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Adsorption / desorption

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Reference
Endpoint:
adsorption / desorption
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:
Data estimated by KOCWIN v2.00 (EPIWEB v 4.1) which uses a valid estimation method; Except for the glyceride representative constituent (i.e., tristearin), test substance was found to fall in the applicability domain of this method and results are adequate for the purpose of classification and labeling and/or risk assessment. However, the uncertainty of the prediction for tristearin is low as the estimated data is in line with the expected behaviour of this class of compounds.
Qualifier:
according to guideline
Guideline:
other: REACH guidance on QSARs: Chapter R.6. QSARs and grouping of chemicals
Principles of method if other than guideline:
1. Meylan WPH, Howard and RS Boethling (1992). "Molecular Topology/Fragment Contribution Method for Predicting Soil Sorption Coefficients", Environ. Sci. Technol. 26: 1560-7.
2. Doucette WJ (2000).  Soil and sediment sorption coefficients.  In: Handbook of Property Estimation Methods, Environmental and Health Sciences. R.S. Boethling & D. Mackay (Eds.), Boca Raton, FL: Lewis Publishers (ISBN 1-56670-456-1). 
Type of method:
other: QSAR estimation
Computational methods:
In absence of experimental data, the adsorption coefficient (Koc) of the test substance was determined through KOCWIN v.2.0 program of EPISuite v.4.1.

Assumptions:
- Individual Koc values will be calculated for representative constituents/substances of each class present in the test substance.
- These representative substances each should represent at >10 % of the test substance composition.
- As the test substance is a UVCB the individual or average estimated Koc values for the constituents will be used to represent a range of values for the entire substance.

Therefore, the Koc values were determined for the following individual substances, present at >10%.

SMILES notation was used as the input parameter and the Koc values were estimated using the different methods integrated in each of the model.:

a) Octanoic acid, stearic and oleic acid representing free fatty acids (substance class)
The calculation input will be provided in SMILES notation as
Octanoic acid: O=C(O)CCCCCCC
Stearic acid: O=C(O)CCCCCCCCCCCCCCCCC
Oleic acid: O=C(O)CCCCCCCC=CCCCCCCCC
b) Triglyceride of Octanoic acid, stearic and oleic acid, representing glycerides of fatty acids (substance class)
The calculation input will be provided in SMILES notation as
Trioctanoin: CCCCCCCC(=O)OCC(COC(=O)CCCCCCC)OC(=O)CCCCCCC
Tristearin: O=C(CCCCCCCCCCCCCCCCC)OC(COC(=O)CCCCCCCCCCCCCCCCC)COC(=O)CCCCCCCCCCCCCCCCC
Triolein: O=C(OC(COC(=O)CCCCCCCC=CCCCCCCCC)COC(=O)CCCCCCCC=CCCCCCCCC)CCCCCCCC=CCCCCCCCC




Key result
Phase system:
other: Average estimated Koc for the fatty acids substance class
Type:
other: Average estimated Koc for the fatty acids substance class
Value:
ca. 49.3 - ca. 31 350 L/kg
Remarks on result:
other: Average value estimated using Kow and MCI methods of KOCWIN v.2
Key result
Phase system:
other: Average estimated Koc for glycerides substance class
Type:
other: Average estimated Koc for glycerides substance class
Value:
ca. 1 530 150 - ca. 54 305 000 000 000 L/kg
Remarks on result:
other: Average value estimated using Kow and MCI methods of KOCWIN v.2
Key result
Phase system:
other: Overall average estimated Koc
Type:
other: Overall average estimated Koc
Value:
> 31 350 L/kg
Remarks on result:
other: Average value for ≥90% of the individual constituents of the test substance

Koc estimations using KOCWIN v.2.0 of EPISuite v.4.1

Substance EPISuite
KOCWIN
MCI - based Koc (L/kg)
EPISuite
KOCWIN
Kow - based Koc (L/kg)
Average (L/kg) Koc ranges (L/kg)
C8 fatty acid 2.89E+01 6.96E+01 4.93E+01 4.93E+01-3.14E+04
C18 fatty acid 1.17E+04 5.11E+04 3.14E+04
C18-unsatd. fatty acid (oleic acid) 1.17E+04 2.41E+04 1.79E+04
C8 triglyceride 2.30E+06 7.63E+05 1.53E+06 1.53E+06-5.43E+13
C18 triglyceride  1.00E+10 1.09E+14 5.43E+13
C18-unsatd. Triglyceride (triolein) 1.00E+10 4.75E+13 2.37E+13

