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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:
31 Oct 1996 to 28 Nov 1996
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Qualifier:
according to
Guideline:
EU Method C.4-B (Determination of the "Ready" Biodegradability - Modified OECD Screening Test)
Deviations:
yes
Remarks:
intial test substance concentration lower than proposed in guideline
GLP compliance:
no
Oxygen conditions:
aerobic
Inoculum or test system:
other: effluent of a laboratory scale
Details on inoculum:
- Source of effluent: south of Wupperverband
- Concentration of sewage: 0.5 mL/L
- Water filtered: yes
Duration of test (contact time):
28 d
Initial conc.:
9.03 mg/L
Based on:
DOC
Parameter followed for biodegradation estimation:
DOC removal
Details on study design:
TEST CONDITIONS
- Test temperature: 22 ± 2 °C
- Continuous darkness: yes

SAMPLING
- Sampling frequency: after 0, 7, 14, 21, 27 and 28 days

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Toxicity control: yes
Reference substance:
aniline
Parameter:
% degradation (DOC removal)
Value:
83
Sampling time:
28 d
Remarks on result:
other: 9.03 mg/L DOC
Details on results:
Please refer to "any other information on results incl. tables".
Results with reference substance:
92 % degradation after 14 days.

Table 1: DOC values of test item

9.03 mg/L DOC

DOC

 

Vessel no.

0 h

7 d

14 d

21d

27 d

28 d

 

13

a1

9.70

9.80

7.90

4.40

2.80

3.30

 

a2

10.10

9.60

6.70

4.40

2.70

3.50

 

a, mean value

9.90

9.70

7.30

4.40

2.75

3.40

 

14

b1

9.10

10.50

5.80

2.40

3.80

1.90

 

b2

10.20

10.90

5.90

2.20

3.30

2.40

 

b, mean value

9.65

10.70

5.85

2.30

3.55

2.15

 

4.10 mg/L DOC

DOC

 

Vessel no.

0 h

7 d

14 d

21d

27 d

28 d

 

15

a1

5.20

4.50

1.80

1.90

2.60

2.00

 

a2

4.40

4.60

1.80

1.80

2.90

2.20

 

a, mean value

4.80

4.55

1.80

1.85

2.75

2.10

 

16

b1

5.00

5.00

1.20

0.90

2.20

2.60

 

b2

4.80

5.60

1.30

1.30

1.70

1.80

 

b, mean value

4.90

5.30

1.25

1.10

1.95

2.20

 

2.20 mg/L DOC

DOC

 

Vessel no.

0 h

7 d

14 d

21d

27 d

28 d

 

17

a1

3.20

3.50

0.40

1.00

1.80

0.80

 

a2

2.60

3.20

1.20

1.00

1.80

0.60

 

a, mean value

2.90

3.35

0.80

1.00

1.80

0.70

 

18

b1

3.20

3.30

1.20

2.30

1.70

1.30

 

b2

2.80

4.00

2.20

3.10

1.00

1.20

 

b, mean value

3.00

3.65

1.70

2.70

1.35

1.25

 

1.10 mg/L DOC

DOC

 

Vessel no.

0 h

7 d

14 d

21d

27 d

28 d

 

19

a1

2.20

2.20

1.70

1.30

1.20

1.20

 

a2

1.40

1.90

2.00

1.40

1.90

1.10

 

a, mean value

1.80

2.05

1.85

1.35

1.55

1.15

 

20

b1

2.30

2.00

2.30

1.50

1.80

1.60

 

b2

1.50

1.90

1.10

1.40

1.50

1.80

 

b, mean value

1.90

1.95

1.70

1.45

1.65

1.70

 

Table 2: Degradation of test item (for the test concentrations 2.2 mg/L and 1.1 mg/L degradation clould not be determined as DOC values were close to the limit of detection)

9.03 mg/ DOC

% degradation

 

Vessel no.

0 h

7 d

14 d

21d

27 d

28 d

 

13

0

2

23

60

84

77

 

14

0

0

37

82

74

90

 

mean value

0

1

30

71

79

83

 

4.10 mg/ DOC

% degradation

 

Vessel no.

0 h

7 d

14 d

21d

27 d

28 d

 

15

0

6

62

72

63

80

 

16

0

0

77

90

83

78

 

mean value

0

3

69

81

73

79

 

Interpretation of results:
readily biodegradable
Conclusions:
After 28 days a degradation of 83 % was observed at concentrations of 9.03 and 4.10 mg/L DOC, respectively. Therefore the test item can be considered as ready biodegradable.
Executive summary:

The ready biodegradability of sodium p-chloro-m-cresol was investigated according to EU C. 4-B method (Modified OECD Screening Test (Müller 1996)). The effluent of a laboratory scale was treated with the test item at a concentration of 9 mg/L DOC and incubated in the dark for 28 days. As test parameter the removal of dissolved organic carbon was measured. After 28 days a degradation of 83 % was observed. Therefore, the test item can be considered as ready biodegradable.

