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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:
04 Jul - 06 Oct 2016
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Reference:
Composition 0
Qualifier:
according to
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
Version / remarks:
1992
Deviations:
yes
Remarks:
Two temporary lapses in aeration.
Qualifier:
equivalent or similar to
Guideline:
EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)
GLP compliance:
yes
Test material information:
Composition 1
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL
- Appearance: white, waxy solid
- Source and lot/batch No.of test material: 605803
- Expiration date of the lot/batch: 31 Dec 2016
- Purity: 98.4%
- Purity test date: 25 Nov 2015

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: At room temperature
- Stability under test conditions: Substance is hydrolytically active
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge: freshly obtained activated sludge from municipal sewage treatment plant 'Waterschap Aa en Maas', 's-Hertogenbosch, The Netherlands, receiving predominantly domestic sewage.
- Preparation of inoculum for exposure: Sludge was aerated ca. 24 hours to precondition but not otherwise cultured
- Pretreatment: Before use, the sludge was allowed to settle 46 minutes and the supernatant was used as the inoculum.
- Concentration of sludge: 3.4 g/L suspended solids in the concentrated sludge
Duration of test (contact time):
28 d
Initial conc.:
21.5 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
TEST CONDITIONS
- Composition of medium: per OECD 301B
- Test temperature: 21.7 - 22.6 °C
- pH: 7.6 at start of test, 7.8-8.1 at conclusion of test
- pH adjusted: yes, from 7.7 to 7.6
- Aeration of dilution water: 80%N2/20% O2 at ca. 30-100 mL/min. Gas was sparged through 0.0125M Ba(OH)2 to trap residual CO2.
- Suspended solids concentration: 10 mL of supernatant liquor over the settled sludge was used per liter.
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: 2 litre glass brown coloured bottles. Three CO2-absorbers were connected in series to the exit air line of each test bottle. On the day of a titration, the absorber closest to the test bottle was removed, the other two absorbers advanced, and a new absorbed added to the end of series. On day 28, the test bottles were acidified with 1 mL concentrated HCL and aerated overnight to trap evolved CO2.
- Number of culture flasks/concentration: two
- Method used to create aerobic conditions: constant aeration and stirring
- Details of trap for CO2: flasks filled with 100 mL 0.0125 M Ba(OH)2

SAMPLING
- Sampling frequency: See Table 1

CONTROL AND BLANK SYSTEM
- Inoculum blank: duplicate
- Toxicity control: Reference substance plus test substance at same concentrations as Positive control and test replicates, respectively
Reference substance:
acetic acid, sodium salt
Key result
Parameter:
% degradation (CO2 evolution)
Value:
>= 3 - <= 7
Sampling time:
28 d
Remarks on result:
other:
Remarks:
Not significantly biodegraded during the test period
Details on results:
In the toxicity control, less than 25% biodegradation occurred within 14 days. Therefore, the test item might possibly inhibit microbial activity slightly. However, the production of CO2 might also have been decreased by the two breakdowns in the aeration. Therefore, it is not sure that the slightly lower CO2 production in the toxicity control was the effect of the test item or the effect of the breakdown in the aeration.
Results with reference substance:
Reference substance 33% degraded by Day 5, 67% degraded by Day 14

Table 1: CO2 evolution in the blank v. background in 0.0125 M Ba(OH)2

Day

Mean volume HCl titrated¹ in untreated Ba(OH)2 (mL)

Mean volume HCl titrated in blank (mL)

Evolved CO2

(mL HCl)

Evolved CO2

(mg)

Cumulative CO2

(mg)

2

50.94

48.00

2.94

3.2

3.2

5

50.00

46.16

3.85

4.2

7.5

7

51.11

46.44

4.68

5.1

12.6

9

51.10

47.76

3.34

3.7

16.3

14

51.16

46.10

5.06

5.6

21.8

19

49.36

44.39

4.97

5.5

27.3

23

52.49

45.36

7.13

7.8

35.2

27

52.59

46.07

6.52

7.2

42.3

29

52.39

46.73

5.67

6.2

48.6

29

52.09

49.02

3.08

3.4

51.9

29

52.07

50.71

1.36

1.5

53.4

1, Titrated with standard 0.05N HCl

Table 2: CO2 evolution and percentage biodegradation of the reference substance

Day

Mean volume HCl titrated in blank (mL)¹

Volume HCl titrated in positive control (mL)

