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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:
10-May-2017 to 07-June-2017
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)
Deviations:
no
GLP compliance:
yes
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL
- Appearance: Orange, brown liquid
- Source and lot/batch No.of test material: 624730
- Expiration date of the lot/batch: Dec 2017
- Certificate of Analysis date: 14 Feb 2017
- Purity: 97.1%

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: Away from strong bases, otherwise no special requirements
- Stability under test conditions: Substance is hydrolytically active

ThOD of test material was calculated to be 2.43 mg O2/mg test item
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge: Joint Abbotsford Mission Environmental Systems wastewater treatment plant, Abbotsford, BC.
- Laboratory culture: Sludge was washed twice by centrifugation 10 min at 2500 RPM, 4 °C and resuspension in mineral medium.
- Storage conditions: The washed, resuspended sludge (approx. 3.5 L) was placed in a foil-wrapped 4-L flask, aerated, and stirred at test temperature for five days.
- Preparation of inoculum for exposure: pH adjustment not required (pH 6.2)
- Concentration of sludge: ca. 20 mg/L (solids)
Duration of test (contact time):
28 d
Initial conc.:
40 mg/L
Based on:
test mat.
Initial conc.:
97.33 mg/L
Based on:
ThOD
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: Mineral medium per OECD 301F
- Additional substrate: none
- Solubilising agent: None. Test substance was weighed onto bent glass slides which were added directly to test vessels.
- Test temperature: 20 - 21 °C
- pH: 7.2 - 7.6
- pH adjusted: no
- Suspended solids concentration: 20 mg/L
- Continuous darkness: yes
TEST SYSTEM
- Culturing apparatus: 2-L flat-bottomed bottles sealed with a rubber bottle stopper connected to a manometric respirometer and a controlled inlet source of ultra-high purity grade oxygen. Each bottle contained a CO2 trap suspended from the top of the bottle stopper. Total fill volume was 1.5 liters.
- Number of culture flasks/concentration: two
- Method used to create aerobic conditions: stirring and controlled introduction of oxygen gas
- Measuring equipment: online manometer
- Test performed in open system: no
- Details of trap for CO2 and volatile organics if used: small scintillation vial with ~4.0 g of potassium hydroxide pellets
CONTROL AND BLANK SYSTEM
- Inoculum blank: duplicate
- Abiotic sterile control: single flask as per test substance, with addition of mercuric chloride (50 mg/L final) as biocide
- Toxicity control: single flask with both test substance (ca. 40 mg/L) and reference substance (60 mg/L)
Reference substance:
benzoic acid, sodium salt
Remarks:
60 mg/L
Key result
Parameter:
% degradation (O2 consumption)
Value:
>= 60 - <= 61
Sampling time:
28 d
Remarks on result:
other:
Remarks:
the 10-day window criteria was not met (see details on results)
Details on results:
The 10-day window for the test replicates commenced on Day 4. The Test replicates did not surpass 60% biodegradation by the end of the 10-day window.

Detailed results on oxygen utilization of inoculum blanks are provided in Table 1. Oxygen utilization is within range of guideline validity criteria.
Detailed results on oxygen utilization of test substance are provided in Table 2 and are graphically depicted in the illustration.
Detailed results on oxygen utilization by the reference substance and in the toxicity control are provided in Table 3. The toxicity control showed 52% degradation by day 14, indicating no toxicity by the test substance.
Detailed results on oxygen utilization in the abiotic control are provided in Table 4. The abiotic control showed negative oxygen utilization throughout the experiment. While the reason for this is unclear, the results show that the test substance does not exert an abiotic demand for oxygen.
Results with reference substance:
56% degradation by day 3, 60% biodegradation by day 5 (see Table 3).