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
23 Aug 1995 - 18 Oct 1995
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Qualifier:
according to
Guideline:
EU Method C.4-E (Determination of the "Ready" Biodegradability - Closed Bottle Test)
GLP compliance:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
other: effluent of a laboratory scale
Details on inoculum:
- Source of sewage: south of Wupperverband
- Pretreatment: 5 days aeration
- Concentration of sludge: 5 mL/L
- Water filtered: yes
Duration of test (contact time):
56 d
Initial conc.:
5.13 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Test temperature: 20 - 21 °C
- Continuous darkness: yes

SAMPLING
- Sampling frequency: after 0, 7, 14, 21, 28, 35, 42, 49 and 56 days

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Toxicity control: yes, 5.13 mg/L test item with 2.0 mg/L reference item
Reference substance:
aniline
Parameter:
% degradation (O2 consumption)
Value:
18
Sampling time:
56 d
Details on results:
A pre-test was conducted (closed bottle) a degradation of 42% was reached after 28 days.
Results with reference substance:
62 % degradation after 14 days.

Table 1: O2 concentration of test item (mg O2/L after x days)

no flasks

0 d

no flasks

7 d

no flasks

14 d

no flasks

21 d

no flasks

28 d

37

7.87

39

7.89

41

7.95

43

7.33

45

7.46

38

7.82

40

7.88

42

7.84

44

7.37

46

7.47

Mean value

7.85

 

7.89

 

7.90

 

7.35

 

7.47

no flasks

0 d

no flasks

35 d

no flasks

42 d

no flasks

49 d

no flasks

56 d

37

7.87

47

7.52

49

7.24

51

7.37

53

6.48

38

7.82

48

7.24

50

6.76

52

6.28

54

6.46

Mean value

7.85

 

7.38

 

7.00

 

6.83

 

6.47

Table 2: O2 consumption: % degradation

Test item conc.:5.13 mg/L (ThOD: 1556 mg/L)

O2 consumption

7 d

14 d

21 d

28 d

35 d

42 d

49 d

56 d

No 1: (mt0 - mtx) – (mb0 - mbx)

0.00

0.00

0.16

0.08

0.17

0.51

0.25

1.47

No 2: (mt0 - mtx) – (mb0 - mbx)

0.00

0.00

0.07

0.02

0.40

0.94

1.29

1.44

D1: % degradation

0

0

2

1

2

6

3

18

D2: % degradation

0

0

1

0

5

12

16

18

D: mean value

0

0

2

1

4

9

10

18

 Table 3: Results of pre-test

 

7 d

14 d

21 d

28 d

% degradation

0

1

0

42

 

Interpretation of results:
not readily biodegradable
Conclusions:
Under test conditions 18 % biodegradation was observed after 56 days.
Executive summary:

The ready biodegradability of sodium p-chloro-m-cresol was investigated according to EU C. 4-E method (closed bottle test (Caspers & Müller 1996). The effluent of a laboratory scale was treated with the test item at a concentration of 5.13 mg/L and incubated in the dark for 56 days. As test parameter the oxygen consumption was measured. After 56 days a degradation of 18 % was observed, therefore the test item cannot be considered as ready biodegradable. The results of the pre-test showed a degradation of 42 %.

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
13 Jun 1996 - 11 Jul 1996
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Qualifier:
according to
Guideline:
EU Method C.4-B (Determination of the "Ready" Biodegradability - Modified OECD Screening Test)
GLP compliance:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
other: effluent of a laboratory scale
Details on inoculum:
- Source of sewage: south of Wupperverband
- Concentration of sludge: 0.5 mL/L
- Water filtered: yes
Duration of test (contact time):
28 d
Initial conc.:
18 mg/L
Based on:
DOC
Parameter followed for biodegradation estimation:
DOC removal
Details on study design:
TEST CONDITIONS
- Test temperature: 22 ± 2 °C
- Continuous darkness: yes

SAMPLING
- Sampling frequency: after 0, 7, 14, 21, 27 and 28 days

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Toxicity control: yes
Reference substance:
aniline
Parameter:
% degradation (DOC removal)
Value:
0
Sampling time:
28 d
Details on results:
Please refer to "any other information on results incl. tables".
Results with reference substance:
96 % degradation after 14 days.

Table 1: DOC values of test item

Vessel no.

DOC

0 h

7 d

14 d

21d

27 d

28 d

5

a1

20.4

18.6

18.9

19.2

20.8

20.4

a2

19.2

18.9

18.3

18.1

18.9

18.9

a, mean value

19.8

18.8

18.6

18.7

19.9

19.7

6

b1

21.4

19.1

18.8

18.8

20.6

20.5

b2

20.6

18.6

18.3

18.1

20.8

20.0

b, mean value

21.0

18.9

18.6

18.5

20.7

20.3

Table 2: Degradation of test item

Vessel no.

