6 alpha-Fluoro-16 alpha-methyl-21-valeryloxy-1,4,9(11)-pregnatriene-3,20-dione

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:

01 Feb to 18 May 2016

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)

Deviations:

no

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

TEST ORGANISMS:
- Type: mixed population of aquatic microorganisms (activated sludge)
- Origin: aeration tank of a wastewater plant treating predominantly domestic sewage (Wupper area water authority, WWTP Odenthal)
- Date of collection: 01 Feb 2016
- Concentration of inoculum: 30 mg/L suspended solids

PRE-TREATMENT OF THE INOCULUM:
- Before use, the inoculum was stored for one day at room temperature under continuous shaking with aeration
- The sludge was washed twice by adding mineral medium and centrifuging for 10 min at 2000 rpm and 20 °C and decanting off the supernatant
- An aliquot of the wet sludge was dried in order to determine the wet weight / dry weight ratio of the sludge and to prepare a stock suspension (activated sludge) of 3 g dw/L
- The calculated amount of sludge, needed to achieve 300 mL of this stock suspension, was dissolved in mineral medium and then filled up to a defined end volume

Duration of test (contact time):

28 d

Initial conc.:

100 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

PRE-TREATMENT OF THE TEST SUBSTANCE:
- 25 mg of the test item were weighed out and filled with 200 mL of mineral medium
- volume was made up to 250 mL with mineral medium containing the inoculum to give a test concentration of 100 mg test item/L

PRE-TREATMENT OF THE REFERENCE COMPOUND:
- 25 mg of the reference compound were weighed out and filled with 200 mL of mineral medium
- volume was made up to 250 mL with mineral medium containing the inoculum to give a test concentration of 100 mg reference compound/L

PRE-TREATMENT OF THE TOXICITY CONTROL:
- 25 mg of the test item and 25 mg of the reference compound were weighed out and filled with 200 mL of mineral medium
- flask volume was made up to 250 mL with mineral medium containing the inoculum to give a test concentration of 100 mg test item and reference compound/L

EXPOSURE CONDITIONS:
- Test volume: 250 mL
- Test apparatus: OxiTopControl System (WTW)
- Number of culture flasks/concentration: 3 (test item), 2 (reference compound), 3 (inoculum blank), 1 (toxicity control)
- Mixing: 1 magnetic stirrer per test vessel
- Test performed in closed vessels: Yes
- Incubation temperature : 22 ± 1 °C
- Test temperature: 22 ± 1°C
- pH: 6.9 - 7.7 (measured in the test flasks after 28 days)
- pH adjusted: no
- Aeration of dilution water: no
- Continuous darkness: yes

SAMPLING
- Sampling frequency: The BOD (in mg O2/L) was measured daily

CONTROL AND BLANK SYSTEM
- Inoculum blank: Blanks with inoculum and without test item were run in parallel (3 replicates)

Reference substance:

benzoic acid, sodium salt

Remarks:

Acros Organics, Purity: 99.9 %; Batch-No.: A0357641

Parameter:

% degradation (O2 consumption)

Value:

6

Sampling time:

7 d

Parameter:

% degradation (O2 consumption)

Value:

10

Sampling time:

14 d

Parameter:

% degradation (O2 consumption)

Value:

14

Sampling time:

21 d

Key result

Parameter:

% degradation (O2 consumption)

Value:

15

Sampling time:

28 d

Details on results:

The toxicity control exhibited degradation rates > 25 % within 14 days.

Results with reference substance:

The reference compound sodium benzoate showed 90 % degradation after 14 days.

Validity criteria for the measurement of the biodegradation according to OECD 301:

Target condition according to guideline:	Actual condition according to the study:	Validity criteria met:
In order to check the procedure, reference compounds which meet the criteria for ready biodegradability are tested by setting up an appropriate vessel in parallel as part of normal test runs. Suitable compounds are aniline (freshly distilled), sodium acetate and sodium benzoate.	Benzoic acid, sodium salt was used as a reference compound.	Yes
A test is considered valid if the 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% and if the percentage degradation of the reference compound has reached the pass levels by day 14.	% degradation of the test substance at the end of the test (28 d) was 15 %	Yes
If in a toxicity test, containing both the test substance and a reference compound, less than 35% degradation (based on total DOC) or less than 25% (based on total ThOD or ThCO2) occurred within 14 days, the test substance can be assumed to be inhibitory. The test series should be repeated, using a lower concentration of test substance (if this can be done without seriously impairing the accuracy of the DOC determination) and/or a higher concentration of inoculum, but not greater than 30 mg solids/L.	The used concentrations of the test substance did not show toxic effects to bacteria (after 14, 21 and 28 d, 48 % degradation was measured based on BOD).	Yes

 

Validity criteria fulfilled:

yes

Remarks:

See "Any other information on results incl. tables"

Interpretation of results:

not readily biodegradable

Conclusions:

Delta-9(11)-Fluocortolon-Valerat showed 15 % degradation within 28 days. The reference compound sodium benzoate was degraded to 90% after 14 days. Thus, the substance is not readily biodegradable.

Executive summary:

The study was conducted in accordance with the Council Regulation (EC) No 440/2008, Method C.4-D "Manometric Respirometry Test" (2008). This test method is in all essential parts identical with OECD Guideline 301 F (adopted July 1992). A suspension of Delta-9(11)-Fluocortolon-Valerat in a mineral medium was inoculated and incubated for 28 d under aerobic conditions. During this period, degradation was followed by continuous automated BOD determinations. The 28-day degradation was 15 % while a biodegradation of 90% within 14 days was observed for reference substance sodium benzoate. In conclusion the substance is not readily biodegradable under test conditions.

Description of key information

Delta-9(11)-Fluocortolon-Valerat showed 15 % degradation within 28 days. Thus, the substance is considered to be "Not Readily Biodegradable".

Key value for chemical safety assessment

Biodegradation in water:

not biodegradable

Type of water:

freshwater

Additional information

The reference compound sodium benzoate was degraded to 90% after 14 days.