Propanoic acid, 2-hydroxy-, (1R,2S,5R)-5-methyl-2-(1-methylethyl)cyclohexyl ester, (2S)-

Adsorption / desorption

Description of key information

The log Koc value was predicted by using three valid QSPR methods. The log Koc = 3.05 indicates that the substance has low mobility in soil and sediment according to the classification scheme of McCall et al. (1981).

Key value for chemical safety assessment

Koc at 20 °C:

1 122

Additional information

Discussion of results

As no single computational model could be identified which would fit completely to this task, the Koc of menthyl lactate eventually was being calculated from the geometric mean of the data generated by three individual QSPR approaches.The QSPR computations were based on the experimentally derived log Kow of the test item of 3.71.

Method	Log KOC
Gerstl method	3.182
Sabljic and Güsten (esters)	2.868
Sabljic and Güsten (mainly hydrophobic)	3.105
Geometric mean	3.05

The resulting geometric mean of log Koc = 3.05 (Koc = 1122 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 = 3.05 in the chemical safety assessment.

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

Waiving of further adsorption/desorption studies

It is being proposed to waive further studies on adsorption/desorption, as is basically would be requested by REACH Annex IX. According to ECHA guidance documents a strong justification needs to be provided for avoiding experimental confirmation of the computed Koc data, as basically being requested by REACH Annex IX. The justification arguments for supporting the robustness of this QSPR-derived Koc result reads as follows: 1. For final computation three individual Koc values were being used which were all based on the log Kow of menthyl lactate; the relatively high log Kow of menthyl lactate of 3.71 is considered to have significant impact on Koc computation. 2. The Koc computations of the three methods all are based on real physical properties 3. The three individual Koc data points represent a coherent data set without outliers 4. The log Koc of menthyl lactate resulting from the geometric mean of these three values therefore is being supported by three different QSPR models Furthermore, concerning data interpretation of the resulting Koc of menthyl lactate, the predicted adsorption coefficients uniformly are pointing in one direction and clearly indicate that the substance has to be considered as having low mobility in sediments and soil. For these reasons additional adsorption/desorption testing cannot be expected to reveal new results with any added value concerning the risk assessment of this substance, thus additional Annex IX studies on adsorption/desorption shall be waived.

[LogKoc: 3.05]