% degradation

0 h

7 d

14 d

21d

27 d

28 d

5

0

0

0

0

0

0

6

0

1

1

6

0

0

mean value

0

1

1

3

0

0

Interpretation of results:
not readily biodegradable
Conclusions:
Under test conditions no biodegradation was observed (0 % after 28 d).
Executive summary:

The ready biodegradability of sodium p-chloro-m-cresol was also investigated according to EU C. 4 –B method (Modified OECD Screening Test (Caspers & Müller 1996)). The effluent of laboratory scale was treated with the test item at a concentration of 18 mg/L and incubated in the dark for 28 days. As test parameter the removal of dissolved organic carbon was measured. After 28 days no degradation was observed, therefore the test item cannot be considered as ready biodegradable.

Description of key information

85 % degradation (EU-method C.4-B) after 28 days (Müller 1999)

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

The biodegradability of of sodium p-chloro-m-cresolate (CAS 15733-22-9) was investigated in three biodegradation studies. To support these results in accordance to Regulation (EC) No. 1907/2006 Annex XI, 1.5 a read-across to two biodegradation studies of the source substance (p-chloro-m-cresol, CAS 59-50-7) which is the main transformation product of the target substance sodium p-chloro-m-cresolate (CAS 15733-22-9) is applied. The read-across approach is justified in detail within the analogue justification in IUCLID section 13.

The ready biodegradability of sodium p-chloro-m-cresol was investigated according to EU C. 4-B method (Modified OECD Screening Test (Müller 1996)). The effluent of a laboratory scale was treated with the test item at a concentration of 9 mg/L DOC and incubated in the dark for 28 days. As test parameter the removal of dissolved organic carbon was measured. After 28 days a degradation of 83% was observed. Therefore, the test item can be considered as ready biodegradable.

This result confirms a closed bottle test (OECD guideline 301 D) with the source substance p-chloro-m-cresol was conducted by Müller (1992) and re-evaluated by Weyers (2007). The test substance (4.5 mg/L) was incubated with effluent of a laboratory scale for a period of 28 days at 20 to 21 °C. During this period the biodegradation is followed by analysis of dissolved oxygen. The amount of oxygen taken up by the microorganisms, corrected for uptake by the blank inoculum run in parallel, is expressed as a percentage of theoretical oxygen demand (ThOD) or chemical oxygen demand (COD). After 15 days 79 % biodegradation was reached. The pass level of 60% was reached within the 10 day window, therefore under the conditions of this test, p-chloro-m-cresol can be considered to be ready biodegradable.

Further ready biodegradation studies for parent and source substance are available were the degradation degree was lower. In one study the ready biodegradability of sodium p-chloro-m-cresol was investigated according to EU C. 4-E method (closed bottle test (Caspers & Müller 1996). The effluent of a laboratory scale was treated with the test item at a concentration of 5.13 mg/L and incubated in the dark. As test parameter the oxygen consumption was measured. Due to a degradation of 42% after 28 days in a pre-test the duration of the main test was conducted with an expanded test duration time of 56 days. At the end of the 56 days test duration a degradation of 18 % was observed.  Furthermore ready biodegradability of sodium p-chloro-m-cresol was investigated according to EU C. 4 –B method (Modified OECD Screening Test (Caspers & Müller 1996)). The effluent of laboratory scale was treated with the test item at a concentration of 18 mg/L and incubated in the dark for 28 days. As test parameter the removal of dissolved organic carbon was measured. After 28 days no degradation was observed. In order to investigate the influence of inoculum activity a further test on ready biodegradability with the source substance p-chloro-m-cresol was conducted according to Draft OECD guideline, Doc. No. CDUP/89.104/13.6 (Hanstveit & Pullens, 1993), which is in general accordance with OECD 301 D (closed bottle test). Diluted activated sludge inoculum of two concentrations, i.e., 2.5 mL and 7.6 mL inoculum/L was treated with p-chloro-m-cresol at a concentration of 1.71 mg/L and incubated for 56 days. The biodegradation (BOD/COD) of p-chloro-m-cresol started between day 28 and 42 of incubation. After 56 days a biodegradation of 32% was found for the low inoculum activity (2.5 mL/L) and 52% for the high inoculum activity (7.6 mL/L). Hence, after an approximately four week adaptation period a significant degradation of the test compound could be noticed. It was postulated that p-chloro-m-cresol might have inhibited the endogenous activity of the microorganisms during the first weeks. However, based on the validity criteria of OECD guideline 301 (criteria for inhibitory substances: less than 25 % degradation in the toxicity control) p-chloro-m-cresol cannot be denoted as such. The lower rates of biodegradation measured in some ready biodegradability tests suggests that, the micro-organisms capable to degrade sodium p-chloro-m-cresol in the test system were present in insufficient numbers or were inappropriate species.

It can be concluded that sodium p-chloro-m-cresol is readily biodegradable under stringent test conditions, i.e., a high inoculum activity and/or the presence of appropriate inoculum species being able to degrade the substance. Hence, sodium p-chloro-m-cresol can be considered to be ready biodegradable.