3-methoxyoestra-1,3,5(10)-trien-17-one

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 B (Ready Biodegradability: CO2 Evolution Test)

Deviations:

no

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge (adaptation not specified)

Details on inoculum:

The activated sewage sludge for the inoculum was collected on the day before the start of the experiment from a well-operated municipal sewage treatment plant ("Kläranlage Berlin-Ruhleben"), predominantly dealing with domestic sewage. Upon arrival at the laboratory, the activated sludge was stirred and aerated for approx. 2 h. Thereafter, the sludge was homogenised in a blender. Then it was allowed to settle for approx. 1.5 h. 23 mL = 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:

TOC

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

Preparation of the test and refernece compound solution and addition of inoculum
- test solution was prepared in triplicate
- one reference solution was prepared
- one toxicity control solution was prepared
- blank control was prepared in triplicate
The test material was despersed well in vessels containing approx. 1-2 mL demineralized water and added directly at amounts of 37, 39 mg test substance to each of three test bottles. Finally the vessels were rinsed with 2-3 mL demineralized water.
The reference substance solution was prepared by using 102 mL of a stock solution of 1.0 g sodium acetate in 1 L demineralizied water.
The toxicity control was prepared by adding 102 mL of the reference substance (stock solution) and 37, 39 mg of test substance.
The blank contained only nutrient solution, inoculum and demineralized water. 23 mL of the inoculum from the activated sludge were added tot the nutrient solutions and the demineralized water. These mixtures were aerated with CO2-free air for about 24 h to purge the system of carbon dioxide before test and reference compounds were added. CO2-free air was obtained by bubbling filtered air through activated charcoal and soda lime pellets.
After 24 h the test and reference substance was added. Finally, each vessel was filled up with demineralized water to a volume of 300 mL.

Incubation conditions
The test solutions were incubated at 19 - 22°C for 28 d. Furthermore, the test solutions were supplied with filtered CO2-free aeration (1.5 - 6.5 L/ h for each test vessel) for 29 days. On day 28 the pH of all test vessels ranged from 7.8 - 8.0. After the measurement of pH on day 28, 1 mL of concentrated HCl was addded to each test vessel in order to voncert all dissolved inorganic carbon into CO2.

Reference substance:

acetic acid, sodium salt

Remarks:

batch no. 945 TA 56968, Merck Darmstadt

Key result

Parameter:

% degradation (CO2 evolution)

Value:

7

Sampling time:

29 d

Remarks on result:

other:

Remarks:

= 28 days of incubation

Details on results:

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 substracted for correction.

Results with reference substance:

The reference compound sodium acetate showed a biodegradation of 83 % after 29 d. The time required for 60 % biodegradation of the reference compound was less than 9 d.

The toxicity control showed a degradation of 44 %. Thus the test substance is not toxic towards the microorganisms.

Interpretation of results:

not readily biodegradable

Conclusions:

As a degradation of 7 % was obeserved for the test substance after 28 days, Estron-Methylether can be considered as not readily biodegradable.

Executive summary:

A study was conducted according to OECD 301B to assess the biodegration of Estron-Methylether. The test substance was incubated in an aqueous solution including nutrients with microorganisms from a municipal sewage treatment plant for 28 days (start of treatment = day 1).

The test substance 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 migroorganisms. Turthermore, a blank control was tested in triplicate without any test or reference substance. One further vessel was incubated as toxicity control with soldium acetate 10 mg carbon/L (reference substance) plus reference substance 10 mg carbon/L.

The biological degradation of the test and reference substances was evaluated by measurement of the CO2 produced during the test period. CO2 production was determind on day 4, 7, 9, 11, 15, 18, 23 and 29. On day 28 the solutions were acidified in order to expel all dissolved CO2 and CO2 was determined on day 29.

The reference compound sodium acetate was degraded to 83% on day 29 (= 28 d of incubation).

In the toxicity control a biodegradation of 44 % was observed on day 29 (= 28 d of incubation).

The test substance was degraded to 7% on day 11 (= 10 days of incubation) where a plateau was reached.

Thus Estron-Methylether can be considered to be not readily biodegradable.

Description of key information

A study was conducted according to OECD 301B to assess the biodegration of Estron-Methylether. The test substance was incubated in an aqueous solution including nutrients with microorganisms from a municipal sewage treatment plant for 28 days (start of treatment = day 1).

The test substance 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 migroorganisms. Turthermore, a blank control was tested in triplicate without any test or reference substance. One further vessel was incubated as toxicity control with soldium acetate 10 mg carbon/L (reference substance) plus reference substance 10 mg carbon/L.

The biological degradation of the test and reference substances was evaluated by measurement of the CO2 produced during the test period. CO2 production was determind on day 4, 7, 9, 11, 15, 18, 23 and 29. On day 28 the solutions were acidified in order to expel all dissolved CO2 and CO2 was determined on day 29.

The reference compound sodium acetate was degraded to 83% on day 29 (= 28 d of incubation).

In the toxicity control a biodegradation of 44 % was observed on day 29 (= 28 d of incubation).

The test substance was degraded to 7% on day 11 (= 10 days of incubation) where a plateau was reached.

Thus Estron-Methylether can be considered to be not readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Type of water:

freshwater