For details on results refer to the attached PDF under 'Attached background material'

Validity criteria fulfilled:
not applicable
Conclusions:
Based on the modelling results for ≥90% of the individual constituents of the test substance, the overall Koc of the test substance is considered to approximately exceed 3.14E+04 L/kg.
Executive summary:

The adsorption coefficient (Koc) of the soaps, stocks, vegetable oil, acidulatedwas determined through KOCWIN v.2.0 program of EPISuite v.4.1. As the test substance is a UVCB/mixture of different constituents (i.e. glycerides of fatty acids, fatty acids and unsaponifiable matters (UMs)) the Koc values were determined for representative substances of each class present >10% to represent the lower and upperlimit of the test substance. Hence, the Koc estimations were carried out for octanoic acid, stearic acid and oleic acid representing fatty acids and trioctanoin, tristearin and triolein representing glycerides of fatty acids. SMILES notations were used as the input parameters for the programs/softwares. The average estimations for the individual representative substances from each class range as follows: (1) C8-18 and C18 -unsatd. alkyl chain containing fatty acids: 4.93E+01-3.14E+04 L/kg (2) C8-18 and C18 -unsatd. alkyl chain containing glycerides: 1.53E+06-5.43E+13 L/kg. Except for the tristearin and triolein, all other representative structures were found to fall in the applicability domain of this method and results are adequate for the purpose of classification and labeling and/or risk assessment. However, the uncertainty in the prediction for tristearin and triolein is low as the estimated data is in line with the expected behaviour of this class of compounds. Further, the Koc values from both the methods were averaged to gain more confidence on the prediction. Therefore, based on the modelling results for ≥90% of the individual constituents of the test substance, the overall Koc of the test substance is considered to approximately exceed >3.14E+04 L/kg, which is indicative of high adsorption potential. However, due to its ready biodegradability potential, the substance is not expected to be persistent in the environment (US EPA, 2012).

Description of key information

Based on the modelling results for ≥90% of the individual constituents of the test substance, the overall Koc of the test substance is considered to approximately exceed >3.14E+04 L/kg (US EPA, 2012), which is indicative of high adsorption potential. However, due to its ready biodegradability potential, the substance is not expected to be persistent in the environment. Further, the lower Koc value has been taken forward for risk assessment, since it results in lower PNECsoil and sediment values. Further, the lower Koc value has been taken forward for risk assessment, since it results in lower PNECsoil and sediment values.

Key value for chemical safety assessment

Koc at 20 °C:
31 350

Additional information

According to Annex VIII, Section 9.3.1, Column 2 of the REACH regulation, the study is not required as the substance is readily biodegradable. Nevertheless, this endpoint was estimated in order to determine its impact on the PNECsoil and sediment derivations.

The adsorption coefficient (Koc) of the ‘soaps, stocks, vegetable oil, acidulated' was determined through KOCWIN v.2.0 program of EPISuite v.4.1. As the test substance is a UVCB/mixture of different constituents (i.e. glycerides of fatty acids and fatty acids) the Koc values were determined for representative substances of each class present >10% to represent the lower and upper limit of the test substance. Hence, the Koc estimations were carried out for octanoic acid, stearic acid and oleic acid representing fatty acids and trioctanoin, tristearin and triolein representing glycerides of fatty acids. SMILES notations were used as the input parameters for the programs/softwares. The average estimations for the individual representative substances from each class range as follows: (1) C8-18 and C18 -unsatd. alkyl chain containing fatty acids: 4.93E+01-3.14E+04 L/kg (2) C8-18 and C18 -unsatd. alkyl chain containing glycerides: 1.53E+06-5.43E+13 L/kg. Except for the tristearin and triolein, all other representative structures were found to fall in the applicability domain of this method and results are adequate for the purpose of classification and labeling and/or risk assessment. However, the uncertainty in the prediction for tristearin and triolein is low as the estimated data is in line with the expected behaviour of this class of compounds. Further, the Koc values from both the methods were averaged to gain more confidence on the prediction. Therefore, based on the modelling results for ≥90% of the individual constituents of the test substance, the overall Koc of the test substance is considered to approximately exceed >3.14E+04 L/kg, which is indicative of high adsorption potential (US EPA, 2012). However, due to its ready biodegradability potential, the substance is not expected to be persistent in the environment.

Further, the lower Koc value has been taken forward for risk assessment, since it results in lower PNECsoil and sediment values.

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