Dibenzylbenzene, ar-methyl derivative

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Test procedure in accordance with generally accepted scientific standards.

Qualifier:

no guideline followed

Principles of method if other than guideline:

Substance is the sole carbon source (mineral medium) at low concentration in presence of a non adapted inoculum. Incubation and periodic analysis of substance concentration by gas chromatography and aromatic ring decay by UV spectroscopy. Incubation took place during 149 days

GLP compliance:

no

Oxygen conditions:

aerobic

Inoculum or test system:

mixture of sewage, soil and natural water

Details on inoculum:

Mixture of river water and secondary effluent from WWTP.
- Water sampled in river Seine (Levallois-Perret) is filtered through 0.22 µm. The filter is re-suspended in water such as to concentrate it 100 times
- Effluent from a sewage treatment plant treating domestic wastewater (city of Versailles) is filtered on paper, filtrate is centrifuged, bottom collected and re-suspended such as to concentrate the original sample 50 times.
Both resulting sources are mixed (2/3 river, 1/3 effluent) and flasks are inoculated with 1% of final volume.
CFU concentration is 3*E6 bacteria/ml (TotalCount Millipore)

Duration of test (contact time):

149 d

Initial conc.:

10 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

test mat. analysis

Remarks:

gas chromatography

Parameter followed for biodegradation estimation:

other: UV lambdamax 256 nm (aromatic rings)

Details on study design:

Several series are prepared in parallel.
TEST CONDITIONS
- Composition of medium: as described in OECD Guideline 301E
- Solubilising agent (type and concentration if used): acetone stock solutions are used to introduce the substance into flasks but acetone is evaporated before addition of test medium
- Test temperature: 20°C
- pH: 7.4
- pH adjusted: no
- Suspended solids concentration: 3*E6 CFU/mL
- Continuous darkness: yes


TEST SYSTEM
- Culturing apparatus: flasks of 500 mL with screwcaps with an inner PTFE membrane.
- Number of culture flasks/concentration: 19 (6 for sterile control, 11 for assay, 2 for reference substance)
- Test performed in closed vessels due to significant volatility of test substance: yes
- Flasks are incubated on orbital shakers


SAMPLING
- Sampling frequency: T = 0, 6, 20, 62, 105, 149 days
- Sampling method: at T = 0, one assay and one assay series flasks are extracted, then one sterile and two assay flasks on reaining sampling occasions
- Sterility check if applicable: no
- Sample storage before analysis: immediate extraction
- Other: reference substance biodegradation is check by DOC analysis on duplicate flasks


CONTROL AND BLANK SYSTEM
- Inoculum blank: no
- Abiotic sterile control: inoculum is replaced by 1.5 mL of mercuric chloride solution 1g/L
- Toxicity control: no
- Other: inoculum control with reference substance


STATISTICAL METHODS:

Reference substance:

benzoic acid, sodium salt

Remarks:

40 mgC/L

Parameter:

other: aromatic ring decay (UV)

Value:

67

Sampling time:

149 d

Remarks on result:

other: ultimate biodegradation

Parameter:

% degradation (test mat. analysis)

Value:

94

Sampling time:

149 d

Remarks on result:

other: primary biodegradation

Parameter:

% degradation (test mat. analysis)

Value:

65

Sampling time:

62 d

Remarks on result:

other: primary degradation

Details on results:

see table below

Results with reference substance:

sodium benzoate ultimate biodegradation is 70% in 8 days.

Primary degradation (GC)

Day	% deg. abiotic	%deg. biotic1	%deg. biotic2	Mean %deg. biotic
0	-5	1	1	1
6	4	1	7	4
20	5	11	9	10
62	-3	63	66	65
105	9	63	63	63
149	11	94	93	94

Ultimate degradation (UV)

Day	% deg. abiotic	%deg. biotic1	%deg. biotic2	Mean %deg. biotic
0	8	4	4	4
6	7	5	5	5
20	5	10	16	13
62	14	74	41	58
105	23	54	47	50
149	14	65	70	67

Validity criteria fulfilled:

not applicable

Interpretation of results:

inherently biodegradable

Conclusions:

This study carried out under general principles of ready biodegradability (moderate substance concentration 10 mg/L and a non adapted inoculum). It is shown that ready biodegradability criteria are not met but, under prolonged incubation conditions, primary and ultimate biodegradation occu. Therefore the substance can be considered as inherently biodegradable.