Table 1. Oxygen use in inoculum blanks

Day Blank 1 oxygen use (mg) Blank 2 oxygen use (mg) Mean Blank oxygen use (mg)
0 0 -0.1 0
1 -13.3 -9.0 -11.2
2 -6.5 -4.2 -5.3
3 -4.4 -2.6 -3.5
4 -0.9 1.2 0.1
5 2.0 2.3 2.1
6 -7.0 -5.8 -6.4
7 10.3 11.8 11.1
8 12.3 13.2 12.8
9 12.3 13.2 12.8
10 14.5 15.7 15.1
11 17.7 18.6 18.1
12 16.9 16.8 16.8
13 12.0 11.5 11.8
14 11.9 11.4 11.7
15 11.8 10.0 10.9
16 13.3 11.9 12.6
17 16.1 16.5 16.3
18 17.4 16.1 16.7
19 15.6 14.3 15.0
20 13.5 12.2 12.9
21 14.1 12.2 13.2
22 13.6 11.5 12.6
23 19.6 17.8 18.7
24 16.7 14.9 15.8
25 20.8 17.9 19.3
26 25.3 23.7 24.5
27 20.2 16.3 18.2
28 14.9 12.0 13.5

Table 2. Raw and blank-corrected oxygen use, BOD and percent biodegradation in test samples

Day Raw Test 1 oxygen use (mg) Raw Test 2 oxygen use (mg) Corrected Test 1 oxygen use (mg) Corrected Test 2 oxygen use (mg) BOD Test 1 (mg O2/L) BOD Test 2 (mg O2/L) % Biodeg Test 1 % Biodeg Test 2 % Biodeg Mean
0 -0.1 0.3 0.0 0.3 -0.033 0.232 0 0 0
1 -14.3 -1.1 -3.1 10.1 -2.087 6.726 -2 7 2
2 0.5 11.2 5.8 16.6 3.877 11.034 4 11 8
3 5.1 14.3 8.5 17.8 5.699 11.862 6 12 9
4 21.1 26.9 20.9 26.8 13.95 17.859 14 18 16
5 31.3 37.0 29.2 34.8 19.450 23.227 20 24 22
6 32.1 35.9 38.5 42.2 25.646 28.164 26 29 28
7 54.9 58.5 43.8 47.5 29.191 31.643 30 33 31
8 62.5 64.0 49.8 51.2 33.167 34.161 34 35 35
9 65.5 69.0 52.7 56.2 35.155 37.475 36 39 37
10 72.7 74.7 57.6 59.5 38.369 39.695 39 41 40
11 77.8 79.8 59.7 61.7 39.794 41.120 41 42 42
12 81.4 81.3 64.6 64.5 43.041 42.975 44 44 44
13 78.7 78.8 66.9 67.0 44.632 44.698 46 46 46
14 80.0 81.4 68.3 69.7 45.560 46.487 47 48 47
15 82.4 82.6 71.5 71.7 47.647 47.780 49 49 49
16 86.2 86.8 73.6 74.2 49.039 49.436 50 51 51
17 90.5 91.0 74.2 74.7 49.436 49.768 51 51 51
18 93.1 95.3 76.4 78.6 50.927 52.385 52 54 53
19 93.0 95.1 78.1 80.2 52.054 53.446 53 55 54
20 92.3 94.4 79.5 81.6 52.982 54.373 54 56 55
21 94.5 95.4 81.4 82.3 54.241 54.837 56 56 56
22 93.1 95.3 80.6 82.8 53.711 55.169 55 57 56
23 101.2 103.8 82.5 85.1 55.003 56.726 57 58 57
24 99.6 102.1 83.8 86.3 55.864 57.521 57 59 58
25 103.5 105.2 84.1 85.8 56.096 57.223 58 59 58
26 110.8 109.8 86.3 85.3 57.554 56.892 59 58 59
27 105.7 103.9 87.4 85.6 58.283 57.090 60 59 59
28 102.1 100.5 88.6 87.0 59.078 58.018 61 60 60

Table 3. Raw and blank-corrected oxygen use, BOD and percent biodegradation in a reference and toxicity controls

