Chinomethionate

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:

23 February 2018

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)

Deviations:

yes

Remarks:

The difference of extremes of replicate values of the removal of the test substance at the plateau was greater than 20 % in the test item group during the test.

Qualifier:

according to guideline

Guideline:

EPA OPPTS 835.3110 (Ready Biodegradability)

Deviations:

yes

Remarks:

The difference of extremes of replicate values of the removal of the test substance at the plateau was greater than 20 % in the test item group during the test.

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Name: Chinomethionate
Chemical Name: 6-Methyl-1,3-dithiolo[4,5-b]quinoxaline-2-one
Batch/Lot Number: 160722-01
CAS number: 2439-01-2
Description: yellow powder
Expiry Date: 22 July 2018
Purity1: 97%
Molecular formula: C10H6N2OS2
Molecular Weight: 234.3
Storage Conditions: Controlled room temperature (15-25°C, below 70 RH%)
Safety precautions: Enhanced safety precautions were applied considering the supplied safety datasheet to assure personnel health and safety.

Oxygen conditions:

aerobic

Inoculum or test system:

sewage, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): The secondary effluent was supplied from the sewage plant for domestic sewage in Veszprém, Hungary.
- Laboratory culture:
- Method of cultivation:
- Storage conditions:
- Storage length:
- Preparation of inoculum for exposure:
- Pretreatment: The secondary effluent used for this study was allowed to settle approximately for an hour, then the decanted effluent was aerated until use (not later than an hour).
- Concentration of sludge:
- Initial cell/biomass concentration:
- Water filtered: yes/no
- Type and size of filter used, if any:

Duration of test (contact time):

14 d

Initial conc.:

2.7 mg/L

Based on:

ThOD

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium:
- Additional substrate:
- Solubilising agent (type and concentration if used):
- Test temperature:
- pH:
- pH adjusted: yes/no
- CEC (meq/100 g):
- Aeration of dilution water:
- Suspended solids concentration:
- Continuous darkness: yes/no
- Other:

TEST SYSTEM
- Culturing apparatus: stoppered bottles
- Number of culture flasks/concentration: 10
- Method used to create aerobic conditions:
- Method used to create anaerobic conditions:
- Measuring equipment:
- Test performed in closed vessels due to significant volatility of test substance:
- Test performed in open system:
- Details of trap for CO2 and volatile organics if used:
- Other:

SAMPLING
- Sampling frequency:
- Sampling method:
- Sterility check if applicable:
- Sample storage before analysis:
- Other:

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

STATISTICAL METHODS:

Reference substance:

benzoic acid, sodium salt

Key result

Parameter:

% degradation (O2 consumption)

Value:

0

Sampling time:

28 d

The reference item Sodium benzoate was sufficiently degraded to a mean of 76.7 % after 14 days, and to a mean of 82.5 % after 28 days of incubation, based on ThOD, thus confirming the suitability of the used inoculum. 

In the toxicity control containing both, the test item and the reference item Sodium benzoate, a mean of 36.0 % biodegradation was noted within 14 days and 40.1 % biodegradation after 28 days of incubation.

According to the test guidelinesthe test item can be assumed to be not inhibitory at the applied concentration level of 2.7mg/L on the secondary effluent microorganismsbecause degradation was >25 % within 14 days.

The test item was not considered to have significant inhibitory effects on the secondary effluent microorganisms.

Validity criteria fulfilled:

yes

Interpretation of results:

under test conditions no biodegradation observed

Conclusions:

Under the test conditions the percentage biodegradation of Chinomethionate reached a mean of -0.8 % after 28 days based on the ThOD of the test item. According to the test guidelines the pass level for ready biodegradability is removal of 60 % ThOD. Therefore the test item is considered not readily biodegradable.

Description of key information

Under the test conditions the percentage biodegradation of Chinomethionate reached a mean of -0.8 % after 28 days based on the ThOD of the test item. According to the test guidelines the pass level for ready biodegradability is removal of 60 % ThOD. Therefore the test item is considered not readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Type of water:

freshwater