Evolved CO2

(mL HCl)

Evolved CO2

(mg)

Cumulative CO2

(mg)

Percentage biodegradation²

2

48.00

40.67

7.33

8.1

8.1

9

5

46.16

27.81

18.35

20.2

28.2

33

7

46.44

37.23

9.21

10.1

38.4

45

9

47.76

40.06

7.69

8.5

46.8

55

14

46.10

36.44

9.66

10.6

57.5

67

1, Titrated with standard 0.05NHCl

2, Calculated as the ratio of cumulative CO2 produced and the ThCO2 of sodium acetate: 85.6 mg/ CO2/ 2L bottle

Table 3: CO2 evolution and percentage biodegradation of the test substance (Bottle A)

Day

Mean volume HCl titrated in blank (mL)¹

Volume HCl titrated in bottle A (mL)

Evolved CO2

(mL HCl)

Evolved CO2

(mg)

Cumulative CO2

(mg)

Percentage biodegradation²

2

48.00

47.20

0.80

0.9

0.9

1

5

46.16

47.76

0.00

0.0

0.9

1

7

46.44

46.68

0.00

0.0

0.9

1

9

47.76

47.16

0.59

0.7

1.5

2

14

46.10

48.25

0.00

0.0

1.5

2

19

44.39

44.01

0.38

0.4

1.9

2

23

45.36

46.43

0.00

0.0

1.9

2

27

46.07

47.46

0.00

0.0

1.9

2

29

46.73

46.57

0.16

0.2

2.1

2

29

49.02

49.40

0.00

0.0

2.1

2

29

50.71

50.50

0.20

0.2

2.3

3

1, Titrated with standard 0.05N HCl

2, Calculated as the ratio of cumulative CO2 produced and the ThCO2 of test substance: 89.0 mg/ CO2/ 2L bottle

Table 4: CO2 evolution and percentage biodegradation of the test substance (Bottle B)

Day

Mean volume HCl titrated in blank (mL)¹

Volume HCl titrated in bottle A (mL)

Evolved CO2

(mL HCl)

Evolved CO2

(mg)

Cumulative CO2

(mg)

Percentage biodegradation²

2

48.00

46.41

1.59

1.7

1.7

2

5

46.16

45.58

0.58

0.6

2.4

3

7

46.44

45.07

1.37

1.5

3.9

4

9

47.76

47.36

0.39

0.4

4.3

5

14

46.10

47.68

0.0

0.0

4.3

5

19

44.39

43.32

1.07

1.2

5.5

6

23

45.36

46.95

0.0

0.0

5.5

6

27

46.07

46.19

0.0

0.0

5.5

6

29

46.73

46.58

0.15

0.2

5.6

6

29

49.02

48.98

0.04

0.0

5.7

6

29

50.71

50.36

0.34

0.4

6.1

7

1, Titrated with standard 0.05N HCl

2, Calculated as the ratio of cumulative CO2 produced and the ThCO2 of the test substance: 89.0 mg CO2/ 2 L test bottle

Table 5: CO2 evolution and percentage biodegradation of the toxicity control

Day

Mean volume HCl titrated in blank (mL)¹

Volume HCl titrated in toxicity control (mL)

Evolved CO2

(mL HCl)

Evolved CO2

(mg)

Cumulative CO2

(mg)

Percentage biodegradation²

2

48.00

44.43

3.57

3.9

3.9

2

5

46.16

29.90

16.26

17.9

21.8

13

7

46.44

39.95

6.49

7.1

28.9

17

9

47.76

42.27

5.48

6.0

35.0

20

14

46.10

42.82

3.28

3.6

38.6

22

1, Titrated with standard 0.05N HCl

2, Calculated as the ratio of cumulative CO2 produced and the sum of the ThCO2 for test substance and sodium acetate: 173.4 mg CO2/ 2L test bottle (ThCO2 test substance: 89.0 mg CO2/2L + ThCO2 sodium acetate: 85.6 mg CO2/2L)

Validity criteria fulfilled:
yes
Remarks:
reference >60% degraded by day 14 (67%), difference in test substance degradation <20% (4%), total CO2 in blanks <40 mg/L (26.7 mg/L)
Interpretation of results:
under test conditions no biodegradation observed
Conclusions:
MTDID 15670 was not degraded under test conditions (OECD 301B)
Executive summary:

Ready biodegradability of MTDID 15670 was examined according to OECD 301B. The reference substance sodium acetate was 67% degraded by day 14. In duplicate vessels, MTDID 15670 was 3% or 7% degraded. This is not considered significant. In a toxicity control containing sodium acetate and MTDID 15670, 22% degradation was observed. However, due to aeration failure during the test, it cannot be conclusively determined whether MTDID 15670 is inhibitory (<25% degradation in the toxicity control) to activated sludge.

The test was conducted under internationally accepted test guidelines in accord with GLP criteria. Because the validity criteria for this guideline were met, the aeration failures are not expected to affect the overall conclusion of non-degradation. Therefore, the test is deemed reliable without restriction. It is suitable for Risk Assessment, Classification & Labelling, and PBT Analysis

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
(Q)SAR
Adequacy of study:
supporting study
Study period:
21May2018 to 22May2018
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
results derived from a valid (Q)SAR model, but not (completely) falling into its applicability domain, with adequate and reliable documentation / justification
Justification for type of information:
QMRF and QPRF attached
Reference:
Composition 0
Qualifier:
according to
Guideline:
other: Guidance on information requirements and chemical safety assessment: Chapter R.6: QSARs and grouping of chemicals
Deviations:
no
GLP compliance:
no
Remarks:
QSAR model
Test material information:
Composition 1
Specific details on test material used for the study:
Ethyl dodecyl sulfide, CAS# N/A, a hydrolysis product of MTDID 15670; SMILES: CCCCCCCCCCCCSCC
Duration of test (contact time):
28 d
Parameter:
% degradation (O2 consumption)
Value:
20
Sampling time:
28 d
Remarks on result:
not readily biodegradable based on QSAR/QSPR prediction
Remarks:
Catalogic301C v.08.12 Model
Parameter:
% degradation (O2 consumption)
Value:
44
Sampling time:
28 d
Remarks on result:
not readily biodegradable based on QSAR/QSPR prediction
Remarks:
Catalogic 301F v.13.16 Model result
Parameter:
% degradation (CO2 evolution)
Value:
60
Sampling time:
28 d
Remarks on result:
readily biodegradable based on QSAR/QSPR prediction
Remarks:
Catalogic 301B v.02.09 Model result
Key result
Parameter:
% degradation (O2 consumption)
Value:
52
Sampling time:
28 d
Remarks on result:
other:
Remarks:
average value of 301F and 301B model estimates
Details on results:
Catalogic OECD 301C model:
The QPRF for ethyl dodecyl sulfide reports that the chemical fulfills the general properties requirements of the model, and is in the metabolic domain of the model, but its structural fragments are indicated to be 93.33% within correctly predicted training chemicals and 6.67% not present in the training chemicals for the model, and therefore the chemical is out of the interpolation structural space. There are two related chemicals within the model's training set. These include trideclyl alcohol (CAS# 112-70-9) with an observed degradation of 88.4% BOD, and model predicted value of 100% BOD; and hexane, 1,1'-thiobis- (dihexyl sulfide CAS# 6294-31-1) with an observed degradation of 57% BOD, and model predicted value of 2% ± 2% BOD.

Catalogic OECD 301F model:
The QPRF for ethyl dodecyl sulfide reports that the chemical fulfills the general properties requirements of the model, and its structural fragments are indicated to be 93.33% within correctly predicted training chemicals and 6.67% not present in the training chemicals for the model, and therefore the chemical is out of the interpolation structural space. The chemical is not in the metabolic domain of the model. This model does not allow the user to select and display analogous chemicals present in the models training set.

Catalogic OECD 301B model:
The QPRF for ethyl dodecyl sulfide reports that the chemical fulfills the general properties requirements of the model, and its structural fragments are indicated to be 86.67% within correctly predicted training chemicals and 13.33% not present in the training chemicals for the model, and therefore the chemical is out of the interpolation structural space. The chemical is not in the metabolic domain of the model. This model does not allow the user to select and display analogous chemicals present in the models training set.
Validity criteria fulfilled:
not applicable
Conclusions:
Ethyl dodecyl sulfide has an estimated 28-day biodegradation level of 52% BOD, as an average of the predicted values from two ready biodegradability OASIS Catalogic v.5.11.17 software models.
Executive summary:

Ethyl dodecyl sulfide is identified as one of the hydrolysis products of MTDID 15670. The 28-day biodegradation level of ethyl dodecyl sulfide was estimated to be 52% BOD as an average of the predicted values from an OECD 301F, and an OECD 301B ready biodegradability model (OASIS Catalogic v.5.11.17 software). Individual 28-day model results were 20% BOD (OECD 301C model), 44% BOD (OECD 301F model), 60% CO2 evolution (OECD 301B model). The result from the 301C model was disregarded as the model failed to accurately predict the degradation of a related sulfide chemical within its training set, dihexyl sulfide which has an observed 28-day degradation of 57% BOD was estimated by the model to degrade only 2% BOD.

The software models are accepted, and valid for estimation of ready biodegradability. While the chemical is not fully in domain for the models the chemical's structural fragments are 86.67% and 93.33% represented by correctly predicted training chemicals. The estimated value for ethyl dodecyl sulfide (52% BOD after 28 days) is considered to accurately represent the molecule as persistent (P). This conclusion is pertinent to the fate of MTDID 15670 and may be used to support conclusions regarding risk analysis, classification and labelling, and PBT analysis.

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
(Q)SAR
Adequacy of study:
supporting study
Study period:
22May2018
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
results derived from a (Q)SAR model, with limited documentation / justification, but validity of model and reliability of prediction considered adequate based on a generally acknowledged source
Justification for type of information:
QMRF and QPRF attached
Reference:
Composition 0
Qualifier:
according to
Guideline:
other: Guidance on information requirements and chemical safety assessment: Chapter R.6: QSARs and grouping of chemicals
Deviations:
no
GLP compliance:
no
Remarks:
Q(SAR) model
Test material information:
Composition 1
Specific details on test material used for the study:
Crotononitrile, CAS# 4786-20-3, a hydrolysis product of MTDID 15670; SMILES: C(=CC)C(#N)
Duration of test (contact time):
28 d
Parameter:
% degradation (O2 consumption)
Value:
70
Sampling time:
28 d
Remarks on result:
readily biodegradable based on QSAR/QSPR prediction
Remarks:
Catalogic301C v.08.12 Model. Result reported as 70% (+/- 7% C.I.)
Parameter:
% degradation (O2 consumption)
Value:
82
Sampling time:
28 d
Remarks on result:
readily biodegradable based on QSAR/QSPR prediction
Remarks:
Catalogic 301F v.13.16 Model result
Parameter:
% degradation (CO2 evolution)
Value:
96
Sampling time:
28 d
Remarks on result:
readily biodegradable based on QSAR/QSPR prediction
Remarks:
Catalogic OECD 301B v.02.09 Model
Key result
Parameter:
% degradation (O2 consumption)
Value:
83
Sampling time:
28 d
Remarks on result:
readily biodegradable based on QSAR/QSPR prediction
Remarks:
Results from the three Catalogic model predictions were averaged to obtain this result. Although the models and the guidelines on which they are based, have different measures (units) for degradation, they were considered to all represent a measure of the extent of biodegradation and % BOD was chosen as the unit for the averaged result.
Details on results:
Catalogic OECD 301C model:
The QPRF for crotononitrile reports that the chemical fulfills the general properties requirements of the model, and is in the metabolic domain of the model, but its structural fragments are indicated to be 100% not present in the training chemicals for the model, and therefore the chemical is out of the interpolation structural space. Despite what is reported regarding the structural domain, there are two closely related chemicals within the model's training set. These include acrylonitrile (CAS# 107-13-1, SMILES: C=CC#N) with an observed degradation of 57% BOD, and model predicted value of 72% ± 7% BOD; and 2-propenenitrile, 2-methyl- (CAS# 126-98-7, SMILES: CC(=C)C#N) with an observed degradation of 83% BOD, and model predicted value of 62% ± 7% BOD.

