2H-Azepin-2-one, hexahydro-, polymer with 1,6-diisocyanatohexane

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

2007-04-23 to 2007-07-09

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Guideline study with acceptable restrictions: high concentration of solvent, no substance specific analytical monitoring

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

(1992)

Deviations:

no

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

(1992)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

Activated sludge from the aeration tank of a wastewater plant treating predominantly domestic sewage (Wupper area water authority, STP Odenthal)
was washed twice by adding mineral medium, centrifuging (10 min at 2000 rpm and 20 °C) and decanting off the supernatant. 0.731 g of the wet sludge was dried in order to calculate the amount of wet sludge to achieve a concentration of activated sludge of 3 g/L (dry wet) suspended solids. The calculated amount of sludge was first dissolved in mineral medium, then filled up to a defined end volume and stored at room temperature under continuous shaking with aeration until use for max. 3 days.

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:

A suspension of 100 mg/L test item in a mineral medium was inoculated and incubated under aerobic conditions in the dark. The endogenous activity of the inoculum was checked running parallel blanks with inoculum but without test item. A reference compound (sodium benzoate) was run in parallel to check the operation of the procedures.
A toxicity control (test item and reference compound mixed) was run in parallel, to ensure that the chosen concentration of the test item was not inhibitory to microorganisms.
Degradation was followed by the determination of oxygen uptake and measurements were taken at frequent intervals to allow the identification of the beginning and end of biodegradation. The test lasted for 28 days.
Because of the nature of biodegradation and of the mixed bacterial populations used as inoculum, determinations of test item and reference compound are carried out in duplicate and inoculum blank in triplicate.
At the end of incubation, the pH of the contents of the flasks was measured.
The test item was an N-containing substance. Therefore, the increase in concentration of nitrite and nitrate over the test period was determined. The oxygen consumed by nitrification was calculated. This oxygen consumption by nitrification was subtracted from the respective measurements.

Reference substance:

benzoic acid, sodium salt

Test performance:

Toxicity control: 78.5% degradation after 28 days

Parameter:

% degradation (O2 consumption)

Value:

17.3

Sampling time:

7 d

Parameter:

% degradation (O2 consumption)

Value:

20.8

Sampling time:

14 d

Parameter:

% degradation (O2 consumption)

Value:

22.8

Sampling time:

21 d

Parameter:

% degradation (O2 consumption)

Value:

22.3

Sampling time:

28 d

Results with reference substance:

Reference substance: 81.7% degradation after 14 days, 89.3% degradation after 28 days

Validity criteria fulfilled:

yes

Interpretation of results:

under test conditions no biodegradation observed

Executive summary:

A solution of a 72 % solution of 2H-Azepin-2-one, hexahydro-, polymer with 1,6-diisocyanatohexane in 2-methoxy-1-methylethylacetate in a mineral medium was inoculated and incubated for 28 days under aerobic conditions. During this period, degradation was followed by BOD determinations. The test item showed:

17.3 % degradation after 7 days

20.8 % degradation after 14 days

22.8 % degradation after 21 days

22.3 % degradation after 28 days

Therefore, 2H-Azepin-2-one, hexahydro-, polymer with 1,6-diisocyanatohexane is considered to be “Not Readily Biodegradable“. The reference compound sodium benzoate showed 81.7 % degradation after 14 days. Considering ready biodegradability of the solvent 2-methoxy-1-methylethylacetate, the observed BOD is essentially due to the solvent, i.e. no degradation of the oligomer was shown.

Reference 2

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2002-08-14 to 2002-09-11

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Guideline study

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

adopted July 31, 1992

Deviations:

no

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

Commission Directive 92/69/EEC

Deviations:

no

Qualifier:

according to guideline

Guideline:

ISO DIS 9408 (Ultimate Aerobic Biodegradability - Method by Determining the Oxygen Demand in a Closed Respirometer)

Version / remarks:

Adopted 1999

Deviations:

no

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

- Source: Domestic STP D-65380 Kriftel, Mainstrasse 7-9
- Preparation of inoculum: twice 30 min sedimentation, decantation, and resuspension in mineral medium, once with filtration; centrifugation, sampling for dry weight determination, resuspension of 10 g/l in mineral medium

