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Environmental fate & pathways

Adsorption / desorption

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Reference
Endpoint:
adsorption / desorption, other
Type of information:
(Q)SAR
Adequacy of study:
key study
Study period:
2016
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:
Accepted calculation method
Reference:
Composition 0
Principles of method if other than guideline:
Estimation Program Interface EPI-Suite version 4.1: KOCWIN (v2.00) for the estimation of the organic carbon-normalized sorption coefficient for soil and sediment (Koc).
The Estimation Program Interface was developed by the US Environmental Agency's Office of Pollution Prevention and Toxics, and Syracuse Research Corporation (SRC). © 2000 - 2011 U.S. Environmental Protection Agency for EPI SuiteTM (Published online in January 2011).
GLP compliance:
no
Type of method:
other: Calculation
Test material information:
Composition 1
Specific details on test material used for the study:
SMILES: CC34CCC1C(CCC2=CC(=O)CCC12)C3CCC4(O)C#C (values relate to the pure substance)
Molecular weight: 298.42 g/mol
Key result
Type:
log Koc
Value:
2.2
Remarks on result:
other: calculation (logKow method)
Key result
Type:
Koc
Value:
159.5 L/kg
Remarks on result:
other: calculation (logKow method)
Type:
log Koc
Value:
3.32
Remarks on result:
other: calculation (MCI method)
Type:
Koc
Value:
4 147 L/kg
Remarks on result:
other: calculation (MCI method)

Validity of the model:

1. Defined Endpoint: Organic carbon partition coefficient, given as logarithmic Koc and Koc

2. Unambigous algorithm: The molecule is first classified as a polar substance. Based on structure of the molecule, the following fragment correction was applied: -C-CO-C- (Ketone). The number of times that the fragment occurs in the structure of the substance applied by the program is verified. For estimation of the log Koc according to the log Kow method the log Kow (exp.) of 2.7 was used.

3. Applicable domain:With a molecular weight of 272.39 g/mole the substance is within the range of the training set (32 - 665 g/mole) as well as in the validation set (27 - 991 g/mole). Regarding the structure of androstendione, the fragment descriptors found by the program are complete.

4a. Statistical characteristics (MCI method):N training set without corrections = 69; N training set with correction = 447; N validation set = 158; Correction coefficient of the total training set without corrections r² = 0.967; Correlation coefficient of the total training set with corrections r² = 0.900; Correlation coefficient of the total validation set r² = 0.850.

4b.Statistical characteristics (Kow method):N training set without corrections = 68; N training set with correction = 447; N validation set = 150; Correction coefficient of the total training set without corrections r² = 0.877; Correlation coefficient of the total training set with corrections r² = 0.855; Correlation coefficient of the total validation set r² = 0.778

5. Mechanistic interpretation: Log Koc is estimated based on the likeliness of a substance for sorption to surfaces of soil/sediment particles. The log Koc is a physical inherent property used extensively to describe a chemical's likeliness to adsob to organic carbon.

Adequacy of prediction:

The result for norethisterone falls within the applicability domain described above and the estimation rules applied for the substance appear appropriate. But an individual uncertainty for the investigated substance is available as some fragments occur more often in the structure of the substance than found in any single substance of the training set. But as the latter is only concerning one fragment and the result is in good correlation to the experimentally determined log Kow, the calculated value for the Koc is assumed to display a realistic value for the substance.
Validity criteria fulfilled:
not applicable
Conclusions:
The QSAR determination of the carbon partition coefficient revealed values of 159.5 L/kg (logKow method) and 4147 L/kg (MCI method) for the unaffected molecule of the substance as any decomposition (e.g. hydrolysis) of the substance is not taken into account by the program.
Executive summary:

The organic carbon partition coefficient (Koc) was predicted using the QSAR calculation of the Estimation Program Interface (EPI) Suite v 4.1. The Koc was estimated to be 159.5 L/kg (logKow method), and 4147 L/kg (MCI method). The results relate to the unaffected molecule of the substance as any decomposition (e.g. hydrolysis) of the substance is not taken into account by the program.

Description of key information

The QSAR determination of the carbon partition coefficient revealed values of 159.5 L/kg (logKow method) and 4147 L/kg (MCI method) for the unaffected molecule of the substance as any decomposition (e.g. hydrolysis) of the substance is not taken into account by the program.

Key value for chemical safety assessment

Koc at 20 °C:
159.5

Additional information

[LogKoc: 2.2]