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Environmental fate & pathways

Adsorption / desorption

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Description of key information

Based on a pH corrected Koc calculated for the charged molecule, adsorption to the solid soil phase is to be expected.

However, the chemical has been demonstrated to decompose rapidly in water and soil (see IUCLID chapter 5.2).

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.

 

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 TEA (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.

Assessment

According to Regulation (EC) No 1907/2006, Annex VIII, Section 9.3.1, Column 2, the study on adsorption/desorption screening 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), or the substance and its relevant degradation products decompose rapidly.  TEA has a low log Kow of -2.3 at pH 7.1 (measured; BASF AG, 1991, report no. 90P03095.03). The substance is also readily biodegradable (see IUCLID Ch. 5.2.1). Therefore, a study does not need to be conducted.

In order to assess the adsorption potential of the substance, the Koc value was estimated using QSAR models. According to the MCI method of the KOCWIN v2.00 module of EPI Suite v4.11, TEA has a Koc of 10. The MCI module is more reliable than the log Kow method of KOCWIN v2.00, which estimates the KOC based on the n-octanol/water partition coefficient (measured log Kow: 1.34; uncharged molecule at pH 9.5; BASF AG, 1991; report no: 90P03095.03). The latter method resulted in a Koc of 6. These estimates are representative for uncharged molecules; the substance is not within the applicability domain of the estimation models.

 

At environmentally relevant conditions, TEA will be present in ionised form (pKa = 7.86; measured at 25 °C; BASF AG, 1991; report no.: 90P03095). 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 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 molecule.

The resulting Koc values range from 4489 (at pH 5) to 1979 L/Kg (pH 8).

 

It can be concluded that adsorption to the solid soil phase is to be expected.