Duration of test (contact time):

28 d

Initial conc.:

70 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST SYSTEM
- Culturing apparatus: 500 ml flasks filled with 250 ml test solution
- Number of culture flasks per concentration:
2 with test substance and inoculum
2 with inoculum only (inoculum control)
1 with reference substance and inoculum (procedure control)
1 with test substance and 3,5-dichlorophenol (400 mg/l, abiotic control)
1 with test and reference substances and inoculum (toxicity control, only 97 ml)

METHOD OF PREPARATION OF TEST SOLUTION:
Pipetting activated sludge suspension into a volumetric flask, filling up with test water to 250 ml, addition of test / reference compounds, quantitative transfer to test apparatus

TEST CONDITIONS
- Composition of medium:
(A) Dissolved in 1000 ml deionized water:
8.50 g KH2PO4
21.75 g K2HPO4
33.40 g Na2HPO4 * 2 H2O
0.50 g NH4Cl
(B) Dissolved in 1000 ml deionized water:
36.40 g CaCl2 * H2O
(C) Dissolved in 1000 ml deionized water:
22.50 g MgSO4 * 7 H2O
(D) Dissolved in 1000 ml deionized water:
0.25 g FeCl3 * 6 H2O
1 drop of concentrated HCl
10 ml (A) + 1 ml each (B), (C), (D) in deionized water, total volume 1 liter
- Additional substrate:
10 mg/l N-allylthiourea (to prevent nitrification; not in abiotic control)
1 cm2 polytetrafluorethylene strip (required for quantitative transfer of the viscous test substance; not in abiotic and toxicity controls)
- Test temperature: 22 +/- 1 °C
- pH value: 7.3 - 7.7 both at start and end
- Concentration of suspended solids: 30 mg dry solids/l
- Other relevant factors: darkness, continuous stirring

Reference substance:

aniline

Parameter:

% degradation (O2 consumption)

Value:

0

Sampling time:

28 d

Details on results:

- Toxicity control:
41 % degradation (14 days) i.e. approx. 77 % reference compound
44 % degradation (28 days) i.e. approx. 83 % reference compound
This demonstrates that the test substance does not inhibit the microorganisms.
- Abiotic control:
Oxygen demand 0.0 = no degradation.
- Inoculum control:
Oxygen demand 9.9 mg/l (both replicates).

Results with reference substance:

8 day(s) = 67 %
14 day(s) = 84 %
28 day(s) = 89 %

Validity criteria fulfilled:

yes

Interpretation of results:

under test conditions no biodegradation observed

Conclusions:

Under the conditions of this test 2H-Azepin-2-one, hexahydro-, polymer with 1,6-diisocyanatohexane cannot be considered to be readily biodegradable.

Executive summary:

The biodegradability of 2H-Azepin-2 -one, hexahydro-, polymer with 1,6 -diisocyanatohexane was examined in a "Manometric Respirometry Test"-test according to EU-Method C.4 -D and OECD 301 F (Aventis 2002). Oxygen consumption was measured continuously (at least daily) over a period of 28 days. The test item was observed to be "not ready biodegradable" under the present test conditions (0% biodegradation within 28 days). The study was assessed as "reliable without restriction".

Description of key information

The biodegradability of 2H-Azepin-2-one, hexahydro-, polymer with 1,6-diisocyanatohexane was examined in a "Manometric Respirometry Test"-test according to EU-Method C.4 -D and OECD 301 F (Aventis 2002). Oxygen consumption was measured continuously (at least daily) over a period of 28 days. The test item was observed to be "not ready biodegradable" under the present test conditions (0% biodegradation within 28 days).
In a further test by Bayer (2007) a Manometric Respirometry Test was performed to assess the ready biodegradability of a 72 % solution of 2H-Azepin-2-one, hexahydro-, polymer with 1,6-diisocyanatohexane in 2-methoxy-1-methylethylacetate. The test item showed 22.3 % degradation after 28 days. Considering ready biodegradability of the solvent 2-methoxy-1-methylethylacetate, the observed BOD is essentially due to the solvent, i.e. no degradation of the oligomer was shown.

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed