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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:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Study conducted on accepted methods on the substance itself with some deficiencies in documentation, but the available information allows the conclusion that the test was properly conducted.
Qualifier:
according to
Guideline:
other: MITI-Test II
Deviations:
not specified
GLP compliance:
no
Remarks:
conducted prior to GLP implementation
Oxygen conditions:
not specified
Inoculum or test system:
not specified
Duration of test (contact time):
28 d
Initial conc.:
90 mg/L
Based on:
not specified
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST SYSTEM
- Culturing apparatus: with 333 ml fill volume

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
Reference substance:
aniline
Parameter:
% degradation (O2 consumption)
Value:
3
Sampling time:
28 d
Results with reference substance:
88% biodegradation after 28 days

Table 1: Oxygen Consumption

Time (days)

BOD

Blank (mg)

Biodegradation

Aniline (mg)

Test material (mg)

Aniline (%)

Test material (%)

0

0

0

0

0

0

7

179

13

11

78

1

14

196

17

15

84

1

21

204

21

17

87

2

27

209

23

18

88

3

28

209

24

18

88

3

Validity criteria fulfilled:
not specified
Interpretation of results:
other: not readily biodegradable
Conclusions:
The study was conducted on accepted methods, i.e. MITI-Test II, on the substance itself with some deficiencies in documentation, but the available information allows the conclusion that the test was properly conducted. The method is to be considered scientifically reasonable and suitable for the test item, the positive control showed the appropriate results. Hence, the results can be considered as reliable to assess ready biodegradability of 3-Methyl-thiazolidin-2-thion by supporting the information as provided in the key study. The test item attained 3% biodegradation after 28 days and therefore cannot be considered as readily biodegradable. This results is consistent with the one of the key study (4% degradation after 28 days), clearly showing that 3-Methyl-thiazolidin-2-thion is not readily biodegradable according to the recent OECD Guidelines.
Executive summary:

The ready biodegradability of 3-Methyl-thiazolidin-2-thion was examined at a concentration of 90 mg/L in a MITI-Test II. After 28 days, biodegradation reached 3%, determined by oxygen consumption. The positive control showed the appropriate results, i.e. 88% after 28 days. Based on the available information, 3-Methyl-thiazolidin-2-thion is not readily biodegradable.

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2015-03-11 - 2015-04-08
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Well-documented GLP guideline study without deviations on the registered substance itself
Qualifier:
according to
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Deviations:
no
Qualifier:
according to
Guideline:
EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)
Deviations:
no
Qualifier:
according to
Guideline:
EPA OPPTS 835.3110 (Ready Biodegradability)
Version / remarks:
US EPA Fate, Transport, and Transformation Test Guidelines OCSPP 835.3110 (Paragraph (q))
Deviations:
no
GLP compliance:
yes (incl. certificate)
Remarks:
THE DEPARTMENT Of HEALTH OF THE GOVERNMENT OF THE UNITED KINGDOM
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic (adaptation not specified)
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): A mixed population of sewage treatment micro-organisms was obtained on 9 March 2015 from the final effluent stage of the Severn Trent Water Pic sewage treatment plant at Loughborough, Leicestershire, UK
- Preparation of inoculum for exposure: The sample of effluent was filtered through coarse filter paper (first approximate 200 mL discarded) and maintained on aeration in a temperature controlled room at 21 ± 1 °C prior to use.
- Concentration of sludge: All vessels were inoculated with the prepared inoculum at a rate of 1% v/v.
Duration of test (contact time):
28 d
Initial conc.:
100 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: mineral medium:
Solution a
KH2PO4 8.50 g/L
K2HPO4 21.75 g/L
Na2HPO4.2H2O 33.40 g/L
NH4CI 0.50 g/L
pH = 7.4
Solution b CaCl2 27.50 g/L
Solution c MgSO4.7H2O 22.50 g/L
Solution d FeCl3.6H2O 0.25 g/L
To 1 liter (final volume) of purified water was added the following volumes of solutions a - d:
10 mL of Solution a
1 mL of Solution b
1 mL of Solution c
1 mL of Solution d
- Test temperature: 23 ± 1 °C
- pH: 7.5 - 7.9
- pH adjusted: no
- Continuous darkness: no, diffuse light

TEST SYSTEM
- Culturing apparatus: 500 mL bottles
- Number of culture flasks/concentration: 3 per test item & control, 2 per reference item an toxicity control
- Measuring equipment: CES Multi-Channel Aerobic Respirometer
The system consists of a sample flask sealed by a sensor head/C02 trap immersed in a temperature controlled water bath. The samples were stirred for the duration of the test with a magnetically coupled stirrer.
- Measuring frequency: Daily
Reference substance:
aniline
Parameter:
% degradation (O2 consumption)
Value:
4
Sampling time:
28 d
Details on results:
Results
Daily BOD values for the test item, procedure control, toxicity control and inoculum control vessels are given in Table 1. Percentage biod1gradation values of the test and reference items and the toxicity control are given in Table 2. The pH values of each individual vessel on Days 0 and 28 are given in Table 3.

Validation Criteria
The mean BOD of the inoculated mineral medium (control) was 32.11 mg O2/L after 28 days and therefore satisfied the validation criterion given in the OECD Test Guidelines.
The pH of the inoculated test item vessels on Day 28 were 7.9 and hence satisfied the validation criterion given in the OECD Test Guidelines.
The difference between extremes of replicate BOD values at the end of the test was less than 20% and therefore satisfied the validation criterion given in the OECD Test Guidelines.

Biodegradation
The test item attained 4% biodegradation after 28 days, calculated from the oxygen consumption values, and therefore cannot be considered to be readily biodegradable under the strict terms and conditions of OECD Guideline No. 301F.
The toxicity control attained 36% biodegradation after 14 days and 39% biodegradation after 28 days thereby confirming that the test item was not toxic to the sewage treatment micro-organisms used in the test.
Aniline (procedure control) attained 73% biodegradation after 14 days and 78% biodegradation after 28 days thereby confirming the suitability of the inoculum and test conditions.
Results with reference substance:
Aniline (procedure control) attained 73% biodegradation after 14 days and 78% biodegradation after 28 days thereby confirming the suitability of the inoculum and test conditions.

Table 1: Biological Oxygen Demand (BOD) Values

Day

BOD (mg O2/L)

Inoculum Control

Procedure Control

Test Item

Toxicity Control

R1

R2

R1

R2

0

0.00

0.00

0.00

0.00

0.00

0.00

1

0.00

0.00

0.00

0.00

0.00

0.00

2

2.96

5.16

5.66

5.62

5.16

5.46

3

6.12

7.78

10.58

8.62

7.38

8.00

4

7.16

8.92

113.08

10.42

9.16

47.64

5

9.00

10.28

171.80

11.92

10.28

144.40

6

10.42

12.08

201.96

13.86

11.58

180.56

7

12.54

14.70

216.82

17.16

14.78

195.58

8

13.54

15.92

225.24

18.86

16.42

201.00

9

14.74

17.28

230.40

20.78

18.28

205.30

10

15.46

17.86

233.62

21.90

19.62

208.92

11

16.24

18.74

236.44

23.16

21.08

211.34

12

16.50

18.96

238.94

23.86

22.12

213.08

13

17.28

19.86

241.94

24.94

23.70

215.20

14

17.96

20.74

244.94

26.44

25.28

217.28

15

18.78

21.78

247.74

27.58

26.86

219.20

16

19.58

22.78

251.48

28.90

28.28

220.78

17

20.58

23.86

255.74

30.20

29.90

222.70

18

21.40

24.74

258.32

31.44

31.24

224.50

19

22.04

25.74

260.22

32.40

32.52

226.32

20

22.86

26.66

262.06

33.66

33.82

228.54

21

23.62

27.54

263.26

34.56

34.90

230.82

22

24.44

28.70

265.18

35.78

36.24

233.82

23

25.48

29.66

266.60

37.02

37.32

236.44

24

26.32

30.70

267.86

38.06

38.52

238.78

25

27.32

31.82

269.18

39.28

39.74

240.82

26

28.28

32.66

270.90

40.20

40.82

242.52

27

29.12

33.56

272.44

41.32

41.98

244.06

28

29.86

34.36

273.40

42.24

42.78

245.32

 

 

Table 2: Percentage Biodegradation Values

Day

Procedure Control

Test Item

Toxicity Control

R1

R2

Mean

0

0

0

0

0

0

1

0

0

0

0

0

2

1

1

0

1

0

3

1

1

0

1

0

4

34

1

0

1

7

5

52

1

0

1

25

6

62

1

0

1

31

7

66

1

0

1

33

8

68

2

1

2

34

9

69

2

1

2

34

10

70

2

1

2

35

11

71

2

1

2

35

12

72

3

2

3

36

13

72

3

2

3

36

14

73

3

2

3

36

15

74

3

3

3

36

16

75

3

3

3

36

17

76

3

3

3

37

18

76

3

3

3

37

19

76

4

4

4

37

20

77

4

4

4

37

21

77

4

4

4

37

22

77

4

4

4

38

23

77

4

4

4

38

24

77

4

4

4

38

25

78

4

4

4

38

26

78

4

4

4

39

27

78

4

4

4

39

28

78

4

4

4

39

 

Table 3: pH Values of the Test Preparations on Days 0 and 28

Test Vessel

pH

Day 0 Pre-Adjustment

Day 28

Inoculum Control Ri

7.5

7.9

Inoculum Control R2

7.5

7.9

Procedure Control

7.5

8.1

Test Item Rt

7.5

7.9

Test Item R2

7.5

7.9

Toxicity Control

7.5

8.3

 

 

Theoretical Oxygen Demand Values

 

Calculation of Theoretical Oxygen Demand (ThOD) for the test and reference items. Test Item: 3-Methyl-thiazolidin-2-thion C4H7NS2,mol wt = 133.24

ThOD(NO3) = 16*[12+3.5+2.5+6]/93.13 = 2.40 O2/mg

Therefore for a test concentration of 100 mg/L, the ThOD will be 240 mg O2/L.

 

Reference Item (Procedure Control) : Aniline C6H5NH2,mol wt = 93.13

ThOD(NO3) = 16*[12+3.5+2.5]/93.13 = 3.09 O2/mg

Therefore, for a test concentration of 100 mg/L, the ThOD will be 309 mg O2/L.

Validity criteria fulfilled:
yes
Interpretation of results:
other: not readily biodegradable
Conclusions:
The study was conducted under GLP according to OECD 301 F without deviations on the registered substance itself. The method is to be considered scientifically reasonable and suitable for the test item, the available information allows the conclusion that the test was properly conducted, the positive control showed the appropriate results. Hence, the results can be considered as reliable to assess ready biodegradability of 3-Methyl-thiazolidin-2-thion. The test item attained 4% biodegradation after 28 days and therefore cannot be considered as readily biodegradable under the strict terms and conditions of OECD Guideline No. 301F.
Executive summary:

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

The 3-Methyl-thiazolidin-2-thion at a concentration of 100 mg/L was exposed to sewage treatment micro-organisms with mineral medium in sealed culture vessels in diffuse light at a temperature of 23 ± 1 °C for 28 days.

The biodegradation 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 4% biodegradation after 28 days and therefore cannot be considered to be readily biodegradable under the strict terms and conditions of OECD Guideline No. 301F.

Description of key information

Biodegradation in water: screening tests: Not readily biodegradable: 4% (BOD) in 28 days (OECD 301F, EU method C.4-D,  US EPA OCSPP 835.3110, GLP)
Biodegradation in water: screening tests: Not readily biodegradable: 3% (BOD) in 28 days (MITI-Test II)

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

There are two studies available to determine the ready biodegradability of 3-Methyl-thiazolidin-2-thion. The key study was assessed with Klimisch 1 (OECD 301F), the supporting (MITI-Test II) as Klimisch 2. Both studies showed consistently that 3-Methyl-thiazolidin-2-thion is not readily biodegradable (4% resp. 3% after 28 days based on BOD), leaving no doubt that the results are reliable. Hence, the endpoint is sufficiently covered, no data gaps were identified.