Executive summary:

Aerobic biodegradation of dibenzyltoluene (commercial name: Jarysol BT 02) has been assessed in a test were substance was introduced in a series of test flasks, with a mineral medium inoculated with microorganisms from a mixture of river water and secondary effluent from WWTP. The flasks, tightly closed, were placed in a thermostated (20°C) shaker in the dark. Along time, flasks were removed, extracted, and remaining substance quantified by gas chromatography. In addition, UV spectroscopy allowed to quantify remaining aromatic rings. It has been shown that dibenzyltoluene is degraded by 65% in 62 days and almost completely (94%) in 149 days. Furthermore, in the same period of time 67% of aromatic rings have been degraded. It is concluded that dibenzyltoluene is inherently biodegradable.

On this basis, French authorities, rapporteur in the TC NES subgroup on identification of PBT and vPvB substances, in charge of assessing PBT status of dibenzyltoluene (substance n°43) have concluded on the removal of this substance from the list of potential PBTs.

In the final decision on CCh number CCH-D-2114432929-37-01/F, Echa has rejected this study and askes to assess the P/vP criterion on degradation simulation study. 

Reference 2

Endpoint:

biodegradation in water: inherent biodegradability

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

1992-08-20 to 1992-09-17

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 302 C (Inherent Biodegradability: Modified MITI Test (II))

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

other: mixture of different strains of micro-organisms (non-acclimated) found in fertile garden soil and sewage effluent

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure):
1. fertile garden soil, sampling site not described
2. final sewage effluent, consisting of primary settlement and a rotating disk bio-filter from a small sewage treatment works at Lake Windermere, UK
- Laboratory culture: no
- Method of cultivation: not applicable
- Storage conditions: not mentioned
- Storage length: Both inocula were prepared and used on the day of collection.
- Preparation of inoculum for exposure:
1. The soil inoculum was prepared from 100 g of soil which had been suspended in 1000 mL of chlorine-free drinking water and stirred for 30 min. After allowing to settle for a further 30 minutes, the supernantant was filtered through Whatman No 1 filter paper, the first 200 mL of the filtrate was discarded, the remaining filtrate were used for the test.
2. Filtration of the effluent through Whatman No 1 filter paper, the first 200 ml of the filtrate was discarded, the remaining filtrate were used for the test.
- Pretreatment: The filtrates used for the test were kept aerobic until required for seeding the test solutions.
- Concentration of sludge: not measured
- Initial cell/biomass concentration: not measured
- Water filtered: not mentioned

Duration of test (contact time):

28 d

Initial conc.:

100 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium: according to guideline with the deviation of using 36.3 g/L CaCl2 x 2 H2O instead of 27.5 g/L CaCl2
- Additional substrate: none
- Solubilising agent (type and concentration if used): not used
- Test temperature: 20 +/- 1 °C
- pH: 7.0 +/- 0.2
- pH adjusted: yes, by addition of 100 µL M NaOH
- CEC (meq/100 g): not mentioned
- Aeration of dilution water: yes
- Suspended solids concentration: not mentioned
- Continuous darkness: yes
- Other: none


TEST SYSTEM
- Culturing apparatus: Test apparatus (Hach) consisting of an amber glass bottles connected to a closed-end mercury manometer.
- Number of culture flasks/concentration: 3 for the BOD of test substance
- Method used to create aerobic conditions: not mentioned
- Method used to create anaerobic conditions: not applicable
- Measuring equipment: constant volume respirometer, measuring of oxygen uptake manometrically
- Test performed in closed vessels due to significant volatility of test substance: no
- Test performed in open system: no
- Details of trap for CO2 and volatile organics if used: Carbon dioxide produced during respiration was absorbed by potassium hydroxide placed in the seal cup.
- Other: The contents of each bottle were individually stirred by a PTFE covered stirrer-bar driven by magnets attached to a motor.


SAMPLING
- Sampling frequency: daily up to day 28
- Sampling method: Oxygen taken up measured as a decrease in pressure by reading directly the BOD (mg/L) on the manometer scale
- Sterility check if applicable: not applicable
- Sample storage before analysis: no storage
- Other: none


CONTROL AND BLANK SYSTEM
- Inoculum blank: yes, one blank (dilution water reagents and inoculum)
- Abiotic sterile control: none
- Toxicity control: none
- Other: one adsorption control (100 mg/l test substance made up in deionised water without inoculum)


STATISTICAL METHODS: no statistics performed

Reference substance:

acetic acid, sodium salt

Remarks:

68.3 mg/L

Preliminary study:

not performed

Test performance:

