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Environmental fate & pathways

Adsorption / desorption

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Description of key information

Due to the calculated Koc for the uncharged and the charged molecule, adsorption to the solid soil phase (e.g. clay) is not expected. Furthermore, the chemical is readily biodegradable.

Key value for chemical safety assessment

Additional information

The adsorption potential was estimated for Triethanolamine (TEA; CAS 102 -71 -6) using the MCI and the Kow methods of the KOCWIN v2.00 module from SRC EPI Suite v4.10. The MCI method is regarded as more reliable compared to the log Kow method. Both model results are representative for the uncharged molecule. As the correction factor for "aliphatic alcohol" has a maximum occurrence of 2 while it is found twice in TEA, the substance is not within the applicability domain of both models. In addition, the log Kow of TEA (-2.3, see IUCLID Ch. 4.7) is slightly below the lower limit of the training dataset (-2.11), which also reduces the accuracy of the estimation. Nevertheless, the deviations from the estimation domain is in both cases rather marginal; therefore, the results can be used in a weight of evidence approach for the uncharged molecule.

TEA ionises in aqueous solutions based on a pKa of 7.91 (SPARC v4.6). TEA will partly exist as a cation in the environment. Cations generally adsorb more strongly to the soils organic carbon and clay than the substance's neutral counterparts. Therefore, the adsorption coefficient was calculated according to Franco & Trapp (2008, 2009, 2010) to correct for the charged molecule at pH 5 to 8. The pH range was selected since this range represents 98% of the European soils. The Koc values are listed below.

 

Uncharged molecule:

- MCI method: Koc = 10; log Koc = 1

- Kow method: Koc = 0.058; log Koc = -1.24

Charged molecule:

- Franco & Trapp, 2008:

pH 5: Koc = 18; log Koc = 1.27

pH 7: Koc = 17; log Koc = 1.23

pH 8: Koc = 12; log Koc = 1.06

Based on the corrections for the charged molecule according to Franco & Trapp (2008, 2009, 2010), adsorption to the solid soil phase is not expected.

In a study conducted by West in 1996 it was demonstrated, that TEA rapidly degrades according to the definition as laid down in the

Guidance on the application of CLP criteria (Guidance to regulation (EC) No 1272/2008 on classification, labelling and packaging (CLP) of substances and mixtures), further it also rapidly degrades in soil with a half-life of 1.8 days. Additionaly, in a ready test performed by Gerike (1978) according to a precursor of the Modified OECD Screeening Test (OECD TG 301 E) the substance turned out to be readily biodegradable.

According to the REACH legislation Annex VIII 9.3.1 a study on the adsorption/desorption does not need to be conducted if the substance and its relevant degradation products decompose rapidly. Therefore, a screening test on the adsorption of TEA is not required.