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Environmental fate & pathways

Adsorption / desorption

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Endpoint:
adsorption / desorption: screening
Type of information:
(Q)SAR
Adequacy of study:
supporting 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
Remarks:
The (Q)SAR is an accepted calculation method, therefore generally being considered as reliable study with restrictions. As this approach is taken from (1) ECHA's Guidance on information requirements and chemical safety assessment - Chapter R.7a: Endpoint specific guidance, and from (2) "European Chemical Bureau Technical Guidance Document on Risk Assessment Part III", the computation method is considered a valid.
Guideline:
other: REACH guidance on QSARs R.6, May/July 2008
Principles of method if other than guideline:
The adsorption coefficient of the substance was estimated using different QSPR estimation methods.
GLP compliance:
no
Type of method:
other: QSPR estimation
Media:
other: QSPR estimation
Test temperature:
Computation referring to a temperature of 20 °C.
Computational methods:
- Adsorption coefficient per organic carbon (Koc):
The adsorption coefficient of the substance was estimated with the KOCWIN modelling program (version 2) by using the first-order Molecular Connectivity Index (MCI) and by using the octanol-water partition coefficient (log Kow). Additionally, different equations based on a correlation of the Koc and Kow values were applied (Gerstl 1990, Sabljic et al. 1995). Furthermore the Koc was calculated using EUSES 2.1.2 (Chemical class for Koc-QSAR: Ester).
Type:
Koc
Value:
4 496
Temp.:
20 °C
Remarks on result:
other: Geometric mean of Koc values determined with five approaches
Type:
log Koc
Value:
3.653
Temp.:
20 °C
Remarks on result:
other: Geometric mean of Koc values determined with five approaches
Type:
log Koc
Value:
3.11
Temp.:
20 °C
Remarks on result:
other: PCKOCWIN MCI
Type:
log Koc
Value:
3.65
Temp.:
20 °C
Remarks on result:
other: PCKOCWIN log KOW
Type:
log Koc
Value:
4.02
Temp.:
20 °C
Remarks on result:
other: Gerstl method
Type:
log Koc
Value:
4.11
Temp.:
20 °C
Remarks on result:
other: Sabljic et al. (mainly hydrophobic substances)
Type:
log Koc
Value:
3.47
Temp.:
20 °C
Remarks on result:
other: EUSES 2.1.2 (Chemical class for Koc-QSAR: Esters)

SMILES : CC(C)CCOC(=O)C=Cc1ccc(OC)cc1

CHEM : 2-Propenoic acid, 3-(4-methoxyphenyl)-, 3-methylbutyl ester

MOL FOR: C15 H20 O3

MOL WT : 248.32

--------------------------- KOCWIN v2.00 Results ---------------------------

Koc Estimate from MCI:

---------------------

First Order Molecular Connectivity Index ........... : 8.613

Non-Corrected Log Koc (0.5213 MCI + 0.60) .......... : 5.0900

Fragment Correction(s):

1 Ether, aromatic (-C-O-C-) ........... : -0.6791

1 Ester (-C-CO-O-C-) or (HCO-O-C) ...... : -1.2970

Corrected Log Koc .................................. : 3.1139

Estimated Koc: 1300 L/kg <===========

Koc Estimate from Log Kow:

-------------------------

Log Kow (User entered ) ......................... : 4.95

Non-Corrected Log Koc (0.55313 logKow + 0.9251) .... : 3.6631

Fragment Correction(s):

1 Ether, aromatic (-C-O-C-) ........... : 0.0559

1 Ester (-C-CO-O-C-) or (HCO-O-C) ...... : -0.0656

Corrected Log Koc .................................. : 3.6534

Estimated Koc: 4502 L/kg <===========

Equation from Gerstl (1990): log KOC = 0.679 · log KOW + 0.663 (n = 419, r2 = 0.831)

Computation for test substance: log KOC = 0.679 · 4.95 + 0.663

The result is: log KOC = 4.02

Equation from Sabljic et al.(1995), mainly hydrophobic substances: log KOC = 0.81 · log KOW + 0.10 (n = 81, r2 = 0.89)

Computation for test substance: log KOC = 0.81 · 4.95 + 0.10

The result is: log KOC = 4.11

Validity criteria fulfilled:
not applicable
Conclusions:
The QSPR-estimated adsorption coefficient of the substance is Koc = 4496 L/kg (log Koc = 3.65). It is proposed to use this value further in the chemical safety assessment. The substance has a "slight mobility" in soil (acc. to McCall et al. 1981).
Executive summary:

The purpose of this study was to determine the Koc of test item by the use of non experimental methods. As no single computational model could be identified which would fit completely to this task, the Koc was calculated from the geometric mean of the results generated by five individual QSPR approaches.

The adsorption coefficient of the substance was estimated with the KOCWIN program using the Molecular Connectivity Index and the octanol-water partition coefficient of the substance. Further, two equations were used for the computation of the adsorption coefficient that were derived from the regression of experimental log Koc and log Kow values (Gerstl 1990, Sabljicet al. 1995) and the EUSES 2.1.2 QSAR calculation (chemical class: Esters). The approaches gave a coherent set of five data points for the log Koc value. The geometric mean log Koc value calculated from these five data points was 3.65 (Koc = 4496). It is proposed to use this value further in the chemical safety assessment.

Finally, based on the classification of soil mobility potential as given in McCall et al.1981, with a Koc 2000 - 5000 the substance is to be classified as slightly mobile in soil (McCall P.J., Laskowski D.A., Swann R.L., and Dishburger H.J., (1981), “Measurement of sorption coefficients of organic chemicals and their use, in environmental fate analysis”, in Test Protocols for Environmental Fate and Movement of Toxicants. Proceedings of AOAC Symposium, AOAC, Washington DC).

Endpoint:
adsorption / desorption: screening
Data waiving:
study scientifically not necessary / other information available
Justification for data waiving:
the study does not need to be conducted because the substance and its relevant degradation products decompose rapidly

Description of key information

As the substance and its relevant degradation products decompose rapidly testing of adsorption/desorption of the substance is not necessary according to Regulation (EC) No 1907/2006, Annex VIII, column 2.

The log Koc value was predicted with the program KOCWIN and with two QSPR methods and EUSES 2.1.2. The mean Koc of 4496 indicates that the substance is slightly mobile in soil and sediment according to the classification scheme of McCall et al. (1981). This value was used for PNEC sediment and soil derivation and exposure calculations.

Key value for chemical safety assessment

Koc at 20 °C:
4 496

Additional information