Day Raw Reference oxygen use (mg) Corrected Reference oxygen use (mg) BOD Reference (mg O2/L) % Biodeg Reference Raw Tox Control oxygen use (mg) Corrected Tox Control oxygen use (mg) BOD Tox Control (mg O2/L) % Biodeg Tox Control
0 0 0 0.033 0 -0.1 0 -0.033 0
1 -7.0 4.2 2.816 3 -8.4 2.7 1.822 1
2 62.4 67.7 45.162 45 65.2 70.5 47.018 24
3 80.9 84.4 56.262 56 84.1 87.6 58.383 30
4 89.6 89.4 59.609 60 91.3 91.1 60.735 31
5 91.8 89.7 59.807 60 97.2 95.1 63.386 32
6 83.7 90.1 60.039 60 99.4 105.8 70.510 36
7 102.2 91.1 60.735 61 125.1 114.1 76.043 39
8 109.5 96.8 64.512 65 138.0 125.2 83.465 42
9 111.1 98.4 65.573 66 143.5 130.8 87.176 44
10 115.3 100.2 66.799 67 151.7 136.6 91.053 46
11 118.8 100.6 67.097 67 158.1 139.9 93.273 47
12 119.2 102.3 68.223 68 165.3 148.5 98.972 50
13 114.8 103.0 68.687 69 160.9 149.2 99.436 50
14 114.8 103.1 68.754 69 166.9 155.2 103.478 52
15 114.5 103.6 69.052 69 170.1 159.1 106.096 54
16 117.4 104.8 69.847 70 174.8 162.2 108.150 55
17 119.8 103.5 68.986 69 180.4 164.1 109.409 55
18 121.9 105.1 70.079 70 183.9 167.1 111.431 56
19 120.3 105.3 70.212 70 184.0 169.0 112.690 57
20 118.9 106.0 70.675 71 187.4 174.5 116.334 59
21 120.0 106.8 71.206 71 192.2 179.1 119.383 61
22 118.3 105.7 70.477 71 191.1 178.5 118.985 60
23 126.1 107.5 71.636 72 200.2 181.5 121.006 61
24 125.2 109.4 72.962 73 198.5 182.7 121.802 62
25 128.0 108.7 72.465 73 206.4 187.0 124.684 63
26 133.9 109.4 72.929 73 213.3 188.8 125.877 64
27 128.0 109.8 73.194 73 208.3 190.1 126.739 64
28 123.6 110.1 73.392 73 203.9 190.4 126.937 64

Table 4. Raw and blank-corrected oxygen use, BOD and percent biodegradation in abiotic controls

Day Raw Abiotic control oxygen use (mg) Corrected Abiotic control oxygen use (mg) BOD Abiotic control (mg O2/L) % Biodeg Abiotic control
0 0 0 0.033 0
1 -15.2 -4.0 -2.684 -3
2 -10.8 -5.5 -3.678 -4
3 -11.2 -7.8 -5.169 -5
4 -8.6 -8.8 -5.865 -6
5 -9.4 -11.6 -7.720 -8
6 -19.9 -13.5 -9.013 -9
7 -3.9 -15.0 -9.973 -10
8 -4.2 -16.9 -11.299 -12
9 -4.5 -17.2 -11.498 -12
10 -3.8 -18.9 -12.591 -13
11 0.0 -18.1 -12.094 -12
12 -2.2 -19.0 -12.690 -13
13 -8.0 -19.7 -13.154 -14
14 -8.8 -20.5 -13.684 -14
15 -10.1 -21.1 -14.049 -14
16 -8.4 -21.1 -14.049 -14
17 -3.0 -19.3 -12.856 -13
18 -3.3 -20.0 -13.353 -14
19 -5.5 -20.4 -13.618 -14
20 -8.3 -21.1 -14.082 -14
21 -8.8 -22.0 -14.678 -15
22 -8.9 -21.5 -14.347 -15
23 -3.7 -22.4 -14.910 -15
24 -6.2 -22.0 -14.645 -15
25 -3.0 -22.3 -14.877 -15
26 2.3 -22.2 -14.811 -15
27 -4.0 -22.2 -14.811 -15
28 -9.9 -23.4 -15.606 -16
Validity criteria fulfilled:
yes
Remarks:
difference in test substance degradation <20% (1%), ref substance degradation >60% by day 14 (day 7), toxicity control degradation >25% by day 14 (52%), oxygen uptake by inoculum blanks <60 mg/L in 28 days (mean, 13.5 mg/1.5 L), pH within range 6-8.5.
Interpretation of results:
not readily biodegradable
Remarks:
60% BOD/ThOD after 28 days, but failing 10-day window criteria
Conclusions:
In duplicate flasks, MTDID 47403 was degraded 61% and 60% (mean, 60% BOD/ThOD) in an OECD 301F test. MTDID 47403 was not inhibitory to biodegradation.
Executive summary:

