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Biodegradation in water: screening tests

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Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2018-06-12 to 2018-10-15
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Version / remarks:
1992
Deviations:
no
GLP compliance:
yes (incl. certificate)
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, non-adapted
Details on inoculum:
- Preparation of inoculum for exposure: The activated sludge was washed twice with chlorine free tap water. After the second washing the settled sludge was resuspended in mineral salts medium and was maintained in an aerobic condition by aeration with CO2 free air untii test start (2 days). The amount of inoculum used to initiate inoculation was 4.0 mL/L (25.0 mg/L dw).
Duration of test (contact time):
28 d
Initial conc.:
46 mg/L
Based on:
test mat.
Remarks:
corresponding to an oxygen demand of 51.1 mg O2/L
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: Mineral salts medium according to OECD 301 F
- Test temperature: Nominal: 20 - 24 ± 1 °C; Actual: 21.0 - 21.2 °C
- pH: 7.42 - 7.71
- pH adjusted: no
- Suspended solids concentration: 25.0 mg/L dw
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: Brown glass bottles (volume 500 mL), continuous stirring
- Number of culture flasks/concentration: -
- two for the inoculum control (C1, C2)
- one for the functional control (R1)
- two for the test item (P1, P2)
- one for the toxicity control (T1);
Separate replicates of test item and toxicity control were prepared for measurement of the pH-value at test start:
- one for the test item (PpH)
- one for the toxicity control (TpH)
- Measuring equipment:
OxiTop® OC1 10 controller with software Achat OC, WTW
OxiTop® measuring heads, WTW
Stirring platform, WTW
Climatic exposure test cabinet, RUMED RUBARTH APPARATE GMBH
pH-Meter, Multi 350i, WTW
Datalogger 174 T, TesTo
Analytical balance, SARTORlUS
Balance, KERN
Magnetic stirrer, M83000, lab 4 you
Spectralphotometer NANOCOLOR® UV/VlS, MACHEREY- NAGEL
Test Kits: Nitrat 50, Nitrit 2, all by MACHEREY-NAGEL
Multipette X-Stream, EPPENDORF
Various pipettes
- Details of trap for CO2 and volatile organics if used: A rubber sleeve with soda lime was hung into the opening of the bottles to absorb evolved CO2. The bottles were closed with OxiTop® measuring heads and the measuring system was activated.

CONTROL AND BLANK SYSTEM
- Inoculum blank: duplicate, The inoculated test medium, consisting of the required volumes of mineral medium stock solutions, ultrapure water and inoculum, was prepared in a measuring flask. 250 mL of this solution were filled in the brown glass bottles of the inoculum control, using a 250 mL measuring flask.
- Functional control: one test vessel, the reference item was weighed out and transferred into a measuring flask, the required volumes of mineral medium stock solutions, ultrapure water and inoculum, were added. 250 mL of this solution were filled in the brown glass bottle of the functional control, using a 250 mL measuring flask.
- Toxicity control: one test vessel, the test item was weighed out and directly transferred into the test vessels with 250 mL of the reference item medium, using a 250 mL measuring flask.
Reference substance:
benzoic acid, sodium salt
Key result
Parameter:
% degradation (O2 consumption)
Value:
18
Sampling time:
15 d
Key result
Parameter:
% degradation (O2 consumption)
Value:
67
Sampling time:
23 d
Key result
Parameter:
% degradation (O2 consumption)
Value:
93
Sampling time:
28 d
Key result
Parameter:
% degradation (O2 consumption)
Remarks:
second test vessel
Value:
13
Sampling time:
17 d
Key result
Parameter:
% degradation (O2 consumption)
Remarks:
second test vessel
Value:
66
Sampling time:
27 d
Key result
Parameter:
% degradation (O2 consumption)
Remarks:
second test vessel
Value:
79
Sampling time:
28 d
Results with reference substance:
% degradation on day 1: 10
% degradation on day 10: 93
% degradation on day 28: 100
The pass level for ready biodegradation (≥ 60% degradation) was reached within 3 days. The validity criterion that the degradation should be ≥ 60% after 14 d was fulfilled. Stages of Biodegradation: The adaptation phase changed to the degradation phase within 1 day (degradation > 10%), with a maximum of 100% on day 15
Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
After a test period of 28 days, the test item is classified as readily biodegradable within the 10-day-window and within the 28 day period of the study.
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Justification for type of information:
REPORTING FORMAT FOR THE ANALOGUE APPROACH
1. HYPOTHESIS FOR THE ANALOGUE APPROACH
This read-across is based on the hypothesis that source and target substances have similar biodegradation behaviour because the target substance, TA-2, exhibits the same core structure as TA-1 (source substance). TA-2 was investigated for stability in aqueous solutions by implementation of analytical methods via LC-MS/MS and LC-QToF employing ESI ionization. Based on observations resulting from these experiments, a complete hydrolysis of the test item within the mobile phase (contact time less than 1 minute for all experiments) can be assumed. This corresponds to the known reactivity (hydrolytically instability) of the sulfonyl chloride functional group of the target substance. Hydrolysis of 2-(1,3-dioxo-1,3-dihydro-2H-isoindol-2-yl)ethane-1-sulfonyl chloride (TA-2) results in its breakdown product 2-(1,3-dioxo-1,3-dihydro-2H-isoindol-2-yl)ethane-1-sulfonic acid which is also considered to be the main constituent in aqueous solutions of the source substance 2-(1,3-dioxo-1,3-dihydro-2H-isoindol-2-yl)ethane-1-sulfonic acid- potassium (TA-1) . Studies to determine biodegradation are conducted in water, thus, these studies use the hydrolysis product 2-(1,3-dioxo-1,3-dihydro-2H-isoindol-2-yl)ethane-1-sulfonic acid as active ingredient. Testing of TA-2 in aqueous solutions is therefore assumed to reveal the same results as compared to TA-1.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
The target substance, 2-(1,3-dioxo-1,3-dihydro-2H-isoindol-2-yl) ethane-1-sulfonyl chloride contains Phthalimid as core structure linked to an ethansulfonyl chloride group. Furthermore, the target substance is hydrolytically not stable and is experimentally shown to rapidly degrade to 2-(1,3-dioxo-1,3-dihydro-2H-isoindol-2-yl)ethane-1-sulfonic acid (source substance) and chloride.
The source substance 2-(1,3-dioxo-1,3-dihydro-2H-isoindol-2-yl)ethane-1-sulfonic acid--potassium is a water soluble substance for which was shown to be stable in aqueous solutions (study according to OECD guideline 201). It consists of the same core structure as the target substance (Phthalimid with sulfonic acid as functional group). TA-1 as a solid contains potassium as counter ion but when used in aqueous solutions is considered to be present as free sulfonic acid form.

