1-butyl-1,2-dihydro-6-hydroxy-4-methyl-2-oxonicotinonitrile

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

Please refer to section "Additional Information" in the Endpoint Summary for "Read Across Justification".

Reason / purpose for cross-reference:

read-across source

Key result

Parameter:

% degradation (DOC removal)

Value:

< 10

Sampling time:

28 d

Interpretation of results:

not readily biodegradable

Reference 2

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1999-10-19

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 A (Ready Biodegradability: DOC Die Away Test)

Qualifier:

according to guideline

Guideline:

EU Method C.4-A (Determination of the "Ready" Biodegradability - Dissolved Organic Carbon (DOC) Die-Away Test)

Qualifier:

according to guideline

Guideline:

ISO 7827 (Evaluation in an Aqueous Medium of the "Ultimate" Aerobic Biodegradability of Organic Compounds - Method by Analysis of Dissolved Organic Carbon (DOC))

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

Activated sludge from laboratory wastewater plants treating municipal sewage. Concentration of dry substance: 30 mg/L.

Duration of test (contact time):

28 d

Initial conc.:

90 mg/L

Based on:

test mat.

Initial conc.:

20 mg/L

Based on:

DOC

Parameter followed for biodegradation estimation:

DOC removal

Details on study design:

PRELIMINARY INVESTIGATIONS:
- TOC of the test item: 236 mg/g
- DOC of the test item: 234 mg/g

Reference substance:

aniline

Test performance:

- Physico-chemical (abiotic) elimination of the test substance: <10% DOC
- Elimination of the test substance by adsorption: <10% DOC after 5 days

VALIDITY OF THE TEST:
- Deviation of the degradation degree of the test substance in the plateau phase <20%: yes
- Degradation degree of the reference substance >70% after 14 days: yes (90-100% DOC)
- Degradation degree in the inhibition control >35 % after 14 days: yes (40-50% DOC)
The test is valid.

Key result

Parameter:

% degradation (DOC removal)

Value:

< 10

Sampling time:

28 d

Results with reference substance:

>95% degradation after 5 days

Table: DOC decrease [%]:

Day	Test substance	Reference substance	Inhibition control	Abiotic control	Adsorption control
0	0	0	0	0	0
1	0	6	-1	5	6
3	5	16	2	2	1
5	13	99	54	6	10
7	8	96	48	0	-
10	2	96	47	5	-
14	3	96	47	5	-
17	2	96	43	0	-
21	4	97	47	0	-
24	-1	95	42	-3	-
27	-1	95	46	-1	-
28	4	98	50	5	-

 

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Description of key information

 Not readily biodegradable (by OECD criteria).

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Additional information

No experimental biodegradation data are available for the substance itself. Therefore, the biodegradation potential is assessed based on data available for the close structural analogue 1-Ethyl-2-hydroxy-3-cyan-4-methylpyridon-6 (CAS 28141-13-1). This analogue differs from the substance only in that it has an ethyl- instead of a butyl-chain attached to the nitrogen atom in the pyridine ring.

The biodegradation potential of the read-across substance in water was determined in a screening study according to OECD TG 301A (DOC Die Away Test) and in compliance with GLP criteria (BASF, 1999). In this study 90 mg/L test substance (equivalent to 20 mg/L DOC) was inoculated with non-adapted activated sludge from laboratory wastewater plants treating municipal sewage for 28 days under aerobic conditions. During the incubation period the degree of biodegradation is determined as removal of dissolved organic carbon (DOC). Based on DOC measurements it was determined that after the 28-day incubation period <10% of the substance was biodegraded. Based on these findings, ethylpyridon is assessed to be not readily biodegradable.

Increased alkyl-chain length on cyclic substances is generally associated with decreased biodegradation potential of such a substance (OECD, 1993*). Therefore, it may be considered likely that the conclusion of non-ready biodegradation applies also to the target substance 1-butyl-1,2-dihydro-6-hydroxy-4-methyl-2-oxonicotinonitrile.

* OECD (1993). Environment Monograph No. 68; Structure-Activity Relationships for Biodegradation. OECD/GD(93)126; Paris