Catalogic OECD 301F model:
The QPRF for crotononitrile reports that the chemical fulfills the general properties requirements of the model, and is in the metabolic domain of the model, but its structural fragments are indicated to be 60% within correctly predicted training materials and 40% not present in the training chemicals for the model, and therefore the chemical is out of the interpolation structural space. This model does not allow the user to select and display analogous chemicals present in the models training set.

Catalogic OECD 301B model:
The QPRF for crotononitrile reports that the chemical does not fulfill the general properties requirements of the model becuase the molecular weight of crotononitrile (67.1 Da) is slightly lower than the range of the model (82.1 to 737 Da), but is within the ranges for logKow and water solubiility. Crotononitirle is within the metabolic domain of the model, but its structural fragments are indicated to be 100% not present in the training chemicals for the model, and therefore the chemical is out of the interpolation structural space. This model does not allow the user to select and display analogous chemicals present in the models training set.
Validity criteria fulfilled:
not applicable
Conclusions:
Crotononitrile has an estimated 28-day biodegradation level of 83% BOD as an average of the predicted values from three ready biodegradability OASIS Catalogic v.5.11.17 software models.
Executive summary:

Crotononitrile is identified as one of the hydrolysis products of MTDID 15670. The 28-day biodegradation level of crotononitrile was estimated to be 83% BOD as an average of the predicted values from three ready biodegradability OASIS Catalogic v.5.11.17 software models. Individual 28-day model results were 70% BOD (OECD 301C model), 82% BOD (OECD 301F model), 96% CO2 evolution (OECD 301B model).

The software models are accepted, and valid for estimation of ready biodegradability. While the chemical is not fully in domain for any of the models the 301C model includes experimentally determined data for two analogous chemicals; acrylonitrile (CAS# 107-13-1, SMILES: C=CC#N) with an observed degradation of 57% BOD, and model predicted value of 72% ± 7% BOD; and 2-propenenitrile, 2-methyl- (CAS# 126-98-7, SMILES: CC(=C)C#N) with an observed degradation of 83% BOD, and model predicted value of 62% ± 7% BOD. These observed degradation values add confidence to the estimated value for crotononitrile, which is pertinent to the fate of MTDID 15670 and may be used to support conclusions regarding risk analysis, classification and labelling, and PBT analysis.

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
2006-10-23 - 2007-02-23
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study without detailed documentation
Reference:
Composition 0
Qualifier:
according to
Guideline:
OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I))
Qualifier:
according to
Guideline:
OECD Guideline 302 C (Inherent Biodegradability: Modified MITI Test (II))
Test material information:
Composition 1
Specific details on test material used for the study:
- Purity : 98.8 % (GC),
- Water solubility : 0.0819 mg/L (20 °C) (Flask method)
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge (adaptation not specified)
Duration of test (contact time):
28 d
Initial conc.:
100 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Parameter followed for biodegradation estimation:
test mat. analysis
Details on study design:
- Concentration of activated sludge : 30 mg/L
- Number of culture flasks/concentration: three
Key result
Parameter:
% degradation (O2 consumption)
Value:
57
Sampling time:
28 d
Remarks on result:
other: Mean of 43%, 65%, and 63%
Details on results:
By test material analysis (HPLC), degradation was 40%, 60%, and 62% (mean 54%).

