Test temperature: 22 °C
- pH: 7.6 (measured at the Start of the test); 7.7 - 7.9 (measured at the end of the test)
- pH adjusted: no
- Aeration of dilution water: no
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: Manometric Test System with test flasks containing a volume of 500 mL
- Number of culture flasks/concentration: 2
- Measuring equipment: BSB/BOD-Sensor-System
- Test performed in closed vessels: The test flasks were closed gas-tight by a measuring head
- Test performed in open system: no

SAMPLING
- Sampling frequency: everyday of the exposure period

CONTROL AND BLANK SYSTEM
- Inoculum blank: 2
- Abiotic sterile control: 1
- Toxicity control: 1
- Procedure control: 1

Reference substance:

benzoic acid, sodium salt

Key result

Parameter:

% degradation (O2 consumption)

Value:

74

Sampling time:

28 d

Results with reference substance:

The reference item sodium benzoate was sufficiently degraded to 87 % after 14 days and to 90 % after 28 days of incubation. The percentage biodegradation of the reference item confirms the suitability of the used activated sludge inoculum.

Validity Criteria of the Study

Inoculum control: The oxygen demand of the inoculum control (medium and inoculum) was 21 mg O₂/L and thus not greater than 60 mg O₂/L within 28 days as required by the test guideline.

pH-Value: The pH-value of the test item flasks at the end of the test was within the range of pH 6.0 - 8.5 as required by the test guideline.

Reference Item: The percentage degradation of the reference item should reach the level for ready biodegradability (> 60 %) within 14 days as required by the test guideline. The reference item sodium benzoate was degraded to more than 60 % after 4 days of incubation.

Test Item: The difference of duplicate values for the degradation of the test item at the plateau, at the end of the test and at the end of the 10-day window should be less than 20 %.

The validity criterion was fulfilled.

 

Percentage Biodegradation of Test Item: The test item was degraded to 24 % (mean) after 14 days and 74 % (mean) after 28 days of incubation. The degradation rate was about 14 % (mean) on day 13 when the counting of the 10-day window began and reached 64 % (mean) at the end of the 10-day window.

Percentage Biodegradation of Reference Item Sodium Benzoate: The reference item sodium benzoate was sufficiently degraded to 87 % after 14 days and to 90 % after 28 days of incubation.

Percentage Biodegradation in the Toxicity Control: In the toxicity control containing both, the test item and the reference item, 38 % biodegradation was noted within 14 days and 48 % biodegradation was determined after 28 days of incubation. According to the test guidelines the test item can be assumed to be not inhibitory on the activated sludge microorganisms because degradation was > 25 % within 14 days.

Abiotic Control - Oxygen Demand: The oxygen demand in the abiotic control was zero. No correction of the test item degradation rates had to be done.

 

Table 1: Preparation of the Test Solutions

 

 

Treatment	Flask	Test Item mg	Reference Item^1 mg	Activated Sludge^2 mL	Test Water mL	Final Volume mL
Test item	1	25.3	—	5	239	244
	2	25.5	—	5	239	244
Inoculum Control^3	3	—	—	5	239	244
	4	—	—	5	239	244
Procedure Control^4	5	—	25,2	5	239	244
Abiotic Control	6	25.5	—	—	244	244
Toxicity Control	7	24.7	25.2	5	239	244

¹ Reference item: sodium benzoate

² Stock Suspension of 1.5 g/L on dry matter base (final concentration: 30 mg/L)

³ The inoculum control was also used for other projects which ran in parallel.

⁴ The procedure control was also used for other projects which ran in parallel.

—: Not applicable

 

Table 2: Cumulative Biochemical Oxygen Demand (mg O₂/L) in Test Flasks During the Test Period

 

Time (days)	Flask No.
	Flask No. 1	Flask No. 2	Flask No. 3	Flask No. 4	Flask No. 5	Flask No. 6	Flask No. 7
1	0	0	0	0	48.7	0	0
2	0	0	5.9	5.9	75.2	0	53.1
3	0	0	5.9	5.9	94.4	0	69.3
4	0	0	5.9	7.4	111	0	87
5	0	0	7.4	8.8	127	0	97.3
6	0	0	7.4	8.8	136	0	109
7	0	0	7.4	10.3	140	0	119
8	0	0	8.8	11.8	147	0	127
9	0	0	8.8	11.8	150	0	136
10	0	2.9	10.3	13.3	155	0	143
11	4.4	17.7	10.3	13.3	156	0	152
12	19.2	36.8	11.8	14.7	159	0	161
13	45.7	48.6	13.3	14.7	164	0	165
14	74.6	70.8	13.3	14.7	164	0	170
15	88.9	90	13.3	14.7	164	0	176
16	106	103	14.7	16.2	164	0	180
17	118	115	14.7	16.2	164	0	186
18	127	130	14.7	16.2	165	0	189
19	144	140	14.7	17.7	165	0	192
20	148	150	16.2	17.7	171	0	196
21	158	155	16.2	17.7	171	0	198
22	168	163	17.7	17.7	171	0	202
23	176	170	17.7	19.2	173	0	204
24	181	177	20.6	19.2	174	0	207
25	186	183	20.6	19.2	174	0	210
26	192	188	20.6	20.6	174	0	211
27	196	194	20.6	20.6	174	0	215
28	203	199	20.6	20.6	175	0	218

