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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 column 2 of REACH Annexes VIII and IX, 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.

 

In addition the Koc value was estimated using QSAR models. According to the MCI method of the KOCWIN v2.00 module of EPI Suite v4.11, diethanolamine has a Koc of 1.0. The MCI module is more reliable than the second method of KOCWIN v2.00, which estimates the KOC based on the log Kow (not reliable due to applicability domain of the model). The latter method resulted in a Koc of 0.05. These estimates are representative for uncharged molecules. However, the substance is outside the applicability domain of both models as the number of occurrence of one fragment was exceeded (2 instead of 1). In case of the Kow method, the log Kow was also slightly outside of the range of the training set. Therefore, the Koc estimates may be less accurate.

At environmentally relevant conditions, diethanolamine will be present in ionised form (pKa = 8.99; BASF AG, 1991). Therefore the adsorption coefficient was calculated according to Franco & Trapp (2008, 2009, 2010) to correct for the charged molecule at pH 5, 7, and 8. This pH range is representative for 98% of the European soils. The value at pH 7 will be used as key value, i.e. for PEC and PNEC calculations. The resulting Koc at pH 5 to pH 8 is 10 L/kg. The model is not yet validated; in addition, the applicability domain is not clearly defined. Nevertheless, the Koc values of the Franco & Trapp method give a good indication on the adsorption potential of a substance depending on the pH conditions of soil. The method is based on the dissociation constant pKa and the log Kow for the uncharged moelcule.

 

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