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Biodegradation in water: screening tests

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Endpoint:
biodegradation in water: ready biodegradability
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Study period:
From August 04, 2017 to October 30, 2017
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Remarks:
KL2 due to RA
Justification for type of information:
Refer to section 13 of IUCLID for details on the read-across justification. The study with the read across substance is considered sufficient to fulfil the information requirements as further explained in the provided endpoint summary.
Reason / purpose:
read-across source
Qualifier:
according to
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Deviations:
not specified
GLP compliance:
yes (incl. certificate)
Oxygen conditions:
aerobic
Inoculum or test system:
other: activated sludge, domestic, pre-conditioned to the experimental conditions
Details on inoculum:
Test organisms
Activated sludge was obtained from Totnes Sewage Treatment Works, Totnes, Devon, UK on 23 August 2017. This works treats sewage of predominantly domestic origin. At the laboratory, the activated sludge was kept aerated at room temperature and the pH maintained at 7.0 ± 1.0. Six days prior to the exposure start the activated sludge was centrifuged, washed and re suspended in the mineral medium and the solids concentration determined. This sludge was then diluted in medium, added to test bottles and stirred until required for use. The seeded mineral medium was pre-conditioned for six days to reduce the blank oxygen uptake readings in the test.
Duration of test (contact time):
ca. 60 d
Initial conc.:
ca. 100 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
Test apparatus
The measurement of oxygen uptake was conducted in the Oxitop™ respirometers (Wissenschaftlich-Technische Werkstätten, GmbH, Germany). Each individual unit consisted of a dark glass 500 mL bottle with an OxitopÔbottle top containing a piezoresistive electronic pressure sensor. Bottles were situated on a magnetic stirrer in a constant temperature incubator. Carbon dioxide produced by microbial respiration was absorbed by potassium hydroxide solution (KOH) placed in a seal cup in the neck of each bottle, and the oxygen taken up was measured as a decrease in pressure. The Oxitop™ controller collected the pressure values from the measuring tops and calculated the BOD (as mg/L).
Reference substance:
benzoic acid, sodium salt
Remarks:
100 mg/L
Test performance:
Validity Criteria
The validity requirements of the OECD guideline state:
1) The difference between extremes of replicate biodegradation values should be less than 20% at the end of 10-day window, at the plateau or at the end of the test;
2) The positive control should achieve > 60% biodegradation by Day 14.
3) The oxygen consumption of the inoculum blank should not exceed 60 mg/L in 28 days.

Mean oxygen uptake of the inoculum blank was below 60 mg/L, as required in the OECD guideline. The difference between replicate test substance extremes was < 20% after the 10-d window, at plateau, and on Day 60. Sodium benzoate reached a mean 74% biodegradation by Day 14. The average of the mean oxygen consumed in the inoculum blanks was 6.9 mg/L after 28 d and 8.4 mg/L after 60 d. Therefore, this test has satisfied all the validity criteria.
Key result
Parameter:
% degradation (O2 consumption)
Remarks:
Test substance
Value:
ca. 40
Sampling time:
28 d
Remarks on result:
other: <60% Biodegradation confirmed that the test substance cannot be classified as readiily biodegradable. Hence it is classified as Inherently biodegradable
Key result
Parameter:
% degradation (O2 consumption)
Remarks:
Reference substance
Value:
ca. 74
Sampling time:
14 d
Remarks on result:
other: >60% Biodegradability confirmed that the activated sludge contained viabale organism
Key result
Parameter:
% degradation (O2 consumption)
Remarks:
Toxicity control
Value:
ca. 40
Sampling time:
14 d
Remarks on result:
other: >25% Biodegradability confirmed that the test substance is assumed not to be inhibitory at used concentration
Details on results:
pH and temperature measurements
At the end of the 60-d test period, the pH values were 7.3 in the inoculum blank bottles, ranged from 6.7 to 7.0 in the sodium benzoate bottles, from 6.9 to 7.0 in the test substance bottlesand from 6.7 to 6.9 in the toxicity control bottles. Temperature measurements recorded in several of the test bottles on Days 0 and 60 indicated the temperature was within the range 22 ± 1°C. Continuous monitoring of the incubator temperature showed it to have remained within the range 22 ± 1°C throughout the study.
Results with reference substance:
Theoretical oxygen demand (ThOD)
The ThOD of sodium benzoate was calculated as 1.67 g O2/g of substance, using the formula given in the OECD guideline. Biodegradation of sodium benzoate has been calculated on the basis of calculated ThOD.

