Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

Adsorption

Adsorption to solid soil phase cannot be excluded based on estimated data. The log Koc for the uncharged molecule was calculated using both models of the KOCWIN program (EPI Suite v4.11). The MCI method resulted in a log Koc of 3.1, the log Kow method have a log Koc of 1.5 (BASF SE, 2013). Since the identified fragment (Nitrogen-to-Cycloalkane, aliphatic) occurs at a higher number than the training data set of the models, the estimates are less accurate. The pKa of 10.3 indicates that the substance will exist primarily as a cation in the environment. Therefore, a correction for the charged molecule was performed according to Franco & Trapp (2008, 2009, 2010). The pH-corrected log Koc is 4.5 at pH 7.

Experimental data is available for the structurally similar substance 4,4´-Diamino-3,3´,5,5´-tetramethyl-dicyclohexylmethan (CAS 65926 -45 -0). The adsorption coefficient was determined according to OECD 121 (HPLC method; BASF SE, 2013). The log Koc was measured to be 2.6 at pH 7.0 (23 °C) which is representative for the charged molecule. At pH 9 no reliable Koc could be determined as the retention time on the HPLC system was larger than for the reference substances (log Koc > 5.63). As 98% of the European soils have a pH within a range of 5 to 8, the value determined at pH 9 is not relevant for the assessment of the substances environmental fate.

Due to the uncertainty of the estimated data (applicability domain) and the environmental relevance of the Koc determined at pH 7 for the analogue substance 4,4´-Diamino-3,3´,5,5´-tetramethyl-dicyclohexylmethan (CAS 65926 -45 -0), the experimental value of log Koc = 2.6 at pH 7 was used for the environmental risk assessment.

 

Henry’s Law Constant

Regarding the Henry's law constant, DMDC will not evaporate into the atmosphere from the water surface.

 

Environmental distribution

The distribution of DMDC between the environmental compartments was calculated for the uncharged molecule by use of the Mackay LEVEL 1 v3.00 programme. Over time, the uncharged substance will preferentially distribute into the compartment water (94%). However, as the model does not consider the ionic character of the molecule at environmental relevant pH condition (pKa = 10.3), the distribution into water may be underestimated by the model.