Diisopropylbiphenyl and triisopropylbiphenyl

Biodegradation in water and sediment: simulation tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: sediment simulation testing

Type of information:

(Q)SAR

Remarks:

Triisopropyl biphenyl isomer mixture (TIPB; CAS-No.: 29225-91-0) represents one main constituent of the registered UVCB (Alkylation and transalkylation products of biphenyl with propene)

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

results derived from a valid (Q)SAR model and falling into its applicability domain, with adequate and reliable documentation / justification

Justification for type of information:

1. SOFTWARE
Vega version 1.1.4

2. MODEL (incl. version number)
Persistence in sediment Model version 1.0.0

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
See “Test material information”

4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
See attached information on the model provided by the developer. Further information on the OECD criteria as outlined by the applicant is provided below under "Any other information of materials and methods incl. tables"

5. APPLICABILITY DOMAIN
See attached information and information as provided in "Any other information on results incl. tables".

6. ADEQUACY OF THE RESULT
See assessment of adequacy as outlined in the "Overall remarks, attachments" section.

Qualifier:

according to guideline

Guideline:

other: REACH Guidance on QSARs R.6

Principles of method if other than guideline:

- Software tool(s) used including version: Vega v1.1.4
- Model(s) used: Persistence in sediment Model version 1.0.0

Full reference and details of the used formulas can be found in:
A. Manganaro, F. Pizzo, A. Lombardo, A. Pogliaghi, E. Benfenati, “Predicting persistence in the sediment compartment with a new automatic software based on the k-Nearest Neighbor (k-NN) algorithm”, Chemosphere (2015), accepted paper.
Gouin, T., Cousins, I., Mackay, D., “Comparison of two methods for obtaining degradation halflives”, Chemosphere 56, 2004, 531-535
Gramatica, P., Papa, E., “Screening and ranking of POPs for Global Half-Life: QSAR approaches for prioritization based on molecular structure”, Environ. Sci. Technol. 41, 2007, 2833-9.

- Model description: see field 'Justification for non-standard information', 'Attached justification' and 'any other information on Material and methods'
- Justification of QSAR prediction: see field 'Justification for type of information', 'Attached justification' and/or 'overall remarks'

GLP compliance:

no

Radiolabelling:

no

Oxygen conditions:

aerobic

Remarks on result:

other: TIPB was predicted to be vP

Transformation products:

not specified

For detailed information on the results please refer to the attached report.

Validity criteria fulfilled:

not applicable

Reference 2

Endpoint:

biodegradation in water: simulation testing on ultimate degradation in surface water

Remarks:

Feasibility study under OECD 309 test conditions with three different test designs and determination of the degradation of five selected main constituents of the registered UVCB (Alkylation and transalkylation products of biphenyl with propene).

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 309 (Aerobic Mineralisation in Surface Water - Simulation Biodegradation Test)

Version / remarks:

2004

Principles of method if other than guideline:

The following three study designs were used to evaluate the feasibility and limitations of testing the biodegradability:
I. Open system
II. Closed system with tubes (Tenax® or activated carbon)
III: Closed system with solvent (toluene) traps

GLP compliance:

yes (incl. QA statement)

Radiolabelling:

no

Oxygen conditions:

aerobic

Inoculum or test system:

natural water: freshwater

Details on source and properties of surface water:

Details on collection:
- Location: Aalkistensee, a natural aerobic surface water source (75433 Maulbronn, Germany, 48°59’37.439’’N, 8°45’25.714’’E)
- Sampling procedure: Water was sampled from the top 5 to 10 cm of the natural resource and transported in polyethylene containers to the laboratory.
- Date of sampling:
07 November 2019 (Batch 20191107, used in open system and closed system with Tenax tubes)
12 December 2019 (Batch 20191218, used in closed systems with activated carbon tubes and solvent traps).

Storage conditions:
- Stored at 4 °C. prior to use, coarse particles were removed by filtration through a filter with 100 µm mesh size.