Biochemical oxygen demand (BOD)
The results for the reference substance did show that sodium benzoate attained a mean level of biodegradation (based on the BOD:ThOD ratio) of 86%, and the results showed good replication. More than 60% degradation was achieved within the 10-day window as expected for a biodegradable substance, thus confirming that the activated sludge contained viable organisms.

Results

Theoretical oxygen demand (ThOD)

The ThOD of sodium benzoate was calculated as 1.67 g O2/g of substance, using the formula given in the OECD guideline. Biodegradation of sodium benzoate has been calculated on the basis of calculated ThOD.

Chemical oxygen demand (COD)

The measured COD value of test substance was 1.50 g O2/g of substance, and its biodegradation was calculated on the basis of measured COD.

Biochemical oxygen demand (BOD)

The results for the reference substance did show that sodium benzoate attained a mean level of biodegradation (based on the BOD:ThOD ratio) of 86%, and the results showed good replication. More than 60% degradation was achieved within the 10-d window as expected for a biodegradable substance, thus confirming that the activated sludge contained viable organisms.

Biodegradation results – Reference Substance

Day

Sodium benzoate (blank corrected) BOD (mg/L)

BODa(g O2/g)

Biodegradationb(%)

Rep 1

Rep 2

Rep 3

Rep 1

Rep 2

Rep 3

Rep 1

Rep 2

Rep 3

Mean

7

96.5

119

122

0.97

1.19

1.22

58

71

73

67

14

109

131

134

1.09

1.31

1.34

65

78

80

74

21

109

137

135

1.09

1.37

1.35

65

82

81

76

28

114

136

136

1.14

1.36

1.36

68

81

81

77

35

116

141

141

1.16

1.41

1.41

69

84

84

79

42

115

143

140

1.15

1.43

1.40

69

86

84

80

49

114

148

145

1.14

1.48

1.45

68

89

87

81

56

110

152

152

1.10

1.52

1.52

66

91

91

83

60

116

158

155

1.16

1.58

1.55

69

95

93

86

BOD:   Biological Oxygen Demand

a       BOD (g O2/g) =Blank corrected biodegradation (mg/L)         

                  Sodium benzoate concentration (100 mg/L)

b  Biodegradation (%) =Biological Oxygen Demand (g O2/g)× 100

                                                ThOD (1.67 g O2/g)

The following phases (approximate) were observed:

Phase

Time period

Lag phase

Days 0 to 1

Degradation phase

Days 1 to 18

10-day window

Days 1 to 11

 

The results for test substance did show that test substance attained a mean level of biodegradation (based on the BOD:COD ratio) of 40% after 28 d and 64% after 60 d, and the results showed good replication. Less than 60% degradation was achieved within 28 d, so test substance cannot be classified as readily biodegradable.

Biodegradation results – Test substance

Day

Test substance (blank corrected) BOD (mg/L)

BODa(g O2/g)

Biodegradationb(%)

Rep 1

Rep 2

Rep 3

Rep 1

Rep 2

Rep 3

Rep 1

Rep 2

Rep 3

Mean

7

9.3

14.9

14.9

0.09

0.15

0.15

6

10

10

9

14

35.3

32.5

35.3

0.35

0.33

0.35

23

22

23

23

21

50.7

47.9

50.7

0.51

0.48

0.51

34

32

34

33

28

60.6

55.0

60.6

0.61

0.55

0.61

41

37

41

40

35

70.6

65.0

65.0

0.71

0.65

0.65

47

43

43

44

42

80.7

72.3

72.3

0.81

0.72

0.72

54

48

48

50

49

88.5

80.0

77.2

0.89

0.80

0.77

59

53

51

54

56

95.9

87.4

87.4

0.96

0.87

0.87

64

58

58

60

60

102

92.6

92.6

1.02

0.93

0.93

68

62

62

64

BOD:   Biological Oxygen Demand

a       Biological oxygen demand (g O2/g) =Blank corrected biodegradation (mg/L)

                                                      Substance concentration (100 mg/L)

b  Biodegradation (%) =Biological Oxygen Demand (g O2/g)× 100

                                                COD (1.50 g O2/g)

The following phases (approximate) were observed:

Phase

Time period

Lag phase

Days 0 to 7

Degradation phase

Days 7 to 49

Combined ThOD/COD for toxicity control

The mean toxicity control degradation achieved on Day 14 was 40% (based on combined ThOD/COD), as this was > 25% the test substance was assumed not to be inhibitory at this concentration.

