Diisopropylbiphenyl and triisopropylbiphenyl

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

other: Constituent

Remarks:

Monoisopropyl biphenyl isomer mixture (MIPB; CAS-No.: 25640-78-2) represents one constituent of the registered UVCB (Alkylation and transalkylation products of biphenyl with propene)

Adequacy of study:

weight of evidence

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 310 (Ready Biodegradability - CO2 in Sealed Vessels (Headspace Test)

Deviations:

yes

Remarks:

including chemical analysis and CO2-determination

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material (migrated information):
PHYSICO-CHEMICAL PROPERTIES
- Melting point: -15 °C
- Boiling point: > 294 - < 304 °C
- Vapour pressure: <0.01 hPa
- Henry's law constant (for volatie substances):
- Water solubility (under test conditions): approx. 0.5 mg/L
- log Pow: 5.2 - 5.5
- pKa: n.a.
- pH dependance on stability: n.a.

OTHER PROPERTIES (if relevant for this endpoint)
- Adsorption characteristics:
- Toxicity to microorganisms: none

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: Municipal sewage treatment plant, Hildesheim, Germany: Activated sludge from the sewage plant at Hildesheim is well suited, as it receives predominantly municipal sewage and hardly any industrial chemical waste.

- Laboratory culture: The activated sludge was washed twice with chlorine free tap water. After the second washing the settled sludge was
re-suspended in mineral salts medium and was maintained in an aerobic condition by aeration for 2 hours. Thereafter the sludge was
homogenised with a blender. The supernatant was decanted and was maintained in an aerobic condition by aeration with CO2-free air for 6 days.
10 mL/L were used to initiate inoculation.

Duration of test (contact time):

43 d

Initial conc.:

19.65 mg/L

Based on:

test mat.

Initial conc.:

17.7 mg/L

Based on:

other: carbon content

Parameter followed for biodegradation estimation:

test mat. analysis

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium: Mineral salts medium according to OECD 310
- Additional substrate: no
- Solubilising agent (type and concentration if used): no
- Test temperature: 20 +-1 °C
- pH adjusted: no
- Aeration of dilution water: yes
- Suspended solids concentration: no data, instead: colony-forming units (CFU)/volume, which were approx. 3 *10^-3/mL
- Continuous darkness: no, low light condition

TEST SYSTEM
- Culturing apparatus: Headspace flask 120 mL total volume, 80 mL test medium (headspace-to-liquid ratio: 1:2)
- Number of culture flasks/concentration: 3, at test end: 5
- Addition of the test substance: 100 µL of the acetone stock solution were pipetted into the test vessel. Afterwards the test vessel
was left open for 2 h to allow evaporation of the acetone. After the acetone had been completely evaporated, 80 mL test medium
(mineral salts medium and inoculum) were given into the test vessel.
- Method used to create aerobic conditions: aeration of the test medium in the absence of the test substance.
- Measuring equipment: Carbon analyser
- Test performed in closed vessels due to significant volatility of test substance: yes
- Test performed in open system: no
- Details of trap for CO2 and volatile organics if used: no - CO2 was fixed in the test medium by addition of excess NaOH
prior to opening the test vessel.


SAMPLING
- Sampling frequency: variable, in total 10 sampling times
- Sampling method: total content of a test flask

CONTROL AND BLANK SYSTEM
- Inoculum blank: Mineral salts medium + inoculum; triplicates (test end 5 replicates)
- Solvent control: 100 µL acetone + mineral salts medium + inoculum; single
- Abiotic sterile control: 100 µL acetone test item stock solution without inoculum, poisoned with 5 mL/L HgCl2 (10 g/L); duplicate
- Toxicity control: Test item at 19.65 mg/L + reference item 1 at 30 mg/L; triplicates (test end 5 replicates)

STATISTICAL METHODS: To calculate the 95 % confidence interval for the mean percentage biodegradation 5 replicates of test item,
reference item, toxicity control and inoculum control were set up for test end.

Reference substance:

benzoic acid, sodium salt

Reference substance:

other: n-octanol

Parameter:

% degradation (CO2 evolution)

Value:

ca. 58

Sampling time:

28 d

Parameter:

% degradation (CO2 evolution)

Value:

>= 60

Sampling time:

30 d

Parameter:

% degradation (CO2 evolution)

Value:

67

Sampling time:

43 d

Remarks on result:

other: 95% C.I. 63 - 71 %

Parameter:

% degradation (test mat. analysis)

Value:

97

Sampling time:

6 d

Parameter:

% degradation (test mat. analysis)

Value:

> 99

Sampling time:

13 d

Details on results:

see Attached document below

Results with reference substance:

Benzoic acid, sodium salt: 60 % after 6 days, 94 % after 43 days.
n-Octanol: 60 after 6 days, 97 % after 43 days.
Toxicity control: 57 % after 13 days, 87 % after 45 days.

Table 1:   Biodegradation and Confidence Interval of the Test Item MIPB in Comparison

to the Functional Controls and the Toxicity Controls (Report Table 1)

	Biodegradation [%] on Day 43					Confidence Interval on Day 43
Replicates	1	2	3	4	5	P = 95 %
Test Item	67	62	69	65	71	63 – 71
Functional Control 1 (Sodium benzoate)	95	95	94	92	94	92 – 96
Functional Control 2 (n‑Octanol)	98	95	95	96	101	94 – 100
Toxicity Control, Test Item + Reference Item*	85	87	85	85	64**	84 – 88

*)            = Analysed on day 45
**)           = Determined to be an outlier, not taken into account

Table 2: Primary Degradation of the Test Item MIPB: Results and Recovery Rates

of the Specific Chemical Analysis (Report Table 11)

Sampling day	Solvent Control [mg/L]	Abiotic Control [mg/L]		Primary Degra-dation [%]	Test item [mg/L]		Primary Degra-dation [%]
		Replicates	Mean		Replicates	Mean
0	< LOQS	1.397	1.406	‑	1.372	1.385	‑
					1.395
		1.415
					1.388
6	< LOQS	1.275	1.293	8	0.032	0.04	97
					0.066
		1.310
					0.036
13	< LOQS	1.301	1.279	9	n.d.	< LOD	> 99
					< LOD
		1.258
					n.d.

RR      = Recovery rate referring to the concentration at test start

Italic    = < LOQ_M(40 µg/L)

n.d.     = not detectable

Table 3:   CO₂-Production and Biodegradation in the Test Item Samples (Report Table 7)

CO2-Production in mg C/L
Day	P1	P2	P3	P4	P5	Mean	Net MP	Degr. [%]
0	1.72	1.75	1.77			0.42	‑	‑
2	1.98	1.57	1.71			0.42	0.00	0
6	2.69	2.75	2.74			0.76	0.00	0
10	7.94	8.07	6.47			6.00	4.87	28
13	9.92	9.50	8.28			8.04	6.70	38
17	9.53	11.82	12.98			9.95	8.45	48
21	13.76	14.50	13.39			11.85	9.99	56
28	13.05	13.91	(11.42)			12.06	10.33	58*
35	14.90	15.24	14.30			12.76	11.55	65
43	15.16	14.30	15.51	14.69	15.89	13.52	11.85	67

 Mean                 = mean values (NaOH corrected)
Net MP               = netto mean production (corrected for inoculum control values)
Degr.                  = degradation
*)                        = calculated only with P₁and P₂

Validity criteria fulfilled:

yes

Interpretation of results:

inherently biodegradable

Reference 2

Endpoint:

biodegradation in water: ready biodegradability

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:

3 (not reliable)

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

Remarks:

The substance is not compliant with the applicability domain of the model. However, this calculation is used as supporting information and is considered acceptable for this purpose. It is adequately documented and justified. For more detail see field `overall remarks, attachments´.

Justification for type of information:

1. SOFTWARE
Vega version 1.1.4

2. MODEL (incl. version number)
Ready Biodegradability Model (IRFMN) v. 1.0.9

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: Ready biodegradability model (version 1.0.9)

Full reference and details of the used formulas can be found in:
Meylan W.M., Howard P.H., Boethling R.S. et al. Improved Method for Estimating Bioconcentration / Bioaccumulation Factor from Octanol/Water Partition Coefficient. 1999, Environ. Toxicol. Chem. 18(4): 664-672

- 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

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge (adaptation not specified)

Remarks on result:

not determinable

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

The model was not reliable to perform an assessment. However, some information on similar substances are reported (see Table 1 or attached report) which gives hints that the aromatic biphenyl ring system is readily biodegradable whereas the constituent DIPB with its two isopropyl side chains is not readily biodegradable.

Table 1. Model performance on similar substances

name and/or CAS No.	SMILES	Index of similarity to the test compound	Experimental result	Predicted result	Quality of prediction *
92-52-4	c1ccc(cc1)c2ccccc2	0.863	Readily Biodegradable	Not classifiable	N/A
13540-50-6	c1ccc(cc1)Cc2cc(ccc2C)C	0.852	NON Readily Biodegradable	NON Readily Biodegradable	Good
100-18-5	c1cc(ccc1C(C)C)C(C)C	0.85	NON Readily Biodegradable	NON Readily Biodegradable	Good

*difference between experimental and predicted values

Interpretation of results:

not readily biodegradable

Reference 3

Endpoint:

biodegradation in water: ready biodegradability

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)
Ready Biodegradability Model (IRFMN) v. 1.0.9

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: Ready biodegradability model (version 1.0.9)

Full reference and details of the used formulas can be found in:
Meylan W.M., Howard P.H., Boethling R.S. et al. Improved Method for Estimating Bioconcentration / Bioaccumulation Factor from Octanol/Water Partition Coefficient. 1999, Environ. Toxicol. Chem. 18(4): 664-672

- 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

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge (adaptation not specified)

Remarks on result:

not readily biodegradable based on QSAR/QSPR prediction

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

The prediction is “NON readily biodegradable” and the molecule falls within the applicability domain of the model (AD index = 0.912). The measured applicability domain scores achieved good assessment except the similarity index of 0.831 (only moderately similar compounds with known experimental value in the training set been found). Overall, the result appears to be reliable. The performance of the model on similar molecules is good (see Table 2 or attached report).

The model detected an alert related to non ready biodegradability activity, defined by the SMARTS: c1ccc(c(c1)CC)C. Following, the most similar compounds from the model's dataset having the same fragment (1-ethyl-2-methylbenzene) (see Table 1 or attached report)

Table 1. Most similar compounds from the model's dataset having the fragment (1-ethyl-2-methylbenzene)

name and/or CAS No.	SMILES	Index of similarity to the test compound	Experimental result	Predicted result	Quality of prediction *
577-55-9	c1ccc(c(c1)C(C)C)C(C)C	0.788	NON Readily Biodegradable	NON Readily Biodegradable	Good
527-84-4	c1ccc(c(c1)C)C(C)C	0.756	NON Readily Biodegradable	NON Readily Biodegradable	Good
135-01-3	c1ccc(c(c1)CC)CC	0.744	NON Readily Biodegradable	NON Readily Biodegradable	Good

*difference between experimental and predicted values

Table 2. Model performance on similar substances

name and/or CAS No.	SMILES	Index of similarity to the test compound	Experimental result	Predicted result	Quality of prediction *
13540-50-6	c1ccc(cc1)Cc2cc(ccc2C)C	0.818	NON Readily Biodegradable	NON Readily Biodegradable	Good
86-73-7	c1ccc3c(c1)c2ccccc2C3	0.815	NON Readily Biodegradable	NON Readily Biodegradable	Good
35860-37-8	c2cc1c(cc(cc1C(C)C)C(C)C)c(c2)C(C)C	0.867	NON Readily Biodegradable	NON Readily Biodegradable	Good

*difference between experimental and predicted values

Interpretation of results:

not readily biodegradable

Description of key information

Not readily biodegradable based on a weight of evidence assessment for main constituents of the UVCB substance (including QSAR estimates).

Additional information

For Alkylation and transalkylation products of biphenyl with propene no biodegradation screening test in water is available. However, based on experimental data available for the constituent MIPB (monoisopropyl biphenyl) and QSAR estimates for the two main constituents DIPB (diisopropyl biphenyl) and TIPB (triisopropyl biphenyl) it can be concluded that the UVCB substance does not meet the OECD criteria for ready biodegradability.

In an OECD 310 headspace test with a prolonged test duration of 45 days 67% degradation of MIPB was observed. The 10 % adaption phase was reached on day 10, the pass level of 60% was reached on day 30. Based on the result it can be concluded that MIPB does not meet the persistence criteria and can be fully mineralized within a short period of time at environmental conditions.

The ready biodegradability of the main constituents DIPB and TIPB was estimated by QSAR (VEGA 1.1.4; Ready Biodegradability model (IRFMN) 1.0.9). For DIPB the QSAR model was outside of the applicability domain and no prediction on biodegradability was performed. However, the data on similar substances listed in the training set of the model provide valuable information. In the training set experimental data are reported for the biphenyl (CAS 92-52-4) and for 1,4-diisopropylbenzene (CAS 100-18-5) which consists of only one phenyl ring with two isopropyl side chains. According to the presented experimental results the aromatic biphenyl ring system without isopropyl side chains is readily biodegradable, whereas 1,4-diisopropylbenzene is not readily biodegradable. The presented data in combination with the experimental result of the OECD 310 study with MIPB (see above) indicate that the degradability of the biphenyl derivatives decreases with an increasing number of isopropyl chains (biphenyl > MIPB > DIPB > TIPB). This is in line with the QSAR calculation for TIPB predicting no ready biodegradability. The QSAR prediction for TIPB is considered reliable and falls within the applicability domain of the model.

Based on the information on screening test level persistence can only be excluded for MIPB, whereas a final conclusion on the P/vP criterion cannot be drawn for the main constituents DIPB and TIPB.