Pregn-4-ene-3,20-dione, 21-(acetyloxy)-6-fluoro-11-hydroxy-16-methyl-, (6.alpha.,11.beta.,16.alpha.)-

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 Nov 1998 - 15 Dec 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)

Qualifier:

equivalent or similar to guideline

Guideline:

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

GLP compliance:

no

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

Inoculum:
- Type: predominantly domestic sewage
- Origin: A well-operated municipal sewage treatment plant (Kläranlage Berlin-Ruhleben, Germany),

Pre-treatment of the inoculum:
- Upon arrival at the laboratory, the activated sludge was aerated and stirred for approx. 2.5 hours
- The sludge was homogenised in a blender about 1.5 hours
- Then it was allowed to settle for about 1 hours and 16 mL inoculum corresponding to 90 mg suspended solids were taken from the supernatant for each test vessel

Duration of test (contact time):

28 d

Initial conc.:

10 mg/L

Based on:

DOC

Parameter followed for biodegradation estimation:

CO2 evolution

Reference substance:

acetic acid, sodium salt

Remarks:

Merck AG, Batch No. TA 662668502

Test performance:

I. Inoculation, preparation of the test and reference compound solution:
- 16 mL of the inoculum from the activated sludge were added to the nutrient solutions and the demineralized water
- These mixtures were aerated with CO2-free air for about 24 hours before test and reference compounds were added
- CO2-free air was obtained by bubbling filtered air through activated charcoal and soda lime pellets
- After about 24 hours the test and reference substance was added

II. Sets of test, reference and control solutions:
- Test substance: 10 mg/L (triplicate)
- Reference substance (sodium acetate): 10 mg/L (single set)
- Toxicity control (test item + sodium acetate ): 10 mg/L+10 mg/L (single set)
- Blank control: 0 mg/L (triplicate)

III. Test Design:
- The test material was dispersed well in test tubes containing approximately 1-2 mL demineralized water and added directly at amounts of 43.8 mg test item to each of three test vessels
- Finally, the test tubes were rinsed with 2-3 mL demineralized water
- The reference substance solution was prepared by using 103 mL of a stock solution of 1.0 g sodium acetate in 1 L demineralized water
- The toxicity control was prepared by adding 103 mL of the reference substance (stock solution) and 43.8 mg of test item
- The blank control contained only nutrient solution, inoculum and demineralized water
- Finally, each vessel was filled up with demineralized water to a volume of 3000 mL

IV. lncubation conditions:
- The test solutions were incubated at 22 to 24 °C for 28 days
- Furthermore, the test solutions were supplied with filtered CO2-free air (2.5 to 5.0 L air per hour for each test vessel) for 30 days.
- On day 29 the pH of all test vessels ranged trom 8.0 to 8.2. After the measurements of pH on day 29, 1 mL of concentrated HCI was added to each test vessel in order to convert all dissolved inorganic carbon into CO2

Key result

Parameter:

% degradation (CO2 evolution)

Value:

6

Sampling time:

28 d

Parameter:

% degradation (CO2 evolution)

Value:

4

Sampling time:

20 d

Parameter:

% degradation (CO2 evolution)

Value:

1

Sampling time:

10 d

Details on results:

The toxicity control did not reveal any toxic influence of the test substance (52 % degradation).

Results with reference substance:

The reference substance sodium acetate passed 60 % degradation at day 11.

Validity criteria for the measurement of the biodegradation:

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.	Sodium acetate was used as a reference substance.	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.	The reference compound sodium acetate was degraded to 65 % on day 11 (~ 10 days of incubation) and to 87 % on day 30.	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.	In the toxicity control, the reference compound (sodium acetate) plus the test compound ZK 47525 was degraded to 52 % on day 30 (~ 28 days of incubation).	Yes

 

Validity criteria fulfilled:

yes

Interpretation of results:

under test conditions no biodegradation observed

Conclusions:

In the study on ready biodegradability Fluocortolon-A-Acetat was degraded to 6 % within 28 days of incubation. Thus, the substance is not readily biodegradable. The reference compound sodium acetate was degraded to 60 % after 11 days of incubation.

Executive summary:

The study was conducted in agreement with the OECD test guideline No. 301 B. Fluocortolon-A-Acetat was incubated in aqueous solutions including nutrients, with microorganisms from a municipal sewage treatment plant for 28 days. The test item was incubated in a concentration of 10 mg carbon/L in triplicate. Additionally, a reference substance (sodium acetate) was tested in a single set according to the same procedure, in order to verify the viability and activity of the degrading microorganisms. One further set was incubated with sodium acetate at 10 mg carbon/L (reference substance) plus test item at 10 mg carbon/L representing a toxicity control. Furthermore, a blank control was tested in triplicate without any test or reference substance. The biological degradation of the test and reference substances was evaluated by measurement of the carbon dioxide (CO₂) produced during the test period. CO₂ production was determined on days 4, 7, 10, 11, 16, 21, 25 and 30. On day 29 the solutions were acidified in order to expel all dissolved CO₂ and CO₂ was determined on day 30. The CO₂ production was calculated as the percentage of total CO₂ that the test material could theoretically have produced based on carbon content. The blank CO₂ production was subtracted for correction. In the toxicity control, the reference compound (sodium acetate) plus the test compound was degraded to 52 % on day 30 (28 days of incubation). In accordance with the OECD 301 B Fluocortolon-A-acetat is not readily biodegradable under the conditions of the test.

Description of key information

In the study on ready biodegradability according to OECD guideline 301 B Fluocortolon-A-Acetat was degraded to 6 % within 28 days. The reference compound sodium acetate was degraded to 60 % after 11 days of incubation. The substance is not readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Type of water:

freshwater