Benzyltoluene

Bioaccumulation: aquatic / sediment

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

bioaccumulation in aquatic species: fish

Type of information:

(Q)SAR

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:

Based on the results of the aerobic mineralisation study OECD 309 with two relevant constituents of Dibenzyltoluene (CAS 53585-53-8): o,m DBT and o,o DTPM, and one relevant impurity (tested in the OECD 309 study), the BCF calculations of these three compounds were refined using the US EPA EPISUITE software, which is considered a QSAR model prediction tool of particular relevance and interest in accordance with the ECHA Guidance on Information Requirements and Chemical Safety Assessment, Chapter R.11 (PBT/vPvB assessment).

Principles of method if other than guideline:

B assessments were conducted for each relevant compounds using the US EPA EPISUITE software KOWWIN v.1.68 and BCFBAF v3.01.

GLP compliance:

not specified

Key result

Type:

BCF

Value:

2 169 L/kg

Calculation basis:

other: regression based

Remarks on result:

other: relevant impurity

Key result

Type:

BCF

Value:

8 513 L/kg

Calculation basis:

other: regression based

Remarks on result:

other: o,o-DPTM

Key result

Type:

BCF

Value:

10 280 L/kg

Calculation basis:

other: regression based

Remarks on result:

other: o,m-DBT

Validity criteria fulfilled:

not applicable

Conclusions:

The estimated BCF value is 10 280 L/kg wet-wt for the compound o,m-DBT, meaning that this compound is potentially very bioaccumulable.
The estimated BCF value is 8513 L/kg wet-wt for the compound o,o-DTPM, meaning that this compound is potentially very bioaccumulable.
The estimated BCF value is 2169 L/kg wet-wt for the relevant impurity of DBT substance, meaning that this compound is potentially bioaccumulable.

Executive summary:

Summary Results for the relevant impurity:
Log BCF (regression-based estimate): 3.34 (BCF = 2.17e+003 L/kg wet-wt)
Biotransformation Half-Life (days) : 6.34 (normalized to 10 g fish)
Log BAF (Arnot-Gobas upper trophic): 3.29 (BAF = 1.95e+003 L/kg wet-wt)

 

Summary Results for o,o-DTPM:
Log BCF (regression-based estimate): 3.93 (BCF = 8.51e+003 L/kg wet-wt)
Biotransformation Half-Life (days) : 16.7 (normalized to 10 g fish)
Log BAF (Arnot-Gobas upper trophic): 4.94 (BAF = 8.65e+004 L/kg wet-wt)

 

Summary Results for o,m-DBT:
Log BCF (regression-based estimate): 4.01 (BCF = 1.03e+004 L/kg wet-wt)
Biotransformation Half-Life (days) : 3.43 (normalized to 10 g fish)
Log BAF (Arnot-Gobas upper trophic): 5.67 (BAF = 4.66e+005 L/kg wet-wt)

Reference 2

Endpoint:

bioaccumulation in aquatic species: fish

Type of information:

(Q)SAR

Adequacy of study:

key study

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:

QSAR prediction

Principles of method if other than guideline:

calculation of BCF from experimental log Kow = 6.38, according to accepted model.

Key result

Type:

BCF

Value:

7 525 L/kg

Calculation basis:

other: regression based

Validity criteria fulfilled:

not applicable

Conclusions:

The estimated BCF is 7525 L/kg wet-wt, meaning that the substance is potentially bioaccumulable.

Executive summary:

Summary Results:

Log BCF (regression-based estimate): 3.88 (BCF = 7.53e+003 L/kg wet-wt)

Biotransformation Half-Life (days) : 2.97 (normalized to 10 g fish)

Log BAF (Arnot-Gobas upper trophic): 5.55 (BAF = 3.57e+005 L/kg wet-wt)

Reference 3

Endpoint:

bioaccumulation in aquatic species: fish

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

from 1991-12-19 to 1992-02-27

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

OECD Guideline 305 C (Bioaccumulation: Test for the Degree of Bioconcentration in Fish)

GLP compliance:

yes

Radiolabelling:

no

Details on sampling:

- Sampling intervals/frequency for test organisms: 1, 2, 3, 4, 6, 7 and 8 weeks
- Sample storage conditions before analysis: not mentioned
- Details on sampling and analysis of test organisms and test media samples (e.g. sample preparation, analytical methods): fish with freeze drying