Characteristics of the water at time of collection:
- Temperature [°C]:
Batch 20191107 = 10.5°C
Batch 20191218 = 6.5°C
- pH at time of collection:
Batch 20191107 = 8.05
Batch 20191218 = 8.12
- Redox potential [mv]:
Batch 20191107 = 250
Batch 20191218 = 180
- Oxygen concentration [mg/l]:
Batch 20191107 = 10.04 (below water surface) / 8.53 (water/sediment interface)
Batch 20191218 = 12.04 (below water surface) / 11.70 (water/sediment interface)

Characteristics of the water at study start:
- pH at time of collection:
Batch 20191107 = 8.15
Batch 20191218 = 7.96
- Total Organic Carbon (TOC) [mg/L]:
Batch 20191107 = 42
Batch 20191218 = 33
- Dissolved Organic Carbon (DOC) [mg/L]:
Batch 20191107 = 39
Batch 20191218 = 23
- Total nitrogen [mg/L]:
Batch 20191107 = 18
Batch 20191218 = 14
- Total phosphorus [mg/L]:
Batch 20191107 = 0.03
Batch 20191218 = 0.04
- Total ammonium [mg/L]:
Batch 20191107 = 1.3
Batch 20191218 = 4.8
- Total nitrite [mg/L]:
Batch 20191107 = 0.03
Batch 20191218 = 0.11
- Total nitrate [mg/L]:
Batch 20191107 = 1.0
Batch 20191218 = 2.8
- Dissolved Orthophosphate [mg/L]:
Batch 20191107 <0.01
Batch 20191218 <0.01
- Biological Oxygen Demand (BOD) [mg/L O2]:
Batch 20191107 = 9.4
Batch 20191218 = 8.8

Duration of test (contact time):

>= 7 - <= 78 d

Initial conc.:

3 µg/L

Based on:

test mat.

Initial conc.:

15 µg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

radiochem. meas.

test mat. analysis

Details on study design:

The following three study designs were used to evaluate the feasibility and limitations of testing the biodegradability of the UVCB test item:

I. OPEN SYSTEM
- Test vessels: 1000 mL all-glass flasks with Polyurethane (PU-) foam stopper in the upper neck to prevent particle contamination from the air, as well as to act as a trap for volatile compounds
- Volume of test solution: 500 mL surface water (Batch 20191107) / vessel
- Test temperature: 12 +/- 2°C
- Light conditions: Dark
- Test item concentrations: 3µg/L and 15 µg/L
- Number of culture flasks/concentration: 16 (8 flasks/concentraion were analysed)
- Number of steril samples: 6 treated with 15 µg/L test item (all were alanysed)
- Number of reference samples: 8 treated with 4.9 µg/L [14C] sodium benzoate (4 were analysed)
- Number of blank controls: 5 treated with the highest amount of solvent
- Method used to create aerobic conditions: Aerated by a slightly orbital movement of the test vessel on an orbital shaker
- Sampling intervals: test item 0, 6, 14, 78 days after treatment (duplicates) / reference item 0 and 7 days after treatment (duplicates)
- Sample storage before analysis: Samples were analysed on the same day as sampling or stored at ≤-18°C
- pH-value and dissolved oxygen concentration of the water phase were measured in the blank controls once a week
- Adsorption test: The test item adsorbed to the wall of the vessel were extracted with toluene (more details see "Details on analytic methods")

II: CLOSED SYSTEM WITH TENAX TUBES
- Test vessels: 1000 mL all-glass flasks closed with an air tight cap provided with a septum to allow for gas phase sampling
- Volume of test solution: 500 mL surface water (Batch 20191107) / vessel
- Test temperature: 12 +/- 2°C
- Light conditions: Dark
- Test item concentrations: 3µg/L and 15 µg/L
- Number of culture flasks/concentration: 4 (all 8 flaskswere analysed)
- Method used to create aerobic conditions: Aerated by a slightly orbital movement of the test vessel on an orbital shaker
- Sampling: At 7 DAT the gas phase of the treated vessels was pumped for 30 minutes through two Tenax® tubes
- Adsorption test: The test item adsorbed to the wall of the vessel were extracted with toluene (more details see "Details on analytic methods")