100 mg/L test material was used for the test. At this concentration oily droplets of the test substance remained undissolved at the bottom, strong agitation with a homogenizer broke the droplets down and a slightly cloudy white emulsion resulted. Aerated deionised water was used to make up the test solution to which the dilution water reagents were added. The pH was checked and adjusted to 7.0, followed by the addition of 5 mL/L of each inoculum, and then the solution was made up to the mark on the volumetric flask. The appropiate volumes of samples were introduced into the test bottles and initially loose connections were made to the manometers. After allowing thermal equilibrium to become established (1 hr) the manometer and bottle screw caps were tightened, and the manometer scales adjusted by setting the zero mark on the scale level with the top of the mercury columns. Daily BOD measurements were recorded over the 28 day test period.

Parameter:

% degradation (O2 consumption)

Value:

0.2

Sampling time:

28 d

Details on results:

see below

Results with reference substance:

The control solution showed 68.9 % degradation at day 7 (details see below)

Table: Degradation kinetics

Sampling time [days]	Biodegradation [% ]
	test vessel 1	test vessel 2	test vessel 3	reference control
1	0	0	0	0
3	0	0	0	29.2
4	0	0	0	46.8
5	0.1	0.3	0	52.8
6	0	0.3	0	62.7
7	0.1	0.3	0	68.9
8	0	0.3	0	73.6
11	0.1	0.3	0	79.4
12	0.1	0.3	0	81.5
13	0.1	0.3	0	82.0
14	0.1	0.3	0	82.4
15	0.1	0.3	0	82.8
18	0.1	0.3	0	83.3
19	0.1	0.3	0	83.3
20	0.1	0.3	0	83.3
21	0.1	0.4	0	83.3
22	0.1	0.4	0	83.7
25	0.1	0.4	0	83.3
26	0.1	0.4	0	83.3
27	0.1	0.4	0	83.3
28	0.1	0.4	0	83.3

Validity criteria fulfilled:

yes

Interpretation of results:

under test conditions no biodegradation observed

Conclusions:

It was concluded that Marlotherm S was non-biodegradable under these test conditions.

Reference 3

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

1994-09-28 to 1994-10-27

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)

Deviations:

yes

Remarks:

At days 11 and 12 the temperature was increased due to an air condition fault, this was judged to have no influence on the test results.

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: domestic sewage plant (Marl-East, Germany)
- Laboratory culture: no
- Storage conditions: not mentioned
- Storage length: not mentioned
- Preparation of inoculum for exposure: according to prescipt (not specified)
- Pretreatment: not mentioned
- Concentration of sludge: 23.5 mg/L suspended solids; dry weight of inoculum: 3.922 g/L
- Initial cell/biomass concentration: 220x10E3 cfu/mL (colony forming units/mL)
- Water filtered: not mentioned

Duration of test (contact time):

29 d

Initial conc.:

16.2 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium: not specified
- Additional substrate: none
- Solubilising agent (type and concentration if used): not used
- Test temperature: 20.7 - 33.4 °C
- pH: 6.6 (measured on day 28)
- pH adjusted: no
- Aeration of dilution water: not specified
- Suspended solids concentration: 23.5 mg/L
- Continuous darkness: not mentioned
- Other: none

TEST SYSTEM
- Culturing apparatus: 5000 ml glass vessels containing culture samples
- Number of culture flasks/concentration: 2 bottles, one concentration
- Method used to create aerobic conditions: not mentioned
- Method used to create anaerobic conditions: not applicable
- Measuring equipment: carbon analyzer (Shimadzu)
- Details of trap for CO2: collection of carbon dioxide as sodium carbonate with sodium hydroxide solution (no further details mentioned)
- Other: none


SAMPLING
- Sampling frequency: on days 0, 1, 6, 9, 14, 19, 23, 28 and 29
- Sampling method: not mentioned
- Sample storage before analysis: not mentioned
- Other: none


CONTROL AND BLANK SYSTEM
- Inoculum blank: yes (2 vessels with inoculum without test substance)
- Abiotic sterile control: not performed
- Toxicity control: not performed
- Other: none


STATISTICAL METHODS: no statistics performed

Reference substance:

benzoic acid, sodium salt

Remarks:

25 mg/L final test medium (14.6 mg DOC/L)

Preliminary study:

not performed

Test performance:

