Octyl laurate

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:

08 Dec 2015 - 06 Jan 2016

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)

Version / remarks:

1992

Qualifier:

according to guideline

Guideline:

EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)

Qualifier:

according to guideline

Guideline:

EPA OPPTS 835.3110 (Ready Biodegradability)

GLP compliance:

yes (incl. QA statement)

Remarks:

Department of Health, United Kingdom

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Activated sewage sludge micro-organisms obtained on 7 December 2015 from the aeration stage of the Severn Trent Water Plc sewage treatment plant at Loughborough, Leicestershire, UK.
- Laboratory culture: no
- Storage conditions: No storage, used on the day of collection.
- Pretreatment: The activated sewage sludge sample was washed twice by settlement and resuspension in mineral medium to remove any excessive amounts of dissolved organic carbon (DOC). The washed sample was then maintained on continuous aeration in the laboratory at a temperature of approximately 21 °C.
- Suspended solids concentraiton: 3.1 g/L

Duration of test (contact time):

28 d

Initial conc.:

13 mg/L

Based on:

test mat.

Initial conc.:

10 mg/L

Based on:

TOC

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium: according to guideline
- Solubilising agent (type and concentration if used): chloroform
- Test temperature: 20-24 °C
- pH: 7.4 - 7.7
- pH adjusted: yes; adjusted to pH 7.4 ± 0.2 using diluted hydrochloric acid or sodium hydroxide solution
- Continuous darkness: yes
- Suspended solids concentration: 30 mg/L

TEST SYSTEM
- Culturing apparatus: 5 L test vessels containing 3 L of solution
- Number of culture flasks/concentration: 2
- Method used to create aerobic conditions: Approximately 24 h prior to addition of the test and reference items the vessels were filled with 2400 mL of mineral medium and 29.0 mL of inoculum and aerated overnight. The test vessels were sealed and CO2-free air bubbled through the solution at a rate of 30 to 100 mL/min per vessel and stirred continuously by magnetic stirrer.
- Measuring equipment: The samples were analyzed for IC using either a Shimadzu TOC-VCSH TOC analyzer or a Shimadzu TOC-LCSH TOC analyzer. Samples (135 or 50 μL) were injected into the IC channel of the TOC analyzer. IC analysis occurs by means of the conversion of an aqueous sample to CO2 by orthophosphoric acid or 2 M HCl using zero grade air as the carrier gas. Calibration was by reference solutions of sodium carbonate (Na2CO3). Each analysis was carried out in triplicate. The pH was measured using a Hach HQ40d Flexi handheld meter.
- Details of trap for CO2 and volatile organics if used: The CO2 produced by degradation was collected in two 500 mL Dreschel bottles containing 350 mL of 0.05 M NaOH. The CO2 absorbing solutions were prepared using purified water.
- Other: On Day 28, 1 mL of concentrated hydrochloric acid was added to each vessel to drive off any inorganic carbonates formed. The vessels were resealed, aerated overnight and the final samples taken from both absorber vessels on Day 29.

SAMPLING
- Sampling frequency: Sampled on Days 0, 2, 6, 8, 10, 14, 21, 28 and 29. The second absorber vessels were sampled on Days 0 and 29.
- Sampling method: Samples (2 mL) were taken from the first CO2 absorber vessels.

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes, two replicates
- Abiotic sterile control: no
- Toxicity control: yes, one replicate
- Procedure control: yes, two replicates

Reference substance:

benzoic acid, sodium salt

Parameter:

% degradation (CO2 evolution)

Value:

87

Sampling time:

28 d

Details on results:

The toxicity control was degraded to 87% after 14 d. Thus, it can be assumed that the test item is not inhibitory to the inoculum (degradation > 25%).

Results with reference substance:

The reference substance was degraded to 76% after 28 d thus confirming the suitability of the inoculum.

Table 1: Percentage degradation

Day	% Biodegradation
	Procedure control	Test item	Toxicity control
0	0	0	0
2	46	36	32
6	67	68	61
8	66	89	80
10	75	83	77
14	81	91	87
21	78	88	85
28	79	91	88
29	76	87	86

Table 2: Validity criteria

Criterion from the guideline	Outcome	Validity criterion fulfilled
Difference of extremes of replicate values of the removal of the test chemical at the plateau, at the end of the test or at the end of the 10-d window, as appropriate, is less than 20%.	<20%	yes
Percentage degradation of the reference compound has reached the pass levels by day 14.	81%	yes
The IC content of the test substance suspension in the mineral medium at the beginning of the test must be less than 5% of the TC, and the total CO2 evolution in the inoculum blank at the end of the test should not normally exceed 40 mg/L medium.	1-2%	yes

Validity criteria fulfilled:

yes

Remarks:

see "Any other information incl. table" for further details

Interpretation of results:

readily biodegradable

Description of key information

Readily biodegradable: 87% after 28 d (CO2 evolution, OECD 301B)

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Type of water:

freshwater

Additional information

One experimental study is available investigating the biodegradation of octyl laurate (CAS 5303-24-2). The study was performed according to OECD 301B (GLP). Activated sludge from a sewage treatment plant treating predominantly domestic sewage was used as inoculum. Biodegradation of the test item was followed for 28 d by measuring the evolution of CO2. The study included a reference substance (benzoic acid, sodium salt) as well as a toxicity control (benzoic acid, sodium salt and test item) in order to assess if the test item is inhibitory to the inoculum. On day 28, hydrochloric acid was added to the test vessels in order to stop microbial activity and to drive off any inorganic carbon. After 28 d a biodegradation of 87% was recorded. Since the 10-day window was met the substance can be considered as readily biodegradable according to the OECD criteria. The toxicity control attained 87% after 14 d assuming that the test item is not inhibitory to the inoculum.