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Environmental fate & pathways

Adsorption / desorption

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Description of key information

Adsorption to solid soil phase is not expected.

Key value for chemical safety assessment

Additional information

QSAR-disclaimer


In Article 13 of Regulation (EC) No 1907/2006, it is laid down that information on intrinsic properties of substances may be generated by means other than tests, provided that the conditions set out in Annex XI (of the same Regulation) are met. Furthermore according to Article 25 of the same Regulation testing on vertebrate animals shall be undertaken only as a last resort.


According to Annex XI of Regulation (EC) No 1907/2006 (Q)SAR results can be used if (1) the scientific validity of the (Q)SAR model has been established, (2) the substance falls within the applicability domain of the (Q)SAR model, (3) the results are adequate for the purpose of classification and labeling and/or risk assessment and (4) adequate and reliable documentation of the applied method is provided.


For the assessment of diethanolamine (Q)SAR results were used for the estimation of the adsorption potential. The criteria listed in Annex XI of Regulation (EC) No 1907/2006 are considered to be adequately fulfilled and therefore the endpoint(s) sufficiently covered and suitable for risk assessment. 


Therefore, further experimental studies on the adsorption potential are not provided.


 


In accordance with Regulation (EC) 1907/2006, Annex VIII, Section 9.3.1., Colum 2 and Annex IX, Section 9.3.3., Colum 2, the study does not need to be conducted if based on the physicochemical properties the substance can be expected to have a low potential for adsorption (e.g. the substance has a low octanol water partition coefficient, log Kow), or the substance and its relevant degradation products decompose rapidly. Diethanolamine (CAS 111-42-2) has a log Kow of -2.46 (@ 25 °C, pH 6.8 -7.3, Sasol, 2009) and is readily biodegradable.


 


Assessment


However, in order to assess the adsorption potential of the substance, the Koc value was estimated using a (Q)SAR model.


At environmentally relevant conditions, diethanolamine (CAS 111-42-2) will be present in ionised form (pKa = 8.99; BASF AG, 1991). Cations generally adsorb stronger to soils containing organic carbon and clay than their neutral counterparts. Franco & Trapp (2008, 2009, 2010) have developed a method to take this effect into consideration when assessing the adsorption potential. The method is based on the dissociation constant pKa and the log Kow for the uncharged molecule.


Regarding the charged molecule at pH 7 the log Koc was estimated to be 0.99 (Koc = 10 L/kg) following the method of Franco & Trapp, 2008, 2009, 2010 (BASF, 2021) and using the estimated pKa of 8.99 (BASF AG, 1991; see IUCLID Ch. 4.21) and the calculated log Kow for the uncharged molecule of -2.46 (measured; Sasol, 2009). The substance is slightly out of the applicability domain (AD), since the measured log Kow of diethanolamine is -2.46 (SASOL, 2009) and limits for the AD for bases are: -1.66 < log Kow < 7.03. However, since the low log Kow does not point to any adsorption potential of the substance, the deviation from the AD seems of low relevance. Regarding pKa the substance is within the AD. The correction was performed for pH 5, 7, and 8, which represents 98% of the European soils. The value at pH 7 will be used as key value, i.e. for PEC and PNEC calculations.


 


It can be concluded that adsorption to the solid soil phase is not to be expected.