Biodegradation results – Toxicity Control

Day

Toxicity control (blank corrected) BOD (mg/L)

BODa(g O2/g)

Biodegradationb(%)

Rep 1

Rep 2

Rep 3

Rep 1

Rep 2

Rep 3

Rep 1

Rep 2

Rep 3

Mean

7

111

105

108

0.56

0.53

0.54

35

33

34

34

14

125

117

131

0.63

0.59

0.66

40

37

42

40

21

137

126

143

0.69

0.63

0.72

43

40

45

43

28

148

139

153

0.74

0.70

0.77

47

44

48

46

35

161

147

161

0.81

0.74

0.81

51

47

51

50

42

168

157

171

0.84

0.79

0.86

53

50

54

52

49

173

170

176

0.87

0.85

0.88

55

53

55

54

56

180

180

183

0.90

0.90

0.92

57

57

58

57

60

186

186

186

0.93

0.93

0.93

58

58

58

58

BOD:   Biological Oxygen Demand

a       Biological oxygen demand (g O2/g) =Blank corrected biodegradation (mg/L)

                                                      Toxicity control concentration (200 mg/L)

b  Biodegradation (%) =Biological Oxygen Demand (g O2/g)× 100

                                    Combined ThOD/COD (1.59 g O2/g)

Validity criteria fulfilled:
yes
Interpretation of results:
inherently biodegradable
Conclusions:
Based on the results of the read across study, the test substance, is considered as inherently biodegradable.
Executive summary:

A study was conducted to determine the ready biodegradability of the read across substance, 'mono- and di- C16 PSE, K+ and H3PO4' (purity: 100%), using Manometric respirometry method, according to OECD Guideline 301F, in compliance with GLP. Following the pre-conditioning, the test bottles containing prepared activated sludge inoculum in mineral medium were set up for the test according to the experimental design. In the study, Inoculum blanks, positive control (sodium benzoate at 100 mg/L), test substance (100 mg/L) as well as toxicity controls (test and reference substances, both at 100 mg/L), each these group bottles were prepared in triplicate, except inoculum blanks which were prepared in duplicate. Additional single replicate test substance and toxicity control bottles were prepared for determination of pH at Day 0, so undissolved test substance was not removed by the pH probe. Oxygen uptake was recorded automatically every 240 minutes during the 60 d experimental period. Oxygen uptake values were corrected for the inoculum blank and the biodegradation was calculated as a percentage of the chemical oxygen demand (COD) for the substance under test and as a percentage of the theoretical oxygen demand (ThOD) for the reference substance. The chemical oxygen demand (COD) of test substance was determined using spectrophotometer for evaluation. The test substance attained a mean level of biodegradation (based on the BOD:COD ratio) of 40% after 28 d and 64% after 60 d. The test substance results showed good replication. Less than 60% degradation was achieved within 28 d, so test substance was classified as inherently biodegradable. Sodium benzoate attained a mean level of biodegradation (based on the BOD:ThOD ratio) of 86%, and the results showed good replication. More than 60% degradation was achieved within the 10-d window as expected for a biodegradable substance, thus confirming that the activated sludge contained viable organisms. The mean toxicity control degradation achieved on Day 14 was 40% (based on combined ThOD/COD), as this was > 25% the test substance was assumed not to be inhibitory at this concentration. The test met all the all validity criteria. Under the study conditions, the read across substance was considered to be inherently biodegradable (Scymaris, 2017). Based on the results of the read across study, a similar inherent biodegradation potential can be considered for the test substance, 'mono- and di- C16 PSE, K+ and C16 -18-OH'.

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Study period:
From October 24, 2017 to November 24, 2017
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
KL2 due to RA
Justification for type of information:
Refer to section 13 of IUCLID for details on the read-across justification. The study with the read across substance is considered sufficient to fulfil the information requirements as further explained in the provided endpoint summary.
Reason / purpose:
read-across source
Qualifier:
according to
Guideline:
OECD Guideline 310 (Ready Biodegradability - CO2 in Sealed Vessels (Headspace Test)
Deviations:
not specified
GLP compliance:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
other: Aerobic sludge, mixed treatment plant of urban (66%) and industrial (34%)
Details on inoculum:
Method of mud sampling
For the preparation of the inoculum a sample of aerobic sludge has been selected by the mixed treatment plant of urban (about 66%) and industrial (about 34%) liquid sewage situated at San Rocco - Monza (MB), Italia. The plant of treatment is managed by "BRIANZACQUE SRL (Monza)".