Procedure: The test substance was weighed into a weighing vessel (Eppendorf, 0.7 mL) and given with this vessel into a defined, liquid mineral medium, which was inoculated with an inoculum from activated sludge and aerated at 20.7 - 33.4 °C. The released CO2 is bound in caustic soda solution in the form of sodium carbonate. The degradation was followed over the duration of the test of 29 days at the days of sampling as stated above via a TIC analysis (total inorganic carbon) of the bound CO2. One day before the end of the test (28th day) a pH-measurement was conducted and the remaining dissolved CO2 was driven out by acidification of the test preparation, the degradation values ascertained on the 29th day (end of incubation) are therefore related to the 28th day.
Preparation of the mineral medium: Two days before the beginning of the test (addition of the test substance) 35 L of the mineral medium were prepared and aerated overnight. On the following day 2400 mL were filled into the individual test containers and, after inoculation with the inolculum, filled with the mineral medium up to 3 L.
Dosage of the test material: The test material was weighed exactly by means of a weighing aid (reaction vessel from Eppendorf, cut-off cover) and was put into the test vessels together with the weighing aid.

Key result

Parameter:

% degradation (CO2 evolution)

Value:

ca. 1

Sampling time:

29 d

Remarks on result:

other: after acidification

Details on results:

see below

Results with reference substance:

see below

Table: Degradation kinetic

sampling time [days]	degradation [%]
	test substance			reference substance
	vessel 1	vessel 2	mean
1	2	0	1	28
6	1	0	1	80
9	1	0	1	80
14	-1	0	-1	82
19	0	0	0	82
23	0	1	1	88
28	1	1	1	90
29 (after acifidation)	1	1	1	85

Validity criteria fulfilled:

yes

Interpretation of results:

under test conditions no biodegradation observed

Conclusions:

Under test conditions, no biodegradation observed

Reference 4

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

1990-08-03 to 1990-09-06

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): predominantly domestic sewage plant, Frankfurt/M-Niederrad, Germany
- Laboratory culture: no
- Method of cultivation: not applicable
- Storage conditions: not mentioned
- Storage length: not mentioned
- Preparation of inoculum for exposure: Prior to the use the activated sludge from the sewage plant was washed twice with tap water. After resuspension the sludge was aerated for 4 hours. It was then homogenized in a waring blender at medium speed for 2 minutes and then settled for about 30 minutes. The supernantant was filtered through a coarse filter paper the first 200 ml being discarded. The filtrate was used as inoculum.
- Pretreatment: aeration with CO2-free air for 24 h
- Concentration of sludge: not mentioned
- Initial cell/biomass concentration: not mentioned
- Water filtered: not mentioned

Duration of test (contact time):

45 d

Initial conc.:

10 mg/L

Based on:

test mat.

Initial conc.:

20 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium: according to the guideline
- Additional substrate: none
- Solubilising agent (type and concentration if used): not used
- Test temperature: 20.4 - 25.5 °C (mean 22.9 +/- 1.5 °C)
- pH: not determined
- pH adjusted: no
- CEC (meq/100 g): not mentioned
- Aeration of dilution water: aeration with CO2-free air for 24 h
- Suspended solids concentration: not mentioned
- Continuous darkness: not mentioned
- Other: The duration of the test was extended to 45 days with a second test substance concentration (20 mg/L). This culture was prolonged as biodegradability had started before day 28 and a plateau was not reached until that day.


TEST SYSTEM
- Culturing apparatus: volume of 3.5 L, no further details described
- Number of culture flasks/concentration: one flask/concentration
- Method used to create aerobic conditions: The test solutions being aerated with CO2-free air at a constant aeration rate of 4 L/h, controled by precise flowmeters (Fisher & Porter, Göttingen, Germany)
- Method used to create anaerobic conditions: not applicable
- Measuring equipment: Resting Ba(OH)2 was titrated with 0.05 N HCl.
- Test performed in closed vessels due to significant volatility of test substance: no
- Test performed in open system: not applicable
- Details of trap for CO2 and volatile organics if used: CO2 generated by the test substance was trapped by 0.025 N Ba(OH)2 in a trap system decribed in the guideline.
- Other: none


SAMPLING
- Sampling frequency: days 3, 8, 10, 14, 17, 21, 24, 28, 30, 34, 36, 38, 41, 43, 45
- Sampling method: resting Ba(OH)2 was titrated
- Sterility check if applicable: not applicable
- Sample storage before analysis: not mentioned
- Other: noen


CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Abiotic sterile control: no
- Toxicity control: no
- Other: none


