3,7-dimethyl-6-octenyl 2-methylcrotonate

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:

26 Sep - 25 Oct 2016

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 310 (Ready Biodegradability - CO2 in Sealed Vessels (Headspace Test)

Version / remarks:

2014

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.29 (Ready Biodegradability - CO2 in Sealed Vessels (Headspace Test))

Version / remarks:

2014

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

Swiss federal office of public health consumer protection directorate notification authority for chemicals

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: activated sludge of the local waste water treatment plant, ARA Birs, Birsfelden, Switzerland
- Storage conditions: aerated with CO2-free air at room temperature
- Storage length: holding period of two days prior to use
- Preparation of inoculum for exposure: washed three times by centrifugation, decantation of the supernatant liquid phase and resuspension of the solid material in tap water and finally in mineral medium
- Concentration of sludge: 4 mg dry material per liter
- Initial cell/biomass concentration: 4 mg dry material per liter
- Water filtered: no

Duration of test (contact time):

28 d

Initial conc.:

26.4 mg/L

Based on:

test mat.

Initial conc.:

20 mg/L

Based on:

TOC

Parameter followed for biodegradation estimation:

inorg. C analysis

Details on study design:

TEST CONDITIONS
- Composition of medium: according to the guidelines; pH adjusted to 7.7 to 7.4
- Test temperature: 20 °C
- pH: 6.8 (test item bottle), 7.3 (inoculum control bottle)
- Continuous darkness: yes

TEST SYSTEM
- Test vessel: 160 mL-Wheaton glass serum bottles (total volume), sealed with aluminium crimp caps with Teflon lined chlorobutyl septa
- Culturing condition: on an orbital shaker, shaking rate of 200 rpm in a temperature-controlled environment
- Number of culture flasks/concentration: 30 bottles (test item, inoculum control), 20 bottles (reference control), 12 vessels (toxicity control), at least three bottles were measured on each sampling timepoint
- Method used to create aerobic conditions: sealed bottles with a headspace of air
- Measuring equipment: inorganic carbon (IC) measured with TOC infrared gas analyzer, equipped with an automatic sampler (i.e. vario TOC cube from Elementar Analysensysteme GmbH, Germany)
- Test item application: injected into sealed bottles containing the inoculated mineral medium using a high precision syringe

SAMPLING
- Sampling frequency: Test item and inoculum control: Exposure Day 0, 2, 5, 7, 10, 14, 21 and 28; Procedure control: Exposure Day 0, 2, 7, 14 and 28; Toxicity control: Exposure Day 0, 14 and 28;
- Sampling method: 1 mL of 7M NaOH solution injected in each bottle and shaken for 1 h at the test conditions; test and control bottles were removed from the shaker and allowed to settle; suitable volumes of the liquid phase were withdrawn and subjected to IC analysis; 3 bottles were measured on each sampling occasion and 5 bottles from each series (except the toxicity control) were analyzed at the end of the test

CONTROL AND BLANK SYSTEM
- Inoculum blank: 3 replicates per sampling time (5 replicates at test end)
- Toxicity control: 26.4 mg/L test item and 26.1 mg/L reference item (corresponding to 20 mg TOC/L and 19.2 mg TOC/L); 3 replicates per sampling time (5 replicates at test end)
- Reference control: was tested with 26.1 mg/L 1-octanol (corresponding to 19.2 mg TOC/L); 3 replicates per sampling time (5 replicates at test end)

Reference substance:

other: 1-octanol

Key result

Parameter:

% degradation (CO2 evolution)

Value:

89

Sampling time:

28 d

Remarks on result:

other: 95 % confidence interval of ± 1.0 %

Details on results:

- pass level (10% degr.) reached after 14 days
- 10-day time window was fulfilled

Results with reference substance:

Functional control (1-Octanol): 86% degradation after 14 days
Toxicity control: 100% degradation within 14 days

Table 1: Percentage Biodegradation of the Test Item and the Reference Item 1-Octanol during the Incubation Period

Time (days)	% Degradation
	Test item						Reference item
	Replicate No.						Replicate No.
	1	2	3	4	5	mean	1	2	3	4	5	mean
0	0.7	1.2	0.7	--	--	0.8	0.7	1.7	0.7	--	--	1.0
2	0.0	0.5	0.0	--	--	0.2	31.7	30.1	29.1	--	--	30.3
5	13.7	12.7	11.7	--	--	12.7	--	--	--	--	--	n.a.
7	33.6	46.1	31.6	--	--	37.1	71.2	67.6	72.2	--	--	70.3
10	59.5	50.4	57.5	--	--	55.8	--	--	--	--	--	n.a.
14	64.3	61.3	60.8	--	--	62.1	84.9	86.4	85.9	--	--	85.7
21	94.0	96.0	94.0	--	--	94.7	--	--	--	--	--	n.a.
28	88.1	88.6	90.6	88.1	89.6	89.0	98.1	97.1	98.1	94.5	92.4	96.0

(table continued below)

Time(days)	%Degradation
	Toxicity control1
	Replicate No.
	1	2	3	mean
0	1.7	0.7	1.2	1.2
2	--	--	--	n.a.
5	--	--	--	n.a.
7	--	--	--	n.a.
10	--	--	--	n.a.
14	95.3	103.1	100.5	99.6
21	--	--	--	n.a.
28	116.3	106.4	107.5	110.1

1: Based on the added TOC from the reference item only.

--: No samples taken.

n.a.: Not applicable

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

The substance was found to be readily biodegradable under the test conditions, with a mean percentage biodegradation of 89% at the end of the 28-day exposure period. The pass level for ready biodegradability (IC production of at least 60% of ThIC in a 10-day window within the 28-day test period) was reached on exposure day 14 (62%).

Description of key information

Readily biodegradable (89% within 28 d, OECD 310)

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Additional information

One experimental study is available investigating the biodegradability of the substance. The study was performed according to the OECD 310 (GLP). Non-adapted, domestic activated sludge from a sewage treatment plant was used as inoculum. After 28 d a mean degradation of 89% was recorded based on CO2-evolution (IC production increased from Day 2 until Day 21). Thus, the substance is considered to be readily biodegradable according to the OECD criteria. A toxicity control containing both, reference substance and test substance, did not indicate inhibitory effects to the inoculum (100% degradation after 14 d). All validity criteria of the study were met.