Mud preparation
In the laboratory the sampled muds, have been mixed and let settle, keeping them in aerobic conditions. The mud samples, before their use, have been analysed to check its ability to form colony units. Then it has been centrifuged, washed and analyzed to quantify the suspended solids concentration for the inoculum preparation. The inoculum was prepared in order to have a concentration of suspended solid of about 4 mg/L.

Medium preparation:

Solution A
Anhydrous potassium dihydrogen phosphate (KH2P04): 8.50 g/L
Anhydrous dipotassium hydrogen phosphate (K2HP04): 21.75 g/L
Disodium hydrogen phosphate dihydrate (Na2HP04.2H20): 33.40 g/L
Ammonium chloride (NH4Cl): 0.50 g/L
pH = 7.53

Solution B
Calcium chloride dihydrate (CaCI2.2H20): 36.40 g/L

Solution C
Magnesium sulphate heptahydrate (MgSO4.7H20): 22.50 g/L

Solution D
Iron chloride (Ill) hexahydrate (FeCl3.6H20): 0.25 g/L
All solutions has been made with deionized water (MilliQ Millipore). Then for each litre of medium 10 mL of Solution A have been transferred into a 1000 mL volumetric flask and diluted with 800 mL of deionised water; 1 mL of Solution B, 1 mL of Solution C and 1 mL of Solution D have been added and the solution has been diluted to volume with deionised water. For higher volumes the medium has been prepared according to the same proportion. The preparation of the solutions has been reported in an internal laboratory logbook.

Duration of test (contact time):
ca. 28 d
Initial conc.:
ca. 39.73 mg/L
Based on:
TOC
Parameter followed for biodegradation estimation:
inorg. C analysis
Reference substance:
benzoic acid, sodium salt
Remarks:
18.61 mg/L of TOC
Key result
Parameter:
% degradation (inorg. C analysis)
Remarks:
Test substance
Value:
ca. 118
Sampling time:
28 d
Remarks on result:
other: Readily biodegradable
Results with reference substance:
Percentage biodegradation of reference substance at 14 d was determined to be 101%, therefore the assay fulfilled the validity criteria.

Results

Quality criteria of the test were satisfied. The mean amount of TIC present in the blank controls at the end of the test was < 3 mg C/L. The trend of the inorganic carbon and related biodegradation percentages in the bottle contained both the test sample and the reference substance confirm the absence of inhibitory effect of the test sample on inoculum. The biodegradation percentage of the test substance during the test was as follow:

Check point (d)

% of Biodegradation

Reference substance

% of Biodegradation

Test substance

% of Biodegradation

Reference + Test substance

0

0

0

0

1

3

3

7

7

90

35

-

14

101

58

-

21

102

88

-

28

127

118

90

 

Conclusions

On the basis of results obtained, interpreted in accordance to OECD 310:2014, the test substance was considered readily biodegradable in aerobic condition.

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
Under the study conditions, the test substance was determined to be readily biodegradable.

Executive summary:

A study was conducted to determine the ready biodegradability of the read across substance, 'mono- and di- C16 PSE, K+ and C16-OH and isostearyl isostearate', using Headspace test method (CO2 in sealed vessels), according to OECD Guideline 310, in compliance with GLP. Aerobic sludge inoculum was prepared with mixed treatment plant of urban (66%) and industrial (34%) liquid sewage and in order to have a concentration of suspended solid of about 4 mg/L. In the study, 17 replicates of blanks (containing only culture medium), positive control (sodium benzoate at 18.61 mg/L) and read across substance (39.73 mg/L) and 8 replicates of toxicity control (i.e., read across substance and reference substances) were used. All treated samples were kept at the temperature of 20°C for 28 d. The calculation of biodegradation as total inorganic carbon (TIC) were determined at each sampling time (i.e., 0, 1, 7, 14, 21 and 28 d) for the reference substance, test sample and blank. For toxicity control, calculation of biodegradability as total inorganic carbon (TIC) was determined on Day 1 and 28. The trend of the inorganic carbon and related biodegradation percentages in the bottle containing both the test sample and the reference substance, confirmed the absence of inhibitory effect of the test sample on inoculum. At 28 d, the biodegradability of the test substance was determined to be 118%. At 14 d biodegradability for reference substance was determined to be 101%. The mean amount of TIC present in the blank controls at the end of the test was < 3 mg C/L. Therefore, the test was considered to have satisfied all the validity criteria. Therefore, under the study conditions, the read across substance was considered to be readily biodegradable (Eurofins, 2017). Based on the results of the read across study, a similar biodegradation potential can be considered for the test substance, 'mono- and di- C16 PSE, K+ and C16 -18-OH'.