Flasks 1 and 2: Test item

Flasks 3 and 4: inoculum control

Flask 5: sodium benzoate (procedure control)

Flask 6: abiotic control

Flask 7: toxicity control

 

Table 3: Percentage Biodegradation of Test Item, of Sodium Benzoate and of the Toxicity Control

 

Time (Days)	Percentage Biodegradation^1
	Test item		Sodium benzoate	Toxicity control^2
	Flask 1 [%]	Flask 2 [%]	Flask 5 [%]	Flask 7 [%]
1	0	0	28	0
2	-2	-2	40	12
3	-2	-2	51	15
4	-3	-3	61	20
5	-3	-3	69	22
6	-3	-3	74	25
7	-4	-4	76	27
8	-4	-4	79	28
9	-4	-4	81	31
10	-5	-4	83	32
11	-3	2	84	34
12	2	10	85	36
13	13	14	87	37
14	25	23	87	38
15	31	31	87	40
16	37	36	86	40
17	42	41	86	42
18	46	47	87	42
19	53	50	87	43
20	54	54	90	44
21	58	56	90	44
22	62	59	89	45
23	65	62	90	45
24	66	64	90	46
25	68	66	90	46
26	70	68	89	46
27	72	71	89	47
28	75	73	90	48

¹ based on ThOD_NH4

ThOD_NH4 of the test item: 2.347 mg/mg

ThOD_NH4 / ThOD_NO3 of sodium benzoate: 1.666 mg/mg

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

Under the test conditions of the OECD TG 301 F, the test item can be considered to be readily biodegradable within the 10-day window.

Executive summary:

The ready biodegradability of the test item in a Manometric Respirometry Test according to OECD TG 301 F and EU Method C.4-D was determined with aerobic activated sludge from a domestic wastewater treatment plant for 28 days under GLP. The biodegradation was followed by the oxygen uptake of the microorganisms during exposure. As a reference item, sodium benzoate was tested simultaneously under the same conditions as the test item, and functioned as a procedure control. Degradation rate of the test item calculated by the oxygen consumption of the aerobic activated sludge microorganisms after 28 days of incubation. The test item was tested at a concentration of 104 mg/L in duplicate, corresponding to about 244 mg/L based on ThOD of 2.347 mg O₂/mg test item. The oxygen concentration was measured using a BSB/BOD-Sensor-System and the test flasks were closed gas-tight by a measuring head. Since no nitrogen is incorporated into the molecule, nitrification was not considered. The validity criterion was fulfilled. The reference item sodium benzoate was sufficiently degraded to 87 % after 14 days and to 90 % after 28 days of incubation, thus confirming the suitability of the aerobic activated sludge inoculum used. In the toxicity control containing both the test item and the reference item sodium benzoate, 38 % biodegradation was noted within 14 days and 48 % biodegradation after 28 days of incubation. According to the test guidelines, the test item can be assumed to be not inhibitory to the aerobic activated sludge microorganisms because degradation was > 25 % within 14 days. The test item was degraded to a mean of 24 % after 14 days and a mean of 74 % after 28 days of incubation. The degradation rate was about 14 % (mean) on day 13 when the counting of the 10-day window began and reached 64 % (mean) at the end of the 10-day window, thus, the 10-day window criterion was passed. Therefore, according to the test guidelines, the test item is considered to be readily biodegradable within the 10-day window.

Description of key information

Under the test conditions of the OECD TG 301 F, the test item can be considered to be readily biodegradable within the 10-day window (reference 5.2.1-1).

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Type of water:

freshwater

Additional information

The ready Biodegradability of the test item in a Manometric Respirometry Test according to OECD TG 301 F and EU Method C.4-D was determined with aerobic activated sludge from a domestic wastewater treatment plant for 28 days under GLP. The biodegradation was followed by the oxygen uptake of the microorganisms during exposure. As a reference item, sodium benzoate was tested simultaneously under the same conditions as the test item, and functioned as a procedure control. Degradation rate of the test item calculated by the oxygen consumption of the aerobic activated sludge microorganisms after 28 days of incubation. The test item was tested at a concentration of 104 mg/L in duplicate, corresponding to about 244 mg/L based on ThOD of 2.347 mg O₂/mg test item. The oxygen concentration was measured using a BSB/BOD-Sensor-System and the test flasks were closed gas-tight by a measuring head. Since no nitrogen is incorporated into the molecule, nitrification was not considered. The validity criterion was fulfilled. The reference item sodium benzoate was sufficiently degraded to 87 % after 14 days and to 90 % after 28 days of incubation, thus confirming the suitability of the aerobic activated sludge inoculum used. In the toxicity control containing both the test item and the reference item sodium benzoate, 38 % biodegradation was noted within 14 days and 48 % biodegradation after 28 days of incubation. According to the test guidelines, the test item can be assumed to be not inhibitory to the aerobic activated sludge microorganisms because degradation was > 25 % within 14 days. The test item was degraded to a mean of 24 % after 14 days and a mean of 74 % after 28 days of incubation. The degradation rate was about 14 % (mean) on day 13 when the counting of the 10-day window began and reached 64 % (mean) at the end of the 10-day window, thus, the 10-day window criterion was passed. Therefore, according to the test guidelines, the test item is considered to be readily biodegradable within the 10-day window.