9beta,11beta-Epoxy-6alpha-fluoro-16alpha-methyl-21-valeryloxy-1,4-pregnadiene-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:

1993

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)

Qualifier:

equivalent or similar to guideline

Guideline:

EU Method C.4-E (Determination of the "Ready" Biodegradability - Closed Bottle Test)

GLP compliance:

no

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

TEST ORGANISMS:
- Type: Activated sewage sludge bacteria
- Origin: aeration stage of the HRC sewage treatment plant treating predominantly domestic sewage
- Date of collection: 1993-03-18

PRE-TREATMENT OF THE INOCULUM:
- The sample was allowed to settle for approx. 30 minutes and the supernatant filtered through Whatman GFA coarse filter paper (first 250 mL discarded)
- The filtrate was maintained under aeration and used within 24 hours of collection

Duration of test (contact time):

28 d

Initial conc.:

3 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

STUDY PERIOD:
- Start of experimental phase: 1993-03-18
- End of experimental phase: 1993-04-15

PRE-TREATMENT OF THE TEST SUBSTANCE:
- The test substance was dissolved in chloroform to give a stock solution of 56 mg/mL
- 10 µL aliquots of stock solution were placed on individual pieces of Whatman GFA glass filter paper and the solvent allowed to evaporate to dryness
- One piece of paper was placed in each test bottle prior to fllling with inoculated medium
- Filter paper blanks were prepared in the same manner using solvent only

PRE-TREATMENT OF THE REFERENCE COMPOUND:
- Reference substance standards (3 mg/L) were prepared by dissolving the sample directly in nutrient medium

TEST SERIES:
- Non-inoculated nutrient medium
- Inoculated nutrient medium
- Inoculated nutrient medium plus filter paper
- 2 mg/L test substance plus filter paper
- 3 mg/L sodium benzoate
- 2 mg/L test substance plus filter paper and 3 mg/L sodium benzoate (Toxicity control)

EXPOSURE CONDITIONS:
- Test volume: 250 mL
- Test apparatus: Yellow Springs BOD Meter (Model 59)
- Test performed in closed vessels: Yes
- Incubation temperature: 20 ± 1 °C

SAMPLING
- Sampling frequency: oxygen determination per bottle at day 0, 5, 15 and 28 (duplicate bottles at each sampling time)

CONTROL AND BLANK SYSTEM
- Inoculum blank: Blanks with inoculum and without test item were run

Reference substance:

benzoic acid, sodium salt

Remarks:

(Batch no. 30055292 (Fisons))

Parameter:

% degradation (O2 consumption)

Value:

11

Sampling time:

7 d

Parameter:

% degradation (O2 consumption)

Value:

8

Sampling time:

15 d

Key result

Parameter:

% degradation (O2 consumption)

Value:

11

Sampling time:

28 d

Details on results:

There was no evidence of inhibitory effects under the conditions of this test .

Parameter:

ThOD

Value:

1.67 mg O2/g test mat.

Remarks on result:

other: Estimated oxygen depletion for 3 mgL test item

Results with reference substance:

Sodium benzoate attained 86% biodegradation after 28 days .

- Cultures containing both test and standard substances combined showed an oxygen depletion value 1 % higher than that anticipated on the basis of results from separate cultures. Consequently the test item was not considered to have had an inhibitory effect on sewage bacteria under the conditions of this test.

- Oxygen depletions in the inoculated (<0.5 mg O₂/L after 5 days and <0.6 mg O₂/L after 28 days) and non-inoculated control (<0.3 mg O₂/L after 5 days and <0.4 mg O₂/L after 28 days) series were within the prescribed limits.

Validity criteria fulfilled:

yes

Remarks:

ready biodegradation of reference compound > 60 % within 14 days; toxicity control exhibited degradation rates > 25 % within 14 days; replicates difference < 20 %; oxygen uptake of the inoculum blank was <= 60 mg/L; no pH influence

Interpretation of results:

under test conditions no biodegradation observed

Conclusions:

Epoxid-Valerat showed 11 % degradation within 28 days. Therefore the substance is not readily biodegradable. The reference compound sodium benzoate showed more than 70 % degradation after 5 days .

Executive summary:

The study was conducted in accordance with OECD Guideline for Testing of Chemicals No. 301 D and EEC Methods for the Determination of Ecotoxicity, EEC Directive 67/548 Annex V Part C.6 (84/449/EEC). The test substance Epoxid-Valerat, dissolved in inorganic nutrient medium (concentration: 2 mg/L) and inoculated with activated sewage sludge bacteria, was incubated in duplicate in sealed bottles for 28 days at 20 ± 1°C. On days 0, 5, 15, and 28 duplicate bottles were taken and the concentration of dissolved oxygen was measured using an oxygen probe. Percent biodegradation values were calculated by comparing the oxygen depletion with the theoretical oxygen demand. The biodegradation was also studied in bottles containing sodium benzoate alone as reference compound (3 mg/) as well as test item (2 mg/L) plus sodium benzoate (3 mg/L) for investigation of inhibitory effects of the test substance, all under the same conditions. Epoxid-Valerat showed only up to 11 % degradation. There was no indication of inhibitory effects caused by the test compound. The reference compound showed more than 70 % degradation after 5 days. In conclusion Epoxid-Valerat is not readily biodegradable.

Description of key information

The substance showed 11 % degradation within 28 days. The reference compound showed more than 70 % degradation after 5 days. The substance is considered to be "Not Readily Biodegradable".

 

Key value for chemical safety assessment

Biodegradation in water:

not biodegradable

Type of water:

freshwater