Estr-4-ene-3,17-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:

1995

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Reason / purpose for cross-reference:

reference to same study

Reason / purpose for cross-reference:

reference to other study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 E (Ready biodegradability: Modified OECD Screening Test)

Deviations:

no

Principles of method if other than guideline:

Not relevant

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

- Type: mixed population of aquatic microorganisms (activated sewage sludge)
- Origin: municipal sewage treatment plant, predominantly dealing with domestic sewage
- Date of collection: on the day of the start of the experiment

Pre-treatment of the inoculum:
- The sewage sludge was kept under aerobic conditions
- Approximately 2 hours before the start of the incubation, aeration was discontinued and the sludge was allowed to sediment
- The inoculum was obtained from the supernatant

Duration of test (contact time):

28 d

Initial conc.:

20 mg/L

Based on:

DOC

Details on study design:

TEST CONDITIONS:

PREPARATION OF THE STOCK SOLUTIONS::
- 1 g sodium acetate (reference substance) was dissolved in 1000 mL aqua dest. (290.1 mg/L TOC/289.8 mg/L DOC)
- 200.2 mg test substance was dissolved in 2 L aqua dest. (78.7 mg/L TOC/76.5 mg/L DOC)
- Since the difference in TOC and DOC of the test solutions did not exceed 10%, all test solutions were prepared by using the respective unfiltered stock solutions

PREPARATION OF THE TEST SOLUTION:
- Sodium acetate: 69 mL of the stock solution, 15 mL nutrient solution and 915.5 mL aqua dest.
- Test item + sodium acetate: 69 mL of the sodium acetate stock solution + 254 mL of the test item stock solution + 15 mL nutrient solution + 661.5 mL aqua dest.
- Test item: 254 mL of the stock solution, 15 mL nutrient solution and 730.5 mL aqua dest.

ADDITION OF THE INOCULUM:
- The test and reference substance solutions were measured for pH (7.5); they were not pH-adjusted
- 0.5 mL of the inoculum was added to each test solution as weil as the reference solution; additionally, a blank containing the nutrient solutions, aqua dest. and the inoculum was prepared
- Triplicate 2-litre glass beakers were used for the blank and for the test substance solution; the reference and the toxicity control solutions were each incubated in one 2-litre grass beaker

EXPOSURE CONDITIONS:
- Final test concentration: approx. 20 mg DOC/1000 mL
- Mixing : 1 magnetic stirrer per test vessel; constant stirring in darkness
- Incubation time : 28 days
- Incubation temperature : 23 ± 1 °C
- pH value of test solutions: 7.5 (not adjusted)

Reference substance:

acetic acid, sodium salt

Remarks:

Purity not specified

Parameter:

% degradation (DOC removal)

Value:

16

Sampling time:

8 d

Parameter:

% degradation (DOC removal)

Value:

82

Sampling time:

15 d

Parameter:

% degradation (DOC removal)

Value:

89

Sampling time:

22 d

Parameter:

% degradation (DOC removal)

Value:

85

Sampling time:

28 d

Details on results:

In the toxicity control, the reference compound sodium acetate plus the test item was degraded to 96 % within 28 days.

Results with reference substance:

The reference compound sodium acetate was degraded to 99 % on day 5.

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

Within 28 days the substance was degraded to 85%. The reference compound was degraded to 99% on day 5. In the toxicity control, the reference compound sodium acetate plus the test item was degraded to 96 % within 28 days.

Executive summary:

The study on ready biodegradability was conducted in agreement with the test guideline of the OECD, No. 301 E. The substance was incubated in aqueous solution including nutrients with microorganisms from a municipal sewage treatment plant for 28 days. The nutrient solution contained phosphates, ammonium chloride, vitamins and trace elements. The test concentration was 20 mg/L as dissolved organic carbon (DOC) for the test substance. Additionally, a reference substance (sodium acetate) was tested at the same DOC concentration and according to the same procedure in order to verity the viability and activity of the degrading microorganisms. Furthermore, one flask containing the test substance and the reference substance, in each case 20 mg/L as DOC, total 40 mg/L as DOC, was tested as a toxicity contral. Three additional vessels without any test or reference substance were used as blank (control). The biological degradation of the test and reference substances was evaluated by the decrease of DOC in the solutions. DOC was analysed on days 1, 2, 5, 8, 15, 22, 28 and 29. Within 28 days the substance was degraded to 85%. The reference compound was degraded to 99% on day 5. In the toxicity control, the reference compound sodium acetate plus the test item was degraded to 96 % within 28 days. Therefore the substance has to be classified as "Readily biodegradable".

Description of key information

The substance showed 85% degradation within 28 days. The reference compound was degraded to 99% . In the toxicity control, the reference compound sodium acetate plus the test item was degraded to 96 % within 28 days.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Type of water:

freshwater