2-ethylhexyl 10-ethyl-4,4-dimethyl-7-oxo-8-oxa-3,5-dithia-4-stannatetradecanoate

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

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Guideline study

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

sewage, predominantly domestic (adaptation not specified)

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Severn Trent Watr Plc sewage treatment plant at Loughborough, Leicestershire, UK
- Storage conditions: maintained on aeration in a temperature controlled room at 21 ± 1ºC overnight prior to use in the test.
- Preparation of inoculum for exposure: The sample of effluent was filtered through coarse filter paper
- Type and size of filter used, if any: coarse (first approximate 200 ml discarded)

Duration of test (contact time):

28 d

Parameter followed for biodegradation estimation:

DOC removal

Details on study design:

The following test preparations were prepared and inoculated in 500 ml bottles:
a) Four replicate bottles containing inoculated culture medium to act as the control plus 100 mg silica gel.
b) Three replicate bottles containing inoculated culture medium plus 100 mg silica gel and the reference item, aniline, at a concentration of 100 mg/l.
c) Three replicate bottles containing inoculated culture medium plus 100 mg silica gel and the test item at a concentration of 25 mg/l.
d) Two replicate bottles containing inoculated culture medium plus 100 mg silica gel the reference item, aniline, at a concentration of 100 mg/l and the test item at a concentration of 25 mg/l to act as toxicity control vessels.

All vessels were inoculated with the prepared inoculum at a rate of 1% v/v.
On Day 0, one control, and one reference item vessel were sampled for pH and DOC analysis.
The pH of all remaining control, test item, reference item and toxicity control vessels was measured prior to the vessels being placed in the CES Multi-channel Aerobic Respirometer.
The system consists of a sample flask sealed by a sensor head/CO2 trap immersed in a temperature controlled water bath. The samples were stirred for the duration of the test with a magnetically coupled stirrer.

The test was conducted in diffuse light at a temperature of 21 ± 1ºC.

On Day 28, two control and one reference item vessel were sampled for pH and DOC analysis.
The remaining vessels which were not sampled were discarded and not reported. Additional replicate vessels were prepared and incubated in order that in the event of a leak in the test system a replicate vessel could be discarded without jeopardising the integrity of the test.

Reference substance:

aniline

Parameter:

% degradation (DOC removal)

Value:

63

Sampling time:

28 d

Details on results:

The mean BOD of the inoculated culture medium (control) was 26.76 mg O2/l after 28 days.
The pH of the inoculated test vessels on Day 28 ranged from 7.8 to 7.9.
The difference between extremes of replicate BOD values at the end of the test was less than 20%.
The toxicity control attained 58% degradation after 14 days and 63% degradation after 28 days thereby confirming that the test item was not toxic to the sewage treatment micro-organisms used in the test.

Results with reference substance:

Aniline attained 69% degradation after 14 days and 74% degradation after 28 days thereby confirming the suitability of the inoculum and test conditions.
Aniline attained 94% degradation after 28 days, calculated from the results of the DOC analyses performed on Days 0 and 28. The degradation rate calculated from the results of the DOC analyses was higher than that calculated from oxygen consumption values. This is considered to be due to incorporation of the test item/aniline into the microbial biomass prior to degradation, and hence oxygen consumption, occurring.

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable, but failing 10-day window

Conclusions:

The test item attained 63% degradation after 28 days.
Despite attaining in excess of 60% degradation the test item failed to satisfy the 10 Day window validation criterion, whereby 60% degradation must be attained within 10 days of the degradation rate exceeding 10%, and therefore cannot be considered to be readily biodegradable under the strict terms and conditions of OECD Guideline No 301F. However, the test item has exhibited the potential for rapid degradation.

Executive summary:

The study was performed to assess the ready biodegradability of the test item in an aerobic aqueous media. The method followed that described in the OECD Guidelines for Testing of Chemicals (1992) No 301F, “Ready Biodegradability; Manometric Respirotry Test” referenced as method C.4-D of Commission Regulation (EC) No. 440/2008 and US EPA Fate, Transport, and Transformation Test Guidelines OPPTS 835.3110 (Paragraph (q)).

At the request of the Sponsor the test item at a concentration of 25 mg/l was exposed to sewage treatment micro-organisms with culture medium in sealed culture vessels in diffuse light at 21 ± 1ºC for 28 days. Following the recommendations of the International Standards Organisation (ISO 1995) and published literature (Handleyet al, 2002), the test item was adsorbed onto granular silica gel prior to dispersion in the test medium to aid dispersion of the test item in the test medium and to increase the surface area of the test item exposed to the test organisms.

The degradation of the test item was assessed by the measurement of daily oxygen consumption values on Days 0 to 28. Control solutions with inoculum and the reference item, aniline, together with a toxicity control were used for validation purposes.

The test item attained 63% degradation after 28 days.

Despite attaining in excess of 60% degradation, the test item failed to satisfy the 10‑Day window validation criterion, whereby 60% degradation must be attained within 10 days of the degradation rate exceeding 10%, and therefore cannot be considered to be readily biodegradable under the strict terms and conditions of OECD Guideline No 301F. However, the test item has exhibited the potential for rapid degradation.

Description of key information

The test item attained 63% degradation after 28 days in sludge according to OECD 301F.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable but failing 10-day window

Additional information

The study was performed following OECD Guidelines for Testing of Chemicals (1992) No 301F.

The test item at a concentration of 25 mg/l was exposed to sewage treatment micro-organisms with culture medium in sealed culture vessels in diffuse light at 21 ± 1 ºC for 28 days. The degradation of the test item was assessed by the measurement of daily oxygen consumption values on Days 0 to 28. 

The test item attained 63% degradation after 28 days. Despite attaining in excess of 60% degradation, the test item failed to satisfy the 10-Day window validation criterion. However, the test item has exhibited the potential for rapid degradation.