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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.

 

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 the reaction mass of N1,N3-bis(3-aminopropyl)-2-methyl-cyclohexane-1,3-diamine and N1,N3-bis(3-aminopropyl)-4-methyl-cyclohexane-1,3-diamine (DAP-MCDA)

(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.

The substance has a log Kow of 0.46 (see IUCLID Ch. 4.7, Read-Across to its representative constituents N1,N3-bis(3-aminopropyl)-4-methyl-cyclohexane-1,3-diamine (BI 858010) and N1,N3-bis(3-aminopropyl)-2-methyl-cyclohexane-1,3-diamine (BI 858015)). Therefore, a study does not need to be conducted.

To assess the adsorption potential of DAP-MCDA no experimental data exist. Therefore, the Koc value was estimated using QSAR models for two representative constituents of DAP-MCDA (N1,N3-bis(3-aminopropyl)-4-methyl-cyclohexane-1,3-diamine (BI 858010) and N1,N3-bis(3-aminopropyl)-2-methyl-cyclohexane-1,3-diamine (BI 858015)). According to the MCI method of the KOCWIN v2.00 module of EPI Suite v4.11, BI 858010 has a Koc of 218.3 L/kg and a log Koc of 2.34. BI 858015 has a Koc of 222.8 L/kg and a log Koc of 2.35 (BASF SE 2019). 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 (log Kow of 0.46 @25°C; KOWWIN v1.68, EPI Suite v4.11, BASF SE 2019). The latter method resulted in a Koc of 2.38 L/kg and a log Koc of 0.38 for both constituents. These estimates are representative for uncharged molecules. The substances were not within the applicability domain of the models.

 

At environmentally relevant conditions, the constituents of DAP-MCDA will be present in their ionised form (pKa = 10.76 for both constituents; SPARC On-Line Calculator, BASF SE 2019). Therefore, the adsorption coefficient was calculated according to Franco & Trapp (2008, 2009, 2010) to correct for the charged molecules 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 at pH 7 is 74 L/kg and the log Koc is 1.87, respectively, for both constituents of DAP-MCDA, N1,N3-bis(3-aminopropyl)-4-methyl-cyclohexane-1,3-diamine (BI 858010) and N1,N3-bis(3-aminopropyl)-2-methyl-cyclohexane-1,3-diamine (BI 858015).

 

It can be concluded that adsorption to the solid soil phase is not expected under environmentally relevant conditions.

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