Phosphonic acid, monoethyl ester, sodium salt (1:1)

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:

key study

Study period:

23 Feb - 23 Mar 2001

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)

Qualifier:

according to guideline

Guideline:

EU Method C.4-E (Determination of the "Ready" Biodegradability - Closed Bottle Test)

GLP compliance:

yes (incl. QA statement)

Remarks:

Hessisches Ministerium für Umwelt, Landwirtschaft und Forsten

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Sewage plant GroB-Zimmern, Germany
- 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 resuspended 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 4 g dry material per litre were mixed with test water and then aerated until use. Before use the sludge was filtered through cotton wool.

Duration of test (contact time):

28 d

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Test temperature: 21 - 22 °C
- pH: 7.6 (measured at start of the test)
- Oxygen Concentration of Test Water: 8.8 - 9.0 mg O2/L (measured at the start of the test)
- Continuous darkness: yes
- Other: Reconstituted water was used

TEST SYSTEM
- Culturing apparatus: Karlsruher flasks of 250 mL volume with glass stoppers
- Number of culture flasks/concentration: 2
- Measuring equipment: The oxygen concentrations were electrochemically measured in an airtight system with an O2-electrode (WTW Oxi 340, Wissenschaftlich Technische Werkstatten GmbH, Weilheim, Germany) under constant stirring
- Test performed in closed vessels: yes

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

Reference substance:

aniline

Parameter:

% degradation (O2 consumption)

Value:

-1

Sampling time:

28 d

Remarks on result:

other: based on active ingredient sodium ethyl phosphonate of the test item

Results with reference substance:

The reference item aniline was sufficiently degraded to 65% after 14 days, and to 94% after 28 days of incubation.

Biodegradation of the toxicity control:

In the toxicity control containing both, the test item and the reference item aniline, 37% biodegradation was noted within 14 days

and 50% biodegradation after 28 days of incubation. Thus, the test item can be assumed to be not inhibitory on the activated sludge microorganisms.

Table 1: Dissolved oxygen concentrations at different time intervals during the exposure period of 28 days

Treatment	Conc. of a.i. (mg/L)	Flask No.	Mg O2 after n days of exposure
			0	3	5	7	12	14	21	28
Test item	7.09	1a	8.6	8.4	8.4	8.2	8.1	8.1	8.1	7.8
		1b	8.6	8.5	8.4	8.2	8.1	8.1	8.0	7.9
		Mean	8.6	8.45	8.4	8.2	8.1	8.1	8.05	7.85
Procedure control	2.1	2a	8.6	8.5	8.5	7.6	5.0	4.9	3.8	3.0
		2b	8.6	8.5	8.5	7.9	5.1	4.9	4.5	3.1
		Mean	8.6	8.5	8.5	7.75	5.05	4.9	4.15	3.05
Inoculum control	-	3a	8.6	8.5	8.5	8.4	8.3	8.2	8.0	7.8
		3b	8.6	8.5	8.5	8.3	8.2	8.2	8.3	7.8
		Mean	8.6	8.5	8.5	8.35	8.25	8.2	8.15	7.8
Toxicity control	TI: 7.10, aniline: 2.02	4a	8.6	n.d.	n.d.	5.1	n.d.	4.3	4.1	2.2
		4b	8.6	n.d.	n.d.	5.3	n.d.	4.1	3.6	2.6
		Mean	8.6	n.d.	n.d.	5.2	n.d.	4.2	3.85	2.4

TI: test item (active ingredient), n.d.: not determined

Table 2: Oxygen depletion at different time intervals during the exposure period of 28 days

Treatment	Conc. of a.i. (mg/L)	Flask No.	O2 depletion (mg/L) after n days of exposure
			3	5	7	12	14	21	28
Test item	7.09	1a	0.10	0.10	0.15	0.15	0.10	0.05	0.00
		1b	0.00	0.10	0.15	0.15	0.10	0.15	-0.10
Procedure control	2.1	2a	0.00	0.00	0.75	3.25	3.30	4.35	4.80
		2b	0.00	0.00	0.45	3.15	3.30	3.65	4.70
Inoculum control	-	Mean	0.10	0.10	0.25	0.35	0.40	0.45	0.80
Toxicity control	TI: 7.10, aniline: 2.02	4a	n.d.	n.d.	3.25	n.d.	3.90	4.05	5.60
		4b	n.d.	n.d.	3.05	n.d.	4.10	4.55	5.20

TI: test item (active ingredient), n.d.: not determined

Table 3: Percentage biodegradation at different time intervals during the exposure period of 28 days

