N,N'-dithiodi-o-phenylenedibenzamide

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Remarks:

Results of abiotic assessment from surface water degradation testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

60 day degradation (performed 2016-17)

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

test procedure in accordance with generally accepted scientific standards and described in sufficient detail

Justification for type of information:

In-life work followed OECD 309 with radiolabelling at neutral pH, 12 C
Analysis performed to determine potential abiotic degradation products.

Reason / purpose for cross-reference:

reference to same study

Qualifier:

according to guideline

Guideline:

other: OECD 309

Version / remarks:

In-life followed OECD 309

Principles of method if other than guideline:

An aerobic mineralisation study was performed by Fera Science Ltd. An analytical study was also subsequently performed by Fera Science Ltd. in order to identify the transformation products formed during the mineralisation study.
The structural identities for some of the transformation products have been suggested and a transformation pathway has been proposed.
A kinetics analysis was performed by Enviresearch

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

2-Aminothiophenyl-ring-14C(U)]-DBD
Source: Hartmann Analytic
Batch number: 670-025-1201-A-20160914-JHO
Appearance: Liquid
Molecular formula: C26H20N2O2S2
Specific Activity: 120.1 mCi / mmol
Radiochemical Purity 97.1 % (taken from CofA)
Received: 29/09/2016

Radiolabelling:

yes

Analytical monitoring:

yes

Details on sampling:

Samples taken over period from Day 0 - Day 60

Buffers:

None - used natual lake water pH 7.3

Details on test conditions:

Non-sterile lake water, 12 C pH 7.3

Duration:

60 d

pH:

7.3

Temp.:

12 °C

Initial conc. measured:

ca. 24 µg/L

Remarks:

Conditions set up for water biodegradation study OECD 309

Number of replicates:

2

Positive controls:

yes

Remarks:

For biological assessment - sodium benzoate

Statistical methods:

Concentrations over varous time points (including Day 0 and Day 1) were plotted using KinGUII v2.1 to demonstrate the DT50/90.

Preliminary study:

An ‘initial mineralisation’ assessment was performed using duplicate samples.
Due to the rapid degradation a ‘repeat degradation’ assessment was performed specifically to track the degradation rate.

Test performance:

On the day after dispensing, samples were treated with the substance at either concentrations of 1 μg/L or 24 μg/L.
The experimental samples were incubated in the dark at 12±2 °C. Immediately following application and at 5 hours and 1, 2, 5, 8, 15, 20, 29, 42, 50 and 60 days for the repeat degradation assessment, samples treated at 24 μg/L were removed from incubation and analysed for radioactivity.
Sub-samples from all treated waters were quantified by LSC. Samples treated at the higher concentration of 24 μg/L were analysed by HPLC-βRAM for transformation products.

Transformation products:

yes

No.:

#1

No.:

#2

Details on hydrolysis and appearance of transformation product(s):

N-((1E)-4-oxo-2-sulfanylcyclohexa-2,5-dien-1-ylidene) benzamide, thought to be formed from cleavage of the disulfide bond with subsequent hydroxylation and oxidation
N-(2-((2-aminophenyl)disulfanyl)phenyl) benzamide, thought to be formed from biotic or abiotic cleavage of one amide function and release of benzoic acid
Details are provided in a summary report attached.

% Recovery:

ca. 42

pH:

7.3

Temp.:

12 °C

Duration:

1 d

% Recovery:

ca. 5

pH:

7.3

Temp.:

12 °C

Duration:

ca. 10 d

% Recovery:

ca. 2

pH:

7.3

Temp.:

12 °C

Duration:

ca. 60 d

Key result

pH:

7.3

Temp.:

12 °C

DT50:

ca. 1 d

Type:

(pseudo-)first order (= half-life)

Details on results:

Although there was a rapid loss of the parent compound, residues were being detected at the end of the sampling period. This is though to be in part due to adsorption / desoroption processes slowly releasing the substance from surfaces, including sediments present in the natural lake water.

Validity criteria fulfilled:

not applicable

Conclusions:

Although the data are derived from a freshwater biodegradation study using natural water, the abiotic processes demonstrate rapid hydrolysis under natural conditions, with the formation of hydrolytically stable transformation products.

Executive summary:

An aerobic mineralisation study has been performed by Fera Science Ltd. An analytical study was also subsequently performed by Fera Science Ltd. in order to identify the transformation products formed during the mineralisation study.

The structural identities for some of the transformation products have been suggested and a transformation pathway has been proposed, together with a kinetics analysis performed by Enviresearch.

Results have shown that the parent substance does not fulfil the surface water criterion for persistent (P) or for very persistent (vP) substances. Of the many transformation products that were formed during the aerobic mineralisation study, some could potentially fulfil the surface water criterion for P or for vP under the conditions of the laboratory work.

It is recognised that while some transformation products may be P and/or vP, a qualitative assessment of the transformation products indicates that they are unlikely to fulfil the criterion for bioaccumulation B and so would not be considered to be PBT and/or vPvB substances.

Description of key information

Water solubility 0.048 mg/l and screening study not technically possible.

QSAR attempted and inconclusive

Biodegradation testing (60 days radiolabelled and cold studies) resulted in conclusion that DT50 for substance is < 1 day (neutral pH), but transformation products are more stable. Results of this work provide information relating to hydrolysis and identity of transformation products.

Key value for chemical safety assessment

Half-life for hydrolysis:

1 d

at the temperature of:

12 °C

Additional information

Standard screening study not technically possible due to low water solublity.

Modelling attempted, but relevance of data is questionable.

Abiotic degradation in surface water biodegradation testing provides reliable information n half-life.