Willow, Salix alba, ext.

Adsorption / desorption

Link to relevant study record(s)

Reference

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 has a low octanol water partition coefficient and the adsorption potential of this substance is related to this parameter

the study does not need to be conducted because the substance and its relevant degradation products decompose rapidly

Description of key information

The UVCB registration substance has uniformly a very low experimentally determined log Pow (< 0.3; extrapolated log-value: -2.2; OECD 117), without any fraction of higher log Pow. Adsorption is related to this parameter and can thus be concluded to be very low.

Further, the reliable and valid test on ready biodegradability allows to conclude on a rapid and thorough mineralisation of the substance. As such, decomposition to CO2 will be rapid.

Accordingly, in agreement with the provisions of "column 2" in Annex VIII of REGULATION (EC) No 1907/2006 no study on adsorption/desorption screening needs to be performed for this substance. The substance must be considered to be of a very low adsorption potential for sludge, sediment, or soil. Due to its rapid mineralisation there will be no potential for long-term accumulation in sediment or soils.

Key value for chemical safety assessment

Koc at 20 °C:

1.985

Additional information

To derive a scientifically valid key value for chemical safety assessment, Koc was estimated based on log Kow:

For an UVCB, no QSAR based on molecular structure can be applied. The submission substance is known to consist of diverse structures including phenolic compounds.                                                 

The equation according to Gerstl (1990) showed a good correlation with log Kow for a large diverse data set (n=419; r^2=0,831; s not given).                                                   

The model was reviewed by Dearden et al. (2013), concluding compliance with OECD principles 1,2,4E, meaning that

1) the endpoint is defined;

2) the model is based on an unambiguous algorithm;

4E) Appropriate measures of goodness-of-fit, robustness and predictivity are available with regard to external validation.                                                 

The equation is based on a large diverse organic chemical dataset, including organic acids and phenols, and thus applicable to the UVCB submission substance.                                                 

Equation by Gerstl (1990):

log Koc = 0.679*log Kow + 0.094

Based on a log Kow of <0.3 (input used: 0.3), a Koc of 1.985 L/kg is resulting and used for chemical safety assessment.

References:                                                                                           

Gerstl, Z. (1990)

Estimation of organic chemical sorption by soils.

Journal of Contaminant Hydrology, 6, 357-375

Dearden, J.C.; Rotureau, P.; Fayet, G. (2013)

QSPR prediction of physico-chemical properties for REACH.

SAR and QSAR in Environmental Research, 24, 279-318