Vehicle:

yes

Details on preparation of test solutions, spiked fish food or sediment:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: 1 g test substance + 1 g vehicle /L, no further details mentioned
- Controls: yes, blank and vehicle control
- Chemical name of vehicle (organic solvent, emulsifier or dispersant): Castor oil , ethoxylated (40 EO)
- Concentration of vehicle in test medium (stock solution and final test solution(s) including control(s)): stock solution: 1 g/L; final test solutions: same as test material, vehicle control: 0; 20 and 200 µg/L
- Evidence of undissolved material (e.g. precipitate, surface film, etc): nothing mentioned

Test organisms (species):

Cyprinus carpio

Details on test organisms:

TEST ORGANISM
- Common name: Carp
- Strain: cyprinus carpio
- Source: Limnotherm, Bergheim/Niederaussen, Germany
- Age at study initiation (mean and range, SD): not mentioned
- Length at study initiation (lenght definition, mean, range and SD): 12.9 +/- 1.3 cm
- Weight at study initiation (mean and range, SD): 30.4 +/- 6.7 g
- Health status: not mentioned
- Description of housing/holding area: 260 glass aquariums, flow rate 20 l/h
- Feeding during test: yes
- Food type: Trouvit
- Amount: approx. 1 % of body weight
- Frequency: two times per day

ACCLIMATION
- Acclimation period: 14 days
- Acclimation conditions (same as test or not): The fish were kept in 260 l aquariums in flow rate.
- Type and amount of food: Trouvit, administration in an amount of approx. 0.5 - 1 % of body weight
- Feeding frequency: daily
- Health during acclimation (any mortality observed): only healthy animals used for the test

Route of exposure:

aqueous

Test type:

flow-through

Water / sediment media type:

not specified

Remarks:

freshwater

Total exposure / uptake duration:

8 wk

Total depuration duration:

2 wk

Hardness:

200 mg/L CaCO3

Test temperature:

23 +/- 2 °C

pH:

7.4 - 8.3

Dissolved oxygen:

6.1 - 9.1 mg/L

TOC:

not mentioned

Salinity:

not mentioned

Details on test conditions:

TEST SYSTEM
- Test vessel: aqariums
- Type (delete if not applicable): open
- Material, size, headspace, fill volume: glass
- Aeration: Yes
- Type of flow-through (e.g. peristaltic or proportional diluter): not mentioned
- Renewal rate of test solution (frequency/flow rate): not mentioned
- No. of organisms per vessel: 50
- No. of vessels per concentration (replicates): 1
- No. of vessels per control / vehicle control (replicates): 1
- Biomass loading rate: not mentioned

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: tapewater dechlorinated with charcoal filtered
- Holding medium different from test medium: no

OTHER TEST CONDITIONS
- Adjustment of pH: no
- Photoperiod: not mentioned
- Light intensity: not mentioned

Nominal and measured concentrations:

nominal concentrations tested : 20 and 200 µg/L

Reference substance (positive control):

no

Details on estimation of bioconcentration:

BASIS INFORMATION
- Measured/calculated logPow: 4.73

BASIS FOR CALCULATION OF BCF
- Estimation: BCF = Concentration in Fish (mg/kg) / Concentration in Water (mg/L)

Key result

Type:

BCF

Value:

2 000 dimensionless

Basis:

whole body w.w.

Time of plateau:

8 wk

Calculation basis:

steady state

Remarks on result:

other: Conc.in environment / dose:20 µg/L

Key result

Type:

BCF

Value:

9 700 dimensionless

Basis:

whole body d.w.

Time of plateau:

8 wk

Calculation basis:

steady state

Remarks on result:

other: Conc.in environment / dose:20 µg/L

Key result

Type:

BCF

Value:

54 000 dimensionless

Basis:

total lipid content

Time of plateau:

8 wk

Calculation basis:

steady state

Remarks on result:

other: Conc.in environment / dose:20 µg/L

Key result

Type:

BCF

Value:

6 300 dimensionless

Basis:

whole body w.w.

Time of plateau:

8 wk

Calculation basis:

steady state

Remarks on result:

other: Conc.in environment / dose:200 µg/L

Key result

Type:

BCF

Value:

28 000 dimensionless

Basis:

whole body d.w.

