Isooctyl 3-mercaptopropionate

Biodegradation in water: screening tests

Administrative data

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2007-11-06 to 2007-12-11

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2008

Report date:

2008

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

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

Deviations:

yes

Remarks:

Analysis of concentration, homogeneity and stability of the test material in the test preparations were not approriate to the test guideline

Test guideline 2

Qualifier:

according to guideline

Guideline:

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

Test guideline 3

Qualifier:

according to guideline

Guideline:

EPA OPPTS 835.3110 (Ready Biodegradability)

GLP compliance:

yes (incl. QA statement)

Remarks:

The Department of Health of the Government of the United Kingdom

Test material

Test material information

Constituent 1

Reference substance name:

Isooctyl 3-mercaptopropionate

EC Number:

250-157-6

EC Name:

Isooctyl 3-mercaptopropionate

Cas Number:

30374-01-7

Molecular formula:

C11H22O2S

IUPAC Name:

2-methylheptyl 3-sulfanylpropanoate

Details on test material:

- Name of test material (as cited in study report): Isooctyl 3-mercaptopropionate (IOMP)
- Substance type: clear colourless liquid
- Physical state: liquid
- Analytical purity: no data
- Lot/batch No.: 0000020703
- Storage condition of test material: room temperature over silica gel in the dark

Study design

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): from aeration stage of the Severn Trent Water Plc sewage treatment plant at Loughborough, Leicestershire, UK, obtained 5 Nov 2007
- Method of cultivation: continuous aeration, approx. 21°C, in lab
- Storage length: 1 day
- Preparation of inoculum for exposure: activated sewage sludge sample was washed three times by settlement and resuspension in culture medium to remove any excessive amounts of DOC
- Concentration of sludge: suspended solid concentration was equal to 2.6 g/L prior to use; determination: 100 mL of washed activated sludge were filtered by suction through preweighed GF/A filter paper using a Buchner funnel. Filtration was then continued for further 3 min after rinsing the funnel three successive times with 10 mL of deionised reverse osmosis water. Filter paper was dired in an oven at approx. 105°C for at least 1 hour and allowed to cool before weighing. Process was repeated until a constant weight was attained.

Duration of test (contact time):

28 d

Initial test substance concentration

Initial conc.:

10 mg/L

Based on:

other: concentration based on test material as mg Carbon/L

Parameter followed for biodegradation estimation

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium: standard medium according to OECD guideline
- Test temperature: 21°C
- pH: 7.5 - 7.6
- pH adjusted: no
- Suspended solids concentration: 2.6 g/L prior to use
- Continuous darkness: yes


TEST SYSTEM
- Culturing apparatus: 5 L glass culture vessels containing 3L of solution
- Number of culture flasks/concentration: 2
- Method used to create aerobic conditions: Co2-free air bubbled through the solution at a rate of approx. 40 mL/min and stirred continuously. The CO2-free air was produced by passing compressed air through a glass column containing self-indicating soda lime granules
- Measuring equipment: Tekmar-Dohrmann Apollo 9000 TOC analyser, Shimadzu TOC-V(CSH) TOC Analyser
- Test performed in closed vessels: yes
- Details of trap for CO2: 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 de-gassed water.
- Other:


SAMPLING
- Sampling frequency: days 0, 1, 2, 3, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 27, 28 and 29
- Sampling method: see details on trap above
- Sample storage before analysis: immediately; samples from days 12 and 18 stored at approx. -20°C


CONTROL AND BLANK SYSTEM
- Inoculum blank: yes, duplicate
- Toxicity control: yes, single

Reference substance

Reference substance:

benzoic acid, sodium salt

Results and discussion

% Degradation

Parameter:

% degradation (CO2 evolution)

Value:

55

Sampling time:

28 d

Details on results:

Total CO2 evolution in control vessels on day 28 was 25.93 mg/L, thus the OECD validation criterion is met.

Inorganic carbon content of test material suspension in the mineral medium at start was below 5% of the TC content, thus the OECD validation criterion is met.

Difference between values for CO2 production at the end of the test for the replicate vessels was <20%, thus the OECD validation criterion is met.

Toxicity control attained 82% degradation after 14 days and 88% degradation after 28 days thereby confirming the suitability of the inoculum and test conditions

BOD5 / COD results

Results with reference substance:

82% biodegradation on day 28

Any other information on results incl. tables

The results of the degradation test are considered valid if in the same test the standard material yields > 60% degradation by Day 14.
The test material may be considered to be readily biodegradable if > 60% degradation is attained within 28 days. This level of degradation must be reached within 10 days of biodegradation exceeding 10%.
The toxicity control (test material and sodium benzoate) should attain > 25% degradation by Day 14 for the test material to be considered as non-inhibitory.
The test is considered valid if the difference of the extremes of replicate values of production of CO) at the end of the test is less than 20%.
The total CO, evolution in the control vessels at the end of the test should not normally exceed 40 mg/l medium.
The IC content of the test material suspension in the mineral medium at the beginning of the test should be < 5% of the TC.

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

Under the strict terms and conditions of OECD guideline 301B, the test material cannot be considered to be readily biodegradable.

Executive summary:

A study was performed to assess the ready biodegradability of the test material iOMP in an aerobic aqueous medium on accordance with OECD TG 301 B.

The test material, at a concentration of 10 mg Carbon/l, was exposed to activated sewage sludge micro-organisms with culture medium in sealed culture vessels in the dark at approximately 21°C for 28 days.
The degradation of the test material was assessed by the determination of carbon dioxide produced. Control solutions with inoculum and the standard material, sodium benzoate, together with a toxicity control were used for validation purposes.

For the purposes of the test a toxicity control, containing the test material and sodium benzoate, was prepared in order to assess any toxic effect of the test material on the sewage sludge microorganisms used in the test.
An amount of test material (49.5 mg) was dispersed in approximately 400 ml of culture medium and subjected to high shear mixing at approximately 7500 rpm for approximately 15 minutes prior to dispersal in inoculated culture medium. An aliquot (51.4 ml) of the sodium benzoate stock solution was also added to the test vessel and the volume adjusted to 3 litres to give a final concentration of 16.5 mg test material/l plus 17.1 mg sodium benzoate/l, equivalent to a total of 20 mg carbon/l.

The test material attained 55% degradation after 28 days and therefore cannot be considered to be readily biodegradable under the strict terms and conditions of OECD Guideline No 301B.

The toxicity control attained 82% degradation after 14 days and 84% degradation after 28 days thereby confirming that the test material was not toxic to the sewage treatment micro-organisms used in the test.