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
weight of evidence
Study period:
1991
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
comparable to guideline study with acceptable restrictions
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
Deviations:
not specified
GLP compliance:
not specified
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
Inoculum concentration: 3 - 5 g/L suspended solids, diluted 200 mL to 3 L in mineral medium.
Test volume: 3000 mL
Temperature: not reported
pH: not reported
Duration of test (contact time):
>= 46 d
Initial conc.:
ca. 20 mg/L
Based on:
test mat.
Details on study design:
Duplicate assays were performed, although the samples were prepared differently. The first sample was prepared by direct addition of a single piece of solid material to the test vessel, while the second was added using a heated dropper to produce round solid droplets. Results were not within +/- 20% for the two samples.
Test performance:
The following validity criteria were met:
(1) The blanks were valid for this test, the maximum milligrams of carbon dioxide were well within the 40 mg/L range (13.5-18.8 mg/L),
(2) The reference substance reached the pass level within 14 d.
Key result
Parameter:
% degradation (CO2 evolution)
Value:
ca. 55 - ca. 91
Sampling time:
46 d
Key result
Parameter:
% degradation (CO2 evolution)
Value:
ca. 21 - ca. 65
Sampling time:
28 d
Parameter:
% degradation (CO2 evolution)
Value:
ca. 7 - ca. 21
Sampling time:
19 d
Parameter:
% degradation (CO2 evolution)
Value:
ca. 3 - ca. 10
Sampling time:
12 d
Results with reference substance:
A) Kinetic of control substance: 8 d = 57.0%, 14 d = 72.3%, 22 d = 82.3%. 28 d = 83.0%
B) The test substance did not meet the '10-d window' rule for ready biodegradation. The test substance required 5 extra days for a total of 15 d to reach 60% of maximum theoretical carbon dioxide production.
C) The reference substance Sodium acetate degraded by 84% after 28 d.
Validity criteria fulfilled:
not specified
Interpretation of results:
readily biodegradable, but failing 10-day window
Conclusions:
Under the study conditions, the test substance was determined to be readily biodegradable, but failing 10-d window.
Executive summary:

A study was conducted to determine the ready biodegradability of the test substance, Alcohols C16-18 (purity not specified), using CO2 evolution test, according method similar to OECD Guideline 301B. An activated sludge, domestic, non adapted (3-5 g/L suspended solids, 3 L volume) inoculum was treated with test substances (20 mg/L) and reference substance (Sodium benzoate) at 25°C for 46 d. Degradation was followed over 28 d by determining the carbon dioxide produced. Duplicate assays were performed, although the samples were prepared differently. The first sample was prepared by direct addition of a single piece of solid material to the test, while the second was added using a heated dropper to produce round solid droplets. Results were not within +/- 20% for the two samples. The test substance attained 21 - 65% and 55 - 91% degradations in 28 and 46 d, respectively. The test substance did not meet the 10-d window rule for ready biodegradation. The test substance required 5 extra days for a total of 15 d to reach 60% of maximum theoretical carbon dioxide production. The reference substance sodium acetate degraded by 84% after 28 d. The study has met all validity criteria. Under the study conditions, the test substance was determined to be readily biodegradable, but failing 10-d window (OECD SIDS, 2006).

