6-Amino-5-chloro-2-cyclopyrimidine-4-carboxylic acid

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:

29 Oct - 26 Nov 2019

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:

1992

GLP compliance:

yes (incl. QA statement)

Remarks:

Ministerium für Arbeit, Integration und Soziales des Landes Nordrhein-Westfalen, Düsseldorf, Germany

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

- Source of inoculum/activated sludge: WWTP Odenthal, Germany (28 Oct 2019)
- Storage conditions: stored for one day at room temperature under continuous stirring with aeration before use
- Preparation of inoculum for exposure: washed twice by adding mineral medium and centrifuging for 10 min at 3500 rpm and 20 °C and decanting off the supernatant, aliquot of the wet sludge was dried in order to determine the wet weight/dry weight ratio of the sludge and to prepare a stock suspension (activated sludge) of 3 g dw/L, calculated amount of sludge, needed to achieve 300 mL of this stock suspension, was dissolved in mineral medium and then filled up to a defined end volume
- Concentration of sludge: 30 mg/L suspended solids
- Initial cell/biomass concentration:

Duration of test (contact time):

28 d

Initial conc.:

97.4 mg/L

Based on:

ThOD

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium: According to OECD 301
- Test temperature: 22 ± 1 °C
- pH: 7.4 - 8.1
- pH adjusted: no
- Suspended solids concentration: 30 mg/L s
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: OxiTopControl System (WTW), 250 mL, automated respirometer flasks
- Number of culture flasks/concentration: 3
- Method used to create aerobic conditions: before use, the inoculum was stored under continuous stirring with aeration
- Test performed in closed vessels due to significant volatility of test substance: yes
- Details of trap for CO2 and volatile organics if used: carbon dioxide was absorbed in sodium hydroxide

CONTROL AND BLANK SYSTEM
- Inoculum blank: 3
- Abiotic sterile control: 3
- Toxicity control: 1

Reference substance:

benzoic acid, sodium salt

Remarks:

100 mg/L

Parameter:

% degradation (O2 consumption)

Value:

4

Sampling time:

28 d

Results with reference substance:

The reference compound sodium benzoate showed 87 % degradation after 14 days.

Table 1: BOD values (mg O2/L) after n days

 

flask no.	test item			blank			blank mean	reference compound		toxicity control
	10	11	12	1	2	3		4	5	13
code*	a1	a2	a3	b1	b2	b3	bm	r1	r2	t1
time [d]
0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
1	4.3	5.7	5.7	5.7	5.7	5.7	5.7	34.2	37.0	37.0
2	8.5	8.5	7.1	8.5	8.5	8.5	8.5	78.3	76.9	81.2
3	11.4	11.4	8.5	11.4	12.8	11.4	11.9	98.3	91.2	94.0
4	12.8	12.8	11.4	11.4	12.8	12.8	12.3	130.0	125.0	128.0
5	14.2	14.2	11.4	12.8	12.8	14.2	13.3	138.0	134.0	138.0
6	14.2	14.2	12.8	12.8	14.2	14.2	13.7	144.0	140.0	144.0
7	18.5	15.7	15.7	11.4	11.4	11.4	11.4	145.0	141.0	147.0
8	21.4	18.5	15.7	12.8	12.8	14.2	13.3	150.0	144.0	150.0
9	21.4	18.5	17.1	12.8	12.8	14.2	13.3	152.0	148.0	154.0
10	22.8	18.5	17.1	14.2	14.2	14.2	14.2	155.0	150.0	155.0
11	22.8	18.5	18.5	14.2	14.2	12.8	13.7	157.0	152.0	158.0
12	22.8	19.9	19.9	14.2	14.2	14.2	14.2	158.0	155.0	160.0
13	22.8	21.4	18.5	14.2	15.7	15.7	15.2	161.0	155.0	160.0
14	22.8	19.9	18.5	12.8	14.2	14.2	13.7	161.0	157.0	161.0
15	24.2	19.9	18.5	14.2	15.7	15.7	15.2	162.0	160.0	162.0
16	24.2	21.4	18.5	15.7	15.7	15.7	15.7	164.0	162.0	162.0
17	24.2	21.4	21.4	15.7	15.7	15.7	15.7	165.0	164.0	165.0
18	25.6	21.4	21.4	15.7	15.7	15.7	15.7	167.0	165.0	165.0
19	25.6	22.8	19.9	15.7	15.7	15.7	15.7	167.0	165.0	165.0
20	24.2	21.4	21.4	15.7	15.7	15.7	15.7	167.0	167.0	167.0
21	25.6	21.4	19.9	15.7	15.7	15.7	15.7	167.0	168.0	167.0
22	25.6	22.8	22.8	15.7	17.1	15.7	16.2	168.0	170.0	168.0
23	25.6	21.4	21.4	14.2	15.7	15.7	15.2	167.0	170.0	168.0
24	25.6	22.8	22.8	17.1	17.1	17.1	17.1	170.0	170.0	168.0
25	25.6	22.8	22.8	17.1	17.1	17.1	17.1	171.0	171.0	170.0
26	27.1	22.8	22.8	17.1	17.1	17.1	17.1	171.0	171.0	170.0
27	27.1	22.8	21.4	17.1	17.1	17.1	17.1	171.0	172.0	170.0
28**	23.5	19.2	19.2	17.1	17.1	17.1	17.1	171.0	174.0	171.0

*Abbreviations according to test guideline.