Degradability of MTDID 47403 was assessed according to OECD 301F. Duplicate flasks were used for blanks and the test substance, with single flasks for reference substance (sodium benzoate), toxicity control, and abiotic (mercuric chloride-killed) samples. The reference substance was degraded adequately by day 7. The test substance was biodegraded 60% and 61% (average, 60% BOD/ThOD) by day 28, however during the 10-day window, only 47% degradation occurred. The toxicity control was biodegraded 52% by day 14. The test substance is not readily biodegradable, due to failing the 10-day window criteria, but is not inhibitory to biodegradation.

The test was conducted according to internationally accepted guidelines under GLP criteria. It is reliable without restrictions and 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
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
Specific details on test material used for the study:
Ethyl dodecyl sulfide, CAS# N/A, a hydrolysis product of MTDID 47403; 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 tridecyl 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 47403. 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 47403 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:
15-June-2018 to 18-June-2018
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
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
Specific details on test material used for the study:
Dipentyl glutaconate, CAS# None, a hydrolysis product of MTDID47403; SMILES: CCCCCOC(=O)C/C=C/C(=O)OCCCCC
Duration of test (contact time):
28 d
Parameter:
% degradation (O2 consumption)
Value:
93
Sampling time:
28 d
Remarks on result:
readily biodegradable based on QSAR/QSPR prediction
Remarks:
Catalogic 301C v.08.12 Model (95% C.I. ± 7%)
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 (passes 10-day window criteria for ready-biodegradability)
Parameter:
% degradation (CO2 evolution)
Value:
69
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:
81.3
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 dipentyl glutaconate 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 89.47% within correctly predicted training chemicals and 10.53% not present in the training chemicals for the model, and therefore the chemical is out of the interpolation structural space. There is a closely related chemical within the model's training set. Dibutyl adipate (CAS# 105-99-7) has an observed degradation of 90% BOD, and the Catalogic model predicted a value of 92% BOD (95% C.I. ± 4%).

Catalogic OECD 301F model:
The QPRF for dipentyl glutaconate 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 89.47% within correctly predicted training chemicals, 5.26 in non-correctly predicted training chemicals for the model, and 5.26% 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 dipentyl glutaconate 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 89.47% within correctly predicted training chemicals and 10.53% 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:
Dipentyl glutaconate has an estimated 28-day biodegradation level of 81.3% BOD as an average of the predicted values from three ready biodegradability models within OASIS Catalogic v.5.11.17 software models.
Executive summary:

Dipentyl glutaconate is identified as one of the hydrolysis products of MTDID 47403. The 28-day biodegradation level of dipentyl glutaconate was estimated to be 81.3% BOD as an average of the predicted values from three ready biodegradability models within OASIS Catalogic v.5.11.17 software. Individual 28-day model results were 93% BOD (95% C.I. ± 7%, OECD 301C model), 82% BOD (OECD 301F model), 69% 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 an analogous chemical which supports the predicted value. The observed and predicted