STATISTICAL METHODS: no statitics performed

Reference substance:

benzoic acid, sodium salt

Preliminary study:

not performed

Test performance:

The test solutions contained in a total volume of 3500 mL: 35 mL of the inoculum, 14 mL of the ferrichloride solution, 3.5 mL of the magnesium sulfate solution, 3.5 mL of the calcium chloride solution, 7 mL of the phosphate mixture solution ad 3.5 mL of the ammonium sulfate solution according to the guideline. A stock solution with the test material could not prepared in aqua bidest. For this reason 35.0 mg and 70.0 mg of the test material were weighed into small glass tubes, previously cleaned by treatment with acetone, rinsed with plenty of demin. water, and dried at 104 °C. The glass tubes with the test substance were given into the test solutions at the starting point of the test. At the same time one blank without any test substance but with inoculation and one reference with 20 mg C/L were run in parallel.
CO2 generated by the test substance was trapped by 0.025 N Ba(OH)2 in a trap system described in the guideline. Resting Ba(OH)2 was titrated with 0.05 N HCl. Each mL of HCl titrated - after deduction of the amount of HCl titrated for the blank control - corresponds to 1.1 mg of CO2 produced. Determinations of CO2 were performed after following intervals: days 3, 8, 10, 14, 17, 21, 24, 28, 30, 34, 36, 38, 41, 43, and 43.
At day 28 1 mL conc. HCl was given into the test solution with 10 mg/L of the test material in order to make the dissolved CO2 or inorganic carbon volatile and to purge the system of CO2. Final titration was made at day 30. At day 43 1 mL conc. HCl was given into the test solution with 20 mg/L of the test material. The final titration for this test was made at day 45.

Parameter:

% degradation (CO2 evolution)

Value:

ca. 2.3

Sampling time:

28 d

Remarks on result:

other: 10 mg/L test substance

Parameter:

% degradation (CO2 evolution)

Value:

ca. 28.5

Sampling time:

43 d

Remarks on result:

other: 20 mg/L test substance

Details on results:

see below

Results with reference substance:

Na-benzoate degraded at 77 % within 6 days.

Table: Degradation kinetics

sampling time [days]	% degradation of test substance
	10 mg/L	20 mg/L
3	0	0
8	0	0
10	0.5	0.2
14	0.5	0.2
17	0.5	0.5
21	0.5	1.2
24	0.5	3.5
28	0.5	7.6
30	2.3 (after acidification)	10.5
31		12.0
34		14.5
36		16.7
38		20.6
41		25.1
43		27.4
45		28.5 (after acidification)

Validity criteria fulfilled:

yes

Interpretation of results:

inherently biodegradable

Conclusions:

Marlotherm S was tested for biodegradability according to 'modified Sturm-Test' (OECD Guideline 301 B). Calculated from the organic carbon content of the test substance and the measured CO2 generation 2.3% of the theoretical CO2 (ThCO2) had been generated by the test substance within 28 d in the case of the 10 mg test substance/L - culture. 28.5% of the theoretical CO2 (ThCO2) had been generated by the test substance within 43 d in the case of the 20 mg test substance/L - culture. This culture was prolonged as biodegradability had started before day 28 and a plateau was not reached until that day. From these data obtained Marlotherm S may be regarded as "inherently biodegradable" though biodegradability of this test material seemed to be not fast.

Reference 5

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

1990-05-10 to 1990-06-06

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): effluent of a predominantly domestic sewage plant, Lippeverband (Marl-West), Germany
- Laboratory culture: no
- Method of cultivation: not applicable
- Storage conditions: not mentioned
- Storage length: The effluent was sampled at the day of the beginning of the test
- Preparation of inoculum for exposure: The effluent was filtrated, the first 200 mL were discarded.
- Pretreatment: The inoculum was aerated until required.
- Concentration of sludge: not mentioned
- Initial cell/biomass concentration: not mentioned
- Water filtered: yes
- Type and size of filter used, if any: paper filter (Weißband)

Duration of test (contact time):

28 d

Initial conc.:

2 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium: mineral salt solution, no further details mentioned
- Additional substrate: none
- Solubilising agent (type and concentration if used): acetone, the test substance was dissolved in acetone, the solution was distributed on the walls of the test vessels at room temperature until the acetone evaporated
- Test temperature: 20 +/- 1°C
- pH: not measured
- pH adjusted: no
- CEC (meq/100 g): not mentioned
- Aeration of dilution water: not mentioned
- Suspended solids concentration: not detemined
- Continuous darkness: not mentioned
- Other: none