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Study period:
1997
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Justification for type of information:
Refer to section 13 of IUCLID for details on the read-across justification. The study with the read across substance is considered sufficient to fulfil the information requirements as further explained in the provided endpoint summary.
Reason / purpose:
read-across source
Qualifier:
according to
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
Deviations:
not specified
GLP compliance:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic (adaptation not specified)
Details on inoculum:
Concentration of activated sludge: 30 mg dry matter/L
Test volume: 3 L
Temperature: 21°C
pH: not reported
Duration of test (contact time):
ca. 29 d
Initial conc.:
ca. 17.1 mg/L
Based on:
other: Related to test substance
Parameter followed for biodegradation estimation:
CO2 evolution
Reference substance:
benzoic acid, sodium salt
Key result
Parameter:
% degradation (CO2 evolution)
Value:
ca. 62
Sampling time:
28 d
Remarks on result:
other: readily biodegradable, but failing 10-day window
Parameter:
% degradation (CO2 evolution)
Value:
ca. 52
Sampling time:
16 d
Parameter:
% degradation (CO2 evolution)
Value:
ca. 10
Sampling time:
6 d
Details on results:
The following validity criteria were fulfilled:
(1) degradation rate of the reference substance had reached a level of 60% within 14 d,
(2) parallel assays did not differ by more than 20%,
(3) CO2 evolution in the inoculum blank did not exceed 40 mg/L at the end of the test,
(4) IC content of the test substance suspension in mineral medium at the start of the test was less than 5% of the total carbon.

Results: Kinetic of test substance (% degradation)
6 d = 10%
16 d = 52%
28 d = 62%
The test substance attained 62% degradation over the test period. However, the 60% pass level was not reached within the 10 d window, therefore it cannot be considered readily biodegradable.
Results with reference substance:
Result: Kinetic of control substance (% degradation)
6 d = 40%
16 d = 102%
28 d = 105%
Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable, but failing 10-day window
Conclusions:
Under the study conditions, the test substance was determined to be readily biodegradable, but failing 10-day window.
Executive summary:

A study was conducted to determine the ready biodegradability of the read across substance, hexadecan-1-ol (purity not specified), using CO2 evolution test, according to OECD Guideline 301B, in compliance with GLP. An activated sludge, domestic (30 mg dry matter/L, 3 L volume) inoculum was treated with test substances (17.1 mg/L) and reference substance (Sodium benzoate) at 25°C for 28 d. Degradation was followed over 28 d by determining the carbon dioxide produced. The test substance attained 62% degradation over the test period. However, the 60% pass level was not reached within the 10 d window. The study has met all validity criteria. Under the study conditions, the read across substance was determined to be readily biodegradable, but failing 10-d window (OECD SIDS, 2006). Based on the results of the read across study, a similar biodegradation potential can be considered for the test substance, 'mono- and di- C16 PSE, K+ and C16 -18-OH'.

Description of key information

Based on the available weight of evidence information from the read across studies of the main constituents, the test substance, mono- and di- C16 PSE, K+ + C16-18-OH, is considered to be inherently biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

In absence of biodegradation study with the test substance, the endpoint has been assessed based on studies for substances representative of the main constituents, which can be categorised as phosphate esters (PSE; i.e., mono- and di- C16 PSE, K+) and alcohol (i.e., alcohols, C16-18). The results are presented below:

Constituent: PSE – read across studies

Study 1:A study was conducted to determine the ready biodegradability of the read across substance, 'mono- and di- C16 PSE, K+ and H3PO4' (purity: 100%), using Manometric respirometry method, according to OECD Guideline 301F, in compliance with GLP. Following the pre-conditioning, the test bottles containing prepared activated sludge inoculum in mineral medium were set up for the test according to the experimental design. In the study, Inoculum blanks, positive control (sodium benzoate at 100 mg/L), test substance (100 mg/L) as well as toxicity controls (test and reference substances, both at 100 mg/L), each these group bottles were prepared in triplicate, except inoculum blanks which were prepared in duplicate. Additional single replicate test substance and toxicity control bottles were prepared for determination of pH at Day 0, so undissolved test substance was not removed by the pH probe. Oxygen uptake was recorded automatically every 240 minutes during the 60 d experimental period. Oxygen uptake values were corrected for the inoculum blank and the biodegradation was calculated as a percentage of the chemical oxygen demand (COD) for the substance under test and as a percentage of the theoretical oxygen demand (ThOD) for the reference substance. The chemical oxygen demand (COD) of test substance was determined using spectrophotometer for evaluation. The test substance attained a mean level of biodegradation (based on the BOD:COD ratio) of 40% after 28 d and 64% after 60 d. The test substance results showed good replication. Less than 60% degradation was achieved within 28 d, so test substance was classified as inherently biodegradable. Sodium benzoate attained a mean level of biodegradation (based on the BOD:ThOD ratio) of 86%, and the results showed good replication. More than 60% degradation was achieved within the 10-d window as expected for a biodegradable substance, thus confirming that the activated sludge contained viable organisms. The mean toxicity control degradation achieved on Day 14 was 40% (based on combined ThOD/COD), as this was > 25% the test substance was assumed not to be inhibitory at this concentration. The test met all the all validity criteria. Under the study conditions, the read across substance was considered to be inherently biodegradable (Scymaris, 2017).

