2-ethylhexyl nitrate

Bioaccumulation: aquatic / sediment

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

bioaccumulation in aquatic species: fish

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

January - May 1989

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

test procedure in accordance with national standard methods with acceptable restrictions

Qualifier:

according to guideline

Guideline:

other: "Study method concerning new chemical substances” provided in Kanpogyo No5, Yakuhatsu No.615 and 49 Kiyoku No.392, 1974

Deviations:

no

GLP compliance:

not specified

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Source (i.e. manufacturer or supplier) and lot/batch number of test material: Mr. Yoshihiro Nishikawa, Japan Cooper, Co., Ltd.
- Lot No.: 630318
- Purity: 100%

Radiolabelling:

no

Vehicle:

no

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

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method:
(1) Feed stock solution preparation
-- First concentration level: 500 mg of the test substance and 20 g of HCO-30 were mixed and made up to a constant volume 100 mL with Tetrahydrofuran to prepare a feed stock solution of 5 mg/mL of the test substance concentration. (HCO-30 concentration: 200 mg/mL)
-- Second concentration level: 10 mL taken from the feed stock solution for the First concentration level was diluted and made up to a constant volume 100 mL with Tetrahydrofuran to prepare a feed stock solution of 0.5 mg/mL of the test substance. (HCO-30 concentration: 20 mg/mL)
-- The feed stock solution was freshly prepared every 7 days for exchange.
(2) Test solution preparation method
The feed stock solution prepared in (1) was fed to a dilution mixture tank using a constant volume pump for supplying chemical solutions. Then it was mixed with a dilution water (Yokohama city tap water, dechlorinated by activated carbon (compliant to Fishery Standard)) supplied by a constant volume pump for supplying dilution water in order to adjust to the nominal concentration of the test solution. Then the test solution was fed to a rearing water tank.
- Controls: 100 mL of the 200 mg/mL HCO-30 - tetrahydrofuran solution was dissolved in 10 L deionized water (HCO-3- concentration: 2 mg/mL). This control solution was fed at the flow rate of 1 L/day to make the concentration of HCO-30 in the tank the same concentration as that of the first concentration level.

Test organisms (species):

Oryzias latipes

Details on test organisms:

TEST ORGANISM
- Source: Miyazawa Fish Farm
- Length at study initiation: 9-11 cm
- Weight at study initiation: 21-37 g
- Method of breeding: The fish were bred in Mitsubishi‐Kasei Institute of Safe & Security Science, rearing period 8 weeks.
- Lipid content at test initiation: 5.1% (n=4, 4.8 – 5.2 %)
- Feeding during test
- Food type: TetraMin
- Frequency: Once per day

ACCLIMATION
- Acclimation period: One week at 25 ± 2°C
- Type of food: TetraMin
- Feeding frequency: Once per day
- Health during acclimation (any mortality observed): No death was observed during the acclimation period of one week before the test

Route of exposure:

aqueous

Test type:

flow-through

Water / sediment media type:

natural water: freshwater

Total exposure / uptake duration:

8 wk

Hardness:

Not reported

Test temperature:

25 ± 2°C

pH:

Not reported

Dissolved oxygen:

4.9 – 8.1 ppm

TOC:

Not reported

Salinity:

Not applicable

Conductivity:

Not applicable

Details on test conditions:

TEST SYSTEM
- Test vessel: Glass rearing tank
- Type (delete if not applicable): closed
- Material, size, headspace, fill volume: 85 L glass tank filled to 80L with a stainless steel floating cover
- Aeration: yes

Nominal and measured concentrations:

Nominal

Reference substance (positive control):

no

Conc. / dose:

50 ng/L

Temp.:

25 °C

Type:

BCF

Value:

ca. 748 - ca. 1 248 L/kg

Basis:

whole body w.w.

Conc. / dose:

5 ng/L

Temp.:

25 °C

Type:

BCF

Value:

ca. 665 - ca. 996 L/kg

Basis:

whole body w.w.

Elimination:

yes

Parameter:

DT50

Depuration time (DT):

2 wk

Validity criteria fulfilled:

yes

Conclusions:

The highest bioconcentration factors for first and second concentration level were 1248 and 996, respectively.The bioconcentration factors for first and second concentration level were nearly reached to equilibrium at the time of the two weeks. The depuration test was also performed, and rapid depuration was found, so that a half-life was about 2 days.

Executive summary:

The highest bioconcentration factors for first and second concentration level were 1248 and 996, respectively.The bioconcentration factors for first and second concentration level were nearly reached to equilibrium at the time of the two weeks. The depuration test was also performed, and rapid depuration was found, so that a half-life was about 2 days. The study was conducted to a high level of reliability, with special precautions taken due to the high volatility of the test substance and analytical verification of concentrations in fish and test solutions.

