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Environmental fate & pathways

Bioaccumulation: aquatic / sediment

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Description of key information

Accumulation in organisms is possible.

Key value for chemical safety assessment

Additional information

Quantities of non-intermediate uses are below 100 t/yr. Hence, additional standard information requirements according to Annex IX and Annex X are not to be fulfilled.

However, data will be provided in order to discuss the bioaccumulation potential within the PBT assessment.

 

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 (CAS 106-20-7) (Q)SAR results were used for aquatic bioaccumulation. 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, and for reasons of animal welfare, further experimental studies on aquatic bioaccumulation are not provided.

 

Results and assessment of bioaccumulation

The log Kow of the substance was measured to be 7.3 at 25 °C and pH 7.5 (Oxea AN-ASB 0496, 2010), indicating a potential for bioaccumulation. 

 

Experimental data on bioaccumulation are not available for di-(2-ethylhexyl)amine (CAS 106-20-7). However, in order to assess the bioaccumulation potential of the substance, the BCF was calculated with several estimation models. The table below lists the applied (Q)SAR models, the estimated BCF values and basic information on the applicability domain (AD). Detailed information on the model’s results and the AD are given in the endpoint study records of IUCLID Chapter 5.3.1. The selected models comply with the OECD principles for (Q)SAR models.

 

Summary of relevant information on aquatic bioaccumulation of the substance: Predicted BCF values for applied QSAR models sorted in ascending order by BCF (AD = Applicability Domain)

Model

BCF [L/kg]

In AD

Restraints

US EPA T.E.S.T. v4.2.1: Bioaccumulation: Consensus method

66.5

yes

The substance is within the model’s applicability domain;

but based on the mean absolute errors of the Consensus model, the confidence in the predicted results is low.

BCF base-line model v04.11 (OASIS Catalogic v5.14.1.5):

incl. mitigating factors

562

yes

Mainly metabolism and molecular size are the effective mitigating factors for the Substance.

BCFBAF v3.01 (EPI Suite v4.11): Meylan et al. (1997/1999)

2402

yes

BCF based on log Kow using a correction factor for alkyl chains.

BCF base-line model v04.11 (OASIS Catalogic v5.14.1.5):

not considering mitigating factors

22131

yes

BCF calculated without considering any mitigating factors.

 

The Substance is within the applicability domain of the US EPA T.E.S.T. bioaccumulation model v4.2.1. Nevertheless, the BCF value estimated by the model should be used with caution as the confidence in the result is low based on the mean absolute error. However, it should be kept in mind that the BCF is low (BCF = 66.5 L/kg; BASF SE, 2019).

The BCF calculated by the BCFBAF v3.01 model is above the critical value of 2000 for B/vB substances. However, this model is based on the log Kow and does not consider mitigating factors which affect the bioaccumulation potential.

In contrast, the BCF base-line model v04.11 (OASIS Catalogic v5.14.1.5) takes several mitigating factors into consideration in the calculation of the bioaccumulation potential. The model calculated a BCF of 562 L/kg when considering mitigating factors like metabolism, molecular size and water solubility. Metabolism had the highest mitigating effect on the bioaccumulation potential, followed by molecular size and, to a minor extent, water solubility. According to the OECD 305 technical guidance document, the degree of transformation of the parent is decisive for the effect of metabolism (i.e. the reproduction of subsequent steps is less critical for the prediction of the BCF). The BCF base-line model identified aliphatic N-oxidation as the relevant phase I reaction for the substance. Further identified transformations are aliphatic C-hydroxylation, N-dealkylation, and omega oxidation. Without these mitigating factors, a BCF of 22131 was calculated. However, this value is not relevant for the assessment of the bioaccumulation potential as the relevant mitigating factors were not considered. This maximum BCF is a theoretical bioconcentration factor for a given log Kow value assuming that the only driving force of bioconcentration is lipophilicity and the effect of any other factors is insignificant.

Molecular size and water solubility are discussed within the literature whether certain threshold values are suitable as cut-off criteria for indication of limited bioaccumulation. Regarding molecular size, the PBT working group on hazardous substances discussed a maximum diameter of > 17.4 Å (Comber et al., 2006). The average diameter of the molecules is slightly lower, but the maximum diameter exceeds this critical value (19.0 Å); therefore, the bioaccumulation potential of the Substance is reduced as the molecules would pass less easily through cell membranes.

 

Conclusion

Summing up the available estimated data on the bioaccumulation potential of di-(2-ethylhexyl)amine (CAS 106-20-7), it can be concluded that accumulation in organisms is possible. However, taking into consideration mitigation factors like metabolism by organisms and the molecular size of the substance that additionally reduce the BCF, the substance does not fulfill the B criterion in the PBT assessment as the relevant BCF is < 2000 L/kg (see IUCLID Ch. 2.3).