4-(2-chlorophenyl)-N-cyclohexyl-N-ethyl-5-oxo-4,5-dihydro-1H-tetrazole-1-carboxamide

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:

16 Dec 1998 - 3 Jan 1999

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study without detailed documentation

Qualifier:

according to guideline

Guideline:

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

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: Secondary effluent of a domestic sewage treatment plant (Odenthal).
- Preparation of inoculum for exposure: Aeration for 5 days.
- Pretreatment: Separation of coarse particles by filtration.
- Initial cell/biomass concentration: 5 mL/L

Duration of test (contact time):

28 d

Initial conc.:

4.1 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium: mineral medium
- Test temperature: 20 ± 1 °C

TEST SYSTEM
- Number of culture flasks/concentration: 2

SAMPLING
- Sampling frequency: Dissolved oxygen given for days 0, 7, 14, 21 and 28

CONTROL AND BLANK SYSTEM
- Inoculum blank: 2 replicates
- Reference control: 2 replicates
- Toxicity control: 2 replicates (4.1 mg/L test item, 2 mg/L reference substance)

Reference substance:

aniline

Remarks:

2 mg/L

Key result

Parameter:

% degradation (O2 consumption)

Value:

0

Sampling time:

28 d

Results with reference substance:

In preparations with the reference substance aniline a degradation of 84 % was achieved within 14 days.

Table 1: Mean Dissolved Oxygen.

Sampling Time Points [d]	Inoculum blank	Reference Substance	Test substance	Toxicity control
0	9.65	9.64	9.63	9.63
7	9.31	6.28	9.31	6.15
14	9.24	5.17	9.28	4.97
21	9.00	4.56	8.99	4.33
28	8.98	4.43	9.03	4.35

Table 2: % Degradation.

Sampling Time Points [d]	Reference Substance	Test substance	Toxicity control
7	63	0	29
14	84	0	39
21	92	0	43
28	95	0	43

Table 3: Validity criteria for OECD 301 D.

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%.	0%	yes
Percentage degradation of the reference compound has reached the pass levels by day 14.	84% 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.	39% at Day 14	yes
Oxygen depletion in the inoculum blank should not exceed 1.5 mg dissolved oxygen/L after 28 days.	0.67 mg O2/L	yes
The residual concentration of oxygen in the test bottles should not fall below 0.5 mg/L at any time.	Did not fall below 0.5 mg/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: 0% biodegradation after 28 d (EU Method C.4-E).

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Type of water:

freshwater

Additional information

One study is available testing the biodegradability of the test substance by a non-adapted domestic activated sludge (1999). The test follows the principles of the EU Method C.4-E. and was conducted under GLP standards. 4.1 mg/L initial test item concentration was suspended in mineral medium and inoculated with the mixed population of activated sludge microorganisms. The mixture was incubated for 28 d and the biodegradation of the test material was determined by measuring the reduction of the dissolved oxygen. 0% degradation was determined at test termination revealing that the substance is not readily biodegradable. The toxicity control run in parallel showed that the substance is not inhibiting the sludge microorganisms (39% degradation of reference substance after 28 d).