**The oxygen uptake by nitrification was determined. The oxygen consumed by nitrification was 3.61 mg/L. This oxygen consumption was subtracted from the respective 28 days measurements of the test item.

Table 2: Degradation of test item

Test concentration: 100 mg/L

Theoretical oxygen demand: 0.974 mgO2/mg

 

time [d]	blank-corrected BOD (a –bm) [mg O2/L]			% degradation			% degradation mean
	a1	a2	a3	a1	a2	a3
0	0.0	0.0	0.0	0	0	0	0
1	0.0	0.0	0.0	0	0	0	0
2	0.0	0.0	0.0	0	0	0	0
3	0.0	0.0	0.0	0	0	0	0
4	0.5	0.5	0.0	0	0	0	0
5	0.9	0.9	0.0	1	1	0	1
6	0.5	0.5	0.0	0	0	0	0
7	7.1	4.3	4.3	7	4	4	5
8	8.1	5.2	2.4	8	5	2	5
9	8.1	5.2	3.8	8	5	4	6
10	8.6	4.3	2.9	9	4	3	5
11	9.1	4.8	4.8	9	5	5	6
12	8.6	5.7	5.7	9	6	6	7
13	7.6	6.2	3.3	8	6	3	6
14	9.1	6.2	4.8	9	6	5	7
15	9.0	4.7	3.3	9	5	3	6
16	8.5	5.7	2.8	9	6	3	6
17	8.5	5.7	5.7	9	6	6	7
18	9.9	5.7	5.7	10	6	6	7
19	9.9	7.1	4.2	10	7	4	7
20	8.5	5.7	5.7	9	6	6	7
21	9.9	5.7	4.2	10	6	4	7
22	9.4	6.6	6.6	10	7	7	8
23	10.4	6.2	6.2	11	6	6	8
24	8.5	5.7	5.7	9	6	6	7
25	8.5	5.7	5.7	9	6	6	7
26	10.0	5.7	5.7	10	6	6	7
27	10.0	5.7	4.3	10	6	4	7
28**	6.4	2.1	2.1	7	2	2	4

 Comments: **The oxygen uptake by nitrification was determined. The oxygen consumed by nitrification was 3.61 mg/L. This oxygen consumption was subtracted from the respective 28 days measurements of the testitem.

Table 3: Oxygen uptake bynitrification ( NO3-N-/NO2-N-determination)

	time	NO3-N concentration [mg/L]	oxygen concen- tration [mg/L]	NO2-N concentration [mg/L]	oxygen concen- tration [mg/L]
test item	0 h	< 1.00	4.57	< 0.100	0.343
test item	28 d	1.79	8.18	< 0.100	0.343
increment (oxygen uptake)	28 d		3.61		0.0
Total oxygenvalue (ON)		3.61

The BOD values of the test item after 28 days were corrected for the oxygen consumed by nitrification.

Table 4: Validity criteria for OECD 301 F

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%.	93%	yes
Percentage degradation of the reference compound reached the pass level by day 14 (≥ 60%).	87%	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.	56%	yes
The oxygen uptake of the inoculum blank is normally 20-30 mg O2/L and should not be greater than 60 mg/L in 28 days.	17.1 mg O2/L	yes

Validity criteria fulfilled:

yes

Remarks:

For further details please refer to “Any other information on results incl. tables”.

Interpretation of results:

not readily biodegradable

Description of key information

Not readily biodegradable: 4% biodegradation after 28 d (OECD 301 F).

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Type of water:

freshwater

Additional information

One GLP guideline study investigating the ready biodegradability of test substance is available. The study was conducted in accordance with OECD Guideline 301 F. A suspension of the test substance in a mineral medium was inoculated and incubated for 28 d under aerobic conditions. During this period, degradation was followed by continuous automated BOD determinations. The biodegradation of the test item was 4 % (ThOD) after 28 days. The test item failed the pass level requested in test method OECD 301 F which is a biodegradation ≥ 70 % DOC or ≥ 60 % ThOD. The test item is, therefore, considered to be not readily biodegradable. The reference compound sodium benzoate showed 87 % degradation after 14 days.