1,6-Naphthyridine-3-carboxylic acid, 4-(4-cyano-2-methoxyphenyl)-1,4,5,6-tetrahydro-2,8-dimethyl-5-oxo-, 2-cyanoethyl ester

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:

supporting study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

Qualifier:

equivalent or similar to guideline

Guideline:

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

Deviations:

not applicable

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

Type: mixed population of aquatic microorganisms (activated sludge)
Origin: aeration tank of a wastewater plant treating predominantly domestic sewage (Wupper area water authority, WWTP Odenthal)
Date of collection: 2016-07-04
Concentration of inoculum: 30 mg/L suspended solids

Pre-treatment of the inoculum
− Before use, the inoculum was stored at room temperature under continuous stirring with aeration.
− One day before start of the test the sludge was washed twice by adding mineral medium and centrifuging for 10 min at 2000 rpm and 20 °C and decanting off the supernatant.
− An aliquot of the wet sludge was dried in order to determine the wet weight / dry weight ratio of the sludge and to prepare a stock suspension (activated sludge) of 3 g dw/L.
− The calculated amount of sludge, needed to achieve 300 mL of this stock suspension, was dissolved in mineral medium and then filled up to a defined end volume. The suspension was stored again at room temperature under continuous stirring with aeration until start of the study the next day. Evaporated mineral medium was replaced.

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:

Pre-treatment of the test item
- 25 mg of CN-Ethyl-TH-naphthyridinon were weighed out and added to the test flasks, filled with 200 mL of mineral medium
- the volume was made up to 250 mL with mineral medium containing the inoculum to give a test concentration of 100 mg test item/L

Pre-treatment of the reference compound
Reference compound name : sodium benzoate (Acros Organics)
Coding number : Ökotox_7/02
Purity : 99.9 %
Batch-no. : A0357641
Expiry date : 2018-03-27
- 25 mg of the reference compound were weighed out and added to the test flasks, filled with 200 mL of mineral medium
- the volume was made up to 250 mL with mineral medium containing the inoculum to give a test concentration of 100 mg reference compound /L

Pre-treatment of the toxicity control
- 25 mg of the test item and 25 mg of the reference compound were weighed out and added to the test flasks, filled with 200 mL of mineral medium
-volume was made up to 250 mL with mineral medium containing the inoculum to give a test concentration of 100 mg test item and reference compound/L

Exposure conditions
- Test volume: 250 mL
- Test apparatus OxiTopControl System (WTW)
- Mixing: 1 magnetic stirrer per test vessel
- Incubation time: 28 days
- Incubation temperature: 22 ± 1 °C
- Determinations of test item and inoculum blank were carried out in triplicate and of reference compound in duplicate

Reference substance:

benzoic acid, sodium salt

Key result

Parameter:

% degradation (O2 consumption)

Value:

0

Sampling time:

28 d

Parameter:

% degradation (O2 consumption)

Value:

0

Sampling time:

7 d

Parameter:

% degradation (O2 consumption)

Value:

1

Sampling time:

14 d

Parameter:

% degradation (O2 consumption)

Value:

1

Sampling time:

21 d

Details on results:

The oxygen consumed by nitrification was not determined after 28 days, because no degradation of the test item was observed.

Results with reference substance:

The reference compound sodium benzoate showed 69 % degradation after 14 days.

The pH-values after 28 days were measured to be between 7.3 -7.9.

Validity criteria fulfilled:

yes

Remarks:

reference compound reached the level of ≥ 60 percent for ready biodegradability within 14 days; toxicity control exhibited degradation rates > 25 % within 14 days; oxygen uptake of the inoculum blank was ≤ 60 mg/L

Interpretation of results:

not readily biodegradable

Conclusions:

CN-ethyl-TH-naphthyridinon showed 0 % degradation after 28 days. The reference compound sodium benzoate showed 69 % degradation after 14 days. Therefore, CN-ethyl-TH-naphthyridinon is considered to be “Not Readily Biodegradable“.

Executive summary:

The study was conducted in accordance with the Council Regulation (EC) No 440/2008, Method C.4-D “Manometric Respirometry Test“(2008). This test method is in all essential parts identical with OECD Guideline 301 F (adopted July 1992). A suspension of CN-ethyl-TH-naphthyridinon in a mineral medium was inoculated and incubated for 28 d under aerobic conditions. During this period, degradation was followed by continuous automated BOD determinations. The reference compound sodium benzoate showed 69 % degradation after 14 days. CN-ethyl-TH-naphthyridinon showed 0 % degradation after 28 days. Therefore, CN-ethyl-TH-naphthyridinon is considered to be “Not Readily Biodegradable“.

Description of key information

The study was conducted in accordance with the test method EC C.4-D “Manometric Respirometry Test“(2008), which is in all essential parts identical with OECD Guideline 301 F. A suspension of CN-ethyl-TH-naphthyridinon in a mineral medium was inoculated and incubated for 28 d under aerobic conditions. The reference compound sodium benzoate showed 69 % degradation after 14 days.

CN-ethyl-TH-naphthyridinon showed 0 % degradation after 28 days. Therefore, CN-ethyl-TH-naphthyridinon is considered to be “Not Readily Biodegradable“.

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed