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Environmental fate & pathways

Bioaccumulation: aquatic / sediment

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Description of key information

The constituents of this uvcb substance do not meet the criteria for bioaccumulation accoding to REACh. 

Key value for chemical safety assessment

BCF (aquatic species):
1 730 dimensionless

Additional information

The bioaccumulative potential of the substance was assessed in a weight of evidence approach including experimental data, several QSAR estimations and data on the molecular size and log Kow. The substance is an UVCB, therefore 2 probable structures were assessed by QSAR. The single results are summarized in the table below.

Overview on BCF Results

Model/endpoint

Monoalkylated (C9) DPA

Dialkylated (C9C9) DPA

SMILES

CCCC(C)CC(C)(C)c1ccc(Nc2ccccc2)cc1

CCCC(C)CC(C)(C)c1ccc(Nc2ccc(cc2)C(C)(C)CC(C)CCC)cc1

Molecular weight Da

295

422

Episuite 4.11 (KOW v 1.68) logKow

7.6

11.9

Catalogic 5.11.19 (Bioaccumulation baseline model v2.09) BCF L/kg

831.76

7.58

BCFBAF v3.01, (regression-based estimate) BCF L/kg

6890

54.4

BCFBAF v3.01 including biotransformation, lower to upper trophic) BCF L/kg

1118 - 721.6

2.4 - 1.7

Catalogic Diamax average

16.6Å

 

20Å

 

Experimental derived BCF

1730 L/kg

 

 

The BCF base-line model integrated in Catalogic is a sophisticated model which takes into account different mitigating factors, i.e. acids, metabolism, phenols, size and water solubility. The two structures were inside the parametric and the mechanistic domains of the compound with 100% of the fragments of the target chemical being present in correctly predicted training chemicals. The result is regarded as reliable and suitable to be used in a weight of evidence approach together with the in vivo results. With mitigating factors applied the BCF is determined as 8 to 832 for these structures. Size and metabolism are the major mitigating factors for both representative structures.  

 

US EPA’s EPISuite includes the regression-based estimation and the Arnot-Gobas model which takes biotransformation processes into account. Both structures are within the applicability domain except dialkylated (C9C9) DPA, which is within the molecular weight range but outside the log Kow range of both the regression-based estimation and the Arnot-Gobas model. The regression-based model predicted a BCF of > 2000 L/kg for the monoalkylated (C9) DPA. The Arnot-Gobas model predicted BCF value of 722 L/kg for the upper trophic level including biotransformation rate estimates and a BCF of 5810 with biotransformation rates of zero. As the values which are > 2000 are calculated without considering metabolism and biotransformation, these values are regarded as not relevant. However, from the results it can be concluded that the monoalkylated DPA represents the worst case regarding bioaccumulation potential. The EPISuite results were regarded as suitable in the weight of evidence approach.

 

According to ECHA’s Guidance on Information Requirements and Chemical Safety Assessment chapter R.11 – PBT Assessment, compounds with an average maximum diameter of >1.7 nm together with molecular weight of greater than 1100 are unlikely to have a BCF of >2000. Although the two probable structures of the UVCB substance have a molecular weight of only 295 and 422 g/mol the DiamMax-average ranges between 16 and 20 Angstrom. This indicates a limited bioavailability, especially for the dialkylated structure.

Furthermore, the aquatic BCF of a substance is probably lower than 2000 if the calculated logKow is higher than 10. The dialkylated structure has a calculated logKow of > 11.9.

Based on the QSAR data available, the monoalkylated (C9) DPA is better available than the di-substituted DPA and represents a worst case regarding the bioaccumulation potential of these two structures. Experimental data on the C9 monoalkylated DPA (CAS 27177 -41 -9) are available.

This GLP study followed the procedures of the Chemical Substances Control Law of Japan and was performed with Cyprinus carpio as test species. The measured BCF values (42 d) range from 411 to 1730 (whole body w.w.)Mitsubishi Chemical Safety Institute 2000].

In conclusion, using all available data in a weight of evidence approach, the constituents do not fulfil the criteria for bioaccumulative or very accumulative according to REACh Annex XIII (PBT Assessment)

NOTE: Environment Canada has initiated an assessment of the category of alkylated diphenylamines as part of their Chemicals Management Plan (Section 71 Survey deadline in 2012) and this assessment is still ongoing. In December 2016 a draft screenining assessment was published. This draft report is attached in IUCLID section 13.

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. Furthermore according to Article 25 of the same Regulation testing on vertebrate animals shall be undertaken only as a last resort.

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 substance (Q)SAR results were used for adsorption. 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.