III: CLOSED SYSTEM WITH ACTIVATED C-TUBES AND SOLVENT TRAPS
- Test vessels: 1000 mL all-glass flasks closed with an air tight cap provided with a septum to allow for gas phase sampling
- Volume of test solution: 500 mL surface water (Batch 20191218) / vessel
- Test temperature: 12 +/- 2°C
- Light conditions: Dark
- Test item concentrations: 3µg/L and 15 µg/L
- Number of culture flasks/concentration: 12 (6 flasks/concentraion were analysed)
- Number of steril samples: 4 treated with 15 µg/L test item (all were alanysed)
- Number of reference samples: 8 treated with 4.9 µg/L [14C] sodium benzoate (4 were analysed)
- Number of blank controls: 5 treated with the highest amount of solvent
- Method used to create aerobic conditions: Aerated by a slightly orbital movement of the test vessel on an orbital shaker
- pH-value and dissolved oxygen concentration of the water phase were measured in the blank controls once a week
- Adsorption test: The test item adsorbed to the wall of the vessel were extracted with toluene (more details see "Details on analytic methods")

Reference substance:

benzoic acid, sodium salt

Compartment:

other: natural water (open system)

Remarks on result:

other:

Remarks:

Recoveries of the 5 measured isomers in the water phase at 6 DAT ranged between 4.1 % and 20 % for the open system

Compartment:

other: natural water (closed system)

Remarks on result:

other:

Remarks:

Recoveries of the 5 measured isomers in the water phase at 7 DAT ranged between 3.2 % and 43 % for the closed systems.

Compartment:

other: steril control samples

Remarks on result:

other:

Remarks:

Recoveries of the 5 measured isomers in the water phase for the steril test samples at 14 DAT ranged between 20 % and 39%.

Parameter:

test mat. analysis

Remarks on result:

not determinable because of methodological limitations

Remarks:

Low recovery rates were observed in all test designs (<43% after 6-7 days). Since a significant decrease of the test item observed in the sterile control as well, it can be assumed that no biological degradation took place.

Compartment:

natural water

Temp.:

12 °C

Remarks on result:

not determinable because of methodological limitations

Remarks:

Low recovery rates were observed in all test designs (<43% after 6-7 days). Since a significant decrease of the test item observed in the sterile control as well, it can be assumed that no biological degradation took place.

Transformation products:

no

Evaporation of parent compound:

yes

Remarks:

Evaporation was observed. The test item was found in different types of traps for volatile compounds: Tenax® tubes: up to 12 % , activated carbon tubes up to 1.2 % and solvent traps up to 0.44 %.

Volatile metabolites:

no

Remarks:

no determination due to methodological limitations

Residues:

no

Results with reference substance:

The test systems were tested to be microbial active with the reference substance sodium benzoate. At 7 DAT 77.8% AR (Batch 20191107) and 88.2% AR (Batch 20191218) of the reference item was mineralized. Thus, the system was biologically active.

Reference 3

Endpoint:

biodegradation in water: sediment simulation testing

Data waiving:

study technically not feasible

Justification for data waiving:

other:

Transformation products:

no

Reference 4

Endpoint:

biodegradation in water: sediment simulation testing

Type of information:

(Q)SAR

Remarks:

Diisopropyl biphenyl isomer mixture (DIPB; CAS-No.: 69009-90-1) represents one main constituent of the registered UVCB (Alkylation and transalkylation products of biphenyl with propene)

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

results derived from a valid (Q)SAR model and falling into its applicability domain, with adequate and reliable documentation / justification

Justification for type of information:

1. SOFTWARE
Vega version 1.1.4

2. MODEL (incl. version number)
Persistence in sediment Model version 1.0.0

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
See “Test material information”

4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
See attached information on the model provided by the developer. Further information on the OECD criteria as outlined by the applicant is provided below under "Any other information of materials and methods incl. tables"

5. APPLICABILITY DOMAIN
See attached information and information as provided in "Any other information on results incl. tables".

