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Endpoint:
adsorption / desorption: screening
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
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.
Justification for type of information:
1. SOFTWARE
KOCWIN and equations based on the correlation of Kow and Koc.

2. MODEL (incl. version number
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).

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
CC(C)CCOC(=O)C=Cc1ccc(OC)cc1 and measured log Kow of 4.78.

4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
See attached QMRF

5. APPLICABILITY DOMAIN
See attached QPRF

6. ADEQUACY OF THE RESULT
See attached QPRF
Reference:
Composition 1
Composition 2
Composition 3
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 material information:
Composition 1
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).
Type:
Koc
Value:
4 340
Temp.:
20 °C
Remarks on result:
other: Geometric mean of Koc values determined with four approaches
Type:
log Koc
Value:
3.64
Temp.:
20 °C
Remarks on result:
other: Geometric mean of Koc values determined with four approaches
Type:
log Koc
Value:
3.11
Temp.:
20 °C
Remarks on result:
other: PCKOCWIN MCI
Type:
log Koc
Value:
3.56
Temp.:
20 °C
Remarks on result:
other: PCKOCWIN log KOW
Type:
log Koc
Value:
3.91
Temp.:
20 °C
Remarks on result:
other: Gerstl method
Type:
log Koc
Value:
3.97
Temp.:
20 °C
Remarks on result:
other: Sabljic et al. (mainly hydrophobic substances)

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 ) ......................... : 4.78

Non-Corrected Log Koc (0.55313 logKow + 0.9251) .... : 3.5691

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 .................................. : 3.5594

Estimated Koc: 3626 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 · 4.78 + 0.663

The result is: log KOC = 3.91

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 · 4.78 + 0.10

The result is: log KOC = 3.97

Validity criteria fulfilled:
not applicable
Conclusions:
The QSPR-estimated adsorption coefficient of the substance is Koc = 4340 L/kg (log Koc = 3.64). 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 four 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). The approaches gave a coherent set of four data points for the log Koc value. The geometric mean log Koc value calculated from these five data points was 3.64. It is proposed to use this value further in the chemical safety assessment.

According to the testing strategy as shown in ECHA "Guidance on information requirements and chemical safety assessment - Chapter R.7a: Endpoint specific guidance", if the QSPR result is considered as reliable, but tonnage supply is > 100 tpa, then the QSPR-derived value shall be used for CSA. This QSPR is considered reliable as it is supported from several, different QSPR models, which mostly are based on real phys.-chem. properties of the test item (i.e. robustness of the approach can be assumed).

Finally, based on the classification of soil mobility potential as given in McCall et al.1981, with a Koc within the range 2000 -5000 substance is to be classified as having "slight mobility" 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

The log Koc value was predicted with the program KOCWIN and with two QSPR methods. The log Koc = 3.64 indicates that the substance is slightly mobile in soil and sediment according to the classification scheme of McCall et al. (1981).

Key value for chemical safety assessment

Koc at 20 °C:
4 340
Log Koc at 20 °C:
3.64

Additional information

Discussion of results

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 data generated by four individual QSPR approaches.The four different ways of QSPR computations mostly were based on the experimentally derived log Kow of the test item of 4.78.

Method

Log KOC

PCKOCWIN MCI

3.11

PCKOCWIN log KOW

3.56

Gerstl method

3.91

Sabljic and Güsten (mainly hydrophobic)

3.97

Geometric mean

3.64

The resulting geometric mean of log Koc = 3.64 (Koc = 4340 L/kg) is considered as valid as it is being supported by several different QSPR approaches.It is proposed to use the predicted value for the adsorption coefficient of log Koc = 3.64 in the chemical safety assessment.

The substance is considered to have "slight mobility" in sediments and soil (McCall 1981).

Waiving of further adsorption/desorption studies

As the substance is readily biodegradable fulfilling the 10-day window, further testing of adsorption/desorption of the substance is not necessary according to Regulation (EC) No 1907/2006, Annex VIII, column 2.