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:

1. SOFTWARE : CATALOGIC 5.14.1

2. MODEL (incl. version number) : BCF base-line model v.04.11

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL : CCCCC(CC)CON(=O)=O

4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
- Defined endpoint: Bioconcentration factor (BCF) - the ratio of the chemical concentration in biota as a result of absorption via the respiratory surface to that in the surrounding water at steady state.
- Unambiguous algorithm: BCF base-line model v.05.12 - November, 2020
- Defined domain of applicability: General properties requirements (log Kow, molecular weight, water solubility), Structural domain (Atom Centered Fragments (ACFs)), Mechanistic domain
- Appropriate measures of goodness-of-fit and robustness and predictivity:
-- External Validation:
--- The BCF base-line model and its major component BCFmax model were subject of external validation:
----- BCFmax model – 123 experimental BCF values for chemicals with insignificant metabolism were kindly provided by ExxonMobil (2005),
----- BCF base-line model – 794 experimental BCF values were used by NITE Japan (2006) to validate the model.
--- Both validations are based on different criteria:
----- BCFmax model – direct comparison of observed and predicted BCF values (in log units) is used,
----- BCF base-line model – dichotomial classification (BCF = 1000 or BCF < 1000) is analyzed.
--- Availability of the external validation sets:
----- BCFmax model – currently implemented in the training set and not available as separate file,
----- BCF base-line model – most of the external BCF values (96%) are proprietary and are not available.
--- Statistics obtained by external validation:
----- BCFmax model:
- Training data: N = 81, RSS = 31, R2 = 0.85,
- External data: N = 123, PRSS = 13, Q2 = 0.80; where PRSS is the RSS calculated by using predicted BCF values for validation set,
- Only one outlier is identified, as a result of incorrectly calculated log KOW (two log units larger than the experimental one is).
----- BCF base-line model – domain is not accounted for:
- Concordance (both BCF = 1000 or BCF < 1000) – 86%,
- Specificity (BCF < 1000) = 87%,
- Sensitivity (BCF = 1000) = 52%.
----- BCF base-line model – domain is accounted for:
- Overall accuracy (both BCF = 1000 or BCF < 1000) – 89%,
- Specificity (BCF < 1000) = 91%,
- Sensitivity (BCF = 1000) = 60%.
----- Statistics for goodness-of-fit:
------ Residual Sum of Squares, RSS = 198
------ Coefficient of correlation, R =0.92
------ Root mean square error, SR = 0.50
----- Correctness of classification:
------ Concordance of dichotomial classification (BCF = 5000 or BCF < 5000): 98%,
------ Sensitivity (BCF = 5000): 84%,
------ Specificity (BCF < 5000): 99%.
- Mechanistic interpretation: Detailed information about mechanistic basis of the model underpinning the prediction is available in model QMRF

5. APPLICABILITY DOMAIN
- Descriptor domain:
--- Log Kow: range = [ -6.34 .. 19.6 ], calculated: 5.24 (In domain)
--- Molecular weight: range = [ 16 .. 1180 ]Da, calculated: 175Da (In domain)
--- Water solubility: range = [ 0 .. 1000000 ]mg/L, calculated: 22.5mg/L (In domain)
- Structural domain:
--- Fragments in correctly predicted training chemicals – 100.00%
--- Fragments in non-correctly predicted training chemicals – 0.00%
--- Fragments not present in the training chemicals – 0.00%
- Mechanistic domain: The expected uptake mechanism of the target chemical is passive diffusion across biological membranes.
- Similarity with analogues in the training set:
--- No analogues with observed BCF data are found in the training set of CATALOGIC BCF model. Structural analogues to the target chemical have been searched in the large database of QSAR Toolbox v.4.4.1 as well as in literature and website sources.Two analogues have been found:
---- Analogue 1
------ Name: 1,2,3-Propanetriol trinitrate
------ CAS RN: 55-63-0
------ BCF data: several data values available ranging from log BCF=0.903 to logBCF=1.18
------ Source: ECOTOX database available in QSAR Toolbox v.4.4.1
---- Analogue 2
------ Name: Amyl nitrate
------ CAS RN: 1002-16-0
------ BCF data: 29 L/kg (log BCF = 1.46)
------ Source: PubChem
- Other considerations (as appropriate): The analogues log BCF data show that nitrate esters are not bioaccumulative.CAS 55-63-0, 1,2,3-Propanetriol trinitrate and CAS 1002-16-0, Amyl-nitrate were use for external validation of the model predictions. BCF base-line model correctly predicts both esters as not bioaccumulative. Both esters have less bioaccumulative potential due their less lipophilicity compared to the target 2-Ethylhexyl nitrate. The BCF values predicted by CATALOGIC BCF base-line model for the found analogues are consistent with their experimental results (variation of experimental error for BCF = ±0.75 log units). The observed and predicted log BCF values for the analogues are in concordance with the prediction for the target chemical (i.e. not bioaccumulative substances).

