Triflumezopyrim

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

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

Qualifier:

according to guideline

Guideline:

EPA OPPTS 835.3110 (Ready Biodegradability)

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: Cambridge Wastewater Treatment Facility, Cambridge, Maryland. This facility treats predominantly residential wastes.
- Preparation of inoculum for exposure: The sludge was sieved using a 2-mm screen, adjusted to approximately 1,000 mg total suspended solids (TSS)/L with test medium and then aerated at test temperature for six days until use. A total suspended solids measurement and standard plate count were performed on the inoculum on the day of test chamber preparation. Plates were incubated at 20 ± 3ºC for approximately 48 hours.

Duration of test (contact time):

28 d

Initial conc.:

10 mg/L

Based on:

ThCO2

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITION
- Composition of medium: The test medium was a modified biochemical oxygen demand (BOD) test dilution water and was prepared using high quality water.
The test medium contained the following standard reagent solutions per liter of high quality water (Nanopure):
1 mL of calcium chloride solution (2.75%)
1 mL of ferric chloride solution (0.025%)
1 mL of magnesium sulfate solution (2.25%)
10 mL of phosphate buffer solution (pH 7.4)

- Test temperature: 19.1 to 20.9ºC
- pH: 7.6
- Aeration of dilution water: All chambers were aerated with CO2-free air for approximately 24 hours at a rate of approximately 50 mL per minute to purge the systems of CO2
- Suspended solids concentration: Approximately 1,000 mg total suspended solids (TSS)/L with test medium

TEST SYSTEM
- Culturing apparatus: Amber 4-liter bottles
- Number of culture flasks/concentration: Each group contained three replicate test chambers except for the toxicity control, which was not replicated.
- Measuring equipment: Shimadzu Model TOC-VCSH carbon analyzer
- Details of trap for CO2 and volatile organics if used: Three CO2 traps, each containing approximately 100 mL of 0.5 M KOH, were connected to the exit air lines of each chamber

SAMPLING
- Sampling frequency: On days 1, 4, 7, 12, 15, 18, 21 and 25 the CO2 trap nearest the test chamber was removed and analyzed for inorganic carbon. The two remaining traps were placed one position closer to the test chamber and a new trap was placed on the end of the series.

CONTROL AND BLANK SYSTEM
- Inoculum blank: Yes

Reference substance:

benzoic acid, sodium salt

Key result

Parameter:

% degradation (CO2 evolution)

Value:

4.6

Sampling time:

28 d

Details on results:

The test substance may not be considered readily biodegradable since 60% TCO2 was not achieved. The toxicity control achieved >25% degradation by Day 14 and, therefore, test substance is considered non-inhibitory at the concentration tested in this study.

Results with reference substance:

The measured total organic carbon (TOC) concentration of the reference substance stock solution was 395.5 mg C/L.
The viability of the inoculum and validity of the test were supported by the results of the reference substance, from which an average of 98.2% of theoretical CO2 was evolved. An average percent biodegradation of greater than 60% was achieved by Day 7, thereby fulfilling the criteria for a valid test by reaching the pass level by Day 14.

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

The test substance does not meet the criteria to be classified as readily biodegradable.

Executive summary:

The biodegradability of the test substance was determined by the Carbon Dioxide Evolution Test Method (OECD Guideline 301B and OPPTS 835.3110).

In the CO2 test, inoculated mineral medium was dosed with a known amount of test substance as the nominal sole source of organic carbon and aerated with CO2-free air. The CO2 produced from the mineralization of organic carbon within the test chambers was displaced by the flow of CO2-free air and trapped as K2CO3 in KOH trapping solution. The amount of CO2 produced by the test substance (corrected for that evolved by the blank inoculum) is expressed as a percentage of the theoretical amount of CO2 (TCO2) that could have been produced if complete biodegradation of the test substance occurred. The test contained a blank control group, a reference group, a treatment group and a toxicity control. Each group contained three replicate test chambers except for the toxicity control, which was not replicated. The blank control was used to measure the background CO2 production of the inoculum and was not dosed with a carbon source. The reference chambers were dosed with sodium benzoate, a substance known to be biodegradable, at a nominal concentration of 10 mg C/L. The treatment group test chambers were used to evaluate the test substance at a nominal concentration of approximately 10 mg C/L. The toxicity control was used to evaluate the inhibition of the test substance to the inoculum and was dosed with both the reference (10 mg C/L) and test (10 mg C/L) substances. The results indicated that the activated sludge inoculum was active, degrading the reference substance 98.2%. The test substance was not inhibitory to the microbial inoculum. The average cumulative percent biodegradation for the test substance was 4.6% after 28 days.

Based on the results of this study, the test substance does not meet the criteria to be classified as readily biodegradable.

Description of key information

OECD Guideline 301B

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Additional information

The average cumulative percent biodegradation for the test substance was 4.6% after 28 days. The test substance does not meet the criteria to be classified as readily biodegradable.