degradation values with the analogous chemical add confidence to the estimated value for dipentyl glutaconate, which is pertinent to the fate of MTDID 47403 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:
7-June-2018
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
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
Specific details on test material used for the study:
Dimethyl gluconate, CAS# 5164-76-1, a hydrolysis product of MTDID47403; SMILES: O=C(C/C=C/C(=O)OC)OC
Duration of test (contact time):
28 d
Key result
Parameter:
% degradation (O2 consumption)
Value:
94
Sampling time:
28 d
Remarks on result:
readily biodegradable based on QSAR/QSPR prediction
Remarks:
Catalogic 301C v.08.12 Model (note, 95% C.I. ± 8%)
Parameter:
% degradation (O2 consumption)
Value:
70
Sampling time:
28 d
Remarks on result:
other:
Remarks:
The predicted 70% BOD in 28 days, by the Catalogic 301F v.13.16 model, indicates that the chemical is not persistent, however the model also predicted that the degradation would not meet the 10-day window criteria to be considered readily biodegradable.
Parameter:
% degradation (CO2 evolution)
Value:
75
Sampling time:
28 d
Remarks on result:
readily biodegradable based on QSAR/QSPR prediction
Remarks:
Catalogic 301B v.02.09 Model result
Details on results:
Catalogic OECD 301C model:
The QPRF for dimethyl glutaconate 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 81.82% within correctly predicted training chemicals and 18.18% not present in the training chemicals for the model, and therefore the chemical is out of the interpolation structural space. There are four related chemicals within the model's training set. These include methyl acetate (CAS# 79-20-9) with an observed degradation of 92% BOD, and model predicted value of 89% BOD (95% C.I. ± 6%); dimethyl glutarate (CAS# 1119-40-0) with an observed degradation of 90% BOD, and model predicted value of 94% BOD (95% C.I. ± 4%); butanoic acid, 3-oxo-, methyl ester (CAS# 105-45-3) with an observed degradation of 78% BOD, and model predicted value of 93% BOD (95% C.I. ± 3%); and butanedioic acid, 1,4-dimethyl ester (CAS# 106-65-0) with an observed degradation of 90% BOD, and model predicted value of 87% BOD (95% C.I. ± 5%).

Catalogic OECD 301F model:
The QPRF for dimethyl glutaconate reports that the chemical fulfills the general properties requirements of the model, and its structural fragments are indicated to be 81.82% within correctly predicted training chemicals, 9.09% in non-correctly predicted training chemicals, and 9.09% 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 dimethyl glutaconate 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 90.91% within correctly predicted training chemicals and 9.09% 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:
Dimethyl glutaconate has an estimated 28-day biodegradation level of 94% BOD from the OECD 301C model within OASIS Catalogic v.5.11.17 software.
Executive summary:

Dimethyl glutaconate is identified as one of the hydrolysis products of MTDID 47403. The 28-day biodegradation level of dimethyl glutaconate was estimated to be 94% BOD by the OECD 301C model within OASIS Catalogic v.5.11.17 software. The 28-day results from other models were 70% BOD (OECD 301F model), 75% 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 biodegradation values for four analogous chemicals, which are in good agreement with their model-estimated values. The four analogous chemicals are readily biodegradable. These observed degradation values add confidence to the estimated value for dimethyl glutaconate, which is pertinent to the fate of MTDID 47403, 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
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))
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 thioethers and may be used in a weight of evidence argument on the fate of MTDID 47403.

Description of key information

Mean MTDID 47403 biodegradation was 60% BOD/ThOD in an OECD 301F test, but it does not pass the 10-day window. MTDID 47403 was not inhibitory to biodegradation.

Key value for chemical safety assessment

Additional information

In an OECD 301F test, MTDID 47403 was biodegraded 60% and 61% (average, 60% BOD/ThOD) by day 28. However, during the 10-day window, only 47% degradation occurred. The toxicity control was biodegraded 52% by day 14. MTDID 47403 does not pass the 10-day window criteria, but is not inhibitory to biodegradation.

MTDID 47403 is hydrolytically active, producing a mixture of glutaconate esters, dodecyl ethyl sulfide, and tetrafluoroborate anion. 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. For the glutaconate esters, the 301C model includes experimentally determined biodegradation values for analogous chemicals, which are in good agreement with their model-estimated values. Dimethyl glutaconate had an estimated biodegradation of 94% BOD, while dipentyl glutaconate had an estimated 28-day biodegradation level of 93% BOD in the 301C. Methyl pentyl glutaconate biodegradation is expected to be at an intermediate level. 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 (observed 28-day degradation, 57% BOD; estimated degradation, 2% BOD). The predicted metabolic pathway for thioethers involves formation of mercaptans. Any mercaptans formed would be potentially toxic to the organism forming them.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.The ability to degrade MTDID 47403 hydrolysis products depends on the specific population of organisms, with the ability to use sulfides being available in most environments. Therefore, MTDID 47403 is expected to form persistent, but not very persistent, degradation products upon rapid hydrolysis andand its hydrolysis products are expected not to be persistent in the environment.