Time of plateau:

8 wk

Calculation basis:

steady state

Remarks on result:

other: Conc.in environment / dose:200 µg/L

Key result

Type:

BCF

Value:

130 000 dimensionless

Basis:

total lipid content

Time of plateau:

8 wk

Calculation basis:

steady state

Remarks on result:

other: Conc.in environment / dose:200 µg/L

Key result

Elimination:

yes

Parameter:

other: BCF clear decreased

Depuration time (DT):

14 d

Details on kinetic parameters:

not performed

Details on results:

- Mortality of test organisms: no mortalities were observed
- Behavioural abnormalities: not mentioned
- Mortality and/or behavioural abnormalities of control: no

	Concentration: 20 µg/L			Concentration: 200 µg/L
Week	BCF w.w.	BCF d.w.	BCF lipid	BCF w.w.	BCF d.w.	BCF lipid
1	321	1580	5160	905	4063	14028
2	897	3985	17000	1563	7180	32190
3	1558	7385	37442	2593	12049	44353
4	697	3424	17091	2694	12061	54744
6	2593	12630	75963	7092	34195	142713
7	2185	10296	56000	6713	29236	99431
8	1481	6963	37852	5497	25623	131055
depuration
9	1926	8741	43482	2558	12743	77967
10	1370	6481	28555	2169	11618	53989

Validity criteria fulfilled:

not specified

Conclusions:

Fish BCF (8w) = 6300 (wet weight)

Executive summary:

The substance was tested according to the OECD 305C guideline with the nominal concentrations of 20 and 200 μg/L. The test concentrations of 9 μg/L and 61 μg/L over the entire course of the test were calculated from the weighted mean values of the analysis. The calculated BCF values show that the substance accumulates rapidly in the fish. The following bioconcentration factors were achieved within the test period of 8 weeks : 

Concentrations (nominal)	BCF (8 weeks) related to
	wet weight	dry weight	total lipid content
20 µg/L	2000	9700	54000
200 µg/L	6300	28000	130000

During the subsequent 14-day release phase, a clear reduction of the substance concentration in the fish was visible. The general behavior of the exposed animals showed no differences from the controls. Food consumption was normal at all test concentrations.

Description of key information

The registered substance contains concentration > 0.1 % of a PBT/ vPvB compound. According to the Echa Guidance R11 related to the PBT/vPvB assessment, in that case, the registered substance has also to be considered as a PBT/vPvB substance.

Therefore, this section 5.3.1 has been completed with the available data on bioaccumulation for the relevant impurity (Dibenzyltoluene: CAS 53585-53-8).

For this relevant impurity,

- the estimated fish BCF value using QSAR BCFBAF v3.00 from EpiWin 4.00 is 7525 L/kg wet/wt, meaning that this impurity is potentially bioaccumulative.

- This result is corroborated by an experimental study following an OECD 305C guidance leading to a BCF value equal to 6300 L/kg (wet wt).

- Moreover, the BCF calculations of the three compounds tested in the OECD 309 study with Dibenzyltoluene (CAS 53585-53-8): o,m-DBT, o,o-DTPM, and the relevant impurity were performed using the US EPA EPISUITE solftware, which is considered a QSAR model prediction tool of particular relevance and interest in accordance with the ECHA guidance on Information Requirements and Chemical Safety Assessment, Chapter R11 (PBT/vPvB assessment).

 

Key value for chemical safety assessment

BCF (aquatic species):

7 525 L/kg ww

Additional information

A calculated BCF is obtained with BCFBAF model from the EPI Suite (US-EPA), based on hydrophobicity. The result obtained corresponds to a computed log Kow of 6.5, in agreement with the experimental value of this parameter determined through an OECD 117. The experimental study confirms the calculated BCF.

The estimated BCF values is 10 280 L/kg wet-wt for the compound o,m-DBT, meaning that this compound is potentially very bioaccumulable.
The estimated BCF values is 8 513 L/kg wet-wt for the compound o,o-DTPM, meaning that this compound is potentially very bioaccumulable.
The estimated BCF values is 2 169 L/kg wet-wt for the relevant impurity of DBT substance, meaning that this compound is potentially bioaccumulable.