In the subsequent inherent biodegradability test, a mean of 81% BOD (89%, 68%, and 86%) and 97% removal of test substance (100%, 92%, and 100%) was found after a 28 day contact period.

Interpretation of results:
readily biodegradable
Conclusions:
Dihexyl sulfide is readily biodegradable based on results of OECD 301C and OECD 302C tests.
Executive summary:

Dihexyl sulfide was degraded 65%, 63%, and 43% in triplicate flask in a 28-day OECD 301C test, and 89%, 86%, and 68% in a 28-day OECD 302C test. Degradation was measured as oxygen consumption. Tests were conducted far in excess of substance water solubility. Based on these results, the responsible governmental ministry concluded that dihexyl sulfide is readily biodegradable. The test was conducted according to international guidelines on behalf of a governmental body, although full details of the test were not reported. The result is relevant to a discussion of the biodegradability and persistence of sulfide esters and may be used in a weight of evidence argument on the fate of MTDID 15670.

Description of key information

MTDID 15670 was not degraded under test conditions (OECD 301B), but its hydrolysis products are expected not to be persistent.

Key value for chemical safety assessment

Additional information

Ready biodegradability of MTDID 15670 was examined according to OECD 301B. The reference substance sodium acetate was 67% degraded by day 14. In duplicate vessels, MTDID 15670 was 3% or 7% degraded. This is not considered significant. In a toxicity control containing sodium acetate and MTDID 15670, 22% degradation was observed. However, due to aeration failure during the test, it cannot be conclusively determined whether MTDID 15670 is inhibitory (<25% degradation in the toxicity control) to activated sludge. MTDID is hydrolytically active, producing crotononitrile (CAS# 4786-20-3), dodecyl ethyl sulfide (No CAS#), and tetrafluoroborate anion (tetrafluoroboric acid, CAS# 16872-11-0). Tetrafluoroborate is inorganic and not subject to biodegradation. Further considerations on biodegradability of MTDID 15670 were provided by modeling using OASIS Catalogic v5.11.17 software. The models therein are accepted and valid for estimation of ready biodegradability. The average biodegradability over three models was taken to provide a weight of evidence. Crotononitrile had an average estimated biodegradation of 83% (70% BOD in an OECD 301C model, 82% BOD in an OECD 301F model, and 96% CO2 evolution in an OECD 301B model). While crotononitrile is not fully in domain for any of the models, the 301C model includes experimentally determined data for two analogous chemicals: 1) acrylonitrile (CAS# 107-13-1) with an observed degradation of 57% BOD and model predicted value of 72% ± 7% BOD; 2) 2-propenenitrile, 2-methyl- (CAS# 126-98-7) with an observed degradation of 83% BOD, and model predicted value of 62% ± 7% BOD. These observed degradation values add confidence to the estimated value for crotononitrile. The 28-day biodegradation level of dodecyl ethyl sulfide was estimated to be 52% BOD as an average of the predicted values (OECD 301F, 44% BOD; OECD 301B, 60% CO2 evolution). The result from the 301C model was disregarded as the model failed to accurately predict the degradation of a related thioether, dihexyl sulfide, in its training set (estimated degradation, 2% BOD). However, dihexyl sulfide was degraded 65%, 63%, and 43% in triplicate flasks in a 28-day OECD 301C test, and 89%, 86%, and 68% in a 28-day OECD 302C test, with a conclusion of ready biodegradability. By multiple lines of evidence, dodecyl ethyl sulfide is expected not to be persistent.

Little direct toxicity of MTDID 15670 to activated sludge was found based on the results of an OECD 209 test. The EC10 was 139 mg/L, and the 50% effect level was not attained at a loading rate of 1000 mg/L. However, the predicted metabolic pathway for thioethers involves formation of mercaptans. Any mercaptans formed would be potentially toxic to the organism forming them. The ability to degrade MTDID 15670 hydrolysis products depends on the specific population of organisms, with the ability to use sulfides being available in most environments. Therefore, MTDID 15670 and its hydrolysis products are expected not to be persistent in the environment.