6. ADEQUACY OF THE RESULT
Bioaccumulation assessment for CAS 27247-96-7, 2-Ethylhexyl nitrate, was undertaken using CATALOGIC BCF base-line model. The QMRF of the model and model description can be found in Supplementary materials. The target chemical is predicted to be not bioaccumulative (log BCF = 3.16) using logKow as a parameter for passive diffusion. The target belongs 100% to model applicability domain. All mitigating factors (size, metabolism, ionization and water solubility) are considered within for the prediction. It was found that the metabolism is the most significant mitigating factor for the BCF prediction. The size is the other factor having an effect, although its impact on the prediction is much lower than metabolism.

The CATALOGIC BCF prediction is consistent with the available observed data for the target chemical: logBCF = 3.10 (BCF of 1248 L/kg from a 1989 study), logBCF = 3.08 (BCF of 1196 L/kg; METI`s data (2019, available in the training set of BCF base-line model).

The BCF prediction for the target chemical is supported by:
a) two structural analogues with experimental BCF data corresponding to not B/vB
b) external QSAR models predictions
c) metabolic similarity assessment between the target and analogues with documented metabolism

Based on the weight-of-evidence and the adequacy of the BCF prediction and metabolism, it can be concluded with a high degree of certainty that the target chemical will not bioaccumulate in living organisms.

Guideline:

other: REACH Guidance on QSARs R.6

Principles of method if other than guideline:

- Software tool(s) used including version: CATALOGIC 5.14.1
- Model(s) used: BCF base-line model v.04.11
- Model description: see field 'Attached justification'
- Justification of QSAR prediction: see field 'Justification for type of information' and 'Attached justification'

Specific details on test material used for the study:

SMILES: CCCCC(CC)CON(=O)=O

Key result

Type:

other: logBCF

Value:

3.16 L/kg

Remarks on result:

other: QSAR predicted value

The CATALOGIC 5.14.1 BCF base-line model v.04.11 predicted that 2 -ethylhexyl nitrate has a log BCF of 3.16 l/kg.

Validity criteria fulfilled:

yes

Conclusions:

Bioaccumulation assessment for CAS 27247-96-7, 2-Ethylhexyl nitrate, was undertaken using CATALOGIC BCF base-line model. The QMRF of the model and model description can be found in Supplementary materials. The target chemical is predicted to be not bioaccumulative (log BCF = 3.16) using logKow as a parameter for passive diffusion. The target belongs 100% to model applicability domain. All mitigating factors (size, metabolism, ionization and water solubility) are considered within for the prediction. It was found that the metabolism is the most significant mitigating factor for the BCF prediction. The size is the other factor having an effect, although its impact on the prediction is much lower than metabolism.

The CATALOGIC BCF prediction is consistent with the available observed data for the target chemical: logBCF = 3.10 (BCF of 1248 L/kg from a 1989 study), logBCF = 3.08 (BCF of 1196 L/kg; METI`s data (2019, available in the training set of BCF base-line model).

The BCF prediction for the target chemical is supported by:
a) two structural analogues with experimental BCF data corresponding to not B/vB
b) external QSAR models predictions
c) metabolic similarity assessment between the target and analogues with documented metabolism

Based on the weight-of-evidence and the adequacy of the BCF prediction and metabolism, it can be concluded with a high degree of certainty that the target chemical will not bioaccumulate in living organisms.

Description of key information

Experimental study

A Bioaccumulation Study in Oryzias latipes was conducted according to "Study method concerning new chemical substances” provided in Kanpogyo No5, Yakuhatsu No.615 and 49 Kiyoku No.392, 1974.

The highest bioconcentration factors for first and second concentration level were 1248 and 996, respectively. The bioconcentration factors for first and second concentration level were nearly reached to equilibrium at the time of the two weeks. The depuration test was also performed, and rapid depuration was found, so that a half-life was about 2 days. The study was conducted to a high level of reliability,with special precautions taken due to the high volatility of the test substance and analytical verificationof concentrations in fish and test solutions.

Catalogic QSAR prediction

Bioaccumulation assessment for CAS 27247-96-7, 2-Ethylhexyl nitrate, was undertaken using CATALOGIC BCF base-line model. The target chemical is predicted to be not bioaccumulative (log BCF = 3.16) using logKow as a parameter for passive diffusion. The target belongs 100% to model applicability domain. All mitigating factors (size, metabolism, ionization and water solubility) are considered within for the prediction. It was found that the metabolism is the most significant mitigating factor for the BCF prediction. The size is the other factor having an effect, although its impact on the prediction is much lower than metabolism.

The CATALOGIC BCF prediction is consistent with the available observed data for the target chemical: logBCF = 3.10 (BCF of 1248 L/kg from a 1989 study), logBCF = 3.08 (BCF of 1196 L/kg; METI`s data (2019, available in the training set of BCF base-line model).

The BCF prediction for the target chemical is supported by:

a) two structural analogues with experimental BCF data corresponding to not B/vB

b) external QSAR models predictions

c) metabolic similarity assessment between the target and analogues with documented metabolism

Based on the weight-of-evidence and the adequacy of the BCF prediction and metabolism, it can be concluded with a high degree of certainty that the target chemical will not bioaccumulate in living organisms.

Key value for chemical safety assessment

BCF (aquatic species):

1 248 L/kg ww