6. ADEQUACY OF THE RESULT
See assessment of adequacy as outlined in the "Overall remarks, attachments" section.

Qualifier:

according to guideline

Guideline:

other: REACH Guidance on QSARs R.6

Principles of method if other than guideline:

- Software tool(s) used including version: Vega v1.1.4
- Model(s) used: Persistence in sediment Model version 1.0.0

Full reference and details of the used formulas can be found in:
A. Manganaro, F. Pizzo, A. Lombardo, A. Pogliaghi, E. Benfenati, “Predicting persistence in the sediment compartment with a new automatic software based on the k-Nearest Neighbor (k-NN) algorithm”, Chemosphere (2015), accepted paper.
Gouin, T., Cousins, I., Mackay, D., “Comparison of two methods for obtaining degradation halflives”, Chemosphere 56, 2004, 531-535
Gramatica, P., Papa, E., “Screening and ranking of POPs for Global Half-Life: QSAR approaches for prioritization based on molecular structure”, Environ. Sci. Technol. 41, 2007, 2833-9.

- Model description: see field 'Justification for non-standard information', 'Attached justification' and 'any other information on Material and methods'
- Justification of QSAR prediction: see field 'Justification for type of information', 'Attached justification' and/or 'overall remarks'

GLP compliance:

no

Radiolabelling:

no

Oxygen conditions:

aerobic

Remarks on result:

other: DIPB was predicted to be P/vP

Transformation products:

not specified

For detailed information on the results please refer to the attached report.

Validity criteria fulfilled:

not applicable

Description of key information

Alkylation and transalkylation products of biphenyl with propene is an UVCB substance composed of different constituents. Each constituent is present as a mixture of isomers with unknown constituents. Based on the complex composition in combination with the physico-chemical properties of the substance biodegradation simulation testing is technically not feasible. This was assessed within a feasibility study conducted according to OECD 309 guideline. In a weight of evidence approach, considering study results and QSAR estimates for the main constituents of the UVCB, it was concluded that alkylation and transalkylation products of biphenyl with propene is potentially persistent or very persistent.

Additional information

Based on the complex composition in combination with the physico-chemical properties of the substance biodegradation simulation testing is considered as technically not feasible. This was assessed within a feasibility study conducted according to OECD 309 guideline (see below). Persistence in sediment was estimated by QSAR calculations for the two main constituents DIPB and TIPB. These QSAR results were used in a weight of evidence approach for the persistence assessment of the UVCB substance.

Biodegradation simulation tests (feasibility test in surface water)

Simulation degradation tests in surface water were performed according to OECD 309 with non-labeled test item.

The substance is a reaction product of biphenyl with propene. The alkylation and transalkylation of biphenyl is not stereoselective, and can be either a monofunctional, bifunctional or trifunctional reaction, which will lead to a mixture of mono-, di- and tri-substituted biphenyl isomers as products (namely MIPBs, DIPBs and TIPBs).

The main constituents of the UVCB are DIPB isomers with a typical concentration of approximately 80% (w/w) and TIPB isomers with a typical concentration of approximately 15% (w/w). These isomers together with the other constituents of the UVCB give more than 55 peaks in the GC-chromatogram of a representative substance sample. From all detected peaks of the GC diagram only around 20 can be assigned to mono-, di- and tri-substituted biphenyl isomers, whereas the others peaks represent further minor constituents, of which the most are unknown.

It is technically not possible to identify and quantify all peaks detected in the GC analysis. And it is not possible to distinguish between the stereoisomers of the constituents (MIPB, DIPB and TIPB) by GC-MS, because they present the same ion fragments.

Since not all of the stereoisomers can be technically identified and quantified it was necessary to select representative analytes (isomers) for the degradation measurement in the OECD 309 study. One criterion for the selection of representative analytes was the limit of detection (LOD) and quantification (LOQ). Due to the low solubility of the test item of approximately 33 µg/L an application rate of 15 µg/L was chosen as high application rate in the feasibility test which is below the standard rate of 100 µg/L. The low application rate was set to 3 µg/L. Due to these low concentrations it was necessary to find appropriate extraction methods for quantification and identification of the analytes. This required a series of pre-tests, in order to develop appropriate instrumental and extraction methods to identify and subsequently analyse the test item. The four most abundant isomers of DIPB (i.e. DIPB1, DIPB2, DIPB3 and DIPB4; arbitrary names) and the most abundant isomer of TIPB (TIPB1) were selected as representatives for the UVCB substance (>90% of the constituents of the UVCB substance are covered). Finally, the chromatographic conditions were optimized in GC-MS analysis and a column with a different stationary phase (DB-5MS, J & W Scientific) was further used for a better peak resolution. A LOQ value of 0.3 µg/L was set for all five selected analytes. A LOD value of 0.03 µg/L was set for DIPB isomers and a LOD value of 0.1 µg/L was set for TIPB1. The conduction of the pre-tests took more than a year to complete.

