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Environmental fate & pathways

Bioaccumulation: aquatic / sediment

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Description of key information

Based on a bioaccumulation study in fish with a closely related structural analogue and QSAR modelling, the BCF value for the test substance is estimated to be 4.1 L/kg ww (geometric mean).

Key value for chemical safety assessment

BCF (aquatic species):
4.1 L/kg ww

Additional information

Bioaccumulation potential has been evaluated in fish for closely related structural analogue, tris(2-ethylhexyl)benzene-1,2,4-tricarboxylate according to OECD test methods. A measured BCF of up to 2.7 suggests the potential for bioconcentration in aquatic organisms is low. However, there are some uncertainties in the experimental data mainly due to testing at concentrations above the water solubility of the substance by the use of solubilising agents which are recognised as having the potential to lead to an underestimation of the BCF.

The test substance was assessed for bioaccumulation potential using recognised QSAR derivation software as follows:

 

BCF model (CAESAR) (version 2.1.11)

BCF model (Meylan) (version 1.0.0)

BCF Read-Across (version 1.0.0)

US EPA On-Line EPI Suite™v4.0 model BCFBAF

 

It is understood that Annex XI, section 1.3 allows adaptation of the standard testing requirements by making use of (Q)SAR only if the following conditions are met:

 

(i) results are derived from a (Q)SAR model whose scientific validity has been established,

(ii) the substance falls within the applicability domain of the (Q)SAR model,

(iii) results are adequate for the purpose of classification and labelling and/or risk assessment, and

(iv) adequate and reliable documentation of the applied method is provided.

 

Within the four models used, the conditions (i) through (iv) are considered to be met for two of the models:

 

•      US EPA On-Line EPI Suite™v4.0 model BCFBAF

•      BCF Read-Across (version 1.0.0)

 

The structures assessed with these models were deemed to mainly fall within the applicability domain of the model, and this is demonstrated within the relevant QPRF’s. The models are recognized, and are referenced within ECHA’s own guidance and/or have relevant QMRF’s which are also detailed. Due to the fact that QSAR is utilised, these were assigned as Klimish 2 level studies.

 

Within the four models used, the conditions (i), (iii) and (iv) are considered to be met for two of the models:

 

•      BCF model (CAESAR) (version 2.1.11)

•      BCF model (Meylan) (version 1.0.0)

 

Within these models, conditions (i) through (iv) were not fulfilled for the following reasons:

- accuracy of prediction for similar molecules found in the training set is not adequate/not optimal

- similar molecules found in the training set have experimental values that slightly disagree with the target compound predicted value

- the maximum error in prediction of similar molecules found in the training set has a high value, considering the experimental variability

- reliability of logP value used by the model is not optimal

- descriptors for this compound have values outside the descriptor range of the compounds of the training set

 

These studies were therefore assigned as Klimisch 3 level studies and the values obtained using these studies were not used to calculate the geometric mean.

 

Overall

 

On the basis of a weight of evidence approach, there is sufficient information available to state that the substance is not bioaccumulative. Whilst it is not possible to provide a definitive BCF value for the substance due to the variation in the results, none of the values determined via QSAR are above the threshold value quoted in the REACH Regulation of 2000 or 5000 which indicates the potential to bioaccumulate. In order to derive a BCF for the purposes of dossier preparation, it is considered appropriate to utilise a geometric mean across the Klimisch 2 studies. The document “Guidance on information requirements and chemical safety assessment Chapter R.10: Characterisation of dose [concentration]-response for environment” states under section“R.10.2.2 Evaluation and interpretation of data” that:

 

Where there is more than one set of data on the same species, (strain if known), endpoint, duration, life stage and testing condition the greatest weight is attached to the most reliable and relevant one. When there is more than one set of data with the same reliability rating, it might be necessary to look into more detail at the study reports to see whether a specific reason could explain the difference. If no explanation can be found and the results are for the same species and endpoints and are not more than one order of magnitude apart, they can be harmonised by a geometric mean.

 

A geometric mean BCF is therefore applied for the purposes of hazard assessment.

 

Endpoint study

BCF (L/kg ww)

Read-across study

2.7

EPIWIN BCFBAF Results [L/kg]

3.16

BCF Read-Across (version 1.0.0) [L/kg]

8

Geometric Mean BCF overall

4.1

 

Whilst this mean result is presented as only a general indication, this supports the overall conclusion that the substance is not considered to be bioaccumulative. The substance is not considered to be “bioaccumulative” or “very bioaccumulative” on the basis of the available data.