2,6-Octadienal, 3,7-dimethyl-, acid-isomerized

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:

key study

Study period:

1999-05-07 to 1999-06-04

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Justification for type of information:

The study was conducted and documented according to OECD 301 D and EU Directive 92/69 Method C.4-E.

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.4-E (Determination of the "Ready" Biodegradability - Closed Bottle Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Remarks:

secondary effluent

Details on inoculum:

- Source: secondary effluent of domestic sewage treatment plant (Kläranlage Odenthal)
- Pretreatment: 7 days aeration
- Concentration of sludge: 5 ml/L
- Water filtered: yes, to remove coarse particles

Duration of test (contact time):

28 d

Initial conc.:

2.9 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Initial concentration: 2.9 mg/L by direct weighing
- Test temperature: 20 +/- 1 °C
- Continuous darkness: yes

TEST SYSTEM
- Number of culture flasks/concentration: 2 replicates for each treatment
blank inoculum
reference substance at 2.9 mg/L
test substance at 2.9 mg/L
toxicity control at 2.9 mg/L

SAMPLING
- Sampling frequency: day 0, 7, 14, 21 and 28


CONTROL AND BLANK SYSTEM
- Inoculum blank: yes, 2 replicates
- Abiotic sterile control: no
- Toxicity control: yes, 2 replicates
- Other: reference substance

Reference substance:

benzoic acid, sodium salt

Test performance:

No unusual observations

Key result

Parameter:

% degradation (O2 consumption)

Value:

42

Sampling time:

28 d

Result of biodegradation study:

Substance	Replicate	% degradation after
		7d	14d	21d	28d
Test item	1	21	27	37	43
	2	26	29	36	41
	Mean	23.5	28.0	36.5	42.0
	std dev	2.5	1.0	0.5	1.0
Reference substance	1	68	80	84	86
	2	68	80	85	85
	Mean	68	80	85	86
	std dev	0.0	0.0	0.7	0.7
Toxicity control	1	40	47	51	55
	2	41	47	52	57
	Mean	41	47	52	56
	std dev	0.7	0.0	0.7	1.4

Within the 28 -day test period, a degradation of 42% was observed. Hence, the substance is not readily biodegradable.

The reference item, sodium benzoate, biodegraded to 80% within 14 days.

The results of the toxicity control show biodegradation up to 47 % within 14 days, hence, the test substance was not inhibitory to the inoculum at a test concentration of 2.9 mg/L.

Validity criteria fulfilled:

yes

Interpretation of results:

inherently biodegradable

Conclusions:

A closed bottle test was conducted to assess the biodegradability of the substance. A biodegradation of 42 % after 28 days incubation was observed. Thus, the pass level of 60% degradation was not met and the result of the test is not readily biodegradable. However, as the test item still degraded > 40% degradation in the Closed Bottle Test, it is a clear indication that extensive primary biodegradation has occured. Therefore the test substance is considered to be inherently biodegradable. The toxicity control shows that the test item is not inhibitory at a concentration of 2.9 mg/L.

Executive summary:

The biodegradatability of the test substance was assessed according to OECD 301 D and EU Method C.4 -E (Directive 92/69), a closed bottle test.

The test item was suspended in a mineral medium by direct weighing, inoculated with a mixed population of aquatic microorganisms from the secondary effluent of a domestic sewage treatment plant and incubated for 28 days in the dark. The biodegradation of the test substance was assessed by measuring the reduction of dissolved oxygen.

The reference substance (2.9 mg/L sodium benzoate) showed a biodegradation of 80 % fulfilling the validity criteria within 14 days . Moreover, 56 % biodegradation was observed in the toxicity control (2.9 mg/L test substance + 2.9 mg/L reference substance), indicating that the test substance was not inhibitory to the inoculum.

Within the test period of 28 days, the biodegradation of the test substance was only 42 %. The pass levels were not reached by the end of the 28-d period. Thus, the result of the ready test is "not readily biodegradable". However, as > 40% degradation were observed in the ready biodegradability test, the test substance is considered to be inherently biodegradable.

Description of key information

The biodegradability of the test item was assessed in according to OECD 301 D and EU method C.4, in a closed bottle test. A biodegradation of 42 % after 28 days incubation was observed. The test result is "not readily biodegradable".

However, as > 40% degradation were observed in the ready biodegradability test, the test substance can be considered to be inherently biodegradable.

The toxicity control shows that the test item is not inhibitory at a concentration of 2.9 mg/L.

Key value for chemical safety assessment

Biodegradation in water:

inherently biodegradable