2-fluoro-6-trifluoromethylpyridine

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 D (Ready Biodegradability: Closed Bottle Test)

Deviations:

yes

Remarks:

The oxygen depletion in the blank after 28 days was 1.6 mg O2/L. This is just outside the value of 1.5 mgO2/L given in the OECD guideline. This deviation of 0.1 mgO2/L is not considered to have affected the validity of the study.

GLP compliance:

yes

Specific details on test material used for the study:

Substance ID: F6TF
Lot #: AH0148
Purity: 100%

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

Secondary effluent was obtained from a laboratory scale rolling tube reactor, which treats predominantly domestic sewage. This was added to the test medium at a level of 1 mL/L.

Duration of test (contact time):

28 d

Initial conc.:

35.6 mg/L

Based on:

other: nominal concentration (measured 22 mg/L)

Initial conc.:

17.8 mg/L

Based on:

other: nominal concentration (measured 11 mg/L)

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

The test medium was made up according to the OECD guideline and contained the following nutrients per litre of deionised water: 8.5 mg of KH2PO4, 21.75 mg of K2HPO4, 33.4 mg of Na2HPO4.2H2O, 0.5 mg of NH4Cl, 22.5 mg of MgSO4.7H2O, 54.3 mg of CaCl2.6H20, 0.20 mg of FeCl3.6H2O and 0.40 mg of EDTA (disodium salt).

The measurement of oxygen uptake was carried out in completely filled and closed glass reagent bottles with ground glass stoppers, the volume of which has been determined as 281 ± 2 ml at 20 ± 2 ºC. The bottles were inoculated with micro-organisms from a mixed population and incubated in the dark at 20 ± 1 ºC. The dissolved oxygen concentration in sacrificial test and control bottles was measured at intervals during the test using a YSI oxygen electrode.

Prior to filling the bottles, the prepared mineral medium and inoculurn was aerated for at least two hours and then left to stand for 30 minutes. On Day 0 of the study 32 control blank bottles were set up containing mineral medium and inoculum only. There were 25 reference compound bottles containing inoculated medium and sodium benzoate. And two sets of 17 test bottles, each containing inoculated medium and 5 or 10 mg of test substance, giving nominal test concentrations of 17.8 and 35.6 mg/L, respectively.

Oxygen uptake was recorded at 5 day intervals during the 28 day experimental period (Day 25 analysis replaced by Day 28). The readings obtained were corrected for the O2 demand of the blank and the biodegradation was calculated as a percentage of the theoretical oxygen demand for the substance under test.

Reference substance:

benzoic acid, sodium salt

Test performance:

The substance was not suitable for COD determination by standard methods. The substance was known to be volatile and during the standard COD determination the test compound would be driven off during the heating part of the analysis. Therefore the biochemical oxygen demand (BOD) values have been compared to the theoretical oxygen demand (ThOD) to allow the calculation of % degradation.

Key result

Parameter:

% degradation (O2 consumption)

Value:

< 5.9

Sampling time:

28 d

Remarks on result:

other: nominal concentration 35.6 mg/L (measured 22 mg/L)

Key result

Parameter:

% degradation (O2 consumption)

Value:

< 11

Sampling time:

28 d

Remarks on result:

other: nominal concentration 17.8 mg/L (measured 11 mg/L)

Details on results:

At Day 0 the measured concentrations of the test substance in the nominal 17.8 and 35.6 mg/L test solutions were both 62% of nominal. At Day 28 the measured concentrations were 62 and 65% of nominal, indicating that the test substance was still present. This also confirms the BOD results that the test substance is not readily biodegradable.

Parameter:

ThOD

Value:

969.7 mg O2/g test mat.

Results with reference substance:

Sodium benzoate attained a maximum level of biodegradation (based on the B0D:COD ratio) of 109% at day 20. Sodium benzoate achieved 63% at day 10, within the 14 day window allowed for a closed bottle test. Indicating that the activated sludge contained viable organisms.

Measured Dissolved Oxygen (mg O2/L) and Associated Calculated Data

Bottle Contents or Calculated Value	Day 5	Day 10	Day 15	Day 20	Day 28
Blank Control, (Initial dissolved oxygen at 0 hours = 9.1 mg O2/L)	9.0	9.0	7.8	7.8	7.5
	9.0	8.9	8.1	7.9	7.7
	9.0	8.9	8.1	8.0	7.9
	8.9	8.9	8.1	7.9	7.3
	9.0	8.9	7.8	7.8	7.0
	8.9	9.0	8.2	8.0	7.7
Mean (mg O2/L)	9.0	8.9	8.0	7.9	7.5
Calculated Concentration (mg/L) (see Note A)	18.149	18.007	18.007	18.185	18.007
5 mg Test Substance per Vessel, Nominal 17.8 mg/L, Measured 9.1 mg/L	8.6	8.8	8.0	7.6	7.7
	8.7	8.8	7.7	7.7	7.9
	8.7	8.8	7.9	7.7	7.8
Mean (mg O2/L)	8.7	8.8	7.9	7.7	7.8
Blank - Mean (mg O2/L)	<2	<2	<2	<2	<2
BOD (mg O2/g)	<110	<111	<111	<110	<111
% Biodegradation (BOD / ThOD x 100)	<11%	<11%	<11%	<11%	<11%
Calculated Concentration (mg/L) (see Note A)	36.192	35.658	35.693	35.729	35.373
10 mg Test Substance per Vessel, Nominal 35.6 mg/L, Measured 24 mg/L	8.8	8.9	8.0	7.8	8.0
	8.8	8.9	7.8	7.8	8.0
	8.8	8.9	8.0	7.8	7.9
Mean (mg O2/L)	8.8	8.9	7.9	7.8	8.0
Blank - Mean (mg O2/L)	<2	<2	<2	<2	<2
BOD (mg O2/g)	<55	<78	<56	<56	<57
% Biodegradation (BOD / ThOD x 100)	<5.7%	<8%	<5.8%	<5.8%	<5.9%

Note A: concentration is calculated from the largest weight used for each set of triplicate bottles divided by the bottle volume, then x 1000

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

The test substance is not readily biodegradable. Degradation after 28 days was < 11% at 11 mg/L and < 5.9% at 22 mg/L.

Executive summary:

A closed bottle biodegradation test was conducted with two concentrations of the test substance according to OECD Guideline 301D.

The closed bottle study was started by the direct addition of 5 and 10 mg of test substance to 281 ml capacity test bottles, giving two nominal test concentrations, 17.8 and 35.6 mg/L.

The theoretical oxygen demand (ThOD) of the test substance is 969.7 mg O2/g (assuming no nitrification). At 28 days the oxygen consumptions in the nominal 17.8 and 35.6 mg/L test concentrations were 0.0078 and 0.0080 g O2/g respectively. The percentage degradation was calculated as (BOD/ThOD) x 100.

At day 0 the measured concentrations of F6TF in the nominal 17.8 and 35.6 mg/L test solutions were both 62% of nominal. At day 28 the measured concentrations were 62 and 65% respectively, of nominal.

Samples were incubated in the dark at approximately 20 ºC and analysed at 5 day intervals to determine the biological oxygen demand. Degradation after 28 days was < 11% at the lowest concentration tested (11 mg/L) and < 5.9% at 22 mg/L, indicating that the test substance is not readily biodegradable.

 

Description of key information

Not readily or inherently biodegradable

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Additional information

Four biodegradation studies are available and are consistent in quality and results. All studies are K1 and followed OECD guidelines. Zero to 11% of the substance degraded after 28 days, indicating that the test substance is not readily or inherently biodegradable.