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Environmental fate & pathways

Biodegradation in soil

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Key value for chemical safety assessment

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In accordance with Regulation (EC) No 1907/2006, Annex IX, Section 9.2,, Column 2, soil simulation testing does not need to be conducted as the chemical safety assessment according to Annex I indicates that there is no need to investigate further the degradation of the substance and its degradation products. The risk characterization ratios (RCRs) of the chemical safety assessment are below 1, indicating that the risks are acceptable.

 In addition, the substance does not have a high potential for adsorption to soil. The log Kow is low (log Kow < 3; see IUCLID Ch. 4.7). The estimated adsorption coefficients for the charged and the uncharged molecule is also low (measured and estimated data; see IUCLID Ch. 5.4.1).  Therefore, it is not considered necessary to conduct a soil simulation test and no biodegradation studies in soil will be provided.

The degradation productsof the two constituents (CAS 13897 -55 -7 and 13897 -56 -8) of the substance (EC 939 -489 -9) were predicted using Catalogic v5.13.1.156 301C v11.15. The model predicted in total 133 metabolites for the two constituents 4-methylcyclohexane-1,3-diamine (CAS 13897-55-7: 86 metabolites) and 2-methylcyclohexane-1,3-diamine (CAS 13897-56-8: 47 metabolites). The majority of the substances is assessed to be readily biodegradable (n = 76) based on biological oxygen demand after 28 days (≥ 60% BOD/ThOD). None of the substances has a log Kow > 3, as the maximum log Kow of the substances is 1.27 (range: -6.1 to 1.27). In total 19 metabolites are to be regarded as relevant based on their estimated quantity (≥ 0.1%, approximately 0.001 mol/mol parent as estimated by the model). An overview on the relevant degradation products is shown in the endpoint summary of IUCLID Ch. 5.2.1. The complete list of metabolites is given in the endpoint study records of the model predictions for the two constituents.

Ten of the relevant degradation products are readily biodegradable. The log Kow of these predicted degradation products is clearly below the critical value of 3 (log Kow -5.0 to 1.3). Two of the metabolites are registered under REACH, but are not PBT/vPvB.

Therefore, it can be concluded that none of these degradation products is potentially PBT/vPvB.

In addition, it is expected that the reaction product of 2,4-Dinitrotoluene and 2,6-Dinitrotoluene and hydrogen is not biodegraded through growth linked processes based on the screening tests on biodegradability (IUCLILD Ch. 5.2.1).