 

Study 2:A study was conducted to determine the ready biodegradability of the read across substance, 'mono- and di- C16 PSE, K+ and C16-OH and isostearyl isostearate', using Headspace test method (CO2 in sealed vessels), according to OECD Guideline 310, in compliance with GLP. Aerobic sludge inoculum was prepared with mixed treatment plant of urban (66%) and industrial (34%) liquid sewage and in order to have a concentration of suspended solid of about 4 mg/L. In the study, 17 replicates of blanks (containing only culture medium), positive control (sodium benzoate at 18.61 mg/L) and read across substance (39.73 mg/L) and 8 replicates of toxicity control (i.e., read across substance and reference substances) were used. All treated samples were kept at the temperature of 20°C for 28 d. The calculation of biodegradation as total inorganic carbon (TIC) were determined at each sampling time (i.e., 0, 1, 7, 14, 21 and 28 d) for the reference substance, test sample and blank. For toxicity control, calculation of biodegradability as total inorganic carbon (TIC) was determined on Day 1 and 28. The trend of the inorganic carbon and related biodegradation percentages in the bottle containing both the test sample and the reference substance, confirmed the absence of inhibitory effect of the test sample on inoculum. At 28 d, the biodegradability of the test substance was determined to be 118%. At 14 d biodegradability for reference substance was determined to be 101%. The mean amount of TIC present in the blank controls at the end of the test was < 3 mg C/L. Therefore, the test was considered to have satisfied all the validity criteria. Therefore, under the study conditions, the read across substance was considered to be readily biodegradable (Eurofins, 2017).

 

Constituent: Alcohol

Study 1:A study was conducted to determine the ready biodegradability of the test substance, Alcohols C16-18 (purity not specified), using CO2 evolution test, according method similar to OECD Guideline 301B. An activated sludge, domestic, non-adapted (3-5 g/L suspended solids, 3 L volume) inoculum was treated with test substances (20 mg/L) and reference substance (Sodium benzoate) at 25°C for 46 d. Degradation was followed over 28 d by determining the carbon dioxide produced. Duplicate assays were performed, although the samples were prepared differently. The first sample was prepared by direct addition of a single piece of solid material to the test, while the second was added using a heated dropper to produce round solid droplets. Results were not within +/- 20% for the two samples. The test substance attained 21 - 65% and 55 - 91% degradations in 28 and 46 d, respectively. The test substance did not meet the 10-d window rule for ready biodegradation. The test substance required 5 extra days for a total of 15 d to reach 60% of maximum theoretical carbon dioxide production. The reference substance sodium acetate degraded by 84% after 28 d. The study has met all validity criteria. Under the study conditions, the test substance was determined to be readily biodegradable, but failing 10-d window (OECD SIDS, 2006).

 

Study 2: A study was conducted to determine the ready biodegradability of the read across substance, hexadecan-1-ol (purity not specified), using CO2 evolution test, according to OECD Guideline 301B, in compliance with GLP. An activated sludge, domestic (30 mg dry matter/L, 3 L volume) inoculum was treated with test substances (17.1 mg/L) and reference substance (Sodium benzoate) at 25°C for 28 d. Degradation was followed over 28 d by determining the carbon dioxide produced. The test substance attained 62% degradation over the test period. However, the 60% pass level was not reached within the 10 d window. The study has met all validity criteria. Under the study conditions, the read across substance was determined to be readily biodegradable, but failing 10-d window (OECD SIDS, 2006).

 

 

Overall, based on the available weight of evidence from studies for substances representing the main constituents and the fact that the constituent alcohol, make up more than 80% of the composition, the test substance, 'mono- and di- C16 PSE, K+ and C16-18-OH', can be considered to be readily biodegradable.

[Type of water: freshwater]