Bis(dodecylthio)dimethylstannane

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Not specified

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Reason / purpose for cross-reference:

other: read-across target

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 ± 1 °C 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 material, aniline, at a concentration of 100 mg/L.
c) Three replicate bottles containing inoculated culture medium plus 100 mg silica gel and the test material at a concentration of 25 mg/L.
d) Two replicate bottles containing inoculated culture medium plus 100 mg silica gel the reference material, aniline, at a concentration of 100 mg/L and the test material 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 material vessel were sampled for pH and DOC analysis.
The pH of all remaining control, test material, reference material 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 ± 1°C.

On Day 28, two control and one reference material 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

Key result

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 material 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 material/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 material attained 63 % degradation after 28 days.
Despite attaining in excess of 60 % degradation the test material 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 material has exhibited the potential for rapid degradation.

Executive summary:

The study was performed to assess the ready biodegradability of the test material in an aerobic aqueous media. The method followed that described in the standardised guidelines OECD 301F.

The test material was exposed to sewage treatment micro-organisms at a concentration of 25 mg/L with culture medium in sealed culture vessels in diffuse light at 21 ± 1 ºC for 28 days. The test material was adsorbed onto granular silica gel prior to dispersion in the test medium to aid dispersion of the test material in the test medium and to increase the surface area of the test material exposed to the test organisms.

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

Under the conditions of the study, the test material attained 63 % degradation after 28 days.

Despite attaining in excess of 60 % degradation, the test material 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 material has exhibited the potential for rapid degradation.

Reference 2

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Study conducted on read-across material

Justification for type of information:

Read-across to structurally similar substance DMTE (Dimethyltin bis (2-ethylhexyl thioglycolate) CAS 57583-35-4), see attached justification.

Reason / purpose for cross-reference:

read-across source

Key result

Parameter:

% degradation (DOC removal)

Value:

63

Sampling time:

28 d

Description of key information

Read-across to structurally similar substance DMTE (Dimethyltin bis (2-ethylhexyl thioglycolate) CAS 57583-35-4)

The test material attained 63 % degradation after 28 days in sludge according to OECD 301F. Despite attaining in excess of 60 % degradation, the test material failed to satisfy the 10-Day window validation criterion. However, the test material has exhibited the potential for rapid degradation.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable but failing 10-day window

Additional information

Read-across to structurally similar substance DMTE (Dimethyltin bis (2-ethylhexyl thioglycolate) CAS 57583 -35 -4)

Key study - Clarke (2013)

The study was performed to assess the ready biodegradability of the test material in an aerobic aqueous media. The method followed that described in the standardised guidelines OECD 301F, under GLP conditions. The study was awarded a reliability score of 1 in accordance with the criteria set forth by Klimisch et al. (1997).

The test material was exposed to sewage treatment micro-organisms at a concentration of 25 mg/L with culture medium in sealed culture vessels in diffuse light at 21 ± 1 ºC for 28 days. The test material was adsorbed onto granular silica gel prior to dispersion in the test medium to aid dispersion of the test material in the test medium and to increase the surface area of the test material exposed to the test organisms.

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

Under the conditions of the study, the test material attained 63 % degradation after 28 days.

Despite attaining in excess of 60 % degradation, the test material 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 material has exhibited the potential for rapid degradation.

Supporting study - Beimborn (2000)

The ready biodegradability of the test material was determined in the Manometric Respirometry Test according to OECD 301F, under GLP conditions. The study was awarded a reliability score of 1 in accordance with the criteria set forth by Klimisch et al. (1997).

This test employed biodegradation reaction mixtures containing a non-adapted activated sludge inoculum, which was suspended in a defined mineral medium at a concentration of 30 mg/L (dry solids). Mixtures of the test material, a defined inorganic medium and an inoculum were incubated and aerated in a respirometer at room temperature for 28 days. The test material was introduced into the reaction mixtures by direct addition at 50 mg/L (equivalent to 98 mg/L theoretical oxygen demand [ThOD]). The test period was expanded for up to 39 days, since the biodegradation processes were still ongoing after 28 days. The oxygen consumed during the biodegradation of the test material was continuously measured by the test apparatus. The measured biochemical oxygen demand (BOD) was compared with the calculated ThOD of the test material and indicated as biodegradation degree in per cent.

At a test material concentration of 50 mg/L and a test temperature of 22 ± 1 °C, the biodegradation after 28 days was 38 -57% (BOD of ThOD). The biodegradation after 39 days was 50 -60% (BOD of ThOD). The test material is considered primarily biodegradable but not readily biodegradable according to OECD criteria.

[Type of water: freshwater]