1,6-Naphthyridine-3-carboxylic acid, 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

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)

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:

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
− 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
- 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 the test item 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/L

Pre-treatment of the reference compound
Reference compound name: sodium benzoate (Acros Organics)
- 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 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
-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)
- Mixing: 1 magnetic stirrer per test vessel
- Incubation time: 28 days
- Incubation temperature: 22 ± 1 °C
- ph at end of test: 7.3 - 7.9

Reference substance:

benzoic acid, sodium salt

Remarks:

Acros Organics, purity: 99.9 %, Batch no. A0357641

Parameter:

% degradation (O2 consumption)

Value:

0

Sampling time:

28 d

Results with reference substance:

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

Validity criteria fulfilled:

yes

Remarks:

biodegradation reference compound ≥ 60 % within 14 d; degradation toxicity control > 25 % within 14 days; replicate difference ≤ 20 %; oxygen uptake of inoculum blank was ≤ 60 mg/L; no pH influence

Interpretation of results:

not readily biodegradable

Conclusions:

Within 28 days, a degradation rate of 0 % was determined for Carboxy-TH-naphthyridin. Carboxy-TH-naphthyridin is considered to be "Not Readily Biodegradable".

Executive summary:

A study was performed to assess the ready biodegradability of Carboxy-TH-naphthyridin. It 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 100 mg/L test item in a mineral medium was stirred in a closed flask and inoculated at a constant temperature (22 ± 1 °C) for up to 28 days 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. Because of the nature of biodegradation and of the mixed bacterial populations used as inoculum, determinations of test item and inoculum blank were carried out in triplicate and of reference compound in duplicate.

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 and the slope of the biodegradation curve. At the end of incubation, the pH was measured in the flasks.

The test item is an N-containing substance. Therefore, the concentration of nitrite and nitrate was determined at the start of the test. The oxygen consumed by nitrification was not determined after 28 days, because no degradation of the test item was observed.

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

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

Description of key information

A study was performed to assess the ready biodegradability of Carboxy-TH-naphthyridin. It 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).

The reference compound sodium benzoate showed 69 % degradation after 14 days. Within 28 days, a degradation rate of 0 % was determined for Carboxy-TH-naphthyridin. Carboxy-TH-naphthyridin is considered to be "Not Readily Biodegradable".

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed