Ethyl 2-methyl-4-oxo-6-pentylcyclohex-2-ene-1-carboxylate

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: inherent biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

05 June to 10 October 2014

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 302 C (Inherent Biodegradability: Modified MITI Test (II))

Deviations:

no

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Name of test material (as stated in the report): Calyxol
- Batch No. NX00006086
- Aspect: colourless to pale yellow liquid
- Expiration date of the lot/batch: September 30, 2014

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

Fresh activated sludge from a biological waste water treatment plant treating predominantly domestic sewage (Bois-de-Bay, Satigny, Switzerland) was used.
The sludge is collected in the morning, washed three times in the mineral medium (by centrifuging at 1000 g for 10 minutes, discarding the supernatant and resuspending in mineral medium) and kept aerobic until being used on the same day.

Duration of test (contact time):

70 d

Initial conc.:

30 mg/L

Based on:

test mat.

Reference substance:

other: sodium benzoate

Remarks:

99% purity

Key result

Parameter:

% degradation (O2 consumption)

Value:

18

Sampling time:

28 d

Parameter:

% degradation (O2 consumption)

Value:

23

Sampling time:

21 d

Parameter:

% degradation (O2 consumption)

Value:

36

Sampling time:

70 d

Details on results:

Oxygen uptakes, as read on the Oxitop meters, are corrected to account for the small differences between actual and nominal concentrations of test and reference substances

Results with reference substance:

Degradation of sodium benzoate exceeded 40 % after 7 days and 65 % after 14 days: the activity of the inoculum was thus verified (validity criterion).

Validity criteria fulfilled:

yes

Interpretation of results:

not inherently biodegradable

Remarks:

inherently primarily biodegradable

Conclusions:

At the test concentration Calyxol and/or its degradation products did reduce the oxygen consumption in the test flasks compared to flasks containing inoculum only (apparent negative biodegradation at beginning of test, apparent declining biodegradation from day 21). However, the inhibition of the intrinsic respiration of the inoculum was less than 20%, and therefore considered not significant.
Thus, Calyxol cannot be regarded as inherently and ultimately biodegradable according to this test. However Calyxol should be regarded as inherently primarily biodegradable according to this test method.

Executive summary:

The Inherent Biodegradability of Calyxol was determined by the Manometric Respirometry Test according to the OECD Guidelines for Testing of Chemicals, Method No. 302C.

In the test conditions Calyxol undergoes 18% biodegradation after 28 days (23% after 21 days, 36 % after 70 days).

At the test concentration Calyxol and/or its degradation products did reduce the oxygen consumption in the test flasks compared to flasks containing inoculum only (apparent negative biodegradation at beginning of test, apparent declining biodegradation from day 21). However, the inhibition of the intrinsic respiration of the inoculum was less than 20%, and therefore considered not significant.

Thus, Calyxol cannot be regarded as inherently and ultimately biodegradable according to this test. However Calyxol should be regarded as inherently primarily biodegradable according to this test method.

 

Reference 2

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

23 October 2013 to 10 February 2014

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

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

Deviations:

yes

Remarks:

An optional toxicity control as suggested by OECD guideline 301 F was not performed. The validity of the study is not adversely affected.

Qualifier:

according to guideline

Guideline:

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

Qualifier:

according to guideline

Guideline:

EPA OPPTS 835.3110 (Ready Biodegradability)

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Name of test material (as stated in the report): Calyxol
- Batch No. NX00006086
- Aspect: colourless to pale yellow liquid
- Expiration date of the lot/batch: January 03, 2014

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

Fresh activated sludge from a biological waste water treatment plant treating predominantly domestic sewage (Bois-de-Bay, Satigny, Switzerland) was used.
The sludge is collected in the morning, washed three times in the mineral medium (by centrifuging at 1000 g for 10 minutes, discarding the supernatant and resuspending in mineral medium) and kept aerobic until being used on the same day.

Duration of test (contact time):

69 d

Initial conc.:

30 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Reference substance:

other: Sodium benzoate

Remarks:

99% purity

Key result

Parameter:

% degradation (O2 consumption)

Value:

34

Sampling time:

28 d

Parameter:

% degradation (O2 consumption)

Value:

46

Sampling time:

69 d

Details on results:

Oxygen uptakes, as read on the Oxitop controller, are corrected to account for the small differences between actual and nominal concentrations of test and reference substances.
The repeatability validity criterion (not more than 20% difference between replicates) is fulfilled. Therefore, the test is considered valid.

Results with reference substance:

Degradation of sodium benzoate exceeded 40% after 7 days and 65% after 14 days: the activity of the inoculum was thus verified (validity criterion).

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

Calyxol undergoes 34% biodegradation after 28 days (46% after 69 days) in the test conditions. Calyxol did not significantly inhibit the intrinsic respiration of the inoculum at the test concentration and was therefore considered to be non-toxic to the inoculum at the test concentration. Thus, Calyxol should be regarded as not readily biodegradable according to this test.

Executive summary:

The Ready Biodegradability of Calyxol was determined by the Manometric Respirometry Test according to the OECD guideline 301F.

Calyxol undergoes 34% biodegradation after 28 days (46% after 69 days) in the test conditions. Calyxol did not significantly inhibit the intrinsic respiration of the inoculum at the test concentration and was therefore considered to be non-toxic to the inoculum at the test concentration.

Thus, Calyxol should be regarded a not readily biodegradable according to this test

Description of key information

The ready biodegradability of Calyxol has been investigated using the OECD 301F Manometric Respiratory Test. The level of biodegradation achieved after 28 days was 34%. Thus Calyxol should be regarded as not readily biodegradable according to this test.

The OECD 301F test was prolonged beyond 28 days because the curve showed that a plateau had not been reached. The level of degradation achieved after 69 days was 46% indicating significant partial degradation of Calyxol.

Similar levels of degradation were achieved in a guideline 302C inherent biodegradability test. When assessing inherent biodegradability it is not necessary to define limits on test duration. Biodegradation above 20% may be regarded as evidence of inherent, primary biodegradation, whereas biodegradation above 70% may be regarded as evidence of inherent, ultimate biodegradability. Calyxol achieved 23% degradation after 21 days and 36% after 70 days. Therefore, the substance should be regarded as inherently primarily biodegradable according to this test.

The time plot from the inherent 302C test shows a plateau of approximately 20% degradation between days 16 -24. Since Calyxol is an ester (ethyl 2 -methyl-6 -pentyl-4 -oxo-cyclohex-2 -ene carboxylate), the 20% degradation probably reflects hydrolytic cleavage of the ester function to release the carboxylic acid moiety and ethanol, the latter of which would be is rapidly mineralised. Degradation commences again from day 34 onwards, indicating that the carboxylic acid moiety undergoes further attack. This is supported by the 46% biodegradation achieved in the prolonged ready test.