TEST SYSTEM
- Culturing apparatus: 300 mL BOD glass bottles with ground-in stoppers
- Number of culture flasks/concentration: 2 replicates for each sampling day
- Method used to create aerobic conditions: not mentioned
- Method used to create anaerobic conditions: not applicable
- Measuring equipment: oxygen electrode (WTW)
- Test performed in closed vessels due to significant volatility of test substance: no
- Test performed in open system: no
- Details of trap for CO2 and volatile organics if used: not applicable
- Other: none


SAMPLING
- Sampling frequency: on days 0, 5, 15 and 28
- Sampling method: in every test bottle the O2 concentration was measured
- Sterility check if applicable: not applicable
- Sample storage before analysis: not mentioned
- Other: noen


CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Abiotic sterile control: no
- Toxicity control: no
- Other: none


STATISTICAL METHODS:

Reference substance:

benzoic acid, sodium salt

Remarks:

2 mg/L

Preliminary study:

not performed

Test performance:

Approx. 0.1 g test substance was weighed into a 100 mL graduated flask and refilled to the calibration mark with acetone. The flask was shaken until the test substance was dissolved. Approx. 0.5 - 1.0 mL - according to 2 mg test substance/L - was distributed on the walls of the test vessels at room temperature until the acetone evaporated. The test vessels were filled with culture medium by means of a syphon and closed bubble-free. The preparations were inoculated with 1 drop per liter of the filtrate of the activated sludge. The test vessels were incubated at 20 +/- 1 °C and after 0, 5, 15 resp. 28 days the O2 concentration was measured in every test vessel with an oxygene electrode.

Parameter:

% degradation (O2 consumption)

Value:

0.5

Sampling time:

28 d

Details on results:

0.5 % degradation after 5 days, 0 % after 15 days

Results with reference substance:

6 % degradation after 5 days, 69 % after 15 days, 93 % after 28 days

Validity criteria fulfilled:

yes

Interpretation of results:

under test conditions no biodegradation observed

Conclusions:

Under test conditions, no biodegradation observed

Description of key information

Several studies were available and previously assessed indicating that Dibenzylbenzene, ar-methyl derivative can be considered as inherently biodegradable. 
Nevertheless, a new aerobic mineralisation in surface water study (OECD 309) has been performed. Based on this study, some compounds of Dibenzylbenzene, ar-methyl derivative can be considered as persistent or very persistent.

Key value for chemical safety assessment

Type of water:

freshwater

Additional information

Two studies based on OECD 301 B (CO2 evolution test) have been reported. In one of these studies (Diefenbach 1994), no CO2 evolution is observed in the standard test duration of 28 days. In the other one (Lebertz, 1990), some CO2 evolution is observed in 28 days and the test is prolonged: 28.5% degradation is registered for a total test duration of 45 days.

In two other studies based on oxygene consumption, no biodegradation is observed: Schoeberl, 1990, based on Closed Bottle Test method (OECD 301 D) and Carrick 1992, based on Modified MITI (II) test (OECD 302 C).

Finally, a non standard study has been carried out (Boutonnet, 1990) in conditions similar to a ready biodegradability test: Dibenzylbenzene, ar-methyl derivative is the sole carbon source (mineral medium) at low concentration in presence of a non adapted inoculum. Incubation was done at 20°C and periodic analysis were carried out: substance concentration by gas chromatography and aromatic ring decay by UV spectroscopy. It has been shown that Dibenzylbenzene, ar-methyl derivative is degraded by 65% in 62 days and almost completely (94%) in 149 days. Furthermore, in the same period of time 67% of aromatic rings have been degraded. It is concluded that Dibenzylbenzene, ar-methyl derivative is inherently biodegradable.

Based on this study, French authorities, rapporteur in the TC NES subgroup on identification of PBT and VPVB substances, in charge of assessing PBT status of dibenzyltoluene ( Dibenzylbenzene, ar-methyl derivative, substance n°43) have concluded on the removal of this substance from the list of potential PBTs .

It can be hypothetized that the slow but ultimate biodegradation is limited in speed by the bioavailability of this very poorly soluble substance. By analogy, benzylbenzene that has the same structure, but is slightly more soluble, has shown 46% mineralisation in 28 days during a 301B study.

Nevertheless, additional information on degradation of this substance is available in an aerobic mineralisation in surface water study (OECD 309) indicating that some compounds of dibenzylbenzene, ar-methyl derivative can be considered as persistent or very persistent.