Benzyl 4-[(1-butyl-5-cyano-1,6-dihydro-2-hydroxy-4-methyl-6-oxopyridin-3-yl)azo]benzoate

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

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

Adequacy of study:

key study

Study period:

15 July to 15 August, 2002

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

The justification of the read across is reported and detailed into the IUCLID section 13.

Reason / purpose for cross-reference:

read-across source

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

1992

GLP compliance:

yes (incl. QA statement)

Duration of test (contact time):

28 d

Initial conc.:

100 mg/L

Based on:

test mat.

Initial conc.:

175 - 226 mg/L

Based on:

ThOD

Remarks:

Nh4/NO3, i.e. without / with nitrification

Parameter followed for biodegradation estimation:

O2 consumption

Parameter:

% degradation (O2 consumption)

Remarks:

ThOD NH4

Value:

0 - 6

Sampling time:

28 d

Parameter:

% degradation (O2 consumption)

Remarks:

ThODNO3

Value:

0 - 5

Sampling time:

28 d

Interpretation of results:

not readily biodegradable

Conclusions:

The substance was found to be not biodegradable under the test conditions within 28 days.

Executive summary:

The test item was investigated for its ready biodegradability in a manometric respirometry test over 28 days based on EU Commission Directive 92/69/EEC, C.4-D (1992) and OECD guideline 301F (1992).

The percent biodegradation of the test item was calculated based on the theoretical oxygen demand of 1.75 mg O2/mg test item without nitrification (ThODNH4) and 2.26 mg O2/mg test item with nitrification (ThODNO3).

The biochemical oxygen demand (BOD) of the test item in the test media was within the range of the inoculum controls.

Consequently, the substance was found to be not biodegradable under the test conditions within 28 days.

In the toxicity control, containing both test item and the reference item sodium benzoate, no inhibitory effect on the biodegradation of the reference item was determined. Thus, the test item had no inhibitory effect on the activity of activated sludge microorganisms.

In the procedure controls, the reference item sodium benzoate was biodegraded by an averege of 86 % on exposure day 14, and reached an average biodegradation rate of 90 % by the end of the test (day 28), thus confìrming suitability of the activated sludge.

Description of key information

Not readily biodegradable

Key value for chemical safety assessment

Type of water:

freshwater

Additional information

The ready biodegradability potential of test substance was assessed relying on a data on structural analogue, i.e. Similar Substance 01. Details on the read across are available in section 13.

Similar Substance 01 was tested according to OECD guideline 301F and was found to be non ready biodegradable.

In general, mono-azo dyes are not expected to be ready biodegradable due to the chemical structure and the technical function. Commonly, dyes undergo a primary transformation, i.e. discolouration, due to interruption of the conjugation. However, a degradation process involves more steps and takes more time, thus such dyes are not considered readily biodegradable.

Disperse Yellow 231 was found to be inherently biodegradable in a MITI (II) test; 100 % biodegradation was seen after 14 days of exposure under aerobic conditions. However, due to the lack of details on test conditions and observations, the reliability of such data could not be ascertained.

Moreover, as reported in the Guidance on application of CLP criteria (v. 5.0 - July 2017), substances that are degraded more than 70 % in tests for inherent biodegradability (OECD guidelines 302) have the potential for ultimate biodegradation. However, because of the optimised conditions in these tests, the rapid biodegradability of inherently biodegradable substances in the environment cannot be assumed. The optimised conditions in inherent biodegradability tests stimulate adaptation of the micro-organisms thus increasing the biodegradation potential, compared to natural environments. Therefore, positive results in general should not be interpreted as evidence for rapid degradation in the environment.