1,6-Naphthyridine-3-carboxamide, 4-(4-cyano-2-methoxyphenyl)-5-ethoxy-1,4-dihydro-2,8-dimethyl-

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

Study period:

2016

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)

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

TEST ORGANISMS:
- 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: 2016-02-01
- Concentration of inoculum: 30 mg/L suspended solids

PRE-TREATMENT OF THE INOCULUM:
- Before use, the inoculum was stored for one day at room temperature under continuous shaking with aeration
- 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

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:

STUDY PERIOD:
- Start of the experimental phase: 2016-02-01
- End of the experimental phase: 2016-05-19

PRE-TREATMENT OF THE TEST SUBSTANCE:
- 25 mg of the test item were weighed out and filled with 200 mL of mineral medium
- afterwards 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:
- 25 mg of the reference compound were weighed out and filled with 200 mL of mineral medium
- afterwards 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 filled with 200 mL of mineral medium
- afterwards the flask 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)
- Number of culture flasks/concentration: 3 (test item) 2 (reference compound), 3 (inoculum blank), 1 (toxicity control)
- Mixing: 1 magnetic stirrer per test vessel
- Test performed in closed vessels: Yes
- Incubation temperature : 22 ± 1 °C
- Test temperature: 22+/- 1°C
- pH: 6.9-7.8 (measured in the test flasks after 28 days)
- pH adjusted: no
- Aeration of dilution water: no
- Continuous darkness: yes

SAMPLING
- Sampling frequency: The BOD (in mg O2/L) was measured daily

CONTROL AND BLANK SYSTEM
- Inoculum blank: Blanks with inoculum and without test item were run in parallel (3 replicates)

Reference substance:

benzoic acid, sodium salt

Remarks:

(Acros Organics) Purity: 99.9 %; Batch-No.: A0357641

Parameter:

% degradation (O2 consumption)

Value:

6

Sampling time:

7 d

Parameter:

% degradation (O2 consumption)

Value:

7

Sampling time:

14 d

Parameter:

% degradation (O2 consumption)

Value:

8

Sampling time:

21 d

Parameter:

% degradation (O2 consumption)

Value:

8

Sampling time:

28 d

Details on results:

The toxicity control exhibited degradation rates > 25 % within 14 days.

Results with reference substance:

The reference compound sodium benzoate showed 90 % degradation after 14 days.

The oxygen consumed by nitrification was not determined at the end of the study, because no degradation of the test item was observed and the correction for oxygen uptake by nitrification would not have an influence on the results.

Validity criteria fulfilled:

yes

Remarks:

(-Ready biodegradation of reference compound ¿ 60 % within 14 days. - The 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:

Rac-Amido-TH-naphthyridin showed 8 % degradation within 28 days. The reference compound was degraded to 90% .

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 the Rac-Amido-TH-naphthyridin 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 28-day degradation was 8 % while a biodegradation of 90% was observed for the positive control (with reference substance). In conclusion the substance is not readily biodegradable under test conditions.

Description of key information

Rac-Amido-TH-naphthyridin showed 8 % degradation within 28 days. Thus, the substance is considered to be "not readily biodegradable".

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Additional information

The reference compound sodium benzoate was degraded to 90%.