Treatment	Conc. of a.i. (mg/L)	Flask No.	% biodegradation after n days of exposure
			3	5	7	12	14	21	28
Test item	7.09	1a	2	2	2	2	2	1	0
		1b	0	2	2	2	2	2	-2
		Mean	1	2	2	2	2	2	-1
Procedure control (aniline)	2.1	2a	0	0	15	64	65	86	95
		2b	0	0	9	62	65	72	93
		Mean	0	0	12	63	65	79	94
Toxicity control	TI: 7.10, aniline: 2.02	4a	n.d.	n.d.	30	n.d.	36	37	51
		4b	n.d.	n.d.	28	n.d.	38	42	48
		Mean	n.d.	n.d.	29	n.d.	37	39	50

TI: test item (active ingredient), n.d.: not determined

Table 4: Validity criteria

Criterion from the guideline	Outcome	Validity criterion fulfilled
Difference of extremes of replicate values of the removal of the test chemical at the plateau, at the end of the test or at the end of the 10-d window, as appropriate, is less than 20%.	At the end the test item showed 0% and -2% degradation, since a negative degradation is not possible, the latter replicate also presents 0% degradation. Thus the difference between replicates was 0%.	Yes
Percentage degradation of the reference compound reached the pass level by day 14 (≥ 60%).	Degradation of Aniline was 65% at day 14	Yes
The toxicity control should degrade to at least 35% (based on DOC) or at least 25% (based on ThOD or ThCO2) within 14 d.	Toxicity control degraded to 37% at day 14	Yes
Oxygen depletion in the inoculum blank should not exceed 1.5 mg dissolved oxygen/L after 28 days.	Oxygen depletion was 0.8 mg O2/L after 28 days	Yes
The residual concentration of oxygen in the test bottles should not fall below 0.5 mg/L at any time.	The residual concentration was not below 0.5 mg/L	Yes

Validity criteria fulfilled:

yes

Remarks:

see Table 4 in 'any other results incl. tables'

Interpretation of results:

under test conditions no biodegradation observed

Reference 2

Endpoint:

biodegradation in water: inherent biodegradability

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

14 Aug - 18 Sep 2014

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

OECD Guideline 302 C (Inherent Biodegradability: Modified MITI Test (II))

Version / remarks:

1981

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

other: mixture of activated sludge, surface soil and surface water

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Activated sludge, surface soil and surface water were sampled from ten sites distributed in four districts throughout Nanjing city, such as Chengdong, Chengbei, Jiangxinzhou and Jiangning.
- Method of cultivation: 1 L of the sludge, soil and water were collected and mixed thoroughly together. After removing floating matter, the mixture was allowed to stand and then the supernatant is filtrated through filter paper. After that the filtrate was adjusted the supernatant to pH 7.0 with sodium hydroxide or phosphoric acid. Finally an appropriate volume of the filtered supernatant was transferred to a fill-and-draw activated sludge vessel and aerated for about 23.5 h. Batch No.: 120140604.
Thirty minutes after stopping the aeration, about one third of the whole volume of supernatant was discarded. Then an equal volume of the solution (pH 7.0) containing 0.1% each of glucose, peptone and potassium orthophosphate was added into the settled material and aerated again. This procedure was repeated once per day during one month.
- Preparation of inoculum for exposure: Before use the mixture was allowed to stand, and the supernatant was removed. A small quantity of sludge was taken to be centrifuged (10000 rpm, for 10 min) and then weighed. Then the sludge was dried in the oven and weighed again in order to calculate the content of dry sludge was 10%. At last 10 g of centrifuged sludge was diluted 1 L with basal culture medium (BSM) to get activated sludge suspension with a concentration of 1000 mg/L (dry basis) Batch No.: 120140814.
- Concentration of sludge: 100 mg/L

Duration of test (contact time):

28 d

Initial conc.:

101.5 mg/L

Based on:

test mat.

Remarks:

concentration presents mean of 4 replicates

Parameter followed for biodegradation estimation:

test mat. analysis

Parameter followed for biodegradation estimation:

O2 consumption

Remarks:

based on BOD and ThOD

Details on study design:

TEST CONDITIONS
- Composition of medium: Based Salt Medium (BSM)/mineral medium was prepared by adding 3 mL of each of the following stock solutions prepared in pre-aerated deionized water to 1 litre of pure water:
- Stock solution A
KH2P04 (potassium dihydrogen phosphate) 8.50 g/L
K2HP04 (dipotassium hydrogen phosphate) 21.75 g/L
Na2HP04. 12H20 (disodium phosphate dodecahydrate) 44.60 g/L
NH4Cl (ammonium chloride) 1.70 g/L
The pH of this solution was 7.22
- Stock solution B
CaCl2 (calcium chloride) 27.50 g/L
- Stock solution C
MgS04.7H20 (magnesium sulphate heptahydrate) 22.50 g/L
- Stock solution D
FeCl3.6H20 (iron (III) chloride hexahydrate) 0.25 g/L
- Test temperature: 25±1 °C
- pH: 6.32 - 7.41
- pH adjusted: no
- Suspended solids concentration: 100 mg/L
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: 500 mL BOD bottles
- Number of culture flasks/concentration: 3
- Method used to create aerobic conditions: stir vigorously with mechanical stirrer
- Measuring equipment: BOD meter (OM3100, Ohkura, Japan)

SAMPLING
- Sampling frequency: daily

CONTROL AND BLANK SYSTEM
- Inoculum blank: 1
- Abiotic sterile control: 1
- Positive control: 1

Reference substance:

benzoic acid, sodium salt

Parameter:

% degradation (test mat. analysis)

Value:

> 99.9

Sampling time:

28 d

Remarks on result:

other: result based on residue analysis in 3 replicates

Parameter:

% degradation (O2 consumption)

Value:

86.9

Sampling time:

28 d

Remarks on result:

other: result based on BOD measurements of 3 replicates

Results with reference substance:

the level of biodegradation of the reference substance sodium benzoate was 83.5% after 7 days (> 40%), and 87.7% after 14 days (> 65%)

Table 1. Analytical results and degradation of the test substance

Sample	Time (d)	Bottle	Conc. of test substance (mg/L)	Degradation (%)
“abiotic”	0	-	99.8*	-
	28	1	101	-
“blank”	28	6	< LOD	-
“test”	28	2	0.084	99.9
		3	0.006	>99.9
		4	0.006	>99.9
		Mean	0.032	>99.9

*Concentration of Fosetyl-Na in “abiotic” at day 0 was from the results of recovery sample of 100 mg/L

 

Table 2. Results of BOD measurements

Time (d)	BOD (mg/L)
	Abiotic	Test substance			Positive control	Blank control
	Bottle #1	Bottle #2	Bottle #3	Bottle #4	Bottle #5	Bottle #6
0	0	0	0	0	0	0
1	0	13.2	14.0	16.4	19.3	10.6
2	0	21.3	20.5	22.0	58.8	11.6
3	0	26.8	28.3	30.9	73.0	13.8
4	0	32.2	35.6	36.5	77.7	14.9
5	0	40.1	43.9	42.2	80.2	14.8
6	0	48.5	49.7	48.9	82.0	15.4
7	0	51.3	53.6	53.5	86.6	16.9
8	0	53.2	61.0	58.8	89.1	18.0
9	0	55.8	62.5	62.1	91.5	19.4
10	0	57.9	63.2	65.3	92.4	19.9
11	0	58.3	63.7	66.4	93.0	20.1
12	0	58.9	64.9	67.0	93.9	20.7
13	0	59.2	65.7	68.2	94.3	21.2
14	0	61.6	66.1	68.5	94.6	21.4
15	0	64.0	67.4	69.3	95.7	22.5
16	0	66.4	68.3	70.2	96.1	22.8
17	0	70.4	69.1	70.8	96.7	23.3
18	0	72.0	69.6	71.4	97.0	23.5
19	0	72.6	69.9	71.6	97.3	23.7
20	0	73.7	71.0	71.9	97.7	24.0
21	0	74.3	72.4	72.8	98.0	24.3
22	0	74.9	72.8	74.8	99.2	24.9
23	0	75.5	73.4	75.0	99.7	25.4
24	0	75.9	74.8	77.4	99.9	25.5
25	0	76.8	75.6	78.0	101	26.4
26	0	77.5	76.3	78.2	101	26.6
27	0	78.3	77.2	78.8	102	27.1
28	0	79.5	77.8	79.4	103	27.9

 

 

 Table 3. Results of biodegradation based on BOD measurements

Time (d)	Biodegradation after deduct the abiotic (%)
	Test substance				Positive control
	Bottle #2	Bottle #3	Bottle #4	Mean	Bottle #5
0	0	0	0	0	0
1	4.7	6.2	12.4	9.64	10.5
2	17.4	16.0	19.7	18.7	56.1
3	23.6	26.3	30.5	27.3	70.9
4	31.2	37.4	37.6	35.2	75.2
5	45.7	52.5	46.3	46.4	78.3
6	59.8	62.0	55.7	56.3	79.8
7	62.1	66.2	60.9	60.2	83.5
8	63.6	77.7	67.6	66.3	85.2
9	65.7	77.8	70.9	68.4	86.3
10	68.5	78.1	75.1	70.8	86.7
11	69.0	78.7	76.6	71.6	87.3
12	69.0	79.8	76.8	72.1	87.6
13	68.7	80.4	78.0	72.7	87.6
14	72.7	80.8	78.2	74.0	87.7
15	74.9	81.0	78.1	75.0	87.7
16	78.8	82.2	79.1	76.8	87.9
17	85.1	82.7	79.5	78.9	88.0
18	87.6	83.3	80.1	80.1	88.1
19	88.3	83.5	80.2	80.4	88.2
20	89.8	84.9	80.3	81.3	88.3
21	90.2	86.8	81.3	82.4	88.2
22	90.3	86.5	83.6	83.2	89.0
23	90.4	86.6	83.4	83.4	89.0
24	91.0	89.0	86.8	85.3	89.1
25	91.1	88.9	86.7	85.5	89.1
26	91.9	89.7	86.8	86.0	89.3
27	92.4	90.5	87.1	86.6	89.6
28	93.2	90.1	87.1	86.9	89.6

 

Table 4. Validity criteria OECD 302C

Criterion from the guideline	Outcome	Validity criterion fulfilled
The test is considered to be valid, if biodegradation of the reference substance reached > 40% after 7 days and 65% after 14 days.	Sodium benzoate was 83.5% after 7 days (> 40%), and 87.7% after 14 days (> 65%),	Yes
The recovery rate of residual amount of the test compound in the “abiotic” test should be more than 10%.	Recovery was 99.8% and 101%	Yes

 

 

 

Validity criteria fulfilled:

yes

Remarks:

see Table 4 in 'any other information on results incl. tables'

Interpretation of results:

inherently biodegradable, fulfilling specific criteria

Description of key information

- Not readily biodegradable (-1% degradation based on a.i. Fosetyl-Sodium after 28 days; OECD 301D, closed bottle test)

- Inherently biodegradable (86.9% biodegradation based on BOD and > 99.9% biodegradation based on residue analysis after 28 days; OECD 302 C)

Key value for chemical safety assessment

Biodegradation in water:

inherently biodegradable

Type of water:

freshwater

Additional information

A GLP study according to OECD 301D on ready biodegradability was performed with Fosetyl-Sodium (technical concentrate; 22.1%; Code: AE C529354 00 TK22 A101, containing 22.1% w/w Fosetyl-Sodium) under static conditions. The study was designed as a closed bottle test. The test item was exposed to activated sludge from the aeration tank of a domestic waste water treatment plant for 28 days. The biodegradation was followed by the oxygen uptake of the microorganisms during exposure. As a reference item aniline was tested simultaneously under the same conditions as the test item, and functioned as a procedure control.

Under the test conditions the percentage biodegradation of the active ingredient Sodium ethyl phosphonate (exposure to a concentration of 7.09 mg active ingredient) of the test item Fosetyl-Sodium; technical concentrate (Code: AE C529354 00 TK22 A101) was determined to be -1% after 28 days of incubation. The results are based on concentrations of the active ingredient sodium ethyl phosphonate (content of 22.1 % w/w in test item). The test item cannot considered to be ready biodegradable.

In a weight of evidence approach, a second GLP study is available which was performed according to OECD guideline 302 C (modified MITI test). In this study, the test item Fosetyl-Sodium with an analytical purity of 97.6% was tested for 28 days for the inherent biodegradability based on the biochemical oxygen demand (BOD) of the microorganisms in a mixture of activated sludge, surface soil and surface water sampled from 10 places in Nanjing city, China. Additionally, the biodegradation of the test substance was analytically verified by HPLC-MS/MS. The reference substance sodium benzoate was tested simultaneously under the same conditions as the test item, and functioned as a procedure control. Under the test conditions the percentage biodegradation of the test substance based on BOD measurements was 86.9% (mean of three replicates) at 28 days and based on residue analysis of the test substance, the biodegradation was > 99.9% (mean of three replicates). The biodegradation of the reference substance sodium benzoate was 89.6% after 28 days, 83.5% after 7 days (> 40%), and 87.7% after 14 days (> 65%). The analytical recovery of the test substance in the abiotic control was 99.8% and 101%. Therefore, the study was valid according to the OECD guideline 302 C and the test item Fosetyl-Sodium is regarded as inherently biodegradable.