6-hydroxy-1H-pyrimidin-4-one

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:

1995-11-08 to 1996-01-04

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Study performed according to guideline and under GLP without deviations.

Qualifier:

according to guideline

Guideline:

EU Method C.4-A (Determination of the "Ready" Biodegradability - Dissolved Organic Carbon (DOC) Die-Away Test)

Deviations:

no

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Sewage treatment plant Marl-Ost, Germany
- Storage length: < 1d
- Concentration of sludge: suspended solids: 24.2 mg/L, dry weight: 4.0 g/L

Duration of test (contact time):

28 d

Initial conc.:

ca. 17.5 mg/L

Based on:

DOC

Parameter followed for biodegradation estimation:

DOC removal

Details on study design:

TEST CONDITIONS
- Composition of medium: 85 mg/L KH2PO4, 217.5 mg/L K2HPO4, 334 mg/L Na2HPO4*2H2O, 5 mg/L (NH4)Cl, 22.5 mg/L MgSO4*7H2O, 27.5 mg/L CaCl2, 0.25 mg/L FeCl3*6H2O (medium compliant with EU Method C.4 and OECD Guideline 301)
- Test temperature: 21.5-22.0°C
- pH: 7.3-7.4
- pH adjusted: no

TEST SYSTEM
- Culturing apparatus: 2L Erlenmeyer flasks
- Number of culture flasks/concentration: 2
- Measuring equipment: DOC analyzer (Shimadzu)
- Test performed in closed vessels: yes; vessels were loosley closed by aluminium foil

SAMPLING
- Sampling frequency: at 0 and 3 hours, and at days 7, 14, 21, 27, and 28.
- Sampling method: Samples were acidified and degassed to remove inorganic carbon and subsequently centrifuged

CONTROL AND BLANK SYSTEM
- Inoculum blank: 2 flasks with inoculum but without test item
- Positive control: 2 flasks with positive control substance (sodium benzoate)

Reference substance:

benzoic acid, sodium salt

Parameter:

% degradation (DOC removal)

Value:

10

Sampling time:

7 d

Parameter:

% degradation (DOC removal)

Value:

31

Sampling time:

14 d

Parameter:

% degradation (DOC removal)

Value:

67

Sampling time:

21 d

Parameter:

% degradation (DOC removal)

Value:

75

Sampling time:

27 d

Parameter:

% degradation (DOC removal)

Value:

78

Sampling time:

28 d

Details on results:

Degradation of the test item was 78% within 28 days.
The pass level for 70% degradation within 10 days was not reached, as the duration from 10% degradation to 70% degradation was 16 days (test day 7 to 23).

The reference substance sodium benzoate showed 100% degradation within 14 days.

Table 1: Degradation of the test item 4.6-dihydroxypyrimidine in the DOC-Die-away test. Results are means of 2 determinations per flask.

Test	flask	DOC concentration in [mg/L]
		at 0h	at 3h	at 7d	at 14 d	at 21d	at 27d	at 28d
Test item	1	17.17	16.79	15.30	12.62	6.51	4.65	4.65
	2	17.82	16.91	15.50	10.91	5.59	3.90	3.70
Blank	1	0.54	0.54	0.68	0.36	0.74	0.38	0.75
	2	0.24	0.26	0.48	0.39	0.61	0.10	0.29
	Mean	0.39	0.40	0.58	0.38	0.68	0.24	0.52

 

Table 2: Degradation of the test item 4.6-dihydroxypyrimidine in the DOC-Die-away test: % degradation

flask	% DOC removal
	at 0h	at 3h	at 7d	at 14 d	at 21d	at 27d	at 28d
1	0.00	0.00	10.19	25.32	64.43	73.09	74.80
2	0.00	0.00	9.63	36.22	70.26	77.83	80.74
Mean	0.00	0.00	9.91	30.77	67.35	75.46	77.77
Rounded	0	0	10	31	67	75	78

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable, but failing 10-day window

Conclusions:

The test item 4,6-dihydroxypyrimidine (CAS 1193-24-4) showed 78% degradation over a period of 28 days in the DOC die away test according to EU Method C.4-A. The pass level of 70% degradation within a 10d period was not reached.

Executive summary:

The ready biodegradability of 4,6-dihydroxypyrimidine (CAS 1193-24-4) was assessed using the DOC-die-away test according to EU Method C.4 -A without deviations under GLP. Briefly, the test item was incubated for 28 days in the dark with a suspension of activated sludge from a domestic sewage treatment plant and DOC concentration was quantified weekly. Negative (activated sludge without test item) and positive (sodium benzoate with activated sludge) controls were run in parallel. The test item 4,6-dihadroxypyrimidine showed 78% DOC removal (degradation) within the test period of 28 days. The pass level of 70% degradation within a 10d period was not reached. The reference substance sodium benzoate showed 100% degradation within 14 days, proving the suitability of the test system. Taking together, 4.6-dihydroxypyrimidine is biodegradable but as the requested 10d window was failed, a classification as "readily biodegradable" is not indicated.

Description of key information

78% DOC removal (degradation) in 28 days, 70% degradation within a 10d period was not reached, EU Method C.4 (DOC Die-Away test), Diefenbach 1996

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable but failing 10-day window

Type of water:

freshwater

Additional information

The substance is biodegradable but as the requested 10d window was failed, a classification as "readily biodegradable" is not indicated. The results are sufficiently detailed and unambiguous as to be reliable for risk assessment, classification and labeling.