3. ANALOGUE APPROACH JUSTIFICATION
The read-across hypothesis is based on the experimentally proven assumption that 2-(1,3-dioxo-1,3-dihydro-2H-isoindol-2-yl) ethane-1-sulfonyl chloride hydrolyses fast to 2-(1,3-dioxo-1,3-dihydro-2H-isoindol-2-yl)ethane-1-sulfonic acid. The source substance 2-(1,3-dioxo-1,3-dihydro-2H-isoindol-2-yl)ethane-1-sulfonic acid--potassium (TA-1) is present in the free sulfonic acid form when dissolved in aqueous solutions, thus, the tests on biodegradation and ecotoxicity are performed with the same compound regardless whether TA-1 or TA-2 is used. Furthermore, available physico-chemical data reveal similar properties for both substances supporting the read-across strategy.
The respective reliable data (RL 1) are summarised in the table below; robust study summaries are included in the Technical Dossier in the respective sections.


4. DATA MATRIX
For more detailed information please refer to the 'attached justification' section
Reason / purpose:
read-across source
Key result
Parameter:
% degradation (O2 consumption)
Value:
18
Sampling time:
15 d
Key result
Parameter:
% degradation (O2 consumption)
Value:
67
Sampling time:
23 d
Key result
Parameter:
% degradation (O2 consumption)
Value:
93
Sampling time:
28 d
Key result
Parameter:
% degradation (O2 consumption)
Value:
13
Sampling time:
17 d
Key result
Parameter:
% degradation (O2 consumption)
Value:
66
Sampling time:
27 d
Key result
Parameter:
% degradation (O2 consumption)
Value:
79
Sampling time:
28 d
Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
After a test period of 28 days, the test item (TA-1) is classified as readily biodegradable within the 10-day-window and within the 28 day period of the study.
The target substance 2 -(1,3 -dioxo-1,3 -dihydro-2H-isoindol-2 -yl)ethane-1 -sulfonyl chloride (TA-2) is hydrolytically not stable and is experimentally shown to rapidly degrade to 2 -(1,3-dioxo-1,3 -dihydro-2H-isoindol-2 -yl)ethane-1 -sulfonic acid and chloride. The source substance 2-(1,3-dioxo-1,3-dihydro-2H-isoindol-2-yl)ethane-1-sulfonic acid--potassium (TA-1) is present in the free sulfonic acid form when dissolved in aqueous solutions, thus, the tests on biodegradation and ecotoxicity are performed with the same compound regardless whether TA-1 or TA-2 is used. Therefore, the results for the source substance apply likewise to the target substance.

Description of key information

The target substance 2-(1,3-dioxo-1,3-dihydro-2H-isoindol-2-yl)ethane-1-sulfonyl chloride (TA-2) is hydrolytically not stable and is experimentally shown to rapidly degrade to 2 -(1,3 -dioxo-1,3 -dihydro-2H-isoindol-2 -yl)ethane-1 -sulfonic acid (source substance) and chloride. Therefore, the results for the source substance apply likewise to the target substance.

-Read-across: guideline study according to OECD 301F (Manometric Respirometry Test), biodegradation of 46 mg/L TA-1 was 93% at day 28 in a first experiment and 79% at day 28 in a second experiment, biodegradation was >65% within the 10 -day window, readily biodegradable

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable
Type of water:
freshwater

Additional information