5-amino-1-[2,6-dichloro-4-(trifluoromethyl)phenyl]-4-(ethylsulfinyl)-1H-pyrazole-3-carbonitrile

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:

02 Mar - 31 Mar 1999

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)

Version / remarks:

adopted in 1992

Deviations:

yes

Remarks:

At test start, the inorganic carbon content of the test substance suspension in medium was 15% of total carbon and not < 5% as recommended.

Qualifier:

according to guideline

Guideline:

EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)

GLP compliance:

yes (incl. QA statement)

Remarks:

The Department of Health of the Government of the United Kingdom, date of inspection 23 Mar 1998

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

- Source of inoculum/activated sludge: A mixed population of activated sewage sludge micro-organisms was obtained on 01 Mar 1999 from the aeration stage of the Severn Trent Water Plc sewage treatment plant at Belper, Derbyshire, UK, which treats predominantly domestic sewage.
- Storage conditions: continuous aeration upon receipt
- Preparation of inoculum for exposure: A sample of the activated sewage sludge was washed three times by settlement and resuspension in culture medium to remove any excessive amounts of dissolved organic carbon.

Duration of test (contact time):

28 d

Initial conc.:

10 mg/L

Based on:

other: TOC

Initial conc.:

25.4 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium: standard medium as recommended in the guideline
- Test temperature: 21 °C
- Suspended solids concentration: 30 mg suspended solids/L
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: 5 L glass culture vessels containing 3 L of solution
- Number of culture flasks/concentration: 2
- Measuring equipment: The CO2 produced by degradation was collected in two 500 mL Dreschel bottles containing 350 mL of 0.05 M NaOH. The CO2 absorbing solutions were prepared using purified de-gassed water. The samples were analysed for CO2 using an Ionics 1555B TOC analyser and a Dohrmann DC-190 TOC analyser. 40 - 50 µl of the samples were injected into the inorganic carbon channel of the TOC analyser.

SAMPLING
- Sampling frequency: the first CO2 absorber vessel was sampled on days 0, 1, 2, 3, 6, 8, 10, 14, 16, 20, 22, 24, 27, 28 and 29; the second absorber vessel was sampled on days 0 and 29
- Sample storage before analysis: instant analysis

CONTROL AND BLANK SYSTEM
- Inoculum blank: 2 vessels
- Toxicity control: 1 vessel
- Reference control: 2 vessels

Reference substance:

benzoic acid, sodium salt

Parameter:

% degradation (CO2 evolution)

Value:

18

Sampling time:

28 d

Remarks on result:

other: 0% degradation up to day 20.

Details on results:

- The carbon content of the test material was determined as 39.31%.
- The toxicity control attained 75% degradation after 28 days confirming the test material to be non-toxic to the microorganisms.
- The total CO2 evolution in the inoculum blank was 28.8 mg/L after 28 days (required: ≤ 40 mg/L).

Results with reference substance:

The reference substance attained 74% degradation after 28 days (77% after 10 days) confirming the suitability of the test system.

Table 1. Percentage biodegradation values

Day	%Degradation Sodium benzoate	% Degradation Ethiprole (RPA 107382)	% Degradation Ethiprole (RPA 107382) plus sodium benzoate toxicity control
0	0	0	0
1	8	0	5
2	33	0	19
3	44	0	27
6	70	0	38
8	70	0	35
10	77	8	36
14	77	0	46
16	75	0	47
20	74	0	68
22	74	9	69
24	74	12	76
27	75	16	74
28	74	18	75
29*	77	22	78

* Day 29 values corrected to include any carry-over of CO2 detected in absorber 2

 

Table 2. Total and inorganic carbon values in the culture vessels at day 0

Test vessel	Total Carbon (mg/L)	Inorganic Carbon (mg/L)	% Inorganic Carbon
Sodium benzoate 10 mg C/I R1	11.21	1.62	14
Sodium benzoate 10 mg C/I R2	11.68	1.64	14
Ethiprole 10 mg C/I R1	12.86	1.88	15
Ethiprole 10 mg C/I R2	12.67	1.76	14
Ethiprole plus sodium benzoate Toxicity control 20 mg C/I	22.47	1.98	9

 R1, R2 = replicate 1 and replicate 2

Table 3: Validity criteria for OECD 301 B.

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%.	CV at day 29 = 3.39%	Yes
Percentage degradation of the reference compound reached the pass level by day 14 (≥ 60%).	77%	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.	46%	Yes
The IC content of the test substance suspension in the mineral medium at the beginning of the test must be less than 5% of the TC.	15% in replicate 1 and 14% in replicate 2	No
The total CO2 evolution in the inoculum blank at the end of the test should not normally exceed 40 mg/L medium.	28.8 mg/L	Yes

 

Validity criteria fulfilled:

no

Remarks:

See Table 3 in 'any other information on results incl.tables'

Interpretation of results:

not readily biodegradable

Description of key information

Not readily biodegradable: 18% (ThCO2) in 28 days (OECD 301 B)

Key value for chemical safety assessment

Biodegradation in water:

not biodegradable

Additional information

One study on the ready biodegradability of the substance carried out according to GLP and OECD guideline 301 B is available. The study used activated sludge from a sewage treatment plant treating predominantly domestic sewage and 25.4 mg/L of test material, corresponding to 10 mg TOC/L. The test substance reached 18% degradation within 28 days while the reference substance attained 74% and the toxicity control 75% degradation. Thus, the test substance can be assessed as not readily biodegradable under OECD conditions.