The repeatability of the extraction method was performed by analysing five replicates at 0.3 µg/L (10 % of lowest application rate) and five replicates at 16.5 µg/L (110% of the highest application rate). Mean recoveries ranged from 108 % to 117 % and between 100 % and 109 % for the low and high application rates, respectively. Relative standard deviation values ranged from 2 % to 12 %. An overall mean recovery of 108 % ± 7 % was obtained, thus showing that the extraction method is repeatable. The mean procedural recovery values on the day of extraction were within 70-110% and the method is therefore considered to be reliable.

The feasibility of the test was assessed in three main types of experimental designs: open system, closed system with tubes (Tenax® or activated carbon) and closed system with solvent (toluene) traps. The test water (natural surface water) was incubated in the dark at 12 ±2°C with slightly constant orbital movement of the test vessel. The incubation period after treatment was 78 days for the open system and 7 days for the closed systems. Duplicate samples were taken for analysis at specified intervals for 0, 8, 13 and 78 days after treatment (DAT) for the open system and for 0 and 7 DAT for the closed systems. The identification and quantification of the selected analytes was done by using GC-MS as analytical method.

There was a significant decrease in test item concentration at 6 DAT in the open and 7 DAT in the closed systems. Recoveries of the test item in the water phase ranged between 4.1 % and 20 % for the open system and at between 3.2 % and 43 % for the closed systems. This decrease was similar in the sterile samples, which indicates the absence of biological degradation. The presence of test item in the different traps for volatile compounds observed a loss by evaporation. The recovery of the applied analytes in the traps ranged from <LOD to 12 % for the Tenax® tubes, from <LOD to 1.2 % in the activated carbon tubes and from <LOD to 0.44 % in the solvent traps.

It can be concluded that the experimental designs, which were tested in this study, were not suitable for determining the degradation rate of the test item in natural aerobic surface water. In the open system, the constant gas phase exchange between the bottle gas phase and the air produces a high loss of the test item. In the closed system, the test item is confined to the bottle headspace. From the three different traps for volatiles tested in this study, the Tenax® tubes showed the highest trapping efficiency. However, the amount of test item recovered from the gas phase by the Tenax® tubes did not account for the total decrease of test item in the water phase. Based on the results of this study, it is not possible to provide conclusive remarks about the reason for the incomplete mass balance. The loss of test item might be due to incomplete trapping efficiency of the Tenax® tubes. The absence of biological degradation was indicated by the analysis of sterile samples.

In conclusion, an aerobic mineralisation study in surface water according to OECD 309 can be considered technically not feasible due to the physico-chemical properties of the substance (e.g. evaporation of the substance from the water phase takes place). Furthermore, based on the low solubility of the substance in combination with the complex composition of this UVCB substance, the adequate analytical methods on the identification and quantification of the substance are only limited to some of the most abundant constituents. For these reasons no further simulation tests for alkylation and transalkylation products of biphenyl with propene were conducted.

QSAR predictions for sediment/water system)

Persistence in sediment was estimated by QSAR calculations for the two main constituents DIPB and TIPB. These QSAR results were used in a weight of evidence approach for the persistence assessment of the UVCB substance.

For the prediction of the persistence of DIPB and TIPB in sediment/water systems the VEGA 1.1.4 “Persistence sediment model” (IRFMN) 1.0.0 was used. Both constituents (DIPB and TIPB) fall within the applicability of the model. The prediction is persistent (P) and/or very persistent (vP) for DIPB and very persistent (vP) for TIPB, respectively. For performance of the model on similar molecules is good (DIPB) to moderate (TIPB), even though isopropyl chains are missing in the list of the most similar substances in the training set of the model. The prediction is considered to be valid and is used as information within a weight of evidence approach for the persistency assessment of the substance.